STUDIES ON PESTICIDES RESIDUES ANALYSIS
61
STUDIES ON PESTICIDES RESIDUES ANALYSIS DISSERTATION SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE AWARD OF THE DEGREE OF ^ast^r of ^I(tl0S0p^g IN APPLIED CHEMISTRY By GAIVEN VARSHNEY DEPARTMENT OF APPLIED CHEMISTRY Z.H. COLLEQE OF ENGINEERING AND TECHNOLOGY ALIGARH MUSLIM UNIVERSITY ALIGARH (INDIA) 2005
Transcript of STUDIES ON PESTICIDES RESIDUES ANALYSIS
STUDIES ON PESTICIDES RESIDUES ANALYSIS
DISSERTATION SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS
FOR THE AWARD OF THE DEGREE OF
^ a s t ^ r of ^I(tl0S0p^g
IN
APPLIED CHEMISTRY
By
GAIVEN VARSHNEY
DEPARTMENT OF APPLIED CHEMISTRY Z.H. COLLEQE OF ENGINEERING AND TECHNOLOGY
ALIGARH MUSLIM UNIVERSITY ALIGARH (INDIA)
2005
Fed in CoinputBK
. i
( Voc. N )
2 8 J U L 2035
V
DS3496 1i
V-
Dedicated to
My parents
? rOff. ; 0571-2700920-23 Ext. 3000 IRes i . ; 0571-2741580
Email; [email protected]
DEPARTMENT OF APPLIED CHEMISTRY
OXE,
M.Sc, M.Phil., Ph.D.
Professor & Chairman
FACULTY OF ENGINEERING & TECHNOLOGY ALIGARH MUSLIM UNIVERSITY
ALIGARH - 202 002 (INDIA)
CERTIFICATE
This is to certify that the dissertation entitled "Studies on
Pesticides Residues Analysis" submitted for the award of the degree
of Philosophy in Applied Chemistry, is a faithful record of the
bonafide research vvork carried out at the Department of Applied
Chemistry, ,Zakir Hussain College of Engineering and Technology,
Aligarh Muslim Uni^'ersity, Aligarh by Ms. Gaiven Varshney under
my guidance and supervision .
(Prof. H.S. Rathore)
Chairman
ACKNOWLEDGEMENTS
S/feefyreaJp/easure io express lay ofeep sense ofrespec/ <uic/Sincem
^ra/i/ucfe h J^rof. J{.S. 'iRai£ore^ Chairman, ^eparimeni of
C^ppnecf Gnemjs/ry, /j. y/. Gof/e^e of &nqineerin^ ancfZIec£nofoqu^
C^fiqarn Muslim Q^niuersiio^ C^fiqar£^ ancfer cunose efficienf
qviJance anJ supervision^ inis wor£ nas oeen compieiea. J~fis
encouraqemeni ancf aiieniion at eueru siaqe of mq research career
prouidecfme spirit io complete this stuoq.
y am tnan£fuf to mu faSoraiorq Goifeaqaes^ friends for tneir
cooperation ancf timelq nelp. Special mention must oe made of mq
respected parents for prouidinq me constant encouraqement and
moral support^ wnien smootnens mq path during mu
L V ^
GAIVEN VARSHNEY
CONTENTS
I. General Introduction Page No.
A. Pesticides 1 B. Classification of Pesticides 2
1. Inorganic Pesticides 2 2. Organic Pesticides 2 3. Organic Pesticides Containing Metal Ions 3
C. Dithiocarbamate Pesticides 3 1. General Chemistry and Classification 9 2. Mode of Action 12 3. Other Applications of Dithiocarbamates 15 4. Carbamates Residues Analysis 18
D. Work Done 24 E. References 30
II. A New Spot Test For The Detection Of Dithiocarbamate Fu igicides In Soil And Water
A. Introduction 33 B. Experimental 34 C. Results and Discussion 37 D. Conclusion 40 E. References 52
A. PESTICIDES
The term pesticide is derived from Latin word cida means
"to kill". It is defined'"'^ as any substance, preparation or organism used
to protect plants or wood or other plants products from harmfril
organisms; to regulate the growth of plants; to give protection against the
harmfril creatures or to render such creatures harmless. Thus the term
pesticide embraces large group of class which includes avicides,
cheniosterilants, defolints, ftmgicides, growth regulators, herbicides,
insecticides, nematicides, piscicides , repellants, rodenticides, surface
biocides and wood preservatives etc.
The pesticides have saved millions of lives by controlling
human disease vectors , greatly increasing the yields of
agricultural crops and protecting foodstuffs. In India agriculture is still
the main source of livelihood and the pesticides are among the most
usefiil tools available to man in order to get the crops properly grown
and fruitftilly harvested. Beyond any doubt the worldwide crisis of food
has been considerably removed with the help of pesticides. On the other
handjUsage of pesticides in agriculture has imposed many direct and
indirect undesirable effects on the environment i.e.chemical plant
protection is a profit induced poisoning of the envirormient.The
concentration of pesticides residues in food ,feed and environment is
increasing day by day due to their continuous use in crop protection .
The extent and seriousness of the potential hazards due to these
chemicals still remain to be frilly evaluated. The information that is
available so far on the occurrence of residues in the various parts of the
environment is very uneven and localized. Thus there is a genuine need
of pesticide residue analysis in our ecosystem. Therefore, several
instrumental and non instrumental methods have been used for the
detection, separation and determination of pesticides in different
environmental matrices.
B. CLASSIFICATION OF PESTICIDES
The pesticides have been classified as follows:
1. Inorganic Pesticides : About A.D. 70 Pliny the Elder recommended that
arsenic could be used to kill insects, and the Chinese used arsenic
sulphide as an insecticide as early as the late sixteenth century. Other
inorganic products used as pesticides contain antimony, boron, copper,
fluorine, manganese, mercury, selenium, sulphur, thallium, tin and zinc
as their active ingredients. Although these products are not very effective
for pesticidal use, many are so persistent in the soil that there are
instances as of crops being damaged by their residues in the soil.
2. Organic Pesticides : The era of organic pesticides began from 1940.
These chemicals are so successful in controlling the pests that there is
extremely rapid and general adoption of them and development of new
ones. This has progressed so rapidly, that today about 1500 pesticides in
the Ibrm of 10,000 formulations are in common use around the world.
Some of the commonly used pesticides are given below :
(a) Carboxylic acid derivatives : TCA, dalapon, 2,4-D, 2,4,5-T etc.
(b) Heterocyclic compounds : benomyl, carboxin, metalaxyl etc.
(c) Organochlorines : aldrin, BHC, DDT, endosulfan, heptachlor etc.
(d) Organonitrogens : baygon, carbaryl, carbofliran, dinocap etc.
(e) Organonitrogensulphurs : captafol, captan, folpet etc.
(f) Orga;iophosphates : bromophos, malathion, parathion, phosphamidon etc.
3. Organic Pesticides Containing Metal Ions : It is a relatively less
familiar class of pesticides. The activity of these pesticides depends on
the chelating action of the metal ion as well as the activity of the organic
matrix. Some of the organic pesticides containing metal ions (OPCM) are
given in Table 1.1.
C. DITHIOCARBAMATE PESTICIDES
Amongst OPCM mentioned above, the heavy metal complexes of
dithi )carbamate are well known fungicides. Tisdale first demonstrated
the fungicidal possibilities of the dithiocarbamate (thiram) in 1931 in the
laboratory of E.I. Du Pont Company, U.S.A. but the commercial
production started about a decade later.
It is employed in every use, i.e. contact, protective, eradicative
known for fungicides except systemic action. It is widely used on
vegetables like lettuce, peanuts, potatoes, tomatoes and brinjals; fruits
like apples, figs, grapes, peaches and pears; crops like cotton, maize,
paddy and wheat; ornamentals like chrysanthemums, black currants,
carnations etc. to control diseases like early and late blight, gall, mildew,
leaf spot, rust, scab, smut etc. It is used in seed and soil treatment.lt is
also laiown to use as topical ointment to cure dermatophytoses.
Table 1.1: Chemical structure and mode of action of some organic pesticides containing metal ions.
Pesticides Properties
1. Alloxvdim-sodium
ONa , N - 0 - C H r C H = CH,
0 = C-OCH,
a) Colourless cr>'stals
b) 2250-2560. > 1630
c) Selective, systemic herbicide
2. Aluminium phosethyl
H
- * II o
Al
a) Colourless ciystals
b) 5800. > 3200
c) S\steniic fungicide
3. Azocvclotin
a) Colourless crj'slals
b) 99. > 1000
c) Contact acaricide
4. Calcium cvanamide
Ca = N - C s N a) Grey powder
b) 765. -
c) Herbicide, fungicide and defoliant
Pesticides
5. Dikegulac-sodium
COONa
6. Disodium methanearsonate
o • ^ONa
CH - As ~ ONa
7. Fenaininosulf
(CH,y .N-f V N = N - SOjNa
Properties
a) Colouriess crystals
b) 31000, >2000
c) Systemic plant growth regulator
a) Colourless crystals
b) 1000,-
c) Selective post-emergence
herbicide
a) Yellow brown crystalline powder
b) 60,100
c) Seed and soil fungicide
8. Fentinacetate
AcOSn <3 a) Colourless crystals
b) 125-160,450
c) Non systemic leaf-fungicide, algidde and moUusddde
9. Ferbam
ac. H,C
S II
N-C-S-
-"s
Fc
a) Black powder
b) 4000-17000, -
c) Protective leaf - fungidde
Pesticides Properties
10. Mancozeb
H s I II
C H _ N - C - S -(b i -N-C-S-
I II H S
Mn, Zn
—ix (x>l)
a) Greyish - yellow powder
b) 5000, > 10000
c) Protective leaf-fiuigjcide
11. Maneb
H S I II
C H , - N - C - S -
C H - - N - C - S -^ I II
H S
Mn
- J X
a) Ydlow amorphous powder
b) 7500, > 5000
c) Protective leaf - fungicide
12. 2-Methoxyethylmercury chloride
CH,0-CH,-CH,-Hg-Cl
13. Metham - sodium
H , C - N - C - S N a
H S
a) Colouriess crystals
b) 570, -
c) Systemic fungicide
a) Colouriess crystals
b) 820, 97
c) Nematicide, fimgicide, insecticide and herbicide
14. Methyl - metiram
H H S I I II
H , C - C - N - C - S -^ I I
HjC-N -C-S-ZnCNHj)-
H S
H H S I I II
H j C - C - N - C - S -
H j C - N - C - S -I II
H S . X
(X>1)
a) Pale yellow powder
b) 1540, -
c) Protective leaf-fun^cide and acaricide
Pesticides Properties
15. Metiram
H s I II
H , C - N - C - S -
aC-N-C-S-Zii(NH,)
H S
- N - C - S -VcX - I R C - N - C
/ ^ I H A H S
- N - C - S -
a) Yellow powder
b) 10000, > 2000
c) Protective leaf - fvxngicide
(x>l)
16. Nabam
H s I II
H,C-N-C-S-Na • |
RC-N-C-S-Na ^ I II
H S
17. Naptalam
a) Colourless crystals
b) 395, -
c) Protective fungicide and
algicide
a) White crystals
b) 1900,-
c) Selective pre-emergence herbicide
18. Phenylmercury acetate
rvHs-o-Hg-O-COCH,
19. Potassium cyanate
K-N=C = 0
a) Pale yellow powder
b) 50-100, -
c) Eradicadve fiingjcide
a) Colouriess crystals
b) 841 . -
c) Herbicide
Pesticides Properties
20. Propineb
H H S i I II
H , C - C - N - C - S -
R C - N - C - S -1 II H S
Zn
(x>l)
a) Pale yellow powder
b) 8500, > 1000
c) Proteaiveleaf-fimgidde
21. Zineb
H,C-N-C-S-
H,C-N-C-S-I II H S
Zn
X
(x>l)
a) Light coloured powder
b) >5200,> 10000
c) Protective leaf - fungjdde
22. Ziram
H,C
S V II
N - C - S - Zn
-"2
a) White powder
b) 1400, > 20000
c) Protective leaf-ftm^cide and repellant
a) Physical appearance b) Acute oral LDj^(rats) and acute dermal LD^ , (rats) in mg/kg c) Mode of action
1. General Chemistry and Classification : The fundamental building
block of dithiocarbamate fungicides is dithiocarbamic acid. However, the
dithiocarbamic acid itself is not known to exist in the free state since they
quic Jy decompose to simple molecules i.e. carbon disulphide and
ammonia.
HS C NH2 • CS2 + NH3
When the substituted primary or secondary aliphatic or
aromatic amines are treated with carbon disulphide in alkaline solutions,
subs ituted dithiocarbamic acids are produced. Ri and R2 represent aryl or
Ri Ri
NH + CS2 • N C SH / /
R2 R?
alkyl organic radicals or in the case of primary amine, one of them may
happen to be hydrogen. The hydrogen attached to sulphur dissociates and
may be replaced by a metal having atomic no.>20, thus producing a
stable dithiocarbamates.
Ri
R7
NC SH Metal Salt
R.
R7
N C S M x+
y
As shown in Table 1.2, dithiocarbamates can be divided into
two main groupsiGroup I and Group II. The most noteworthy difference
between them being that the members of Group I do not have a H-atom
attached to carbamate-N while members of Group II have a H- atom
attached to the carbamate-N.
The fungicides of Group I have been further divided into two
subgroups:
a) Metal salts or metal complexes of dialkyldithiocarbamic acid e.g. ferbam,
ziram (9,22: Table 1.1)
b) Oxidation product of derivatives of dimethyldithiocabamic acid e.g.
thiram.
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Table 1.2: Classification of dithiocarbamates
Group Chemical Designation Types of derivatives
Dialkyldithiocarbamate
II Bisdithiocarbamate
Monomethyldithiocarbamate
Metal Derivatives
Na salt (no common name)
Zn complex (ziram)
Fe complex (ferbam)
Oxidation Product
S - iS linkage (thiram)
Metal Derivatives
Na salt (nabam)
Zn complex (zineb)
Mn complex (maneb)
Mixed complex (mancozeb)
Metal Derivatives
Na salt (metham-Na)
Dietliyl analogues of this subgroup are medically used to treat alcoholics.
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The fungicides in group II are ethylene derivatives. Among them,
few are salts like metham-sodium, nabam (13,16:Tablel.l) while other
are metal complexes like mancozeb, maneb, zineb (10,11,21: Table 1.1).
Mostly all forms of dithiocarbamates are biologically
interconvertible as sulphide forms which can be reduced to thiol or
sulphur, thus dissociating the metal complexes. The dithiocarbamates
fungicides are less persistent (relative to organochlorine pesticides);
however, there are evidences that they are persistent enough to have an
effect on the acquatic environment. These fungicides tend to be
somewhat unstable to heat, light and moisture. Solubility of these
fungicides is very low in water and most organic solvents.
2. Mode of Action : Despite the chemical similarities, there are evidences
that dialkyldithiocarbamates and ethylenebisdithiocarbamates do not act
in th.; same way. This different is often attributed to reactivity associated
with the N-H bond present in Group II complexes. The
dialkyldithicarbamates (Group I) interfere with energy production i.e.
reduction in the production of ATP for instance; inhibition of respiration.
They also interfere with biosynthesis i.e. the disruption of processes
forming new cellular materials needed for the growth and maintenance of
the fungus while ethylenebisdithiocarbamates interfere with the
biosynthesis process. Various theories have been proposed to explain, the
mode of action of dithiocarbamate fungicides but none of them explain
the mechanism of fungicidal action satisfactorily. The chelation theory is
one of the generally accepted theories.
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a) Dialkyldithiocarbamates : The dialkyldithiocarbamates probably owe
their fungitoxicity to their ability to chelate with certain metal ions, thus
depriving the cell of the needed metal ion. Recent information however
indicates that a heavy metal ion is required for the high toxicity of these
fungicides. Studies with the fungus Aspergillus niser have demonstrated 9-4-
that in the presence of Cu ions, an increase in the concentration of
sodium dimethyldithiocarbamate inhibits the growth at two levels:
(i) Whe i copper to dithiocarbamate ratio is reasonably high (approximately
20:1) the formation of unsaturated, positively charged
copperidithiocarbamate complex (1:1) takes place. These complexes
penetrate lipid barriers in the fungal cell and may be the ultimate toxicant
or alternatively it may be converted into free dimethyldithiocarbamate
ions which kill the fungus by readily complexing with vital trace metals.
For example it interferes in the uptake of oxygen in yeast cells and it has
also been shown that pyruvate accumulates in Aspergillus niger after
treatment with sodium dimethyldithiocarbamate, thus fungicidal activity
arises from interference with respiration by inactivation of the pyruvate
dehydrogenase system.
The charged resonating 1:1 complex between Cuions and dimethyl
dithiocarbamate
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(ii) When the concentration of dithiocarbamate is further increased
the fungicidal activity decreases due to the formation of saturated,
uncharged copper:dithiocarbamate complex (1:2). This inhibition level
requires high concentration of dimethyldithiocarbamate. When all the
internal heavy metals have been converted to dithiocarbamate complex
(1:2), excess dithiocarbamate accumulates and is apparently toxic in its
own right, perhaps by inactivating sulphydryl enzymes.
" ^ ^ \ . -^ S ^ ^ S < ^ / CH3
^ N - C ' . Cu C - N . "^ S ^ ' ^ S ^ ^ CH3 H3C - ^
. Cu C - N . "^ S ^ ' ^ S ^ ^ CH3
The uncharged 1: 2 complex between Cu ions and dimethyldithiocarbamate.
b) Ethylenebisdithiocarbamate : The presence of hydrogen at the nitrogen
in a dithiocarbamate structure considerably reduces the chemical stability
of the ethylenebisdithiocarbamates. The mode of action of this complex
probably involves their oxidation on the leaf surface to such products as
ethylene thiuram disulphide, ethylene thiuram monosulphide,
isothiocyanate (fungitoxic derivatives) by splitting off H2S or HS' ions
(Fig 1.1).
H S
R - N - C - S H z - - ^ H2S + R - N = C i : S
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H S • I I I
R - N - C - S v ' = ^ HS" + R - N = C = S
Especially in the presence of heavy metal ions these equilibria are forced
to the right because of the formation of insoluble metal sulphides. These
fungitoxic derivatives are known to be fungicidal by virtue of their ability
to react with vital thiol compounds within the fungal cells and it has been
demonstrated that the inhibitory action of nabam on fungal spore
germination is strongly antagonized by the addition of thiols.
3. Other Applications of Dithiocarbamates :
Besides the usage of dithiocarbamate as fungicides the following uses
have also been reported in the literature.
a) Additive in lubricating oil: Tanaka et al.' ' '* have reported a process for
producing molybdenum oxysulphide dithiocarbamates as lubricant
additives. These dithiocarbamates have been found to be good
antifriction and anticorrosive agents in lubricating oil.
b) Sulphur vulcanization: Niewenhuizen et al.'^ have published a review
with 262 references describing research methodologies useful in
investigating the mechanism of vulcanization and the reactivity of
thiuram and dithiocarbamate chemicals. The combined knowledge has
been subsequently applied to thoroughly review the mechanism and the
chemistry of both thiuram and dithiocarbamate accelerating sulphur
vulcanization.
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c) Graft copolymerization : Kim and Cho'^ have synthesized graft
copolymers by iniferter-containing macromer. A monomer such as
styrene, methylmethacrylate, ethylacrylate or butylacrylate were
copolymerised with chloromethylstyrene by AIBN initiation and the
chloride group in the polymer was treated with sodium
diethyldithiocarbamate to give dithiocarbamate groups . NMR analysis
showed that conversion to dithiocarbamate groups was quantitative for
acrylate copolymer as well as styrene copolymer. Graft copolymerization
of the macromer such as polystjo-ene macromer and PMMA macromer
yielded graft copolymers.
d) Chelating agents : Tandon et al.'^ have studied N-benzyl-D-
glucaminedithiocarbamate and its analog, N-(4-methoxybenzyl-D-
glucaminedithiocarbamate) which are effective chelators of cadmium for
their efficacy to induce excretion of lead and to reduce tissue burden of
lead in pre-exposed rats. These dithiocarbamates have been found to be
effective in reducing hepatic and renal lead levels but not of brain lead
levels.
e) Analysis :
(i) Spectrophotometry: A spectrophotometric method has been reported
for the determination of copper (11) using sodium diethyldithiocarbamate
as a colouring reagent. The method is based on the formation of a brown
suspension of the copper (II) diethyldithiocarbamate which can be
extncted with butyl acetate and the coloured extract can be analysed
spectrophotometrically at 560 nm. This method is sensitive to lOOjxg of
copper (II).
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(ii) Flotation of non-ferrous metals: Glinkin'^ has published a review with
8 refrences describing the flotation of non-ferrous sulphide minerals with
dithiv^carbamate reagents. It outlines the use of sodium
dimethyldithiocarbamate as a deppresor for sphalerite, iron sulphide and
S-cyanethyl-N,]sr-diethyldithiocarbamate as a collector for copper and
molybdenum sulphides. Data pertaining to industrial application of these
reagents has been reported.
(iii) Ion exchange: Airoldi et al ° in 1994 have studied the chemistry of
immobilized dithiocarbamate groups covalently attached to silica gel for
extraction of cobalt, nickel, copper and zinc cations in ethanolic
solutions. They have reported that a metal : a ligand ratio of 1:3 for
cobalt, 1:2 for nickel and 1:1 for copper and zinc complexes in ethanolic
solution.Tang et al.^' in 1998 have reported that the simultaneous
preconcentration of beryllium , bismuth , cobalt, gallium , silver, lead,
cadmium, copper, manganese and indium in sea water by using
poly(acrylamino phosphoric dithiocarbamate) chelating fiber as an
adsorbent.The optimum experimental parameters such as fiber capacity,
pH, sample flow and volume, eluant and effect of matrix ions on the
preconcentration have been investigated . It has been claimed that the
metal ion can be concentrated to 200 times in a short time and the
technique can be coupled with inductively coupled argon plasma - mass
spectroscopy (ICP-MS) to provide a promising method for the
determination of trace elements in sea water.
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f) Synthesis of new compounds:
(i) Sulfines: Cherrie and Metzner have demonstrated that the oxidation
reaction of various dithiocarbamates give corresponding sulfines
(S-oxides). A number of sulfines could be isolated and characterized
although their stabilities are very moderate. The sulfines decomposed to
thiocarbamates and dithiocarbamates on keeping them at ambient
temperature.
(ii) Drugs: Ching ^ has proposed a new method of synthesis of conjugates of
nitric oxide scavengers (e.g. dithiocarbamates) with drugs (e.g.
NSAIDS). These conjugates provide a new class of drugs (e:g anti
inflammatory agents). These conjugates have much lower incidence of
side effects and they are more effective than unmodified drugs because
cells and tissues contacted by them are protected from the potentially
damaging effects of nitric oxide over production . For instance, ibuprofen
is esterified with 2- pyrrolidinol in the presence of dithiocarbamate and
resulting ester was treated with aqueous sodium hydroxide solution and
carbon disulphide in ethanol, thus producing a dithiocarbamate of
pyrrolidinol- ibuprofen.
4. Carbamates Residues Analysis: The following analytical methods
have been used for analyzing carbamates residues in different matrices:
a) Spot test : Spot tests are simple, sensitive, selective or specific,
inexpensive and rapid. This spot test analysis has been found to be
extremely useful for the preliminary on-field detection of pesticides.
Generally, a preliminary examination of a test material is required before
undertaking costly and sophisticated quantitative analysis in order to
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minimize time and operation costs. Recently, the following tests have
been developed for the detection and semi-quantitative determination of
pesticide residues in environmental samples.
A Paper spot test has been developed^"^ for the detection of carbaryl in
water. To carry out this test a paper strip impregnated with sodium
hydroxide was spotted with carbaryl and then it was treated with 2,6 -
dichloroquinone - 4 - chloroimine. A violet spot appears if carbaryl is
present. The lower limits of detection is found to be 0.06 p,g / spot. The
tentative mechanism is given in scheme no. 1.
Padalikar et al. ^ have reported a thin layer
chromatography spot test for the determination of carbaryl. Slica gel G
coated thin layer chromatography (TLC) plates spotted with carbaryl
gives violet colour on treating with copper (II) chloride solution followed
by ammonium metavandate reagent. The lower limits of detection for
carbaryl and 1 - naphthol are 10 |Lig / spot and 1 \ig I spot respectively.
The lower limit of detection is 1 fig / spot for carbaryl and 1 - naphthol
both when alkaline hexacyanoferrate (III) is used as a chromogenic
reagent. Other insecticides such as malathion, parathion, dimethoate,
sumithion, ekalax, eldrin, DDT, baygon, carbofuran and zineb do not
interfere. The tentative mechanism is given in scheme no.2. A selective,
sensitive, simple and inexpensive spot test is described^^ for the detection
of mancozeb at trace levels in the soil, vegetation and water. It is based
upon the intensive catalytic action of dithiocarbamates on the production
of nitrogen from sodium azide reaction with iodine. The chemical
reactions involved are given in scheme no. 3. A spot test has been
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97
developed for the on-field detection of dithiocarbamates fungicides at
)ig levels in soil, vegetation and water. Copper - ammonia complex on
cation - exchange resin beads in presence of diethanolamine has been
used as a chromogenic reagent for carbon disulphide.The reaction
involved has been shown in scheme no.4. A spot test has been
developed^^ using sulphanilic acid - sodium nitrite - sodium hydroxide, 8
- hydroquinoline and alkaline hexacyanoferrate (III) as colouring
reagents for the sensitive and selective detection of carbaryl at jig level in
environmental samples. The tentative reaction mechanism is shown in
scheme no. 5. A already known, spot test for dithiocarbamates , is
extended for the selective detection of mancozeb at jug levels in its
formulations and water. Copper (II) chloride - acetic acid is used as a
colouring reagent. The reaction mechanism is shown in scheme no. 6. A
colour reaction based on the formation of black lead sulfide by
treatment of mancozeb with alkaline plumbite solution has been
developed for the thin layer chromatography (TLC) detection of
mancozeb.The lower limit of detection on a silica gel plate is 0.45 }xg /
spot. Fungicides other than dithiocarbamates do not interfere with the
test. The test can also be applied for the detection of mancozeb in soil
extracts. A tentative reaction mechanism is shown in scheme no. 7.
b) Spectroscopic and spectrophotometric methods: These methods are
simple, direct, sensitive and rapid but they do not achieve the sensitivity
of thin layer chromatography and gas chromatography techniques. They
may not be able to distinguish between the parent compound, and its
metsbolites and hydrolysis products but they can be used with
20
chromatography as a confirmatory technique. Spectrophotometry is a
reliable and routinely used technique that is readily available for analysts.
A few papers have been reported in this area.
CuUen^^ has carried out spectrophotometric determination of zineb,
maneb, ziram, ferbam, thiram and metiram residue on food crops. The
residues were decomposed on the crop and the evolved carbon disulphide
was collected and reacted with cupric acetate - diethanolamine in ethanol
(0.0016%) to form the yellow cupric salt of N, N bis (2 - hydroxyethyl)
dithi acarbamic acid which can be measured colorimetrically at 435 nm.
The speed of decomposition of the dithiocarbamate and the copper -
carbon disulphide ratio were found to be critical factors. This method is
sensitive to 20 |j,g of carbon disulphide. 0 1 ^
Rathore and varshney have carried out spectrophotometric
determination of sodium diethyldithiocarbamate (NaDDC), Ziram using
copper (II) as a colouring agent. Slightly ammonical solution of copper
(II) reacts with dithiocarbamate to produce a brown colloidal suspension
of the copper (II) dithiocarbamate. The suspension was extracted with
organic solvent (butyl acetate) and the coloured extract analysed
spectrophotomerically at 430 nm. The lower limits of determination is
100 i.'.g of ziram.
c) Volumetric method : A simple, inexpensive and rapid complexometric
titration has been developed for the determination of
mancozeb.The procedure is based on the fact that mancozeb
dissolves (at ppm level) in ammonia buffer of pH 10 in presence of
versenate solution. The quantification is made on the basis of versenate
21
consumed in the process of dissolution. The end point was detected by
using visual indicator, Eriochrome BlackT which gives wine red colour
with zinc (II) and manganese (II) and changes to sky blue at the end point
on titrating with versenate solution at pH 10.
d) Atomic absorption spectrophotometric methods : Rathore et al. ^ have
carried out atomic absorption spectrophotometric determination of
mancozeb residues, micronutrients (Mn^^ and Zn " ) in plants. It is based
on the decomposition of organic matrix by treating mancozeb with
oxidizing mixture ( nitric acid - perchloric acid ) and the determination
of zinc or manganese in the residue by using atomic absorption
spectrophotometer. The lower limits of determination has been reported
to be at ppm level. The results of atomic absorption spectrophotometry
have been compared with those obtaind by volumetry in which disodium
salt of ethylene diaminetetraacetic acid, Eriochrome Black T and
ammonia buffer of pH 10 have been used.
e) Chromatographic methods:
(i) High performance liquid chromatography : Weissmahr et al. "* have
carried the analysis of the dithiocarbamate fungicides : ziram, maneb and
zineb and the flotation agent ethyl xanthogenate by ion - pair reversed -
phase high performance liquid chromatography in the natural water. The
method is based on the in situ formation of a 1:1 Cu (II) - dithioligand
complex and its separation, at an ion - pair with hexane sulphonate on a
C- 1 d reversed - phase column and detected as 260 - 287 nm. Detection
limits are reported to be 3 [ig/ L (ziram), 9ng/ L (maneb) and 4 |ig/L
(ethyl xanthogenate).
22
Zhou et al. ^ have established a derivative high performance liquid
chro iiatography method for quantitative determination of cisplatin in
emulsions. Cisplatin was extracted by dimethylsulphoxide (DMSO) from
emulsions and reacted with sodium diethyldithiocarbamate (NaDDC) to
produce a Pt(DDC)2 complex, which was extracted by chloroform and
detected at 254 nm. An analytical column, U- Bondapak - C18H37 (5 \im,
150mm X 4m) was used with MeOH - H2O (80:20) as the mobile phase
at a flow rate of Iml/min.Nickel chloride was used as an internal
standard. The main recovery of extraction has been found to be 78.4%
with relative standard deviation < 5%.
(ii) Gas chromatography : Woodrow et al have trapped air borne
particulate residues that resulted from commercial applications of the
dithi:)carbamate fungicides (ziram and mancozeb) on glass fiber filters at
14 - 16 L / min upto 24 hrs. Hydrochloric acid hydrolysis, with stannous
chloride reduction, is used to convert these residues to carbon disulphide,
which is partitioned into isooctane for assay using sulphur mode flame
photometric gas chromatography. Limits of detection have been found to
be about 0.3 [ig (ziram) and 0.5 ,g (mancozeb) per filter, which are
equivalent to about 14 - 23 ng W (24hrs).
(iii) Thin layer chromatography : It has been reported that the admixtures of
heavy metal^^ ions such as Mn^ , Fe ,Co^ ,Ni ,Cu^ ,Bi '*" and Ag^ can be
separated on cellulose plates impregnated with sodium
diethyldithiocarbamate using organic solvents as mobile phase.
(iv) Paper chromatography: Rathore and Kumar^^ have performed
chromatography of Mn^^ Fe "", Fe^^ Co^^ Ni^^ Cu^^ Zn^^ Cd^\ Hg^\
23
Hg* and Pb^^ on paper strips impregnated with sodium diethyl
dithiocarbamate and its admixtures with Si02,CaS04, Na2C03, NaCl,
NH4CI, EDTA, NaOH, CaCOa, Na2HP04 and H3PO4. Several binary
separations have been achieved experimentally.
D. WORK DONE
The candidate has made efforts to develop a new spot
test for the detection of fungicides such as mancozeb, propineb
sodiumdiethyldithiocarbamate, zineb in soil and water. The colour
formation is based on the decomposition of dithiocarbamate to carbon
disulphide which reacts with plumbite in alkaline medium to form a
brown complex that finally converts to black lead sulphide. The coloured
product exists as a bright brown- black colloidal solution in
formaldehyde or glycerin or hydroxylaminehydrochloride. The lower
limit of detection is nkg. The results obtained are described in this
dissertation.
24
CONHCH. H
+ NaOH
Carbaryl 1-naphthol
OH Ck
+ 0 = <
CI'
Cls
>=NC1—*-0=<
cr
>=M—<f \ - O N a
\ /
1-naphthol 2,6-dichloroquinone-4-chloroimine
Indonaphthol dye (Blue)
Scheme l:Colour reaction of carbaryl with 2,6-dichloroquinone-4-chloroimine
1 \oc. '^lni'^^ \y
25 ^
CONHCH,
+ NaOH
Carbaryl 1-naphthol
+ Ammonium metavandate
l-naphthol
O
OH
\ / \ / Violet
Complex
Fe[(CN)6H20]3- +
OCONHCH3
(CN)6 I 3-
+ H2O
Ali<aline Carbaryl hexacyanoferrate
Carbaryl hexacyanoferrate (Violet colour)
Scheme 2:Colour reaction of carbaryl with ammonium metavandate and hexacyanoferrate
26
Dithiocarbamates ^ ,^, I 2NaN3 + I, ; *- 2NaI + 3N2T
act as catalyst
Sodium Sodium azide Iodide
Scheme 3: Vigorous evolution of bubbles of nitrogen by using dithiocarbamate as a catalyst.
RjN-C-S Na+ + H2SO4 *• R2NH + CS2 + NaHS04
Cu++ + NH4OH *- Cu(NH3)4++ Blue complex
Cu^ + CS2 + R2NH —*- R^NCSjCu^
yellow complex
Cu(NH3)4++ + CS2 + R2NH *- R2NCS2CU (NH3)4+
red complex
Scheme 4:Colour reaction of copper-ammonia complex with dithiocarbamate.
27
(a) HO3S , — / ^NH2+HN02+H^ HO3S / \ - N ^ ^ N + 2H2O
Sulphanilic acid Diazobenzene Sulphonic acid
HO3S—< > N " = N
ONHCH,
HO,S-/ V N = = N Y \oCONHCH3
Diazobenzene Carbaryl Sulphonic acid
\ / + H"
Dye stuffs (Pink colour)
0=< >=NOH
^ V 5-nitroso-8-hydroxyquinoline Oxime
0=< >=NOH
N ' ^ ^
Oxime
:0NHCH3
Carbaryl Brown colour
ONHCH3
(c) Fe[(CNV,H20]^- + (CN), + H,0
Alkaline Carbaryl hexacyanoferrate
Carbaryl hexacyanoferrate (Violet colour)
Scheme 5:Colour reaction of carbaryl with (a) sulphanilic acid in the presence of sodium nitrite (b) 5-nitroso-8-hydroxyquinoline (c) alkaline hexacyanoferrate (III).
28
iff ft CH2-N-C-S\ CHj-N-C-S. CH2-N-C-S^
M + Cu(CH3COO)2 1 ^ ^ c u + M(CH3COO)2 " ^ H S
Yellow salt Yellow brown colour
Where M=Zn"'2 or Mn-*"
Scheme 6: Colour reaction of mancozeb with copper acetate
CH2-N-C-S\ CH2-NH2 Irj XT c/f^ +4Na,Pb02 + 6H20 • | + 2CO2 + 8NaOH + 4PbS + M(0H)2 CH2-N-C-S - CH2-NH2
H S
Yellow salt Yellow brown colour Black ppt
Where M=Zn"'- or Mn+-
Scheme 7: Colour reaction of mancozeb with lead plumbite
29
E. REFERENCES
1. Ware G. W., ''The Pesticides Book", eds. W. W. George ,W. H.
Freeman and Company, San Francisco, 1978.
2. "Analysis of Pesticides in Water : Nitrogen Containing Pesticides'',
eds. A. S. Y. Chau, B. K. Afghan and J. W. Robinson , CRC Press ,
Boca Raton, 1982.
3. Scaroni I., Previati M. P. and Bovolenta A., "Handbook of Food
Analysis : Residues and Other Food Component Analysis (Fungicide
Residues in Foods) ", ed. Leo M. L. Nollet, Vol. 2"^, Marcel Dekker,
New York, 1996.
4. "Handbook of Water Analysis", ed. Leo M. L. Nollet, Marcel
Dekker, New York ,1999 (In Press).
5. "The Pesticide ManuaF, ed. C. R. Worthing, 8* ed., British Crop
Protection Council, Lavenham, 1987.
6. "The Agrochemical Handbook', eds. D. Hartley and H. Kidd, The
Royal Society of Chemistry, England, 1983.
7. "Farm Chemicals Handbool^\ ed. G. L. Berg, Meister Publishing
Company Willoughby, Ohio, 1980.
8. "Analytical Reference Standards and Supplemental Data for
Pesticides and Other Organic Compounds", ed. R. R. Watts,
Environmental Protection Agency, U.S., 1981.
9. Ramulu U. S. S., "Chemistry of Insecticides and Fungicides", 2"''
ed., Oxford and IBH Publishing Co., New Delhi, 1996.
10. Weisberg E. D "Medicinal Chemistry", ed. A. Burger ,3'''' ed., vol. 1'',
Wiley Interscience, New York, 1970.
30
11. Nene Y. L. and Thapliyal P. N., "Fungicides, in Plant Disease
Control".,?)"^ Qd., Oxford and IBH Publishing Co., New Delhi, 1993.
12. Hassall K. A., ''Chemistry of Pesticides , Their Metabolism , Mode of
Action and Uses in Crop Protection", Macmillan Press Ltd., London,
1992.
13. TanakaN., Fukushima A., Tatsumi Y., Morita K. and Saito Y., Eur.
Pat. EP 727429/1996 (Chem. Abstr., 1996,125, 236920).
14. Tanaka N., Fukushima A., Tatsumi Y., Morita K. and Saito Y., Jap.
Pat. JP 1017586/1998 {Chem. Abstr., 1998,128, 104231).
15. Nieuwenhuizen P. J., Reedijk J.,Van D. M.and Mc Gill W. J., Rubber
Chem. Technol, 1997, 70 (3), 368-429.
16. Kim S. and Cho C. G., Pollimo., 1997, 21 (6), 947-954.
17. Tandon S. K., Singh S. and Prasad S., Hum. Exp. Toxicol., 1997, 16
(10), 557- 562.
18. Basett J., Denney R. C , Jeffery G. H. and Mendham J.,''Vogel's
Text Book of Quantitative Inorganic Analysis",4'^ ed., ELBS:
Longman Crop, 1998, 155-156.
19. Glinkin V. A., Obogashch. Rud (S.- Peterburg)., 1997,4, 22-24.
20. Espinola J. G. P., Freitas J. M. P., Oliveira S. F. and Airoldic,
"Physicochemical and Engineering Aspects"., 1994, 87, 33-38.
21. Wen B., Shan X.. Q., Liu R. X. and Tang H. X., Fresenius J. Anal
Chem.,\999, 363(3), 251-255.
22. Cherrie D. and Metzner P., Tetrahedron Lett., 1998,39(49),8983-8986.
23. Ching S., Chem. Abstr., 1999,130, 57211.
24. Rathore H. S. and Saxena S. K., Anal. Lett., 1990, 23, 93-118.
31
25. Padilkar S. V., Shinde S. S. and Shinde B. M., Analyst, 1998, 113,
1747- 1748.
26. Rathore H. S., Kumar S. and Singh Y. N., J. of Indian Chem. Soc,
2001,78,422-423.
27. Rathore H. S., Mital S., Kumar S. and Singh Y. N., Proc. Not
Acad. Sci. India., 2001, 71(A), 176-183.
28. Rathore H. S., Sharma R. and Mital S., Water, Air and Soil Pollution.,
1997,97,431-441.
29. Rathore H. S., Mital S., Journal of planar Chromatography., 1997,
10,124-127.
30. Cullen T. E., Anal. Chem., 1964, 36 (1), 221-224.
31. Rathore H. S. and Varshney C , (Unpublished work).
32. Rathore H. S. and Mital S., J. Indian Chem. Soc, 1999, 76, 355-356.
33. Rathore H. S., Rao R. A. K. and Kumar M., J. Indian Chem. Soc,
2004,81,616-617.
34. Weissmahr K. W,, Houghton C. L. and Sedlak D. L., Anal. Chem.,
1)98, 70 (22), 4800-4804.
35. Zhou Q. and Yu. Y., Zhongguo Yiyuan Yaoxue Zazhl, 1997,19 (2),
78-79.
36. Woodrow J. E., Seiber J. N. and Fitzell D., J. Agric Food Chem.,
1995,43(6), 1524-1529.
37. Rathore H. S. and Singh Y. N., J. of Planar Chromatography., 2002,
15,361-366.
38. Rathore H. S. and Kumar M., J. of Indian Chem.Soc, 2005, (In Press).
32
CKJKFM^- II
A O^'W StPOT liEST 'F0<^ "tm (i>E'mciio9{ o<F conmocA'K^AMJi'M TV9{gici(iyE3 i9f SOIL jmD WAT^^
A. INTRODUCTION
Dithiocarbamates^ such as mancozeb, propineb and zineb are
being used as agricultural fungicides in grapes, cauliflower,
potato, chillies, apples, groundnut, paddy etc. The pesticides
residues concentration is increasing day by day in the
environment due to their repeated use for the long period. The
pesticides residues analysis involves five steps such as
qualitative detection, preconcentration or extraction, separation
or clean up, estimation and then identification. Spot test analysis
has been found to be extremely simple, inexpensive and useful
for the preliminary characterization/detection of the pesticides
residues in an environmental matrix.
Therefore, in continuation to our previous work ' it
was thought worthwhile to develop a new spot test by studying
exhaustively a brown colour reaction of dithiocarbamates with
plumbite in presence of formaldehyde. This spot test was firstly
reported by Feigl and Weisselberg^ in 1931 and secondly, by
Posen Thaler^ in 1933 for the detection of carbon disulphide. It
is based on the decomposition of dithiocarbamates into carbon
disulphide which produces brown-black colour with plumbite in
presence of formaldehyde. Now efforts have been made to
utilize this reaction for the detection of dithiocarbamate
fungicides in water and soil. The results obtained are described
in this paper.
33
B. EXPERIMENTAL
1. Apparatus: Aluminium heating block, U-tube, micro-test tube,
Whatman-1 filter paper etc. were used.
2. Chemicals and Reagents: Mancozeb (75%WP) (Modem Insecticides
Ltd., India); Proplneb (70%WP) (Bayer Chemicals Company, India);
Sodiumdiethyldithiocarbamate (97%) (CDH Chemicals Company, India);
Zineb (75%WP) (Indofil Chemicals Company, India); lead monoxide
(Qualigens Fine Chemicals, India); Formaldehyde solution (37-
41%WA' ) in water were used. All other reagents and chemicals used
were of analytical grade.
3. Preparation of Solutions: Plumbite reagent (Pbt) was prepared by
dissolving lead monoxide (Ig) in 32% aqueous sodium hydroxide
solution. The homogeneous suspensions of 0.75% mancozeb, 0.70%
propineb and 0.75% zineb were prepared in distilled water (DW).
Solutions of 1% sodium diethyldithiocarbamate (NaDDC), 40% sucrose,
10%) ascorbic acid, 40%) glucose, 2% starch, 40%) hydroxylamine
hydrochloride, 5% potassium permanganate and lOM sulphuric acid were
also prepared in DW.
4. Preparation of Indicator Paper: The paper strip of whatman-1
filter paper (lx4cm) was dipped in a watch glass containing the
reagent, the excess reagent was drained off and then it was used for
detection. Always freshly prepared indicator paper was used.
34
5. Collection of Soil Samples:Loam soil from Jattari village in tehsil
Khair, clay loam from tehsil Sikandra-Rao and from the barren
fields around Aligarh Muslim University (A.M.U.)> silty clay loam
from tehsil Atrauli from the fields in the neighbourhood of sankra
bus- .tand about 3km from the river bank, agricultural farm soil
from A.M.U., were collected from district Aligarh (U. P.)- Red soil
was collected from Bhubaneswar (Orissa). The sampling was done
during the month of April. To obtain a composite sample, small
portions of soil were collected from the desired depth (0-15 cm or
more) with Khurpi from 10-15 well distributed spots (from each
sampling Unit i.e., a plot) after scrapping off the surface litter. A
V-shaped cut (upto the plough layer) was made and a uniformly 1.5
cm (approx) thick slice was taken out. The soil collected in this
manner was thoroughly mixed on a polythene sheet or concrete
floor and bulk reduced by quartering and about 500g of the
com losite sample was retained. The soil was quickly air dried in
shade at room temperature and put in polythene bag with suitable
description and identification marks by tagging.
6. Detection Procedures:
a) Detection in solution: Analyte (0.1ml of 1%) was taken in a
micro-test tube, 3-4 drops of the reagent were added to it and after
thorough mixing the colour developed at room temperature
(25±3°C) and at elevated temperature (55±5°C) was noted. In
second attempt, the analyte was treated with one drop of dilute
sulphuric acid (lOM), the reagent was added and the colour
35
developed was noted. In third attempt, the mixture of the analyte
and the sulphuric acid was briefly heated, then the reagent was
added and the colour developed was recorded.
The lower limit of detection (LLD) was measured by using the
known volume (0.1ml) of the standard analyte solutions of different
concentrations in the later procedured.
b) Vapour phase detection:
(i) Indicator paper detection:The analyte solution (0.1 ml of 1%) was
taken in a micro-test tube. The moisture contents were removed by
heat'ng at 50-70°C. The contents were cooled to room temperature
and a drop of cone H2SO4 was added to it. The indicator paper was
hung in the test tube. The contents were heated at 25-150°C. If
indicator paper turns brown-black the dithiocarbamate is present.
The LLD was measured by taking the known volume (0.1ml) of the
standard solutions of the analyte of different concentrations.
(ii) U-tube detection:The analyte solution (0.1ml of 1%) was taken in a
test tube A (9.8 x 1.2cm, inner diameter) jointed with a side U-
tube' (16.9x0.3 cm, inner diameter). The moisture was removed by
heating, the contents were cooled to room temperature, one drop of
lOM H2SO4 was added to it and the reagent (0.1ml) was taken in
the : Ide U-tube. The tube A was stoppered and heated at 60-150°C
to bubble the fumes (CS2) through U-tube containing the reagent.
The change in colour of the reagent was noted after one minute.
36
The LLD was measured by taking the known volume (0.1ml) of the
standard solutions of the analyte of different concentrations.
(iii) Detection in soil: A soil sample (lOmg) was taken in a micro-test
tube, dithiocarbamate solution (0.1ml of 1%) was added to it and
the above procedures were used to detect the dithiocarbamate.
A soil sample (2g) was taken in a watch glass, it was
treated with dithiocarbamate solution (2ml of 1%) and the sample
was dried at room temperature. A portion of the treated soil was
tested for dithiocarbamate using the above procedures. This study
was conducted for 10-15 days and the dithiocarbamate residue was
found to be present. The LLD in soils was measured by adding
known volume of standard solutions of dithiocarbamate under
study in the known weight of soil sample.
C. RESULTS AND DISCUSSION
Table 2.1 shows the nature of the colour developed with NaDDC
and mancozeb with several reagents at 25+3°C and 55 + 5^C. The
LLD of NaDDC, mancozeb, propineb and zineb are given in Table
2,2.Table 2.3 shows the results of detection of above
dithiocarbamates in soil using different reagents and techniques.
The results of detection of zineb and propineb in different types of
soils are summarized in Table 2.4.
It has been reported^''° that xanthates, thioxanthates
dithiocarbamates, thiuram disulphides etc on acidification liberate
37
carbon disulphide. Carbon disulphide is converted into
trithiocarbonate on treatment with alkali hydroxide:
3CS2 + 6K0H -> 2K2CS3 + K2CO3 + 3H2O
The trithiocarbonate reacts with heavy metals to give
insoluble salts, which can be readily decomposed with the
formation of sulphide. Carbon disulphide can be quickly converted
into lead sulphide by treatment with cone, caustic alkali and a
plumbite solution. However, it is not applicable at trace level of
carbon disulphide. Feigl'^has remarked that the formation of
trithiocarbonate and hence of PbS can be accelerated by
formaldehyde for a reason that is not understood. Acetaldehyde,
benzaldehyde, arabinose, glucose and lactose show the same effect.
This action affords a means of detecting small amount of carbon
disulphide. Hence the spot test under study seems to be promising
for the nanokilogram detection of dithiocarbamates fungicides in
environmental samples.
Table2.1 shows that NaDDC does not give colour with
plumbite and it produces colour with plumbite in presence of dilute
acid at room temperature as well as at elevated temperature.
However, mancozeb produces colour directly with plumbite. It may
be due to the fact that NaDDC does not split off to CS2 without
acid while mancozeb produces colour without acid. This
observation is on line with literature i.e., dithiocarbamates are
unstable in acidic medium and heavy metal dithiocarbamates are
38
readily decomposed to give sulphides. The results given in Tables
2.1,2.2 and 2.3 show that the bright colour was obtained with
reagent plumbite-formaldehyde (3:1) provided that plumbite was
addtd first and then formaldehyde i.e., if formaldehyde was
followed by plumbite good bright colour was not produced. The
admixtures of plumbite and formaldehyde also produce bright
colour. The bright colour was also obtained when glycerin or
hydroxylamine hydrochloride was used in place of formaldehyde.
Hence hydroxylamine hydrochloride and formaldehyde are
reducing agents while glycerin has not been reported to be a
reducing agent. Therefore, either reducing or oxidising nature of
the reaction medium does not play any role in this colour reaction.
It was also observed that the rate of settling of brown-black
precipitate is in the following sequence:
Paraffin < CCI4 < gum < fevicol < detergent < HC1< ethanol <
distilled water < NaOH< glycerin < formaldehyde.
Hence it seems that the fine particles of plumbite
sulphide exist as colloidal particle in glycerin and formaldehyde.
Thus the role of glycerin or formaldehyde or hydroxylamine
hydrochloride is to form bright brown-black colloidal system at
nKg level of dithiocarbamates. The colour reaction understudy is
10 times more sensitive in solution state than vapour state.
The results reported in Tables 2.1,2.2 and 2.4 show that
the common impurities such as hardness causing substances.
39
detergent, silt, clay and soil do not produce any colour with the
reagent. Therefore, spot test under study can be successfully used
for the detection of dithiocarbamates in soil and water.
D. CONCLUSION
The spot test under study can be successfully utilized for the
trace level detection of dithiocarbamate fungicides in water and
soil. It is 10 times sensitive in presence of formaldehyde or
glycerin or hydroxylamine hydrochloride than that in presence of
acetaldehyde, benzaldehyde, arabinose, glucose, lactose, starch etc.
40
Table 2.1: Detection of dithiocarbamates using sodium plumbite and
its admixtures admixtures as tiie reagent
Aaatyte Reagent Colour Reagent
NaDDC Mancozeb
Reagent
RT ET RT ET
TS Pbt NC NC DY-Br Bl
TS+H2SO4 Pbt Br LBl Br Bl
TS+H2SO4+AT Pbt Br LBl DBr Bl
TS Formaldehyde NC NC NC NC
TS+H2SO4 Fonnaldehyde NC NC NC NC
TS+H1SO4+AT Formaldehyde+Pbt" Br Bl DBr Bl
TS+H2SO4+AT Pbt+Fonnaldehyde'' DBr Bl DBr Bl
TS Formaldehyde+Pbt* NC NC Br Bl
TS+H2SO4+AT Pbt: Formaldehyde'"': :2:1 Br DBr DBr Bl
TS+H2SO4 Formaldehyde+Pbt*: ::3:1 NC Br NC Br
TS+H2SO4 Pbt+Formaldehyde*' ::3:l NC LDBr NC LDBr
TS+H2SO4+AT Formaldehyde+Pbt': ::3:1 NC Br NC Br
TS+H2SO4+AT Pbt+Formaldehyde'' ::3:1 Br Bl DBr Bl
TS Sucrose NC NC NC NC
TS+H2SO4 Sucrose NC NC NC NC
TS+H2SO4+AT Sucrose+Pbt" NC Y-Br Br Bl
TS+H2SO4+AT Pbt+Sucrose'' LBr LBr DBr Bl
TS Sucrose+Pbt" NC NC LBr Bl
TS+H2SO4+AT Pbt: Sucrose" ::2:1 Br DBr DBr Bl
TS+H2SO4 Sucrose+Pbt* ::3:1 NC VLBr NC NC
TS+H2SO4 Pbt+Sucrose'' ::3:1 NC Br DY Bl
TS+H2SO4+AT Sucrose+Pbt" ::3:1 NC LBr NC NC
TS+H2SO4+AT Pbt+Sucrose'' ::3;1 Br LDBr DBr Bl
TS Glucose NC NC NC NC
TS+H2SO4 Glucose NC NC NC NC
TS+H2SO4+AT Glucose+Pbt' Br DBr Br DBr
TS+H2SO4+AT Pbt+Glucose'' DBr Bl DBr Bl
41
Table 2.1 contd....
TS GlucosefPbt*
TS+H2SO4+AT PbtiQucose'' ::2:1
TS+H2SO4 GIucose4-Pbt*:;3:l
TS+H2SO4 Pbt+GJucose'':.3:l
TS+H2SO4+AT Glucose+Pbt* ::3:1
TS+H2SO4+AT Pbt-KaucoseV:3:l
TS Starch
TS+H2SO4 Starch
TS+H2SO4+AT Starch+Pbt*
TS+H2SO4+AT Pbt+Starch''
TS Starch+Pbt*
TS+H2SO4+AT PbtrStarch' ::2:l
TS+H2SO4 Starch+Pbt* ::3:1
TS+H2SO4 Pbt+Starch** ::3:1
TS+H2SO4+AT Starch+Pbt* ::3;1
TS+H2SO4+AT Pbt+Starch" ::3:1
TS Ascorbic acid
TS+H2SO4 Ascorbic add
TS+H2SO4+AT Ascorbic acid+Pbt*
TS+H2SO4+AT Pbt+Ascorbic acid"
TS Ascorbic acid+Pbt*
TS+H2SO4+AT Pbt:Ascorbic acid' :: 2:1
TS+H2SO4 Ascorbic acid+Pbt* : :3:1
TS+H2SO4 Pbt+Ascorbic acid":: 3:1
TS+H2SO4+AT Ascorbic acid+Pbt* 3:1
TS+H2SO4+AT Pbt+Ascorbic acid" :3:I
TS Dimethyiamine
TS+H2SO4 Dimethylamine
TS+H2SO4+AT Dimeth^amine+Pbt*
TS+H2SO4+AT Pbt+Dimethylamine"
TS Dimethylamine+Pbt*
TS+HiSO^+AT PbtiDimethylamine' :2:l
TS+H2SO4 Dimethylamine+Pbt* ::3:1
NC NC Br DBr
Br DBr NC NC
NC NC NC NC
Br LDBr LBr Br
NC NC NC NC
DBr Bl DBr Bl
NC NC NC NC
NC NC NC NC
VLBr VLBr DY Bl
DBr DBr Br Bl
NC NC NC DY-Bl
NC VLBr Br DBr
NC NC NC NC
VLBr VLBr DY Bl
NC NC NC NC
DBr DBr Br Bl
NC NC NC NC
NC NC NC NC
Br DBr Br DBr
DBr Bl DBr Bl
NC DBr Br DBr
NC DRBr NC Br
NC NC NC NC
NC NC NC NC
NC NC NC NC
DBr Bl DBr Bl
NC NC NC NC
NC NC LBr Br
NC VLBr DBr Bl
DBr LDBr Br DBr
NC NC DY Bl
Br LDBr DY Bl
NC NC DY Bl
42
Table2.1 contd....
TS+H2S04 Pbt+Dimethylamine'' ::3:l NC NC LBr Bl
TS+H2S04+AT Dimethylamine +Pbt* ::3:1 NC NC DY Bl
TS+H2S04+AT Pbt+Dimethylamine'' ::3:1 DBr LBl Br Bl
TS Silica gel NC NC NC NC
TS+H2SO4 Silica gel NC NC NC NC
TS+H2SO4+AT Silica gel+Pbt* VLBr VLBr Y Bl
TS+H2SO4+AT Pbt+Silica gel'' LBr LBr LDBr LBl
TS Silica gel+Pbt" NC NC DY LBl
TS+H2SO4+AT Pbt: Silicager::2:l NC VLBr NC Br
TS+H2SO4 Silica gel+Pbt* :.3:1 NC NC LY LBr
TS+H2SO4 Pbt+Silica gel ••:: 3:1 NC NC LBr Bl
TS+H2SO4+AT Silica gel+Pbt'::3:1 NC NC NC NC
TS+H2SO4+AT Pbt+Silica gel''::3;1 LBr LBr LDBr LBl
TS Gycerin NC NC NC NC
TS+H2SO4 Glycerin NC NC NC NC
TS+H2SO4+AT Glycerin+Pbt* DBr Bl DBr Bl
TS+H2SO4+AT Pbt+Glycerin'' DBr Bl DBr Bl
TS Glycerin+Pbt* NC NC Br Bl
TS+H2SO4+AT PbtiQycerin" ::2.i Br Bl Br Bl
TS+H2SO4 Glycerin+Pbt" ::3:1 NC NC NC NC
TS+H2SO4 Pbt+Glycerin'' ::3:l NC LBr DY DBr
TS+H2SO4+AT Glycerin+Pbt' ::3:1 NC NC NC NC
TS+H2SO4+AT Pbt + Glycerin'' -.-J-.l DBr Bl DBr Bl
TS Soap NC NC NC NC
TS+H2SO4 Soap NC NC NC NC
TS+H2SO4+AT Soap+Pbt" Br LDBr Br Bl
TS+H2SO4+AT Pbt+Soap"* DBr DBr DBr Bl
TS Soap+Pbt* NC NC NC Bl
TS+H2SO4+AT Pbt:Soap' ::2:1 - - - -
TS+H2SO4 Soap+Pbt* ::3:1 NC NC NC NC
TS+H2SO4 Pbt+Soap" ::3:1 NC NC NC NC
TS+H2SO4+AT Soap+Pbt'::3:1 NC NC NC NC
TS+H2SO4+AT Pbt+Soap'' -.J-.l DBr DBr DBr Bl
43
Table 2.1 contd....
TS Gum NC NC NC NC
TS+H2SO4 Gum NC NC NC NC
TS+H2SO4 + AT Gum+^Pbt" NC NC Br Bl
TS+H2SO4 + AT Pbt+Gum" DBr Bl DBr Bl
TS Gum + Pbt" NC NC Br Bl
TS+H2SO4 + AT Pbt: Gum" :2:1 - - - -
TS+ H2SO4 Gum + Pbt* :3:1 NC NC NC NC
TS+H2SO4 Pbt + Gum*" : 3:1 LBr LBr DY Bl
TS+H2SO4 + AT Gum + Pbt" : 3:1 NC NC NC NC
TS+H2SO4 + AT Pbt + Gum" :3:1 DBr Bl DBr Bl
TS Paraffin oil NC NC NC NC
TS+H2SO4 Paraffin oil NC NC NC NC
TS+H2SO4 + AT Paraffin oil+Pbt' Br LBl Br Bl
TS+H2SO4 + AT Pbt+Paraffin oil** DBr LBl DBr Bl
TS Paraffin oil+Pbt* NC NC DY Bl
TS+H2SO4 + AT Pbt:Paraffin oil'' ::2:1 - - - -
TS+H2SO4 Paraffin oil+Pbt* :: 3:1 NC NC NC NC
TS+H2SO4 Pbt+Paraffin oil" ::3:1 NC NC VDY Bl
TS+H2SO4 + AT Paraffin oil+Pbt':: 3:1 NC NC NC NC
TS+H2SO4 + AT Pbt+Paraffinoil''::3:l Br LBl DBr Bl
TS Fevicol NC NC NC NC
TS+H2SO4 Fevicol NC NC NC NC
TS+H2SO4 + AT Fevicol+Pbt' LBr LBr LBr LBl
TS+H2SO4 + AT Pbt+Fevicol" DBr DBr LDBr LBl
TS Fevicol+Pbt* LBr LDBr Br LBl
TS+H2SO4 + AT Pbt:Fevicor ::2:1 - - - -
TS+H2SO4 Fevicol+Pbt* ::3:1 NC NC NC NC
TS+H2SO4 Pbt+Fevicol''::3:l NC VLBr DY Bl
TS+H2SO4+AT Fevicol+Pbt* ::3:1 NC NC NC NC
TS+H2SO4 + AT Pbt+Fevicol" ::3:1 DBr DBr LDBr LBl
TS Hydroxylamine hydrochloride NC NC NC NC
TS+H2SO4 Hydroxylamine hydrochloride NC NC NC NC
TS+H2SO4 + AT Hydroxylamine hydrochloride+Pbt* NC NC DBr Bl
44
Table 2.1 contd..
TS+H1SO4 + AT Pbt+Hydroxylamine hydrochloride'' DBr Bl DBr Bl
TS Hydroxylamine hydrochloride^-Pbt* DBr Bl DY-Br Bl
TS+H2SO4 + AT Pbt.Hydroxylamine hydrochloride" :;2:1
Br DBr Br DBr
TS+H2SO4 Hydroxylamine hydrochioride+Pbt" ::3:1
NC NC NC NC
TS+H2SO4 Pbt+Hydroxylamine hydrochloride*" ;:3:1
LDBr Bl DY Bl
TS+H2SO4 + AT Hydroxylamine hydrochloride+Pbt* ::3;1
NC NC NC NC
TS+H2SO4 + AT Pbt+Hydroxylamine hydrochloride'' :: 3.1
DBr Bl DBr Bl
TS Aluminium oxide acidic NC NC NC NC
TS+H2SO4 Aluminium oxide acidic NC NC NC NC
TS+H2SO4 + AT Aluminium oxide acidic+Pbt* LBr Br Br Bl
TS+H2SO4 + AT Pbt+Aluminium oxide acidic'' Br DBr DBr Bl
TS Aluminium oxide acidic+Pbt* NC NC DY Bl
TS+H2SO4 + AT Pbt: Aluminium oxide acidic° ::2:1 Bl LDBr Br LDBr
TS+H2SO4 Aluminium oxide acidic+Pbt* :: 3:1 NC NC NC NC
TS+H2SO4 Pbt+Aluminium oxide acidic*" ::3:l LBr Br DY DBr
TS+H2SO4 + AT Aluminium oxide acidic+Pbt* ::3:1 NC NC NC VLBr
TS+H2SO4 + AT Pbt+Aluminium oxide acidic'' ::3:1 Br DBr DBr Bl
TS Aluminium oxide basic NC NC NC NC
TS+H2SO4 Alununium oxide basic NC NC NC NC
TS+H2SO4 + AT Aluminium oxide basic+Pbt* Br DBr Br DBr
TS+H2SO4 + AT Pbt+Aluminium oxide basic'' DBr Bl DBr Bl
TS Aluminium oxide basic+Pbt* NC NC LDY Bl
TS+H2SO4 + AT PbtiAluminium oxide basic^::2:1 Bl LDBr Br LDBr
TS+H2SO4 Aluminium oxide basic + Pbt* ::3:1 NC NC NC NC
TS+H2SO4 Pbt+Aluminium oxide basic'' :; 3:1 NC NC NC LBr
TS+H2SO4 + AT Aluminium oxide basic+Pbt* :; 3:1 NC NC NC NC
TS+H2SO4 + AT Pbt+Aluminium oxide basic*" :. 3:1 DBr Bl DBr Bl
TS Potassium permanganate VDBr VDBr VDBr VDBr
TS+H2SO4 Potassium permanganate NC NC NC NC
TS+H2SO4 + AT Potassium permanganate+Pbt* Pr Pr PrBr PrBr
45
Table 2.1 contd....
TS+H2SO4 + AT Pbt+Potassium permanganate''
TS
TS+H2SO4 + AT
TS+H2SO4
TS+H2SO4
TS+H2SO4 + AT
Potassium permanganate+Pbt*
Pbt;Potassium permanganate' ::2:1
Potassium permanganate+Pbt* ::3:1
Pbt+Potassium permanganate''; :3:1
Potassium permanganate+Pbt* ::3.i
TS+H2SO4 + AT Pbt+potassium permanganate'':: 3:1
Gr VDBr Gr Gr-DBr
Gr VDBr Gr Gr-DBr
GrBr VDBr GrBr VDBr
Pr Pr PrBr PrBr
Gr VDBr Gr VDBr
Pr Pr PrBr PrBr
Gr VDBr Gr VDBr
a= compound I was added and then compound 11 was added into the test tube, b=compound 11 was added and then compound I was added into the test tube, c=admixture of I and II was added into the test tube, Bl=black, Br=brown, D=dark, ET=elevated temperature (55±5°C), Gr=green, L=light, NC=no colour, Pr=purple, R=red, RT=room temperature (25±3°C), V=very, Y=yellow and AT=brief heating.
46
Table2.2:Lower limit of detection in water of some dithiocarbamates using different reagents and technologies
Reagent Lower limit of detection (nKg)
Solution state Vapour state
Solution state U-tube Indicator paper
NaDDC Mancozeb NaDDC Mancozeb NaDDC Mancozeb
Pbt: Formaldehyde 100 7.5 100 75 100 75
Pbt: Surcose 1000 75 1000 75 1000 75
Pbt: Glucose 100 75 - - - -
Pbt: Starch 100 7.5 1000 750 1000 75
Pbt: Ascorbic acid 100 75 1000 75 1000 750
Pbt: Dimethylamine 100 75 - 750 - 75
Pbt: Silica gel 1000 75 - 750 - 75
Pbt: Glycerin 100 7.5 100 75 100 75
Pbt: Soap 1000 75 - - - -
Pbt: Gum 100 75 - - - -
Pbt: Paraffin oil 1000 75 1000 75 - 750
Pbt: Fevicol 100 75 - - - -
Pbt: Hydroxylamine hydrochloride
100 7.5 100 75 100 75
Pbt: Aluminium oxide acidic
100 7.5 1000 75 1000 750
Pbt: Aluminium oxide basic
100 7.5 71000 75 1000 750
Pbt: Potassium 1000 750 - - - -permanganate
Zineb Propineb Zineb Propineb Zineb Propineb
Pbt: Formaldehyde 7.5 7.0 75 70 75 70
Pbt: Glycerin 7.5 7.0 75 70 75 70
Pbt: Hydroxylamine hydrochloride
7.5 7.0 75 70 75 70
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53
