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Users of this Test Guideline should consult the Preface,
in particular paragraphs 3, 4, 7 and 8.
111Adopted:
12 May 1981OECD GUIDELINE FOR TESTING OF CHEMICALS
"Hydrolysis as a Function of pH"
1. I N T R O D U C T O R Y I N F O R M A T I O N
P r e r e q u i s i t e s
Water solubility
Suitable analytical method
G u i d a n c e i n f o r m a t i o n
Vapour pressure curve
Q u a l i f y i n g s t a t e m e n t s
Pure and commercial grade substances can be tested with the method described here, butthe potential effect of impurities on the results should be considered.
This Test Guideline applies only to water soluble compounds. There is uncertainty in
extrapolating high temperature results to environmentally relevant temperatures as a change inreaction mechanism could occur.
S t a n d a r d d o c u m e n t s
This Test Guideline is based on methods given in the references listed in Section 4 andon the Preliminary Draft Guidance for Premanufacture Notification EPA, August 18, 1978.
2. M E T H O D
A. INTRODUCTION, PURPOSE, SCOPE, RELEVANCE, APPLICATIONAND LIMITS OF TEST
The testing of substances for hydrolysis is relevant to their persistence. Hydrolysis is oneof the most common reactions controlling abiotic degradation and is therefore one of the maindegradation paths of substances in the environment.
A procedure to determine hydrolysis rates is important also in indicating whether othertesting should be carried out on a parent compound or on its hydrolysis products. It is thedegradation products that are crucial.
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111page 3"Hydrolysis as a Function of pH"
R e f e r e n c e s u b s t a n c e s
Aspirin Diazinon
These substances need not be employed in all cases when investigating a new substance.They are provided primarily so that calibration of the method may be performed from time totime and to offer the chance to compare the results when another method is applied.
The results of the OECD/EEC-Laboratory Intercomparison Testing are included inAnnex 2.
P r i n c i p l e o f t h e t e s t m e t h o d
In the environment, chemicals usually occur in dilute solution, which means that wateris present in large excess, and, therefore, that the concentration of water remains essentiallyconstant during hydrolysis. Hence, the kinetics of hydrolysis are generally pseudo-first orderat fixed pH and temperature.
The hydrolysis reaction may be influenced by acidic or basic species H30+(H+) and OH-,
in which case it is referred to as specific acid or specific base catalysis.
The concentration of the test substance is determined as a function of time. Thelogarithms of the concentrations are plotted against time and the slope of the resulting straightline (assuming first-order or pseudo-first order behaviour) gives the rate constant from theformula.
kobs= - slope . 2.303 (if log10 is used).
When it is not practicable to directly determine a rate constant for a particulartemperature, it is usually possible to estimate the constant through the use of the Arrheniusrelationship in which the logarithm of rate constants at other temperatures is plotted against thereciprocal of the absolute temperature (K).
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Q u a l i t y c r i t e r i a
Repeatability
Mabey and Mill (2) report that measurements of hydrolysis rate constants on 13 classesof organic structures can be of high precision, often with less than 2 per cent standard deviation.The rate constants for one pH and one temperature should be determined in duplicate with adeviation of less than 2.5 per cent unless unusual circumstances (e.g. analytical difficulties)prevent achieving this and then the details of these circumstances should be reported. The
repeatability can be improved by an improved control of the sensitive parameters, in particularpH and oxygen.
Sensitivity
Most hydrolysis reactions follow apparent first order reaction rates and, therefore, half-lives are independent of concentration (equation 3). This usually permits the application oflaboratory results determined at 10-2 - 10-3M to environmental conditions (10-6M) (2).
Specificity
Mabey and Mill (2) report several examples of good agreement between rates of
hydrolysis measured in both pure and natural waters for a variety of chemicals providing bothpH and temperature had been measured.
B. DESCRIPTION OF THE TEST PROCEDURE
The overall scheme is summarised in Figure 1, below.
P r e p a r a t i o n s
Materials
Buffer solutions
The hydrolysis test should be performed at four different values:
(1) at pH 1.2 (if physiologically important)(2) at pH 4.0(3) at pH 7.0(4) at pH 9.0
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Figure 1 HYDROLYSIS SCHEME
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For this purpose, 0.05 M sterile buffer solutions should be prepared using reagent gradechemicals and distilled, sterile water. Some useful buffer systems are presented in Annex 1,based upon the analytical requirements for the chemical being tested. It should be noted thatthe buffer system used may influence the rate of hydrolysis and where this is observed analternate buffer system should be employed. Mabey and Mill recommend the use of borate oracetate buffers instead of phosphate (2).
The pH of each buffer solution must be checked with a calibrated pH meter at therequired temperature to a precision of at least 0.1.
Test solutions
The chemical substance should be dissolved in distilled, sterile water with sterile buffermedium added to it.
The concentrations should not exceed the lesser of 0.01 M or half the saturationconcentration*, and the purest available form of the substance should be employed in makingup the solutions. The use of mixed solvents is recommended only in case of low water solublesubstances the amount of solvent should be less than 1 per cent, and the solvent should notinterfere with the hydrolysis process.
Glassware
All glassware, which must be inert in the pH range studied, should be sterilised.Stoppered volumetric flasks (no grease) should be used for carrying out the hydrolysis reactions.If the chemical or buffer system is volatile, or if the test is being conducted at elevatedtemperatures, sealed or septum-closed tubes are preferred and head space should be avoided.
Analytical method
The analytical method will be determined by the nature of the substance being tested.It must be sufficiently sensitive and specific to allow determination of the different species atthe test solution concentrations and may well consist of some combination of:
pH electrodes UV-visible spectrophotometry conductivity
* Test Guideline Water Solubility 105
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gas chromatography high pressure liquid chromatography extration and formation of derivative(s) and determination by a suitable analytical method.
T e s t c o n d i t i o n s
Temperature
For extrapolation purposes, it is important to maintain the temperature of the
determinations to at least 0.1C.
An appropriate constant temperature bath should be employed. If the hydrolyticbehaviour of the substance is unknown, a preliminary test at 50C is required. For tests beyondthis preliminary stage data for temperatures in the range 0 - 40C are sought. They may beobtained by measurement at two temperatures in this range or by extrapolation from threehigher temperatures. In any event, the determinations should be done at temperatures differingfrom each other by at least 10C.
Light and oxygen
All of the hydrolysis reactions should be carried out using any suitable method to avoid
photolytic effects. All suitable measures should be taken to exclude oxygen (e.g. by bubblingnitrogen or argon for 5 minutes before preparation of the solution).
P e r f o r m a n c e o f t h e t e s t
(1) Preliminary test. A preliminary test should be performed on the substance at 50 0.1C ateach of pH 4.0, 7.0 and 9.0. If less than 10 per cent of the reaction is observed after 5 days(t1/2> 1 year), the chemical is considered hydrolytically stable and no additional testing isrequired. If the substance is known to be unstable at environmentally relevant temperatures, thepreliminary test is not required. The analytical method must be sufficiently precise and sensitiveto detect a reduction of 10 per cent in the initial concentration.
(2) Hydrolysis of unstable substances. If the substance is unstable as defined by the preliminarytest (above), the test procedure is to be as follows:
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The buffered test solutions of the substance should be thermostated at the selectedtemperatures. To test for first-order behaviour, each reaction solution should be analysed in timeintervals which provide a minimum of six spaced data points normally between 20 per cent and70 per cent of hydrolysis of that test chemical. The reaction should be examined at three (4, 7,9) pHs at each of the selected temperatures with replication at one of them (the middletemperature in the case of elevated temperature determinations).
(3) Hydrolysis at pH 1.2. The above test for a hydrolytically unstable compound should alsobe carried out at pH 1.2 employing a single, physiologically significant temperature (37C).
3. D A T A A N D R E P O R T I N G
T r e a t m e n t o f r e s u l t s
Confirmation of first order kinetics: The data obtained should be plotted at log10 Ctversus t and the reaction rate constant kobscalculated by regression analysis or from the slope:
kobs= 2.303 . slope (5)
I n t e r p r e t a t i o n o f r e s u l t s
If the data do not fall on a straight line, the reaction is not first order, and the data mustbe analysed by methods beyond the scope of this test principle.
T e s t r e p o r t
The test report should include information on
sample purity
any results appropriate to the procedure employing reference substances
detailed test procedure including the temperature, pH and buffer for each set of experiments
detailed analytical method used for the tested substance, including detailed method ofextraction and recovery data if an extraction method is used to separate the chemical from theaqueous phase
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all concentration-time data points for reactions which were observed to originate a non-linear log concentration-time plot
possibility of acid or base catalysis
A sample reporting form is found in Annex 3.
4 . L I T E R A T U R E
01. I.M. Kolthoff and H.A. Laitinen,pH and Electro-Ti trations, Second Ed, John Wiley &Sons, N.Y., pp. 34-36 (1941).
02. W. Mabey and T. Mill, "Critical Review of Hydrolysis of Organic Compounds in WaterUnder Environmental Conditions," J. Phys. Chem. Ref. Data 7 (2), 383-415 (1978).
03. H.M. Gomaa, I.H. Suffet, S.D. Faust, "Kinetics of Hydrolysis of Diazoxon", ResidueReviews 29: 171 (1969).
04. OECD Document A80.30, Summary of OECD-EEC Laboratory Intercomparison TestingProgramme, Part 2, Umweltbundesamt, Berlin, May 1980.
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5. A N N E X
1. BUFFER MIXTURES (1)
A. CLARK AND LUBS
BUFFER MIXTURES OF CLARK AND LUBS*0.2 N HC1 and 0.2 N KC1 at 20
Composition PH47.5 ml. HC1 + 25 ml. KC1 dil. to 100 ml . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.032.25 ml. HC1 + 25 ml. KC1 dil. to 100 ml . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.220.75 ml. HC1 + 25 ml. KC1 dil. to 100 ml . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.413.15 ml. HC1 + 25 ml. KC1 dil. to 100 ml . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.608.3 ml. HC1 + 25 ml. KC1 dil. to 100 ml . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.805.3 ml. HC1 + 25 ml. KC1 dil. to 100 ml . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.003.35 ml. HC1 + 25 ml. KC1 dil. to 100 ml . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2
0.1 M potassium biphthalate + 0.1 N HC1 at 20
46.70 ml. 0.1 N HC1 + 50 ml. biphthalate to 100 ml . . . . . . . . . . . . . . . . . . . . . . 2.239.60 ml. 0.1 N HC1 + 50 ml. biphthalate to 100 ml . . . . . . . . . . . . . . . . . . . . . . 2.432.95 ml. 0.1 N HC1 + 50 ml. biphthalate to 100 ml . . . . . . . . . . . . . . . . . . . . . . 2.626.42 ml. 0.1 N HC1 + 50 ml. biphthalate to 100 ml . . . . . . . . . . . . . . . . . . . . . . 2.820.32 ml. 0.1 N HC1 + 50 ml. biphthalate to 100 ml . . . . . . . . . . . . . . . . . . . . . . 3.014.70 ml. 0.1 N HC1 + 50 ml. biphthalate to 100 ml . . . . . . . . . . . . . . . . . . . . . . 3.209.90 ml. 0.1 N HC1 + 50 ml. biphthalate to 100 ml . . . . . . . . . . . . . . . . . . . . . . 3.405.97 ml. 0.1 N HC1 + 50 ml. biphthalate to 100 ml . . . . . . . . . . . . . . . . . . . . . . 3.602.63 ml. 0.1 N HC1 + 50 ml. biphthalate to 100 ml . . . . . . . . . . . . . . . . . . . . . . 3.8
0.1 M potassium biphthalate + 0.1 N NaOH at 20
00.40 ml. 0.1 N NaOH + 50 ml. biphthalate to 100 ml . . . . . . . . . . . . . . . . . . . . . 4.003.70 ml. 0.1 N NaOH + 50 ml. piphthalate to 100 ml . . . . . . . . . . . . . . . . . . . . . 4.207.50 ml. 0.1 N NaOH + 50 ml. biphthalate to 100 ml . . . . . . . . . . . . . . . . . . . . 4.412.15 ml. 0.1 N NaOH + 50 ml. biphthalate to 100 ml . . . . . . . . . . . . . . . . . . . . . 4.617.70 ml. 0.1 N NaOH + 50 ml. biphthalate to 100 ml . . . . . . . . . . . . . . . . . . . . . 4.8
* The pH values reported in these tables have been calculated from the potential measurements using Srensen'sstandard equations (1909). The corresponding pH values are 0.04 unit higher than the tabulated values.
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Composition pH
0.1 M potassium biphthalate + 0.1 NaOH at 20
23.85 ml. 0.1 N NaOH + 50 ml. biphthalate to 100 ml . . . . . . . . . . . . . . . . . . . . . 5.029.95 ml. 0.1 N NaOH + 50 ml. biphthalate to 100 ml . . . . . . . . . . . . . . . . . . . . . 5.235.45 ml. 0.1 N NaOH + 50 ml. biphthalate to 100 ml . . . . . . . . . . . . . . . . . . . . . 5 439.85 ml. 0.1 N NaOH + 50 ml. biphthalate to 100 ml . . . . . . . . . . . . . . . . . . . . . 5.643.00 ml. 0.1 N NaOH + 50 ml. biphthalate to 100 ml . . . . . . . . . . . . . . . . . . . . . 5.8
45.45 ml. 0.1 N NaOH + 50 ml. biphthalate to 100 ml . . . . . . . . . . . . . . . . . . . . . 6.0
0.1 M monopotassium phosphate + 0.1 N NaOH at 20
05.70 ml. 0.1 N NaOH + 50 ml. phosphate to 100 ml . . . . . . . . . . . . . . . . . . . . . . 6.008.60 ml. 0.1 N NaOH + 50 ml. phosphate to 100 ml . . . . . . . . . . . . . . . . . . . . . . 6.212.60 ml. 0.1 N NaOH + 50 ml. phosphate to 100 ml . . . . . . . . . . . . . . . . . . . . . . 6.417.80 ml. 0.1 N NaOH + 50 ml. phosphate to 100 ml . . . . . . . . . . . . . . . . . . . . . . 6.623.45 ml. 0.1 N NaOH + 50 ml. phosphate to 100 ml . . . . . . . . . . . . . . . . . . . . . . 6.829.63 ml. 0.1 N NaOH + 50 ml. phosphate to 100 ml . . . . . . . . . . . . . . . . . . . . . . 7.035.00 ml. 0.1 N NaOH + 50 ml. phosphate to 100 ml . . . . . . . . . . . . . . . . . . . . . . 7.239.50 ml. 0.1 N NaOH + 50 ml. phosphate to 100 ml . . . . . . . . . . . . . . . . . . . . . . 7.4
42.80 ml. 0.1 N NaOH + 50 ml. phosphate to 100 ml . . . . . . . . . . . . . . . . . . . . . . 7.645.20 ml. 0.1 N NaOH + 50 ml. phosphate to 100 ml . . . . . . . . . . . . . . . . . . . . . . 7.846.80 ml. 0.1 N NaOH + 50 ml phosphate to 100 ml . . . . . . . . . . . . . . . . . . . . . . 8.0
0.1 M H2B02in 0.1 M KC1 + 0.1 N NaOH at 20
02.61 ml. 0.1 N NaOH + 50 ml. boric acid to 100 ml . . . . . . . . . . . . . . . . . . . . . 7.803.97 ml. 0.1 N NaOH + 50 ml. boric acid to 100 ml . . . . . . . . . . . . . . . . . . . . . 8.005.90 ml. 0.1 N NaOH + 50 ml. boric acid to 100 ml . . . . . . . . . . . . . . . . . . . . . 8.208.50 ml. 0.1 N NaOH + 50 ml. boric acid to 100 ml . . . . . . . . . . . . . . . . . . . . . 8.412.00 ml. 0.1 N NaOH + 50 ml. boric acid to 100 ml . . . . . . . . . . . . . . . . . . . . . 8.616.30 ml. 0.1 N NaOH + 50 ml. boric acid to 100 ml . . . . . . . . . . . . . . . . . . . . . 8.821.30 ml. 0.1 N NaOH + 50 ml. boric acid to 100 ml . . . . . . . . . . . . . . . . . . . . . 9.026.70 ml. 0.1 N NaOH + 50 ml. boric acid to 100 ml . . . . . . . . . . . . . . . . . . . . . 9.232.00 ml. 0.1 N NaOH + 50 ml. boric acid to 100 ml . . . . . . . . . . . . . . . . . . . . . 9.436.85 ml. 0.1 N NaOH + 50 ml. boric acid to 100 ml . . . . . . . . . . . . . . . . . . . . . 9.640.80 ml. 0.1 N NaOH + 50 ml. boric acid to 100 ml . . . . . . . . . . . . . . . . . . . . . 9.843.90 ml. 0.1 N NaOH + 50 ml. boric acid to 100 ml . . . . . . . . . . . . . . . . . . . . 10.0
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B. KOLTHOFF AND VLEESCHHOUWER
CITRATE BUFFERS OF KOLTHOFF AND VLEESCHHOUWER
0.1 M monopotassium citrate and 0.1 N HC1 at 18(Add tiny crystal of thymol or a few milligrams of mercury to prevent growth of molds)
Composition pH
49.7 ml. 0.1 N HC1 + 50 ml. citrate to 100 ml . . . . . . . . . . . . . . . . . . . . . . . . . 2.243.4 ml. 0.1 N HC1 + 50 ml. citrate to 100 ml . . . . . . . . . . . . . . . . . . . . . . . . . 2.436.8 ml. 0.1 N HC1 + 50 ml. citrate to 100 ml . . . . . . . . . . . . . . . . . . . . . . . . . 2.630.2 ml. 0.1 N HC1 + 50 ml. citrate to 100 ml . . . . . . . . . . . . . . . . . . . . . . . . . 2.823.6 ml. 0.1 N HC1 + 50 ml. citrate to 100 ml . . . . . . . . . . . . . . . . . . . . . . . . . 3.017.2 ml. 0.1 N HC1 + 50 ml. citrate to 100 ml . . . . . . . . . . . . . . . . . . . . . . . . . 3.210.7 ml. 0.1 N HC1 + 50 ml. citrate to 100 ml . . . . . . . . . . . . . . . . . . . . . . . . . 3.404.2 ml. 0.1 N HC1 + 50 ml. citrate to 100 ml . . . . . . . . . . . . . . . . . . . . . . . . . 3.6
0.1 M monopotassium citrate and 0.1 N NaOH at 18(Add tiny crystal of thymol or a few milligrams of mercuric iodide to prevent growth of molds)
02.0 ml. 0.1 N NaOH + 50 ml. citrate to 100 ml . . . . . . . . . . . . . . . . . . . . . . . . 3.809.0 ml. 0.1 N NaOH + 50 ml. citrate to 100 ml . . . . . . . . . . . . . . . . . . . . . . . . 4.016.3 ml. 0.1 N NaOH + 50 ml. citrate to 100 ml . . . . . . . . . . . . . . . . . . . . . . . . 4.223.7 ml. 0.1 N NaOH + 50 ml. citrate to 100 ml . . . . . . . . . . . . . . . . . . . . . . . . 4.431.5 ml. 0.1 N NaOH + 50 ml. citrate to 100 ml . . . . . . . . . . . . . . . . . . . . . . . . 4.639.2 ml. 0.1 N NaOH + 50 ml. citrate to 100 ml . . . . . . . . . . . . . . . . . . . . . . . . 4.846.7 ml. 0.1 N NaOH + 50 ml. citrate to 100 ml . . . . . . . . . . . . . . . . . . . . . . . . 5.054.2 ml. 0.1 N NaOH + 50 ml. citrate to 100 ml . . . . . . . . . . . . . . . . . . . . . . . . 5.261.0 ml. 0.1 N NaOH + 50 ml. citrate to 100 ml . . . . . . . . . . . . . . . . . . . . . . . . 5.468.0 ml. 0.1 N NaOH + 50 ml. citrate to 100 ml . . . . . . . . . . . . . . . . . . . . . . . . 5.674.4 ml. 0.1 N NaOH + 50 ml. citrate to 100 ml . . . . . . . . . . . . . . . . . . . . . . . . 5.8
81.2 ml. 0.1 N NaOH + 50 ml. citrate to 100 ml . . . . . . . . . . . . . . . . . . . . . . . . 6.0
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C. SRENSEN
BORATE MIXTURES OF SRENSEN
0.05 M borax + 0.1 N HC1
Composition Srensen
18
Walbum, pH at
ml. Borax ml. HCl 10 40 70
5.255.505.756.006.507.007.508.008.50
9.009.5010.00
4.754.504.254.003.503.002.502.001.50
1.000.500.00
7.627.948.148.298.518.088.808.919.01
9.099.179.24
7.647.988.178.328.548.728.848.969.06
9.149.229.30
7.557.868.068.198.408.568.678.778.86
8.949.019.08
7.477.767.958.088.288.408.508.598.67
8.748.808.86
0.05 M borax + 0.1 N NaOH
10.09.08.07.06.0
0.01.02.03.04.0
9.249.369.509.689.97
9.309.429.579.76
10.06
9.089.189.309.449.67
8.868.949.029.129.28
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2. RATE CONSTANTS AND HALF-LIVES O F SOM E SELECTED
CHEMICALS
A. REPORTED LITERATURE VALUES ON ASPIRIN AND DIAZINON
The following literature values have been reported:
Diazinon (0, 0-ondiethyl-0- (6-methyl-2-isopropyl-4-pyrimidinyl phosphrothioate) fromH.M. Gomma, I.H. Suffet, S.D. Faust, Residue Reviews 29, 171 (1969):
pH
10.43 0.061 (310) 0.13 (150) 0.41 (48) 15 (12) K [105sec-1] (t1/2 [h])
9.0 0.0059 (3300) K [105sec-1] (t1/2 [h])
7.4 0.00043 (4400) K [105sec-1] (t1/2 [h])
5.0 0.026 (740) K [105sec-1] (t1/2 [h])
3.1 0.75 (260) 1.6 (120) 6.6 (29) 25 (7.8) K [105sec-1] (t1/2 [h])
10C 20C 40C 60C Temperature
Aspirin (2-acetylsalicylic acid) from L.J. Edwards, Trans. Faraday Soc. 723-735 (1950)
0.065 (300) 0.15 (130) 0.13 (150) 0.37 (52) 16 (1.2) K [105 sec-1] (t1/2 [h])
pH 3.5 5.0 7.4 9.5 11.3
at 17C
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B. RESULTS OF OECD-EEC LABORATORY INTERCOMPARISONTESTING PROGRAMME, PART 2 (4)
Aspirin Diazinon
In some cases the results presented here have a variability which exceeds what is called
for in the Test Guideline. This may particularly be the result of the use of different buffers inthe test systems and the influence of oxygen.
The Expert Group presents these results however, as they have been obtained using theTest Guidelines in the OECD/EEC Intercomparison Testing Programme, Part II. The firstGuideline as presented here has been modified in the light of these results.
Summary Results of "Hydrolysis as a function of pH"
Reaction Rate Constant in 105. 1/s
Substance: Aspirin
pH-value temperaturein C
mean value standarddeviation
coefficientof variation
(%)
range n of results
1.2 35-40 1.013 1.278 126.2 0.109 to 1.916 2
3.0 204060
0.0800.556
-
0.0560.112
-
70.320.1
-
0.040 to 0.1190.477 to 0.635
-
22-
7.0 204060
0.2051.339
-
0.0330.004
-
15.90.3
-
0.182 to 0.2281.336 to 1.341
-
22-
9.0 204060
0.3090.953
-
0.1600.006
-
51.70.6
-
0.196 to 0.4420.949 to 0.957
-
22-
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Summary Results of "Hydrolysis as a Function of pH"
Half Life Time in Hours (t1/2)
Substance: Aspirin
pH-value temperaturein C
mean value standarddeviation
coefficientof variation
(%)
range n of results
1.2 35-40 93.71 118.3 126 10.05 to177.36
2
3.0 204060
319.735.4
-
222.57.1
-
7020-
162.3 to 477.030.3 to 40.4
-
22 (1 lab)
-
7.0 204060
95.114.4
-
15.10.0
-
20--
84.4 to 105.814.4 to 14.4
-
22 (1 lab)
-
9.0 204060
72.120.2
-
37.30.1
-
500.0-
45.7 to 98.520.1 to 20.3
-
22 (1 lab)
-
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Summary Results of "Hydrolysis as a Function of pH"Reaction Rate Constant in 105.1/sSubstance: Diazinon
pH-value temperaturein C
meanvalue
standarddeviation
coefficientof variation
(%)
range n of results
1.2 35-40 30.36 8.10 27.0 21.40 to 38.46 4
3.0 20405060
2.8669.0385.77
36.085
0.8252.4474.27
11.088
28.827.174.030.7
1.675 to 3.8415.708 to 14.165
0.86 to 8.5825.535 to 51.449
711 (10 labs)3 (2 labs)
6
7.0 20405060
0.9330.2310.2001.638
1.7960.2940.0233.154
192.4127.311.3
192.6
0.005 to 3.6260.042 to 0.8950.184 to 0.2160.303 to 9.413
482
8 (7 labs)
9.0 20405060
1.1032.5680.2922.801
2.1136.9000.0344.125
191.6268.711.6
147.3
0.007 to 4.2710.064 to 20.9550.268 to 0.3160.241 to 12.604
492
8 (7 labs)
Summary Results of "Hydrolysis as a Function of pH"Half Life Time in Hours (t1/2)Substance: Diazinon
pH-value temperaturein C
meanvalue
standarddeviation
coefficientof variation
(%)
range n of results
1.2 35-40 0.672 0.187 27.9 0.501 to 0.900 4
3.0 20405060
7.272.259.000.57
2.400.57
11.530.17
3325
12829
5.0 to 11.51.4 to 3.3
2.24 to 22.310.37 to 0.75
711 (10 labs)3 (2 labs)
6
7.0 20405060
1707.75215.1697.0738.63
1875.18166.1210.9720.98
110771154
5.3 to 3660.921.5 to 460.7
89.31 to 104.832.0 to 63.5
482
8 (7 labs)
9.0 20405060
1150.75124.3866.4025.13
1335.58102.45
7.7425.67
1168212
102
4.5 to 2840.50.9 to 298.7
60.92 to 71.871.5 to 79.8
492
8 (7 labs)
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111page 18 "Hydrolysis as a Function of pH"
C. FURTHER RESULTS OF OECD-EEC LABORATORYINTERCOMPARISON TESTING PROGRAMME (4)
Three other compounds were similarly tested in this programme and the results arepresented below Atrazine Diethyl-hexylphthalate Ethylacetate
Summary Results of "Hydrolysis as a Function of pH"Reaction Rate Constant in 105. 1/sSubstance: Atrazine
pH-value temperaturein C
meanvalue
standarddeviation
coefficient ofvariation (%)
range n of results
1.2 35-40 0.546 0.416 76.3 0.076 to 0.948 4
3.0 204060
0.0140.1400.808
0.0080.0820.397
56.858.449.1
0.005 to 0.0200.028 to 0.2220.282 to 1.283
365
7.0 204060
-0.009-
-0.011-
-124.8
-
-0.001 to 0.016
-
22-
9.0 204060
0.0130.008-
0.0160.010-
130.1123.7
-
0.001 to 0.0240.001 to 0.015
-
-2-
Reaction Rate Constant in 105. 1/sSummary Results of "Hydrolysis as a Function of pH"Half Life Time in Hours (t1/2)Substance: Atrazine
pH-value temperaturein C meanvalue standarddeviation coefficient ofvariation (%) range n of results
1.2 35-40 54.76 44.36 81.0 20.3 to 115.35 4
3.0 204060
1867.88240.5031.42
1446.58239.6121.51
77.099.669.0
980.7 to 3537.14111.71 to 696.79
15.0 to 68.3
365
7.0 204060
-9000.15
-
-11033.77
-
-123.0
-
-1198.1 to 16802.2
-
22-
9.0 2040
60
17921.058005.35
-
24188.219539.51
-
135.0119.0
-
817.4 to 35024.71259.9 to 14750.8
-
22
-
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111page 19"Hydrolysis as a Function of pH"
Summary Results of "Hydrolysis as a Function of pH"Reaction Rate Constant in 105. 1/sSubstance: DOP
pH-value temperaturein C
meanvalue
standarddeviation
coefficient ofvariation (%)
range n of results
1.2 35-40 - - - - -
3.0 20
4060
0.048
0.1660.084
0.051
0.2020.022
107.8
121.826.3
0.009 to 0.106
0.023 to 0.3090.068 to 0.099
3
22
7.0 204060
0.073(1.627)(0.092)
0.064--
88.8--
0.027 to 0.118--
211
9.0 204060
0.040(0.126)-
0.047--
116.7--
0.007 to 0.073--
21-
Summary Results of "Hydrolysis as a Function of pH"Half Life Time in Hours (t1/2)
Substance: DOP
pH-value temperaturein C
meanvalue
standarddeviation
coefficient ofvariation (%)
range n of results
1.2 35-40 - - - - -
3.0 204060
990.20452.56239.33
996.32551.9863.75
10112227
182.4 to 2103.562.25 to 842.86194.25 to 284.41
322
7.0 204060
440.30(11.83)
(208.19)
391.35--
89--
163.57 to 717.02--
211
9.0 204060
1606.74(152.53)
-
1898.79--
118--
265.51 to 2947.97--
21-
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111page 20 "Hydrolysis as a Function of pH"
Summary Results of "Hydrolysis as a Function of pH"Reaction Rate Constant in 105.1/sSubstance: Ethylacetate
pH-value temperaturein C
meanvalue
standarddeviation
coefficient ofvariation (%)
range n of results
1.2 35-40 - - - - 1
3.0 20
4060
(0.0012)
(0.012)(0.355)
-
--
-
--
-
--
1
11
7.0 204060
(0.003)(0.008)(0.137)
---
---
---
111
9.0 204060
(0.063)(0.153)(1.547)
---
---
---
111
Summary Results of "Hydrolysis as a Function of pH"Half Life Time in Hours (t1/2)
Substance: Ethylacetate
pH-value temperaturein C
meanvalue
standarddeviation
coefficient ofvariation (%)
range n of results
1.2 35-40 - - - - -
3.0 204060
(1656)(1612.85)
(54.30)
---
---
---
111
7.0 204060
(7553.1)(2511.81)(140.38)
---
---
---
111
9.0 204060
(305.55)(125.71)(12.44)
---
---
---
111
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111page 21"Hydrolysis as a Function of pH"
3. SUGGESTED FORM TO REPORT DATA
Laboratory:Test substance:Date:
Test Protocol
A. PRELIMINARY TEST
yes no
buffer systems used:
pH 4.0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .pH 7.0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .pH 9.0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
pHapprox. saturationconcentration[mole/l]
4.0 7.0 9.0
Co[mole/1](start conc.)
Ct[mole/1](final conc. aftert days; tmax= 5
t
at 50 0.1C
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111page 22 "Hydrolysis as a Function of pH"
B. DETERMINATION
T e s t s u b s t a n c e
Separate runs at pH 4.0, pH 7.0, and pH 9.0 at the chosen temperature(s) with replicationat one of these (the middle temperature in the case of determination at elevated temperatures).
pH 4.0
buffer solution used: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .temperature: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .approximate saturation concentration: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
t [ ] 0
Ct [mole/1]
log Ct
pH 7.0
buffer solution used: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .temperature: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .approximate saturation concentration: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
t [ ] 0
Ct [mole/1]
log Ct
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111page 23"Hydrolysis as a Function of pH"
pH 9.0
buffer solution used: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .temperature: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .approximate saturation concentration: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
t [ ] 0
Ct [mole/1]
log Ct
H y d r o l y s i s a t p H 1 - 2
buffer solution used: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .pH: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .temperature: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .approximate saturation concentration: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
t [ ] 0
Ct [mole/1]
log Ct
F i n a l d a t a
pH temperaturein C
startconcentrationCoin mole/l
reaction rateconstant kobs inl/s x 105
half life t1/2in h
coefficient ofcorrelation r2
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111page 24 "Hydrolysis as a Function of pH"
C. REPORT ON TEST METHOD
D e t a i l e d d e s c r i p t i o n o f t h e e x p e r i m e n t a lc o n d i t i o n s , e . g .
for maintaining sterility to avoid photolytic effects
to exclude oxygen to prepare the test solution
(Please use another sheet of paper.)
A n a l y t i c a l c o m b i n a t i o n s u s e d
pH electrodes
UV-visible spectrophotometry
conductivity
gas chromatography
high pressure liquid chromatography
extraction and formation of derivative(s)
D e t a i l s o f t h e a n a l y t i c a l p e r f o r m a n c e
Type of apparatus: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Test conditions: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
D o y o u a s c e r t a i n t h e a c c u r a c y o f t h i s r e s u l t
i n a n y a d d i t i o n a l w a y ?Particular incidents:
Comments: