ARSENIC BIO-ACCESSIBILITY IN RICE BY ON-LINE...
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ARSENIC BIO-ACCESSIBILITY IN RICE BY ON-LINE LEACHING AND INDUCTIVELY COUPLED PLASMA MASS SPECTROMERY: FOCUS ON THE ARABIC REGION. Beauchemin Diane and Althobiti Randa [email protected] , [email protected] Department of Chemistry, Queen’s University, 90 Bader lane, Kingston, ON K7L 3N6, Canada \ . Irrigation of rice paddies with groundwater rich in arsenic 2 . . Paddy soils contaminated from industrial and mining activity 2 . Figure 1: Sampling sites. A- Results and discussion How does washing affect As level ? for better risk assessment, the rice was evaluated before and after washing step. washing rice has a significant impact on reducing the toxic element content. This chart shows the total concentration of As (n=5) found in rice from different countries. The total concentrations for unwashed and washed rice are in agreement according to a Student`s t-test at 95% confidence level. On-line continuous leaching procedure: 0.2 g of sample is wrapped in quartz wool and placed in a PTFE mini-column. The mini-column is enclosed using plugs of quartz wool. The artificial fluids (saliva, gastric and intestinal) are pumped sequentially through the mini-column while the released arsenic is monitored in real time by ICPMS². Batch procedure: 1 g of sample is placed in a 50-mL falcon tube with saliva, gastric and intestinal fluids added sequentially. Between each addition, the test tube is shaken for 10 min for saliva and 2 hours for other juices at 37 ◦ C, followed by centrifugation and collection of supernatants for later analysis². Verification of mass balance: The residue is digested using 2.5 mL HNO 3 , 0.5 mL H 2 O 2 and heated to 50 ◦ C for one hour. The final solution is diluted to 25 mL with DDW². B- Results and discussion 0 20 40 60 80 100 120 140 Bio-accessibility % sampling sites of rice Bio-accessibility percentage of As in unwashed samples residue % intestinal % gastric % saliva % 0 20 40 60 80 100 120 140 Bio-accessiblitiy % sampling sites of rice Bio- accessibility percentage of As in washed samples residue % intestinal % gastric % saliva % water % Figure 4: This chart shows the percentage of As leached by each reagent and in the residue for different types of unwashed rice (n=5). The majority of As was leached out by saliva followed by gastric and intestinal juices. Figure 5: The effect of washing is displayed in this chart (n=5). A portion of As is leached out by water prior of cooking. This step can contribute to reduce the toxicity of arsenic in the rice. C- Results and discussion (a) (b) (c) Iraqi rice was found to be the most contaminated with arsenic. Saliva leaches the highest proportion of bio- accessible arsenic. Washing is an essential step prior to rice cooking and consumption. Future work: Develop methods for the speciation analysis of the different leachates by IEC-ICP-MS. Perform the speciation analysis of the bio-accessible fraction from the different rice samples for realistic risk assessment. Conclusion and future work Saudi Arabia for financial support. NSERC for research funding. References : [1] A. Leufroy, L. Noël, D. Beauchemin, T. Guérin, Anal. Bioanal. Chem. 402 (2012) 2849–2859. [2] N. S. Horner, D. Beauchemin, Anal. Chim. Acta 717 (2012) 1–6. Acknowledgement and references The goal was to investigate the toxicity of arsenic in Arabic area rice, as well as, to assess the potential risk of environmental arsenic in Arabic area. The effect of washing rice prior to cooking was also assessed to verify if it could make rice safer for human consumption. Arsenic in high concentration can cause a variety of adverse health effects after acute and chronic exposures. Rice analysis is considered essential to ensure the safety for human health, and to produce good quality of food 1 . The concentration of As in rice is often high compared to other crops, with a large fraction present as inorganic arsenic. Yet, rice is a fundamental food in many cultures around the world with average consumption of 100-650 g/person/day. For realistic risk assessment, bio-availability (amount ending up in the blood stream) should ideally be measured. However, as it can only be smaller or equal to bio-accessibility (i.e. the portion dissolved in the gastro-intestinal tract), the latter can be measured instead with an in vitro method, using leaching conditions mimicking those in the human body 2 . Purpose of this study Background A total of 10 rice samples were collected from local markets in Saudi Arabia, such as to represent the Arabic region . They were divided into two groups: Raw rice as purchased from the market . Washed for 5 min and then cooked rice with 30 ml of doubly deionized water (DDW) to 5 g of rice and cooking for 15 min. Varian 820 MS inductively coupled plasma quadruple mass spectrometry. Concentric nebulizer fitted into a Scott double pass spray chamber. Collision-reaction interface to reduce the polyatomic ion interferences. Source of contamination Sample collection Experimental set up Figure 2: Sample introduction of Varian 820 MS. Parameters Optimal setting Ar plasma gas flow rate (L/min) 18 Ar auxiliary gas flow rate (L/min) 1.8 Ar nebulizer gas flow rate ( L/min) 0.99 Ar sheathing gas flow rate (L/min) 0.15 Sample uptake rate (mL/min) 0.8 H 2 CRI gas (mL/min) 80 Table 1: Optimal ICP-MS instrumental parameters for analysis of rice samples Figure 3: Summary of experimental procedure. Methodology Figure 6: Arsenic leaching profile by (a) saliva ; (b) gastric juice; (c) Intestinal juice. the result from the batch method are similar to those obtained using the on-line leaching method (n=5). however, the online leaching method also provide access to real time leaching data. leaching with saliva resulted in the largest peak followed by gastric and intestinal juices. 0 200 400 600 800 1000 1200 As concentration (ng/g) sampling sites of rice the effect of washing process on changing the As concentration in rice samples Wash water Full digestion washed Full digestion unwashed
Transcript of ARSENIC BIO-ACCESSIBILITY IN RICE BY ON-LINE...
ARSENIC BIO-ACCESSIBILITY IN RICE BY ON-LINE LEACHING AND INDUCTIVELY
COUPLED PLASMA MASS SPECTROMERY: FOCUS ON THE ARABIC REGION.
BeaucheminDiane and Althobiti Randa [email protected], [email protected]
Department of Chemistry, Queen’s University, 90 Bader lane, Kingston, ON K7L 3N6, Canada
\
.
Irrigation of
rice paddies
with
groundwater
rich in
arsenic2 ..
Paddy soils
contaminated
from
industrial and
mining
activity2.
Figure 1: Sampling sites.
A- Results and discussion
How does washing affect As level ?
for better risk assessment, the rice was evaluated
before and after washing step.
washing rice has a significant impact on reducing the
toxic element content.
This chart shows the total concentration of As (n=5)
found in rice from different countries. The total
concentrations for unwashed and washed rice are in
agreement according to a Student`s t-test at 95%
confidence level.
On-line continuous leaching procedure:
0.2 g of sample is wrapped in quartz wool and placed
in a PTFE mini-column. The mini-column is
enclosed using plugs of quartz wool. The artificial
fluids (saliva, gastric and intestinal) are pumped
sequentially through the mini-column while the
released arsenic is monitored in real time by ICPMS².
Batch procedure:
1 g of sample is placed in a 50-mL falcon tube with
saliva, gastric and intestinal fluids added sequentially.
Between each addition, the test tube is shaken for 10
min for saliva and 2 hours for other juices at 37 ◦C,
followed by centrifugation and collection of
supernatants for later analysis².
Verification of mass balance:
The residue is digested using 2.5 mL HNO3, 0.5 mL
H2O2 and heated to 50 ◦C for one hour. The final
solution is diluted to 25 mL with DDW².
B- Results and discussion
0
20
40
60
80
100
120
140
B
io-a
cces
sib
ilit
y %
sampling sites of rice
Bio-accessibility percentage of As in
unwashed samples
residue %
intestinal %
gastric %
saliva %
0
20
40
60
80
100
120
140
Bio
-acc
ess
iblit
iy %
sampling sites of rice
Bio- accessibility percentage of As in
washed samples
residue %
intestinal %
gastric %
saliva %
water %
Figure 4: This chart shows
the percentage of As leached
by each reagent and in the
residue for different types of
unwashed rice (n=5).
The majority of As was
leached out by saliva followed
by gastric and intestinal juices.
Figure 5: The effect of
washing is displayed in this
chart (n=5). A portion of As
is leached out by water
prior of cooking. This step
can contribute to reduce the
toxicity of arsenic in the
rice.
C- Results and discussion
(a) (b)
(c)
Iraqi rice was found to be the most contaminated
with arsenic.
Saliva leaches the highest proportion of bio-
accessible arsenic.
Washing is an essential step prior to rice cooking
and consumption.
Future work:
Develop methods for the speciation analysis of the
different leachates by IEC-ICP-MS.
Perform the speciation analysis of the bio-accessible
fraction from the different rice samples for realistic risk
assessment.
Conclusion and future work
Saudi Arabia for financial support.
NSERC for research funding. References :
[1] A. Leufroy, L. Noël, D. Beauchemin, T. Guérin, Anal. Bioanal.
Chem. 402 (2012) 2849–2859.
[2] N. S. Horner, D. Beauchemin, Anal. Chim. Acta 717 (2012) 1–6.
Acknowledgement and references
The goal was to investigate the toxicity of arsenic in Arabic
area rice, as well as, to assess the potential risk of
environmental arsenic in Arabic area. The effect of washing
rice prior to cooking was also assessed to verify if it could
make rice safer for human consumption.
Arsenic in high concentration can cause a variety of adverse
health effects after acute and chronic exposures. Rice analysis
is considered essential to ensure the safety for human health,
and to produce good quality of food1. The concentration of As
in rice is often high compared to other crops, with a large
fraction present as inorganic arsenic. Yet, rice is a
fundamental food in many cultures around the world with
average consumption of 100-650 g/person/day. For realistic
risk assessment, bio-availability (amount ending up in the
blood stream) should ideally be measured. However, as it can
only be smaller or equal to bio-accessibility (i.e. the portion
dissolved in the gastro-intestinal tract), the latter can be
measured instead with an in vitro method, using leaching
conditions mimicking those in the human body2.
Purpose of this study
Background
A total of 10 rice samples were collected from local
markets in Saudi Arabia, such as to represent the
Arabic region . They were divided into two groups:
Raw rice as purchased from the market .
Washed for 5 min and then cooked rice with 30 ml
of doubly deionized water (DDW) to 5 g of rice and
cooking for 15 min.
Varian 820 MS inductively coupled plasma quadruple mass spectrometry.
Concentric nebulizer fitted into a Scott double pass spray chamber.
Collision-reaction interface to reduce the polyatomic ion interferences.
Source of contamination
Sample collection
Experimental set up
Figure 2: Sample introduction of Varian 820 MS.
Parameters Optimal setting
Ar plasma gas flow rate (L/min) 18
Ar auxiliary gas flow rate (L/min) 1.8
Ar nebulizer gas flow rate ( L/min) 0.99
Ar sheathing gas flow rate (L/min) 0.15
Sample uptake rate (mL/min) 0.8
H2 CRI gas (mL/min) 80
Table 1: Optimal ICP-MS instrumental parameters for analysis
of rice samples
Figure 3: Summary of experimental procedure.
Methodology
Figure 6: Arsenic leaching profile by
(a) saliva ;
(b) gastric juice;
(c) Intestinal juice.
the result from the batch method are similar to those
obtained using the on-line leaching method (n=5).
however, the online leaching method also provide access to
real time leaching data.
leaching with saliva resulted in the largest peak followed by
gastric and intestinal juices.
0
200
400
600
800
1000
1200
As
con
cen
trat
ion
(n
g/g
)
sampling sites of rice
the effect of washing process on changing
the As concentration in rice samples
Wash water
Full digestion washed
Full digestion unwashed
