QUICK DETERMINATION OF ATRAZINE RESIDUES

IN FOODS

M. H. EL-SAEID* AND M. A. SALEH

BIOMARKERS & ENVIRONMENTAL TOXICOLOGY LAB. CHEMISTRY DEPT. TEXAS

SOUTHERN UNIVERSITY, HOUSTON, TEXAS

INTRODUCTION Atrazine herbicide commonly used in

agriculture. Using cause a residues in fruit and vegetables. Residues cause health problems. Residues need a quick extraction. Quick extraction by Supercritical Fluid

Extraction & Microwave Solvent Extraction {SFE & MSE.}.

Residues need a quick determination. Quick determination by Supercritical Fluid

Chromatography & Enzyme-Linked Immunosorbent Assay {SFC & ELISA}.

SFE & MSE has• Potential advantages than conventional

extraction. Methods.• Reduced time.• Superior recovery.• Reduction in solvent usage.• No cleanup.• Safe.• SFE can be coupled directly with SFC.• MSE has proven to be safe alternative to

conventional organic solvent extraction.• High ability as Food extraction

techniques.

SFC is

• separation techniques used critical points & carrier gases of CO2 .

• CO2 is a safe gas to use.

• Become increasingly apparent in last several years.

• Complements GC & HPLC, it can be analyze different molecular weights without drivatization.

• Increase the analysis speed.

• Wider range of detectors, polarity & sensitivity.• Can be coupled with SFE.

Enzyme Linked Immunosorbent Assay {ELISA} is

• An important environmental analysis method used to identify Atrazine in Water & Foods.

• The EnviroGard Triazine Plate Kit is a quantitative laboratory test for the detection of Atrazine residues in water and foods uses polyclonal antibodies which bind Atrazine-enzyme conjugate for a limited number of antibody binding sites. Antibodies that bind Atrazine are immobilized to the inside of the wells.

• EPA, FDA, AOAC and Codex methods.• Rapid (less than 45 minutes).• Inexpensive, portable & can be used to evaluate

many samples at the same time.• Simple & sensitive (0.02 to 5.0 ppb).• No solvent disposal.

AIM OF STUDY

Extract and determined Atrazine by high sensitive technique in short time.

Modify & Compare SFE and MSE as extraction methods.

Modify & Compare SFC and ELISA technique as a determination methods

MATERIALS Eleven types of food Samples

– Fruit juice ( Guava, Mango and fruit cocktail)– Frozen Vegetables ( Mixed, Molukhia, Artichoke,

Colocassia, Beans, and Okra) – Jam (Strawberry)

• Homogenized and divided in tow portion, one spiked and one as control

• Both portion were freeze-dried.• Stored at -20 °C. Atrazine standard obtained from Chemservice,

Inc.

Envirogard Triazine Plate Kit 72110 was obtained from Strategic Diagnostics Inc.

ATRAZINE EXTRACTION METHODS

SFE hp SFE model 7680T with hp 1050 pump & Hypersil ODS

30m trap was used. Extraction of 10g food samples was carried out in 3 steps.

Parameters Step# I Step# II Step# III

CO2 Density (g/ml) 0.25 0.67 0.67

CO2 F.R. (ml/min) 1 2.5 2.5

Pressure (psi) 1117 3469 3469Chamber Temp. (°C) 40 80 80Nozzle Temp. (°C) 45 45 45Modifier (MeOH) % 0 0 30Time(min) 5 15 5Extracted sample was eluted from the ODS trap by 1.5 ml MeOH

ODS trap regenerated by rinsing 2 ml of MeCl2 followed by 2 ml MeOH

ATRAZINE DETERMINATION METHODSSFC

hp SFC model G1205A attached to an hp 1050 DAD& G1205A modifier pump was used.

SFC parameters was carried out at: Temp. (°C) 30 Press. (psi) 80-150 Flow (ml/min) 1-2 Modifier (%) 2-3 MeOH Column Alltec Hypersil APS 25m, 205mm, ID

4.6mm W.L. (nm) 210 Time (min) 10

ELISA procedures (1) Strip format of negative control {NC} (C), 3 calibrators

(C1-C3) and (S1 to S88). for food samples extract. (2) Add 80 l of NC (C), 80 l of each calibrator (C1-C3) and

80 l of each food extract (S1 to S88) to their respective wells.

(3) Add 80 l of Atrazine-Enzyme conjugate to each well. (4) Rapid circular motion for 1 minute to mix contents of

wells. (5) Cover by parafilm to prevent evaporation and incubate

at ambient temperature for 1 hour with orbital mixing at 200 rpm.

(6) Vigorously shake the contents of the wells, five times washing by a micrototer plate washer to flood the wells completely with cool running tab water, then shake to empty.

(7) Add 80 l of substrate to each well (C), (C1 to C3) and (S1 to S88).

(8) Add 40 l of chromogen sol. to each well. (9) Mix for 1 min., cover, & incubate for 30 min.

with orbital mixing at 200 rpm. (10) Add 40 l of stop sol. to each well arrest the

blue color development and turn the reaction solution yellow, mix thoroughly without spilling until all of the blue has converted to yellow.

A Microplate Reader system model MR 5000 with Biolinx assay manag. software was using as microtiter plate reader to interpret the results at wavelength 450 nm.

Auto-zero on air in a blank well to measure and record the Optical Density (OD) of each wells contents as %Bo using semi-log curve with data reduction capabilities fit for the standard curve.

After OD reading by microtiter plate reader for all of the 96 wells, average the OD of each set of calibrators and food samples and calculates of the Bo.

The %Bo calculation is used as a means of equalizing different runs of assay, also %Bo relationship of calibrators and samples to the negative control should remain fairly constant. Graph %Bo of each calibrator against its Atrazine concentration on the semi-log scale.

Determine the Atrazine concentration of each food sample by finding its %Bovalue and the corresponding concentration level on the graph.

Interpolation of sample concentration is only valid if the %Bo of the sample falls within the range of the

% Bo’s set by the calibrators. Average OD of calibrator or sample

%Bo = --------------------------------------------------- x 100

Average OD of negative control

100- % Bo

Cx = C determined ------------------------

100

OD= Optical Density. Cx = Actual concentration of Atrazine.

RESULTS Minimum Detection Limits (MDL) of Atrazine by

SFC/UVD at 220 nm and ELISA technique at 450 nm.

Atrazine (ppb) SFC ELISA

0.001 ND* D** 0.03 ND D 0.06 ND D 0.09 D D 0.1 D D 0.5 D D

1.0 D D

-------------------------------------------------------------------------------------------

*= Not Detected **= Detected

Extraction & Determination TimeExtraction time(min)/ sample

SFE MSE15.0 5.0

Determination time (min)/ sampleSFC ELISA10.0 2.1

Atrazine residues (ppb) & RSD in Juice samples

Samples SFE MSE SFC ELISA SFC

ELISA

Guava ND 0.0203 ND 0.0203--------------------------------------------------------------------------------Mango 0.3105 0.3508 0.2707 0.3405--------------------------------------------------------------------------------

cocktail ND ND ND ND

--------------------------------------------------------------

Atrazine residues (ppb) & RSD in frozen samples & strawberry jam.

SFE MSESamples

SFC ELISA SFC ELISA

Mixed veg. 0.7208 0.7608 0.7009 0.7408

Molukhia 0.6104 0.6903 0.5803 0.6702

Artichoke, ND 0.0208 ND 0.0208

Colocassia, ND 0.0303 ND 0.0203

Beans 0.6106 0.7108 0.5908 0.6408

Aubergines 0.2404 0.3203 0.2207 0.2903

Okra ND 0.0508 ND 0.0308

Strawberry jam 0.5308 0.6108 0.4806 0.5806

Atrazine recovery % & RSD in Juice samples

Samples SFE MSE SFC ELISA SFC ELISA Guava 93.3 1.2 98.7 0.8 92.4 1.6 97.4 1.6

-------------------------------------------------------------------------------------------------

Mango 94.41.1 97.20.6 93.21.3 97.11.3

-------------------------------------------------------------------------------------------------

cocktail 94.21.5 96.80.7 94.82.7

95.52.7

------------------------------------------------

Atrazine recovery % & RSD in frozen samples & strawberry jam.

SFE MSE Samples

SFC ELISA SFC ELISA

Mixed veg. 93.82.7 98.41.2 93.42.6 97.41.6

Molukhia 92.31.6 97.21.3 91.22.3 96.21.3

Artichoke, 95.41.9 99.81.7 93.83.7 99.12.4

Colocassia, 95.21.3 97.41.6 95.03.6 96.71.6

Beans 92.82.7 98.21.5 92.22.3 97.31.3

Aubergines 95.41.6 99.81.3 94.82.6 98.82.7

Okra 92.21.3 95.41.2 91.41.9 95.22.5

Strawberry jam 90.82.7 92.91.8 89.13.4 91.32.6

CONCLUSION The MDL of Atrazine was 0.06ppb by SFC & 0.01 ppb

by ELISA. Extraction time / sample was less for MSE than SFE. Deter. Time was 10 min. by SFC & 2.1 min. by ELISA. ELISA is considerably fast with LDL than SFC. Atrazine risidue ND in cocktail juice by both techniques. Atrazine risidue ND in guava juice, frozen artichoke,

colocassia, & okra by SFC techniques. Atrazine risidue were detected in 54.5% and 90.9% of

investgated food samples using SFC & ELISA respectively.

ELISA technique coupled with SFE & MSE is less time consuming, high recovery% and more senstive with lower detection limit of Atrazine residues in foods.