Chlor-organic pesticide determination method in cabbages, potatoes and apples using solid phase extraction (SPE) and gas chromatography method.

1. Designation and application field

The method is intended for determination chlor-organic pesticides content in planted products, vegetables and fruits (carrots, beets, potatoes, apples, tomatoes) with fat content not more 3%.

Short characteristic of chemicals.

Gamma isomer hexa-chlor-cyclohexane (lindane) - white crystallite substance without odour. Solubility at 20 C in
100 ml: water - 7*10^-4 g, acetone - 43.5 g, benzene - 28.9 g, ethyl alcohol - 6.4 g, diethyl ester - 20.8 g, petroleum ester - 3.5 г, hexane. Is stable to strong acids. Under action of alkalis turns into three-chlor-benzene.

Alpha isomer hexa-chlor-cyclohexane - white crystallite substance, at 288 C dissociates. Practically is not dissolving in water. Is dissolving in benzene, chloroform, ethyl alcohol, hexane.

Heptachlor - white crystallite substance, practically is not dissolved in water. Is good dissolving in benzene, xylene, toluene, ethyl alcohol, hexane. It is stable under light, high temperature.

DDT(4,4-di-chlor-di-phenyl-tri-chlor-ethane) - white crystallite substance without odour. Practically is not dissolving in water. Solubility at 24 C in 100 ml of solvent: acetone - 40.3 g, benzene - 44 g, diethyl ester - 27.5 g, four-chlorcarbon - 18 g, n-hexane - 97 g, ethyl alcohol - 2.2 g. Is stable in acidic medium, dissociates under action of alkalis.

DDD(4,4-di-chlor-di-phenyl-di-chlor-ethane) - white crystallite substance without odour. Practically insoluble in water, good soluble in benzene, acetone, methanol, n-hexane.

DDE(4,4-di-chlor-di-phenyl-di-chlor-ethylene - white crystallite substance. Solubility in water 0.014 mg/100 ml. Good soluble in acetone, benzene, n-hexane.

2. Measurement error norms

The determination method is based on extraction chlor-organic pesticides from products using organic solvent, purification the extract from intrinsic substances using solid phase extraction and substance determination using gas chromatography method. The measurement method provides determination of pesticide contents with errors not exceed values shown in Table 1.

Table 1

Lower determination limit is 0.0001 mkg of Lindane in analysed probe volume of 1 mkl.

The interval of determined concentrations is 0.001-0.2 mg/kg.

Linear range of pesticides determination is 0.00001-0.002 mkg.

Intrinsic substances (fat in quantity no more 3%, chol-organic bi-phenyles, pigments) do not affect the pesticide determination.

Probe preparation and single measurement time is not exceeds 120 minutes.

3. Measuring means, supplementary devices, reagents and materials

2.1. While carrying out measurements, the following measuring means, supplementary devices reagents and materials should be used:

2.2. Measuring means:

Gas chromatograph of type "Tswett-500" , equipped according TC 5Е 1.550.168-01 with electron capture detector (ECD) (detection limit on lindane 4х10 ^-14 g/cm³.

Analytical weights of type VLR 200 according GOST 24104-80E

Microsyringe of type MS-10 according TC 2-833-106

Measuring cylinder

2-25-2 according GOST 1770-74E

2-50-2 according GOST 1770-74E

2-100-2 according GOST 1770-74E

2-250-2 according GOST 1770-74E

Pipettes of capacity

1 cm³ according GOST 20292 3-2-1

2 cm³ according GOST 20292 3-2-2

5 cm³ according GOST 20292 3-2-5

Cilinders 100 cm³ according GOST 1770-74

Calibrated tubes with stopped pugs of 5 cm³ capacity according GOST 1770-74E 2-5-0,1

Chromatographic Data Processing System UniChrom according MAP 78-97

2.3. Supplementary devices

Packed chromatography column 2 meters with phase SE-30 or 1 meter with phase OV-17

Water-jet glass pump according GOST 10676-75

Rubber syringe

"BAKER" SPE cartridges 500 mg

Flask for filtering under vacuum 500 ml according to TC 25-11-1057

Tissue dispergiser RT-2

Tubes PB-18/180 according GOST 10515-75

Aluminium oxide for chromatography according TC 6-09-3916-75

Rotor vaporiser IR -1M according TC 25-11-917-74

Probe shaker AVU-6S according TC 64-1-2451-78

Porcelain mortar N 4,5 according GOST 9147-73

Filters with blue stripe according TC 6-09-1678-77

Double spatula according GOST 9147-73

Corks N 10 according GOST 5541-76

It is possible using different measuring means and supplemental devices, which does not lack in precision in comparison with recommended.

2.4. Materials

Nitrogen technical or special purity according GOST 9293-74

Silicone tubing ,d 4 mm according TC 64-1-2813-75

2.5. Reagents

Ethyl ester of acetic acid chemically pure according GOST 22300-76

Bidistillated water according GOST 6709-77

Hexane according TC 6-09-3375-73

Methyl alcohol according GOST 69965-77

Dry sodium sulphate according GOST 4166-76

Pesticides standards (CRM - certified reference materials)

Lindane GSO 1855-80

GCCH-α GSO 8024-94

GCCH -β GSO

Heptaclor OSO 113-04-044-91

DDT OSO 113-04-043-91

DDD OSO 113-04-051 -91

DDE OSO 113-04-121 -91

4. Method of Measurement

For chlor-organic pesticide determination in vegetables and in fruits (carrots, beets, apples, potatoes, tomatoes) is used gas chromatographic method, which is based on pesticide separation on chromatographic column length 1 meter packed with Chromaton, Chromasorb and impregnated with stationary liquid phase OV-17 in quantity of 3% or another column - length 2 meters SE-30 5%. For pesticide detection is used electron capture detector (ECD).