The recoveries from untreated control samples, fortified with benomyl, carbendazim and thiophanate-methyl at levels of 0.04 to 1.0 mg/kg, ranged from 73 to 94% and averaged 84%
(see Table). Blank values did not occur. The routine limit of determination was 0.02 mg/kg for lettuce, 0.04 mg/kg for wheat grains, and 0.08 mg/kg for wheat straw.
Table. Percent recoveries from lettuce, wheat grains, and wheat straw, fortified with benomyl, carbend- azim and thiophanate-methyl, expressed as carbendazim equivalents.
Analytical material Compound added (mg/kg) Carbendazim Thiophanate-
methyl Benomyl Carbendazim equiv. *)
Recovery
Lettuce
Wheat grains
Wheat straw
0.04 0.4
0.02 0.2 0.1 0.5 0.05 0.2 0.2 1.0 0.1 0.5
78 0.06
0.6 0.02 0.2
0.2 1.0 0.05 0.2 0.4 1.0 0.1 0.5
0.06 0.6 0.02 0.2
0.05 0.2
0.1 0.5
0.034 0.34 0.04 0.40 0.044 0.44
0.12 0.56 0.11 0.44
0.22 0.56 0.22 1.11
78 73 81 85 77/85/88 85/88/88
82 86 79/82 81/82/89/91
84 83 93 84 79 73 78/90/94 79/83/86
*) The factors for conversion of thiophanate-methyl and benomyl to carbendazim are 0.558 and 0.659, respectively.
7.3 Calculation of residues
The residue R of benomyl, carbendazim and thiophanate-methyl, expressed in mg/kg carbendazim, is calculated from the following equation:
wA-vE x-vE n d
VR 1. VrG
Benomyl, Carbendazim, Thiophanate-methyl 75 where
G = sample weight (in g)
VEx = volume of extract solution from 6.1 (in ml)
VR1 = portion of volume VEx used for further processing (in ml) VEnd = terminal volume of sample solution from 6.5 (in ml)
Vj = portion of volume VEnd injected into high-performance liquid chromatograph (volume of sample loop) (in \i\)
WA = amount of carbendazim for Vj read from calibration curve (in ng)
8 Important points
No data
9 Reference
H. Suzuki et al., Rapid and systematic determination of thiophanate methyl (TPM), benomyl and MBC (methyl benzimidazolecarbamate) by a combined method of alumina column clean- up and UV spectrophotometry, Agric. Biol. Chem. 46, 549-552 (1982).
10 Authors
Ciba-Geigy AG, Agricultural Division, Basle, Switzerland, G. Formica, C. Giannone and W. D. Hormann
Bitertanol 613-A
Apples, barley (green matter, grains and straw), cherries High-performance (fruit, conserves, juice and press pulp), cucumbers, pears, liquid chromato- plums (fruit, jam and puree), sugar beet (foliage and graphic determination edible root), tea (dry leaf, liquor and infused leaf),
tomatoes Soil, water
(German version published 1991)
1 Introduction
For data on physico-chemical properties of bitertanol, see Method for Bitertanol, Triadi- mefon, Triadimenol on p. 87, this Volume.
2 Outline of method
Bitertanol residues are extracted from cereal samples (green matter, grains and straw) and tea leaves with an acetone-water mixture, and from other plant material with acetone. Soil samples are refluxed in aqueous methanol to extract the residues. The extract is concentrated to an aqueous residue, which is made up to a definite volume. An aliquot of this solution is transferred onto a disposable extraction column. Water and liquid samples are transferred directly onto the disposable extraction column. The column is eluted with a cyclohexane-ethyl acetate mixture, and the eluate is evaporated to dryness. Bitertanol is determined by high- performance liquid chromatography using a fluorescence detector.
3 Apparatus
Homogenizer
Wide neck glass bottles, 1-1 and 500-ml, with ground joints Buchner porcelain funnel, 11 cm dia.
Filter paper, 11 cm dia., fast flow rate Filtration flask, 1-1
Round-bottomed flasks, 1-1, 500-ml and 250 ml, with ground joints Rotary vacuum evaporator, 40 °C bath temperature
Glass funnel, 10 cm dia.
Reflux condenser
Heating mantle for 1-1 round-bottomed flask Solvent dispensers, 50-ml and 10-ml
Graduated cylinders, 500-ml and 250-ml
78 Bitertanol
Volumetric flasks, 100-ml, 50-ml and 25-ml, with ground joints Volumetric pipets, 100-ml, 50-ml, 10-ml, 5-ml, 2-ml and 1-ml Centrifuge, e. g. Variofuge (Heraeus-Christ), with 10-ml glass tubes Ultrasonic bath
Test tubes, 10-ml, graduated, with ground stoppers
High-performance liquid chromatograph equipped with fluorescence detector Microsyringe, 100- JLXI
4 Reagents
Acetone, for residue analysis Acetonitrile, for chromatography Cyclohexane, for residue analysis Ethyl acetate, for residue analysis Methanol, for residue analysis Water, ultrapure
Acetone + water mixture 2:1 v/v Acetonitrile + water mixture 1:1 v/v Methanol + water mixture 7:3 v/v
Eluting mixture: cyclohexane + ethyl acetate 85:15 v/v Mobile phase: acetonitrile + water mixture 55:45 v/v Bitertanol stock solution: 1000 M-g/ml ethyl acetate
Bitertanol standard solutions: 0.05-100 M-g/ml acetonitrile-water mixture 1:1 v/v Filter aid, e. g. Celite 545
Disposable extraction columns, 100-ml and 50-ml (Chem Elut CE 20100 and CE 2050;
Analytichem)
Air, synthetic, re-purified Helium 4.6 (> 99.996 vol. %)
5 Sampling and sample preparation
The analytical sample is taken and prepared as described on pp. 17 ff and pp. 21 f, Vol. 1. For water samples, observe the guidelines given on pp. 23 ff, Vol. 1.
6 Procedure
6.1 Extraction
6.1.1 Plant material with high water content
Transfer 100 g of the analytical sample (G) into the 1-1 glass bottle with 200 ml acetone and homogenize for approx. 3 min. For tomatoes and other material from which it is difficult to take a representative 100-g sample, homogenize 200 g with 300 ml acetone.
Bitertanol 79 Add approx. 15 g filter aid, and filter the homogenate through a fast flow-rate filter paper in a Buchner porcelain funnel, using gentle suction. Rinse the filter cake and the bottle several times with a total of 150 ml acetone-water mixture. Allow the filter cake to pull dry, and discard it. Transfer the filtrate to a 1-1 round-bottomed flask and rotary-evaporate to an aqueous residue (approx. 150 ml for a 100-g sample, approx. 250 ml for a 200-g sample).
Make up the aqueous residue with water to 200 ml (100-g sample) or 400 ml (200-g sample) in a graduated cylinder (VEx). Pipet 50 ml (VR1) of this solution onto a dry disposable 50-ml extraction column and allow the solution to soak in. Elute the column three times with 50-ml portions of the eluting mixture. Collect the eluate in a 250-ml round-bottomed flask and rotary-evaporate to dryness. Proceed to step 6.2.
6.1.2 Cereals
Transfer 50 g of cereal green matter or grains, or 25 g of straw (G) into the 1-1 glass bottle with 450 ml (for grains, 300 ml) acetone-water mixture, allow to stand for 10 min, and then homogenize for approx. 3 min.
Add approx. 15 g filter aid, and filter the homogenate through a fast flow-rate filter paper in a Buchner porcelain funnel, using gentle suction. Rinse the filter cake and the bottle several times with a total of 150 ml acetone-water mixture. Allow the filter cake to pull dry, and discard it. Transfer the filtrate to a 1-1 round-bottomed flask and rotary-evaporate to an aqueous residue.
Make up the aqueous residue with water to 200 ml in a graduated cylinder (VEx). Pipet 100 ml (VR1) of this solution onto a dry disposable 100-ml extraction column and allow the solution to soak in. Elute the column three times with 100-ml portions of the eluting mixture.
Collect the eluate in a 500-ml round-bottomed flask and rotary-evaporate to dryness. Proceed to step 6.2.
6.1.3 Tea leaves
Transfer 25 g of dry tea leaves or 10 g of infused tea leaves (G) into the 500-ml glass bottle with 100 ml acetone-water mixture and homogenize for approx. 3 min.
Add approx. 15 g filter aid, and filter the homogenate through a fast flow-rate filter paper in a Buchner porcelain funnel, using gentle suction. Rinse the filter cake and the bottle several times with a total of 150 ml acetone-water mixture. Allow the filter cake to pull dry, and discard it. Transfer the filtrate to a 1-1 round-bottomed flask and rotary-evaporate to an aqueous residue.
Make up the aqueous residue with water to 150 ml in a graduated cylinder (VEx). Pipet 50 ml (VR1) of this solution onto a dry disposable 50-ml extraction column and allow the solution to soak in. Elute the column three times with 50-ml portions of the eluting mixture.
Collect the eluate in a 250-ml round-bottomed flask and rotary-evaporate to dryness. Proceed to step 6.2.
6.1.4 Beverages (e. g. cherry juice, tea liquor)
Pipet 50 ml of the analytical sample (G) directly onto a dry disposable 50-ml extraction col- umn and allow the liquid to soak in. Elute the column three times with 50-ml portions of the eluting mixture. Collect the eluate in a 250-ml round-bottomed flask and rotary-evaporate to dryness. Proceed to step 6.2.
80 Bltertanol
6.1.5 Soil
Weigh 50 g soil (G) into a 1-1 round-bottomed flask, add 300 ml methanol-water mixture, and heat under reflux for 4 h. Allow to cool, and filter the suspension with gentle suction through a fast flow-rate filter paper, covered with approx. 15 g filter aid, in a Buchner porcelain funnel.
Rinse the flask and filter cake twice with 50-ml portions of methanol-water mixture. Allow the filter cake to pull dry, and discard it. Transfer the filtrate to a 1-1 round-bottomed flask and rotary-evaporate to an aqueous residue (approx. 130 ml). Make up the aqueous residue with water to 200 ml in a graduated cylinder (VEx). Pipet 100 ml (VR1) of this solution onto a dry disposable 100-ml extraction column and allow the solution to soak in. Elute the column three times with 100-ml portions of the eluting mixture. Collect the eluate in a 500-ml round- bottomed flask and rotary-evaporate to dryness. Proceed to step 6.2.
6.1.6 Water
Pipet 100 ml of the water sample (G) directly onto a dry disposable 100-ml extraction column and allow the water to soak in. Elute the column three times with 100-ml portions of the eluting mixture. Collect the eluate in a 500-ml round-bottomed flask and rotary-evaporate to dryness. Proceed to step 6.2.