Dissolve the residue derived from 6.2.2 in mobile phase and dilute to an appropriate volume, e.g. 10 ml (VEnd). Inject an aliquot of this solution (Vj) into the high-performance liquid chromatograph.
Operating conditions
Chromatograph Spectra-Physics SP 8700
Injector Injection valve 7125 with sample loop (Rheodyne) Column Zorbax Sil, 4.6 m m i. d., 25 cm long (Du Pont No.
880952701) Column temperature 25 °C
Mobile phase Cyclohexane-isopropanol-methanol-acetic acid-water Flow rate 0.5 ml/min
Conditioning solution Isopropanol-methanol-acetic acid-water
Detector Photoconductivity detector (Tracor 965), operated with a mercury lamp at 254 nm, ATT = 5
Recorder 5 mV; chart speed 5 mm/min Injection volume 20 JLAI
Retention times for
chlorsulfuron 13 min metsulfuron-methyl 15 min
The Zorbax Sil column must be conditioned before use. For this end, pump conditioning solu- tion through the column for 4 h at a flow rate of 0.7 ml/min. Next equilibrate the column for 3 h with mobile phase at the same flow rate. Moreover, pump conditioning solution at a flow rate of 0.15 ml/min through the system over night, changing to mobile phase at a flow rate of 0.5 ml/min for 1 h before beginning a new series of measurements the next morning.
7 Evaluation
7.1 Method
Quantitation is performed by the calibration technique. Prepare calibration curves as follows.
Inject equal volumes of each chlorsulfuron and metsulfuron-methyl standard solution into the high-performance liquid chromatograph. Plot the areas or heights of the peaks obtained vs.
150 Chlorsulfuron, Metsulfuron
ng chlorsulfuron or metsulfuron-methyl, respectively. Also inject equal volumes of the sample solutions. For the areas or heights of the peaks obtained for these solutions, read the ap- propriate amounts of compound from the corresponding calibration curve.
7.2 Recoveries, limit of detection and limit of determination
The recoveries from untreated cereal control samples, fortified with chlorsulfuron and metsulfuron-methyl at levels of 0.05 to 10 mg/kg, ranged from 68 to 103% and averaged 80%.
The limit of detection was 0.02 mg/kg, and the limit of determination was 0.05 mg/kg or, for cereal green matter, 0.1 mg/kg. Blanks usually did not occur or, if so, they were less than 0.02 mg/kg.
The recoveries from soils, fortified at levels of 0.01 to 1 mg/kg, ranged from 70 to 112%
and averaged 91%. The limit of detection was 0.005 mg/kg, and the limit of determination was 0.01 mg/kg. Blanks were less than 0.0025 mg/kg. The recoveries from tap water fortified at 1 |ig/l ranged from 70 to 100%, and the limit of determination was 1 u.g/1.
7.3 Calculation of residues
The residue R, expressed in mg/kg chlorsulfuron or metsulfuron-methyl, is calculated from the following equations:
for soil and water R = W A ' VEnd
VrG where
G = sample weight (in g) or volume (in ml)
VEx = total volume of solution after addition of extraction solution to filtered cereal extract from 6.1.1 (in ml)
VR1 = portion of volume VEx used for further cleanup (in ml) VEnd = terminal volume of sample solution from 6.3 (in ml)
Vj = portion of volume VEnd injected into high-performance liquid chromatograph (volume of sample loop) (in \i\)
WA = amount of chlorsulfuron or metsulfuron-methyl for Vj read from calibration curve (in ng)
8 Important points
The pH adjustment in 6.2.1 takes longer than one would expect and must be carried out very carefully. Only at pH 3-4, chlorsulfuron and metsulfuron-methyl are existing in the unionized form which can be transferred into the organic phase. If the pH is too low, decomposition
Chlorsulfuron, Metsulfuron 151 is likely to occur; if it is too high, both compounds are partially ionized and will not be ex- tracted quantitatively.
A LiChrosorb column can also be used for the HPLC measurement: 4 mm i. d., 25 cm long;
packed with LiChrosorb Si 60, particle size 7 urn; other conditions as described in 6.3.
When evaporated to dryness, the cleaned-up extract can be stored in a freezer for a max- imum of four days if immediate measurement is not possible.
In order to make allowance for baseline drifting, the balance is best set to approx. 30%
above the zero point of the recorder prior to each measurement. The balance must be re- adjusted after each measurement, if necessary. If possible, leave the mercury lamp switched on over night.
9 References
E.W. Zahnow, Analysis of the herbicide chlorsulfuron in soil by liquid chromatography, J. Agric. Food Chem. 30, 854-857 (1982).
R. V. Slates, Determination of chlorsulfuron residues in grain, straw, and green plants of cereals by high-performance liquid chromatography, J. Agric. Food Chem. 31, 113-117 (1983).
10 Authors
DuPont de Nemours & Co., Biochemicals Department, Research Division, Experimental Sta- tion, Wilmington, DE, U.S.A., L. W. Hershberger, R. V. Slates and E. W. Zahnow Federal Biological Research Centre for Agriculture and Forestry, Braunschweig, M. Blacha- Puller, H. Kohle, H.-G. Nolting and J. Siebers
Copper Oxychloride (as copper) 147-A
Grapes Atomic absorption
spectrophotometric determination (German version published 1985)
1 Introduction Chemical name Structural formula Empirical formula Molar mass Melting point Solubility
Other properties
Dicopper chloride trihydroxide (IUPAC) Cu2(OH)3Cl or CuCl2 • 3Cu(OH)2 Cu2H3ClO3 or Cu4H6Cl2O6
213.56 or 427.12
Above 220 °C, decomposition with elimination of hydrochloric acid to oxides of copper
Virtually insoluble in water and organic solvents;
soluble in mineral acids yielding the corresponding copper salts;
soluble in ammonia, amine and EDTA solutions, under complex formation
Largely stable in neutral media, decomposed by warm- ing in alkaline media, yielding oxides
2 Outline of method
Copper containing residues are stripped from the grapes with a lead-doped aqueous solution of ethylenedinitrilo tetraacetic acid (EDTA, disodium salt). The copper content of this solu- tion is determined by flame atomic absorption spectrophotometry (FAAS) at 324.7 nm.
3 Apparatus
Volumetric flasks, 1-1 and 100-ml
Wide neck bottle, 500-ml, with ground stopper Water bath, 40 °C temperature
Glass funnel, 7 cm dia.
Fluted filter paper, 15 cm dia. (Schleicher & Schull) Flame atomic absorption spectrophotometer
154 Copper Oxychloride (as copper)
4 Reagents
Cu standard solution: A solution of 2.116 g cupric chloride (CuCl2) in water (Merck No.
9987) is made up to 1 1 in a volumetric flask. The solution contains 1 mg/ml Cu
Pb standard solution: A solution of 1.598 g lead nitrate [Pb(NO3)2] in water (Merck No.
9969) is made up to 1 1 in a volumetric flask. The solution contains 1 mg/ml Pb
EDTA solution: 1 g/100 ml of ethylenedinitrilo tetraacetic acid disodium salt dihydrate p. a.
(Merck No. 8418)
Stripping solution: 10 g ethylenedinitrilo tetraacetic acid disodium salt dihydrate p.a. and 20 ml Pb standard solution are made up to 1 1 in a volumetric flask. The solution contains 20 mg/1 Pb
Acetylene, 99.6 vol. °/o Air, re-purified
5 Sampling and sample preparation
The analytical sample is taken and prepared as described on pp. 17 ff, Vol. 1.
6 Procedure
6.1 Extraction
Transfer 100 g of the unchopped analytical sample (G) into the wide neck bottle, add 100 ml stripping solution (VEx), and allow to stand for 1 h with occasional swirling. With deep- frozen grapes, warm the solution in a water bath at 40 °C. Filter the solution through a fluted filter paper.