Gas-Liquid Chromatographic Determination of 3,6-Dichloropicolinic Acid in Soils

Abstract

A gas-liquid chromatographic (GLC) method has been developed for the determination of the experimental herbicide 3,6-dichloropicolinic acid (Dowco 290) in soils. The method involves extraction of 1 g soil samples with 1N NaCl at approximately pH 7, methylation with diazomethane utilizing a microgenerator, and detection by electron capture GLC. Interferences are small, so that a cleanup step is not necessary even at the 6 ppb level. The procedure is rapid, requiring only 45 min/sample. Recoveries range from 84 to 94% at the 6–1000 ppb level with a minimum detectable limit of 6 ppb. Standard deviations for the percentage recovery values vary from 10.9 to 2.3 for the tested range of 6.7–670 ppb, respectively.

Gas chromatography‐mass spectrometry analysis of the herbicide clopyralid in differentially cultivated soils

“…In order to investigate the reproducibility of the method, two different soils (soil 1 and soil 2) were employed. Recovery rates at concentrations of 50, 100, and 500 g/kg soil were 73 Ϯ 11, 69 Ϯ 12, and 68 Ϯ 9 for conventional and 83 Ϯ 6, 75 Ϯ 5, and 76 Ϯ 4 for ultrasound-enhanced extraction, resulting in means of 70 Ϯ 10% for conventional [5,[10][11][12] extraction by shaking with solvent and 78 Ϯ 5% for ultrasound-enhanced extraction (n ϭ 10 each concentration). Application of ultrasound enhances the dissociation of clay-humic acid complexes in soil and increases reliability and recovery of clopyralid extraction [5,10,11].…”

“…Chem. 15,1996 S. Schütz et al shifts the pH into the acidic range and NaCl helps to transfer the undissociated clopyralid acid into the organic phase [5,[10][11][12]. After phase separation, the organic phase was extracted with 2 ml 10% sodium phosphate buffer (pH ϭ 8).…”

“…Although the published HPLC-UV methods [6,7] suffer from a general lack of sensitivity, the GC-ECD methods [4,5,8,9] fall short in reliability because of instabilities of baselines due to numerous unidentified by-products formed in the derivatization step. Another published gas chromatography-mass spectrometry (GC-MS) method employing clopyralid methyl ester [10,11] has not been considered because of the toxic, carcinogenic, and explosive properties of the diazomethane needed for the derivatization reaction. A further GC-MS method [12] shows drawbacks in the reliability of the derivatization procedure.…”

Droplets-based microextraction assisted SPME for GC-MS analysis of polar compounds such as clopyralid in water

“…The regulatory analytical methods for the determination of clopyralid from water samples, soil, and compost include gas chromatography (GC) [3][4][5][6][7][8][9][10] and liquid chromatography (LC). [11][12][13][14][15] Since clopyralid has a carboxylic group, the GC analysis required also the derivatization of the analyte as methyl ester, 4,6 1-butyl ester, 3,5,7 pentauorobenzyl ester 8 or silyl derivatives.…”

“…The regulatory analytical methods for the determination of clopyralid from water samples, soil, and compost include gas chromatography (GC) [3][4][5][6][7][8][9][10] and liquid chromatography (LC). [11][12][13][14][15] Since clopyralid has a carboxylic group, the GC analysis required also the derivatization of the analyte as methyl ester, 4,6 1-butyl ester, 3,5,7 pentauorobenzyl ester 8 or silyl derivatives. 10 LC could be an attractive method because no derivatization is required, but the sensitivity of the UV detector is not enough to detect and quantify clopyralid at trace levels in a quality control lab without a mass spectrometer.…”