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Gas-liquid
chromatographic determination of 4-chlorophenoxyacetic acid residues in mung
bean sprouts.
J Assoc Off Anal Chem 1982 Sep;65(5):1118-21
Wong YS.
A gas-liquid chromatographic (GLC) method is described for determining
4-chlorophenoxyacetic acid (CPA) residues in mung bean sprouts. The residues
were extracted from samples by using ethyl acetate followed by liquid-liquid
partition into 5% NaHCO3 solution. After acidification and reextraction with
ethyl acetate, CPA was reacted with pentafluorobenzyl bromide (PFB-Br) to form
the PFB derivative. The reaction mixture was separated on a silica gel column to
remove excess reagent, and the derivative was eluted with a solution of 75%
toluene in hexane. GLC separations were performed on a 3% OV-1 column at 230
degrees C. As low as 10 pg CPA could be quantitated, which is equivalent to
about 0.05 ppm at residue level, using an electron capture detector. Recoveries
of CPA from fortified mung bean sprouts (0.05, 0.20, and 0.50 ppm) ranged from
71 to 107%. The PFB derivative was further identified by gas chromatography-mass
spectrometry.
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