Abstract
A colorimetric determination of diphenylether herbicides ; CNP, NIP and X-52 (chlomethoxynil), was achieved according to the procedure for the colorimetric determination of organophosphorus pesticides ; EPN, parathion and methylparathion, which consists of n-hexane extraction, reduction with zinc, diazotization with nitrite and then coupling reaction with N-(1-naphthyl) ethylenediamine. Diazo-coupling derivatives of CNP and NIP have λmax at 570 nm and mol absorptivity (ε) is 3.2×104 (CNP) and 3.3×104 (NIP), but X-52 does not yield sufficient intensity (ε : 0.1×104 at 585 nm) for the presented method. The sample water alkalized with NaOH is extracted with n-hexane and the extract is shaked with HCl (1 : 9). After layeres separate, aqueous layer contained CNP-amino and NIP-amino is treated to form their diazo-coupling derivatives directly and n-hexane layer contained CNP, NIP, X-52 and fenitrothion is subjected to florisil column chromatography. The 2% ethylether/n-hexane 50 ml eluate for CNP, the next 70 ml eluate for NIP and the 5% ethylether/n-hexane 100 ml eluate for X-52 are reduced and reacted to form their diazo-coupling derivatives. The average recoveries at the 0.2 and 2.0 ppm level throughout the procedure were 79% (CNP), 80% (NIP), 0% (X-52) and 95% (CNP-amino+NIP-amino).
