Determination of organo-zinc based fungicides in timber treatments employing gas chromatographic analysis with mass selective detection and/or inductively coupled plasma atomic emission spectroscopy

A method for the determination of zinc octoate (zinc 2-ethylhexanoate) and acypetacs zinc in occupational hygiene samples and wood treatments formulat ions is described. The zinc carboxylates are liquid-liquid partitioned betw een toluene and 1 M HCl, with the liberated acids being extracted into the toluene and zinc (chloride) into the acid. The carboxylic acids are then me thylated using trimethylsilyldiazomethane-methanoI and the resultant methyl esters are selectively and sensitively analysed by gas chromatography with mass selective detection (GC-MS). Alternatively, the zinc content of the a cid extract can be analysed by inductively coupled plasma atomic emission s pectroscopy (ICP-AES). GC-MS is the preferred method of analysis for zinc o ctoate, where a single analyte (methyl-2-ethylhexanoate) is produced for an alysis. Because acypetacs zinc contains a complex mixture of carboxylates, quantitative GC-MS analysis of the methyl esters produced is impractical an d ICP-AES is the preferred method for quantitation. In this case, GC-MS can be used to confirm the identity of the product used. The analysis of occup ational hygiene samples (cotton pads, gloves and socks as well as Tenax tub es and GF/A filters) spiked with metal carboxylates is demonstrated. Recove ries around 70-90% and reproducibilities of 5-23% (n=6-8) were typically ac hieved for the determination of tin octoate (a surrogate for zinc octoate) at spiking levels ranging from 4 to 190 mug per sampling device. Recoveries around 102-106% and reproducibilities of 10-12% (n=5-6) were typically ach ieved for acypetacs zinc at spiking levels ranging from 100 mg per sampling device. Reaction yields for the octoate methylation reaction were in the r egion of 85-87%. The method was used to monitor for occupational exposure t o zinc octoate and acypetacs zinc during the application of wood treatments to fences. Crown copyright (C) 2001 Published by Elsevier Science B.V. All rights reserved.