Chloracetanilide herbicides

Chloracetanilide herbicides like alachlor, metolachlor and metazachlor can be analysed in positive-ion mode. In ESI, protonated and sodiated molecules are observed as well as the loss of methanol [16, 34, 47, 63]. The MS-MS spectmm of alachlor was stndied, nsing MS-MS and in-source CID on a orthogonal-acceleration time-of-flight mass spectrometer [63]. 

A variety of neutral degradation products of the chloracetanilide herbicide alachlor was identified [63, 115]. However, the ionic metabohtes such as the oxoethanesulfonic acid derivative appear to be of more significance, as they are readily leached to groundwater. WMe alachlor itself is amenable to GC-MS, its ionic metabolites are not. Initially, GC-MS, LC-UV-DAD, and fast-atom bombardment MS-MS were applied in the analysis and identification of such metabolites [119]. Subsequently, the potential of LC-ESI-MS in this area was recognized [120]. Both oxanilic acid and oxoethanesulfonic acid metabohtes of alachlor, acetochlor and metolachlor were identified in snrface water and gronnd water, and subsequently determined with detection limits at the 0.01-pg/l level using off-hne SPE in combination with LC-MS [120]. 

As an example 2.5 1 of estuarine water were extracted with two times 100 ml dichloromethane for the analysis of chloracetanilide, triazine, and phenylurea herbicides. The extract was evaporated to dryness and the residue was dissolved in 400 pi of methanol, from which 10 pi was injected in LC-MS. Typical absolute detection hmits in SIM are between 10 and 500 pg [74]. 

Some compound classes have been widely analyzed using ESI-MS, enabhng statements on the likeliness of Na+-cationizatioa Pesticide classes that are prone to the formation of [M+Na]+, often next to [M+H]+,are carbamate and oiganophos-phorus pesticides, and various classes of herbicides like phenylureas, sulfonylmeas, and chloracetanilides. Antibiotics that readily show [M+Na] next to [M+H]" are sulfonamides, betalactams, tetracychnes, aminoglycosides, and macrolides. The... 

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