Report No DWI0644

SEPT 1986


Four methods for the analysis of carbamate herbicides, pesticides and fungicides, which had been drafted by the Pesticide Panel of the Standing Committee of Analysts were tested on samples of distilled and river waters spiked with a selection of carbamates and ureas. The methods were:

(1) A normal-phase HPLC method.

(2) A TLC method.

(3) A method for dialkyldithiocarbamates by conversion to CS2.

(4) An extraction and colorimetric method.

The best and most versatile method was the HPLC procedure. Most compounds are measured with good detection limits and precision. Small ammendments to the method enable it to be used for almost all the compounds in the group.

The TLC procedure was adequate as a confirmatory technique and perhaps for identification purposes but as with all TLC methods the results were imprecise and statistical estimation of the performance less than perfect.

The method for dialkyldithiocarbamates involving conversion to carbon disulphide and estimation by gas chromatography with flame-photometric detection is essentially a screening technique for a number of carbamates which are not detected by the HPLC or TLC procedures.

It was based on a method for crop residues and soil and the procedure can be adapted to cope with these samples as well as water. The method proved satisfactory although the recoveries were rather low and the method unspecific.

The colorimetric method was regarded by SCA as a method for Total Carbamates to screen water samples for a wide range of compounds of this type. However, the method gave a colour reaction with only very few carbamates, all of which could be determined by the HPLC method. Furthermore the recoveries were low and variable and the precision extremely poor.

It is sugested that this procedure does not become a method recommended for use in the Water Industry. The other three methods should cope with all compounds in the group in use at the present time.

The appendices to the individual methods are intended for use as the new SCA drafts subject to approval and editing.

Copies of this report may be available as an Acrobat pdf download under the 'Find Completed Research' heading on the DWI website.