Quantitative Determination of Paralytic Shellfish Poisoning Toxins in Shellfish Using Prechromatographic Oxidation and Liquid Chromatography with Fluorescence Detection: Collaborative Study

A collaborative study was conducted for the determination of paralytic shellfish poisoning (PSP) toxins in shellfish. The method used liquid chromatography with fluorescence detection after prechromatographic oxidation of the toxins with hydrogen peroxide and periodate. The PSP toxins studied were saxitoxin (STX), neosaxitoxin (NEO), gonyautoxins 2 and 3 (GTX2,3; together), gonyautoxins 1 and 4 (GTX1,4; together), decarbamoyl saxitoxin (dcSTX), B-1 (GTX5), C-1 and C-2 (C1,2; together), and C-3 and C-4 (C3,4; together). B-2 (GTX6) toxin was also included, but for qualitative identification only. Mussels, both blank and naturally contaminated, were mixed and homogenized to provide a variety of PSP toxin mixtures and concentration levels. The same procedure was followed with clams, oysters, and scallops. Twenty-one test samples in total were sent to 21 collaborators who agreed to participate in the study. Results were obtained from 18 laboratories representing 14 different countries. It is recommended that the method be adopted First Action by AOAC INTERNATIONAL.

Use patterns and residual levels of organophosphate pesticides on vegetables in Trinidad, West Indies

The twin-island state of Trinidad and Tobago produces much of the fresh fruit and vegetables consumed locally, although some are exported to Europe and North America. On average, approximately 1500 tons of pesticides are imported annually, of which about 10-15% are organophosphates. A survey of local farmers revealed that a wide range of pesticides are used and that the same pesticides are used on several crops to control different pests. Application rates exceeding manufacturers' recommendations are also common, as is the disregard of recommended preharvest intervals after pesticide application. Praedial larceny and subsequent sale of freshly sprayed crops also contribute to the risks posed to consumers by pesticide residues. A market basket survey of produce conducted between October 1996 and May 1997 in Trinidad for organophosphate pesticides showed that 10% of produce exceeded the internationally acceptable maximum residue limits (MRLs) for the respective pesticides. Celery constituted 6.5% of all such samples, with over 83% of celery samples exceeding the MRL. Organophosphate pesticides detected were methamidophos, triazophos, prophenofos, diazinon, ethion, pirimiphos methyl, malathion, and dimethoate, with the first 4 being the most commonly detected. There is an urgent need for comprehensive monitoring and control of pesticides on produce by local regulatory agencies, especially because the above data relate only to one class of pesticides. The education of farmers on safe operating practices regarding pesticide application and observation of recommended preharvest intervals for applied pesticides is also required.