Automated Steam Distillation and Fluorometry for Screening for Carbaryl as 1-Naphthol in Fruits and Vegetables

Abstract

Abstract A rapid method for screening for carbaryl in methylene chloride extract solutions of various fruits and vegetables has been developed. For most crops, sufficient cleanup was effected by solidification of many impurities in paraffin wax and further by automated steam distillation of 1-naphthol (free or free plus that produced from carbaryl by alkaline hydrolysis) into an alkaline scrubbing solution. This solution was pumped automatically into a fluorometer equipped with a continuous flow cell and a strip chart recorder to monitor the fluorescence intensity of 1-naphthol present. Apples and carrots required an additional cleanup procedure prior to presentation to the automated steam distillation and fluorometer system. Of 20 crops tested, celery was the only one causing background interference even after use of the additional cleanup procedure. All of the other crops were rapidly screened for carbaryl plus 1-naphthol or for free 1-naphthol, depending upon the sample preparation procedure; the difference between the 2 assays represents the contribution from the carbaryl residue. The automated analytical system was operated at a rate of 20 samples/hr and the lower limit of detection for carbaryl was 0.2 ppm of the fortified crop.