The Stability of Carbamates in Blood Samples under Experimental Conditions

Abstract

Carbamate insecticides are the most prevalent compounds involved in cases of poisoned patients in Thailand. However, stability data of carbamate insecticides are relatively limited in literatures. This study investigated the stability of three common carbamate insecticides including carbaryl, carbofuran and propoxur under different temperature conditions. Pooled blood samples were spiked with carbaryl, carbofuran and propoxur at three concentration levels (low, medium and high). These compounds were analyzed for initial concentrations, they were stored both at room temperature (25°C) and in a refrigerator (4°C). Next, all samples were analyzed for these compounds on the 1st, 2nd, 3rd, 7th, 14th and 30th day at 25°C and on the 3rd, 7th, 14th, 30th, 60th, 90th and 180th day at 4°C. Descriptive statistics and one-way ANOVA were performed to investigate the changing trend of three compounds. Changing rates in three analyte concentrations at 25°C were significantly decreased by less than 15% from the initial concentrations on the 7th day to the 30th day (p<0.001). At 4°C, three analytes decreased significantly by less than 15% from initial concentrations on the 7th day to the 180th day (p<0.01). Carbofuran decreased at the fastest rate, followed by propoxur and carbaryl, respectively. In conclusion, carbaryl, carbofuran and propoxur were significantly unstable at 25°C and 4°C. Carbofuran was the most unstable compound, followed by propoxur and carbaryl, respectively. This suggested that blood samples from suspected carbamate poisoning cases should be collected and analyzed as soon as possible because these ordinary carbamate insecticides were unstable at room temperature and 4°C.