Modification of Gas-trap Apparatus of Commercial Arsenic Test Kit for Direct Determination of Total Arsenic in Dried Shrimps

Abstract

In this study, a gas trapping apparatus has been modified to measure the total arsenic concentration in dried shrimp samples by combining with a test kit developed by the Department of Chemistry, Faculty of Science, Mahidol University. The glass gas trapping apparatus was designed as a cylindrical bottle with an 8-cm height and a neck size of 2.5 cm. The designed apparatus had a higher efficiency in measuring the total arsenic content in dried shrimp samples than that containing the same type of bottle with different neck size. The efficiencies were compared among three different methods, namely, test kit using the designed gas trapping apparatus, spectrophotometric technique using molybdenum blue method, and Inductively Coupled Plasma-Optical Emission Spectroscopy technique. The effect of adding a masking agent into the dried shrimp samples prior to the analysis in order to reduce the background interference from the alkaline and alkaline earth elements was also studied. It was found that diethylenetriaminepentaacetic acid (DTPA) is the proper masking agent due to its ability to yield the higher total arsenic concentration. The total arsenic concentrations found in the same DTPA-added sample using the proposed three techniques were 5-10, 5.13 and 4.38 ppb, respectively. These were compared with those of the same sample obtained without DTPA addition of less than 5, 4.21 and 3.51 ppb, respectively.