[Improved methodology for quantitative determination of thiabendazole].

The method prescribed in the 8th edition of Japan's Specifications and Standards for Food Additives (JSSFA) for the quantitative analysis of thiabendazole was improved by eliminating the use of toxic reagents such as mercuric acetate and chromium trioxide. For exclusion of mercuric acetate, a nonaqueous titration was performed using four types of solvent systems, including acetic acid:acetic anhydride (1:5), acetic acid:acetic anhydride (3:7), acetic acid alone, and formic acid:acetic acid (1:10), that did not contain mercuric compounds. Because precipitates were formed in titrations using acetic acid alone and formic acid:acetic acid (1:10), we considered that it was difficult to determine the purity using these solvent systems. However, it was confirmed that the purity of thiabendazole dissolved in the two acetic acid:acetic anhydride solvent systems can be determined using either a visual indicator or potentiometry. Specifically, the purity of thiabendazole was determined to be 99.9% (relative standard deviation (RSD) = 0.07%) for acetic acid:acetic anhydride (1:5) and 99.7% (RSD = 0.13%) for acetic acid:acetic anhydride (3:7) With respect to chromium trioxide, it was determined that chromium trioxide can be excluded using acetic acid, which conforms to the JIS K8001 standard for nonaqueous titrations. Therefore, in this study, an improved method for the quantitative determination of thiabendazole was developed without the use of toxic reagents.