The stable isotope fingerprinting technique for agricultural pesticide

Abstract:

The compound specific isotope analysis (CSIA) is nowadays an important and powerful tool in geochemical, environmental, and forensics field. In particular, the stable isotope ratio of pesticide is applied to biological process and reaction in the soil and distribution channel as forensics science. The aim of this study is to measure the stable isotope ratios of pesticide using various analytical methodologies, GC/IRMS, EA/IRMS, and LC/IRMS under high accuracy and precision. Therefore, these methods seemed to be important knowledge as geological field.

In particular case, we present the method to measure carbon isotope ratio of nine malathion emulsion pesticides using GC/IRMS with cryo-focusing system to identify the source. In December 2013, food poisoning occurred after eating frozen dumplings (i.e., pizza and chicken nuggets) in Japan. There was a very high concentration, maximum value 15,000ppm, of malathion (diethyl (dimethoxythiophosphorylthio) succinate) in products. This incident was caused by an employee of process, and threatened the food safety. We analyzed the δ¹³C of malathion ranged from −30.63‰ to −29.54‰ (S.D. 0.10‰), the differences less than 1.0‰. All malathion emulsion sold in Japan are imported from Cheminova India Lat., Denmark to Sumitomo Chemical Co. Ltd., Japan. After that, Japanese each manufacture buy from Sumitomo Chemical Co. Ltd. And blended malathion and organic solvent (ethylbenzene and xylene). Therefore, ethylbenzene and xylene may be important tool as source identification. We measured the δ¹³C of ethylbenzene and m-,p-xylene, too. As the results, the δ¹³C of ethylbenzene and m-,p-xylene ranged from −28.20‰ to −20.84‰ (S.D. 0.16‰), −28.69‰ to −25.15‰ (S.D. 0.13‰), respectively. The δ¹³C of ethylbenzene and m-,p-xylene can be identified manufacture, although the δ¹³C of malathion indicated same value.

In addition, we measured five pesticides (acephate, acetamiprid, glufosinate, glyphosate, and oxamyl) using EA/IRMS and LC/IRMS. The correlation coefficient between EA/IRMS and LC/IRMS is 0.97. The detail results will be presented in this conference.