Abstract

False Positive (FP) results of the detection of organophosphorus or carbamate pesticides in sulfur-containing vegetables are the primary issue using acetylcholineesterase (AchE), because the activities of AchE were inhibited by the produced sulfides. An improved pretreatment for reducing the FP results is proposed in this paper. It was exposed by a series of experiments that the alkaline sample at pH8.5~9 can reduce the FP results for three kinds of vegetables: leek, onion and garlic. The results of pesticides detection in vegetable solutions was mostly consistent with in buffer solution. 8 kinds of pesticides were detected in the vegetables solutions at pH8.5 with 91.7 percent consistency with in buffer at pH7.5. So, the method is available and convenient for the rapid detection.

INTRODUCTION

Recently, food security has been a critical issue in more and more countries, especially in developing countries (1). Rapid screening methods including novel detection technologies and corresponding test paper, kits, instruments and so on were necessary to be researched and developed.
Sulfur-containing vegetables were exposed under critical pesticides pollution. For example, the roots of leeks were irrigated using phorate against bradysia odoriphaga in many countries. The phorate residue was high and deathful for human. However, rapid detection of pesticides for most sulfur-containing vegetables was difficult owing to the disturbance from its by-product- sulfides.
The precise determination methods of pesticide residues are based on gas chromatography (GC) or high performance liquid chromatography (HPLC) (Molina, Honing, & Barcelo (2), 1994; Sherma & Zweig, 1972 (3)), so GC and HPLC were used for standard method in most countries and unions (4, 5). However, GC or HPLC is not available for rapid detection and screening. Enzyme-linked immunosorbent assay (ELISA) is a popular rapid detection method owing to its high accur ...