Biological monitoring method for urinary neonicotinoid insecticides using LC-MS/MS and its application to Japanese...

Agricultural use of neonicotinoid (NEO) insecticides has been increasing in recent years, but their biological monitoring methods have been scarcely reported. In this study, we developed and validated a rapid and sensitive method for quantifying urinary NEO concentrations using high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS).

After phosphate-induced acidification of a urine sample, urinary NEOs were trapped by a solid-phase extraction column and eluted with methanol for acetamiprid, imidacloprid, thiacloprid, thiamethoxam, clothianidin and dinotefuran and with an acetonitrile and methanol solution (1:1, v/v) containing 5% NH3 for nitenpyram. A separation analysis was performed by LC-MS/MS within 10 minutes for the sample. This method was applied to first morning urine obtained from 52 Japanese (40.9 ± 10.5 years old, mean ± standard deviation) without occupational NEO exposure.

The linear dynamic ranges and their limit of quantification (LOQ, signal to noise ratio=10) levels were 0.3-20 or 50 µg/l (r=0.998-0.999) and 0.05-0.36 µg/l, respectively. The absolute recovery was 64-95%, and the intra- and inter-day precisions were less than 16.4% (relative standard deviation, %RSD). This method was successfully applied for analysis of NEOs in human urine samples obtained from 52 adults. The frequencies of individuals who showed more than LOD levels was above 90% for imidacloprid, thiamethoxam, clothianidin and dinotefuran, more than 50% for acetamiprid and thiacloprid and 29% for nitenpyram.

These results indicated that our new method could be applied to biological monitoring of NEO exposure even at environmental exposure levels in Japanese adults without occupational spraying histories.