Analytical method for the quantitative determination of urinary ethylenethiourea by liquid chromatography/electrospray ionization tandem mass spectrometry

Abstract

A direct, rapid and selective method for the quantitative determination of the ethylenethiourea (ETU) in human urine has been validated and is reported in the present study. It allows the accurate quantification of ETU in this complex matrix without the use of any internal standard as the sample cleanup is effective enough for the removal of interferences that could lead to ion suppression in the electrospray ionization (ESI) source. This simple and rapid purification system, based on the use of a Fluorosil phase of a BondElut column followed by a liquid-liquid extraction procedure, achieves mean extracted recoveries, assessed at three different concentrations (2.5, 10.0, and 25.0 microg/L), always more than 85%. High-performance liquid chromatography (HPLC) with positive ion tandem mass spectrometry, operating in selected multiple reaction monitoring (MRM) mode, is used to quantify ETU in human urine. The assay is linear over the range 0-50 microg/L, with a lower limit of quantification (LOQ) of 1.5 microg/L and a coefficient of variation (CV) of 8.9%. The lower limit of detection (LOD) is assessed at 0.5 microg/L. The overall precision and accuracy were determined on three different days. The values for within- and between-day precision are < or = 8.3 and 10.1%, respectively, and the accuracy is in the range 97-118%. The relative uncertainties for the LOQ and QC concentrations have been estimated to be 18 and 8%, respectively. The assay was applied to quantify ETU in human urine from growers that regularly handle ethylenebisdithiocarbamate pesticides in large crop plantations. The biological samples were collected at the start and end of the working day, and the ETU urine levels were found to vary between 1.9 and 8.2 microg/L.

Effect of household and industrial processing on levels of five pesticide residues and two degradation products in spinach

“…This decrease could be explained by its pronounced water solubility. These results are consistent with previous studies (Kaushik et al, 2009;Timme & Walz-Tylla, 2004). It was indeed demonstrated that surface residues are amenable to simple washing operations whereas systemic residues present in tissues will only be affected to a limited extend.…”

“…It was indeed demonstrated that surface residues are amenable to simple washing operations whereas systemic residues present in tissues will only be affected to a limited extend. Polar, water-soluble pesticides are more readily removed than low-polarity materials (Burchat et al, 1998;Holland et al, 1994;Timme & Walz-Tylla, 2004). The effectiveness of washing in removing residues depends on the location, the water solubility of the pesticide and the temperature of the wash.…”

“…Typical operations employed in processing food crops such as washing, peeling, blanching and cooking play a role in the reduction of residues (Holland, Hamilton, Ohlin, & Skidmore, 1994;Kaushik, Satya, & Naik, 2009;Timme & Walz-Tylla, 2004). It is expected that fruits and vegetables contain higher pesticide residue levels compared to other foods of plant origin, such as bread based on cereal processing, because they are mainly consumed raw or semi-processed (Berrada et al, 2010;Chen et al, 2011;Claeys et al, 2011;Kaushik et al, 2009;Rasmusssen, Poulsen, & Hansen, 2003).…”

“…It is expected that fruits and vegetables contain higher pesticide residue levels compared to other foods of plant origin, such as bread based on cereal processing, because they are mainly consumed raw or semi-processed (Berrada et al, 2010;Chen et al, 2011;Claeys et al, 2011;Kaushik et al, 2009;Rasmusssen, Poulsen, & Hansen, 2003). Conversely, processing can also result in a higher residue concentration, for example, as a result of the loss of water during processing (Timme & Walz-Tylla, 2004). Furthermore, in some special cases, more toxic by-products or metabolites can be formed during processing (Holland et al, 1994).…”

“…Ethylenebisdithiocarbamates (EBDCs), which are not highly toxic contact fungicides, can be degraded to the more toxic ethylenethiourea (ETU). Levels of ETU can increase when products are processed, especially during cooking (Dubey, Heberer, & Stan, 1997;Hwang, Cash, & Zabik, 2003;Kontou, Tsipi, Oreopoulou, & Tzia, 2001;Sottani, Bettinelli, Fiorentino, & Minoia, 2003).…”