Biomonitoring Equivalents for ethylene thiourea.

Ethylene thiourea, or ETU, is used in the rubber industry and is a degradation product and impurity in some fungicides. The general public may be exposed to low concentrations of residues of ETU in a variety of ways, including food treated with ethylene bis-dithiocarbamate (EBDC) fungicides or migration from rubber products. Biomonitoring of ETU in urine is useful for an assessment of integrated exposures to ETU across different sources and routes of exposure. In this evaluation, we review available health-based risk assessments and toxicological reference values (TRVs) for ETU and derive Biomonitoring Equivalent (BE) values for interpretation of population biomonitoring data. BEs were derived based on existing TRVs derived by Health Canada, yielding a BE of 27 µg of total ETU/L in urine associated with the Acceptable Daily Intake (ADI) and 6.7 µg/L associated with a 1e-6 cancer risk. These BEs are based on an analytical method that involves a digestion step to liberate conjugated ETU, thus producing 'total' ETU in urine. The BE values derived in this manuscript can serve as a guide to help public health officials and regulators interpret population based ETU biomonitoring data in a public health risk context.

A novel analytical approach for the determination of ethylene-thiourea and propylene-thiourea in vegetal foodstuffs by high-performance liquid chromatography hyphenated to inductively coupled plasma-tandem mass spectrometry.

This study reports a novel analytical approach for the simultaneous determination of ethylene-thiourea (ETU) and propylene-thiourea (PTU) in fruits and vegetables by (reverse phase) high-performance liquid chromatography (HPLC) coupled to inductively coupled plasma-tandem mass spectrometry (ICP-QQQMS or ICP-MS/MS). A baseline separation of ETU and PTU was achieved in less than 5 min. A robust method validation by using the accuracy profile approach was performed by carrying out four measurement series in duplicate at six different levels over a timespan of 4 weeks (different days). The recovery factors ranged from 87 to 101% for ETU and from 98 to 99% for PTU (depending on the spiking level). The coefficient of variation in terms of repeatability (CVr) ranged from 1 to 4.7% for ETU and from 1.8 to 3.9% for PTU (depending also on the analyte level) while the coefficient of variation in terms of intermediate reproducibility (CVR) ranged from 3.4 to 10% for ETU and from 1.8 to 10.8% for PTU. The limit of quantification was 0.022 mg kg-1 (wet weight) for ETU and 0.010 mg kg-1 (ww) for PTU. This novel approach was proved to be highly robust and suitable for the determination of ETU and PTU in foodstuffs of vegetal origin.

Assessment of Mancozeb Exposure, Absorbed Dose, and Oxidative Damage in Greenhouse Farmers.

Mancozeb (MNZ) is a fungicide commonly employed in many countries worldwide. This study assesses MNZ absorption dynamics in 19 greenhouse farmers, specifically following dermal exposure, aiming to verify the efficacy of both preventive actions and protective equipment. For data collection, a multi-assessment approach was used, which included a survey to record study population features. MNZ exposure was assessed through the indirect measurement of ethylene thiourea (ETU), widely employed as an MNZ biomarker. The ETU concentration was measured with the patch method, detecting environmental ETU trapped in filter paper pads, applied both on skin and working clothes, during the 8 h work shift. Urine and serum end-of-shift samples were also collected to measure ETU concentrations and well-known oxidative stress biomarkers, respectively, namely reactive oxygen metabolites (ROMs), advanced oxidation protein products (AOPPs), and biological antioxidant potential (BAP). It was observed that levels of ETU absorbed and ETU excreted were positively correlated. Additionally, working clothes effectively protected workers from MNZ exposure. Moreover, following stratification of the samples based on the specific working duty (i.e., preparation and spreading of MNZ and manipulation of MNZ-treated seedlings), it was found that the spreading group had higher ETU-related risk, despite lower chronic exposure levels. AOPP and ROM serum levels were higher in MNZ-exposed subjects compared with non-exposed controls, whereas BAP levels were significantly lower. Such results support an increase in the oxidative stress upon 8 h MNZ exposure at work. In particular, AOPP levels demonstrated a potential predictive role, as suggested by the contingency analysis results. Overall, this study, although conducted in a small group, confirms that ETU detection in pads, as well as in urine, might enable assessment of the risk associated with MNZ exposure in greenhouse workers. Additionally, the measurement of circulating oxidative stress biomarkers might help to stratify exposed workers based on their sensitivity to MNZ. Pivotally, the combination of both ETU measurement and biological monitoring might represent a novel valuable combined approach for risk assessment in farmhouse workers exposed to pesticides. In the future, these observations will help to implement effective preventive strategies in the workplace for workers at higher risk, including greenhouse farmers who are exposed to pesticides daily, as well as to clarify the occupational exposure levels to ETU.

Systematic review of human biomonitoring studies of ethylenethiourea, a urinary biomarker for exposure to dithiocarbamate fungicides.

Toxicological and epidemiological studies implicate exposure to dithiocarbamate (DTC) fungicides in adverse health outcomes. However, there is limited information about human exposure to these chemicals. This systematic review determined to which extent human populations worldwide, including children, pregnant women, and adults, are exposed environmentally or occupationally to DTC pesticides and how these exposures compare to the NHANES 2003-2008 population, using urinary ETU data as an outcome measure. PubMed, Embase, and SciFinder were searched using the keywords "ethylenethiourea" or CAS No.: 96-45-7, and urine or urinary. Duplicates and irrelevant studies were removed from the search results based on predetermined exclusion criteria. This screening process identified 17 relevant papers. One additional paper was found independent of this search. Data from studies were extracted using a pre-established data collection form. Ten, two, and five manuscripts reported urinary levels in environmentally exposed adults, children, and pregnant women, respectively. Median ETU levels ranged from 0.15 to 4.7 µg/g creatinine in adults (1994-2017), 0.24-0.83 µg/g creatinine in children (2011), and 2.6-5.24 ng/ml in pregnant women (2011). Eight studies reported urinary ETU levels in mostly agriculturally exposed populations, with median ETU levels ranging from 0.42 to 49.6 µg/g creatinine (1999-2011). With one exception, all studies were conducted between 1994 and 2011. ETU levels in the NHANES 2003-2008 population appeared to be generally lower than most studies identified in this review. This finding suggests that, historically, DTC fungicide exposures in the general population of high-income countries, such as the US, were low, whereas agricultural populations may have experienced higher exposure. Unfortunately, more recent exposure data are missing, especially in countries where DTC pesticides are not being phased out.

Establishing health-based biological exposure limits for pesticides: A proof of principle study using mancozeb.

Pesticides represent an economical, labor-saving, and efficient tool for pest management, but their intrinsic toxic properties may endanger workers and the general population. Risk assessment is necessary, and biological monitoring represents a potentially valuable tool. Several international agencies propose biological exposure indices (BEI), especially for substances which are commonly absorbed through the skin. Biological monitoring for pesticide exposure and risk assessment seems a natural choice, but biological exposure limits (BEL) for pesticides are lacking. This study aims at establishing equivalent biological exposure limits (EBEL) for pesticides using real-life field data and the Acceptable Operator Exposure Level (AOEL) of mancozeb as the reference. This study included a group of 16 vineyard pesticide applicators from Northern Italy, a subgroup of a more extensive study of 28 applicators. Their exposure was estimated using "patch" and "hand-wash" methodologies, together with biological monitoring of free ethylene-bis-thiourea (ETU) excretion in 24-h pre- and post-exposure urine samples. Modeling was done using univariate linear regression with ETU excretion as the dependent variable and the estimated absorbed dose as the independent variable. The median skin deposition of mancozeb in our study population was 125 µg, leading to a median absorbed dose of 0.9 µg/kg. The median post-exposure ETU excretion was 3.7 µg. The modeled EBEL for mancozeb was 148 µg of free ETU or 697 µg of total ETU, accounting for around 75% of the maximum theoretical excretion based on a mass balance model. Although preliminary and based on a small population of low-exposed workers, our results demonstrate a procedure to develop strongly needed biological exposure limits for pesticides.

[Determination of ethylenethiourea residues in tea using precolumn derivatization with ultra-performance liquid chromatography-tandem mass spectrometry].

A method based on precolumn derivatization along with ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was developed for the determination of ethylenethiourea residues in tea. The sample was extracted using acetonitrile; the extracting solution was purified by matrix-dispersed solid phase extraction and precolumn derivatization using 9-fluorenylmethyl chloroformate (FMOC-CL). The UPLC separation was carried out on an Acquity BEH C18 column (100 mm×2.1 mm, 1.7 µm) and quantified using the isotope internal standard method. The mobile phase was 0.1% (v/v) formic acid and acetonitrile. For tea samples, the detection limit of this method was 1.3 µg/kg and the limit of quantitation was 4.2 µg/kg. The recoveries were in the range 97.7%-107.5% with relative standard deviation (RSD) of 2.1%-10.0% (n=6). The linear correlation coefficient (r) was 0.9993 over the concentration range 1.0-203.4 µg/L. This method showed high sensitivity, good reproducibility, and qualitative and quantitative accuracy, and could be suitable for the detection of ethylenethiourea residues in tea.

Environmental and biological monitoring for the identification of main exposure determinants in vineyard mancozeb applicators.

Grapevine is a vulnerable crop to several fungal diseases often requiring the use of ethylenebisdithiocarbamate (EBDC) fungicides, such as mancozeb. This fungicide has been reported to have goitrogenic, endocrine disrupting, and possibly immunotoxic effects. The aim of this study was to assess workers' exposure in two scenarios of mancozeb application and analyse the main determinants of exposure in order to better understand their mechanism of influence. Environmental monitoring was performed using a modified Organisation for Economic Co-operation and Development (OECD) "patch" methodology and by hand-wash collection, while mancozeb's metabolite, ethylenethiourea (ETU), was measured in 24-h preexposure and postexposure urine samples. Liquid chromatography-mass spectrometry was used for determination of mancozeb and ETU in different kinds of samples. Closed tractor use resulted in 40 times lower potential exposure compared with open tractor. Coveralls reduced skin exposure 4 and 10 times in case of open and closed tractors, respectively. Gloves used during application resulted in 10 times lower hand exposure in open but increased exposure in closed tractors. This study has demonstrated that exposure to mancozeb is low if safe occupational hygiene procedures are adopted. ETU is confirmed as suitable biological marker of occupational exposure to mancozeb, but the absence of biological exposure limits significantly reduces the possibility to interpret biological monitoring results in occupationally exposed workers.

Iodine nutritional status and thyroid effects of exposure to ethylenebisdithiocarbamates.

INTRODUCTION: Italy is still characterized by a mild iodine deficiency and is among the most intensive users of chemical products for agriculture in Europe. The aim of this study was i) to evaluate thyroid effects of exposure to mancozeb, a fungicide widely used in agriculture, in a sample of Italian grapevine workers, and ii) to verify whether the iodine intake may modulate the risk of thyroid disruption due to the mancozeb metabolite ethylenthiourea (ETU). METHODS: One hundred seventy-seven occupationally exposed male workers (29 from Chianti, a mild iodine deficient area, and 148 from Bolzano an iodine sufficient province) and 74 non-occupationally exposed male controls (34 from Chianti and 40 from Bolzano) were enrolled in the study. Serum biomarkers of thyroid function, as well as urinary iodine and ETU concentrations were assessed. Moreover all the recruited subjects underwent clinical examination and thyroid ultrasound. RESULTS: Multivariate comparisons showed lower mean serum levels of FT4 in Chianti-workers as compared to Bolzano-workers. Moreover, an increased urinary iodine excretion (>250µg/L) was more frequently found among more exposed workers (ETU>20µg/L) than among less exposed ones and this effect was more pronounced in Chianti- than in Bolzano-workers. Chianti-workers also showed a significantly higher frequency of very low thyroid volume (≤6.0ml) as compared to controls. CONCLUSIONS: These findings showed a mild thyroid disrupting effect due to occupational exposure to mancozeb, more pronounced in workers residing in an area characterized by a mild to moderate iodine deficiency as compared to workers residing in an area covered by a long-lasting iodine prophylaxis program.

Manganese concentrations in drinking water from villages near banana plantations with aerial mancozeb spraying in Costa Rica: Results from the Infants' Environmental Health Study (ISA).

Elevated manganese (Mn) in drinking water has been reported worldwide. While, naturally occurring Mn in groundwater is generally the major source, anthropogenic contamination by Mn-containing fungicides such as mancozeb may also occur. The main objective of this study was to examine factors associated with Mn and ethylenethiourea (ETU), a degradation product of mancozeb, in drinking water samples from villages situated near banana plantations with aerial spraying of mancozeb. Drinking water samples (n = 126) were obtained from 124 homes of women participating in the Infants' Environmental Health Study (ISA, for its acronym in Spanish), living nearby large-scale banana plantations. Concentrations of Mn, iron (Fe), arsenic (As), lead (Pb), cadmium (Cd) and ethylenethiourea (ETU), a degradation product of mancozeb, were measured in water samples. Only six percent of samples had detectable ETU concentrations (limit of detection (LOD) = 0.15 µg/L), whereas 94% of the samples had detectable Mn (LOD = 0.05 µg/L). Mn concentrations were higher than 100 and 500 µg/L in 22% and 7% of the samples, respectively. Mn was highest in samples from private and banana farm wells. Distance from a banana plantation was inversely associated with Mn concentrations, with a 61.5% decrease (95% CI: -97.0, -26.0) in Mn concentrations for each km increase in distance. Mn concentrations in water transported with trucks from one village to another were almost 1000 times higher than Mn in water obtained from taps in houses supplied by the same well but not transported, indicating environmental Mn contamination. Elevated Mn in drinking water may be partly explained by aerial spraying of mancozeb; however, naturally occurring Mn in groundwater, and intensive agriculture may also contribute. Drinking water risk assessment for mancozeb should consider Mn as a health hazard. The findings of this study evidence the need for health-based World Health Organization (WHO) guidelines on Mn in drinking water.

Exposure to pesticide mixtures and DNA damage among rice field workers.

This study describes the use of pesticides mixtures and their potential association with comet assay results in 223 rice field workers in Colombia. Thirty-one pesticides were quantified in blood, serum, and urine (15 organochlorines, 10 organophosphorus, 5 carbamates, and ethylenethiourea), and the comet assay was performed. Twenty-four (77.42%) pesticides were present in the workers. The use of the maximum-likelihood factor analysis identified 8 different mixtures. Afterwards, robust regressions were used to explore associations between the factors identified and the comet assay. Two groups of mixtures--α-benzene hexachloride (α-BHC), hexachlorobenzene (HCB), and ß-BHC (ß: 1.21, 95% confidence interval [CI]: 0.33-2.10) and pirimiphos-methyl, malathion, bromophos-methyl, and bromophos-ethyl (ß: 11.97, 95% CI: 2.34-21.60)--were associated with a higher percentage of DNA damage and comet tail length, respectively. The findings suggest that exposure to pesticides varies greatly among rice field workers.

Ozonation and peroxone oxidation of ethylenethiourea in water: operational parameter optimization and by-product identification.

The objective of this work was to study the degradation and mineralization of ethylenethiourea (ETU) in water by ozonation at different pH values and in the presence of hydrogen peroxide. Degradation experiments were performed using an initial ETU concentration of 50 ppm for 180 min with a gas flux of 0.25 dm(3) min(-1) and an O3 production rate of 12.1 mg min(-1). Degradation of by-products was monitored by direct injection electrospray ionization mass spectrometry (ESI-MS), ETU concentration was determined by HPLC-UV, and its mineralization was detected by total organic carbon (TOC) analysis. Optimum degradation of ETU in water was observed at pH = 11, whereas at pH = 3, the degradation of ETU was slowest, indicating that the reaction occurred through different mechanisms. The additional effects of hydroxyl radicals formed at the highest pH can be used to explain the results obtained in this study. Peroxone experiments were carried out in the presence of 400 and 800 mg L(-1) H2O2; the degradation of ETU was faster at 400 mg L(-1) H2O2. This was attributed to the scavenging effect of the excess H2O2. ETU treatment by ozonation produced several by-products of degradation such as ethylene urea and 2-imidazoline.

Aerial application of mancozeb and urinary ethylene thiourea (ETU) concentrations among pregnant women in Costa Rica: the Infants' Environmental Health Study (ISA).

BACKGROUND: Mancozeb and its main metabolite ethylene thiourea (ETU) may alter thyroid function; thyroid hormones are essential for fetal brain development. In Costa Rica, mancozeb is aerially sprayed at large-scale banana plantations on a weekly basis. OBJECTIVES: Our goals were to evaluate urinary ETU concentrations in pregnant women living near large-scale banana plantations, compare their estimated daily intake (EDI) with established reference doses (RfDs), and identify factors that predict their urinary ETU concentrations. METHODS: We enrolled 451 pregnant women from Matina County, Costa Rica, which has large-scale banana production. We visited 445 women up to three times during pregnancy to obtain urine samples (n = 872) and information on factors that possibly influence exposure. We determined urinary ETU concentrations using liquid chromatography mass spectrometry. RESULTS: Pregnant women's median urinary ETU concentrations were more than five times higher than those reported for other general populations. Seventy-two percent of the women had EDIs above the RfD. Women who lived closest (1st quartile, < 48 m) to banana plantations on average had a 45% (95% CI: 23, 72%) higher urinary ETU compared with women who lived farthest away (4th quartile, ≥ 565 m). Compared with the other women, ETU was also higher in women who washed agricultural work clothes on the day before sampling (11%; 95% CI: 4.9, 17%), women who worked in agriculture during pregnancy (19%; 95% CI: 9.3, 29%), and immigrant women (6.2%; 95% CI: 1.0, 13%). CONCLUSIONS: The pregnant women's urinary ETU concentrations are of concern, and the principal source of exposure is likely to be aerial spraying of mancozeb. The factors predicting ETU provide insight into possibilities for exposure reduction.

Combined determination and confirmation of ethylenethiourea and propylenethiourea residues in fruits at low levels of detection.

In this work, a new method for the determination of ethylenethiourea (ETU) and propylenethiourea (PTU) in fruits and vegetables is presented. Different extraction and purification techniques, including matrix solid phase dispersion (MSPD) and solid-liquid extraction (SLE), followed by a clean-up step by solid phase extraction (SPE), were compared. The determination of ETU and PTU was performed by high performance liquid chromatography with diode array detection (HPLC/DAD) or by gas chromatography with mass spectrometry detection (GC/MS). The effect of several parameters on the extraction, separation and detection was studied. The proposed method based on solid-liquid extraction with acetonitrile, clean-up with Envicarb II/PSA cartridges and subsequent analysis by HPLC/DAD was characterised and applied to the analysis of fruits and vegetables from different countries. Analytes recoveries were between 71% and 94% with relative standard deviations (RSDs) ranging from 8% to 9.5%. Quantification limits obtained for ETU and PTU with the HPLC/DAD method were 7 and 16 µg kg⁻¹ in strawberries (fresh weight), respectively. For apples, they were 11 and 25 µg kg⁻¹, respectively.

Pesticide risk perception and biomarkers of exposure in Florida female farmworkers.

OBJECTIVE: To compare workplace characteristics, workplace behaviors, and the health beliefs of female farmworkers of childbearing age with actual biomarkers of exposure to organophosphate pesticides and to the fungicide mancozeb. METHODS: Hispanic and Haitian farmworkers between the ages of 18 and 40 years working in nursery or fernery operations were recruited to participate in a cross-sectional survey, examining demographics, work practices, work-related hygiene, and pesticide exposure beliefs. Single-void (spot) urine samples were analyzed for organophosphate and ethylenethiourea metabolites. RESULTS: Women in nurseries worried less frequently about the effects of pesticides on their health than those in fernery operations. In summary, organophosphate and ethylenethiourea levels in nursery workers were significantly higher than levels in fernery workers and the control group. CONCLUSIONS: Results showed that perceived pesticide exposure did not correspond to actual metabolite levels within differing agricultural subpopulations.

High-throughput method for the analysis of ethylenethiourea with direct injection of hydrolysed urine using online on-column extraction liquid chromatography and triple quadrupole mass spectrometry.

Ethylenethiourea (ETU) is of major toxicological concern, since in experimental animal studies, ETU has shown a large spectrum of adverse effects. High occupational exposure can be found among agricultural workers or during manufacturing of ethylenbisdithiocarbamates (EBDC). For the general public, sources of environmental exposure may be residues of ETU in commercial products, food and beverages. For the determination of ETU in human urine we present a high-throughput online on-column extraction liquid chromatography triple quadrupole mass spectrometry method using direct injection of hydrolysed urine samples. This method is simple, user- and environmentally friendly and all sample preparation is performed in 96-well plates. A labelled ETU internal standard was used for quantification. The method showed a good sensitivity with a limit of quantification (LOQ) of 0.5ng ETU/mL urine and the calibration curve was linear in the range 0.25-200ng ETU/mL urine. The within-run, between-run and between-batch precision was between 6% and 13%. Alkaline hydrolysis considerably increased the levels of ETU indicating a potential conjugate. The method was applied in an experimental dermal exposure study in humans, with sample concentrations ranging from 0.4 to 5.0ng ETU/mL urine. The excretion in urine was 10% of the applied dose. The elimination profile seemed to differ between the two individuals. The results show an estimated half-life of ETU between 34 and 72h. Although the experiment is limited to two individuals, the data provide valuable and new information regarding the toxicokinetics of ETU after dermal exposure.

Development and validation of ethylenethiourea determination in foods using methanol-based extraction, solid-phase extraction cleanup and LC-MS/MS.

To response to the need for a rapid, cost-effective, eco-friendly and efficient extraction process, a sensitive method for the determination of ethylenethiourea (ETU) in food matrices by high-performance liquid chromatography-mass spectrometry (HPLC-LC/MS) was developed and validated. ETU was extracted from food commodities with methanol, cleaned up by alumina-SPE column, and then determined by HPLC-MS/MS. The MS detection was operated in positive ionization mode. For confirmation of target compound, two precursor ion>product ion transitions were selected by multi-reaction monitoring mode (MRM). The method showed good linearity with correlation coefficient higher than 0.9950. Recoveries at three spiked levels (10, 50, 100 ng/g) in random selected food matrices were in range of 71-121% with RSDs not larger than 25%. The limit of quantitation for the analyte was estimated at 5 ng/g.

A rapid determination method for ethylenethiourea in potato and cucumber by modified QuEChERS - high performance liquid chromatography-tandem mass spectrometry.

A rapid and sensitive analytical method for the determination of ethylenethiourea (ETU) in potatoes and cucumbers is developed. This method employs modified QuEChERS followed by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) analysis. ETU was extracted by alkaline acetonitrile (containing 1%NH(3).H(2)0), separated on a ZIC-pHILIC column, confirmed by multiple reaction monitoring (MRM) mode with electrospray ionisation source. This modified procedure showed satisfactory recovery (90.6-103.5%) fortified at the range of 0.005-0.05 mg kg(-1) with relative standard deviation (RSD)<7%. The limits of detection (LOD) and the limits of quantification (LOQ) were 0.002 mg kg(-1) and 0.005 mg kg(-1), respectively. Matrix effect and HILIC retention mechanism were also evaluated. The method was finally applied to detect ETU in potato and cucumber samples collected at harvest period. Residues of ETU were detected in four cucumber samples with the level lower than LOQ.

Liquid chromatography coupled to tandem mass spectrometry for the residue determination of ethylenethiourea (ETU) and propylenethiourea (PTU) in water.

Ethylenethiourea (ETU) and propylenethiourea (PTU) are the main degradation products of dithiocarbamates fungicides, which are widely used in agriculture from several years ago. Their determination in water at low concentrations (e.g. sub-ppb levels) is highly problematic due to their polar character and low molecular size. In the present study, two analytical methodologies have been developed and compared for the selective and sensitive determination of ETU and PTU in various types of waters. Both approaches are based on liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) with electrospray ionization, using triple quadrupole analyzer. Whereas the first methodology used an on-line solid-phase extraction (SPE) step in order to reach the adequate sensitivity, the second one avoided sample treatment and was based on direct injection into an ultra high performance liquid chromatography (UHPLC-MS/MS) system, making use of a new-generation instrument in order to reach sub-ppb analyte levels in water. Strong matrix effects (typically leading to signal enhancement) were observed for most of the evaluated waters, especially when applying the on-line SPE method, surely due to the higher amount of sample injected into the system. The use of the own analyte (ETU-d4)) as isotope-labelled internal standard (ILIS) allowed to compensate these effects and to achieve an accurate ETU quantification at low concentrations. Moreover, three simultaneous transitions, operating in selected reaction monitoring mode, were acquired for both ETU and ETU-d4. This fact together with the evaluation of their relative intensity ratios assured the reliable identification of the analyte in the water samples. The two optimized methodologies were validated by analysis of six different samples (two drinking water, two groundwater and two surface water), spiked at two levels (0.1 and 1.0 µg/L), and analyzed each in quintuplicate. Satisfactory accuracy and precision, with recoveries ranging from 73 to 104% and RSDs lower than 20%, were obtained for ETU. Limits of detection for ETU were found to be 0.058 µg/L and 0.027 µg/L with direct injection and with the on-line methodology, respectively. No satisfactory recoveries were obtained, in general, for PTU despite using its own deuterium-labelled molecule for matrix effects correction. Notable differences in the chemical behaviour between PTU and PTU-d6 were observed, which lead to significant variation in their chromatographic retention time and ionization efficiency. Thus, no satisfactory correction of matrix effects could be reached illustrating that the use of deuterated ILIS can be problematic in some particular cases. Despite the poor correction, a semi-quantitative analysis would be feasible for PTU at sub-ppb levels in water. To the best of our knowledge, this is the first article reporting the use of LC-MS/MS for the trace level determination of these problematic analytes in water.

[Improvement of 2-mercaptoimidazoline analysis in rubber products containing chlorine].

An improved analysis method for 2-mercaptoimidazoline in rubber products containing chlorine was developed. 2-Mercaptoimidazoline (20 µg/mL) is detected by means of TLC with two developing solvents in the official method. But, this method is not quantitative. Instead, we employed HPLC using water-methanol (9 : 1) as the mobile phase. This procedure decreased interfering peaks, and the quantitation limit was 2 µg/mL of standard solution. 2-Mercaptoimidazoline was confirmed by GC-MS (5 µg/mL) and LC/MS (1 µg/mL) in the scan mode. For preparation of test solution, a soaking extraction method, in which 20 mL of methanol was added to the sample and allowed to stand overnight at about 40°C, was used. This gave similar values to the Soxhlet extraction method (official method) and was more convenient. The results indicate that our procedure is suitable for analysis of 2-mercaptoimidazoline. When 2-mercaptoimidazoline is detected, it is confirmed by either GC/MS or LC/MS.