Ultrahigh-performance liquid chromatography-tandem mass spectrometry quantitation of o-cresol in hydrolyzed human urine to assess toluene exposure.

RATIONALE: Toluene is a volatile organic compound used in domestic and industrial applications. The main routes of workplace exposure to toluene are inhalation and dermal contact. As toluene exposure can cause severe nervous system damage, its quantification is crucial to prevent occupational illness. Toluene is metabolized mainly as hippuric acid, S-benzylmercapturic acid and epoxides. These are rapidly converted to o-/p-cresol, which is then excreted in the urine as conjugated glucuronides and sulfates. o-Cresol and its conjugates can be chemically hydrolyzed to form free o-cresol, which can then serve as a urinary biomarker of toluene exposure. Current analytical methods for quantifying o-cresol in hydrolyzed urine are, however, either weakened by interference, are not sensitive enough or require water-sensitive sample preparation. Development of a liquid chromatography-tandem mass spectrometry method for assessing exposure to toluene is thus required. METHOD: Urine samples were acidified and heated to form free o-cresol and then derivatized with dansyl chloride and diluted. Extracts were separated by reverse-phase chromatography on a BEH phenyl column and then analyzed using a triple quadrupole instrument in selected reaction monitoring mode. RESULTS: The dansyl chloride derivatization step was optimized to produce the derivative within a reaction time of 3 min. Hydrolysis efficiency in forming free o-cresol from conjugated metabolites was evaluated using o-cresol-ß-d-glucuronidespiked human urine: complete hydrolysis occurred in 45 min. Dynamic range was 0.4 to 40 µM, and the method was useful for toluene monitoring in non-occupational (0.1 µmol/mmol creatinine) as well as occupational (0.3 µmol/mmol creatinine) exposure. The calculated limit of detection and limit of quantitation of the method were 0.06 and 0.21 µM, respectively. Intraday and interday precisions were 3.2% and 4.4%, respectively. Method accuracy was established as 99% using ClinChek® urine controls. CONCLUSION: An ultrahigh-performance liquid chromatography-tandem mass spectrometry method for analysis of o-cresol was developed for biological monitoring of toluene exposure in human urine. This is the method of choice used by occupational health and safety practitioners in the province of Québec, Canada.

Development of a new SPE UPLC-MS/MS method for extraction and quantitation of toluene diamine on gloves following toluene diisocyanate exposure.

RATIONALE: Toluene diisocyanate (TDI) is a highly reactive isocyanate commonly used as a mixture of 2,4- and 2,6- isomers in the production of flexible foams. Exposure to TDI occurs primarily through vapour inhalation in workplaces where TDI is produced or used, but dermal exposure is also possible during some tasks. To ensure workplace safety, accurate monitoring of TDI and toluene diamine (TDA) levels is required. Methods of quantifying field effectiveness of gloves in preventing dermal exposure have not been established. Therefore, there is a need to develop a new practical method for assessing glove effectiveness for TDI/TDA. METHOD: A new offline SPE UPLC-MS/MS method for the quantitation of TDA isomers from TDI-exposed gloves was developed. Gloves were dipped in a solution of 1% acetic acid leading to a full conversion to TDA. TDA-free amine compounds were derivatized with acetic anhydride to increase chromatographic retention and signal intensity. RESULTS: 2,4-Diaminotoluene-α, α, α-d3 (2,4-d3 -TDA) was selected as a surrogate standard to minimise the variability in sample preparation and instrumental sensitivity. The choice of UPLC-MS/MS operated in multiple reaction monitoring (MRM) mode allowed to reach much lower limits of detection (LOD). The LOD of the method was 6.86 and 2.83 ng/mL (0.03 and 0.01 µg) for 2,6-TDA and 2,4-TDA, respectively. The limit of quantitation (LOQ) was 22.85 and 9.42 ng/mL (0.11 and 0.05 µg) for 2,6-TDA and 2,4-TDA, respectively. CONCLUSION: A new UPLC-MS/MS analytical method has been developed to determine field effectiveness of gloves for preventing dermal exposure to TDI/TDA. The new technique overcomes some limitations for measuring putative dermal exposure to isocyanates and may be useful in exposure monitoring and future research on isocyanate health risks.

Surface contamination with nine antineoplastic drugs in 109 canadian centers; 10 years of a monitoring program.

INTRODUCTION: Healthcare workers exposure to antineoplastic drugs can lead to adverse health effects. Guidelines promote the safe handling of antineoplastic drugs, but no safe exposure limit was determined. Regular surface sampling contributes to ensuring workers safety. METHODS: A cross-sectional monitoring is conducted once a year with voluntary Canadian centers, since 2010. Twelve standardized sampling sites were sampled. Samples were analyzed by high performance mass coupled liquid chromatography. The limits of detection (in ng/cm2) were: 0.001 for cyclophosphamide and gemcitabine; 0.3 for docetaxel and ifosfamide; 0.04 for 5-fluorouracil and paclitaxel; 0.003 for irinotecan; 0.002 for methotrexate; 0.01 for vinorelbine. RESULTS: The surfaces from 109 centers were sampled between 01/01/2020-18/06/2020. Twenty-six centers delayed their participation because of the COVID-19 pandemic. 1217 samples were analyzed. Surfaces were frequently contaminated with cyclophosphamide (34% positive, 75th percentile 0.00165 ng/cm2) and gemcitabine (16% and <0.001 ng/cm2). The armrest of patient treatment chairs (84% to at least one drug), the front grille inside the biological safety cabinet (BSC) (73%) and the floor in front of the BSC (55%) were frequently contaminated. Centers that prepared ≥5000 antineoplastic drugs annually had higher concentration of cyclophosphamide on their surfaces (p < 0.0001). Contamination measured on the surfaces was reduced from 2010 to 2020. CONCLUSIONS: This large-scale study showed reproducible long term follow up of the contamination of standardized sites of Canadian centers and a reduction in surface contamination from 2010 to 2020. Periodic surface sampling help centers meet their continuous improvements goals to reduce exposure as much as possible. The COVID-19 pandemic had a limited impact on the program.

Evaluation of decontamination efficacy of four antineoplastics (ifosfamide, 5-fluorouracil, irinotecan, and methotrexate) after deliberate contamination.

The main objective was to determine the decontamination efficacy of quaternary ammonium, 0.1% sodium hypochlorite, and water after deliberate contamination with four antineoplastics (ifosfamide, 5-fluorouracil, irinotecan, methotrexate). A stainless-steel surface was deliberately contaminated with ifosfamide (15 µg), 5-fluorouracil (10 µg), irinotecan (1 µg), and methotrexate (1 µg). First, a single decontamination step with either water, quaternary ammonium, or 0.1% sodium hypochlorite was tested. Then, the effect of up to four successive decontamination steps with either quaternary ammonium or 0.1% sodium hypochlorite was tested. Commercial wipes consisting of two layers of non-woven microfibers with an inner layer of highly absorbent viscose fibers were used. Triplicate surface samples were obtained and tested by ultra-performance liquid chromatography tandem mass spectrometry. The limits of detection were 0.004 ng/cm2 for ifosfamide, 0.040 ng/cm2 for 5-fluorouracil, 0.003 ng/cm2 for irinotecan, and 0.002 ng/cm2 for methotrexate. After a single decontamination step, the 0.1% sodium hypochlorite eliminated 100% of contamination with 5-fluorouracil, irinotecan, and methotrexate and 99.6 ± 0.5% of ifosfamide contamination. Quaternary ammonium and water also removed 100% of the 5-fluorouracil, and 99.5% to 99.9% of the other three antineoplastics. For ifosfamide, irinotecan, and methotrexate, the decontamination efficacy increased with successive decontamination steps with quaternary ammonium. 5-fluorouracil was undetectable after a single decontamination step. Methotrexate was the only drug for which decontamination efficacy was less than 100% after four decontamination steps. 100% decontamination efficacy was achieved from the decontamination step with 0.1% sodium hypochlorite for 5-fluorouracil, irinotecan, and methotrexate. For ifosfamide, 100% efficacy was achieved only after the third decontamination step. It was possible to make all traces of antineoplastic undetectable after deliberate contamination with 5-fluorouracil, irinotecan, and methotrexate with a 0.1% chlorine solution; up to three decontamination steps were needed to make ifosfamide undetectable. Water or quaternary ammonium removed more than 99.5% of deliberate contamination. In several scenarios, it was necessary to repeat the decontamination to eliminate residual traces. More work is needed to identify the optimal decontamination approach for all of the antineoplastic drugs used.

A validated UPLC-MS/MS method for the determination of aliphatic and aromatic isocyanate exposure in human urine.

4,4'-Methylenediphenyldiisocyanate (MDI), toluenediisocyanate (2,4-TDI and 2,6-TDI), and 1,6'-hexamethylenediisocyanate (HDI) are all commonly used in the production of polyurethane-containing materials in different application areas. Workers exposed occupationally to these compounds may develop sensitization with the potential to lead to asthma. Isocyanates are metabolized in vivo by conjugation to macromolecules and/or by acetylation prior to being eliminated in urine. The hydrolysis of urine samples releases free amine compounds from these metabolites as biomarkers of exposure, specific to each parent isocyanate: 4,4'-methylenedianiline (MDA), toluenediamine (2,4-TDA and 2,6-TDA), and hexamethylenediamine (HDA). To address the need for a validated method that could be used for the simultaneous determination of biomarkers of aliphatic and aromatic isocyanates to monitor occupational exposure based on recommended thresholds, we have developed an UPLC-MS/MS method for the quantitation of MDA, TDA isomers, and HDA following acid hydrolysis, solid-phase extraction, and derivatization of urine samples. Free amine compounds were derivatized with acetic anhydride to augment chromatographic retention and signal intensity. The method was developed considering the biological guidance value (BGV) of MDA at 10 µg L-1, and biological exposure indices (BEI) of TDA isomers and HDA at 5 µg g-1 and 15 µg g-1 creatinine, respectively. Limits of detection allowed monitoring down to 6% of BGV/BEI, with precision within 8%. The accuracy and reliability of the method were assessed using inter-laboratory reference samples and deemed acceptable based on three rounds of measurements. This novel method has therefore been proven as useful for occupational safety and health assessments. Graphical Abstract.

Cross-sectional evaluation of surface contamination with 9 antineoplastic drugs in 93 Canadian healthcare centers: 2019 results.

INTRODUCTION: The primary objective was to describe environmental contamination with National Institute for Occupational Safety and Health Group 1 hazardous drugs in oncology pharmacies and outpatient clinics in Canada in 2019, as part of an annual surveillance project. METHODS: In each participating center, 12 standardized sites (6 in the oncology pharmacy and 6 in outpatient clinic) were sampled. Each sample was prepared to allow quantification of six antineoplastic drugs (cyclophosphamide, ifosfamide, methotrexate, gemcitabine, 5-fluorouracil, and irinotecan) by ultra-performance liquid chromatography-tandem mass spectrometry. Samples were also tested for three additional antineoplastic drugs (docetaxel, paclitaxel, and vinorelbine) without quantification. The impact of certain characteristics of the sampling sites was evaluated with a Kolmogorov-Smirnov test for independent samples. RESULTS: Ninety-three Canadian centers participated in 2019, with a total of 1045 surfaces sampled. Cyclophosphamide was the drug most often found in the surface samples (32.4% of samples with positive result), followed by gemcitabine (20.3%). The front grille inside the biological safety cabinet (81.5% of samples positive for at least one antineoplastic drug) and the armrest of a treatment chair (75.8%) were the most frequently contaminated surfaces. Centers with more oncology inpatient and outpatient beds, those that prepared more antineoplastic drugs each year, and those that used more cyclophosphamide each year had higher concentrations of cyclophosphamide contamination on the surfaces tested (p < 0.0001). CONCLUSION: Traces of dangerous drugs were found in oncology pharmacies and oncology outpatient clinics in 93 Canadian hospitals in 2019. However, the quantities measured were very small. Every healthcare worker should consider these work areas to be contaminated and should wear appropriate protective equipment.

Quantification of healthcare workers' exposure to cyclophosphamide, ifosfamide, methotrexate, and 5-fluorouracil by 24-h urine assay: A descriptive pilot study.

PURPOSE: The objective of this pilot study was to determine the frequency of urination and the concentration of four hazardous drugs (cyclophosphamide, ifosfamide, methotrexate, and fluorouracil) in workers' 24-h urine samples in relation to exposure to traces with hazardous drugs. METHODS: The study was conducted in three healthcare centers in the region of Montréal, Quebec, Canada. We recruited healthcare workers (nurses and pharmacy technicians) assigned to the hematology-oncology department. Each participant was asked to collect all urine voided during a 24-h period, to fill out an activity journal documenting tasks performed and to document the use of personal protective equipment. Samples were analyzed for cyclophosphamide, ifosfamide, methotrexate, and alpha-fluoro-beta-alanine (FBAL, the main urinary metabolite of 5-fluorouracil). Drugs were quantified by ultra-performance liquid chromatography-tandem mass spectrometry (positive electrospray MRM mode). RESULTS: Eighteen healthcare workers (10 nurses and 8 technicians) were recruited and provided consent to participate. Urine samples were obtained between 1 September and 30 September 2019. The number of urinations over the 24-h collection period ranged from 3 to 11 per participant. A total of 128 urine samples were analyzed for the 18 workers. All urine samples were negative for the four antineoplastics tested. CONCLUSION: No traces of cyclophosphamide, ifosfamide, methotrexate, or FBAL were found in the 24-h urine samples of 18 healthcare workers practicing in three healthcare facilities in Quebec. Although it was feasible to collect 24-h urine samples in this research project, it appears unrealistic to do so recurrently as part of a large-scale surveillance program.

On-site comparison of the OSHA 47, Asset EZ4-NCO, Iso-Chek, DAN, and CIP10 methods for measuring methylene diphenyl diisocyanate (MDI) at an oriented-strand board (OSB) factory.

Diisocyanates are occupational contaminants and known sensitizers causing irritation (skin and respiratory tract) as well as occupational asthma. Because of their physicochemical properties (semi-volatile and high reactivity) and low occupational limits, diisocyanate exposure evaluation is still a challenge nowadays for industrial hygienists and laboratories. The objective of this study was to compare the methylene diphenyl diisocyanate (MDI) concentrations measured by five methods using different collection or derivatization approaches in an oriented-strand board (OSB) factory. The methods used were: OSHA 47 (filter, 1-(2-pyridyl)piperazine) (OSHA), Asset EZ4-NCO (denuder and filter, dibutylamine) (Asset), Iso-Chek (double-filter, 9-(N-methylaminomethyl) anthracene and 1,2-methoxyphenylpiperazine), DAN (filter, 1,8-diaminonaphthalene), and CIP10 (centrifugation, 1,2-methoxyphenylpiperazine). Real-time monitoring of particle concentration and size distribution was performed to explain the potential bias between methods. The comparison study was performed over 3 consecutive days, generating at least 18 replicates for each of the 5 methods. The results of each methods were compared using linear mixed effect modeling. Compared to Asset, which yielded the highest concentrations overall, the OSHA method provided the smallest bias with -18% (95% CI [-61;24]) (not significant) for MDI monomer and the DAN method provided the smallest bias with -30 (95% CI [-70;9]) (not significant) for Total Reactive Isocyanate Group (TRIG). The CIP10 and Iso-Chek methods provided the largest biases for MDI monomer (-83% (95% CI [-115;-51]) and -78% (95% CI [-110;-46]), respectively) as well as for TRIG (-87% (95% CI [-120;-55]) and -75% (95% CI [-107;-44]), respectively). The underestimations of the CIP10 and Iso-Chek were explained by its inefficient sampling principle for fines particles and the use of a non-impregnated filter to collect aerosol MDI, respectively. This study confirms that impregnated filter, including denuding device such as the Asset EZ4-NCO sampler, collects the MDI-coated wood particles and MDI vapor with similar efficiency. It also demonstrates for the first time in this type of MDI emission a significant agreement for TRIG concentration between the DAN method in the impregnated filter configuration and an international standard one such as Asset.

On site comparison of the OSHA 42, Asset EZ4-NCO, Iso-Chek, DAN and CIP10 methods for measuring toluene diisocyanate (TDI) at a polyurethane foam factory.

Because of the semi-volatile nature of diisocyanates (being airborne in both physical vapor and particulate phases), their high reactivity and low occupational exposure limits, diisocyanate exposure evaluation has been challenging for industrial hygienists and laboratories. The objective of this study was to compare the toluene diisocyanate (2,4 and 2,6 isomers, TDI) concentration measured by five methods in a flexible polyurethane foam factory using different collection or derivatization approaches. The methods used were: OSHA 42 modified (filter, 1-(2-pyridyl)piperazine) (OSHA), Asset EZ4-NCO (denuder and filter, dibutylamine) (Asset), Iso-Chek (double-filter, 9-(N-methylaminomethyl) anthracene and 1,2-methoxyphenylpiperazine), DAN (filter, 1,8-diaminonaphthalene), and CIP10 (centrifugation, 1,2-methoxyphenylpiperazine). Particle real-time monitoring for concentration and size distribution was performed in parallel to improve the understanding of the potential bias between methods. The comparison study was performed over 3 days, providing 18 replicates for each of the 5 methods. Isocyanate concentrations collected for each sampling method were compared using linear mixed effect modeling. Compared to OSHA, which yielded the highest concentrations overall, the Asset and DAN methods provided the smallest biases (-29% (95% CI [-52;-6]) and -45% (95% CI [-67;-23]), respectively), while the CIP10 and Iso-Chek methods provided the largest biases (-82% (95% CI [-105;-66]) and -96% (95% CI [-118;-75]), respectively). The substantial bias of Iso-Chek and CIP10 seemed to be explained by the predominance of TDI in the form of sub-micron particles that were inadequately captured by these two methods due to their sampling principle, which are particle filtration without derivatizing agent and centrifugation respectively. Asset and DAN performance seemed to decrease as the sampling time increased. While DAN's bias could be related to a reagent deficiency on the filter, the disparities between OSHA and Asset, both considered as reference methods, highlight the fact that the mechanisms of collection, derivation and extraction do not seem to be completely controlled. Finally, an upward trend has been observed between concentrations of particles below 300 nm in size and concentration levels of TDI. It has also been observed that TDI levels increased with the TDI foam index produced at the facility.

A validated liquid chromatography/tandem mass spectrometry method for 4,4'-methylenedianiline quantitation in human urine as a measure of 4,4'-methylene diphenyl diisocyanate exposure.

RATIONALE: 4,4'-Methylene diphenyl diisocyanate (MDI) is a highly reactive isocyanate used in the production of polyurethanes. Workers exposed to these products may develop sensitization to the diisocyanate compounds, leading to occupational asthma. Quantifying MDI levels is necessary to ensure workplace safety. MDI is metabolized by acetylation and/or conjugation to macromolecules for excretion into urine. All metabolites can be chemically hydrolyzed to form the free diamine 4,4'-methylenedianiline (MDA) as a urinary biomarker of MDI exposure. Current methods involve long sample preparation, or have been designed using costly automation. There is therefore a need to develop a new practical method for assessing exposure to MDI. METHODS: Urine samples were acidified and heated to form MDA, followed by neutralization and liquid-liquid extraction. Extracts were separated by reversed-phase chromatography on a HSS T3 column followed by analysis on a triple quadrupole mass spectrometer in multiple reaction monitoring (MRM) mode. RESULTS: 13 C15 N-MDA was selected as the internal standard (IS) of choice following an investigation of internal standard stability. The hydrolysis efficiency, forming free MDA from conjugated metabolites in vivo, was evaluated using 4,4'-methylenebis(acetanilide) spiked into urine and complete hydrolysis occurred after 1 h. A dynamic range of 5 to 500 nM was achieved, and was useful for monitoring MDI exposure considering the biological guidance value (BGV) of 10 µg/L (~50 nM) proposed by the German Research Foundation (DFG). The limit of detection (LOD) and limit of quantification (LOQ) of the method were 0.8 and 2.7 nM, respectively. The intra-day and inter-day precisions were 4.33% and 4.27%, respectively. Finally, the method was tested with inter-laboratory samples from the German External Quality Assessment Scheme (G-EQUAS) program and the results submitted were all within the allowable tolerance range. CONCLUSIONS: A practical and validated method for the analysis of small- to medium-sized batches of samples has been developed for the biological monitoring of MDI exposure in human urine.

Standardized Procedure for the Simultaneous Determination of the Matrix Effect, Recovery, Process Efficiency, and Internal Standard Association.

The matrix effects (MEs) on the quantification of an analyte can be significant and should not be neglected during development and validation of an analytical method. According to this premise, we developed a standardized procedure based on a set of six tests performed on six different sample matrices to detect and characterize the effects of the matrix for single and multiple analytes methods. The link between the matrix effect, recovery, process efficiency, accuracy, precision, and calibration curve was underscored by calculations performed with peak areas, ratios of standard/internal standard peak area, and concentrations. The terms instrumental ME and global ME were introduced, and the term recovery was subdivided for clarity. The test accounts for the presence of ubiquitous and endogenous analytes through background subtraction. The results showed the necessity for using samples with an original concentration in the same range and that the concentration selected for the addition had a definite impact on the results. The use of six-sample matrices provided a standard deviation on the results, and this information could be inserted in a method performance result to show precision. The tool also allows for testing of different analytes/internal standard combinations, which helps with the selection of the association with minimum MEs. A UPLC-MS/MS method for the quantification of several phthalate metabolites in urine was developed and validated with this test. This methodology responds to a scientific need for homogeneity, clarity, and understanding of the results and facilitates the decision-making process while lowering the required costs and time.

Pilot study of biological monitoring of four antineoplastic drugs among Canadian healthcare workers.

Purpose There are health risks to workers occupationally exposed to antineoplastic drugs. We hypothesized that implementing a biological monitoring program would be feasible. The goal was to present the results of our pilot cross-sectional study of biological monitoring of four antineoplastic drugs. Methods We recruited workers from the hematology-oncology department and control workers in a mother-child university health center. This study was preceded by an information period during which we aimed at enhancing the workers' awareness and knowledge of the risks of occupational exposure. Participants filled out a journal containing activities performed and personal protective equipment worn. One urine sample was collected at the end of their shift. Samples were analyzed by UPLC/MS-MS for the presence of cyclophosphamide, ifosfamide, methotrexate, and alpha-fluoro-beta-alanine (5-fluorouracile's main urinary metabolite). Results The participation rate was 85.7% (102/119). No urine sample had detectable concentrations of any of the four drugs evaluated (0/101; 0/74 nurses, 0/11 pharmacists, 0/9 pharmacy technicians, and 0/7 doctors). In the 5 days before sampling, 67/92 (72.8%) hematology-oncology participants performed at least one activity with antineoplastic drugs. Nurses wore all of the recommended protection for technical activities (86.2%), but rarely for non-technical activities (14.9%). Pharmacists and pharmacy technicians wore all of the recommended protection for all activities (100.0%). Conclusions This pilot study had a good participation rate. The absence of positive samples was a good indication that the measures in place ensured workers' safety, even though we found areas where the worker protection can be enhanced.

Identification of methylene diphenyl diisocyanate thermal degradation products in a generation chamber by liquid chromatography coupled with tandem mass spectrometry.

Isocyanate thermal degradation characterization by liquid chromatography coupled with electrospray tandem mass spectrometry has been performed to elucidate the methylene diphenyl diisocyanate (MDI) thermal degradation structure emitted in a generation chamber using a temperature between 50°C and 180°C to produce MDI vapors. [M+H](+) ions containing an isocyanate functional group were studied by tandem mass spectrometry. The [M+H](+) ion analyses based on the combination of full scans and precursor ion scans were useful for identifying all structures. The compounds emitted were identified and validated as a mixture of compounds containing amine and isocyanate functions. Residual MDI, methylene diphenyl amino-isocyanate, and methylene diphenyl diamine were identified. Polymerized forms of these structures were also observed because amine and isocyanate chemical functions react rapidly to polymerize. These results must be used with special care by scientists establishing sensitization diagnostics and developing sampling devices using generation chambers as they must be related to MDI behavior in workplaces. Even if pure MDI is introduced in the generation chamber, several different compounds are generated when the MDI is heated at a high temperature. This can result in some misleading interpretations for non-specific isocyanate sampling device development and sensitization diagnostics as MDI is present in the chamber with other compounds with known adverse effects.

Implementation and evaluation of an analytical method for a novel derivatizing agent to measure 4,4'-methylene diphenyl diisocyanate atmospheres.

Accurate measurement of 4,4'-methylene diphenyl diisocyanate (MDI) atmospheres is a challenge since the molecule is both chemically reactive and likely to be present in aerosol form when heated and sprayed because of its low vapor pressure. Meeting this challenge requires optimizing both the sampling device used and the derivatization agent employed to stabilize the isocyanate functional group. This study describes the use of a novel derivatization reagent for isocyanate sampling to address the challenge of MDI aerosol exposure sampling. Like most conventional derivatizing agents for isocyanates, 1,8-diaminonapthalene (DAN) reacts with isocyanate functional groups to form a urea. However, unlike other isocyanate derivatizing agents, the sample workup procedure with DAN includes a second step which yields a single analyte molecule, perimidone, for each isocyanate group. This feature gives DAN the unique ability to assess exposure to "total reactive isocyanate group" (TRIG). The analytical method implemented to quantitate the perimidone uses liquid chromatography coupled with tandem mass spectrometry. Positive mode ionization led to LOD and LOQ of 10 ng/mL and 34 ng/mL, respectively. The dynamic range was from 50-2000 ng/mL (with R(2) ≥ 0.990), which corresponds to TRIG concentrations in air from 0.07-3.04 µg/m(3), assuming 60 min of sampling at 10 L/min (based on use of the CIP-10M sampler). The intra-day and inter-day analytical precisions were <4% for all of the concentration levels tested, and the accuracy was within an appropriate range of 98 ± 2%. Minimal matrix effect was observed, and a total recovery of 109% was obtained. The approach seems to be promising for TRIG measurements and further work is planned to establish DAN method behavior in samplers used for workplace monitoring.

Determination of triglycidyl isocyanurate from air samples by ultra-performance liquid chromatography coupled with coordination ion spray mass spectrometry.

RATIONALE: Ultra-performance liquid chromatography (UPLC) coupled with coordination ion spray tandem mass spectrometry was used for the analysis of air samples containing triglycidyl isocyanurate. The method is not affected by any chromatographic interference and the filter extract is compatible with the UPLC system, as opposed to approaches using high-performance liquid chromatography coupled with ultraviolet detection and gas chromatography coupled with mass spectrometry. METHODS: Accu-cap™ filters that had sampled triglycidyl isocyanurate were extracted using a mixture of acetonitrile/acetone (95/5) diluted with 3 volumes of water and were then analyzed. The mass spectrometry method uses sodium as the alkali adduct complexing with the triglycidyl isocyanurate in positive mode, and this complex is then analyzed using the survivor mode where the same ion is monitored in the first and third quadrupoles of a triple quadrupole mass spectrometer. RESULTS: The method has a limit of detection and limit of quantitation of 50 and 170 ng/filter, respectively. The dynamic range was between 480 and 24,000 ng/sample, which is equivalent to 2 µg/m(3) and 100 µg/m(3) based on a sampling volume of 240 L. The intra- and inter-day precisions were both <4% and the overall accuracy was 97 ± 3%. The method was tested with personal breathing zone random samples collected from workers using triglycidyl isocyanurate in their tasks, and all the random samples were easily quantified. CONCLUSIONS: A new method by UPLC coupled with coordination ion spray tandem mass spectrometry using sodium as the alkali adduct is now available for industrial hygienists who want to evaluate exposures of workers to triglycidyl isocyanurate in workplaces.

CIP10 optimization for 4,4-methylene diphenyl diisocyanate aerosol sampling and field comparison with impinger method.

4,4-methylene diphenyl diisocyanate (MDI) aerosol exposure evaluation in spray foam insulation application is known as being a challenge because the spray foam application actually involves a fast-curing process. Available techniques are either not user-friendly or are inaccurate or not validated for this application. To address these issues, a new approach using a CIP10M was developed to appropriately collect MDI aerosol in spray foam insulation while being suitable for personal sampling. The CIP10M is a commercially available personal aerosol sampler that has been validated for the collection of microbial spores into a liquid medium. Tributylphosphate with 1-(2-methoxyphenyl)piperazine (MOPIP) was introduced into the CIP10M to collect and stabilize the MDI aerosols. The limit of detection and limit of quantification of the method were 0.007 and 0.024 µg ml(-1), respectively. The dynamic range was from 0.024 to 0.787 µg ml(-1) (with R (2) ≥ 0.990), which corresponds to concentrations in the air from 0.04 to 1.3 µg m(-3), assuming 60 min of sampling at 10 l min(-1). The intraday and interday analytical precisions were <2% for all of the concentration levels tested, and the accuracy was within an appropriate range of 98 ± 1%. No matrix effect was observed, and a total recovery of 99% was obtained. Parallel sampling was performed in a real MDI foam spraying environment with a CIP10M and impingers containing toluene/MOPIP (reference method). The results obtained show that the CIP10M provides levels of MDI monomer in the same range as the impingers, and higher levels of MDI oligomers. The negative bias observed for MDI monomer was between 2 and 26%, whereas the positive bias observed for MDI oligomers was between 76 and 113%, with both biases calculated with a confidence level of 95%. The CIP10M seems to be a promising approach for MDI aerosol exposure evaluation in spray foam applications.

Comparison between the ASSET EZ4 NCO and Impinger Sampling Devices for Aerosol Sampling of 4,4'-Methylene Diphenyl Diisocyanate in Spray Foam Application.

4,4'-methylene diphenyl diisocyanate (MDI) aerosol exposure evaluation in spray foam insulation application is known to be a challenge. Current available techniques are either not user-friendly or are inaccurate or are not validated for this application. A new sampler has recently been developed to address the user-friendliness issues with other samplers: the ASSET EZ4-NCO, but the use of this sampler in spray foam insulation applications has not been demonstrated or validated. Because of this, the current work was undertaken to provide a comparison of the ASSET sampler with an impinger method, considered to be the best available method in the context of spray foam insulation, and hence the pertinence of comparing this sampler to an impinger method, considered to be the best available method for measuring MDI monomer and oligomers for this particular application. Liquid chromatography coupled with tandem mass spectrometry method for MDI monomer and oligomer analysis was implemented based on the Supelco literature. It allows the analysis of MDI-dibutylamine (DBA) and MDI 3-ring-DBA with a minimum reported value of 5ng ml(-1), a dynamic range of 5-140ng ml(-1), precision <15% and accuracy >80%. This method was used to quantify MDI aerosols collected with the ASSET sampler in an MDI spray foam environment in parallel with the toluene/MOPIP impinger reference method. The ASSET sampler significantly underestimated the levels of MDI monomer and oligomers when compared to the reference method. The estimated bias was 72% (95% confidence interval [CI] 54-89%) for the monomer and 96% (95% CI 76-115%) for the oligomers. These results demonstrate the importance of evaluating each new sampler for each isocyanate application prior to a formal worker exposure evaluation.

Discovery of MK-1439, an orally bioavailable non-nucleoside reverse transcriptase inhibitor potent against a wide range of resistant mutant HIV viruses.

The optimization of a novel series of non-nucleoside reverse transcriptase inhibitors (NNRTI) led to the identification of pyridone 36. In cell cultures, this new NNRTI shows a superior potency profile against a range of wild type and clinically relevant, resistant mutant HIV viruses. The overall favorable preclinical pharmacokinetic profile of 36 led to the prediction of a once daily low dose regimen in human. NNRTI 36, now known as MK-1439, is currently in clinical development for the treatment of HIV infection.

Comprehensive proteomics approach in characterizing and quantifying allergenic proteins from northern shrimp: toward better occupational asthma prevention.

Occupational asthma is a major chronic health dilemma among workers involved in the seafood industry. Several proteins notoriously known to cause asthma have been reported in different seafood. This work involves the application of an allergenomics strategy to study the most potent allergens of northern shrimp. The proteins were extracted from shrimp tissue and profiled by gel electrophoresis. Allergenic proteins were identified based on their reactivity to patient sera and were structurally identified using tandem mass spectrometry. Northern shrimp tropomyosin, arginine kinase, and sarcoplasmic calcium-binding protein were found to be the most significant allergens. Multiple proteolytic enzymes enabled 100% coverage of the sequence of shrimp tropomyosin by tandem mass specrometry. Only partial sequence coverage was obtained, however, for the shrimp allergen arginine kinase. Signature peptides, for both tropomyosin and arginine kinase, were assigned and synthesized for use in developing the multiple reaction monitoring tandem mass spectrometric method. Subsequently, air samples were collected from a shrimp processing plant and two aerosolized proteins quantified using tandem mass specrometry. Allergens were detected in all areas of the plant, reaching levels as high as 375 and 480 ng/m(3) for tropomyosine and arginine kinase, respectively. Tropomyosine is much more abundant than arginine kinase in shrimp tissues, so the high levels of arginine kinase suggest it is more easily aerosolized. The present study shows that mass spectrometric analysis is a sensitive and accurate tool in identifying and quantifying aerosolized allergens.

Determination of trans,trans-muconic acid in workers' urine through ultra-performance liquid chromatography coupled to tandem mass spectrometry.

A novel method for the biological monitoring of benzene-exposed workers has been developed through ultra-performance liquid chromatography coupled to tandem mass spectrometry. The method uses trans,trans-muconic acid in urine as the benzene-exposure biomarker. The method was developed using a triple quadrupole mass spectrometer with enough sensitivity to facilitate diluting and injecting the urine samples directly, rather than performing a solid-phase extraction procedure as is common in the available protocols. Moreover, compared with a conventional high-pressure liquid chromatography system, the separation power provided by the ultra-performance liquid chromatography system allows a 10-fold reduction in run time. The method was adjusted to a dynamic range of between 198.9 and 4916.7 µg/L to cover the biological exposure index of trans,trans-muconic acid in urine. Also, the method demonstrated intra-day and inter-day precision at 98%, and accuracy within an acceptable range of 101 ± 8%. The method has been used to quantify various types of urine samples, such as workers' urine and inter-laboratory proficiency tests. Depending on the sample, the quantified levels ranged from less than the limit of quantitation to 3836.7 µg/L. No levels exceeding the calibration range were detected in the urine of workers, and the reported concentrations in urine for the proficiency tests were, as expected, based on known values. Moreover, the new method using sample dilution and faster chromatographic run was more effective, facilitating fast communication of results, as needed, to decision-makers.