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The microbiome has a fundamental impact on the human host's physiology through the production of highly reactive compounds that can lead to disease development. One class of such compounds are carbonyl-containing metabolites, which are involved in diverse biochemical processes. Mass spectrometry is the method of choice for analysis of metabolites but carbonyls are analytically challenging. Herein, we have developed a new chemical biology tool using chemoselective modification to overcome analytical limitations. Two isotopic probes allow for the simultaneous and semi-quantitative analysis at the femtomole level as well as qualitative analysis at attomole quantities that allows for detection of more than 200 metabolites in human fecal, urine and plasma samples. This comprehensive mass spectrometric analysis enhances the scope of metabolomics-driven biomarker discovery. We anticipate that our chemical biology tool will be of general use in metabolomics analysis to obtain a better understanding of microbial interactions with the human host and disease development., (© 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Safe and noninvasive methods for breast cancer screening with improved accuracy are urgently needed. Volatile organic compounds (VOCs) in biological samples such as breath and blood have been investigated as noninvasive novel markers of cancer. We investigated volatile organic compounds in urine to assess their potential for the detection of breast cancer. One hundred and ten women with biopsy-proven breast cancer and 177 healthy volunteers were enrolled. The subjects were divided into two groups: a training set and an external validation set. Urine samples were collected and analyzed by gas chromatography and mass spectrometry. A predictive model was constructed by multivariate analysis, and the sensitivity and specificity of the model were confirmed using both a training set and an external set with reproducibility tests. The training set included 60 breast cancer patients (age 34-88 years, mean 60.3) and 60 healthy controls (age 34-81 years, mean 58.7). The external validation set included 50 breast cancer patients (age 35-85 years, mean 58.8) and 117 healthy controls (age 18-84 years, mean 51.2). One hundred and ninety-one compounds detected in at least 80% of the samples from the training set were used for further analysis. The predictive model that best-detected breast cancer at various clinical stages was constructed using a combination of two of the compounds, 2-propanol and 2-butanone. The sensitivity and specificity in the training set were 93.3% and 83.3%, respectively. Triplicated reproducibility tests were performed by randomly choosing ten samples from each group, and the results showed a matching rate of 100% for the breast cancer patient group and 90% for the healthy control group. Our prediction model using two VOCs is a useful complement to the current diagnostic tools. Further studies inclusive of benign tumors and non-breast malignancies are warranted., (© 2021. The Author(s).)

Using improved HPLC analysis conditions, we report the separation of three isomers of mercapturic acid conjugates previously assigned in the literature only to 3-hydroxy-1-methylpropylmercapturic acid (HMPMA-1), a human urinary metabolite of crotonaldehyde. The new conditions, employing a biphenyl column cooled to 5 °C and eluted with a gradient of formic acid, acetonitrile, and methanol, allow the analysis of human urinary mercapturic acids derived not only from crotonaldehyde but also from its isomers methacrolein (3-hydroxy-2-methylpropyl mercapturic acid, HMPMA-2) and methyl vinyl ketone (3-hydroxy-3-methylpropyl mercapturic acid, HMPMA-3). The mercapturic acids were detected and quantified by LC-ESI-MS/MS using the corresponding stable isotope labeled mercapturic acids as internal standards. The analysis was validated for accuracy and precision and applied to urine samples collected from cigarette smokers and nonsmokers. Smokers had significantly higher levels of all three mercapturic acids than did nonsmokers. The results demonstrated that HMPMA-3 from methyl vinyl ketone comprised the major portion of the peaks previously ascribed in multiple studies to HMPMA-1. HMPMA-1 had concentrations intermediate between those of HMPMA-2 and HMPMA-3 in both smokers and nonsmokers. This study reports the first quantitation of HMPMA-2 and HMPMA-3 in human urine. The observation of higher levels of HMPMA-3 than in the other two mercapturic acids suggests a previously unrecognized potential significance of methyl vinyl ketone as a toxicant in smokers and nonsmokers.

1. Multiple exposures are ubiquitous in industrial environments. In this article, we highlight the risks faced by workers and complete the data available on the metabolic impact of a common mixture: toluene (TOL) and methylethylketone (MEK). 2. Rats were exposed by inhalation under controlled conditions either to each solvent individually, or to mixtures of the two. How the interaction between the two solvents affected their fate in the blood and brain, their main relevant urinary metabolites (o-cresol, benzylmercapturic acid for TOL and 2,3-butanediols for MEK) and their hepatic metabolism were investigated. 3. Although the cytochrome P450 concentration was unchanged, and the activities of CYP1A2 and CYP2E1 isoforms were not additively or synergistically induced by co-exposure, TOL metabolism was inhibited by the presence of MEK (and vice versa). Depending on the relative proportions of each compound in the mixture, this sometimes resulted in a large increase in blood and brain concentrations. Apart from extreme cases (unbalanced mixtures), the amount of o-cresol and benzylmercapturic acid (and to a lesser extent 2,3-butanediols) excreted were proportional to the blood solvent concentrations. 4. In a co-exposure context, ortho-cresol and benzylmercapturic acid can be used as urinary biomarkers in biomonitoring for employees to relatively accurately assess TOL exposure.

Methylethylketone (MEK) is widely used in industry, often in combination with other compounds. Although nontoxic, it can make other chemicals harmful. This study investigates the fate of MEK in rat blood, brain and urine as well as its hepatic metabolism following inhalation over 1 month (at 20, 200 or 1400 ppm). MEK did not significantly accumulate in the organism: blood concentrations were similar after six-hour or 1-month inhalation periods, and brain concentrations only increased slightly after 1 month's exposure. Urinary excretion, based on the major metabolites, 2,3-butanediols (± and meso forms), accounted for less than 2.4% of the amount inhaled. 2-Butanol, 3-hydroxy-2-butanone and MEK itself were only detectable in urine in the highest concentration conditions investigated, when metabolic saturation occurred. Although MEK exposure did not alter the total cytochrome P450 concentration, it induced activation of both CYP1A2 and CYP2E1 enzymes. In addition, the liver glutathione concentration (reduced and oxidized forms) decreased, as did glutathione S-transferase (GST) activity (at exposure levels over 200 ppm). These metabolic data could be useful for pharmacokinetic model development and/or verification and suggest the ability of MEK to influence the metabolism (and potentiate the toxicity) of other substances.

A novel, rapid, simple and green vortex-assisted surfactant-enhanced emulsification microextraction method based on solidification of floating organic drop was developed for simultaneous separation/preconcentration and determination of ultra trace amounts of naproxen and nabumetone with high performance liquid chromatography-fluorescence detection. Some parameters influencing the extraction efficiency of analytes such as type and volume of extractant, type and concentration of surfactant, sample pH, KCl concentration, sample volume, and vortex time were investigated and optimized. Under optimal conditions, the calibration graph exhibited linearity in the range of 3.0-300.0ngL(-1) for naproxen and 7.0-300.0ngL(-1) for nabumetone with a good coefficient of determination (R(2)>0.999). The limits of detection were 0.9 and 2.1ngL(-1). The relative standard deviations for inter- and intra-day assays were in the range of 5.8-10.1% and 3.8-6.1%, respectively. The method was applied to the determination of naproxen and nabumetone in urine, water, wastewater and milk samples and the accuracy was evaluated through recovery experiments., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Toxicokinetic modeling is a useful tool to describe or predict the behavior of a chemical agent in the human or animal organism. A general model based on four compartments was developed in a previous study to quantify the effect of human variability on a wide range of biological exposure indicators. The aim of this study was to adapt this existing general toxicokinetic model to three organic solvents--methyl ethyl ketone, 1-methoxy-2-propanol, and 1,1,1,-trichloroethane--and to take into account sex differences. In a previous human volunteer study we assessed the impact of sex on different biomarkers of exposure corresponding to the three organic solvents mentioned above. Results from that study suggested that not only physiological differences between men and women but also differences due to sex hormones levels could influence the toxicokinetics of the solvents. In fact the use of hormonal contraceptive had an effect on the urinary levels of several biomarkers, suggesting that exogenous sex hormones could influence CYP2E1 enzyme activity. These experimental data were used to calibrate the toxicokinetic models developed in this study. Our results showed that it was possible to use an existing general toxicokinetic model for other compounds. In fact, most of the simulation results showed good agreement with the experimental data obtained for the studied solvents, with a percentage of model predictions that lies within the 95% confidence interval varying from 44.4 to 90%. Results pointed out that for same exposure conditions, men and women can show important differences in urinary levels of biological indicators of exposure. Moreover, when running the models by simulating industrial working conditions, these differences could be even more pronounced. A general and simple toxicokinetic model, adapted for three well-known organic solvents, allowed us to show that metabolic parameters can have an important impact on the urinary levels of the corresponding biomarkers. These observations give evidence of an interindividual variability, an aspect that should have its place in the approaches for setting limits of occupational exposure.

High-performance liquid chromatography (HPLC) coupled with electrospray ionization mass spectrometry (ESI-MS) was applied for the analysis of nabumetone metabolites during the biotransformation in minipigs. In addition to known phase I metabolites, the identification of phase II metabolites was achieved on the basis of their full-scan mass spectra and subsequent MS(n) analysis using both positive-ion and negative-ion ESI mode. Some phase I metabolites are conjugated with both glucuronide acid and glycine, which is quite unusual type of phase II metabolite not presented so far for nabumetone. These metabolites were found in small intestine content, but they were absent in minipigs urine., (Copyright © 2013 Elsevier B.V. All rights reserved.)

A simple fluorescent methodology for the simultaneous determination of nabumetone and its main metabolite, 6-methoxy-2-naphthylacetic acid (6-MNA), in pharmaceutical preparations and human urine is proposed. Due to the strong overlapping between the fluorescence spectra of both analytes, the use of fluorescence decay curves to resolve their mixture is proposed, since these curves are more selective. Values of dependent instrumental variables affecting the signal-to-noise ratio were fixed using a simplex optimization procedure. A factorial design with three levels per factor coupled to a central composite design was selected to obtain a calibration matrix of thirteen standards plus one blank sample that was processed using a partial least-squares (PLS) analysis. In order to assess the goodness of the proposed method, a prediction set of ten synthetic samples was analyzed, obtaining recovery percentages between 97 and 105%. Limits of detection, calculated by means of a new criterion, were 0.96 μg L(-1) and 0.88 μg L(-1) for nabumetone and 6-MNA, respectively. The method was also tested in the pharmaceutical preparation Relif, which contains nabumetone, obtaining recovery percentages close to 100%. Finally, the simultaneous determination of both analytes in human urine samples was successfully carried out by the PLS-analysis of a matrix of fifteen standards plus four analyte blanks and the use of the standard addition technique. Although urine shows native fluorescence, no extraction method or prior separation of the analytes was needed.

The aim of the study was to quantify the variability on biological indicators of exposure between men and women for three well known solvents: methyl ethyl ketone, 1-methoxy-2-propanol and 1,1,1-trichloroethane. Another purpose was to explore the effect of selected CYP2E1 polymorphisms on the toxicokinetic profile. Controlled human exposures were carried out in a 12 m³ exposure chamber for each solvent separately, during 6h and at half of the threshold limit value. The human volunteers groups were composed of ten young men and fifteen young women, including ten women using hormonal contraceptive. An analysis of variance mainly showed an effect on the urinary levels of several biomarkers of exposure among women due to the use of hormonal contraceptive, with an increase of more than 50% in metabolites concentrations and a decrease of up to 50% in unchanged substances concentrations, suggesting an increase in their metabolism rate. The results also showed a difference due to the genotype CYP2E1*6, when exposed to methyl ethyl ketone, with a tendency to increase CYP2E1 activity when volunteers were carriers of the mutant allele. Our study suggests that not only physiological differences between men and women but also differences due to sex hormones levels can have an impact on urinary concentrations of several biomarkers of exposure. The observed variability due to sex among biological exposure indices can lead to misinterpretation of biomonitoring results. This aspect should have its place in the approaches for setting limits of occupational exposure., (Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.)

Urine is commonly analysed in clinical practice by a variety of liquid-phase techniques to check for excessive ketone bodies, proteins and salts to name just a few compounds. However, little work has been carried out to measure the volatile compounds emitted by urine since these do not yet have an established role in clinical diagnosis. There is, however, a growing body of evidence that these volatile compounds can be indicators of adverse physiological conditions and disease and with the advent of sensitive gas-phase analytical methods they can be quickly quantified in urine headspace and potentially provide valuable support for clinical diagnosis. Thus, we are developing selected ion flow tube mass spectrometry, SIFT-MS, for the real-time analysis of urine headspace, ultimately to support rapid diagnosis in the clinical environment. In this paper we focus on volatile ketones in the headspace of aqueous solutions and urine donated by three healthy volunteers. Using SIFT-MS, we have unambiguously quantified in urine headspace acetone, by far the most abundant ketone, butanone, pentanone, hexanone and heptanone using NO(+) precursor ions. Further to this, we have determined the Henry's Law coefficients, HLC, for these ketones in aqueous solution to allow the liquid-phase concentrations in urine to be estimated from headspace levels of their vapours. In addition, the influence of the addition of physiological amounts of dissolved urea, sodium chloride and hydrochloric acid on the partitioning of these ketones between the aqueous phase and gas phase has been investigated and found to be small, which gives greater credence to the use of the HLC obtained using aqueous solutions for the estimation of ketone concentrations in urine. Finally, parallel measurements of the levels of acetone in exhaled breath and urine headspace have been obtained and shown to be very similar, which gives support to the previous deduction from breath analysis that acetone is a truly systemic compound.

Chromatographic analyses play an important role in the identification and determination of phase I and phase II drug metabolites. While the chemical standards of phase I metabolites are usually available from commercial sources or by various synthetic, degradation or isolation methods, the phase II drug metabolites have usually more complicated structures, their standards are in general inaccessible and their identification and determination require a comprehensive analytical approach involving the use of xenobiochemical methods and the employment of hyphenated analytical techniques. In this work, various high-performance liquid chromatography (HPLC) methods were employed in the evaluation of xenobiochemical experiments leading to the identification and determination of phase II nabumetone metabolites. Optimal conditions for the quantitative enzymatic deconjugation of phase II metabolites were found for the samples of minipig bile, small intestine contents and urine. Comparative HPLC analyses of the samples of above-mentioned biomatrices and of the same biomatrices after their enzymatic treatment using beta-glucuronidase and arylsulfatase afforded the qualitative and quantitative information about phase II nabumetone metabolites. Hereby, three principal phase II nabumetone metabolites (ether glucuronides) were discovered in minipig's body fluids and their structures were confirmed using liquid chromatography (LC)-electrospray ionization mass spectrometric (MS) analyses.

Objective: To examine whether unmetabolized methyl isobutyl ketone in urine is a useful marker of low-level occupational exposure to this ketone solvent, as is the case for methyl ethyl ketone., Methods: The study was conducted in the second half of a working week. In total, 27 furniture-making workers (19 men and eight women) and 11 non-exposed controls (six men and five women) volunteered to participate in the study. Time-weighted average (TWA; 8-h) concentration of vapors of several solvents in air, including methyl isobutyl ketone (MIBK-A) and methyl ethyl ketone (MEK-A) was monitored by diffusive sampling. Urine samples collected at the end of the shift were subjected to head-space gas chromatography (GC) analysis for the unmetabolized solvents (i.e., MIBK-U and MEK-U). The relationship between the concentration of the solvent vapor and the corresponding solvent level in urine was examined by simple as well as multiple regression analysis., Results: The exposures to MIBK and MEK were well below the current occupational exposure limit levels, but the maximum levels of exposure to toluene and ethylbenzene were around the corresponding exposure limit. The correlation of the TWA concentration of the solvent in air with the concentration of the corresponding solvent in the end-of-shift urine sample was significant both for MIBK and for MEK, and the correlation coefficient was larger for MIBK than for MEK. The slope in the exposure-excretion regression line was almost twice as steep for MEK than for MIBK, possibly due to the difference in water solubility. Approximately 0.12% of MIBK absorbed in the lungs will be excreted into urine, whereas the yield for MEK was somewhat higher (0.19%)., Conclusion: MIBK in urine is a good marker of exposure to MIBK, as in the case of MEK in urine for MEK exposure.

A high-performance liquid chromatographic (HPLC) method for simultaneous determination of naproxen (NAP), nabumetone (NAB) and its major metabolite, 6-methoxy-2-naphthylacetic acid (6-MNA), was developed for the application to pharmaceuticals and human urine. Isocratic reversed-phase HPLC was employed for quantitative analysis using triethylamine and 1-heptanesulfonic acid sodium salt (HSA) as ion-pair reagents. Urine samples were purified by solid-phase extraction using Bond-Elut Certify II cartridges containing reversed-phase and anion exchange functionalities. The HPLC assay was carried out using a Wakosil ODS 5C18 column (5 microm, 150 x 4.6 mm, i.d.). The mobile phase consisted of 0.5 g of HSA dissolved in 1,000 ml of a mixture of acetonitrile, water and triethylamine (500:500:1, v/v) adjusted with phosphoric acid to pH 3. The calibration curves of NAP and NAB showed good linearity in the concentration range 32-160 microg/ml with UV detection (270 nm) for pharmaceuticals. In the low concentration ranges (8-96 ng of NAP per ml, 24-288 ng of NAB per ml and 5.6-67.2 ng of 6-MNA per ml), the calibration curves were also obtained with fluorimetric detection (excitation 280 nm, emission 350 nm) for biological fluids. The correlation coefficients were better than 0.999 in all cases. The lower limits of detection (defined as a signal-to-noise ratio of about 3) were approximately 0.3 ng for NAP, 1.5 ng for NAB and 0.2 ng for 6-MNA. The procedure described here is rapid, simple, selective, and is suitable for routine analysis of pharmaceuticals and pharmacokinetic studies in human urine samples.

Headspace solid-phase microextraction coupled with gas chromatography/flame ionization detection was developed to measure urinary methyl ethyl ketone (MEK). A fused silica fiber coated with 75 microns carboxen/polydimethylsiloxane was used to extract urinary MEK. The optimal extraction conditions were obtained when temperature was 50 degrees C, extraction time was 15 minutes, and ammonium sulfate concentration was 0.5 g/mL. The optimal desorption temperature and time were 200 degrees C and 5 minutes, respectively. The concentration range of calibration curves was 27 to 8000 ng/mL of MEK. The within-day and between-day pooled coefficients of variation (9 concentrations, triplicate samples) were 5.4% and 8.8%, respectively. The limit of detection and limit of quantitation were 4.2 ng/mL and 21.6 ng/mL, respectively. The recovery (+/- standard deviation) of MEK was 100.2% +/- 8.6% (n = 3). MEK in urine was stable for at least 1 month when stored at -20 degrees C. This method proved to be applicable for the analysis of urinary MEK of exposed workers in a plastic material printing plant. We concluded that this new method is sensitive, inexpensive, simple, and reliable for measuring the occupational exposure of MEK.

1. The disposition of 14C-methyl ethyl ketoxime (MEKO) was determined in the male F344 rat following oral, intravenous (i.v.) and dermal administration. 2. Oral doses of 2.7, 27 and 270 mg/kg were primarily excreted as CO2 (71-49%) in decreasing percentage as the dose increased. Excretion in urine (13-26%) and as volatiles (5-18%) increased as the dose increased. Five to 6% of the dose remained in the major tissues after 72 h. 3. An i.v. dose of 2.7 mg/kg was also principally excreted as CO2 (48.8%) with excretion in urine and as expired volatiles accounting for 21.4 and 11.4%, respectively. About 7% of the administered radioactivity remained in the tissues after 72 h. 4. Following dermal administration, 13 and 26% of a 2.7 and 270 mg/kg dose, respectively, were absorbed. Volatilization from the dose site prior to placement in the metabolism cage may account for the low absorption. 5. MEKO was biotransformed to at least five polar metabolites that could only be partially resolved by anion exchange chromatography. Incubation with glucuronidase, but not sulphatase, changed the urinary metabolic profile. Methyl ethyl ketone was a major component in the volatiles.

Exposure monitoring by personal diffusive samplers, biological monitoring of toluene exposure by urinary hippuric acid determination, haematology, serum biochemistry for liver function, and a subjective symptom survey by questionnaire were conducted on 303 male solvent workers. They were exposed to a mixture of solvents including toluene (geometric mean 18 ppm), methyl ethyl ketone (MEK; 16 ppm), isopropyl alcohol (IPA; 7 ppm), and ethyl acetate (9 ppm). The intensity was mostly below unity using the additiveness formula based on current Japanese occupational exposure limits, but more than eight times unity at the maximum. The results were compared with the findings in 135 non-exposed male workers of similar ages. Haematology and liver function tests did not show any exposure related abnormality, and subjective symptoms were mostly related to central nervous system depression and local irritation. Further analysis suggested that the irritation effects were not related to exposure to MEK. Analysis of the relation between toluene exposure and hippuric acid excretion in urine showed that there was no metabolic interaction between MEK and toluene, or between IPA and toluene. Overall, therefore, it is concluded that there was no sign or symptom detected to suggest anything other than toluene toxicity, that there was no evidence to indicate any modification of toluene toxicity or metabolism due to coexposure, and that the additiveness assumption is reasonable for risk assessment for the combination of solvents under these exposure conditions.

Nabumetone is a new, nonacidic, nonsteroidal antiinflammatory drug. At least 80% of nabumetone is absorbed, and food, milk, and aluminum antacids increase the rate, but not the extent, of absorption. It is rapidly metabolized in the liver to 6-methoxy-2-naphthylacetic acid (6MNA), the major circulating active metabolite. At steady state, the time to maximum plasma concentration for 6MNA is 1 to 4 h. 6MNA has a very low clearance rate and long half-life (about 24 h). In general, steady state plasma concentrations of 6MNA increase in proportion with increases in the dose of nabumetone administered. Steady state plasma concentrations of 6MNA in the elderly are slightly higher than in healthy volunteers; however, this does not appear to be clinically significant. Preliminary studies in patients with impaired renal function indicate that the pharmacokinetics are not altered in patients with mild to moderate disease.

We report a high-performance liquid chromatographic procedure for determining methyl ethyl ketone in urine. The method is based on pre-column derivatization with 2,4-dinitrophenylhydrazine and liquid-liquid extraction of the derivative. The analyte is chromatographically separated from other urine constituents in less than 12 min and is detected by UV absorption at 360 nm. Peak height and concentration are linearly related. The relative standard deviation assessed for within-day imprecision was 3.2% at the 2.21 mg/l level. The mean analytical recovery from urines spiked with 1.0 mg/l ketone was 96.0 +/- 6.1%. The simple sample handling, the small volume of urine required and the short amount of time taken for the whole procedure make it suitable for routine biomonitoring of exposure to methyl ethyl ketone in industrial workers. The concentration in urine from nine non-exposed controls was less than 0.1 mg/l. The concentrations measured in urine samples from 60 exposed workers ranged from 0.1 to 1.1 mg/l and from 0.3 to 3.6 mg/l at the before- and the end-shift collections, respectively.

Using HS.GC, We have succeeded in simultaneous determination of Ac, MeOH and MEK in urine without any complicated pretreatment or correction by internal standard. Moreover, in order to lower the detection limits of these materials, study was made on the salting out effect using 14 kinds of salts. As pretreatment, 2.0 ml of urine, 3.0 g of sodium sulfate and small sized magnetic stirrer are put into vial, which is sealed by septum. This is then heated for 10 min in warm bath of 50 degrees C. In order to dissolve the added salts as much as possible, the specimen is stirred by the stirrer. After cooling the liquid to room temperature, the specimen is analysed by HS.GC. The results showed that sodium sulfate was excellent synthetically. 1) Using the urine of workers not exposed to organic solvents three kinds of urine having specific gravity of 1.010, 1.024 and 1.034 were prepared and mixed standard organic solvents (Ac, MeOH and MEK) were added. Recovery percentages and coefficients of variation were calculated. The results showed that recovery percentages ranged from 92.0 to 101.7% and coefficients of variation from 0.2 to 4.6%. 2) The regression equations of standard curves were satisfactory with y = 9053x - 200(r = 0.999, n = 12) for Ac, y = 801x - 400 (r = 0.999, n = 12) for MeOH, and y = 15488x - 277 (r = 0.999, n = 12) for MEK. 3) The detection limits calculated by IUPAC formula were 0.0092 mg/l for Ac, 0.11 mg/l for MeOH and 0.0063 mg/l for MEK. These results indicated that this method is superior to other methods because the pretreatment is very simple, specificity is excellent, analysis by standard curves is possible, and this method is not affected by specific gravity of the urine.

This study was conducted to evaluate the usefulness of three commonly used methods of biological monitoring for worker exposed to methyl ethyl ketone (MEK) under field conditions using blood, breath and urine. Environmental MEK exposures were measured by personal sampling with carbon-felt dosimeters. The correlation coefficient (r) between the time-weighted average (TWA) MEK concentration in air and the MEK concentration in blood collected at the end of the work shift was 0.85. The correlation coefficient between the TWA MEK level in air and the concentration exhaled in the breath of workers at the end of the work shift was 0.71. The end-of-shift urinary MEK excretion correlated best with the environmental concentration (r = 0.89). Correlations became lower after urine samples had been corrected for urinary creatinine (r = 0.83) or specific gravity (r = 0.73). After 8 h exposure to 200 ppm MEK, the corresponding end-of-shift urinary excretion was 5.1 mumol/l or 4.11 mg/g creatinine. This value is higher than that previously found in some studies, the difference probably being due to the physical activities of the present workers and their extensive skin contact with the solvent. The kinetics of inhaled MEK was also studied in eight subjects. Breath and urine samples were collected during the 8-h work shift on 2 consecutive Mondays. The results showed that urinary MEK excretion rose steadily until the end of exposure, whereas the MEK concentration in exhaled air varied markedly throughout the day.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of presystemic elimination of nabumetone disposition was evaluated in 6 cirrhotic patients after oral administration of a single dose of 1000 mg of the drug. The data revealed the major role of hepatic metabolism in the removal of the drug from the body. The relatively high values of hepatic plasma excretion ratio (= 0.60 +/- 0.04) and of the total intrinsic clearance (= 90.74 +/- 15.87 l/h) places nabumetone between drugs with intermediate properties; clearance being partly dependent on plasma (blood) flow rate and on the hepatic metabolism whose systemic availability was 32% of the dose. Very good coincidence was obtained when ranging patients according to morphological evaluation of liver impairments was compared to the values of nabumetone disposition parameters. There was a statistically significant positive correlation (r = 0.831, p less than 0.05) between the fraction of the dose reaching the systemic circulation, f, and the gamma-GT "normalization index" (i.e., ratio between the observed decrease of serum gamma-glutamyl transpeptidase activity and the pretreatment difference from the upper normal value). A definite interpretation of the data cannot be provided until more knowledge about the effect of 6-mO-2-naphthylacetic acid on nabumetone metabolism is available.

2,3-Butanediol was detected by capillary gas chromatography in 45 urine samples from 20 babies on a special care unit, 17 of whom were premature. The meso form of the diol predominated and in 21 samples was the only diastereoisomer present. Acetoin was found in 20 of the samples. It was never detected in the absence of 2,3-butanediol. 2,3-Butanediol was not detectable in more than trace amounts in urine from 66 other babies on the unit. The most likely origin of these compounds was from bacterial fermentation of pyruvate in the gut. Their presence may be explained by abnormal gut colonisation with acetoin-producing microorganisms, an abundant supply of nutrient lactose in the colon and increased intestinal permeability. It is further evidence of the magnitude of intestinal carbohydrate fermentation in preterm babies. 2,3-Butanediol could prove a useful biochemical marker for abnormal colonisation of neonates on special care units.

A method is described for the determination of the concentration of methyl ethyl ketone and its metabolites: 2-butanol, 3-hydroxy-2-butanone and the meso- and d,l-isomers of 2,3-butanediol in urine. The analytes were isolated from urine by solid-phase extraction and analysed by capillary gas chromatography. The recovery rates were 50-70% for the 2,3-butanediol isomers and 88-96% for the other analytes. The precision of the method ranged from 5 to 12% (S.D.%). The detection limit was 1.0 and 1.4 mg/l for meso- and d,l-2,3-butanediol, respectively, and ranged from 0.1 to 0.15 mg/l for the other analytes.

Head space gas chromatography (GC) was applied to measure methyl ethyl ketone (MEK) in urine from 62 MEK-exposed male workers, whose individual intensity of exposure to MEK was monitored utilizing the carbon felt dosimeter. The urinary MEK level increased rapidly to reach a plateau in the first quarter of the daily 8-h work, while very little MEK was detected in the preshift urine. When the MEK levels in the urine at the end of the shift were compared with the afternoon MEK-TWA values, the uncorrected MEK in urine correlated best with MEK in air (r = 0.774, n = 62), while correction for creatinine gave a comparable result and the correlation was poorer when corrected for a specific gravity of urine or for the lapse of time after preceding passage of urine. Balance of MEK absorption via inhalation and MEK excretion into urine revealed that only 0.1% of MEK absorbed will be excreted unchanged into urine. Wider application of head space GC is discussed for the analysis of unmetabolized solvents in urine.

Fifteen human volunteers were exposed to methyl ethyl ketone (MEK) vapor at 11.9-621.8 mg/m3 for a period of 2 to 4 hours at rest (ten cases) and during light physical exercise (five cases). Subsequently 78 workers occupationally exposed to MEK in a manufacture of leather suitcases (median value: 75.5 mg/m3; geometrical standard deviation: 3.12 mg/m3; range: 6-790) were studied. The analyses were performed by means of a Gas Chromatograph (GC) Hewlett-Packard 5880 A connected with a Mass Selective Detector (MSD). The relative uptake (R) of MEK was about 0.54 (standard deviation: 0.05) and it keeps practically constant either at rest or during light effort (V < 30 L/min). A linear relationship existed in the experimentally exposed subjects between urinary concentration (Cu) and amount of MEK absorbed (U) (Cu = 3.05 x U-162.1; r = 0.95; n = 15) (Cu = micrograms/L; U = mg). Both in the experimentally exposed subjects and in the occupationally exposed workers, the urinary concentration of MEK shoved a linear relationship to the corresponding environmental time-weighted average concentration (CI). The correlation coefficients (r) were 0.93 in occupationally exposed subjects (regression equation: Cu = 0.004 x CI + 0.118; n = 78); Cu = mg/L; CI = mg/m3) and more than 0.93 in experimentally exposed groups. The findings indicate that the urinary concentration of MEK can be used as an appropriate biological exposure indicator.(ABSTRACT TRUNCATED AT 250 WORDS)

1. The metabolism of 4-(4-hydroxyphenyl)butan-2-one(raspberry ketone) was studied in rats, guinea-pigs and rabbits. 2. Following intragastric dosage (1 mmol/kg) urinary metabolite excretion was nearly complete within 24 h, amounting to roughly 90% of the dose in all species. 3. The most prominent urinary metabolites were raspberry ketone and its corresponding carbinol, both largely conjugated with glucuronic acid and/or sulphate. The extent of ketone reduction was greatest in rabbits. 4. Oxidative metabolism included ring hydroxylation and side-chain oxidation. The latter pathway led to 1,2- and 2,3-diol derivatives. It is proposed that the latter undergo cleavage to furnish the C6-C3 and C6-C2 derivatives detected.

1. Rabbits dosed orally with beta-ionone excreted in the urine unchanged beta-ionone, 3-oxo-beta-ionone, 3-oxo-beta-ionol, dihydro-3-oxo-beta-ionol and 3-hydroxy-beta-ionol. 2. Excretion products were isolated as 2,4-dinitrophenylhydrazone derivatives (beta-ionone, 3-oxo-beta-ionone, 3-oxo-beta-ionol and dihydro-3-oxo-beta-ionol) and as p-nitrobenzoate derivatives (3-oxo-beta-ionol, dihydro-3-oxo-beta-ionol and 3-hydroxy-beta-ionol), which were characterized and identified by comparison with the synthetic authentic compounds. 3. The glucuronides of 3-oxo-beta-ionol and dihydro-3-oxo-beta-ionol were also detected in the urine. The latter compound was isolated as free glucuronide, sodium salt and 2,4-dinitrophenylhydrazone.