Characterizing Key Volatile Pollutants Emitted from Adhesives by Chemical Compositions, Odor Contributions and Health Risks.

As one of the major sources of volatile pollutants in indoor air, gaseous emissions from adhesives during interior decoration have attracted increasing concern. Identifying major volatile pollutants and the risk in adhesive gaseous emissions is of great significance, but remains rarely reported. In the present research, we assessed the major volatile pollutants emitted from white emulsion adhesive and silicone adhesive samples (n = 30) from three aspects: chemical composition, odor and health risk contributions. The results showed that a total of 21 volatile pollutants were detected. Significantly, xylene was the most concentrated compound from white emulsion adhesives, accounting for 45.51% of the total concentrations. Butanone oxime was the most concentrated compound in silicone adhesives, accounting for 69.86% of the total concentrations. The trends in odor concentration (evaluated by the odor activity value method) over time were well correlated with the total chemical concentrations. Xylene (58.00%) and butanone oxime (76.75%) showed the highest odor contribution, respectively. Moreover, from an integrated perspective of chemical emissions, odor and health risk contributions, xylene, ethylbenzene, ethyl acetate and benzene were identified as the key volatile pollutants emitted from the white emulsion adhesives, while butanone oxime, butanone, and ethanol were the key volatile pollutants emitted from the silicone adhesives. This study not only identified the key volatile pollutants but also provided characteristics of odor and health risks of gas emitted from adhesives.

Chemoselective and Highly Sensitive Quantification of Gut Microbiome and Human Metabolites.

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.

High-Performance Cataluminescence Sensor Based on Nanosized V2O5 for 2-Butanone Detection.

The development of high-performance sensors is of great significance for the control of the volatile organic compounds (VOCs) pollution and their potential hazard. In this paper, high crystalline V2O5 nanoparticles were successfully synthesized by a simple hydrothermal method. The structure and morphology of the prepared nanoparticles were characterized by TEM and XRD, and the cataluminescence (CTL) sensing performance was also investigated. Experiments found that the as-prepared V2O5 not only shows sensitive CTL response and good selectivity to 2-butanone, but also exhibits rapid response and recovery speed. The limit of detection was found to be 0.2 mg/m3 (0.07 ppm) at a signal to noise ratio of 3. In addition, the linear range exceeds two orders of magnitude, which points to the promising application of the sensor in monitoring of 2-butanone over a wide concentration range. The mechanism of the sensor exhibiting selectivity to different gas molecules were probed by quantum chemistry calculation. Results showed that the highest partial charge distribution, lowest HOMO-LUMO energy gap and largest dipole moment of 2-butanone among the tested gases result in it having the most sensitive response amongst other VOCs.

Machine Vision Methods, Natural Language Processing, and Machine Learning Algorithms for Automated Dispersion Plot Analysis and Chemical Identification from Complex Mixtures.

Gas-phase trace chemical detection techniques such as ion mobility spectrometry (IMS) and differential mobility spectrometry (DMS) can be used in many settings, such as evaluating the health condition of patients or detecting explosives at airports. These devices separate chemical compounds in a mixture and provide information to identify specific chemical species of interest. Further, these types of devices operate well in both controlled lab environments and in-field applications. Frequently, the commercial versions of these devices are highly tailored for niche applications (e.g., explosives detection) because of the difficulty involved in reconfiguring instrumentation hardware and data analysis software algorithms. In order for researchers to quickly adapt these tools for new purposes and broader panels of chemical targets, it is critical to develop new algorithms and methods for generating libraries of these sensor responses. Microelectromechanical system (MEMS) technology has been used to fabricate DMS devices that miniaturize the platforms for easier deployment; however, concurrent advances in advanced data analytics are lagging. DMS generates complex three-dimensional dispersion plots for both positive and negative ions in a mixture. Although simple spectra of single chemicals are straightforward to interpret (both visually and via algorithms), it is exceedingly challenging to interpret dispersion plots from complex mixtures with many chemical constituents. This study uses image processing and computer vision steps to automatically identify features from DMS dispersion plots. We used the bag-of-words approach adapted from natural language processing and information retrieval to cluster and organize these features. Finally, a support vector machine (SVM) learning algorithm was trained using these features in order to detect and classify specific compounds in these represented conceptualized data outputs. Using this approach, we successfully maintain a high level of correct chemical identification, even when a gas mixture increases in complexity with interfering chemicals present.

Isoprene photochemistry over the Amazon rainforest.

Isoprene photooxidation is a major driver of atmospheric chemistry over forested regions. Isoprene reacts with hydroxyl radicals (OH) and molecular oxygen to produce isoprene peroxy radicals (ISOPOO). These radicals can react with hydroperoxyl radicals (HO2) to dominantly produce hydroxyhydroperoxides (ISOPOOH). They can also react with nitric oxide (NO) to largely produce methyl vinyl ketone (MVK) and methacrolein (MACR). Unimolecular isomerization and bimolecular reactions with organic peroxy radicals are also possible. There is uncertainty about the relative importance of each of these pathways in the atmosphere and possible changes because of anthropogenic pollution. Herein, measurements of ISOPOOH and MVK + MACR concentrations are reported over the central region of the Amazon basin during the wet season. The research site, downwind of an urban region, intercepted both background and polluted air masses during the GoAmazon2014/5 Experiment. Under background conditions, the confidence interval for the ratio of the ISOPOOH concentration to that of MVK + MACR spanned 0.4-0.6. This result implies a ratio of the reaction rate of ISOPOO with HO2 to that with NO of approximately unity. A value of unity is significantly smaller than simulated at present by global chemical transport models for this important, nominally low-NO, forested region of Earth. Under polluted conditions, when the concentrations of reactive nitrogen compounds were high (>1 ppb), ISOPOOH concentrations dropped below the instrumental detection limit (<60 ppt). This abrupt shift in isoprene photooxidation, sparked by human activities, speaks to ongoing and possible future changes in the photochemistry active over the Amazon rainforest.

Sources of methacrolein and methyl vinyl ketone and their contributions to methylglyoxal and formaldehyde at a receptor site in Pearl River Delta.

Methacrolein (MACR) and methyl vinyl ketone (MVK) are two major intermediate products from the photochemical oxidation of isoprene, the most important biogenic volatile organic compound. In addition, MACR and MVK have primary emissions. Investigating the sources and evolution of MACR and MVK could provide helpful information for the oxidative capacity of the atmosphere. In this study, hourly measurements of isoprene, MACR, and MVK were conducted at a receptor site in the Pearl River Delta region (PRD), i.e., the Heshan site (HS), from 22 October to 20 November, 2014. The average mixing ratios of isoprene, MACR and MVK were 151 ±â€¯17, 91 ±â€¯6 and 79 ±â€¯6 pptv, respectively. The daily variations and the ratios of MVK/MACR during daytime and nighttime suggested that other sources besides isoprene photooxidation influenced the MACR and MVK abundances at the HS. Positive matrix factorization was utilized to resolve the sources of MACR and MVK. Five sources were identified and quantified, including biogenic emissions, biomass burning, secondary formation, diesel, and gasoline vehicular emissions. Among them, secondary formation made the greatest contribution to observed MACR and MVK with average contributions of ~45% and ~70%, respectively. Through the yields of secondary products from the oxidation of MACR and MVK by the OH radical and the concentrations of MACR and MVK, it was found that methylglyoxal and formaldehyde were the main oxidation products of MACR and MVK at the HS site. Overall, this study evaluated the roles of primary emissions on ambient levels of MACR and MVK and advanced the understanding of photochemical oxidation of MACR and MVK in the PRD.

Determination of 2-alkylcyclobutanones by combining precolumn derivatization with 1-naphthalenyl hydrazine and ultra-performance liquid chromatography with fluorescence detection.

2-Alkylcyclobutanones (2-ACBs) are uniquely formed when triglycerides-containing food products are exposed to ionizing radiation. Thus, 2-ACBs have been used as marker molecules to identify irradiated food. Most methods to determine 2-ACBs involve mass spectrometric detection after chromatographic separation. The spectrofluorometer is rarely used to determine 2-ACBs because these molecules do not fluoresce. In this study, we developed an ultra-performance liquid chromatography (UPLC) method to determine 2-ACBs. 2-ACBs were converted into fluorophores after reacting with 1-naphthalenyl hydrazine to facilitate their sensitive and selective detection using a fluorescence detector (FLD). Analysis of 2-ACBs using our developed UPLC-FLD method allows sensitive determination of 2-ACBs at a detection limit of 2 ng 2-ACBs per g of fat (30 pg/injection), which is significantly lower than that of existing analytical methods. After validation for trueness and precision, the method was applied to γ-irradiated chicken samples to determine their 2-ACB content. Comparative studies employing liquid chromatography-tandem mass spectrometric method revealed no systematic difference between the two methods, thereby demonstrating that the proposed UPLC-FLD method can be suitably used to determine 2-ACBs in irradiated foodstuffs. Graphical Abstract Determination of radiation-induced food-borne 2-dodecylcyclobutanone and 2-tetradecylcyclobutanone by combining 1-naphthalenyl hydrazine derivatization and ultra-performance liquid chromatography with fluorescence detection.

Mass Spectrometric Approaches to the Identification of Potential Ingredients in Cigarette Smoke Causing Cytotoxicity.

Cigarette smoke contains many harmful chemicals that contribute to the pathogenesis of smoking-related diseases such as chronic obstructive pulmonary disease, cancer, and cardiovascular disease. Many studies have been done to identify cytotoxic chemicals in cigarette smoke and elucidate the onset of the above-mentioned diseases caused by smoking. However, definitive mechanisms for cigarette smoke toxicity remain unknown. As candidates for cytotoxic chemicals, we have recently found methyl vinyl ketone (MVK) and acetic anhydride in nicotine/tar-free cigarette smoke extract (CSE) using L-tyrosine (Tyr), an amino acid with highly reactive hydroxyl group. The presence of MVK and acetic anhydride in CSE was confirmed by gas chromatography-mass spectrometry (GC/MS). We also found new reaction products formed in B16-BL6 mouse melanoma (B16-BL6) cells treated with CSE using LC/MS. These were identified as glutathione (GSH) conjugates of α,ß-unsaturated carbonyl compounds, MVK, crotonaldehyde (CA), and acrolein (ACR), by the mass value and product ion spectra of these new products. ACR and MVK are type-2 alkenes, which are well known as electron acceptors and form Michael-type adducts to nucleophilic side chain of amino acids on peptides. These α,ß-unsaturated carbonyl compounds may have a key role in CSE-induced cell death.

Kinetics studies on the removal of Methyl ethyl ketone using cornstack based biofilter.

The performance of cornstack based biofilter inoculated with a mixed culture was evaluated for gas phase MEK removal under various operating conditions. Experiments were carried out at different flow rates (0.03-0.12m3h-1) and various initial concentrations (0.2-1.2g-3). A maximum elimination capacity (EC) of 35g-3h-1 was achieved at an inlet loading rate of 60g-3h-1 with a removal efficiency of 95%. High elimination capacity reached with this system could have been due to the dominant presence of filamentous fungi among others. The experimental results were compared with the values obtained from the Ottengraf-van den Oever model for zero-order diffusion-controlled region. The critical inlet concentration, critical inlet load and biofilm thickness were estimated using the model predictions.

Hexavalent chromium and isocyanate exposures during military aircraft painting under crossflow ventilation.

Exposure control systems performance was investigated in an aircraft painting hangar. The ability of the ventilation system and respiratory protection program to limit worker exposures was examined through air sampling during painting of F/A-18C/D strike fighter aircraft, in four field surveys. Air velocities were measured across the supply filter, exhaust filter, and hangar midplane under crossflow ventilation. Air sampling conducted during painting process phases (wipe-down, primer spraying, and topcoat spraying) encompassed volatile organic compounds, total particulate matter, Cr[VI], metals, nitroethane, and hexamethylene diisocyanate, for two worker groups: sprayers and sprayer helpers ("hosemen"). One of six methyl ethyl ketone and two of six methyl isobutyl ketone samples exceeded the short term exposure limits of 300 and 75 ppm, with means 57 ppm and 63 ppm, respectively. All 12 Cr[VI] 8-hr time-weighted averages exceeded the recommended exposure limit of 1 µg/m3, 11 out of 12 exceeded the permissible exposure limit of 5 µg/m3, and 7 out of 12 exceeded the threshold limit value of 10 µg/m3, with means 38 µg/m3 for sprayers and 8.3 µg/m3 for hosemen. Hexamethylene diisocyanate means were 5.95 µg/m3 for sprayers and 0.645 µg/m3 for hosemen. Total reactive isocyanate group--the total of monomer and oligomer as NCO group mass--showed 6 of 15 personal samples exceeded the United Kingdom Health and Safety Executive workplace exposure limit of 20 µg/m3, with means 50.9 µg/m3 for sprayers and 7.29 µg/m3 for hosemen. Several exposure limits were exceeded, reinforcing continued use of personal protective equipment. The supply rate, 94.4 m3/s (200,000 cfm), produced a velocity of 8.58 m/s (157 fpm) at the supply filter, while the exhaust rate, 68.7 m3/s (146,000 cfm), drew 1.34 m/s (264 fpm) at the exhaust filter. Midway between supply and exhaust locations, the velocity was 0.528 m/s (104 fpm). Supply rate exceeding exhaust rate created re-circulations, turbulence, and fugitive emissions, while wasting energy. Smoke releases showing more effective ventilation here than in other aircraft painting facilities carries technical feasibility relevance.

[Determination of 1-hydroxy-2-butanone in urine by gas chromatography].

Objective: To establish a method for the determination of 1-hydroxy-2-butanone in urine by gas chromatography. Methods: Urine samples were acidified with hydrochloric acid, and then stored in the refrigerator . After thawing under natural conditions, urine volume of 2.0 ml was extracted by C18 solid phase, using methanol volume of 2.0 ml elution, detected by gas chromatography with FID detector and quantified by external standard method. Results: The measurement range of method is 0.986 ~32.88 µg/ml, correlation coefficient (r) =0.999 7, detection limit is 0.13 µg/ml; The recovery is 88.1% ~92.2% ; The precision is 1.4% ~3.2%. Conclusion: This method has a high sensitivity and simple processing. All technical indicators can meet the requirements of the determination method.

Bidirectional Flux of Methyl Vinyl Ketone and Methacrolein in Trees with Different Isoprenoid Emission under Realistic Ambient Concentrations.

Methyl vinyl ketone (MVK) and methacrolein (MAC) are key oxidation products (iox) of isoprene, the most abundant volatile organic compound (VOC) emitted by vascular plants in the atmosphere. Increasing attention has been dedicated to iox, as they are involved in the photochemical cycles ultimately leading to ozone (O3) and particle formation. However, the capacity of plants to exchange iox under low and realistic ambient concentrations of iox needs to be assessed. We hypothesized that a foliar uptake of iox exists even under realistic concentrations of iox. We tested the capacity of iox exchange in trees constitutively emitting isoprene (Populus nigra) or monoterpenes (Quercus ilex), or that do not emit isoprenoids (Paulownia imperialis). Laboratory experiments were carried out at the leaf level using enclosures under controlled environmental factors and manipulating isoprene and reactive oxygen species (ROS) production by using the isoprene specific inhibitor fosmidomycin, acute O3 exposure (300 ppbv for 4 h), and dark conditions. We also tested whether stress conditions inducing accumulation of ROS significantly enhance iox formation in the leaf, and their emission. Our results show a negligible level of constitutive iox emission in unstressed plants, and in plants treated with high O3. The uptake of iox increased linearly with exposure to increasing concentrations of ambient iox (from 0 to 6 ppbv of a 1:1 = MVK/MAC mixture) in all the investigated species, indicating iox fast removal and low compensation point in unstressed and stressed conditions. Plant capacity to take up iox should be included in global models that integrate estimates of iox formation, emission, and photochemical reactions in the atmosphere.

Matrix-bound 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone in tobacco: quantification and evidence for an origin from lignin-incorporated alkaloids.

Substantial quantities of the carcinogenic tobacco-specific N-nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (1; NNK) are still found in the mainstream smoke of tobacco exhaustively extracted with water, indicating the presence of an insoluble, matrix-bound form. Soluble and matrix-bound concentrations of 1 in tobacco were determined by applying a new method using sequential aqueous extraction at room temperature and at 130 °C. On average, 77% and 53% of the total content of 1 were matrix-bound in air-cured (Burley type) and flue-cured tobaccos, respectively. Thermal release of 1 from its matrix-bound form above ca. 200 °C can account for a large fraction of its concentration in cigarette mainstream smoke. An already matrix-bound alkaloid precursor of matrix-bound 1 was identified in vascular tissue of green leaf midribs. The incubation of vascular cell-wall preparations with the lignin precursor coniferyl alcohol and isotopically labeled nicotine or pseudooxynicotine (2) led to the formation of labeled matrix-bound 1 after nitrosation, suggesting that incorporation of nicotine or its oxidized product 2 during lignin polymerization is the origin of the formation of matrix-bound 1.

Butane-2,3-dione: the key contributor to axillary and foot odor associated with an acidic note.

Human body odor, which contains several volatile organic compounds, possesses various odor qualities. To identify key volatile compounds responsible for the common unpleasant odors derived from human axillae and feet, the odor quality and intensity of 118 human axillae and feet were directly evaluated by sniffing, and odor compounds obtained from the subjects were identified. Furthermore, the sensory differences in odor intensity and quality with and without addition of butane-2,3-dione were evaluated by using the visual analog scale (VAS). An acidic odor was a common unpleasant note in human axillae and feet. Butane-2,3-dione was identified as a key compound associated with this odor. Strong positive correlations between the amount of butane-2,3-dione, and the odor intensities of axillae and feet were observed, and the addition of butane-2,3-dione solution to blended short-chain fatty-acid solutions caused significantly increased VAS values of axillary-like odor, unpleasantness, and odor intensity compared to those of each solution without added butane-2,3-dione.

[Indoor air guide values for 2-butanone oxime. Communication from the Ad-hoc Working Group on Indoor Guide Values of the Indoor Air Hygiene Commission and the States' Supreme Health Authorities]. / Richtwerte für Butanonoxim in der Innenraumluft : Mitteilung der Ad-hoc-Arbeitsgruppe Innenraumrichtwerte der Kommission Innenraumlufthygiene und der Obersten Landesgesundheitsbehörden.

The German Working Group on Indoor Guidelines of the Indoor Air Hygiene Committee and of the Supreme State Health Authorities is issuing indoor air guide values to protect public health. No reliable human studies are available for health evaluation of 2-butanone oxime in indoor air. In a well documented chronic inhalation animal study with rats and mice assessed as reliable, degenerative changes in the olfactory epithelium were observed, which led to a dose related increased incidence and severity, especially in mice. Using a benchmark approach the Working Group assessed a BMD10 of 13.8 mg 2-butanone oxime/m(3) for continuous exposure for the endpoint degeneration of the olfactory epithelium. For interspecies differences a reduced factor of 1 was applied due to the same susceptibility of rodents than human for this endpoint. By applying a factor of 10 for interindividual variability, and a factor of 2 to account for the higher respiratory rate of children compared to adults, a health hazard guide value (RW II) of 0.06 mg 2-butanone oxime/m(3) indoor air is obtained. A precautionary guide value of 0.02 mg 2-butanone oxime/m(3) indoor air is recommended.

Demonstration of fast and accurate discrimination and quantification of chemically similar species utilizing a single cross-selective chemiresistor.

Performance characteristics of gas-phase microsensors will determine the ultimate utility of these devices for a wide range of chemical monitoring applications. Commonly employed chemiresistor elements are quite sensitive to selected analytes, and relatively new methods have increased the selectivity to specific compounds, even in the presence of interfering species. Here, we have focused on determining whether purposefully driven temperature modulation can produce faster sensor-response characteristics, which could enable measurements for a broader range of applications involving dynamic compositional analysis. We investigated the response speed of a single chemiresitive In2O3 microhotplate sensor to four analytes (methanol, ethanol, acetone, 2-butanone) by systematically varying the oscillating frequency (semicycle periods of 20-120 ms) of a bilevel temperature cycle applied to the sensing element. It was determined that the fastest response (≈ 9 s), as indicated by a 98% signal-change metric, occurred for a period of 30 ms and that responses under such modulation were dramatically faster than for isothermal operation of the same device (>300 s). Rapid modulation between 150 and 450 °C exerts kinetic control over transient processes, including adsorption, desorption, diffusion, and reaction phenomena, which are important for charge transfer occurring in transduction processes and the observed response times. We also demonstrate that the fastest operation is accompanied by excellent discrimination within a challenging 16-category recognition problem (consisting of the four analytes at four separate concentrations). This critical finding demonstrates that both speed and high discriminatory capabilities can be realized through temperature modulation.

A novel breath test to directly measure use of vaginal gel and condoms.

We assessed the feasibility of a breath test to detect women's single or concurrent use of vaginal products by adding ester taggants to vaginal gel and condom lubricant. Healthy non-pregnant women were enrolled into a two-day cohort (N = 13) and a single-day cohort (N = 12) in San Francisco. Within each cohort, women were randomized (5:1) to tagged or untagged products, and inserted in a clinical setting: 4 mL of tenofovir placebo gel (ten tagged with 15 mg 2-pentyl acetate; three untagged), and an artificial phallus with a lubricated condom (11 tagged with 15 mg 2-butyl acetate; two untagged), on two separate days (two-day cohort) or concurrently (single-day cohort). Using a portable mini-gas chromatograph, the presence/absence of taggants was determined in breath specimens collected prior to, and at timed intervals following product exposure. Demographic, clinical and product use experience data were collected by structured interview. All participants completed all visits and inserted their assigned products. At 5 min post-insertion, the breath test was 100% accurate in identifying insertion of the tagged (or untagged) gel and/or condom. The half-life in breath of the two esters tested was <1 h with large variability between individuals, taggants and cohorts. Overall, among those receiving tagged product, six mild and two moderate product-related AEs were reported. All were transient and resolved spontaneously. Additional sensations included taste in mouth (N = 4) and scent (N = 5). The tagged products were well tolerated. This breath test has the potential to accurately and objectively monitor adherence to vaginal gel and condom used separately or concurrently.

Phospholipase A2 inhibitors synthesized by two entomopathogenic bacteria, Xenorhabdus nematophila and Photorhabdus temperata subsp. temperata.

The entomopathogenic bacteria Xenorhabdus nematophila and Photorhabdus temperata subsp. temperata suppress insect immune responses by inhibiting the catalytic activity of phospholipase A(2) (PLA(2)), which results in preventing biosynthesis of immune-mediating eicosanoids. This study identified PLA(2) inhibitors derived from culture broths of these two bacteria. Both X. nematophila and P. temperata subsp. temperata culture broths possessed significant PLA(2)-inhibitory activities. Fractionation of these bacterial metabolites in the culture broths using organic solvent and subsequent chromatography purified seven potent PLA(2) inhibitors, three of which (benzylideneacetone [BZA], proline-tyrosine [PY], and acetylated phenylalanine-glycine-valine [FGV]) were reported in a previous study. Four other compounds (indole, oxindole, cis-cyclo-PY, and p-hydroxyphenyl propionic acid) were identified and shown to significantly inhibit PLA(2). X. nematophila culture broth contained these seven compounds, while P. temperata subsp. temperata culture broth contained three compounds (BZA, acetylated FGV, and cis-cyclo-PY). BZA was detected in the largest amount among these PLA(2) compounds in both bacterial culture broths. All seven bacterial metabolites also showed significant inhibitory activities against immune responses, such as phenoloxidase activity and hemocytic nodulation; BZA was the most potent. Finally, this study characterized these seven compounds for their insecticidal activities against the diamondback moth, Plutella xylostella. Even though these compounds showed relatively low toxicities to larvae, they significantly enhanced the pathogenicity of Bacillus thuringiensis. This study reports bacterial-origin PLA(2) inhibitors, which would be applicable for developing novel insecticides.

Quantitative information in decay curves obtained with a pulsed ion mobility spectrometer.

Ion mobility spectrometry (IMS) is well known for its very high sensitivity, and thus IMS spectra are commonly used in the identification of trace gases. Extracting quantitative information from IMS spectra is, in contrast, difficult, especially regarding the reproducibility due to the nature of the processes involved in the measurement of the spectra. Here we present data extracted from signal decay curves obtained with a pulsed IMS, which can support the determination of substance concentrations in the lower ppb range with good stability.

Simultaneous determination of nabumetone and its principal metabolite in medicines and human urine by time-resolved fluorescence.

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.