Identification of Volatile Compounds and Selection of Discriminant Markers for Elephant Dung Coffee Using Static Headspace Gas Chromatography-Mass Spectrometry and Chemometrics.

Elephant dung coffee (Black Ivory Coffee) is a unique Thai coffee produced from Arabica coffee cherries consumed by Asian elephants and collected from their feces. In this work, elephant dung coffee and controls were analyzed using static headspace gas chromatography hyphenated with mass spectrometry (SHS GC-MS), and chemometric approaches were applied for multivariate analysis and the selection of marker compounds that are characteristic of the coffee. Seventy-eight volatile compounds belonging to 13 chemical classes were tentatively identified, including six alcohols, five aldehydes, one carboxylic acid, three esters, 17 furans, one furanone, 13 ketones, two oxazoles, four phenolic compounds, 14 pyrazines, one pyridine, eight pyrroles and three sulfur-containing compounds. Moreover, four potential discriminant markers of elephant dung coffee, including 3-methyl-1-butanol, 2-methyl-1-butanol, 2-furfurylfuran and 3-penten-2-one were established. The proposed method may be useful for elephant dung coffee authentication and quality control.

Virgin olive oil quality of hedgerow 'Arbequina' olive trees under deficit irrigation.

BACKGROUND: Regulated deficit irrigation (RDI) is used in hedgerow olive orchards to achieve a sustainable balance between water savings, tree vigor and oil production. Its effects on the presence of compounds responsible for the taste of the oil and its nutritional value are controversial. The present 3-year study was conducted in an 'Arbequina' orchard (1667 trees ha-1 ) under a full irrigation (FI) treatment (470.1 mm year-1 of water) and two RDI treatments scaled to replace 60% and 30%, respectively, of FI. The quality parameters, antioxidant contents and volatiles of the extracted virgin olive oil (VOO) were analyzed. RESULTS: In general, oils from the 30% RDI treatment had higher contents of pigments and phenolic compounds, a higher oleic/linoleic ratio and the highest oxidative stability, despite their lower tocopherol content. FI oils showed higher (E)-2-hexenal, 1-penten-3-one, ocimene, E-2-pentenal and pentene dimer contents than 30RDI oils, but lower contents of (E)-2-pentenol and volatile esters. CONCLUSION: The results of the present study suggest that a RDI strategy supplying 30% of the total irrigation needs induces an increase in natural antioxidants in VOO. Neither yield, nor the rest of the quality parameters were affected by the reduced irrigation. However, abundant autumn precipitation can over-ride these effects of 30% RDI treatment on oil quality. © 2016 Society of Chemical Industry.

Increased sensitivity of OSHA method analysis of diacetyl and 2,3-pentanedione in air.

Gas chromatography/mass spectrometry (GC/MS) operated in selected ion monitoring mode was used to enhance the sensitivity of OSHA Methods 1013/1016 for measuring diacetyl and 2,3-pentanedione in air samples. The original methods use flame ionization detection which cannot achieve the required sensitivity to quantify samples at or below the NIOSH recommended exposure limits (REL: 5 ppb for diacetyl and 9.3 ppb for 2,3-pentanedione) when sampling for both diacetyl and 2,3-pentanedione. OSHA Method 1012 was developed to measure diacetyl at lower levels but requires an electron capture detector, and a sample preparation time of 36 hours. Using GC/MS allows detection of these two alpha-diketones at lower levels than OSHA Method 1012 for diacetyl and OSHA Method 1016 for 2,3-pentanedione. Acetoin and 2,3-hexanedione may also be measured using this technique. Method quantification limits were 1.1 ppb for diacetyl (22% of the REL), 1.1 ppb for 2,3-pentanedione (12% of the REL), 1.1 ppb for 2,3-hexanedione, and 2.1 ppb for acetoin. Average extraction efficiencies above the limit of quantitation were 100% for diacetyl, 92% for 2,3-pentanedione, 89% for 2,3-hexanedione, and 87% for acetoin. Mass spectrometry with OSHA Methods 1013/1016 could be used by analytical laboratories to provide more sensitive and accurate measures of exposure to diacetyl and 2,3-pentanedione.

Identification of signature volatiles to discriminate Candida albicans, glabrata, krusei and tropicalis using gas chromatography and mass spectrometry.

Oral candidiasis is the most frequent fungal infection of the oral cavity. Clinical diagnoses require mycological confirmation, which is time-consuming in case of culture testing. The aim of the study was to identify signature volatiles to develop a chairside breath test to diagnose oral candidiasis. Headspaces above Candida albicans, glabrata, tropicalis, krusei cultures, and growth media as control were analysed after eight and 24 h using offline gas chromatography and mass spectrometry. The identification of signature volatiles was assisted using various microbial databases. Retrieved volatile patterns enabled Candida species discrimination in vitro. For C. albicans 3-methyl-2-butanone and styrene and for C. krusei a combination of p-xylene, 2-octanone, 2-heptanone and n-butyl acetate were found to be specific. 1-hexanol was found in C. tropicalis, but is emitted by a variety of other microorganisms. C. glabrata was characterised through the absence of these volatiles. The development of a breath test is a promising approach in confirming suspicions of oral candidiasis. To confirm the retrieved results in vivo, breath tests in affected and healthy subjects have to be performed.

Environmental characterization of a coffee processing workplace with obliterative bronchiolitis in former workers.

Obliterative bronchiolitis in five former coffee processing employees at a single workplace prompted an exposure study of current workers. Exposure characterization was performed by observing processes, assessing the ventilation system and pressure relationships, analyzing headspace of flavoring samples, and collecting and analyzing personal breathing zone and area air samples for diacetyl and 2,3-pentanedione vapors and total inhalable dust by work area and job title. Mean airborne concentrations were calculated using the minimum variance unbiased estimator of the arithmetic mean. Workers in the grinding/packaging area for unflavored coffee had the highest mean diacetyl exposures, with personal concentrations averaging 93 parts per billion (ppb). This area was under positive pressure with respect to flavored coffee production (mean personal diacetyl levels of 80 ppb). The 2,3-pentanedione exposures were highest in the flavoring room with mean personal exposures of 122 ppb, followed by exposures in the unflavored coffee grinding/packaging area (53 ppb). Peak 15-min airborne concentrations of 14,300 ppb diacetyl and 13,800 ppb 2,3-pentanedione were measured at a small open hatch in the lid of a hopper containing ground unflavored coffee on the mezzanine over the grinding/packaging area. Three out of the four bulk coffee flavorings tested had at least a factor of two higher 2,3-pentanedione than diacetyl headspace measurements. At a coffee processing facility producing both unflavored and flavored coffee, we found the grinding and packaging of unflavored coffee generate simultaneous exposures to diacetyl and 2,3-pentanedione that were well in excess of the NIOSH proposed RELs and similar in magnitude to those in the areas using a flavoring substitute for diacetyl. These findings require physicians to be alert for obliterative bronchiolitis and employers, government, and public health consultants to assess the similarities and differences across the industry to motivate preventive intervention where indicated by exposures above the proposed RELs for diacetyl and 2,3-pentanedione.

Evaluation of electronic cigarette liquids and aerosol for the presence of selected inhalation toxins.

INTRODUCTION: The purpose of this study was to evaluate sweet-flavored electronic cigarette (EC) liquids for the presence of diacetyl (DA) and acetyl propionyl (AP), which are chemicals approved for food use but are associated with respiratory disease when inhaled. METHODS: In total, 159 samples were purchased from 36 manufacturers and retailers in 7 countries. Additionally, 3 liquids were prepared by dissolving a concentrated flavor sample of known DA and AP levels at 5%, 10%, and 20% concentration in a mixture of propylene glycol and glycerol. Aerosol produced by an EC was analyzed to determine the concentration of DA and AP. RESULTS: DA and AP were found in 74.2% of the samples, with more samples containing DA. Similar concentrations were found in liquid and aerosol for both chemicals. The median daily exposure levels were 56 µg/day (IQR: 26-278 µg/day) for DA and 91 µg/day (IQR: 20-432 µg/day) for AP. They were slightly lower than the strict NIOSH-defined safety limits for occupational exposure and 100 and 10 times lower compared with smoking respectively; however, 47.3% of DA and 41.5% of AP-containing samples exposed consumers to levels higher than the safety limits. CONCLUSIONS: DA and AP were found in a large proportion of sweet-flavored EC liquids, with many of them exposing users to higher than safety levels. Their presence in EC liquids represents an avoidable risk. Proper measures should be taken by EC liquid manufacturers and flavoring suppliers to eliminate these hazards from the products without necessarily limiting the availability of sweet flavors.

Respiratory morbidity in a coffee processing workplace with sentinel obliterative bronchiolitis cases.

RATIONALE: Obliterative bronchiolitis in former coffee workers prompted a cross-sectional study of current workers. Diacetyl and 2,3-pentanedione levels were highest in areas for flavoring and grinding/packaging unflavored coffee. METHODS: We interviewed 75 (88%) workers, measured lung function, and created exposure groups based on work history. We calculated standardized morbidity ratios (SMRs) for symptoms and spirometric abnormalities. We examined health outcomes by exposure groups. RESULTS: SMRs were elevated 1.6-fold for dyspnea and 2.7-fold for obstruction. The exposure group working in both coffee flavoring and grinding/packaging of unflavored coffee areas had significantly lower mean ratio of forced expiratory volume in 1 s to forced vital capacity and percent predicted mid-expiratory flow than workers without such exposure. CONCLUSION: Current workers have occupational lung morbidity associated with high diacetyl and 2,3-pentanedione exposures, which were not limited to flavoring areas.

[Determination of methyl propyl ketone in air of workplace by capillary gas chromatography].

OBJECTIVE: To establish a gas chromatography method for determination of methyl propyl ketone in the air of workplace. METHODS: Methyl propyl ketone in the air of workplace was collected with activated carbon tubes and desorbed with carbon disulfide before sample loading. The target toxicant was separated with the capillary column and detected with a hydrogen flame ionization detector, identified by retention time, and quantified by peak area. RESULTS: The linear range of methyl propyl ketone in the air of workplace was 202.5∼4 860.0 µg/ml, with a correlation coefficient of 0.999 98. The limit of detection was 1.5 µg/ml. The lower limit of quantification was 5.0 µg/ml. The minimum detectable concentration was 1.0 mg/m(3) under 1.5 L sampling volume and 1.0 ml desorption solution volume. The relative standard deviation of different methyl propyl ketone concentrations was 1.42%∼1.65%, and the recovery rate was 94.9%∼ 97.9%. CONCLUSION: This method has high sensitivity, precision, and accuracy, and it is applicable for determination of methyl propyl ketone in the air of workplace.

Model Predictions of Occupational Exposures to Diacetyl and 2,3-Pentanedione Emitted From Roasted Whole Bean and Ground Coffee: Influence of Roast Level and Physical Form on Specific Emission Rates.

Roasted coffee emits hazardous volatile organic compounds including diacetyl and 2,3-pentanedione. Workers in non-flavored coffee roasting and packaging facilities might inhale diacetyl and 2,3-pentanedione from roasted coffee above occupational exposure limits depending on their work activities and proximity to the source of emissions. Objectives of this laboratory study were to: (1) investigate factors affecting specific emission rates (SERs) of diacetyl and 2,3-pentanedione from freshly roasted coffee, (2) explore the effect of time on SERs of coffee stored in sealed bags for 10-days, and (3) predict exposures to workers in hypothetical workplace scenarios. Two roast levels (light and dark) and three physical forms (whole bean, coarse ground, and fine ground) were investigated. Particle size for whole bean and ground coffee were analyzed using geometric mean of Feret diameter. Emitted chemicals were collected on thermal desorption tubes and quantified using mass spectrometry analysis. SERs developed here coupled with information from previous field surveys provided model input to estimate worker exposures during various activities using a probabilistic, near-field/far-field model. For freshly roasted coffee, mean SER of diacetyl and 2,3-pentantedione increased with decreasing particle size of the physical form (whole bean < coarse ground < fine ground) but was not consistent with roast levels. SERs from freshly roasted coffee increased with roast level for diacetyl but did not change for 2,3-pentanedione. Mean SERs were greatest for diacetyl at 3.60 mg kg-1 h-1 for dark, fine ground and for 2,3-pentanedione at 3.88 mg kg-1 h-1 for light, fine ground. For storage, SERs of whole bean remained constant while SERs of dark roast ground coffee decreased and light roast ground coffee increased. Modeling demonstrated that near-field exposures depend on proximity to the source, duration of exposure, and air velocities in the near-field further supporting previously reported chemical air measurements in coffee roasting and packaging facilities. Control of source emissions using local exhaust ventilation especially around grinding activities as well as modification of work practices could be used to reduce exposures in this workforce.

Impacts of risk assessment data, assumptions, and methods: Considering the evidence for diacetyl and 2,3-pentanedione.

The articles published as part of the Frontiers in Public Health research topic, "Investigating exposures and respiratory health in coffee workers" present research findings that better characterize exposures to diacetyl and 2,3-pentanedione and inform our understanding of the health risks posed by these exposures. Although various research groups and organizations have conducted risk assessments to derive occupational exposure limits (OELs) for diacetyl, differences in the data used and assumptions made in these efforts have resulted in a wide range of recommended OELs designed to protect human health. The primary drivers of these differences include the decision to use data from human or animal studies in conducting a quantitative risk assessment, and the application of uncertainty factors (UF) to derive an OEL. This Perspectives paper will discuss the practical implications of these decisions, and present additional commentary on the potential role that the recent investigation of human exposures to relatively low concentrations of α-diketones, specifically diacetyl and 2,3-pentanedione, may play in supporting qualitative or quantitative human health risk assessments.

Determinants of Task-Based Exposures to Alpha-Diketones in Coffee Roasting and Packaging Facilities Using a Bayesian Model Averaging Approach.

Coffee production workers can be exposed to inhalational hazards including alpha-diketones such as diacetyl and 2,3-pentanedione. Exposure to diacetyl is associated with the development of occupational lung disease, including obliterative bronchiolitis, a rare and irreversible lung disease. We aimed to identify determinants contributing to task-based exposures to diacetyl and 2,3-pentanedione at 17 U.S. coffee production facilities. We collected 606 personal short-term task-based samples including roasting (n = 189), grinding (n = 74), packaging (n = 203), quality control (QC, n = 44), flavoring (n = 15), and miscellaneous production/café tasks (n = 81), and analyzed for diacetyl and 2,3-pentanedione in accordance with the modified OSHA Method 1013/1016. We also collected instantaneous activity-based (n = 296) and source (n = 312) samples using evacuated canisters. Information on sample-level and process-level determinants relating to production scale, sources of alpha-diketones, and engineering controls was collected. Bayesian mixed-effect regression models accounting for censored data were fit for overall data (all tasks) and specific tasks. Notable determinants identified in univariate analyses were used to fit all plausible models in multiple regression analysis which were summarized using a Bayesian model averaging method. Grinding, flavoring, packaging, and production tasks with ground coffee were associated with the highest short-term and instantaneous-activity exposures for both analytes. Highest instantaneous-sources of diacetyl and 2,3-pentanedione included ground coffee, flavored coffee, liquid flavorings, and off-gassing coffee bins or packages. Determinants contributing to higher exposures to both analytes in all task models included sum of all open storage sources and average percent of coffee production as ground coffee. Additionally, flavoring ground coffee and flavoring during survey contributed to notably higher exposures for both analytes in most, but not all task groups. Alternatively, general exhaust ventilation contributed to lower exposures in all but two models. Additionally, among facilities that flavored, local exhaust ventilation during flavoring processes contributed to lower 2,3-pentanedione exposures during grinding and packaging tasks. Coffee production facilities can consider implementing additional exposure controls for processes, sources, and task-based determinants associated with higher exposures to diacetyl and 2,3-pentanedione, such as isolating, enclosing, and directly exhausting grinders, flavoring mixers, and open storage of off-gassing whole bean and ground coffee, to reduce exposures and minimize risks for lung disease among workers.

Fatal intoxication involving 4-methylpentedrone (4-MPD) in a context of chemsex.

4-methylpentedrone (4-MPD) is a new psychoactive substance (NPS) belonging to the cathinone class. We report an original case of death mainly involving 4-MPD, along with cocaine, sildenafil, bromazepam and nevirapine. The investigation data and the autopsy findings indicated fatal intoxication in a chemsex context (drug use during sex). 4-MPD concentrations were determined in peripheral blood (1285 ng/mL), cardiac blood (1128 ng/mL), urine (>10,000 ng/mL), bile (1187 ng/mL) and vitreous humor (734 and 875 ng/mL in left and right samples, respectively) by gas chromatography (GC) coupled to tandem mass spectrometry. 4-MPD metabolites were explored by GC coupled to high resolution mass spectrometry. Due to the paucity of data concerning 4-MPD, its use and effects were gathered from online user testimonies. This case illustrates the toxicity of this infrequent pentedrone derivate and confirms the significant overdose risk associated with chemsex.

Multi-target optimization of solid phase microextraction to analyse key flavour compounds in wort and beer.

Despite the literature comprises numerous studies dealing with the analysis of wort and beer flavour-related compounds by HS-SPME followed by GC-MS quantification, no generalized consensus exists regarding the optimal conditions for the extraction procedure. The complex chemistry nature of these matrices, the number of analytes, as well as the number and interactions among parameters affecting the extraction performance, requires the adoption of optimal experimental design protocols. This aspect is often overlooked and often not properly addressed in practice. Therefore, in the present work, the optimal conditions under which a range of wort and beer analytes can be extracted and quantified were analysed. The optimal extraction conditions were presented at two levels of aggregation: global (untargeted) and key-flavour analysis. Experimental data was generated by Definitive-Screening-Design, followed by model development and optimization. Both approaches were compared and critically analysed. For vicinal-diketones group, a complete validation study for the optimal conditions is presented.

Understanding retention and metabolization of aroma compounds using an in vitro model of oral mucosa.

The mechanism leading to aroma persistence during eating is not fully described. This study aims at better understanding the role of the oral mucosa in this phenomenon. Release of 14 volatile compounds from different chemical classes was studied after exposure to in vitro models of oral mucosa, at equilibrium by Gas-Chromatography-Flame Ionization Detection (GC-FID) and in dynamic conditions by Proton Transfer Reaction- Mass Spectrometry (PTR-MS). Measurements at equilibrium showed that mucosal hydration reduced the release of only two compounds, pentan-2-one and linalool (p < 0.05), and suggested that cells could metabolize aroma compounds from different chemical families (penta-2,3-dione, trans-2-hexen-1-al, ethyl hexanoate, nonan- and decan-2-one). Dynamic analyses for pentan-2-one and octan-2-one evidenced that the constituents of the mucosal pellicle influenced release kinetics differently depending on molecule hydrophobicity. This work suggests that mucosal cells can metabolize aroma compounds and that non-covalent interactions occur between aroma compounds and oral mucosa depending on aroma chemical structure.

Determination of New Psychoactive Substances in Whole Blood Using Microwave Fast Derivatization and Gas Chromatography/Mass Spectrometry.

The production and consumption of new psychoactive substances (NPSs) has been raising a major concern worldwide. Due to easy access and available information, many NPSs continue to be synthesized with an alarming increase of those available to purchase, despite all the control efforts created. A new analytical method was developed and validated to determine a group of phenethylamines and synthetic cathinones: cathinone, flephedrone, buphedrone, 4-MTA, α-PVP, methylone, 2C-P, ethylone, pentylone, MDPV and bromo-dragonFLY in whole blood. A mixed-mode solid phase extraction was applied to 250 µL of sample, and the extracts were derivatized with fast microwave technique before being analyzed by gas chromatography-mass spectrometry (GC-MS). The validation procedure followed the Scientific Working Group for Forensic Toxicology (SWGTOX) guidelines with parameters that included selectivity, linearity, limits of detection and quantification, intra- and inter-day precision and accuracy, recoveries and stability. The method presented linearity between 5 and 500 ng/mL for cathinone, buphedrone, 4-MTA, methylone, 2C-P and bromo-dragonFLY, 10-500 ng/mL for flephedrone, ethylone, pentylone and MDPV, and 40-500 ng/mL for α-PVP, with determination coefficients above 0.99 for all analytes. Recoveries ranged between 70.3% and 116.6%, and regarding intra- and inter-day precision, the relative mean errors were typically lower than 8.6%. The method was successfully applied to over 100 authentic samples from the Laboratory of Chemistry and Forensic Toxicology, Centre Branch, of the National Institute of Legal Medicine and Forensic Sciences, Portugal.

Potential Hazards Not Communicated in Safety Data Sheets of Flavoring Formulations, Including Diacetyl and 2,3-Pentanedione.

Objectives: Workers using flavoring formulations containing diacetyl and 2,3-pentanedione may be at risk of inhalational exposure, as these volatile hazardous chemicals are emitted from the bulk material, especially at elevated temperatures. However, flavoring formulations that contain diacetyl and 2,3-pentanedione might not list these ingredients because they are generally recognized as safe to ingest, may be part of a proprietary mixture deemed a trade secret, or may not be required to be listed if they are present at <1% composition. The objective of this study was to investigate whether potential inhalational hazards present in flavoring samples were reported as chemical ingredients on their corresponding safety data sheets (SDSs). Methods: A convenience sample of 26 bulk liquid flavorings obtained from two coffee roasting and packaging facilities in the USA was analyzed for 20 volatile organic chemicals present in the headspaces of vials containing flavoring liquids using gas chromatography-mass spectrometry. Flavoring samples were included in the study if headspace analysis results and SDSs were available. Flavoring samples included hazelnut, French vanilla, amaretto, chocolate, and caramel as well as some flavoring mixtures containing added fruit flavors such as cherry and raspberry. The presence of a chemical in the flavoring formulation was then compared to the ingredient list on the SDSs. Results: All the flavoring SDSs contained trade secret designations. None of the SDSs listed diacetyl or 2,3-pentanedione. Headspace analyte concentrations revealed that diacetyl was present in 21 of 26 samples (81%) with a maximum concentration of 5.84 × 10(4) µg m-3 in flavor 18 (caramel). 2,3-Pentanedione was present in 15 flavors (58%) with a maximum concentration of 3.79 × 10(5) µg m-3 in flavor 24 (oatmeal cookies). Conclusions: A majority of the flavorings tested had diacetyl, 2,3-pentanedione, or both as volatile constituents in the headspace. These chemicals were not listed on the SDSs, but inclusion of diacetyl and 2,3-pentanedione on SDSs would serve to protect downstream users from unrecognized exposure and potential respiratory disease. The headspace technique presented here is a viable tool to rapidly screen for volatile hazardous chemicals that may be present in flavoring formulations. Facilities that use flavorings should be aware that constituents in flavorings may present a potential inhalational hazard even if not identified as such by the SDS. A precautionary approach is warranted when working with flavorings, including exposure monitoring and effective exposure control strategies such as containment and local exhaust ventilation.

Measurement of Diacetyl and 2,3-Pentanedione in the Coffee Industry Using Thermal Desorption Tubes and Gas Chromatography-Mass Spectrometry.

Diacetyl is a potentially harmful chemical that is used as an artificial flavouring in the food industry and may also be generated during processing of some natural products including coffee. In Europe, an 8-h time weighted average occupational exposure limit (TWA-OEL) of 20 ppb has been adopted for diacetyl, together with a short-term exposure limit (STEL) of 100 ppb. A new measurement method involving sampling on thermal desorption tubes and analysis by gas chromatography-mass spectrometry has been used to investigate potential exposure to diacetyl, and the related compound 2,3-pentanedione, at eight companies involved in the coffee industry including large- and small-scale manufacturers and coffee shops. A total of 124 static and personal samples were collected. In the majority of personal samples airborne concentrations of diacetyl were <5 ppb, with those at coffee shops generally <1 ppb. However, diacetyl concentrations in ~40% of the long-term personal samples, mainly originating from one site, were found to be in excess of the newly adopted European TWA-OEL of 20 ppb. Diacetyl concentrations up to 400 ppb were detected on the static samples, with the highest values occurring during grinding of roasted coffee beans. 2,3-Pentanedione was also detected in most of the samples at airborne concentrations around half of those for diacetyl. A significant number of other volatile organic compounds (VOCs) were also detected at sub-ppm concentrations, including acetoin, aliphatic carboxylic acids, aldehydes, ketones and esters, methylfuran, furfural and furfuryl-based alcohols and ketones, and nitrogen containing compounds, such as pyridines and pyrazines. In laboratory tests, diacetyl emissions generated during heating of whole beans were found to be significantly lower than those from heating the same beans after grinding. Diacetyl emissions from both ground and whole beans were also found to be significantly dependent on temperature.

A New Method for Workplace Monitoring of Airborne Diacetyl and 2,3-Pentanedione Using Thermal Desorption Tubes and Gas Chromatography-Mass Spectrometry.

Diacetyl is a potentially harmful chemical that is used as an artificial flavouring in the food industry and may also be generated during processing of some natural products including coffee. In Europe, an 8-h time weighted average occupational exposure limit (TWA-OEL) of 20 ppb has been adopted for diacetyl, together with a short-term exposure limit (STEL) of 100 ppb. A sensitive new measurement method for diacetyl, and the related compound 2,3-pentanedione has been developed and evaluated. The new method uses Tenax TA sorbent tubes as the sampling media with analysis by thermal desorption (TD) and gas chromatography-mass spectrometry (GC-MS). The sample tubes are suitable for both active (pumped) and passive (diffusive) sampling. Diacetyl is stable on the sample tubes for at least 3 months but 2,3-pentanedione requires analysis within a month. Sample recovery is unaffected by changes in relative humidity and the presence of acetic acid. For short-term sampling, active sampling is recommended. The safe sampling volume for diacetyl is 3 litres which, at a flow rate of 100 ml min-1, equates to a maximum recommended sampling time of 30 min. For long-term samples, in particular collection of personal samples, passive sampling is recommended. Diffusive uptake rates have been determined for both diacetyl and 2,3-pentanedione on Tenax TA tubes fitted with standard diffusion heads over sampling periods of 1 to 8 h. Analytical limits of detection are approximately 0.2 ng for diacetyl and 0.1 ng for 2,3-pentanedione. These values equate to airborne concentrations of around 0.04 ppb of diacetyl and 0.02 ppb of 2,3-pentanedione for a 1.5-litre active sample and 0.3 ppb of diacetyl and 0.1 ppb of 2,3-pentanedione for an 8-h passive sample. In the case of passive sampling, this limit of detection is less than 1/50th of the new European TWA-OEL for diacetyl of 20 ppb. The method can also be used to identify the presence of other volatile organic compounds at sub-ppm concentrations.