Vapor Samples Research Articles

Milligram mass metrology for quantitative deposition of liquid samples

Quantitative dispensing of liquids by mass becomes increasingly difficult as sample volume decreases. Whereas ml quantities of liquid can be directly weighed as dispensed on an analytical balance or using pycnometer methods, μl samples are more challenging due to their milligram-scale mass and rapid evaporation. Here, a method for quantitative determination of the mass of μl liquid droplets is proposed. The weighing of a microcapillary pycnometer combined with traceable calibration masses and corrections for sample evaporation allows determination of the droplet mass on the order of 1 mg with relative combined expanded uncertainty of 0.3%.

Experimental measurements and modelling of vapour−liquid equilibria for four mixtures of 2,3,3,3−tetrafluoropropene (R1234yf) with 1,1,1,2−tetrafluoroethane (R134a) or 1,1−difluoroethane (R152a) or trans−1−chloro−3,3,3−trifluoropropene (R1233zd(E)) or 2−chloro−3,3,3−trifluoropropene (R1233xf)

Isothermal vapour−liquid equilibrium (VLE) for four binary systems involving R1234yf (R1234yf + R134a, R1234yf + R152a, R1234yf + R1233zd(E) and R1234yf + R1233xf) were measured at temperatures from 278.15 to 348.15 K. The experiments were conducted by means of a “static−analytic” apparatus with phase analysis via gas chromatography, with resulting uncertainties of 0.6 K for temperature, 8 kPa for pressure and a maximum of 0.007 for vapour and liquid mole fractions. The main advantage of the equipment is that vapour and liquid samples are taken from vapour and liquid phases by two capillary samplers (ROLSI®). The Peng Robinson Equation of State is considered to represent the experimental data. If possible, comparison between the new experimental data and prediction with REFPROP 10.0 software are realized.

Nitrocellulose blister material as a source of N-nitrosamine contamination of pharmaceutical drug products

The recent focus of pharmaceutical regulatory authorities has been oriented towards the mitigation of carcinogenic N-nitrosamines in drug products and different sources of N-nitrosamines have been revealed. Within this work, the elucidation of a further source of N-nitrosamines in drug products is reported. A case was investigated where traces of N-nitrosodimethylamine (NDMA) and N-nitrosodiethylamine (NDEA) were detected in a finished dosage form, whereas they were not found in the bulk drug product. This led to an in-depth study of blister material as a potential source, wherein nitrocellulose primer in a lidding foil was identified as a risk factor. Nitrocellulose acts as a nitrosating agent for secondary amines, present in printing inks, forming N-nitrosamines in lidding foil. Their formation was confirmed by the addition of printing ink containing dimethylamine and diethylamine, or diethylamine alone, to lidding foil containing nitrocellulose primer. Their transfer to drug product during the blistering operation was demonstrated by solid-phase microextraction sampling of N-nitrosamine vapors on two commonly used types of pharmaceutical blistering machines, operating with plate sealing or roller sealing technology. Higher vapor amounts were detected on plate sealing equipment, where N-nitrosamine contamination was additionally confirmed in film-coated tablets and blister cavities of the finished dosage form.

Development of a multi-hormone analysis method by LC-MS/MS for environmental water application using diffusive gradient in thin films

An analysis method for four families of hormones (estrogens, progestins, androgens and prostaglandins), dedicated to an efficient water monitoring with passive sampling, was developed using a liquid chromatography tandem mass spectrometry with triple quadrupole coupling and universal electrospray ionisation. Thirteen natural and synthetic hormones in ultra-pure water could be analysed in a single run according to the French Standard NF T90-210: calibration range of 0.1 (except for 17β-Estradiol, Estriol, Estrone and Diethylstilbestrol, from 0.5 μg/L; and Ethinylestradiol, from 1 μg/L) to 20 μg/L with linear regressions (R2 ≥ 0.96), maximum accuracy deviations of 30% at intermediate fidelity for three concentration references (1, 10 and 20 μg/L) and instrumental LOQs from 0.05 to 1 μg/L. The stability of 11 hormones (10 μg/L) was studied under several storage conditions and sample evaporation. All selected hormones were stable for 60 days at −18 °C, 7 days at 4 °C and 7 days at 20 °C but continued drying flow after evaporation should be avoided, especially for 17α-Estradiol, Estrone and Diethylstilbestrol. Observed matrix effects using o-DGT extracts (diffusive gradient in thin-film sampler for polar organics) containing an environmental matrix varied from 24 to 92% but all matrix effects were corrected with IS use. Therefore, the developed method, coupled with o-DGT, was tested with the o-DGT deployment in rivers. Using diffusion coefficients from the literature or lab determined, the concentrations in the rivers varied for Estrone from 1.8 ng/L to 2.5 ng/L, and for Androstenedione from 0.4 to 1.1 ng/L.

A deep learning-driven low-power, accurate, and portable platform for rapid detection of COVID-19 using reverse-transcription loop-mediated isothermal amplification

This paper presents a deep learning-driven portable, accurate, low-cost, and easy-to-use device to perform Reverse-Transcription Loop-Mediated Isothermal Amplification (RT-LAMP) to facilitate rapid detection of COVID-19. The 3D-printed device—powered using only a 5 Volt AC-DC adapter—can perform 16 simultaneous RT-LAMP reactions and can be used multiple times. Moreover, the experimental protocol is devised to obviate the need for separate, expensive equipment for RNA extraction in addition to eliminating sample evaporation. The entire process from sample preparation to the qualitative assessment of the LAMP amplification takes only 45 min (10 min for pre-heating and 35 min for RT-LAMP reactions). The completion of the amplification reaction yields a fuchsia color for the negative samples and either a yellow or orange color for the positive samples, based on a pH indicator dye. The device is coupled with a novel deep learning system that automatically analyzes the amplification results and pays attention to the pH indicator dye to screen the COVID-19 subjects. The proposed device has been rigorously tested on 250 RT-LAMP clinical samples, where it achieved an overall specificity and sensitivity of 0.9666 and 0.9722, respectively with a recall of 0.9892 for Ct < 30. Also, the proposed system can be widely used as an accurate, sensitive, rapid, and portable tool to detect COVID–19 in settings where access to a lab is difficult, or the results are urgently required.

D-depleted water isotopic measurement with a miniaturized cavity ring-down spectrometer aiming for exploration of lunar water

A miniaturized cavity ring-down spectrometer (mini-CRDS) with 5 cm cavity length using a near-infrared laser diode was developed, aiming for exploration of lunar water. This mini-CRDS enables us to measure a water vapor sample of limited amount at low pressure (< 100 Pa) by an unique mechanism using Peltier element modules that changes the resonance point to interpolate the gap of the free spectral range (FSR) of the cavity. We measured aqua samples with different D/H ratios and applied Voigt profile fitting to the absorption spectra, then obtained a calibration line of HDO isotope. The signal to noise ratio (SNR) of HDO peak at δD = − 980‰ was 7.17, which was enough higher than the detection limit of 3.

Determination of tuberculosis-related volatile organic biomarker methyl nicotinate in vapor using fluorescent assay based on quantum dots and cobalt-containing porphyrin nanosheets.

Methyl nicotinate (MN) is a representative and typical volatile organic marker of Mycobacterium tuberculosis, and the specific detection of MN in human breath facilitates non-invasive, rapid, and accurate epidemic screening of tuberculosis infection. Herein, we constructed a fluorescent assay consisted of CdTe quantum dots (QD) and cobalt-metalized tetrakis(4-carboxyphenyl) porphyrin (CoTCPP) nanosheets to determine methyl nicotinate (MN) in vapor samples. Red-emission QD (λex=370 nm, λem=658 nm) acts as signal switches whose fluorescence signals can be effectively quenched by CoTCPP nanosheets but restored in the presence of MN. The strategy relied on the distinct binding affinity of cobalt ion and MN. MN restored the fluorescence of QD quenched by CoTCPP in a concentration-dependent manner, which exhibited a well-linear relationship in the range 1-100 μM, anda limit of detection of0.59 μM. The proposed platform showed sensitivity and selectivity to detect MN in vapor samples with satisfactory RSD below 3.33%. The method ischeap, simple, and relatively rapid (detected within 4 min), which suggestsa potential in tuberculosis diagnosis in resource- and professional-lacked areas.

Paper-Based Optical Nose Made with Bimetallic Nanoparticles for Monitoring Ignitable Liquids in Gasoline.

A paper-based optical nose was fabricated by dropping bimetallic silver and gold nanoparticles on a paper substrate. The nanoparticles were synthesized by both natural (lemon, pomegranate, and orange juices) and chemical (citrate, gallic acid, and ascorbic acid) reducing agents. The performance of the assay was evaluated for identifying gasoline and five ignitable liquids such as diesel, ethanol, methanol, kerosene, and thinner. The interaction of the sensor with sample vapors caused aggregation, consequently changing the color of nanoparticles. The color changes, which were captured by a scanner, represented a specified colorimetric map for each analyte, allowing one to identify the studied fuels. The visual results were confirmed using multivariate statistical analysis such as principal component analysis and hierarchical clustering analysis. Also, partial least-squares regression was used to assist the proposed assay for estimating the amount of studied ignitable liquids as counterfeit species in the gasoline sample. The root-mean-square errors for prediction were 3.4, 2.1, 1.9, 2.0, and 1.7% for diesel, thinner, kerosene, ethanol, and methanol, respectively. Finally, the fabricated sensor indicated high efficiency for the on-site detection of pure industrial gasoline samples from adulterated ones.

Abnormal Respiratory Symptoms of Workers and Sampling of Organic Vapors Using Solid-phase Microextraction Devices in a Golf Ball Manufacturing Factory

The ink that is used in the mark printing, and the protective paints that are sprayed on golf balls as surface and primer layers are the main sources of volatile organic compounds (VOCs) in a golf ball manufacturing factory. In this investigation, workers’ exposures to VOCs were evaluated using a needle trap sampler (NTS), which is a micro sampling device, and the results of an analysis using a gas chromatography mass spectrometer were compared to the samples that were collected in charcoal adsorption tubes with respect to VOC content. Ethyl acetate and n-butyl acetate are main compounds that are emitted in the painting and printing of golf ball. The highest worker time weighted average exposure concentration of n-butyl acetate was 16.92 ppm, and that for ethyl acetate was 19.69 ppm, as measured in a closed spray room. Painters’ and printers’ symptoms of respiratory tract abnormalities (RTA) were strongly correlated with their exposures to organic solvents as determined from the answers to a questionnaire survey on workers’ RTA symptoms. An NTS can be used as an alternative to charcoal tubes for sampling organic solvents to which workers are exposed, based on the differences in the limiting VOC analysis concentrations of both sampling devices. Due to lighter weight and lower cost than the traditional charcoal tube, which has to be connected to a sampling pump, therefore, NTS should be promoted as a routine VOC monitoring device in the workplace.

An unexpected aerobic oxidation of α-amino boronic acid part of Borteomib, leading to (thermal) decomposition of this very expensive anti-cancer API

This project was started when an unknown peak was being detected in the organic volatile impurity (OVI) analysis (using the head-space vapor sampling procedure) of bortezomib (BZB) active pharmaceutical ingredient (API), in pharmaceutical companies. During the OVI analysis of the API of BZB, a huge-area peak with an unknown source appeared in the chromatograms of the gas chromatography with flame ionization detector (GC-FID). The data prepared by GC-MAS revealed that the considered huge peak was 3-methylbutanal (3MBut). But, investigating the synthesis procedures showed that during all the synthesis steps, 3MBut or any other solvent containing this impurity was not being applied. Thus, we had concluded that there is a possibility for emergence of this aldehyde from bortezomib itself. To find out which part of bortezomib might turn into 3MBut, we began to investigate all its molecular structure, and hypothesized that the α-amino-boronic acid part of the molecule turned into 3MBut. The experimental analysis and theoretical quantum chemical calculations confirmed that the α-amino-boronic acid center of bortezomib molecule undergoes a rare and unexpected aerobic oxidation by O2 molecule, even in catalyst and solvent-free conditions. The result of this project not only might make clear the passive source of the 3MBut peak of the OVI of bortezomib, but also, it would suggest to store this API in an inert oxygen-free atmosphere to improve the long-term and accelerated (thermal) stability of this very expensive anti-cancer drug.

Using equilibrium thermodynamics to study thermochemical processes in arc discharges used in atomic emission spectral analysis (review)

Until the beginning of the 21st century, the arc discharge was the main source of excitation of the atomic spectra of elements during routine atomic emission spectral analysis. The wide application of this spectral source at the same time aroused great interest of analysts in the study of complex thermochemical processes occurring at its electrodes and in the discharge plasma. This was due to the need to improve the metrological and informational characteristics of the analysis. Equilibrium thermodynamics has often been used to carry out such studies. It is shown that three levels of the thermodynamic approach can be distinguished here, differing in the complexity of the applied apparatus of thermodynamics and the information content of the results obtained. Numerous examples of the application of these levels of approach to the study of thermochemical processes occurring in the electrode or in the discharge plasma are given. The main advantages and disadvantages of the approaches used, which provide only qualitative information about the ongoing processes, are noted. The main disadvantage is the impossibility of predicting the composition of the arc plasma from the initial composition of the condensed sample. The most informative is the generalized thermodynamic model of thermochemical processes in a DC arc discharge from the sample surface and from the electrode crater. The model is based on the division of a non-stationary non-equilibrium system of an arc discharge into successive quasi-stationary subsystems. They correspond to the stage of sample evaporation and thermochemical transformation of its components in the discharge plasma. According to the model, the total equilibrium composition of the evaporated sample is initially calculated. This determines the initial composition of the arc plasma. Then, the total equilibrium composition of the arc plasma is calculated and the transition to the intensities of the spectral lines of the analytes is performed. The correctness of the generalized model, which gives semi-quantitative results, is confirmed by comparison with experimental data.

The process of making BaM (BaFe12O19) samples based on natural iron sand doped with metal (Co-Cu-Zn) using the coprecipitation method

BaCO3 with natural iron sand is the basic material for making samples of Barium M-Hexaferrite (BaM) which is doped to make the utilization of BaM more effective by adding metal ions that have almost the same size as cobalt (Co), copper (Cu), and Zinc (Zn) and using the coprecipitation method. The process of making Barium M-hexaferrite is carried out in the advanced and basic chemistry laboratory, FMIPA University of Mataram. In this study, variations in concentration and temperature variations during the calcination process were used, namely (x = 0.0; 0.4; 0.8; 1.0) (T = 200; 600; and 1000 °C). These variations greatly affect the sample, where the greater the concentration and temperature of calcination, the color produced in the sample will be darker and this is by the purpose of the calcination process carried out, namely the greater the temperature at the time of calcination, the more water content in the sample will be. reduced because the solvent in the sample evaporation occurs. In addition to these materials, the solvent used also plays an important role in the sample-making process, namely using HCl37% to dissolve, NH4OH 65% so that the deposition process is faster and aquades as a neutralizer.

Capillary electrophoresis-mass spectrometry as a tool for the noninvasive target metabolomic analysis of underivatized amino acids for evaluating embryo viability in assisted reproduction.

Monitoring metabolite uptake and excretion in the culture medium is a noninvasive technique that is used for the metabolic study of cleaving embryos after in vitro fertilization. Low sample consumption, the versatility of the detection, and optimal sensitivity and selectivity are essential elements for extracellular metabolome analyses, and can be conveniently achieved by combining CE with mass spectrometric detection. This paper reports a method for amino acid determination in a limited volume sample (8 μL)ofspent culture media collected after the cultivation of in vitro fertilized embryos. Special attention was focused on the sample preparation procedure. The sample was processed with acetonitrile, which facilitates online sample preconcentration via field-amplified sample stacking, and undesired sample evaporation was significantly reduced by the simultaneous addition of dimethyl sulfoxide. Key parameters that affected electrophoretic separation and mass spectrometric detection were investigated, including the type of buffers and organic solvent, optimization of their concentrations, and finally the settings for their ionization. The separation and quantification of 19 amino acids were achieved using 15% acetic acid as the background electrolyte with a sheath liquid consisting of an equimolar mixture of methanol and water. The applicability of the optimized system was demonstrated by determining the amino acid profile in 40 samples of spent cultivation medium in this pilot study. This developed method also has great potential for amino acid analyses in minute sample volumes of other biological matrices.

Chemical evolution of runoff in Eastern Mediterranean mountainous karstic terrains

The Israeli central mountain rim was chosen to represent the transformation of rain chemical composition to runoff composition in a carbonate landscape under a Mediterranean climate. It was found that at the mostly dolomitic slopes of the Samaria Mountains the main processes shaping runoff chemistry are dissolution of dry fallout (dust) and salts that were precipitated during evaporation of water from previous small-scale runoff events. Calcium and sulfate concentrations in the runoff are defined mainly by the dissolution of dust minerals. The main input of sodium and chloride into runoff composition comes from both rain and dissolution of halite that remained from the evaporation of the previous runoff, whereas the main input of magnesium is connected to dissolution of dolomite outcrops. A combination of forward and inverse modeling by using PHREEQC software was found to be effective for studying runoff chemistry formation. Numerical simulations of runoff sample evaporation have shown that the main minerals precipitating during dry periods are calcite, anhydrite/gypsum, glauberite and halite. The high Na to Cl equivalent ratios (about 1.3 at average) may reflect two-phase dissolution of sulfates and halite in the initial stage that whereas and of glauberite in the following stage. Rainwater transformation to runoff inverse modeling was found to be consistent with the results of forward modeling, confirming these runoff chemical processes.

PhasIR: An Instrumentation and Analysis Software for High-throughput Phase Transition Temperature Measurements

We have designed an open-source and high-throughput thermal analysis system for fast and accurate estimation of phase transition temperatures for up to 96 samples analyzed simultaneously. The results are comparable to current state of the art systems such as differential scanning calorimetry (DSC), which is costly and time-consuming. The PhasIR hardware system utilizes an infrared camera to optically record thermal processes that result from the melting/freezing and/or evaporation of samples, while the accompanying open-source software package allows for subsequent batch analysis and processing to extract phase transition temperatures. The PhasIR system showed good agreement with DSC results for both pure substances and mixtures, such as deep eutectic solvents (DES). The all-in-one hardware and software system can be easily replicated and built using relatively inexpensive components at a total estimated cost of $1,080 USD. Implementation of the PhasIR system will allow for increased throughput in material thermal characterization and broader investigation of material design spaces. <strong>Metadata Overview</strong> Main design files: <a href="https://github.com/pozzo-research-group/phasIR" target="_blank">https://github.com/pozzo-research-group/phasIR</a> Target group: Scientists requiring high-throughput thermal analysis of organic samples (e.g. pharmaceuticals, polymers, food ingredients, greases, solvents). Skills required: CNC machining, 3D printing, basic electronics and programming. Replication: No builds known to the authors so far.

An Improved Procedure for the Determination of Trace Elements in Silicate Rocks Using NH4HF2 Digestion

Knowledge of the elemental composition of geological samples is of high significance to research in Earth science. For whole‐rock elemental determination, complete sample digestion is essential to obtain bias‐free measurement results. In recent years, NH4HF2 digestion has been proposed for geological sample dissolution; however, this requires 3 h of sample evaporation and 6 h of re‐dissolution of residues. In this study a PTFE beaker, which can withstand 300 °C, was designed to increase the evaporation temperature, reducing the evaporation time to 15 min. Further investigations found that the insoluble fluoride residues formed during the high‐temperature evaporation stage significantly influenced the recoveries of Sc, Y, rare earth elements and Th. Among the tested strategies to suppress the formation of fluorides, the microwave heating method was the most efficient and robust. The optimised NH4HF2 digestion shortened the sample evaporation and re‐dissolution times from 9 h to 21 min, significantly reducing the time consumed for sample evaporation by a factor of ~ 26. A suite of silicate rock reference materials was analysed. The results for most elements were in agreement with reference values with a measurement bias of &lt; 10%.

Hypoglycemic and hypolipidemic properties of Casuarina equisetifolia leaf extracts in alloxan induced diabetic rats

BackgroundCausarina equisetifolia is a plant used traditionally as a remedy for various disorders such as diabetes, hyperlipidemia, gastric problems and muscle weakness. The aqueous, ethanol and methanol extracts of C. equisetifolia leaves were studied for hypoglycemic and hypolipidemic potentials. MethodologyPhytochemical analysis was carried out using standard procedures. Rats of both sexes, weighing (145–255 g) were randomly allotted to six groups with each group having four rats. Rats in group A were the normoglycemic, while those in groups B, C, D, E, and F were rendered diabetic by the administration of 110 mg/kg bodyweight of alloxan monohydrate. Group C rats were treated with 15 mg/kg bodyweight of standard drug (Glidazide), while groups D, E, and F rats were respectively treated with 150 mg/kg bodyweight of aqueous, ethanol, and methanol extracts for 15 days. The group B rats were untreated (negative control). Blood glucose was checked after every three days using glucometer. At the end of the treatment, the rats were anaesthetized under chloroform vapor and blood samples were collected by jugular puncture and used for analyzing biochemical parameters. ResultsExtracts showed presence of tannins, flavonoids, saponins, phenols, alkaloids and reducing sugars. There was 64%, 59% and 58% reduction in blood glucose concentration of diabetic rats treated with ethanol, aqueous, methanol extracts respectively. Serum cholesterol and triacylglycerol of the three treated groups reduced (p < 0.05) with the aqueous and methanol extract treated groups having the most significant reductions in both variables (147.93±8.04, 152.91±10.85 mg/dL) when compared with the diabetic group (203.21±6.45, 355.16±11.25 mg/dL) respectively. AST and ALP activities reduced significantly (p < 0.05) in the aqueous extract treated group (33.18±4.48, 52.60±7.23 u/L) with no significant differences when values were compared to that of the normal control group (25.64±4.18, 44.13±5.80 u/L) respectively. Urea concentration decreased in all extract treatment groups except the group treated with the aqueous extract. Creatinine also decreased in the extract treated groups apart from the group treated with the aqueous and methanol extracts when both compared with the normal control group. ConclusionThe extracts from the leaves of C. equisetifolia have hypoglycemic and hypolipidemic effects, and can be further explored as a natural novel lead for drug development in the management of diabetes and dyslipidemia.

Elucidation of the non-volatile fingerprint in oven headspace vapor from bread roll baking by ultra-high resolution mass spectrometry

Untargeted research on vapor arising during the thermal processing of food has so far focused on volatile aroma compounds. In this study, we present an oven atmosphere sampling strategy to trap headspace aerosols along with semi- and non-volatile molecules liberated during the baking of wheat bread rolls. The collected vapor condensate was analyzed for its molecular fingerprinting using direct infusion ultra-high resolution mass spectrometry. We detected up to 4,700 molecular species in a vapor sample from bread rolls baked at 230 °C for 15 min. Beyond the global profiling of the underlying matrix, our method can follow complex reaction cascades during the baking process, such as the formation of advanced glycation end-products like maltosine through the interface of trapped vapor. Further, process parameters such as baking temperature and duration were used to model the dynamic liberation of molecules to the oven atmosphere by a response surface methodology approach.

Continuous vapor sampling of volatile organic compounds associated with explosives using capillary microextraction of volatiles (CMV) coupled to a portable GC–MS

The dynamic sampling and preconcentration device, capillary microextraction of volatiles (CMV), is coupled to a portable GC–MS for the rapid field detection of volatile organic compounds (VOCs) associated with explosives. The results of the portable GC–MS were compared to a benchtop GC–MS throughout this study. Sub-nanogram (ng) instrumental detection limits were achieved for each of the following analytes of interest (3-NT, 2,4-DNT, DPA, EC, DBP and 2-NDPA). Three different dynamic sampling methods were used with the CMV to sample and preconcentrate the volatiles prior to analysis. The headspace of a closed system was sampled over 10 min resulting in recoveries between 0.3 and 12%. Simulated open-air vapor sampling using a previously described vapor source resulted in an improvement of analyte recovery (ranging from 1.6 to 25%), for the same 10-minute sampling. A novel, continuous vapor delivery and sampling system was used, for the first time, to facilitate the delivery of sub-nanogram quantities of explosive analytes. The new continuous delivery system achieved significantly higher recoveries (3.0–89%) for all the analytes while requiring less sampling time (∼5 min) and sampling volumes than the other sampling techniques. The rapid sampling and preconcentration of sub-ng levels of VOCs in field scenarios was coupled to a ∼10-minute portable GC–MS method that compares favorably to the analytical figures of merit achieved by laboratory benchtop instruments and approximates the detection limits reported for canines.

Preservation of vapor samples on adsorbent alumina capillaries and implications for field sampling

Dynamic vapor microextraction (DVME) is a vapor preconcentration method that employs a capillary trap coated with an adsorbent, followed by solvent elution to recover the sample. DVME has been developed for applications in the laboratory, including highly precise vapor pressure measurements, and in the field. When vapor collection is conducted outside the laboratory, samples must almost always undergo some interval of storage representing the time between collection and analysis. This interval may be hours, days, or longer, depending on the situation. Regardless, in all situations there must be confidence that the integrity of the samples is maintained until processing and analysis. In this paper, we present results of two studies that tested the stability of a 50% weathered gasoline headspace sample on alumina PLOT (porous layer open tubular) capillaries stored at room temperature for periods from 24 h up to 20 wk. We used principal component analysis (PCA) to reduce the dimensionality of the chromatographic and mass spectral data and elucidate trends in stability with respect to the complex sample's range of hydrocarbon classes and molecular weights. Both analyses identified changes over storage periods of six weeks or more. The hydrocarbon class analysis, which used selected ion monitoring (SIM) data as input, proved more sensitive to changes over shorter storage periods. Sample integrity was preserved for at least 24 h, but losses, especially of high-volatility compounds, occurred by 168 h (7 d). Near total loss of sample occurred by 20 wk. These findings, which are specific to the sample, adsorbent, and storage conditions, will guide choices in experimental and instrumental design to ensure that data from future field studies is reliable.