Static Headspace Method Research Articles

Cosolvent effects of alcohols on the Henry's law constant and aqueous solubility of tetrachloroethylene (PCE)

The effects of selected cosolvents ethyl alcohol (EtOH), isopropyl alcohol (IPA), and tertbutyl alcohol (TBA) on the Henry's law constant ( H) of tetrachloroethylene (PCE) in aqueous solutions were investigated using the static headspace method. Alcohols in solution at a concentration around 20% and above acted as cosolvents increasing the aqueous solubility of PCE, which resulted in lower H values for PCE as compared to the value of H in deionized water. TBA, the most hydrophobic of the three alcohols, exhibited the strongest cosolvent effects, while EtOH had the weakest effects. A ln–linear relationship was observed between H and the volumetric fraction of alcohol added. Investigation of the solubilization of PCE in alcohol solutions confirmed the cosolvent trend observed for the three alcohols. A ln–ln relationship was observed between H and the enhanced solubility of PCE at a particular alcohol concentration. It was also observed that the value of H is a function of the enhanced solubility regardless of the type of cosolvent used. The results from this research further define the behavior of PCE in alcohol flooding solutions used in the remediation of PCE contaminated media.

High levels of monoaromatic compounds limit the use of solid-phase microextraction of methyl tert-butyl ether and tert-butyl alcohol.

Recently, two papers reported the use of solid-phase microextraction (SPME) with poly(dimethylsiloxane)(PDMS)/Carboxen fibers to determine trace levels of methyl tert-butyl ether (MTBE) and tert-butyl alcohol (tBA) in water. Attempts were made to apply this technique to the analysis of water samples containing high levels of benzene, toluene, ethylbenzene, xylenes, and trimethylbenzenes (BTEXsTMBs) as would be expected at leaking underground storage tank sites. It was found that when the sample contained total aromatic compounds above 1 ppm, the response of the internal standards, deuterated MTBE and tBA, dropped by more than 65%. As this decrease in internal standard peak area was unacceptable, a static headspace method was used instead. This headspace method was used successfully to analyze groundwater from 670 monitoring wells at 74 service stations located in the northeast United States. In these monitoring wells, 30% of the samples contained total BTEXsTMBs above 1 ppm. If the SPME method was used to analyze these samples, dilution of more than 200 samples would be required to minimize the adverse matrix effect that high aromatic content had on the internal standard peak area.

Headspace Evaluation of Methanethiol and Dimethyl Trisulfide in Aqueous Solutions of Soy‐protein Isolates

ABSTRACT Volatile compounds from 2 samples of aqueous soy‐protein isolates (SPI) (7%) were analyzed using both static and dynamic headspace methods. Based on dynamic headspace analyses, the most powerful odorants were (1) dimethyl trisulfide, (2) methanethiol, (3) hexanal, (4) an unidentified charred, sweaty feet‐like odor, (5) 2‐pentyl furan, (6) 2,3‐butadione, and (7) an unknown burnt‐like odor. The most powerful odorants by static headspace analyses were (1) dimethyl trisulfide, (2) hexanal, (3) methanethiol, and (4) 2‐pentyl furan. Using deuterium labeled DMTS as an internal standard, DMTS was quantified at 60.1 and 45.5 ppb in the SPIs. This corresponds to odor values of 6014 and 4554, respectively. Using a cool, on‐column technique, direct injection of concentrated‐headspace volatiles and solvent‐recovered volatiles with an internal standard of d6‐DMTS detected both methanethiol and DMTS at similar levels as with the traditional injection methods.

Measurement of aqueous Henry's law constants for oxygenates and aromatics found in gasolines by the static headspace method

A simple equilibrium vessel made from a large stopcock was used in conjunction with the static headspace method to measure the aqueous Henry's law constants for methyl tert-butyl ether (MTBE) and other potential oxygenates as well as certain of the aromatics found in gasoline. The present method involves using only one aqueous solution whose concentration is not necessarily known. The only quantity that must be known is the phase ratio. Plotting a series of peak areas of the analyte in the headspace after each equilibrium change against the initial peak area of the analyte found in the headspace leads to a linear relationship whose slope is dependent on the analyte's unitless Henry's law constant and the phase ratio. This new method is found to yield unitless aqueous Henry's law constants in the range from 0.02 to 0.2, which are especially applicable to the oxygenates and aromatics found in gasolines.

Interaction of Fragrance Materials With 2‐Hydroxypropyl‐β‐Cyclodextrin by Static and Dynamic Head‐space Methods

The stability constants for the inclusion of fragrance materials with 2-hydroxypropyl-beta-cyclodextrin (2HP-beta-C yD) in aqueous solution have been determined by the static head-space method. The 1:1 stability constants obtained by this method were in reasonable agreement with the corresponding values in the literature. In addition, the release profiles of fragrance materials from 2HP-beta-CyD aqueous solution were investigated using the dynamic head-space method. It was found that the suppression of the fragrance materials release was dependent on their stability constants.

Comparison of Gas-Sampled and SPME-Sampled Static Headspace for the Determination of Volatile Flavor Components

Traditional static headspace and headspace solid-phase microextraction (SPME) techniques were compared for their effectiveness in the extraction of volatile flavor compounds from the headspace of various juice samples. Each method was used to evaluate the responses of certain analytes from real samples and calibration standards in order to provide sensitivity comparisons between the two techniques. Experimental results showed traditional static headspace lacked the sensitivity needed to evaluate certain flavor volatiles, such as α-terpinene and linalool, and that further concentration of the headspace was necessary. Dramatic improvements in the extraction abilities of the SPME fibers over the traditional static headspace method were noted. Different SPME fibers were investigated to determine the selectivities of the various fibers to the different flavor compounds present in the juice samples. Of the various fibers investigated, the PDMS/DVB fiber proved to be the most useful for these analyses. Aging studies of juice samples were also performed which verified that degradation could be observed and quantified.

Solid-Phase Microextraction for the Analysis of Some Alcohols and Esters in Beer: Comparison with Static Headspace Method

Headspace solid-phase microextraction (SPME) has been used for the determination of 12 alcohols and esters in beer. SPME analysis parameters using polyacrylate fiber have been defined and compared with the static headspace (SHS) method used as a reference. Limits of detection, linearity, and repeatability of both methods have been determined using standard solutions. Limits of detection of SPME were generally lower than of the SHS method, and addition of salt enhanced SPME adsorption. Both methods were characterized by high repeatability and good linearity. Results of beer analyses obtained by using these two methods were highly correlated, which indicates the possibility of SPME application as an inexpensive alternative to automated SHS in the analysis of higher alcohols and esters in beer. Keywords: SPME; static headspace; beer alcohols; esters

The effect of various soil matrices on the analysis of VOCs by automated static headspace/gas chromatography

This study addresses the analysis of volatile organic compounds (VOCs) from various soil matrices using an automated, static headspace method. In general, the static (equilibrium) headspace method is able to provide more precise and rapid determinations of VOCs from soil matrices than the commonly used purge‐and‐trap methods. However, this study, as well as those of others, has shown that the experimental conditions of the automated static headspace method (EPA Method 5021) Is not sufficient to remove all of the inherent matrix effects of the various soil types. In general, VOC recoveries are found to decrease in the following order: water, pure sand, sandy soil, clay, then top soil. To reduce matrix effects, a recently reported full evaporation technique (FET), which uses little or no aquéous phase and higher equilibration temperatures, was found to give the most reproducible analyte recoveries, especially from soils exhibiting severe matrix effects due to high carbon content.

Relationship between Static Headspace and Vapor Concentration Above Dilute Liquid Solution Methods In the Measurement of Volatile Compounds

The generation of dilute vapor phase standards using the static headspace method can be challenging, requiring the construction of specialized chambers or use special methods for adding minute amounts of the compound of interest. The vapor concentration above a dilute water solution can be effective and accurate and has been used to create standards to measure the concentration for a wide range of volatile and semivolatile organic compounds. Such systems are highly temperature-sensitive, however. The goal of this work is to mathematically describe the relationship between vapor concentration above a dilute water mixture for compounds important to postharvest physiology, such as ethanol, acetaldehyde, ethyl acetate, and hexanol. The experiments were carried out in the range of 0 to 40°C and concentration of 0 to 1000 ppm for each compound. Three replications were used for each data point. The concentration was measured after thermal and chemical equilibration by gas chromatography containing a HAYESSEP-N column, by injecting 1 cc of the vapor headspace, using a 8-cm-long needle Hamilton syringe. Relationships for each of the compounds noted were successfully described employing multiple-order equations. For example, the relationship for ethanol vapor concentration was: Y = 12.12356 + 0.9461594*X + 0.5761110e-01*X2 + 0.6565694E-03*X3 + 0.23499598E-04*X4 (R2 = 1.000), with X being the temperature in °C. The relationships described for those compounds provides an useful tool that allows us to dilute liquid standards across a range of temperatures.

Development of a whole headspace injection method for the determination of volatile organic compounds in water

A whole headspace injection method was devised and evaluated. In the conventional static headspace method, only a part of headspace gas is introduced into the separation column. The amount of volatile organic compounds in a whole headspace calculated using Henry's constants was shown to be enough for the measurement using gas chromatography-mass spectrometry. Therefore, we have designed a device which allows the whole headspace gas to be sampled from a vial, and the volatile organic compounds in it are brought into a micro-trap, and then into a gas chromatographic-mass spectrometry system. Using this method, sensitive headspace analysis has been achieved.

Novel techniques for the off-line analysis of liquid process streams by mass spectrometry

Two novel methods for the analysis of simulated liquid process streams are described; static headspace analysis–MS and total vaporization–MS. A variety of experimental parameters have been studied and optimized for the detection of acetone and methyl iodide in water and acetic acid matrices, respectively. The detection limits (3σ) for the headspace technique at a sample temperature of 71 °C are 0.5 and 2 µg ml–1 and for the total vaporization technique are 19 and 1 µg ml–1, respectively, for acetone and methyl iodide. The RSD for concentrations of 10 µg ml–1 of the above analytes are generally less than 6%[n= 6 (static headspace method), n= 10 (total vaporization method)].

Use of sequential purging with the static headspace method to quantify gasoline contamination

The static headspace method used with portable gas chromatographs has become an important means of field screening environmental samples for gasoline contamination. A major limitation in using this method is the simultaneous detection (coelution) of other volatile gasoline constituents with those of interest. This is particularly problematic in the quantitation of methyl- t-butyl ether (MTBE), benzene and toluene. A sequential purging technique was used with static headspace analysis to remove coeluting compounds and to improve the accuracy in the quantitation of MTBE and aromatic constituents. Aqueous constituent concentrations determined using sequential purging were generally within 20% of those determined from laboratory purge and trap/gas chromatography (EPA method SW 846-602) analyses. Without sequential purging, constituent concentrations determined using the static headspace method were found to be 2 to over 10 times that of laboratory analyses. Further, in very contaminated samples, sequential purging permitted quantitation of constituents which were not resolvable in the initial headspace analysis due to coelution.

Studies about the desorption of volatile halocarbons from activated carbon by application of static headspace gas chromatography.

The analysis of volatile halocarbons (VHCs) in air or ground air is often performed after their adsorption and enrichment on activated carbon. The current procedure for their subsequent determination is based on their extraction from the activated carbon with a volatile organic solvent such as n-pentane, followed by gaschromatographic (GC) analysis. In order to avoid extraction steps, the static headspace method in combination with GC analysis using diphenylmethane as a desorption agent has been applied. Satisfactory desorption rates for the chloromethanes, for 1,1,1-trichloroethane, trichloroethene and for tetrachloroethene have been obtained after a sample equilibration of 45 min at 120 degrees C in the presence of diphenylmethane. The results have shown a higher recovering rate especially of the unsaturated VHCs compared to the extraction with n-pentane, whereby a potential loss of analytes by the latter procedure has been avoided.

Microwave‐assisted process (MAP™): Application to the headspace analysis of VOCs in water

AbstractA method combining the techniques of microwave‐assisted process (MAP) and gas chromatography (GC) has been developed for the determination of volatile organic compounds in water. For comparison purposes, MAP and conventional gas‐phase extractions using static headspace methods were performed on laboratory‐spiked water samples. The analytes used as models in this preliminary investigation were benzene, toluene, ethylbenzene, chlorobenzene, o‐, m‐, and p‐xylenes, and 1,2‐, 1,3‐, and 1,4‐dichlorobenzenes. MAP uses microwaves to very rapidly heat the bulk of the matrix and achieve a selective vaporization of the analytes that are then transferred onto the gas chromatographic apparatus via identical sampling conditions. The method was tested over a 10–5000 ppb range and proved capable of yielding excellent linearity (R2 > 0.99999) and precision (RSD 1.4%). Compared to the conventional static headspace extraction method, the MAP extraction method offered enhanced sensitivity as evidenced by a response in signal greater by 35% for aliquots from the same aqueous solutions. This level of performance is achieved within one minute of overall sample preparation time for the MAP method, whereas the conventional static headspace method used for comparison purposes required 30 minutes of equilibration time. Similar performance was observed with actual samples.

Using the static headspace method to determine Henry's law constants

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTUsing the static headspace method to determine Henry's law constantsGary A. Robbins, Suya. Wang, and James D. StuartCite this: Anal. Chem. 1993, 65, 21, 3113–3118Publication Date (Print):November 1, 1993Publication History Published online1 May 2002Published inissue 1 November 1993https://doi.org/10.1021/ac00069a026RIGHTS & PERMISSIONSArticle Views1528Altmetric-Citations169LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (670 KB) Get e-Alerts Get e-Alerts

Quantification of volatile solvents in blood by static headspace analysis

A static headspace method for determination of volatile solvents in blood was developed. The solvents determined were 1,1,1-trichloroethane, toluene, xylene ( o-, m- and p-), ethylbenzene, styrene, α-methylstyrene and 4-methylstyrene at concentrations ranging from 0.01 to 1 μg/ml. Internal standard calibration was used. Parameters affecting sensitivity and precision were determined and optimized.

Performance evaluation materials for the analysis of volatile organic contaminants in soil: A preliminary assessment

Abstract During an evaluation of field portable gas chromatographs (GC), site‐specific performance evaluation materials (PEM) were prepared and used as quality control samples. Clean soils from two contaminated sites were spiked with various volatile organic compounds. The PEM were shipped to the field via air carrier and analyzed by GC. The PEM samples were also shipped back to the laboratory and analyzed as double blind samples on a GC and a gas chromatograph / mass spectrometer (GC/MS). PEM samples which were held in the laboratory without being shipped were also analyzed. For GC analyses a static headspace method revealed highly variable recoveries for both shipped and unshipped PEM. An operationally‐defined headspace calibration was used to quantitate the amount of analyte remaining in the soil at various holding times and under various shipment scenarios. The influence of soil characteristics and volatile compound properties, and the effects of holding time and shipping on analyte stability in actua...

Qualitative analysis of a commercially available phenol—formaldehyde resin, by static and dynamic headspace analysis using a mass-selective detector

Static headspace and dynamic headspace procedures for volatile substances in solid matrices were investigated and compared by gas chromatography—mass spectrometry (GC—MS). For this purpose volatile components of a commercially available phenol—formaldehyde resin were analysed by GC—MS, first using the traditional static headspace method. A further study of the method aimed at obtaining a greater concentration, together with increased selectivity and a more reliable structural determination of the volatile substances, led to the use of the dynamic headspace (purge and trap) method. Following the latter method, after enrichment, the trap contents were recovered in solvents with different polarities in order to concentrate selectively the substances contained in the vapours of the resin itself. The solutions obtained were analysed by GC—MS.

Air-water partitioning coefficients of organics in dilute aqueous solutions

Henry's Law constants were measured for 45 chemicals spanning a wide range of chemical structures and volatilities. A static headspace method, Equilibrium Partitioning in Closed Systems (EPICS), was used to measure Henry's Law constant, and the batch air stripping method was used as a check. Measurements were conducted over a temperature range of 10–30°C, and the data were correlated with a temperature regression equation. An average precision of 10% was obtained for the EPICS runs, and the Henry's constants agreed well with the batch air stripping results and other reported values.

Possibilities of dynamic headspace analysis coupled with capillary GC for the investigation of solid samples

AbstractThe advantages of the dynamic headspace method for the analysis of solid samples, as compared with the static head space method, are discussed. Examples of dynamic headspace analyses are given to illustrate its possibilities.