Multivariate analysis of the volatile components in tobacco based on infrared‐assisted extraction coupled to headspace solid‐phase microextraction and gas chromatography‐mass spectrometry

A novel infrared‐assisted extraction coupled to headspace solid‐phase microextraction followed by gas chromatography with mass spectrometry method has been developed for the rapid determination of the volatile components in tobacco. The optimal extraction conditions for maximizing the extraction efficiency were as follows: 65 μm polydimethylsiloxane‐divinylbenzene fiber, extraction time of 20 min, infrared power of 175 W, and distance between the infrared lamp and the headspace vial of 2 cm. Under the optimum conditions, 50 components were found to exist in all ten tobacco samples from different geographical origins. Compared with conventional water‐bath heating and nonheating extraction methods, the extraction efficiency of infrared‐assisted extraction was greatly improved. Furthermore, multivariate analysis including principal component analysis, hierarchical cluster analysis, and similarity analysis were performed to evaluate the chemical information of these samples and divided them into three classifications, including rich, moderate, and fresh flavors. The above‐mentioned classification results were consistent with the sensory evaluation, which was pivotal and meaningful for tobacco discrimination. As a simple, fast, cost‐effective, and highly efficient method, the infrared‐assisted extraction coupled to headspace solid‐phase microextraction technique is powerful and promising for distinguishing the geographical origins of the tobacco samples coupled to suitable chemometrics.     

Inhibiting sorbent stripping by designing a sorbent‐packed porous probe for headspace solid‐phase microextraction

To prevent the stripping of coating sorbents in headspace solid‐phase microextraction, a porous extraction probe with packed sorbent was introduced by using a porous stainless steel needle tube and homemade sol–gel sorbents. The traditional stainless‐steel needle tube was punched by a laser to obtain two rows of holes, which supply a passageway for analyte vapor during extraction and desorption. The sorbent was prepared by a traditional sol–gel method with both poly(ethylene glycol) and hydroxy‐terminated silicone oil as coating ingredients. Eight polycyclic aromatic hydrocarbons and six benzene series compounds were used as illustrative semi‐volatile and volatile organic compounds in sequence to verify the extraction performance of this porous headspace solid‐phase microextraction probe. It was found that the analysis method combining a headspace solid‐phase microextraction probe and gas chromatography with mass spectrometry yielded determination coefficients of no less than 0.985 and relative standard deviations of 4.3–12.4%. The porous headspace solid‐phase microextraction probe showed no decrease of extraction ability after 200 uses. These results demonstrate that the packed extraction probe with porous structure can be used for headspace solid‐phase microextraction. This novel design may overcome both the stripping and breakage problems of the conventional coating fiber.     

Detection of volatile organic compounds in the headspace above mold fungi by GC‐soft X‐radiation–based APCI‐MS

Mold fungi on malting barley grains cause major economic loss in malting and brewery facilities. Possible proxies for their detection are volatile and semivolatile metabolites. Among those substances, characteristic marker compounds have to be identified for a confident detection of mold fungi in varying surroundings. The analytical determination is usually performed through passive sampling with solid phase microextraction, gas chromatographic separation, and detection by electron ionization mass spectrometry (EI‐MS), which often does not allow a confident determination due to the absence of molecular ions. An alternative is GC‐APCI‐MS, generally, allowing the determination of protonated molecular ions. Commercial atmospheric pressure chemical ionization (APCI) sources are based on corona discharges, which are often unspecific due to the occurrence of several side reactions and produce complex product ion spectra. To overcome this issue, an APCI source based on soft X‐radiation is used here. This source facilitates a more specific ionization by proton transfer reactions only. In the first part, the APCI source is characterized with representative volatile fungus metabolites. Depending on the proton affinity of the metabolites, the limits of detection are up to 2 orders of magnitude below those of EI‐MS. In the second part, the volatile metabolites of the mold fungus species Aspergillus, Alternaria, Fusarium, and Penicillium are investigated. In total, 86 compounds were found with GC‐EI/APCI‐MS. The metabolites identified belong to the substance classes of alcohols, aldehydes, ketones, carboxylic acids, esters, substituted aromatic compounds, terpenes, and sesquiterpenes. In addition to substances unspecific for the individual fungus species, characteristic patterns of metabolites, allowing their confident discrimination, were found for each of the 4 fungus species. Sixty‐seven of the 86 metabolites are detected by X‐ray–based APCI‐MS alone. The discrimination of the fungus species based on these metabolites alone was possible. Therefore, APCI‐MS in combination with collision induced dissociation alone could be used as a supervision method for the detection of mold fungi.     

Investigation of bacterial viability from incubated saliva by application of flow cytometry and hyphenated separation techniques

The aim of the study was determination of bacterial viability in saliva samples and finding a correlation between microbiological and volatile profiles of saliva depending on incubation time. Bacteria colonizing healthy oral cavities were also identified. Twelve healthy adults donated unstimulated saliva samples. Flow cytometry, optical density measurements and colony‐forming unit (CFU) counting method were employed for analyses of native and inoculated saliva after 0, 1, 2, 24, and 48 h of incubation. Volatile profiles were acquired using headspace‐solid phase microextraction‐gas chromatography/mass spectrometry (HS‐SPME‐GC/MS). Oral bacteria were the most viable within 2 h after collection of saliva. Extension of incubation time to 48 h caused considerable decrease in live bacteria counts and sharp increase in dead bacteria counts. The most prevalent strain was Sphingomonas paucimobilis (26.67%). The number of volatiles raised from 5 to 27 with incubation time and most of them were putrefaction products, such as methanethiol, indole and pyrrole. HS‐SPME‐GC/MS method is insufficient for volatile profiling of “fresh” saliva and should be directed rather to investigation of bacterial metabolites.     

Use of volatile organic solvents in headspace liquid‐phase microextraction by direct cooling of the organic drop using a simple cooling capsule

A low‐cost and simple cooling‐assisted headspace liquid‐phase microextraction device for the extraction and determination of 2,6,6‐trimethyl‐1,3 cyclohexadiene‐1‐carboxaldehyde (safranal) in Saffron samples, using volatile organic solvents, was fabricated and evaluated. The main part of the cooling‐assisted headspace liquid‐phase microextraction system was a cooling capsule, with a Teflon microcup to hold the extracting organic solvent, which is able to directly cool down the extraction phase while the sample matrix is simultaneously heated. Different experimental factors such as type of organic extraction solvent, sample temperature, extraction solvent temperature, and extraction time were optimized. The optimal conditions were obtained as: extraction solvent, methanol (10 μL); extraction temperature, 60°C; extraction solvent temperature, 0°C; and extraction time, 20 min. Good linearity of the calibration curve (R² = 0.995) was obtained in the concentration range of 0.01–50.0 μg/mL. The limit of detection was 0.001 μg/mL. The relative standard deviation for 1.0 μg/mL of safranal was 10.7% (n = 6). The proposed cooling‐assisted headspace liquid‐phase microextraction device was coupled (off‐line) to high‐performance liquid chromatography and used for the determination of safranal in Saffron samples. Reasonable agreement was observed between the results of the cooling‐assisted headspace liquid‐phase microextraction high‐performance liquid chromatography method and those obtained by a validated ultrasound‐assisted solvent extraction procedure.     

Rapid determination of the volatile components in tobacco by ultrasound‐microwave synergistic extraction coupled to headspace solid‐phase microextraction with gas chromatography‐mass spectrometry

An ultrasound‐microwave synergistic extraction coupled to headspace solid‐phase microextraction was first employed to determine the volatile components in tobacco samples. The method combined the advantages of ultrasound, microwave, and headspace solid‐phase microextraction. The extraction, separation, and enrichment were performed in a single step, which could greatly simplify the operation and reduce the whole pretreatment time. In the developed method, several experimental parameters, such as fiber type, ultrasound power, and irradiation time, were optimized to improve sampling efficiency. Under the optimal conditions, there were 37, 36, 34, and 36 components identified in tobacco from Guizhou, Hunan, Yunnan, and Zimbabwe, respectively, including esters, heterocycles, alkanes, ketones, terpenoids, acids, phenols, and alcohols. The compound types were roughly the same while the contents were varied from different origins due to the disparity of their growing conditions, such as soil, water, and climate. In addition, the ultrasound‐microwave synergistic extraction coupled to headspace solid‐phase microextraction method was compared with the microwave‐assisted extraction coupled to headspace solid‐phase microextraction and headspace solid‐phase microextraction methods. More types of volatile components were obtained by using the ultrasound‐microwave synergistic extraction coupled to headspace solid‐phase microextraction method, moreover, the contents were high. The results indicated that the ultrasound‐microwave synergistic extraction coupled to headspace solid‐phase microextraction technique was a simple, time‐saving and highly efficient approach, which was especially suitable for analysis of the volatile components in tobacco.     

Analysis of volatile organic compounds in pleural effusions by headspace solid‐phase microextraction coupled with cryotrap gas chromatography and mass spectrometry

Headspace solid‐phase microextraction coupled with cryotrap gas chromatography and mass spectrometry was applied to the analysis of volatile organic compounds in pleural effusions. The highly volatile organic compounds were separated successfully with high sensitivity by the employment of a cryotrap device, with the construction of a cold column head by freezing a segment of metal capillary with liquid nitrogen. A total of 76 volatile organic compounds were identified in 50 pleural effusion samples (20 malignant effusions and 30 benign effusions). Among them, 34 more volatile organic compounds were detected with the retention time less than 8 min, by comparing with the normal headspace solid‐phase microextraction coupled with gas chromatography and mass spectrometry method. Furthermore, 24 volatile organic compounds with high occurrence frequency in pleural effusion samples, 18 of which with the retention time less than 8 min, were selected for the comparative analysis. The results of average peak area comparison and box‐plot analysis showed that except for cyclohexanone, 2‐ethyl‐1‐hexanol, and tetramethylbenzene, which have been reported as potential cancer biomarkers, cyclohexanol, dichloromethane, ethyl acetate, n‐heptane, ethylbenzene, and xylene also had differential expression between malignant and benign effusions. Therefore, the proposed approach was valuable for the comprehensive characterization of volatile organic compounds in pleural effusions.     

Sensitive determination of polychlorinated biphenyls in environmental water samples by headspace solid‐phase microextraction with bamboo charcoal@iron oxide black fibers prior to gas chromatography with tandem mass spectrometry

We have investigated the feasibility of bamboo charcoal@iron oxide black for the headspace solid‐phase microextraction of polychlorinated biphenyls in environmental water samples. Bamboo charcoal@iron oxide black was prepared and used as a solid‐phase microextraction coating material, and gas chromatography with tandem mass spectrometry was used for detection. Several important factors affecting the extraction efficiency were systematically investigated and optimized. Under the optimum conditions, the experimental data exhibited wide linear range over the range 0.2–1000 ng/L and low limits of detection in the range of 4.7–22.2 pg/L. The novel coating was successfully used for the enrichment and determination of polychlorinated biphenyls in real environmental water samples. All these results indicated that bamboo charcoal@iron oxide black‐based headspace solid‐phase microextraction coupled to gas chromatography with tandem mass spectrometry was an excellent alternative for the sensitive analysis of polychlorinated biphenyls at ultratrace levels in the environment.     

Metabolomics strategy for the mapping of volatile exometabolome from Saccharomyces spp. widely used in the food industry based on comprehensive two‐dimensional gas chromatography

Saccharomyces spp. are widely used in the food and beverages industries. Their cellular excreted metabolites are important for general quality of products and can contribute to product differentiation. This exploratory study presents a metabolomics strategy for the comprehensive mapping of cellular metabolites of two yeast species, Saccharomyces cerevisiae and S. pastorianus (both collected in an industrial context) through a multidimensional chromatography platform. Solid‐phase microextraction was used as a sample preparation method. The yeast viability, a specific technological quality parameter, was also assessed. This untargeted analysis allowed the putative identification of 525 analytes, distributed over 14 chemical families, the origin of which may be explained through the pathways network associated with yeasts metabolism. The expression of the different metabolic pathways was similar for both species, event that seems to be yeast genus dependent. Nevertheless, these species showed different growth rates, which led to statistically different metabolites content. This was the first in‐depth approach that characterizes the headspace content of S. cerevisiae and S. pastorianus species cultures. The combination of a sample preparation method capable of providing released volatile metabolites directly from yeast culture headspace with comprehensive two‐dimensional gas chromatography was successful in uncovering a specific metabolomic pattern for each species.     

Graphene‐doped electrochemical copolymer coating of 2,2‐bithiophene and 3‐methylthiophene for the highly effective solid‐phase microextraction of volatile benzene homologues

We report the electrochemical fabrication of a poly(2,2‐bithiophene‐co‐3‐methylthiophene)‐graphene composite coating and its application in the headspace solid‐phase microextraction and gas chromatography determination of benzenes (i.e., bromobenzene, 4‐bromotoluene, 2‐nitrotoluene, 3‐nitrotoluene and 1,2,4‐trichlorobenzene). The coating was uniform and showed cauliflower‐like microstructure. It had high thermal stability (up to 375°C) and could be used for at least 180 times of solid‐phase microextraction without a decrease in extraction performance. Furthermore, it presented high extraction capacity for the benzenes due to the hydrophobic effect and π–π interaction between the analytes and the coating. Under optimized extraction conditions, good linearity (correlation coefficients higher than 0.9946), wide linear range (0.01–50 μg/L), and low limits of detection (5.25–12.5 ng/L) were achieved for these analytes. The relative standard deviation was lower than 5.7% for five successive measurements with one fiber, and the relative standard deviation for fiber‐to‐fiber was 4.9–6.8% (n = 5). The solid‐phase microextraction and gas chromatography method was successfully applied for the determination of three real samples, and the recoveries for standards added were 89.6–106% for nail polish, 85.8–110% for hair dye, and 90–106.2% for correction fluid, respectively.     

QSRR Study of GC Retention Indices of Volatile Compounds Emitted from Mosla chinensis Maxim by Multiple Linear Regression

The volatile compounds emitted from Mosla chinensis Maxim were analyzed by headspace solid‐phase microextraction (HS‐SPME) and headspace liquid‐phase microextraction (HS‐LPME) combined with gas chromatography‐mass spectrometry (GC‐MS). The main volatiles from Mosla chinensis Maxim were studied in this paper. It can be seen that 61 compounds were separated and identified. Forty‐nine volatile compounds were identified by SPME method, mainly including myrcene, α‐terpinene, p‐cymene, (E)‐ocimene, thymol, thymol acetate and (E)‐β‐farnesene. Forty‐five major volatile compounds were identified by LPME method, including α‐thujene, α‐pinene, camphene, butanoic acid, 2‐methylpropyl ester, myrcene, butanoic acid, butyl ester, α‐terpinene, p‐cymene, (E)‐ocimene, butane, 1,1‐dibutoxy‐, thymol, thymol acetate and (E)‐β‐farnesene. After analyzing the volatile compounds, multiple linear regression (MLR) method was used for building the regression model. Then the quantitative structure‐retention relationship (QSRR) model was validated by predictive‐ability test. The prediction results were in good agreement with the experimental values. The results demonstrated that headspace SPME‐GC‐MS and LPME‐GC‐MS are the simple, rapid and easy sample enrichment technique suitable for analysis of volatile compounds. This investigation provided an effective method for predicting the retention indices of new compounds even in the absence of the standard candidates.     

Automated headspace solid‐phase microextraction and on‐fiber derivatization for the determination of clenbuterol in meat products by gas chromatography coupled to mass spectrometry

A method was developed for the determination of clenbuterol in meat using stable‐isotope‐dilution gas chromatography with mass spectrometry coupled with solid‐phase microextraction and on‐fiber derivatization. The samples were first homogenized with hydrochloric acid followed by protein deposition. After headspace solid‐phase microextraction and on‐fiber derivatization, the content of clenbuterol was measured with the aid of stable‐isotope dilution. The condition of solid‐phase microextraction was optimized by central composite design. The relative standard deviations, limit of detection, and recoveries for clenbuterol were 4.2–9.2%, 0.48 μg/kg, and 96–104%, respectively. The proposed method was satisfactory for analysis of real samples as compared with the Chinese standard method.     

A novel sorbent based on carbon nanotube/amino‐functionalized sol–gel for the headspace solid‐phase microextraction of α‐bisabolol from medicinal plant samples using experimental design

A novel sol–gel coating on a stainless‐steel fiber was developed for the first time for the headspace solid‐phase microextraction and determination of α‐bisabolol with gas chromatography and flame ionization detection. The parameters influencing the efficiency of solid‐phase microextraction process, such as extraction time and temperature, pH, and ionic strength, were optimized by the experimental design method. Under optimized conditions, the linear range was between 0.0027 and 100 μg/mL. The relative standard deviations determined at 0.01 and 1.0 μg/mL concentration levels (n = 3), respectively, were as follows: intraday relative standard deviations 3.4 and 3.3%; interday relative standard deviations 5.0 and 4.3%; and fiber‐to‐fiber relative standard deviations 6.0 and 3.5%. The relative recovery values were 90.3 and 101.4% at 0.01 and 1.0 μg/mL spiking levels, respectively. The proposed method was successfully applied to various real samples containing α‐bisabolol.     

Modified headspace solid‐phase microextraction for the determination of quantitative relationships between components of mixtures consisting of alcohols,esters, and ethers — impact of the vapor pressure difference of the compounds

The quantitative relationship between analytes established by the headspace solid‐phase microextraction procedure for multicomponent mixtures depends not only on the character and strength of interactions of individual components with solid‐phase microextraction fiber but also on their vapor pressure in the applied headspace solid‐phase microextraction system. This study proves that vapor pressure is of minor importance when the sample is dissolved/suspended in a low‐volatility liquid of the same physicochemical character as that of the used solid phase microextraction fiber coating. It is demonstrated for mixtures of alcohols, esters, ethers and their selected representatives by applying a headspace solid‐phase microextraction system composed of Carbowax fiber and sample solutions in polyethyleneglycol. The observed differences in quantitative relations between components of the examined mixtures established by their direct analysis and by modified headspace solid‐phase microextraction are insignificant (F _exp < F _crit). It is explained by a significant diminution in vapor pressure difference between individual components of the examined mixture in the applied headspace solid phase microextraction system due to low components concentration in polyethyleneglycol suspensions (Raoult's law) and due to strong specific interactions of analyte molecules with polyethyleneglycol molecules.     

Solid‐phase microextraction Arrow for the volatile organic compounds in soy sauce

A novel solid‐phase microextraction Arrow was used to separate volatile organic compounds from soy sauce, and the results were verified by using gas chromatography with mass spectrometry. Solid‐phase microextraction Arrow was optimized in terms of three extraction conditions: type of fiber used (polydimethylsiloxane, polyacrylate, carbon wide range/polydimethylsiloxane, and divinylbenzene/polydimethylsiloxane), extraction temperature (40, 50, and 60°C), and extraction time (10, 30, and 60 min). The optimal solid‐phase microextraction Arrow conditions were as follows: type of fiber = polyacrylate, extraction time = 60 min, and extraction temperature = 50°C. Under the optimized conditions, the solid‐phase microextraction Arrow was compared with conventional solid‐phase microextraction to determine extraction yields. The solid‐phase microextraction Arrow yielded 6–42‐fold higher levels than in solid‐phase microextraction for all 21 volatile organic compounds detected in soy sauce due to the larger sorption phase volume. The findings of this study can provide practical guidelines for solid‐phase microextraction Arrow applications in food matrixes by providing analytical methods for volatile organic compounds.     

Exploiting the versatility of vacuum‐assisted headspace solid‐phase microextraction in combination with the selectivity of ionic liquid‐based GC stationary phases to discriminate Boswellia spp. resins through their volatile and semivolatile fractions

The frankincense resins, secreted from Boswellia species, are an uncommon example of a natural raw material where every class of terpenoids is present in similar proportions. Diterpenoids (serratol, incensole, and incensole acetate) are used to discriminate samples from different species and origins. Headspace solid‐phase microextraction has been used for frankincense analysis, although it requires long sampling time for medium‐ to low‐volatility markers; headspace solid‐phase microextraction under vacuum can overcome this limit. Gas chromatography is used for analysis but the separation of incensole and serratol needs polar stationary phases. In this study, we develop a method to discriminate frankincenses based on vacuum‐assisted headspace solid‐phase microextraction combined with fast gas chromatography‐mass spectrometry with ionic liquid–based stationary phases. The optimized conditions for solid samples were: air evacuation below 0°C, 15 min of incubation time, and 15 min of extraction time. Losses of volatiles due to vial air‐evacuation in the presence of the sample were minimized by sample amount above 100 mg and low sample temperature. Fast gas chromatography provides the baseline separation of all markers in 20 min. By applying vacuum sampling and fast gas chromatography, the total analysis was reduced to 50 min compared to 120 min (60 min sampling plus 60 min analysis) as previously reported. The method was successfully applied to commercial frankincense samples.     

Rapid and accurate determination of trace volatile sulfur compounds in human halitosis by an adaptable active sampling system coupling with gas chromatography

Halitosis with the main components of trace volatile sulfur compounds widely affects the quality of life. In this study, an adaptable active sampling system with two sample‐collection modes of direct injection and solid‐phase microextraction was developed for the rapid and precise determination of trace volatile sulfur compounds in human halitosis coupled with gas chromatography–flame photometric detection. The active sampling system was well designed and produced for efficiently sampling and precisely determining trace volatile targets in halitosis under the optimized sampling and detection conditions. The analytical method established was successfully applied for the determination of trace targets in halitosis. The limits of detection of H₂S, CH₃SH, and CH₃SCH₃ by direct injection were 0.0140–23.0 μg/L with good recoveries ranging from 82.2 to 118% and satisfactory relative standard deviations of 0.4–9.5% (n = 3), respectively. The limit of detections of CH₃SH and CH₃SCH₃ by solid‐phase microextraction were 2.03 and 0.186 × 10^?3 μg/L with good recoveries ranging from 98.3 to 108% and relative standard deviations of 5.9–9.0% (n = 3). Trace volatile targets in positive real samples could be actually found and quantified by combination of direct injection and solid‐phase microextraction. This method was reliable and efficient for the determination of trace volatile sulfur compounds in halitosis.     

Geographical discrimination of Chinese winter wheat using volatile compound analysis by HS‐SPME/GC‐MS coupled with multivariate statistical analysis

This study aimed to develop a potential analytical method to discriminate the Chinese winter wheat according to geographical origin and cultivars. A total of 90 wheat samples of 10 different wheat cultivars among three regions were examined by headspace solid phase microextraction coupled with gas chromatography‐mass spectrometry (GC‐MS). The peak areas of 32 main volatile compounds were selected and subjected to statistical analysis, which revealed significant differences among different regions and cultivars. Multivariate analysis of variance showed a significant influence of regions, wheat genotypes, and their interaction on the volatile composition of wheat. Principal component analysis of the aromatic profile showed better visualization for wheat geographical origins. Finally, a classification model based on the linear discriminant analysis was successfully constructed for the discrimination of regions and cultivars with the correct classification percentages of 90 and 100%, respectively.     

Solid phase microextraction as a tool for trace element speciation

Applications of solid phase microextraction (SPME) for trace element speciation are reviewed. Because of the relative novelty of the technique in the inorganic analytical field, the first part of this review provides a short overview of the principles of SPME operation; the second part describes typical SPME applications to elemental speciation. Volatile organometallic compounds can be collected by SPME from the sample headspace or liquid phase, directly or after derivatization. The usual separation method for the collected volatile species is gas chromatography. Non-volatile analyte species can be collected from the sample liquid phase and separated by liquid chromatography or capillary electrophoresis. Currently, most SPME applications in the inorganic field comprise analyte ethylation and headspace extraction followed by gas chromatographic separation of tin, lead and mercury species. The use of SPME for the study of equilibria in complex systems is also discussed and future roles of solid phase microextraction in the inorganic analytical field are raised.     

Matrix solid‐phase dispersion with chitosan‐zinc oxide nanoparticles combined with flotation‐assisted dispersive liquid–liquid microextraction for the determination of 13 n‐alkanes in soil samples

In this study, chitosan‐zinc oxide nanoparticles were used as a sorbent of miniaturized matrix solid‐phase dispersion combined with flotation‐assisted dispersive liquid–liquid microextraction for the simultaneous determination of 13 n‐alkanes such as C₈H₁₈ and C₂₀H₄₂ in soil samples. The solid samples were directly blended with the chitosan nanoparticles in the solid‐phase dispersion method. The eluent of solid‐phase dispersion was applied as the dispersive solvent for the following flotation‐assisted dispersive liquid–liquid microextraction for further purification and enrichment of the target compounds prior to gas chromatography with flame ionization detection. Under the optimum conditions, good linearity with correlation coefficients in the range 0.9991 < r² < 0.9995 and low detection limits between 0.08 to 2.5 ng/g were achieved. The presented procedure combined the advantages of chitosan‐zinc oxide nanoparticles, solid‐phase dispersion and flotation‐assisted dispersive liquid–liquid microextraction, and could be applied for the determination of n‐alkanes in complicated soil samples with acceptable recoveries.