Headspace Single-drop Microextraction Research Articles

Comparison of microwave-assisted headspace single-drop microextraction (MA-HS-SDME) with hydrodistillation for the determination of volatile compounds from Prangos uloptera

In this paper, a simple method based on gas chromatography–mass spectrometry (GC–MS) following microwave-assisted headspace single-drop microextraction (MA-HS-SDME) was developed for the determination of essential oil composition of Prangos uloptera. The MA-HS-SDME parameters including the nature of extracting solvent, microwave power, extraction time, sample weight and microdrop volume were optimized. The method was compared with traditional hydrodistillation (HD). Sixty components were extracted and identified. The main constituents, extracted by SDME and HD, respectively, included δ-3-carene (32.1% vs. 26.3%), α-pinene (16.8% vs. 15.4%) and camphene (4.1% vs. 2.7%). The relative standard deviation (RSD) values of less than 10% show that the proposed method has good repeatability and it is fast.

Rapid and sensitive determination of fluoride in toothpaste and water samples using headspace single drop microextraction-gas chromatography

A fast and reliable method was developed for the determination of fluoride in toothpaste based on the headspace single drop microextraction (HS-SDME) followed by gas chromatography/flame ionization detection (GC/FID). The method is based on the volatilization of fluoride using trimethylchlorosilane as the derivatization reagent to form trimethylfluorosilane at acidic pH. The trimethylfluorosilane formed is preconcentrated in a 0.8 μL drop of mesitylene suspended from the tip of a common GC microsyringe to the headspace of the sample. Parameters such as nature of the extraction solvent, extraction time, size of the microdrop, sample volume, stirring rate, derivatization reaction time and pH of the sample solution were studied and optimized. The developed protocol was found to yield a linear calibration curve in the concentration range of 5.0–39.0 mg L−1 with a limit of detection of 4.4 μg L−1 with a good enrichment factor of 58.8 for the analyte. The repeatability of the method was satisfactory (RSD ≤ 5.41%). The total analysis time including microextraction and gas chromatography analysis was less than 30 min. Because preconcentration and sampling are performed from the headspace of the sample, this method is suitable for the determination of trace amounts of fluoride in toothpastes and water samples.

Head-space single drop microextraction combined with gas chromatography with an electron capture detector for determination of iodine in infant formulas

Headspace single-drop microextraction (HS-SDME) coupled with gas chromatography with electron capture detection (GC-ECD) was used for quantification of total iodine in milk based samples of infant formula. In this procedure 3 μL of a mixture containing 1-octanol and 3-pentanone was exposed to the headspace of a 5 mL acidic (H2SO4, 2 mol L−1) aqueous solution containing 1.5 mol L−1 ZnSO4 for 30 minutes followed by addition of 1 mL of 1 mol L−1 H2O2 for in situ generation of iodine. Optimization of the microextraction system was carried out using the Taguchi experimental design method. The limit of detection was determined to be 250 ng L−1 with an enrichment factor of 150. The repeatability, expressed as a relative standard deviation, was 1.9% (n = 6). The linear calibration working range was between 0.75 and 2000 μg L−1 (r2 = 0.998). The method was successfully applied for determination of iodine in milk based samples of infant formula.

Headspace single-drop microextraction coupled with gas chromatography electron capture detection of butanone derivative for determination of iodine in milk powder and urine

AbstractA new detection method using headspace single-drop microextraction (HS-SDME) coupled to gas chromatography (GC) was established to determine the iodine in milk powder and urine. The derivative from the reaction between iodine and butanone in the acidic media was extracted into a micro-drop then determined by GC-ECD. With the optimisation of HS-SDME and derivatisation, the calibration curve showed good linearity within the range of 0.004–0.1 μg mL−1 (0.004–0.1 μg g−1) (R 2 = 0.9991), and the limits of detection for milk powder and urine were 0.0018 μg g−1 and 0.36 μg L−1, respectively. The mean recoveries of milk powder and urine were 90.0–107 % and 89.4–101 % with mean RSD of 1.7–3.4 % and 2.7–3.3 %, respectively. This detection method affords a number of advantages, such as being simple, rapid, and inexpensive, with low organic solvent consumption, and is remarkably free from interference effects, rendering it an efficient method for the determination of iodine in milk powder and urine samples.

Headspace Single-Drop Microextraction Gas Chromatography Mass Spectrometry for the Analysis of Volatile Compounds from Herba Asari

A rapid headspace single-drop microextraction gas chromatography mass spectrometry (SDME-GC-MS) for the analysis of the volatile compounds in Herba Asari was developed in this study. The extraction solvent, extraction temperature and time, sample amount, and particle size were optimized. A mixed solvent of n-tridecane and butyl acetate (1 : 1) was finally used for the extraction with sample amount of 0.750 g and 100-mesh particle size at 70°C for 15 min. Under the determined conditions, the pound samples of Herba Asari were directly applied for the analysis. The result showed that SDME-GC–MS method was a simple, effective, and inexpensive way to measure the volatile compounds in Herba Asari and could be used for the analysis of volatile compounds in Chinese medicine.

Microwave distillation followed by headspace single drop microextraction coupled to gas chromatography-mass spectrometry (GC–MS) for fast analysis of volatile components of Echinophora platyloba DC

To avoid the traditional and time consuming hydrodistillation, the analyses of volatile components in aerial parts of Echinophora platyloba DC was carried out by a simple microwave distillation followed by headspace single drop microextraction (MD–HS–SDME) coupled to gas chromatography–mass spectrometry (GC–MS). The headspace volatile compounds were collected after irradiation using a single drop of n-heptadecan. The extraction conditions were optimised using the relative peak areas as index. The chemical composition of the MD–HS–SDME extracts was confirmed according to their retention indexes and mass spectra. Fifty-three components were extracted and identified by using the MD–HS–SDME method. E-β-ocimene (53.81%), R-d-decalactone (12.75%), α-pinene (6.43%), n-heptanol (6.27%), β-phellanderne (2.70%) and linalool (1.89%) were the major constituents.

Fabrication and Characterization of LaF3/Titania Nanotube Array Electrode for Determination of Fluoride Using a Headspace Single-Drop Microextraction System

LaF3/titania nanotube array (TNAs) electrodes were fabricated by electrodeposition of LaF3 on synthesized TNAs. The electrode was characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), and energy dispersive X-ray spectrometer (EDS). The electrode exhibited excellent response to fluoride ion. The linear calibration range achieved four orders of magnitude of F- concentration (10−6–10−2 mg/ml) and the sensitivity of the electrode is higher than that of ordinary fluoride ion selective electrodes (mode PF-1). The limit of detection (LOD) was estimated to be 4.39 × 10−7 mg/ml (S/N = 3). The novel electrode was applied to the determination of trace fluoride ions in tap water and toothpaste. Finally, a headspace single-drop microextraction (SDME) system coupled with LaF3/TNAs electrode was successfully applied to determine fluoride in milk samples. The results are satisfactory with an average relative standard deviation (RSD %) of 0.51% and recovery from 96.3% to 107.3%.

Extraction of the Volatile and Semivolatile Compounds in Seeds of Cuminum cyminum L. Using Hydrodistillation Followed by Headspace-Ionic Liquid-Based Single-Drop Microextraction

Hydrodistillation (HD) coupled with headspace single-drop microextraction by using ionic liquid (IL) as the extraction solvent, followed by gas chromatography analysis technique, was successfully developed to determine the volatile and semivolatile compounds in seeds of Cuminum cyminum L. In the proposed method, a 1.5-μL microdrop of 1-octyl-3-methylimidazolium hexafluorophosphate, working as the extraction solvent was suspended in the headspace of a 50-mL round-bottom sample flask. After extracting for 30 min, both IL and target analytes were injected into the gas chromatographic system by thermal desorption for 5 s under 240 °C. Then, the IL was retracted back to the microsyringe. Thus, the capillary column should not be contaminated and a clean chromatogram was obtained. The parameters affecting extraction performance were investigated and optimized. The extraction efficiency of the proposed method was compared with that of HD, which is a standard extraction method. The contents of constituents in the extract obtained by the proposed method were close to those obtained by HD. It seems to be an environmentally friendly, time-saving, high efficiency and low solvent consumption technique and would be useful, especially for aromatic plants analysis.

A method for fast analysis of volatile components of Citrus aurantium L. leaves

To avoid the traditional and time consuming hydrodistillation, the analyses of volatile components in leaves of Citrus aurantium L. were carried out by a simple microwave distillation followed by headspace single drop microextraction (MD-HS-SDME) coupled to gas chromatography–mass spectrometry (GC–MS). The headspace volatile compounds were collected after irradiation using a single drop of n-heptadecan. The extraction conditions were optimized using the relative peak areas as index. The chemical composition of the MD-HS-SDME extracts was confirmed according to their retention indexes and mass spectra. Forty-one components were extracted and identified by using the MD-HS-SDME method. Limonene (62%), Linalool (7.47%), trans-β-Ocimene (3.47%), Caryophyllene (2.05%), α- Bisabolene (1.8%) and Myrcene (1.18%) were the major constituents.

Determination of musk fragrances in sewage sludge by pressurized liquid extraction coupled to automated ionic liquid‐based headspace single‐drop microextraction followed by GC‐MS/MS

A method for the quantitative determination of ten musk fragrances extensively used in personal care products from sewage sludge was developed by using a pressurized liquid extraction (PLE) followed by an automated ionic liquid-based headspace single-drop microextraction and gas chromatography-tandem mass spectrometry. The influence of main factors on the efficiency of PLE was studied. For all musks, the highest recovery values were achieved using 1 g of pretreated sewage sludge, H(2) O/methanol (1:1) as an extraction solvent, a temperature of 80°C, a pressure of 1500 psi, an extraction time of 5 min, 2 cycles, a 100% flush volume, a purge time of 120 s, and 1 g Florisil as in-cell clean-up extraction sorbent. The use and optimization of an in-cell clean-up sorbent was necessary to remove fatty interferents of the PLE extract that make the subsequent ionic liquid-based headspace single-drop microextraction difficult. Validation parameters, namely LODs and LOQs, ranged from 0.5-1.5 to 2.5-5 ng/g, respectively. Good levels of intra- and interday repeatabilities were obtained analyzing sewage sludge samples spiked at 10 ng/g (n = 3, RSDs < 10%). The method applicability was tested with sewage sludge from different wastewater treatment plants. The analysis revealed the presence of all the polycyclic musks studied at concentrations higher than the LOQs, ranging from 6 to 530 ng/g. However, the nitro musk concentrations were below the LOQs or, in the case of musk xylene, was not detected.

Headspace‐single drop microextraction with a commercial capillary electrophoresis instrument

Automated coupling of headspace-single drop microextraction (HS-SDME) and CE has been demonstrated using a commercial CE instrument. When a drop hanging at the inlet tip of a capillary for CE is used as the acceptor phase, HS-SDME becomes a simple but powerful sample pretreatment technique for CE before injection to facilitate sample cleanup and enrichment. By combining HS-SDME with an on-line sample preconcentration technique, large volume sample stacking using an electroosmotic flow pump, the sensitivity can be improved further. The overall enrichment factors for phenolic compounds were from 1900 to 3400. HS-SDME large volume sample stacking using an electroosmotic flow pump was successfully applied to a red wine sample to obtain an LOD of 4 nM (0.8 ppb) for 2,4,6-trichlorophenol which is a precursor for 2,4,6-trichloroanisole causing the foul odor in wine called cork taint.

Evaluation effect of microwave irradiation on the amount of volatile compounds, monoterpenes and sesquiterpenoids from Thymus kotschyanus Boiss with four methods

This article investigates the effect of microwaves on the amount of volatile compounds from Thymus kotschyanus Boiss with four methods, headspace single-drop microextraction, microwave-assisted headspace single-drop microextraction, microwave distillation extraction and hydrodistillation, for the analysis of essential oil. Solvent selection, solvent volume, microwave power, irradiation time and sample mass were optimised by simplex method.

Fully automated ionic liquid-based headspace single drop microextraction coupled to GC–MS/MS to determine musk fragrances in environmental water samples

A fully automated ionic liquid-based headspace single drop microextraction (IL-HS-SDME) procedure has been developed for the first time to preconcentrate trace amounts of ten musk fragrances extensively used in personal care products (six polycyclic musks, three nitro musks and one polycyclic musk degradation product) from wastewater samples prior to analysis by gas chromatography and ion trap tandem mass spectrometry (GC–IT-MS/MS). Due to the low volatility of the ILs, a large internal diameter liner (3.4mm i.d.) was used to improve the ILs evaporation. Furthermore, a piece of glass wool was introduced into the liner to avoid the entrance of the ILs in the GC column and a guard column was used to prevent analytical column damages. The main factors influencing the IL-HS-SDME were optimized. For all species, the highest enrichments factors were achieved using 1μL of 1-octyl-3-methylimidazolium hexafluorophosphate ([OMIM][PF6]) ionic liquid exposed in the headspace of 10mL water samples containing 300gL−1 of NaCl and stirred at 750rpm and 60°C for 45min. All compounds were determined by direct injection GC–IT-MS/MS with a chromatographic time of 19min. Method detection limits were found in the low ngmL−1 range between 0.010ngmL−1 and 0.030ngmL−1 depending on the target analytes. Also, under optimized conditions, the method gave good levels of intra-day and inter-day repeatabilities in wastewater samples with relative standard deviations varying between 3% and 6% and 5% and 11%, respectively (n=3, 1ngmL−1). The applicability of the method was tested with different wastewater samples from influent and effluent urban wastewater treatment plants (WWTPs) and one potable treatment plant (PTP). The analysis of influent urban wastewater revealed the presence of galaxolide and tonalide at concentrations of between 2.10ngmL−1 and 0.29ngmL−1 and 0.32ngmL−1 and <MQL (Method Quantification Limit), respectively; while the remaining polycyclic musks concentrations were below the method quantification limits and two of the nitro musks (musk xylene and musk moskene) were not detected. The analysis of effluent urban wastewater showed a decrease in galaxolide and tonalide concentrations while the other target analytes were not detected. In waters from PTP only galaxolide was found at a concentration higher than MQL.

Enzymatic single-drop microextraction for the assay of ethanol in alcohol-free cosmetics using microvolume fluorospectrometry detection

A green assay based on the development of an enzymatic reaction in drop format under headspace single-drop microextraction conditions is described for the first time. An aqueous drop containing the enzyme alcohol dehydrogenase and the cofactor β-Nicotinamide adenine dinucleotide has been used as fluorescence probe for determining ethanol in alcohol-free cosmetics by microvolume fluorospectrometry. Experimental parameters affecting the microextraction performance were carefully optimized. Under the conditions employed, the contribution of other alcohols was found to be negligible. After 10min of microextraction, a detection limit of 0.04μgg−1 ethanol, a repeatability, expressed as relative standard deviation, of 5.3% for a 0.05mM ethanol standard and a preconcentration factor of 391, were reached. Accuracy of the proposed methodology was evaluated by comparison of calibration slopes corresponding to external calibration with aqueous standards and standard addition calibration. The method was successfully applied to different alcohol-free cosmetics (external calibration was carried out in all cases). Additional advantages such as simplicity and high sample throughput can be highlighted. The greenness profile of proposed methodology was established using NEMI criteria (US National Environmental Methods Index).

Headspace single-drop microextraction of common pesticide contaminants in honey–method development and comparison with other extraction methods

In the present study the main factors that may influence the headspace single-drop microextraction (HS-SDME) of common pesticide contaminants (diazinon, lindane, chlorpyrifos ethyl, p,p′-DDE, and endosulfan) that may occur in honey were determined and an analytical protocol was further developed by the use of a multivariate optimization. The HS-SDME analytical method developed and two more analytical protocols for the determination of pesticides in honey: (i) by direct SDME (D-SDME), and (ii) by liquid–liquid extraction (LLE), were further validated for the determination of target analytes. The three methods were also applied in the same real honey samples and results were further discussed. By D-SDME, LODs ranged from 0.04 µg kg−1 for β-endosulfan to 2.40 µg kg−1 for diazinon and repeatability expressed as %RSD from 3 for lindane to 15 for diazinon and chlorpyrifos methyl; by HS-SDME, LODs ranged from 0.07 µg kg−1 for p,p′-DDE to 12.54 µg kg−1 for chlorpyrifos methyl and repeatability expressed as %RSD from 11 for chlorpyrifos methyl to 19 for p,p′-DDE; by LLE, LODs ranged from 0.09 µg kg−1 for β-endosulfan to 19.31 µg kg−1 for diazinon and repeatability expressed as %RSD from 6 for p,p′-DDE to 11 for lindane. For all target pesticides but p,p′-DDE that could not be recovered by D-SDME method tested. The proposed HS-SDME optimized in this study was shown to be the method of choice for the determination of diazinon in honey whereas the most favourable analytical characteristics from the comparative study performed were achieved by D-SDME.

An Improved Ionic Liquid-Based Headspace Single-Drop Microextraction-Liquid Chromatography Method for the Analysis of Camphor and Trans-Anethole in Compound Liquorice Tablets

A simple, accurate and sensitive ionic liquid-based headspace single-drop microextraction procedure followed by high-performance liquid chromatography was developed and validated for the determination of camphor and trans-anethole in compound liquorice tablets. The volume of the ionic liquid microdrop was increased to 12 µL by modifying the device of the suspended drop. The stability of the microdrop and the sensitivity of the method were improved. Under the optimum experimental conditions, the calculated calibration curves gave acceptable linearity for camphor and trans-anethole with correlation coefficients of 0.9990 and 0.9998, respectively. The repeatability of the proposed method, expressed as relative standard deviation, was below 4.5% (n = 5). The limits of detection for the two target analytes were found to be 9.77 and 1.95 × 10(-2) μg/mL, respectively. In this study, the separation, purification and enrichment were achieved in one step in an airtight system, which reduced the interferences caused by other complicated constituents, increased the signal-to-noise of the method and ensured the accuracy of the results because there was no loss of volatile components. It is expected to be widely applied for sample pretreatment of volatile components with high boiling points in samples with complicated matrices such as the extractions of plants or Chinese traditional drugs.

Speciation and Determination of Inorganic Mercury and Methylmercury by Headspace Single Drop Microextraction and Electrothermal Atomic Absorption Spectrometry in Water and Fish

AbstractIn this study, headspace single drop microextraction (HS‐SDME) method in combination with electrothermal atomic absorption spectrometry (ETAAS) method was developed and validated for the speciation and determination of inorganic mercury (iHg) and methylmercury (MeHg). MeHg and iHg species were reduced to volatile methylmercury hydride (CH3HgH) and elemental mercury, respectively, in the presence of NaBH4 and trapped onto a drop of acceptor phase in the tip of a microsyringe. Thiourea and ammonium pyrrolydinedithiocarbamate (APDC) were tested as the acceptor phase. The experimental parameters of the method such as microextraction time, temperature, NaBH4 concentration, acceptor phase concentration, and pH of the medium were investigated to obtain distinctive conditions for mercury species. Possible interference effects have also been investigated. In order to validation of the method, analytical figures of merits such as accuracy, precision, limit of detection (LOD), limit of quantitation (LOQ), and linear working range have been evaluated. Accuracy of the method has been verified by analyzing certified reference materials (BCR 453 Tuna fish) and spiked samples. The proposed method was applied for the speciation and determination of mercury species in water and fish samples. Mercury species (MeHg and iHg) have been determined in the real samples with a relative error less than 10%.

Fast screening of terpenes in fragrance-free cosmetics by fluorescence quenching on a fluorescein–bovine serum albumin probe confined in a drop

A headspace single drop microextraction procedure is proposed for terpene screening in fragrance-free cosmetics. The drop is composed by an aqueous solution of a fluorescence probe formed by bovine serum albumin and fluorescein. Extracted volatile terpenes produce a fluorescence quenching that can be monitored by microvolume-fluorospectrometry. This quenching is observed on the fluorescein fluorescence only when it is linked to bovine serum albumin. A mechanism of contact quenching is proposed. Variables related to the terpene microextraction procedure were carefully studied, namely drop composition and volume, microextraction time, sample volume and temperature, stirring rate and salt addition. The only sample treatment is the dilution of cosmetic with 40% (v/v) ethanol. Citronellol was selected as a representative terpene for calibration purposes. According to the European legislation, the probability-concentration graph of the screening system was established using 0.001% (w/w) as the cut-off level. Low limits of detection with simple instrumentation, absence of matrix effects and high sample throughput can be emphasized.

Determination of volatile residual solvents in pharmaceutical products by static and dynamic headspace liquid-phase microextraction combined with gas chromatography-flame ionization detection

Headspace single-drop microextraction (HS-SDME) and dynamic headspace liquid-phase microextraction (DHS-LPME) combined with GC-FID were used to determine thirteen residual solvents in pharmaceuticals. Different extraction conditions such as microdrop volume, ionic strength of the sample, extraction time, stirring rate, extraction temperature, solvent volume, sampling volume and number of extraction cycles were studied. n-Octanol was used as the extracting solvent for both methods. Under the optimal conditions, the limits of detection for the analytes obtained by DHS-LPME and HS-SDME ranged from 1.9 to 44 μg L−1 and 0.3 to 21 μg L−1, respectively. Enrichment factors ranged 9–212 and 15–379 for DHS-LPME and HS-SDME, respectively. The relative standard deviations (RSDs, n = 5) for both methods are lower than 9.1%. The applicability of the selected method (HS-SDME) in real sample analysis was investigated.

The effect of surfactant on headspace single drop microextraction for the determination of some volatile aroma compounds in citronella grass and lemongrass leaves by gas chromatography

A rapid method for the determination of some volatile aromatic compounds (VACs), including citronellal, citronellol, neral, geranial, geraniol and eugenol in citronella grass and lemongrass leaves, was developed using surfactant as a surface tension modifier while performing headspace single drop microextraction (HS-SDME) prior to analysis by GC-FID. Experimental parameters were optimized, including type of single drop solvent, extraction temperature and time, enrichment time, sample volume, and salt and surfactant concentration. In this study, the effect of surfactants (SDS, Triton-X and CTAB) on the HS-SDME of VACs was investigated in detail. It was found that a small amount of SDS could contribute to decreasing the surface tension of liquid phase, resulting in an improvement of the extraction efficiency. The proposed method gave higher concentration factors (2.39–24.6 fold) of these VACs in real samples, and good recovery (97.6–109%) and precision (7–15% RSD). The advantage of this procedure is then recognized as green chemistry because its simple and cheap method with reduced analysis time and toxicity. The sample preparation can easily be applied to routine analysis of these VACs in citronella grass and lemongrass leaf samples.