Stir Bar Sorptive Extraction Method Research Articles

Comparison of micro-scale simultaneous distillation–extraction and stir bar sorptive extraction for the determination of volatile organic constituents of grape juice

Traditional micro-scale simultaneous distillation–extraction (SDE) and stir bar sorptive extraction (SBSE) were compared for their effectiveness in the extraction of volatile organic compounds in a synthetic grape juice and a real grape juice (Huxelrebe, a variety of half Muscat ancestry) from an English vineyard. The novel immersion-mode SBSE method, using stir bars with PDMS sorbent, was optimised using the synthetic grape juice. Although mean percent relative recoveries and reproducibilities (%CV) of the SBSE method were inferior to SDE (28.4 and 8.5%, respectively, against 86.9 and 6.3%), the former method proved to be significantly more sensitive: 126 aroma compounds in Huxelrebe grape juice were identified using SBSE, against 98 using SDE. This allowed the identification of a number of volatile components that have not been reported previously in the juice or wine from the grapes of Muscat varieties.

Stir bar sorptive extraction for the determination of volatile compounds in oak-aged wines

Stir bar sorptive extraction (SBSE) followed by a thermal desorption-gas chromatography–mass spectrometry analysis has been optimized for the determination of 13 of the most important oak volatiles in wine samples, all in a single run. The stir bar sorptive extraction method was optimized in terms of temperature, time, pH and NaCl addition, and the best results were obtained after stirring the wine sample with the polydimethylsiloxane stir bar during 90 min at room temperature. The addition of sodium chloride did not enhance the volatile extraction. The method proposed showed good linearity over the concentration range tested, with correlation coefficients ranging from 0.92 to 0.99 for all the analytes. The reproducibility and repeatability of the method was estimated between 0.11 and 5.45%. The detection and quantification limits of all analytes were lower than their respective olfactory threshold values, and, most importantly, no artifacts have been observed during the analysis as described in most extractions using other current methodologies.

Stir bar sorptive extraction and high-performance liquid chromatography–fluorescence detection for the determination of polycyclic aromatic hydrocarbons in Mate teas

A simple procedure based on stir bar sorptive extraction (SBSE) and high-performance liquid chromatography–fluorescence detection (HPLC–FLD) is presented for the determination of 15 polycyclic aromatic hydrocarbons (PAHs) in herbal tea prepared with Mate leaves ( Ilex paraguariensis St. Hil.). The influence of methanol and salt addition to the samples, the extraction time, the desorption time and the number of desorption steps, as well as the matrix effect, were investigated. Once the SBSE method was optimised (10 mL of Mate tea, 2 h extraction at room temperature followed by 15 min desorption in 160 μL of an acetonitrile (ACN)–water mixture), analytical parameters such as repeatability (≤10.1%), linearity ( r 2 ≥ 0.996), limit of detection (LOD, 0.1–8.9 ng L −1), limit of quantitation (LOQ, 0.3–29.7 ng L −1) and absolute recovery (24.2–87.0%) were determined. For calibration purposes, a reference sample was firstly obtained by removing the analytes originally present in the lowest contaminated Mate tea studied (via SBSE procedure) and then spiked at 1–1200 ng L −1 range. The proposed methodology proved to be very convenient and effective, and was successfully applied to the analysis of 11 Mate tea samples commercialised in Brazil. The results of the commercial Mate tea samples found by the SBSE approach were compared with those obtained by liquid–liquid extraction (LLE), showing good agreement.

Stir bar sorptive extraction with in situ de-conjugation and thermal desorption gas chromatography-mass spectrometry for measurement of 4-nonylphenol glucuronide in human urine sample

4-Nonylphenol glucuronide (NP-G) in human urine samples was analyzed using stir bar sorptive extraction (SBSE) with in situ de-conjugation by β-glucuronidase and thermal desorption (TD)-gas chromatography-mass spectrometry (GC-MS). Distilled water (1 ml), 1.0 M ammonium acetate solution (100 μl) and β-glucuronidase (10,000 units ml −1, 10 μl) were added to human urine sample (1 ml), and extraction was commenced for 90 min at 37 °C while stirring at 250 rpm with a stir bar coated with a 500-μm-thick polydimethylsiloxane (PDMS) layer. Then, the stir bar was subjected to TD-GC-MS in the selected ion monitoring (SIM) mode. The calibration curve was made by SBSE method using 4-nonylphenol (NP) as the standard solution. The method showed good linearity and the correlation coefficients were 0.999 over the concentration range of 5–500 nM. Moreover, to optimize the conditions for SBSE with in situ de-conjugation and the recovery test, NP-G was synthesized by a biochemical technique in our laboratory. The limits of detection ( S/ N = 3) and quantitation ( S/ N > 10) for NP were 0.2 ng ml −1 (1.0 nM) and 1.1 ng ml −1 (5.0 nM), respectively. The average recoveries in the human urine samples ( n = 6) spiked with NP-G at levels of 20 and 100 nM were 104.1 (R.S.D. 7.1%) and 100.6% (R.S.D. 9.2%), respectively, with correction using the added internal standard, 4-(1-methyl) octylphenol-d 5. The method enabled the precise determination of the standard and was applicable to the detection of trace amounts of NP-G in human urine samples.

Comparative Investigation of the Volatile Urinary Profiles in Different Phodopus Hamster Species

Stir bar sorptive extraction method was used for investigation of the urinary volatile profiles in male and female Phodopus campbelli and Phodopus sungorus hamsters. Additionally, female Phodopus roborowsky urinary profiles were characterized. A quantitative analytical approach allowed comparisons of 17 selected compounds in urine. Results showed that campbelli and sungorus species show similar urinary volatile profiles for males and females. Differences appeared only in concentrations. Several unique compounds, such as pyrazine derivatives, were found to be gender-and age-specific. P. roborowsky females exhibited a completely different urinary volatile profile from campbelli and sungorus females, featuring a unique set of substituted quinoxalines.

Capillary electrophoresis for analyzing pesticides in fruits and vegetables using solid-phase extraction and stir-bar sorptive extraction

Two procedures based on solid-phase extraction (SPE) and stir-bar sorptive extraction (SBSE) in combination with micellar electrokinetic chromatography (MEKC)–diode array detection (DAD) were compared for the simultaneous extraction of acrinathrin, bitertanol, cyproconazole, fludioxonil, flutriafol, myclobutanil, pyriproxyfen, and tebuconazole in lettuce, tomato, grape, and strawberry. Selectivity and resolution of the MEKC procedure were studied changing the pH and the molarity of the buffer, the type and the concentration of surfactant, and the methanol content in the mobile phase. A buffer consisting of 6 mM sodium tetraborate decahydrate with 75 mM of cholic acid sodium solution (pH 9.2) gave the best results. Linearity, extraction efficiencies and limits of quantitation (LOQs) of both extraction methods were compared. The recoveries obtained by SPE ranged from 40 to 106% with relative standard deviations (R.S.D.s) from 10 to 19% whereas by the SBSE method, the recoveries were 12–47% and the R.S.D.s 3–17%. The LOQs were much better by SPE (0.2–0.5 mg kg −1 depending on the processed sample amount) than those obtained by SBSE (1 mg kg −1 for each compound). Advantages and disadvantages of both procedures are also discussed. As SPE is more robust, rapid, and sensitive than SBSE, its application in combination with MEKC is recommended because provided LOQs below the MRLs established, which is not always attained by SBSE.

Changes in the Aroma Compounds of Sake during Aging

Changes in the aroma of sake during aging were investigated by aroma extract dilution analysis (AEDA) and quantitative analysis using the stir bar sorptive extraction method. In AEDA, more odor zones were detected in aged sake than in fresh sake. The dilution factors of aldehydes, polysulfides, and some esters were greater in the aged sake, and their increase during aging was confirmed through a quantitative analysis of sake stored for 0-35 years. Among these compounds, 3-methylbutanal, methional, and dimethyltrisulfide (DMTS) were present in aged sake at concentrations exceeding their odor thresholds, and the highest odor active value was observed for DMTS. Sensory tests showed that supplementation with DMTS contributed to both the total odor intensity and the sulfury odor of aged sake aroma.

Stirring bar sorptive extraction in the determination of PAHs in drinking waters

The application of a new extraction technique which is known as stir bar sorptive extraction (SBSE), followed by high-performance liquid chromatography with a fluorescence detector, was assessed for determining eight polycyclic aromatic hydrocarbons (PAHs) in water samples. The extraction conditions such as acetonitrile addition; effects of temperature and salt; and finally, extraction and desorption time profiles were studied. Once SBSE was optimized, analytical method parameters such as linearity ( r 2>0.991), precision (<9%), detection (0.5–7.3 ng/L) and quantitation (1.0–22 ng/L) limits were estimated. To correct for the 43–57% absolute recovery depending on the PAH, calibration was done with a line obtained submitting standard-spiked blank tap waters to the complete sample treatment and analysis. Consequently, relative recovery was about 100% because all water samples (those for calibration purposes and those for recovery estimation) were processed in the same way and the absolute recovery remained constant. SBSE method characteristics were checked with the analysis of real drinking waters in the search for PAHs.

Stir bar sorptive extraction for the analysis of wine cork taint

A magnetic stir bar with a polydimethylsiloxane coating was used to absorb 2,4,6-trichloroanisole, 2,3,4,5-tetrachloroanisole, pentachloroanisole and their respective phenols from synthetic and real wine samples. The stir bar sorptive extraction method was optimised to obtain the best extraction conditions in terms of temperature, time, pH and NaCl addition. The stir bar was desorbed in a thermal desorption system coupled to a gas chromatograph–mass spectrometer. The method proposed showed good linearity over the concentration range tested and correlation coefficients ranged from 0.96 to 0.99 for all the analytes. The reproducibility and repeatability of the method was estimated between 1.29 and 4.02%. With no a pre-concentration step and with a much reduced analysis time, all the analyzed compounds showed detection and quantification limits that were lower than those observed with other methods found in the bibliography. Except for pentachlorophenol due to its poor absorptivity in polydimethysiloxane, in red wines, LOD ranged between 7.56 and 61.56 pg/l, and LOQ ranged between 17.21 and 205.11 pg/l; while in white wines, the LOD ranged between 5.82 and 30.50 pg/l and LOQ ranged between 19.41 and 101.61 pg/l. These concentrations were always lower than their respective olfactory thresholds values.

Comparison of microextraction procedures to determine pesticides in oranges by liquid chromatography–mass spectrometry

A liquid chromatographic–mass spectrometric method has been developed for the determination of bitertanol, carbendazim, fenthion, flusilazole, hexythiazox, imidacloprid, methidathion, methiocarb, pyriproxyfen and trichlorfon. Two procedures, based on stir bar sorptive extraction (SBSE) and matrix solid-phase dispersion (MSPD), have been evaluated for the extraction of these compounds in oranges. Their respective advantages and disadvantages are also discussed. The recoveries obtained by MSPD ranged from 47 to 96% and the relative standard deviations (RSDs) ranged from 1 to 15%, whereas with the SBSE method the recoveries were between 8 and 84% and the RSDs between 4 and 16%. Although, the limits of quantitation of most compounds are much better (0.001–0.05 mg kg −1) by SBSE, it is not suitable to determine some polar pesticides as carbendazim, imidacloprid and trichlorfon. Results obtained by both methods were compared, in terms of sensitivity and selectivity, with a classical ethyl acetate extraction method, and the three methods were applied to analyze real samples. As MSPD is easier to perform, faster than the organic solvent extraction, and shows equal accuracy and resolution, its application for analyzing pesticides in oranges is recommended.

Determination of 2-methylisoborneol and geosmin in water by gas chromatography-mass spectrometry using stir bar sorptive extraction

A method is described for the determination of 2-MIB and geosmin by gas chromatography-mass spectrometry (GC-MS) using stir bar sorptive extraction (SBSE). The detection limits using selected ion monitoring (SIM) were compared between solid phase microextraction (SPME) and stir bar sorptive extraction (SBSE). Since polydimethylsiloxane (PDMS) is only available for stationary phase on the stir bar for SBSE, a 100-μm PDMS fiber was used for SPME due to the same sorption mechanism. The sensitivities of the SBSE method was 54 times higher for 2-MIB and 10 times higher for geosmin than those of the SPME method. The detection limits of the SBSE method evaluated in river water were 0.33 and 0.15 ng/L respectively for 2-MIB and geosmin. The reproducibilities (n = 5) were 9.2 and 3.7%, respectively, at 2 ng/L for 2-MIB and geosmin.

Determination of 2-methylisoborneol and geosmin in water by gas chromatography-mass spectrometry using stir bar sorptive extraction

A method is described for the determination of 2-MIB and geosmin by gas chromatography-mass spectrometry (GC-MS) using stir bar sorptive extraction (SBSE). The detection limits using selected ion monitoring (SIM) were compared between solid phase microextraction (SPME) and stir bar sorptive extraction (SBSE). Since polydimethylsiloxane (PDMS) is only available for stationary phase on the stir bar for SBSE, a 100-μm PDMS fiber was used for SPME due to the same sorption mechanism. The sensitivities of the SBSE method was 54 times higher for 2-MIB and 10 times higher for geosmin than those of the SPME method. The detection limits of the SBSE method evaluated in river water were 0.33 and 0.15 ng/L respectively for 2-MIB and geosmin. The reproducibilities (n = 5) were 9.2 and 3.7%, respectively, at 2 ng/L for 2-MIB and geosmin.

Acetylcholine suppresses the propagation of excitation in the rat visual cortex revealed by optical recording with voltage-sensitive dye

A multiresidue method for the analysis of 86 persistent pollutants in marine sediments at ultra-trace level has been developed and validated using pressurized liquid extraction (PLE) and stir-bar sorptive extraction (SBSE) coupled with thermal desorption and gas chromatography–triple quadrupole mass spectrometry (TD–GC–MS/MS QqQ). The compounds analyzed belong to various families such as polychlorinated biphenyls, polycyclic aromatic hydrocarbons, polybrominated diphenylethers, organophosphorus and organochlorine pesticides and other pesticides such as urons, and triazines. The analytes have very different polarities and log Kow values, which is an important parameter in the optimization of a SBSE method. Due to PLE high efficiency and throughput rates, along with the proven ability for multiresidue analysis and excellent sensitivity of SBSE, we present an efficient method. The limits of quantification obtained ranged from 0.014 to 1.0 ng g−1, with detection limits below pg g−1 levels. In order to validate the proposed methodology, quality parameters such as recovery, linearity and reproducibility were studied. Recoveries ranged from 63% to 119%, reproducibility (in terms of Relative Standard Deviation for ten determinations) was lower than 35% in all cases, and determination coefficients higher than 0.990 for all analytes. The main factors that affect PLE, SBSE and GC–MS/MS procedures were optimized. The method was applied to the analysis of nine marine sediments obtained from the nine main submarine wastewater discharge points (emissaries) presents along the coast of Tenerife Island (Canary Islands, Spain).

The effects of disparity in the peripheral field on human smooth pursuit eye movement

A multiresidue method for the analysis of 86 persistent pollutants in marine sediments at ultra-trace level has been developed and validated using pressurized liquid extraction (PLE) and stir-bar sorptive extraction (SBSE) coupled with thermal desorption and gas chromatography–triple quadrupole mass spectrometry (TD–GC–MS/MS QqQ). The compounds analyzed belong to various families such as polychlorinated biphenyls, polycyclic aromatic hydrocarbons, polybrominated diphenylethers, organophosphorus and organochlorine pesticides and other pesticides such as urons, and triazines. The analytes have very different polarities and log Kow values, which is an important parameter in the optimization of a SBSE method. Due to PLE high efficiency and throughput rates, along with the proven ability for multiresidue analysis and excellent sensitivity of SBSE, we present an efficient method. The limits of quantification obtained ranged from 0.014 to 1.0 ng g−1, with detection limits below pg g−1 levels. In order to validate the proposed methodology, quality parameters such as recovery, linearity and reproducibility were studied. Recoveries ranged from 63% to 119%, reproducibility (in terms of Relative Standard Deviation for ten determinations) was lower than 35% in all cases, and determination coefficients higher than 0.990 for all analytes. The main factors that affect PLE, SBSE and GC–MS/MS procedures were optimized. The method was applied to the analysis of nine marine sediments obtained from the nine main submarine wastewater discharge points (emissaries) presents along the coast of Tenerife Island (Canary Islands, Spain).

1611 Acetylcholine suppresses the propagation of excitation in the rat visual cortex revealed by optical recording with voltage-sensitive dye

A multiresidue method for the analysis of 86 persistent pollutants in marine sediments at ultra-trace level has been developed and validated using pressurized liquid extraction (PLE) and stir-bar sorptive extraction (SBSE) coupled with thermal desorption and gas chromatography–triple quadrupole mass spectrometry (TD–GC–MS/MS QqQ). The compounds analyzed belong to various families such as polychlorinated biphenyls, polycyclic aromatic hydrocarbons, polybrominated diphenylethers, organophosphorus and organochlorine pesticides and other pesticides such as urons, and triazines. The analytes have very different polarities and log Kow values, which is an important parameter in the optimization of a SBSE method. Due to PLE high efficiency and throughput rates, along with the proven ability for multiresidue analysis and excellent sensitivity of SBSE, we present an efficient method. The limits of quantification obtained ranged from 0.014 to 1.0 ng g−1, with detection limits below pg g−1 levels. In order to validate the proposed methodology, quality parameters such as recovery, linearity and reproducibility were studied. Recoveries ranged from 63% to 119%, reproducibility (in terms of Relative Standard Deviation for ten determinations) was lower than 35% in all cases, and determination coefficients higher than 0.990 for all analytes. The main factors that affect PLE, SBSE and GC–MS/MS procedures were optimized. The method was applied to the analysis of nine marine sediments obtained from the nine main submarine wastewater discharge points (emissaries) presents along the coast of Tenerife Island (Canary Islands, Spain).