Development of a method for the determination of UV filters in water samples using stir bar sorptive extraction and thermal desorption-gas chromatography-mass spectrometry

Stir bar sorptive extraction (SBSE) in combination with thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS) was applied for the determination of 9 UV filters in water samples. The stir bar coated with polydimethylsiloxane (PDMS) was added to 20 mL of water sample at pH 2 (10% MeOH) and stirred at 1000 rpm for 180 min. Then, the stir bar was subjected to TD-GC-MS. The desorption conditions (desorption temperature and desorption time) and SBSE parameters (ionic strength, pH, presence of organic solvent and time) were optimised using a full factorial design and a Box-Behnken design, respectively. The method shows good linearity (correlation coefficients >0.994) and reproducibility (RSD<16%). The extraction efficiencies were above 63% for all the compounds. Detection limits were between 0.2 and 63 ng/L. The developed method offers the ability to detect several UV filters at ultra-low concentration levels with only 20 mL of sample volume. The effectiveness of the method was tested by analysing real samples such as lake water, river water and treated wastewater. The application of the method allowed reporting the levels of UV filters in environmental water samples.     

Headspace stir bar sorptive extraction followed by thermal desorption and gas chromatography with mass spectrometry to determine musk fragrances in sludge samples without sample pretreatment

A direct, simple and solvent‐free method based on headspace stir bar sorptive extraction and thermal desorption gas chromatography with mass spectroscopy was developed to determine 13 musk fragrances (six polycyclic musks, three nitro musks and four macrocyclic musks) in sludge without sample treatment. The optimal headspace stir bar sorptive extraction conditions were achieved when a polydimethylsiloxane stir bar was exposed for 45 min in the headspace of a 10 mL vial filled with 100 mg of sludge mixed with 0.2 mL of water stirred at 750 rpm at 80°C. The stir bar was then desorbed in the thermal desorption gas chromatography and mass spectrometry system, obtaining limits of detection between 5 and 30 ng/g. The method applicability was tested with sewage sludge from two urban wastewater treatment plants and from a potable water treatment plant. Results showed galaxolide and tonalide to be the most abundant musk fragrances found in wastewater treatment plants with maximal concentrations of 9240 and 7500 ng/g, respectively. Maximum concentration levels between 35 and 635 ng/g were found for musk ketone, musk moskene, traseolide, phantolide and celestolide in this kind of samples. Concentrations below the limits of quantitation of phantolide, galaxolide, tonalide and musk ketone were found in sludge from a potable water treatment plant.     

Preparation of a novel sorptive stir bar based on vinylpyrrolidone‐ethylene glycol dimethacrylate monolithic polymer for the simultaneous extraction of diazepam and nordazepam from human plasma

A new monolithic coating based on vinylpyrrolidone‐ethylene glycol dimethacrylate polymer was introduced for stir bar sorptive extraction. The polymerization step was performed using different contents of monomer, cross‐linker and porogenic solvent, and the best formulation was selected. The quality of the prepared vinylpyrrolidone‐ethylene glycol dimethacrylate stir bars was satisfactory, demonstrating good repeatability within batch (relative standard deviation < 3.5%) and acceptable reproducibility between batches (relative standard deviation < 6.0%). The prepared stir bar was utilized in combination with ultrasound‐assisted liquid desorption, followed by high‐performance liquid chromatography with ultraviolet detection for the simultaneous determination of diazepam and nordazepam in human plasma samples. To optimize the extraction step, a three‐level, four‐factor, three‐block Box–Behnken design was applied. Under the optimum conditions, the analytical performance of the proposed method displayed excellent linear dynamic ranges for diazepam (36–1200 ng/mL) and nordazepam (25–1200 ng/mL), with correlation coefficients of 0.9986 and 0.9968 and detection limits of 12 and 10 ng/mL, respectively. The intra‐ and interday recovery ranged from 93 to 106%, and the relative standard deviations were less than 6%. Finally, the proposed method was successfully applied to the analysis of diazepam and nordazepam at their therapeutic levels in human plasma. The novelty of this study is the improved polarity of the stir bar coating and its application for the simultaneous extraction of diazepam and its active metabolite, nordazepam in human plasma sample. The method was more rapid than previously reported stir bar sorptive extraction techniques based on monolithic coatings, and exhibited lower detection limits in comparison with similar methods for the determination of diazepam and nordazepam in biological fluids.     

Stir bar sorptive extraction based on restricted access material for the direct extraction of caffeine and metabolites in biological fluids

A biocompatible stir bar sorptive extraction (SBSE) device was prepared using an alkyl-diol-silica (ADS) restricted access material (RAM) as the SBSE coating. The RAM-SBSE bar was able to simultaneously fractionate the protein component from a biological sample, while directly extracting caffeine and its metabolites, overcoming the present disadvantages of direct sampling in biological matrices by SBSE, such as fouling of the extraction coating by proteins. Desorption of the analytes was performed by stirring the bar in a water/ACN mixture (3/1, v/v) and subsequently reconcentrating the sample solution in water to enable HPLC-UV analysis to be performed. The limit of detection, based on a signal to noise ratio of 3, for caffeine was 25 ng/mL in plasma. The method was confirmed to be linear over the range of 0.5-100 microg/mL of caffeine with an average linear coefficient (R2) value of 0.9981. The injection repeatability and intra-assay precision of the method were evaluated over ten injections, resulting in a %RSD of approximately 8%. The RAM-SBSE device was robust (>50 extraction in plasma without significant signal loss) and simple to use, providing many direct extractions and subsequent determination of caffeine and its metabolites in biological fluids. In contrast to existing sample preparation methods for the analysis of caffeine and selected metabolites in biological fluids, this feasibility study using a biocompatible SBSE approach was advantageous in terms of simplifying the sample preparation procedures.     

Sol–gel coating of poly(ethylene glycol)‐grafted multiwalled carbon nanotubes for stir bar sorptive extraction and its application to the analysis of polycyclic aromatic hydrocarbons in water

Poly(ethylene glycol) grafted onto carboxyl‐terminated multi‐walled carbon nanotubes were prepared by the sol–gel technique as a stationary phase for stir bars. The analytical methodology included stir bar sorptive extraction with micellar desorption followed by liquid chromatography. Polycyclic aromatic hydrocarbons were used as the model compounds to evaluate the extraction performance. The extraction efficiency, for the determination of polycyclic aromatic hydrocarbons from water samples, was optimized based on a chemometrics approach. The effect of the experimental parameters on the extraction response was investigated and the optimum extraction conditions were selected. Under the optimum conditions, the proposed method showed a good linearity within the different ranges for different analytes (e.g. 0.05–500 ng/mL for phenanthrene), a square of the correlation coefficient was higher than 0.999, and an appropriate limit of detection in the range of 0.013–0.072 ng/mL. The recoveries in all cases were above 94%, with relative standard deviations below 2.4%.     

Analysis of biogenic carbonyl compounds in rainwater by stir bar sorptive extraction technique with chemical derivatization and gas chromatography‐mass spectrometry

Stir bar sorptive extraction is a powerful technique for the extraction and analysis of organic compounds in aqueous matrices. Carbonyl compounds are ubiquitous components in rainwater, however, it is a major challenge to accurately identify and sensitively quantify carbonyls from rainwater due to the complex matrix. A stir bar sorptive extraction technique was developed to efficiently extract carbonyls from aqueous samples following chemical derivatization by O‐(2,3,4,5,6‐pentafluorobenzyl) hydroxylamine hydrochloride. Several commercial stir bars in two sizes were used to simultaneously measure 29 carbonyls in aqueous samples with detection by gas chromatography with mass spectrometry. A 100 mL aqueous sample was extracted by stir bars and the analytes on stir bars were desorbed into a 2 mL solvent solution in an ultrasonic bath. The preconcentration Coefficient for different carbonyls varied between 30 and 45 times. The limits of detection of stir bar sorptive extraction with gas chromatography mass spectrometry for carbonyls (10–30 ng/L) were improved by ten times compared with other methods such as gas chromatography with electron capture detection and stir bar sorptive extraction with high‐performance liquid chromatography and mass spectrometry. The technique was used to determine carbonyls in rainwater samples collected in York, UK, and 20 carbonyl species were quantified including glyoxal, methylglyoxal, isobutenal, 2‐hydroxy ethanal.     

Evaluation of a method for the simultaneous quantification of N‐nitrosamines in water samples based on stir bar sorptive extraction combined with high‐performance liquid chromatography and diode array detection

A simple, sensitive, and reliable procedure based on stir bar sorptive extraction coupled with high‐performance liquid chromatography was applied to simultaneously extract and determine three semipolar nitrosamines including N‐nitrosodibutylamine, N‐nitrosodiphenylamine, and N‐nitrosodicyclohexylamine. To achieve the optimum conditions, the effective parameters on the extraction efficiency including desorption solvent and time, ionic strength of sample, extraction time, and sample volume were systematically investigated. The optimized extraction procedure was carried out by stir bars coated with polydimethylsiloxane. Under optimum extraction conditions, the performance of the proposed method was studied. The linear dynamic range was obtained in the range of 0.95–1000 ng/mL (r = 0.9995), 0.26–1000 ng/mL (r = 0.9988) and both 0.32–100 ng/mL (r = 0.9999) and 100–1000 ng/mL (r = 0.9998) with limits of detection of 0.28, 0.08, and 0.09 ng/mL for N‐nitrosodibutylamine, N‐nitrosodiphenylamine, and N‐nitrosodicyclohexylamine, respectively. The average recoveries were obtained >81%, and the reproducibility of the proposed method presented as intra‐ and interday precision were also found with a relative standard deviation <6%. Finally, the proposed method was successfully applied to the determination of trace amounts of selected nitrosamines in various water and wastewater samples and the obtained results were confirmed using mass spectrometry.     

Quantification of testosterone and epitestosterone in human urine samples by stir bar sorptive extraction--thermal desorption--gas chromatography/mass spectrometry: application to HIV-positive urine samples

A simple method is described for the measurement of testosterone (T) and epitestosterone (ET) in human urine samples. The deconjugated steroids were extracted directly from the samples by stir bar sorptive extraction (SBSE) and derivatized in situ on the stir bar by headspace acylation prior to thermal desorption and GC/MS. Extraction and derivatization parameters, namely salt addition, temperature, and time, were optimized to improve the recovery of T and ET by SBSE. The limits of quantification (S/N 10) were 0.9 ng/mL for T and 2.8 ng/mL for ET. Quantification of the steroids in urine samples was performed using standard addition to avoid the influence of matrix effects. The method was applied for the measurement of urinary T and ET in a group of healthy volunteers and HIV+ patients. Decreased levels of T were detected in the HIV+ group, whereas the excretion of ET was comparable for the two groups. Further clinical research is required to elucidate the biomarker significance of the T/ET ratio in HIV infection.     

Mercury speciation and analysis in drinking water by stir bar sorptive extraction with in situ propyl derivatization and thermal desorption-gas chromatography-mass spectrometry

A method for mercury analysis and speciation in drinking water was developed, which involved stir bar sorptive extraction (SBSE) with in situ propyl derivatization and thermal desorption (TD)-GC-MS. Ten millilitre of tap water or bottled water was used. After a stir bar, pH adjustment agent and derivatization reagent were added, SBSE was performed. Then, the stir bar was subjected to TD-GC-MS. The detection limits were 0.01 ng mL(-1) (ethylmercury; EtHg), 0.02 ng mL(-1) (methylmercury; MeHg), and 0.2 ng mL(-1) (Hg(II) and diethylmercury (DiEtHg)). The method showed good linearity and correlation coefficients. The average recoveries of mercury species (n=5) in water samples spiked with 0.5, 2.0, and 6.0 ng mL(-1) mercury species were 93.1-131.1% (RSD<11.5%), 90.1-106.4% (RSD<7.8%), and 94.2-109.6% (RSD<8.8%), respectively. The method enables the precise determination of standards and can be applied to the determination of mercury species in water samples.     

应用搅拌棒吸附萃取-热脱附-气相色谱-质谱分析烟用香料的化学成分

应用搅拌棒吸附萃取法(SBSE)提取烟用香料的化学成分,并利用热脱附(TD)和色谱-质谱联用(GC-MS)进行分析。对影响萃取效果的因素(萃取时间和氯化钠的加入量)进行了考察,并采用正交试验法对影响热脱附的3个主要因素(脱附温度、脱附时间和冷阱温度)进行了优化,得到了较优的实验条件。对方法的重现性进行了考察,同一样品6次测定所得30个组分的峰面积的相对标准偏差（RSD）平均值小于10%,说明所建立方法的重现性较好。在样品中鉴别出酯类、酮类和醛类等30种不同化学组分,这些物质反映了该香料的香气特点。实验证明SBSE和TD适用于烟用香料的快速分析测定。     

Development of a sensitive determination method for benzotriazole UV stabilizers in enviromental water samples with stir bar sorption extraction and liquid desorption prior to ultra‐high performance liquid chromatography with tandem mass spectrometry

Benzotriazole UV stabilizers are emerging compounds used in personal care products and can enter surface water after passing through wastewater treatment plants without being removed. Because these analytes are strongly hydrophobic, there is an environmental risk of accumulation in solid matrices and magnification through the trophic chain. In this work, a method based on stir bar sorption extraction with liquid desorption is presented for the extraction of benzotriazole UV stabilizers from water samples. Stir bar sorptive extraction was combined with ultra‐high performance LC with MS/MS detection. All important factors affecting the stir bar sorptive extraction procedure are discussed, and the optimized method was applied to seawater and wastewater samples from Gran Canaria Island, providing good selectivity and sensitivity with LODs and limits of quantification in the range of 18.4–55.1 and 61.5–184 ng/L, respectively. Recoveries between 68.4–92.2% were achieved for the more polar compounds, whereas the recoveries were lower for the two less polar compounds, most likely due to their strong absorption into the polydimethylsiloxane stir bar phase that does not allows the complete desorption. The repeatability studies gave RSDs of between 6.45 and 12.6% for all compounds in the real samples.     

Development of a stir bar sorptive extraction method for the determination of volatile compounds in orange juices

A stir bar sorptive extraction method for the determination of volatile compounds in orange juices was developed. The extraction variables were optimized using a reduced two‐level factorial screening design (2^5‐1), and the most suitable analytical conditions for the extraction of the studied compounds were: sample volume 10 mL, extraction time 60 min, stirring speed 1800 rpm, NaCl amount 30% (weight/volume), and twister length 10 mm. The optimized method was further validated, obtaining good linearity and detection and quantification limits low enough to correctly determine the studied compounds. As well, for most of the studied compounds precision and recovery values were good. Several orange juice samples (squeezed and commercial) were extracted following the optimized extraction method and analyzed by gas chromatography coupled to mass spectrometry detection. The method has proven to be suitable for the determination of the aroma of orange juice, of which limonene was the major volatile compound in all the studied samples.     

聚酰亚胺固相萃取搅拌棒的制备及其在环境水中酚类的分析应用

利用相转换法制备了聚酰亚胺吸附萃取搅拌棒,用5种有机酚作为评价标样,并与现有商品化吸附萃取搅拌棒进行比较。优化了萃取搅拌速度、溶液离子强度、萃取温度、萃取时间以及热解析温度和时间。在最佳实验条件下,100 mL 样品,30% NaCl,在25℃下,经活化5 min 后的聚酰亚胺吸附搅拌棒萃取30 min (800 r/ min),然后300℃热解析4 min,使目标物脱附,再进行色谱分析。目标物在大于两个数量级浓度范围内具有良好的线性(R≥0.9995),定量限(LOQ,S/ N=10)为0.028~0.123μg/ L,重复性为1.6%~9.7%。将SBSE 与气相色谱-质谱联用,对海水、自来水和污水中的酚类进行定性与定量分析,结果表明,聚酰亚胺吸附萃取搅拌棒具有良好的选择性,最高热解析温度350℃,在分析水中痕量极性化合物领域具有广阔应用前景。     

搅拌棒吸附萃取结合气相色谱/质谱/质谱法同时测定饮料和果酱中的7种防腐剂

建立了搅拌棒吸附萃取进行前处理,气相色谱-质谱/质谱法测定饮料和果酱中7种食品防腐剂的方法.饮料和果酱样品用pH=3的30% NaCl溶液稀释,使用搅拌棒进行吸附萃取,吸附在搅拌棒上的防腐剂在热解析单元进行热解析,在冷进样口进行捕集后通过程序升温进入气相色谱,使用串联质谱的多反应监测(MRM)同时检测饮料和果酱中的7种防腐剂(苯甲酸、山梨酸以及对羟基苯甲酸甲酯、对羟基苯甲酸丙酯、对羟基苯甲酸异丙酯、对羟基苯甲酸异丁酯和对羟基苯甲酸庚酯).苯甲酸、山梨酸在40～400 mg/L浓度范围内,对羟基苯甲酸甲酯、对羟基苯甲酸丙酯、对羟基苯甲酸异丙酯和对羟基苯甲酸异丁酯在4～40 mg/L浓度范围内,对羟基苯甲酸正庚酯在0.4～4 mg/L浓度范围内,各组分响应峰面积与其相应浓度呈良好相关性,r>0.99.苯甲酸和山梨酸的检出限分别为37和47 mg/L,对羟基苯甲酸酯类为0.62～6.67 mg/L.方法的回收率为84.0%～125.0%;精确度为3.0%～18.1%.本方法灵敏度高,能够同时快速检测饮料和果酱中7种防腐剂.     

Simple and sensitive monitoring of sulfonamide veterinary residues in milk by stir bar sorptive extraction based on monolithic material and high performance liquid chromatography analysis

A simple, rapid, and sensitive method for the quantitative monitoring of five sulfonamide antibacterial residues (SAs) in milk was developed by stir bar sorptive extraction (SBSE) coupling to high performance liquid chromatography with diode array detection. The analytes were concentrated by SBSE based on poly (vinylimidazole–divinylbenzene) monolithic material as coating. The extraction procedure was very simple, milk was diluted with water then directly sorptive extraction without elimination of fats and protein in samples was required. To achieve optimum extraction performance for SAs, several parameters, including extraction and desorption time, desorption solvent, ionic strength and pH value of sample matrix were investigated. Under the optimized experimental conditions, low detection limits (S/N = 3) quantification limits (S/N = 10) of the proposed method for the target compounds were achieved within the range of 1.30–7.90 ng/mL and 4.29–26.3 ng/mL from spiked milk, respectively. Good linearities were obtained for SAs with the correlation coefficients (R²) above 0.996. Finally, the proposed method was successfully applied to the determination of SAs compounds in different milk samples and satisfied recoveries of spiked target compounds in real samples were obtained.     

Determination of steroid sex hormones in urine matrix by stir bar sorptive extraction based on monolithic material and liquid chromatography with diode array detection

A simple, rapid and sensitive method for simultaneous determination of six steroid sex hormones in urine matrix was developed by the combination of stir bar sorptive extraction (SBSE) with high performance liquid chromatography (HPLC) and diode array detection (DAD). A poly (methacrylic acid stearyl ester-ethylene dimethacrylate) was synthesized and selected as SBSE extraction medium. To achieve the optimum extraction performance, several parameters, including agitation speed, desorption solvent, extraction and desorption time, pH value, inorganic salt and organic solvent content of the sample matrix were investigated. Under the optimized experimental conditions, low detection limits (S/N=3) and quantification limits (S/N=10) of the proposed method for the target compounds were achieved within the range of 0.062-0.38 and 0.20-1.20 ng/mL, respectively from spiked urine, respectively. The calibration curves of six steroid sex hormones showed good linearity ranging from 1.0 to 200 ng/mL with linear coefficient R2 values above 0.990. Good method reproducibilities presented as intra- and inter-day precisions were also found with the R.S.D.s less than 9.2 and 10.0%, respectively. Finally, the proposed method was successfully applied to the determination of the target compounds in a urine sample from a pregnant woman.     

大体积搅拌棒吸附萃取技术与热脱附-气相色谱-质谱法测定地表水中多环芳烃

基于搅拌棒吸附萃取(SBSE)技术建立了气相色谱-质谱测定地表水中16种多环芳烃(PAHs)的分析方法。该法采用多搅拌吸附棒同时富集,依次热脱附冷聚焦后进样的方式有效解决了搅拌棒吸附时间长、富集水样体积小等问题。优化后的结果表明,在0.2~10 ng/L范围内(萘为0.5~10 ng/L范围),16种PAHs的线性关系良好,相关系数(r)均0.99,方法检出限(MDL)为0.03~0.20 ng/L(萘为0.50 ng/L)。用该方法对钱塘江流域地表水进行测定,共检测出11种PAHs,含量为0.13~1.57 ng/L,不同添加水平下的加标回收率为75.6%~108.9%。该法可应用于地表水样品中该类物质的超痕量检测。     

Determination of trace polychlorinated biphenyls and organochlorine pesticides in water samples through large‐volume stir bar sorptive extraction method with thermal desorption gas chromatography

A fast and sensitive analytical method based on stir bar sorptive extraction technology with gas chromatography and mass spectrometry was developed to simultaneously analyze 18 kinds of polychlorinated biphenyls and 20 kinds of organochlorine pesticides in aqueous samples. A long adsorption time and small sample volume, which are problems encountered in conventional methods of stir bar sorptive extraction, were effectively solved by simultaneously using multiple stir bars for enrichment with sequential cryofocusing and merged injection. Optimized results showed good linear coefficients in the range of 10–500 ng/L and the method detection limits of 0.12–2.07 ng/L for polychlorinated biphenyls and organochlorine pesticides. The recovery ratios of the spiked samples at different concentrations were between 64.7 and 111.0%, and their relative standard deviations ranged from 0.9 to 17.6%. Four types of the studied compounds were determined in Qiantang River water samples, and their contents were between 0.82 and 5.00 ng/L.     

Stir bar sorptive extraction coupled to thermodesorption-gas chromatography-mass spectrometry for the determination of insect repelling substances in water samples

Stir bar sorptive extraction (SBSE) in combination with thermodesorption-gas chromatography-mass spectrometry (TD-GC-MS) was applied for the determination of eight insect repellents and synergists in water samples. The stir bar coated with polydimethylsiloxane (PDMS) was added to 20 mL of water sample with 4 g NaCl and stirred at 1000 rpm for 180 min. Then, the stir bar was subjected to TD-GC-MS. SBSE parameters (ionic strength, presence of organic solvent and time) were optimised. Blank contamination and carryover problems were also studied. The method affords detection limits between 0.5 and 30 ng/L, except for dimethyl phthalate (DMP) (150 ng/L) due to blank contamination problems. It shows good linearity with correlation coefficients over 0.997 and reproducibility (RSD) below 20%. The extraction efficiencies were between 29% for DMP and 80% for di-n-propyl isocinchomeronate (R-326). The feasibility of the method was tested by analysing real samples such as lake water, river water and wastewater.     

Coupling stir bar sorptive extraction‐dispersive liquid–liquid microextraction for preconcentration of triazole pesticides from aqueous samples followed by GC‐FID and GC‐MS determinations

Stir bar sorptive extraction (SBSE) combined with dispersive liquid–liquid microextraction (DLLME) has been developed as a new approach for the extraction of six triazole pesticides (penconazole, hexaconazole, diniconazole, tebuconazole, triticonazole and difenconazole) in aqueous samples prior to GC‐flame ionization detection (GC‐FID). A series of parameters that affect the performance of both steps were thoroughly investigated. Under optimized conditions, aqueous sample was stirred using a stir bar coated with octadecylsilane (ODS) and then target compounds on the sorbent (stir bar) were desorbed with methanol. The extract was mixed with 25 μL of 1,1,2,2‐tetrachloroethane and the mixture was rapidly injected into sodium chloride solution 30% w/v. After centrifugation, an aliquot of the settled organic phase was analyzed by GC‐FID. The methodology showed broad linear ranges for the six triazole pesticides studied, with correlation coefficients higher than 0.993, lower LODs and LOQs between 0.53–24.0 and 1.08–80.0 ng/mL, respectively, and suitable precision (RSD < 5.2%). Moreover, the developed methodology was applied for the determination of target analytes in several samples, including tap, river and well waters, wastewater (before and after purification), and grape and apple juices. Also, the presented SBSE‐DLLME procedure followed by GC‐MS determination was performed on purified wastewater. Penconazole, hexaconazole and diniconazole were detected in the purified wastewater that confirmed the obtained results by GC‐FID determination. In short, by coupling SBSE with DLLME, advantages of two methods are combined to enhance the selectivity and sensitivity of the method. This method showed higher enrichment factors (282–1792) when compared with conventional methods of sample preparation to screen pesticides in aqueous samples.