Analyses of polychlorinated biphenyls in waters and wastewaters using vortex-assisted liquid-liquid microextraction and gas chromatography-mass spectrometry

A method was developed for viable and rapid determination of seven polychlorinated biphenyls (PCBs) in water samples with vortex-assisted liquid-liquid microextraction (VALLME) using gas chromatography-mass spectrometry (GC-MS). At first, the most suitable extraction solvent and extraction solvent volume were determined. Later, the parameters affecting the extraction efficiency such as vortex extraction time, rotational speed of the vortex, and ionic strength of the sample were optimized by using a 2(3) factorial experimental design. The optimized extraction conditions for 5 mL water sample were as follows: extractant solvent 200 μL of chloroform; vortex extraction time of 2 min at 3000 rpm; centrifugation 5 min at 4000 rpm, and no ionic strength. Under the optimum condition, limits of detection (LOD) ranged from 0.36 to 0.73 ng/L. Mean recoveries of PCBs from fortified water samples are 96% for three different fortification levels and RSDs of the recoveries are below 5%. The developed procedure was successfully applied to the determination of PCBs in real water and wastewater samples such as tap, well, surface, bottled waters, and municipal, treated municipal, and industrial wastewaters. The performance of the proposed method was compared with traditional liquid-liquid extraction (LLE) of real water samples and the results show that efficiency of proposed method is comparable to the LLE. However, the proposed method offers several advantages, i.e. reducing sample requirement for measurement of target compounds, less solvent consumption, and reducing the costs associated with solvent purchase and waste disposal. It is also viable, rapid, and easy to use for the analyses of PCBs in water samples by using GC-MS.     

漂浮液滴固化分散液液微萃取与高效液相色谱联用检测环境水样中的3种烷基苯酚

建立了漂浮液滴固化分散液液微萃取(DLLME-SFO)方法,以脂肪酸作为萃取剂,以甲醇作为分散剂,与高效液相色谱联用检测了环境水样中3种烷基苯酚。对影响前处理方法的因素进行了详细考察,在最佳萃取条件(60μL萃取剂辛酸、600μL分散剂甲醇、pH值为2.0~8.0、10 mL水样中加入0.5 g NaCl)下,3种烷基苯酚在20~1 500μg/L范围内具有良好的线性关系,相关系数不小于0.998 5,3种目标化合物的检出限为0.45~0.61μg/L,富集倍数为145~169,实际样品中3个水平的加标回收率为80.1%~109.9%。该方法将脂肪酸作为萃取剂,与HPLC联用实现了烷基苯酚的富集与检测,为环境水样中烷基苯酚的检测提供了对环境友好的前处理新方法。     

Determination of phenolic compounds in medicinal plants from the Lamiaceae family

A procedure for the determination of Phenolic compounds in extracts from the medicinal plants of the Lamiaceae family—garden sage (Salvia officinalis L.), creeping thyme (Thymus serpyllum L.), wild marjoram (Origanum vulgare L.), and common balm (Melissa officinalis L.)—obtained under different extraction conditions was developed. The identification of the extracted compounds was performed and their qualitative and quantitative composition was established by HPLC with diode array and mass-spectrometric detection with consideration for the obtained characteristics of the standard samples of individual components. The test samples of medicinal herbs contained caffeic acid (0.19–0.62 mg/g) and rosmaric acid (4–23 mg/g); the highest rosmaric acid content (23 mg/g) was found in wild marjoram, and the lowest content (4 mg/g), in creeping thyme. The extracts of wild marjoram contained the greatest amounts of Phenolic compounds; rosmaric acid and luteolin-7-O-β-D-glucuronide were major components, whereas protocatechuic, 3-O-caffeoylquinic, and caffeic acids were minor components.     

A procedure for determination of cobalt in water samples after dispersive liquid–liquid microextraction

In this work, a procedure for preconcentration of cobalt using dispersive liquid–liquid microextraction (DLLME) with the reagent Br-TAO as complexing reagent was developed. The procedure is based on a ternary system of solvents, where appropriate amounts of the extraction solvent, disperser solvent and the chelating agent Br-TAO are directly injected into an aqueous solution containing Co(II). A cloudy mixture is formed and the ions are extracted in the fine droplets of the extraction solvent. After extraction, the phase separation is performed with a rapid centrifugation, and cobalt is determined in the enriched phase by FAAS. Under the optimized conditions, the detection limit obtained was 0.9 µg L^{− 1}. The enrichment factor and the consumptive index were 16 and 0.31 mL, respectively. The accuracy of the method was tested by the determination of cobalt in certified reference material of spinach leaves, NIST 1570a. The proposed procedure was successfully applied to the determination of cobalt in water samples.     

Design of a flow injection method for chlorophyll determination in in vitro plants

A flow injection (FIA) method was designed for the determination of chlorophylls a and b in small in vitro Dieffenbachia maculata “Sublime” plants. In the first step, the pigments from spinach leaves were separated, purified by solvent extraction and freeze–dried, to obtain standards for the FIA optimization. The sample extraction procedure was optimized. Four solvents were tested: diethyl ether, methanol, acetone and ethanol. The ethanol 96% was the optimal solvent for FIA purposes. It allows to the efficient extraction of the pigments and water can be used as carrier. The best FIA conditions found for the quasi-simultaneous quantification of chlorophylls a and b were a flow rate of 10.84 mL min⁻¹, a sample injection volume of 1.45 mL and a reactor length of 63 cm. The detection was performed with the automatic wavelength scanning Cintra 10e spectrometer, at 649 and 665 nm. The results obtained by the FIA method were compared to those obtained by the Arnon method. A deviation less than 5% was found between results for both methods. The concentration (mg g⁻¹) of chlorophylls a and b during three periods of the plants (in vitro, acclimatization, and adult) was determined to evaluate the whole in vitro procedure. It was found an increment of both pigment concentrations since the in vitro step till the adult stage, while the chlorophylls a to b ratio decreases. The designed method is suitable especially for the determination of the pigments at low concentrations in small samples with appropriate analytical quality.     

基于轻质萃取剂的溶剂去乳化分散液-液微萃取-气相色谱法测定水样中多环芳烃

以密度小于水的轻质溶剂为萃取剂,建立了无需离心步骤的溶剂去乳化分散液-液微萃取-气相色谱(SD-DLLME-GC)测定水样中多环芳烃的新方法。传统分散液-液微萃取技术一般采用密度大于水的有机溶剂为萃取剂,并需要通过离心步骤促进分相。而本方法以密度比水小的轻质溶剂甲苯为萃取剂,将其与丙酮(分散剂)混合并快速注入水样,获得雾化体系;然后注入乙腈作为去乳化剂,破坏该雾化体系,无需离心,溶液立即澄清、分相;取上层有机相(甲苯)进行GC分析。考察了萃取剂、分散剂、去乳化剂的种类及其体积等因素对萃取率的影响。以40 μL甲苯为萃取剂,500 μL丙酮为分散剂,800 μL乙腈为去乳化剂,方法在20～500 μg/L范围内呈现出良好的线性(r2=0.9942～0.9999),多环芳烃的检出限(S/N=3)为0.52～5.11 μg/L。用所建立的方法平行测定5份质量浓度为40 μg/L的多环芳烃标准水样,其含量的相对标准偏差为2.2%～13.6%。本法已成功用于实际水样中多环芳烃的分析,并测得其加标回收率为80.2%～115.1%。     

Validation of a one-step extraction/methylation method for determination of fatty acids and cholesterol in marine tissues

A simple and fast direct extraction/methylation with methanolic hydrogen chloride was validated for determination of fatty acids (FA) in marine tissues. Three parameters: reaction time, temperature and presence of non-polar solvent, were studied by an experimental 2(3) full factorial design. The method was validated for five different types of samples; cod liver (high lipid content >60%, mainly triacylglycerol), cod muscle (low lipid content, approximately 1%, mainly phospholipids), cod plasma (lipid content, approximately 2%, mainly lipoprotein complex, high water amount), cod testis (lipid content approximately 3%, high levels of cholesterol), and herring muscle (lipid content approximately 7%). The one-step procedure for extraction/methylation of wet tissues was compared with the traditional procedure of extraction of the lipids by the Folch method (chloroform/methanol, 2:1, v/v), followed by methylation. The two methods gave similar FA profiles. The one-step extraction/methylation procedure gave a higher recovery of the total FA than the traditional procedure. Problems with carry-over peaks of cholesterol from previous samples were avoided by application of extra long GC temperature programs. The cholesterol decomposed to some degree under the preceding methanolysis step, giving several peaks in the chromatograms. The decomposition peaks were identified by mass spectrometry as cholestdienes originating from dehydration of cholesterol, a metylether of cholesterol and a cholesteryl chloride. These cholesterol artefacts can be used for quantitative determination of cholesterol in the samples. Standard samples of cholesterol were determined with high accuracy, (R(2)>0.99), and cholesterol in cod plasma was compared with good agreement (R(2)=0.97) to an enzymatic method.     

Hydrophobic deep eutectic solvent as a green extractant for high‐performance liquid chromatographic determination of tetracyclines in water samples

A green extractant, hydrophobic deep eutectic solvent was first introduced for extraction of tetracycline, oxytetracycline, and chlortetracycline from environmental water samples prior to high‐performance liquid chromatography determination. Deep eutectic solvents consist of methyltrioctylammonium chloride and various medium‐chain alcohols/acids, and are easy in preparation, low cost and toxicity, desirably biodegradable, and biocompatible. The overall time required for sample preparation was 6 min and the volume of organic solvent used for extraction was only 400 µL. Under the optimized extraction condition, the present method yielded low limit of detection (0.5–2.0 ng/mL), acceptable precision (relative standard deviations < 9.7%), good linearity from 2.0 to 500 ng/mL (r² ≥ 0.9991). This optimized procedure was applied for determination of tetracyclines in different water samples with desirable spiked recovery ranged from 77.5 to 87.6%. There is, therefore, a great potential to further expand application of the method for investigation of other ultra‐trace analyte(s) in environmental matrixes.     

Determination of caffeine in black tea leaves by Fourier transform infrared spectrometry using multiple linear regression

A simple and fast analytical procedure was developed for the determination of caffeine in black tea leaves. The method is based on multiple linear regression treatment of Fourier transform infrared spectrometric data obtained in the wave number range 1800–1300 cm⁻¹ after extraction of caffeine in CHCl₃ from tea samples, wetted with an aqueous solution of NH₃ (0.1 M). The procedure requires no complex sample preparation. It provided a limit of detection of 0.035 mg/ml, a sampling frequency of 6 h⁻¹ and a coefficient of variation of 0.8% for five independent measurements of a tea sample with 3.68% w/w caffeine content. This procedure provides a drastic reduction in the consuming organic solvent for each sample compare to that of the reference chromatographic determination. The accuracy of technique is evaluated by comparing the obtained results with those of a reference HPLC technique. An average value of 3.60±0.07% w/w was obtained by HPLC for a powdered tea sample which is compromising when is compared to 3.68±0.03% (w/w) obtained by this FTIR technique.     

Analysis of polycyclic aromatic hydrocarbons in water and beverages using membrane-assisted solvent extraction in combination with large volume injection-gas chromatography-mass spectrometric detection

Membrane-assisted solvent extraction (MASE) in combination with large volume injection-gas chromatography-mass spectrometry (LVI-GC-MS) was applied for the determination of 16 polycyclic aromatic hydrocarbons (PAHs) in aqueous samples. The MASE conditions were optimized for achieving high enrichment of the analytes from aqueous samples, in terms of extraction conditions (shaking speed, extraction temperature and time), extraction solvent and composition (ionic strength, sample pH and presence of organic solvent). Parameters like linearity and reproducibility of the procedure were determined. The extraction efficiency was above 65% for all the analytes and the relative standard deviation (RSD) for five consecutive extractions ranged from 6 to 18%. At optimized conditions detection limits at the ng/L level were achieved. The effectiveness of the method was tested by analyzing real samples, such as river water, apple juice, red wine and milk.     

Rapid method for the determination of organochlorine pesticides and PCBs in fish muscle samples by microwave-assisted extraction and analysis of extracts by GC-ECD

A procedure for the multiresidue determination of organochlorine pesticides and polychlorinated biphenyls in fish muscle samples has been developed. The method is based on the microwave-assisted extraction (MAE) of food samples from an acetonitrile-water (95 + 5, v/v) mixture followed by SPE cleanup of the extracts and analysis by GC with an electron capture detector. MAE operational parameters, such as the extraction solvent, temperature, and time, were optimized with respect to the extraction efficiency of the target compounds from food samples with 10-13% fat content. The chosen extraction technique allows reduction of the solvent consumption and extraction time when compared with methods already used. Acetonitrile is a good extraction solvent for low-fat matrixes (2-20% fat content), such as fish samples, because it does not significantly dissolve the highly polar proteins, salts, and sugars commonly found in food and gives high recoveries of a wide polarity range of analytes. For purification, SPE using LC-Florisil was shown to be sufficient for the removal of coextracted substances. Recoveries > 78% with RSD values < 15% were obtained for all compounds under the selected conditions. Method quantification limits were in the 5-10 microg/kg range. The method was applied to the analysis of samples of herring (Clupea harengus) purchased at the local fish market. The method is rapid and reliable for the determination of organochlorine analytes in fish muscle.     

Determination of organophosphorus pesticides in soil by dispersive liquid-liquid microextraction and gas chromatography

In this article, a rapid and sensitive sample pretreatment technique for the determination of organophosphorus pesticides (OPPs) in soil samples is developed by using dispersive liquid-liquid microextraction (DLLME) combined with gas chromatography-flame photometric detection. Experimental conditions, including the kind of extraction and disperser solvent and their volumes, the extraction time, and the salt addition, are investigated, and the following experiment factors are used: 20 μL chlorobenzene as the extraction solvent; 1.0 mL acetonitrile as the disperser solvent; no addition of salt; and an extraction time of 1 min. Under the optimum conditions, the linearities for the three target OPPs (ethoprophos, chlorpyriphos, and profenofos) are obtained by five points in the concentration range of 2.5-1500 μg/kg, and three replicates are used for each point. Correlation coefficients vary from 0.9987 to 0.9997. The repeatability is tested by spiking soil samples at a concentration level of 5.0 μg/kg. The relative standard deviation (n = 3) varied between 2.0% and 6.6%. The limits of detection, based on a signal-to-noise ratio (S/N) of 3, range from 200 to 500 pg/g. This method is applied to the analysis of the spiked samples S1, S2, and S3, which are collected from the China Agriculture University's orchard, lawn, and garden, respectively. The recoveries for each target analyte are in the range between 87.9% and 108.0%, 87.4% and 108.0%, and 86.7% and 107.2%, respectively.     

Comparison of several extraction techniques for multiclass analysis of veterinary drugs in eggs using ultra-high pressure liquid chromatography-tandem mass spectrometry

This study compared four extraction methods for the simultaneous determination of tetracyclines, macrolides, quinolones, sulphonamides and anthelmintics (including benzimidazoles and avermectins) in eggs by ultra-high pressure liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS). Solvent extraction, solid-phase extraction (SPE), matrix solid-phase dispersion (MSPD) and modified QuEChERS procedure were compared in terms of recovery and number of veterinary drugs extracted. The solvent extraction procedure with a clean-up step provided better results than the other tested procedures. The QuEChERS procedure was simpler and faster, but extracted fewer compounds than solvent extraction. MSPD did not extract tetracyclines and quinolones, whereas macrolides and tetracyclines were not extracted when SPE was applied. The solvent extraction procedure was validated, obtaining recoveries ranging from 60% (sulfaquinoxaline) to 119% (levamisole) with repeatability values (expressed as relative standard deviations, RSDs) lower than 20% at two concentration levels (10 and 100 μg kg⁻¹), except for erythromycin, emamectin and ivermectin that showed RSD values close to 25% at 10 μg kg⁻¹. Limits of quantification (LOQs) were always equal or lower than 5 μg kg⁻¹. Finally the method was applied to egg samples, and erythromycin, enrofloxacin, difloxacin, thiabendazole, emamectin and fenbendazole were detected in four samples.     

Supramolecular microextraction of cobalt from water samples before its microsampling flame atomic absorption spectrometric detection

The supramolecular solvent system consists of tetrahydrofuran (THF) and 1-decanol, that was used as an extraction solvent for a microextraction procedure for the preconcentration and separation of Co(II). The proposed supramolecular-based procedure was combined with microsampling flame atomic absorption spectrometry for the determination of cobalt at trace levels in water samples. N-Benzoyl-N,N-diisobutylthiourea was used to chelate Co(II) in an aqueous solution. Quantitative extraction efficiency was obtained at pH 6.5. The effects of analytical parameters including pH, amount of ligand, type, ratio and volume of supramolecular solvent, sample volume and interfering ions were investigated for optimisation of the procedure. The proposed supramolecular solvent-based microextraction procedure (Ss-ME) exhibits a limit of detection (LOD) of 1.29 µg L^?1 and a limit of quantification (LOQ) of 3.88 µg L^?1. The procedure was validated by addition/recovery tests and by applying TMDA 64.2 and TMDA 53.3 water certified reference materials. The microextraction method was successfully applied for the preconcentration and determination of cobalt in water samples.     

Determination of Phenolics in Water and Arthrospira (Spirulina) platensis by Concentrated Sulfuric Acid and Ultrasound-Assisted Surfactant-Enhanced Emulsification Microextraction and High Performance Liquid Chromatography

A novel, practical, and environmentally friendly technique, termed concentrated sulfuric acid cleanup and ultrasound-assisted surfactant-enhanced emulsification microextraction (CSAC-UASEM), was combined with HPLC for the preconcentration and determination of five phenolics in water and Arthrospira (Spirulina) platensis samples. The main advantages include that the concentrated sulfuric acid is used to decrease macromolecular interferences prior to microextraction and, unlike dispersive liquid–liquid microextraction procedures, no dispersive organic solvent is required. Chloroform and sodium dodecyl sulfate were used as the extraction solvent and emulsifier, respectively. The algal cell preparation and CSAC-UASEM procedure parameters, including selection of cleanup method, ultrasound power, cell cytocylasis time, type and volume of extraction solvent, extraction temperature, ultrasound-extracted time, and sample pH, were optimized. At the fortification levels of 1.0 and 10.0 µg/L, the enrichment factors of analytes were in the range of 201.38 to 269.24. The percent extraction ranged from 71.57% to 107.42% in environmental Arthrospira-350, -793, and -834 samples, whereas the range was from 74.17% to 106.72% in water samples. The limits of detection (at S/N = 3) were 0.02 to 0.04 µg/L (except for 4-bromobisphenol A of 0.10 µg/L). These values indicate an approximately ten-fold improvement compared with the values reported by other techniques. In summary, the CSAC-UASEM sample preparation technique has great potential in the routine determination of trace phenolics in environmental waters and aquatic biological samples.     

Organic Compounds in High Alpine Snow

Abstract

Snow samples were taken in June 1995 at the Sonnblick Observatory located at the top of Mt. Sonn-blick (3106 m a.s.l.) in the main ridge of the Austrian Alps, as part of the project “Organic Aerosol Scavenging”. The main interest focused on the determination of aliphatic compounds and phenols. First the method for the extraction of the organic compounds was developed using standard samples prepared in the lab. The preconcentration of the samples was performed by liquid-liquid extraction with hexane and hexane/diethylether respectively. To characterize the analytical procedure, the efficiency of the extraction procedure, the reproducibility of the overall method and the detection limits were determined. Values for the recovery of the extraction method range from 57% (fatty acids) to 95% (aliphatic alcohols). Reproducibility was found to be between 3-5%, except for the fatty acids which gave a value of 16%. Detection limits were calculated for the various substances and are between 5μg/l (phenols) and 30μg/l (fatty acids). The analysis of the eight snow samples were performed using a GC-MS-FID system. The following compounds were identified as major compounds in the snow samples: 1-dodecanol, 1-tetradecanol, 1-hexadecanol, 1-octadecanol, 2-isobutyl-4-methoxy-phenol, diisobutylphenol and dibutylphthalate. The aliphatic alcohols are of biogenic origin and are present in a concentration range from 30 to 115 μg/l melted snow. The phenols show concentrations between 5 and 30 μg/l and the phthalates range up to 40 μg/l.     

分散液液微萃取-气相色谱/质谱法测定水中多环芳烃

用分散液液微萃取-气相色谱/质谱法测定水样中的16种多环芳烃(PAHs)。通过实验确定最佳萃取条件为:20μL四氯化碳作萃取剂,1.0 mL乙腈作分散剂,超声萃取1 min。在优化条件下,多环芳烃的富集倍数达到216～511,方法在0.05～50μg/L范围内呈良好的线性关系,相关系数(R2)在0.9873～0.9983之间,检出限为0.0020～0.14μg/L。相对标准偏差(RSD)在3.82%～12.45%(n=6)之间。该方法成功用于实际水样中痕量多环芳烃的测定。     

New procedure for the examination of the degradation of volatile organonitrogen compounds during the treatment of industrial effluents

We present a new procedure for the determination of 32 volatile organonitrogen compounds in samples of industrial effluents with a complex matrix. The procedure, based on dispersive liquid–liquid microextraction followed by gas chromatography with nitrogen‐phosphorus and mass spectrometric detection, was optimized and validated. Optimization of the extraction included the type of extraction and disperser solvent, disperser solvent volume, pH, salting out effect, extraction, and centrifugation time. The procedure based on nitrogen‐phosphorus detection was found to be superior, having lower limits of detection (0.0067–2.29 μg/mL) and quantitation as well as a wider linear range. The developed procedure was applied to the determination of content of volatile organonitrogen compounds in samples of raw effluents from the production of bitumens in which 13 compounds were identified at concentrations ranging from 0.15 to 10.86 μg/mL and in samples of effluents treated by various chemical methods.     

Determination of vitexin and isovitexin in pigeonpea using ultrasonic extraction followed by LC-MS

A method based on ultrasonic extraction (USE) followed by LC-MS is presented for the determination of vitexin and isovitexin in pigeonpea extracts in this study. The influential parameters of the USE procedure were optimized, and the optimal conditions were as follows: extraction solvent, 60% ethanol solution; liquid/solid ratio 10:1 (mL/g), extraction power, 250 W; temperature, 40-50 degrees C; and three extraction cycles, each cycle 15 min. Validation of the USE method was performed in terms of repeatability and reproducibility. RSDs for extraction yields were lower than 5.85 and 8.09%, respectively. The LOD and LOQ of chromatographic determination were 0.96 and 3.2 ng/mL for vitexin and 0.84 and 2.8 ng/mL for isovitexin. The method was also successfully applied for the determination of vitexin and isovitexin in stems, leaves, and root extracts of pigeonpea. From all these results, we may conclude that the developed method is appropriate for the quality control of pigeonpea and other plant extract products developed from pigeonpea.     

Development of ultrasound-assisted emulsification microextraction for the determination of seven pesticides in apple juice by gas chromatography–mass spectrometry

Α simple, relatively rapid, sensitive and cost-effective method based on ultrasound-assisted emulsification microextraction (USAEME) followed by gas chromatography coupled with mass spectrometry has been developed for the determination of seven endocrine disruptor pesticides (chlorpyrifos, deltamethrin, dimethoate, fenitrothion, malathion, pendimethalin and procymidone) in apple juice. This approach is based on the emulsification of organic extraction solvent in a diluted apple juice sample by ultrasound radiation and further separation of both liquids phases by centrifugation. The influence of the different parameters affecting the procedure (extraction solvent, extraction solvent volume, ultrasound time, centrifugation time, ionic strength and pH) was evaluated in order to optimise the efficiency of the extraction process. Target analytes were extracted from a 0.5 g apple juice sample that was diluted by 10 times with aqueous buffer solution (pH 7). The optimised USAEME procedure used 100 μL of chloroform as extraction solvent, 8 min of ultrasound extraction, ionic strength (2.5% w/v) and 7.5 min of centrifugation at 3800 rpm. The optimised method presented recoveries between 70 and 113% for the target analytes. Acceptable linearity for all target analytes was recorded with correlation coefficients (r) higher than 0.992. The limits of quantification were found between 1.1 and 4.6 μg kg^?1 ensuring compliance with the maximum residue limits established by the European Commission. The proposed method was applied for the determination of the endocrine disruptor pesticides in apple samples proving its suitability to the Commission Implementing Regulation (EU) no. 400/2014.