Coupling Of Microextraction Research Articles

Micro-extraction, pre-concentration, and microfluidic-based separation of organophosphate insecticides followed by the miniaturized electrochemical detection system

Introduction: A new analytical method based on the coupling of microextraction and microfluidics was developed and investigated for the pre-concentration, separation, and electrochemical detection of fenitrothion (FT) and parathion (PA) at the sub-ppm concentrations. Method: In the first step, the microchip capillary electrophoresis technique was used to serve as a separation and detection system. Analytes were injected into the 40 mm long microchannel with 10 mm sidearms. Then, they were separated by applying a direct electrical field (+1800V) between buffer and detection reservoirs. 2-(n-morpholino)ethanesulfonic acid (MES) buffer (20 mM, pH 5) was used as the running buffer. The electrochemical detection was performed using three Pt microelectrodes with the width of working, counter, and reference electrodes (50, 250, and 250 µm, respectively) in the out channel approach. Results: The system was devised to have the optimum detection potential equal to -1.2 V vs. Pseudo Ref. electrode. The dimensions of the SU-8 channel have 20 µm depth and 50 µm width. In the second step, an air-assisted liquid-liquid microextraction technique was used for the extraction and preconcentration of analytes from human blood plasma. Then, 1, 2 di-bromoethan was used as extractant solvent, the analytes were preconcentrated, and the sedimented solvent (50 µL) was evaporated in a 60 ˚C water bath followed by substitution of running buffer containing 10% ethanol. The optimum extraction cycles were found 8 with adding 1% NaCl to the aqueous phase. Analyzing time of the mentioned analytes was less than 100s, and the precision range was 3.3 – 8.2 with the linear range of 0.8 – 100 ppm and 1.2 - 100 ppm for FT and PA, respectively. The extraction recoveries were about 91% and 87% for FT and PA, respectively. The detection limits for FT and PA were 240 and 360 ppb, respectively. Finally, the reliability of the method was investigated by GC-FID. Conclusion: The proposed method and device were validated and can be used as in situ and portable detection system for detecting fenitrothion and parathion insecticides.

Profiling Docetaxel in Plasma and Urine Samples from a Pediatric Cancer Patient Using Ultrasound-Assisted Dispersive Liquid-Liquid Microextraction Combined with LC-MS/MS.

In recent years, therapeutic drug monitoring (TDM) has been applied in docetaxel (DOC)-based anticancer therapy to precisely control various pharmacokinetic parameters, including the concentration of DOC in biofluids (e.g., plasma or urine), its clearance, and its area under the curve (AUC). The ability to determine these values and to monitor DOC levels in biological samples depends on the availability of precise and accurate analytical methods that both enable fast and sensitive analysis and can be implemented in routine clinical practice. This paper presents a new method for isolating DOC from plasma and urine samples based on the coupling of microextraction and advanced liquid chromatography with tandem mass spectrometry (LC-MS/MS). In the proposed method, biological samples are prepared via ultrasound-assisted dispersive liquid-liquid microextraction (UA-DLLME) using ethanol (EtOH) and chloroform (Chl) as the desorption and extraction solvents, respectively. The proposed protocol was fully validated according to the Food and Drug Administration (FDA) and the International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use (ICH) requirements. The developed method was then applied to monitor the DOC profile in plasma and urine samples collected from a pediatric patient suffering from cardiac angiosarcoma (AS) with metastasis to lungs and mediastinal lymph nodes, who was receiving treatment with DOC at a dose of 30 mg/m2 body surface area. Due to the rarity of this disease, TDM was carried out to determine the exact levels of DOC at particular time points to ascertain which levels were conducive to maximizing the treatment's effectiveness while minimizing the drug's toxicity. To this end, the concentration-time profiles of DOC in the plasma and urine samples were determined, and the levels of DOC at specific time intervals up to 3 days after administration were measured. The results showed that DOC was present at higher concentrations in the plasma than in the urine samples, which is due to the fact that this drug is primarily metabolized in the liver and then eliminated with the bile. The obtained data provided information about the pharmacokinetic profile of DOC in pediatric patients with cardiac AS, which enabled the dose to be adjusted to achieve the optimal therapeutic regimen. The findings of this work demonstrate that the optimized method can be applied for the routine monitoring of DOC levels in plasma and urine samples as a part of pharmacotherapy in oncological patients.

Rapid screening of polybrominated diphenyl ethers in water by solid-phase microextraction coupled with ultrahigh-resolution mass spectrometry.

Polybrominated diphenyl ethers (PBDEs) are considered emerging organic contaminants that attract more attention in the environment. Herein, online coupling of solid-phase microextraction and ultrahigh-resolution mass spectrometry was developed for rapid screening of eight PBDEs in water samples. This procedure was completed in 22min, about 6 times faster than the routine workflow such as solid-phase extraction coupled with gas chromatography-mass spectrometry. Thermal desorption and solvent-assisted atmospheric pressure chemical ionization were developed for the effective coupling of solid-phase microextraction (SPME) with ultrahigh-resolution mass spectrometry (UHRMS), which contributed to the signal enhancement and made the methodology feasible for environmental screening. The limits of detection and quantification were 0.01-0.50ng/mL and 0.05-4.00ng/mL, respectively. The recoveries were 57.2-75.2% for quality control samples at spiking levels of 0.8-10ng/mL (4-50ng/mL for BDE209), with relative standard deviation less than 19.0%. Twelve water samples from different river sites near industrial areas were screened using the developed method. The results showed that BDE-209 was the dominant PBDE (1.02-1.28ng/mL in positive samples), but its amount was lower than the human health ambient water quality criteria. Consequently, the developed method provides a rapid and reliable way of evaluating contamination status and risks of PBDEs in aqueous environment.

Online In-Tube Solid-Phase Microextraction Coupled with Liquid Chromatography-Tandem Mass Spectrometry for Automated Analysis of Four Sulfated Steroid Metabolites in Saliva Samples.

Accurate measurement of sulfated steroid metabolite concentrations can not only enable the elucidation of the mechanisms regulating steroid metabolism, but also lead to the diagnosis of various related diseases. The present study describes a simple and sensitive method for the simultaneous determination of four sulfated steroid metabolites in saliva, pregnenolone sulfate (PREGS), dehydroepiandrosterone sulfate (DHEAS), cortisol sulfate (CRTS), and 17β-estradiol-3-sulfate (E2S), by online coupling of in-tube solid-phase microextraction (IT-SPME) and stable isotope dilution liquid chromatography–tandem mass spectrometry (LC–MS/MS). These compounds were extracted and concentrated on Supel-Q PLOT capillary tubes by IT-SPME and separated and detected within 6 min by LC–MS/MS using an InertSustain swift C18 column and negative ion mode multiple reaction monitoring systems. These operations were fully automated by an online program. Calibration curves using their stable isotope-labeled internal standards showed good linearity in the range of 0.01–2 ng mL−1 for PREGS, DHEAS, and CRTS and of 0.05–10 ng mL−1 for E2S. The limits of detection (S/N = 3) of PREGS, DHEAS, CRTS, and E2S were 0.59, 0.30, 0.80, and 3.20 pg mL−1, respectively. Moreover, intraday and interday variations were lower than 11.1% (n = 5). The recoveries of these compounds from saliva samples were in the range of 86.6–112.9%. The developed method is highly sensitive and specific and can easily measure sulfated steroid metabolite concentrations in 50 μL saliva samples.

Metal Probe Microextraction Coupled to Dielectric Barrier Discharge Ionization-Mass Spectrometry for Detecting Drug Residues in Organisms.

In this study, a novel method for the direct coupling of metal probe microextraction (MPME) and a dielectric barrier discharge ionization (DBDI) source with mass spectrometry (MS) is reported. Analytes adsorbed on a tungsten needle were directly transferred to the DBDI source via rapid thermal desorption, which resulted in a limit of detection as low as 8 pg/mL. This is in part due to the "active capillary" configuration of the plasma ion source, where the efficiency of ion transfer to the MS is ∼100%. Specialty gases to maintain the plasma and carry analytes to the MS are not required. In contrast to direct one-step ionization of molecular adsorbates, the complete separation of the analyte desorption from the probe and the ionization event in our experimental setup greatly enhanced the sensitivity and detection reproducibility (RSD of 8.3%). We show detection of pyrimethamine, a first-line drug for the treatment and prevention of Plasmodium falciparum malaria all over the world, by this MPME/DBDI/MS method. The detection of drug residues in live fish and paramecium was achieved without the need for any sample pretreatment. The relative concentration of the drug in different organs of the fish was determined. This simple and convenient method has the potential for the analysis of chemicals even in single-cell organisms.

Analysis of volatile compound change in tuna oil during storage using a laser irradiation based HS-SPME-GC/MS

Tuna oil (TO) is susceptible to oxidation thus induce unpleasant flavor during storage. Herein, a novel and efficient laser irradiation desorption headspace solid-phase microextraction coupling gas chromatography-mass spectrometry method was developed for fast analysis of flavor change in TO at different storage periods. The data were statistically analyzed by multivariate statistical analyses, including principle component analysis (PCA) and orthogonal partial least-square analysis (OPLS-DA), which showed superb classification accuracy and validation (R2(X) = 0.915, Q2 = 0.834) and was further verified by permutation test. The variation of volatile compounds in TOs along with the extension of storage time was statistically analyzed to be significant (p < 0.05). Nonanal, heptanal, 2-octanone, and hexadecanoic acid, ethyl ester were regarded as the dominant indicators with significant effect on the data matrix. The LID-HS-SPME GC/MS technique could be employed as a front-line fast detect method to ensure the lipid quality.

Analysis of phenylcarboxylic acid-type microbial metabolites by microextraction by packed sorbent from blood serum followed by GC–MS detection

A method for analysis of 8 phenylcarboxylic acids in blood serum was developed based on the coupling of microextraction by packed sorbent, derivatization and GC–MS detection. These compounds are low molecular weight aromatic microbial metabolites that are proven and prospective indicators of sepsis in critically ill patients. Recoveries of the phenylcarboxylic acids from serum samples using microextraction by packed sorbent were 30–70%. The present method was linear (R2 ≥ 0.9981) over a clinically significant range of concentrations (94–2250 µg L−1/0.5–18 µM). The limits of quantification for the optimized method were 60–100 µg L−1/0.4–0.7 µM for phenylpropionic, phenyllactic, 4-hydroxybenzoic and 4-hydroxyphenylacetic acids, and 160 µg L−1/0.9–1.3 µM for benzoic, 4-hydroxyphenyllactic, homovanillic and 4-hydroxyphenylpropionic acids. The developed conditions were used to determine concentrations of the phenylcarboxylic acids in the most complicated matrix – serum samples of critically ill patients. Results were compared with liquid-liquid extraction and revealed a reduction in the time for sample preparation (45 min vs. 6 min) and serum (200 µL vs. 80 µL) volume. The combination of microextraction by packed sorbent and GC–MS methods, especially when fully automated could be a powerful tool for the clinical diagnosis of sepsis.

Switchable Hydrophilicity Dispersive Solvent-Based Liquid-Liquid Microextraction Coupling to High-Performance Liquid Chromatography for the Determination of Amphenicols in Food Products

Antibiotic residue has become a serious issue of food safety, due to the emergence of drug-resistant bacteria and their toxic side effects. Therefore, regarding the need, we herein report a rapid, sensitive, and selective switchable hydrophilicity dispersive solvent-based liquid-liquid microextraction (SHDS-LLME) method combined with high-performance liquid chromatography and UV detector for determining amphenicols in food products. In the off-line extraction procedure, the mixture of extraction solvent (butanol) and dispersive solvent (tetraethylenepentamine) was manually injected into the acidic aqueous sample solution. Specifically, after the fast neutralization reaction, the dispersive solvent was converted into water-soluble salt and phase separation was achieved. Under the optimal conditions, a good linearity was observed in the range of 0.27–50.0 μg kg−1. The limit of detection for chloramphenicol (CAP) and thiamphenicol (TAP) were 0.03 and 0.08 μg kg−1, respectively. Recoveries for the spiked samples obtained were between 81.5 and 113.5% and the relative standard deviation was less than 8.6%. The proposed method was successfully applied for the analysis of amphenicols in four food products.

Microwave-assisted dispersive liquid-liquid microextraction coupling to solidification of floating organic droplet for colorants analysis in selected cosmetics by liquid chromatography

A convenient and rapid method was developed for determination of fourteen colorants in selected cosmetics based on microwave-assisted dispersive liquid-liquid microextraction (MA-DLLME) using solidification of the floating organic droplet (SFOD) as a clean-up step followed by high-performance liquid chromatography diode array detection (HPLC-DAD). DLLME was performed in a microwave device for reducing manual operations and facilitating rapid extraction equilibrium, resulting in high sample throughput and good extraction efficiency. Matrix effects could be effectively eliminated by SFOD technique. Various parameters affecting the extraction efficiency were optimized by multi-response surface methodology. The limits of detection and quantification were 0.25–3.2 mg kg−1 and 0.85–11.0 mg kg−1, respectively. The recoveries ranged from 90.2% to 106.1% with relative standard deviations of 0.30–3.1%. The method was successfully applied to the analysis of cosmetics, in which all the colorants could be quantified, and their median values ranged from 4.94 to 591 mg kg−1 for seventy-two lipsticks, and from 7.70 to 1.73 × 103 mg kg−1 for fifty eye shadows, respectively. The proposed protocol could achieve batch preparation of samples and avoid measurement errors from the obvious volume reduction of the recovered extract, and it could serve as a powerful tool for high-throughput analysis of multiple colorants in complex samples.

Determination of four salicylic acids in aloe by in vivo solid phase microextraction coupling with liquid chromatography-photodiode array detection

In recent years, great concerns have been raised about salicylic acid (SA) and its derivatives as plant regulators. Therefore, precise determination of the distribution of SAs in the living plants is necessary for not only fundamental researches but also the regulating mechanisms. In this study, a custom-made solid phase microextraction (SPME) fiber based on diallyl dimethyl ammonium chloride-assembled graphene oxide-coated C18 composite (C18@GO@PDDA) was proposed for in vivo detection of salicylic acid, acetylsalicylic acid (ASA), 4-methyl salicylic acid（4-SA）and 3-methyl salicylic acid (3-SA) in aloe plants. Under the optimized conditions, the analytical performance evaluated in homogenized aloe plant tissues exhibited low detection limits (1.8–2.8 μg g−1), wide linear ranges (10–5000 μg g−1), and satisfactory reproducibility (relative standard deviations less than 8.4% and 9.3% for inter-fiber and intra-fiber assays, respectively). Under cadmium stress, the developed method was applied for the in vivo tracing of four salicylic acids in aloe plants. A 48-h in vivo tracing revealed that salicylic acids were involved in the pathway of cadmium stress tolerance. To our best knowledge, it is the first effort to realize the in vivo analysis of SA and its derivatives in plants, and it has a made a great step forward in the area of plant hormone analysis.

Rapid detection of five anesthetics in tilapias by in vivo solid phase microextraction coupling with gas chromatography-mass spectrometry

The concentration of five rapidly metabolized anesthetics in living tilapias was determined in this study, by the presented method coupling in vivo solid phase microextraction (SPME) to gas chromatography-mass spectrometry (GC-MS), which was the first time that in vivo sampling method was adapted in detecting the anesthetic residue in the living aquatic product. The analytical performance of the developed method was evaluated in homogenized tilapia dorsal muscle, and the results demonstrated that the present method possessed low detection limits 1.7–9.4ngg−1), wide linear ranges (10 or 30–5000ngg−1), and satisfactory reproducibility (relative standard deviations no more than 8.1% and 10.8% for inter-fiber and intra-fiber assays, respectively). Standard curves were established in homogenized tilapia dorsal muscle for calibrating in vivo SPME in living tilapias. And the concentrations determined by in vivo SPME were close to those determined by the liquid extraction. By using the present method, one anesthetic residue was detected above the detection limit in tilapias from the local markets. Comparing to traditional methods, the present one exhibited superior time-efficiency and cost performance, as the extraction time was only ten minutes, which was short to successfully avoid the possible loss of analytes caused by elimination and sample storage. In addition, owing to the time-efficiency of the present method, the elimination of the anesthetics in tilapias was traced successfully in the laboratory.

Slug-flow microextraction coupled with paper spray mass spectrometry for rapid analysis of complex samples

Analysis of trace compounds in small-volume complex samples is of importance for forensic, clinical, pharmaceutical, environmental, and life science investigation. In this study, we reported the coupling of slug-flow microextraction with paper spray mass spectrometry for rapid analysis of trace analytes in small volume of complicated biological samples such as whole blood, milk, and body fluid, etc. The method is performed by applying a disposable glass capillary for rapid extraction of a small amount of complex samples using a small amount of organic solvent; the loaded organic solvent was then spotted onto a paper triangle and dried out; subsequently, a high voltage and some spray solvent were applied onto the paper triangle for mass spectrometric analysis. By using the proposed method, high sensitivity and satisfactory precision for quantitative analysis of trace macrolide antibiotics in whole bloods and milks as well as perfluorinated compounds in individual small organisms have been successfully achieved. In addition, investigation of bioaccumulation of perfluorinated compounds in individual small organisms has been reached.

Use of microextraction by packed sorbent directly coupled to an electron ionization single quadrupole mass spectrometer as an alternative for non-separative determinations.

Sometimes it is not necessary to separate the individual compounds of a sample to resolve an analytical problem, it is enough to obtain a signal profile of the sample formed by all the components integrating it. Within this strategy, electronic noses based on the direct coupling of a headspace sampler with a mass spectrometer (HS-MS) have been proposed. Nevertheless, this coupling is not suitable for the analysis of non-volatile compounds. In order to propose an alternative to HS-MS determinations for non-volatile compounds, here we present the first 'proof of concept' use of the direct coupling of microextraction by packed sorbents (MEPS) to a mass spectrometer device using an electron ionization (EI) and a single quadrupole as ionization source and analyzer, respectively. As target compounds, a set of analytes with different physic-chemical properties were evaluated (2-ethyl-1-hexanol, styrene, 2-heptanone, among others). The use of MEPS extraction present many advantages, such as it is fast, simple, easy to automate and requires small volumes of sample and organic solvents. Moreover, MEPS cartridges are re-usable as samples can be extracted more than 100 times using the same syringe. In order to introduce into the system all the elution volume from the MEPS extraction, a programmable temperature vaporizer (PTV) is proposed as the injector device. Results obtained with the proposed methodology (MEPS-PTV/MS) were compared with the ones obtained based on the separative scheme, i.e. using gas chromatography separation (MEPS-PTV-GC/MS), and both methods provided similar results. Limits of detection were found to be between 3.26 and 146.6μgL-1 in the non-separative scheme and between 0.02 and 1.72μgL-1 when the separative methodology was used. Repeatability and reproducibility were evaluated with values below 17% in all cases.

On-line coupling of Micro-Extraction by Packed Sorbent with Sequential Injection Chromatography system for direct extraction and determination of betaxolol in human urine

A novel approach for automation of Micro-Extraction by Packed Sorbent (MEPS), a solid phase extraction technique, is presented, enabling precise and repeatable liquid handling due to the employment of sequential injection technique. The developed system was used for human urine sample clean-up and pre-concentration of betaxolol before its separation and determination. A commercial MEPS C-18 cartridge was integrated into an SIChrom™ system. The chromatographic separation was performed on a monolithic High Resolution C18 (50×4.6mm) column which was coupled on-line in the system with Micro-Extraction using an additional selection valve. A mixture of acetonitrile and aqueous solution of 0.5% triethylamine with acetic acid, pH adjusted to 4.5 in ratio 30:70 was used as a mobile phase for elution of betaxolol from MEPS directly onto the monolithic column where the separation took place. Betaxolol was quantified by a fluorescence detector at wavelengths λex=220nm and λem=305nm. The linear calibration range of 5–400ngmL−1, with limit of detection 1.5ngmL−1 and limit of quantification 5ngmL−1 and correlation r=0.9998 for both the standard and urine matrix calibration were achieved. The system recovery was 105±5%; 100±4%; 108±1% for three concentration levels of betaxolol in 10 times diluted urine – 5, 20 and 200ng mL−1, respectively.

Vortex-Assisted Hollow-Fiber Liquid-Phase Microextraction Coupled with High Performance Liquid Chromatography for the Determination of Three Synthetic Endocrine Disrupting Compounds in Milk

In this study, a vortex-assisted three-phase hollow fiber liquid-phase microextraction (VA-HF-LPME) coupling with high performance liquid chromatography (HPLC) method was developed for determination of three synthetic endocrine disrupting compounds[EDCs, bisphenol-A (BPA), bisphenol-AF (BPAF) and tetrabromobisphenol-A (TBBPA)] in milk samples. Vortex provided effective and mild mixing of the sample solution and increased the contact between analytes and boundary layers of the hollow fibre, thereby enhancing mass transfer rate and leading to high extraction efficiency of the target analytes. The influencing parameters of VA-HF-LPME sample preparation method, such as organic solvents (acceptor phase), pH of sample solution (donor phase), sample volume, concentration of NaOH, extraction time, and ionic strength were systematically optimized. The instrumental calibration curves of BPA, BPAF and TBBPA show good linear relations (R2 > 0.9988) in the concentration range of 0.5-200, 0.5-200 and 1.0-250 µg L-1, respectively. The relative standard deviations (RSD, n = 5) were 1.3-3.7%. The limits of detection (LOD, S/N = 3) were in the range of 0.16-0.35 µg L-1 and the limits of quantification (LOQ, S/N = 10) were in the range of 0.51-1.12 µg L-1. The proposed method was successfully applied to the extraction of EDCs in milk samples.

中空纤维膜液相微萃取–气相色谱法测定水中有机氯农药的研究

建立中空纤维膜液相微萃取–气相色谱测定水中有机氯农药的新方法。研究了萃取体系、萃取时间、萃取温度、溶液pH值、搅拌速度等因素对萃取效率的影响，确定中空纤维膜液相微萃取的最佳条件：以正己烷/甲苯为萃取剂，萃取时间为20 min，萃取温度为40℃，搅拌速度为500 r/mim，pH值为中性。在最优条件下，对实际水样进行分析检测，α-666、β-666、γ-666、δ-666、P,p’-DDE、P,p’-DDD、o,p’-DDT、P,p’-DDT的加标回收率分别为101.1%、56.7%、60.3%、67.0%、135.1%、83.1%、121.7%和74.3%，表明这种方法对水中α-666、P,p’-DDT和P,p’-DDE有很好的检出效果。The determination method for organo-chlorine pesticide in water using hollow fiber membrane liquid microextraction coupling with gas phase chromatography was developed. The effects of extracting system, extraction time, pH value, mixing speed and extraction temperature on recovery of organo-chlorine pesticide in water were investigated and the optimum extraction conditions were gained and listed as follows: using n-hexane/toluene as organic extractant, extraction time of 20 min, extraction temperature of 40℃, mixing speed of 500 rpm, neutral solution. Under the optimum conditions, the recovery rates of α-666, β-666, γ-666, δ-666, P,p’-DDE, P,p’-DDD, o,p’-DDT, P,p’-DDT in actual sample were 101.1%, 56.7%, 60.3%, 67.0%, 135.1%, 83.1%, 121.7% and 74.3%, respectively. The results showed that this method is feasible for P,p’-DDT, α-666 and P,p’-DDE determination in water.

Multiresidue analysis of organic pollutants by in-tube solid phase microextraction coupled to ultra-high performance liquid chromatography–electrospray-tandem mass spectrometry

In this work, in-tube solid phase microextraction (IT-SPME) coupling with ultra-high-pressure liquid chromatography tandem mass spectrometry (UHPLC–MS/MS) multiresidue analytical method has been proposed for the first time for on-line enrichment of 9 analytes included in Water Frame Directive 2000/60/EC (WFD). The device was equipped with a GC TRB-5 capillary column, used as pre-concentration loop, and two conventional six-port injection valves. Water sample and desorption solvent volumes were tested. The optimum conditions were 4mL of processed sample followed by elution with 40μL of methanol. The analytes were detected with a mass spectrometer after being ionized positively using an electrospray ionization (ESI) source. The method presents good linearity over the range assayed, 0.025–2.5μg/L for chlorpyriphos and 0.25–25μg/L for the other tested compounds and LODs between 0.025μg/L and 2.5μg/L. Enrichment factors ranged from 2.5 to 10. Intra and inter-day variation coefficients were <26 and 31.6% respectively. Once validated, the method was applied to several water samples from different sources demonstrating that it achieves the on-line enrichment of the analytes with the advantage of minimum sample manipulation, and the identification and quantification of some organic pollutants in water samples in the range of low parts-per-billion. The method provided similar analytical characteristics as those obtained in the established couple IT-SPME–Capillary Liquid Chromatography (CapLC).

A poly (4‐vinylpridine‐co‐ethylene glycol dimethacrylate) monolithic concentrator for in‐line concentration‐capillary electrophoresis analysis of phenols in water samples

A poly(4-vinylpridine-co-ethylene glycol dimethacrylate) monolith was synthesized in a capillary and constructed as a concentrator for the in-line polymeric monolith microextraction coupling with capillary electrophoresis. The integrated system was then used for the simultaneous determination of five trace phenols (2-nitrophenol, 3-nitrophenol, 4-nitrophenol, 2-chlorophenol, and 2,4-dichlorophenol) in water samples. The experimental parameters for in-line solid-phase extraction, such as composition and volume of the elution plug, pH of sample solution, and the time for sample loading were optimized. The sensitivity for the mixture of phenols (2-nitrophenol, 3-nitrophenol, 4-nitrophenol, 2-chlorophenol, and 2,4-dichlorophenol) enhanced to 615-2222 folds at the optimum condition was compared to the sensitivity for a normal hydrodynamic injection in capillary electrophoresis. Linearity ranged from concentration of 10-500 ng mL(-1) (R(2) > 0.999) for all five phenols with the detection limits of 1.3-3.3 ng mL(-1) . In tap, snow and Yangtze River water spiked with 20 ng mL(-1) and 200 ng mL(-1) , respectively, the recoveries of 84-105% were obtained. It has been demonstrated that this work has great potential for the analysis of phenols in genuine water samples.

Coupling of microextraction by packed sorbents with gas chromatography with ionic liquid stationary phases for the determination of haloanisoles in wines

A new method based on the coupling of microextraction by packed sorbents (MEPS) and gas chromatography with ionic liquid stationary phases for the determination of four haloanisoles in wine matrices is proposed. The analytes were concentrated in a C18 barrel insert and needle (BIN), desorbed with a small volume of an organic solvent, and determined by gas chromatography with electron-capture detection (GC–μECD). The influence of several factors on the efficiency of extraction, washing and elution steps was investigated. Additionally, ionic liquid stationary phases of very different polarities were evaluated in terms of efficiency. Under optimized conditions, the analytes were first extracted in the sorbent material and, after an adequate washing step, eluted with 50μL of ethanol. An aliquot of 5μL of this extract was further injected, using a programmed temperature vaporizer (PTV), into the chromatographic system. The yield of the overall procedure ranged from 48 to 60%; the reproducibility of the method, calculated as the relative standard deviation (RSD), was below 10% for all compounds, and the limits of detection ranged from 1.2 to 4.8ngL−1. External calibration was used in the determination of the target compounds in wine samples.

Highly sensitive analysis of substituted aniline compounds in water samples by using oxidized multiwalled carbon nanotubes as an in-tube solid-phase microextraction medium

An automated on-line method for the determination of the substituted aniline compounds was developed using in-tube solid-phase microextraction coupling to high-performance liquid chromatography (HPLC). In this work, oxidized multiwalled carbon nanotubes (MWCNTs-COOH) coated on the outer surface of the fused-silica tube and inserted in the polyether ether ketone (PEEK) tubing, which was fixed directly on the six-port injection valve to substitute for the sample loop. The extraction procedure was performed by a constant flow pump frequently driving the sample solution through the PEEK tubing and the analytes were adsorbed onto MWCNTs-COOH materials when the six-port valve set to load position. After extraction, the valve switched to inject position and the extracted analytes were desorbed by mobile phase in dynamic mode. High extraction capacity was achieved for the investigated analytes and great improvement of the limits of detection was obtained in comparison with other methods. The calibration plots were linear ( r 2 ≥ 0.9949) over the concentration range of 1.04–104 ng mL −1 for 4-nitroaniline, 1.02–102 ng mL −1 for 2-nitroaniline, 1.68–168 ng mL −1 for 2-chloroaniline and 1.09–109 ng mL −1 for 2,4-dichloroaniline. The detection limit ranged from 0.04 ng mL −1 to 0.13 ng mL −1 (at S/N = 3). The possibility of applying the established method to water samples analysis was also studied.