μL Of 1-octanol Research Articles

Fully Automated Electric-Field-Driven Liquid Phase Microextraction System with Renewable Organic Membrane As a Front End to High Performance Liquid Chromatography.

This article reports for the first time a programmable-flow-based mesofluidic platform that accommodates electric-field-driven liquid phase microextraction (μ-EME) in a fully automated mode. The miniaturized system is composed of a computer-controlled microsyringe pump and a multiposition rotary valve for handling aqueous and organic solutions at a low microliter volume and acts as a front-end to online liquid chromatographic separation. The organic membrane is automatically renewed and disposed of in every analytical cycle, thus minimizing analyte carry-over effects while avoiding analyst intervention. The proof-of-concept applicability of the automated mesofluidic device is demonstrated by the liquid chromatographic determination of nonsteriodal anti-inflammatory drugs in μ-EME processed complex samples (such as urine and influent wastewater) using online heart-cut approaches. Using 5 μL of 1-octanol, 7.5 μL of untreated sample and 7.5 μL of acceptor solution (25 mM NaOH), and 250 V for only 10 min in a stopped-flow mode, the extraction recoveries for the μ-EME of ibuprofen, ketoprofen, naproxen, and diclofenac exceed 40% in real samples. The flow-through system features moderately selective extraction regardless of the sample matrix constituents with repeatability values better than 13%.

Determination of fifteen phenols in wastewater from petroleum refinery samples using a dispersive liquid—liquid microextraction and liquid chromatography with a photodiode array detector

This work proposes for the first time a dispersive liquid-liquid microextraction (DLLME) method for the simultaneous extraction of 15 phenols (including isomers) from refinery wastewater with identification by liquid chromatography coupled to photodiode array detection (LC-PDA). The compounds studied were phenol, cresols, nitrophenols and chlorophenols including the isomers: 2–nitrophenol and 4-nitrophenol; o-cresol, m-cresol and p-cresol; 2,4-dichlorophenol and 2,6-dichlorophenol; 2,4,6-trichlorophenol and 2,4,5-trichlorophenol. Because of the presence of isomers and similar compounds, different mobile phases, comprising several combinations of methanol, acetonitrile and purified water, and different flow rates were tested to provide separation. Also, retention factors, selectivity and resolution were evaluated. For DLLME, volumes of extraction (1-octanol) and disperser (acetone) solvents were optimized by a 22 full factorial design. The optimum conditions involved using the use of 250 μL 1-octanol and 1000 μL of acetone. The limits of quantification were between 2.5 and 10 μg L−1. Analytical recoveries ranged from 69 to 129%, with relative standard deviations (RSD) below 20%. The proposed analytical method was successfully applied to the determination of these compounds in refinery wastewaters. Phenol, o-cresol p + m-cresol and 2,4-dimethylphenol were detected in a concentration range from 15 to 78 μg L−1 and 300–2120 μg L−1 in the treated and raw wastewaters, respectively.

Ionic Liquid-Assisted Liquid-Liquid Microextraction based on the Solidification of Floating Organic Droplet in Sample Preparation for Simultaneous Determination of Herbicide Residues in Fruits.

An ionic liquid-assisted liquid-liquid microextraction based on the solidification of floating organic droplet (ILSFODLLME) was investigated for analysis of four herbicide residues (i.e. simazine, atrazine, propazine, and linuron) by high performance liquid chromatography. For ILSFOD-LLME, the optimal extraction conditions were 5% w/v Na2SO4, 30 μL [C4MIM][PF6]RTIL, 100 μL of 1-octanol, ultrasonication time 30 s and centrifugation at 5000 rpm for 5 min. Under the optimal conditions, linearity was obtained within the range of 0.1-1000 μg kg-1, with the correlation coefficients greater than 0.999. The high enrichment factors of the target analytes were in the range of 64.5-139.9 and low limit of detection could be obtained. A modified QuEChERS was applied for fruit sample preparation before analysis. Matrix effects were also investigated using matrix matched standards for construction of the calibration graph. The proposed method has been successfully applied for extraction and preconcentration of herbicide residues in fruit samples, and good recoveries in the range of 87.32% to 99.93% were obtained.

Ultrasound-Assisted Surfactant-Enhanced Emulsification Micro-Extraction Followed by HPLC for Determination of Preservatives in Water, Beverages and Personal Care Products.

An ultrasound-assisted surfactant-enhanced emulsification micro-extraction (UASEME) procedure has been developed for pre-concentration of benzoic acid (BA) and paraben preservatives, including methylparaben, ethylparaben, propylparaben and butylparaben, prior to high-performance liquid chromatography-ultraviolet (HPLC-UV) analysis. Separations were performed on a Lichrospher RP-18 endcapped 5 µm, using an isocratic mobile phase of 40% acetonitile, at a flow rate of 1 mL min-1 The selected UASEME conditions comprised the use of 10 mL sample extract, 125 µL 1-octanol as extraction solvent and 0.05 mmol L-1 Tween 20 as emulsifier, 0.5% sodium chloride, ultrasonication time of 6 min and centrifugation time of 10 min. Method performance demonstrated wide linear range between 0.5 and 7,000 µg L-1 (R2>0.9903) and limits of detection between 0.03 and 10 µg L-1, which providing the enrichment factors of 15-184. The method precision (relative standard deviation) was <7%. The developed UASEME coupled with HPLC-UV has been successfully applied to determine four paraben preservatives in various sample matrices such as water, beverages and personal care products. The recoveries in the range of 70-138.1% were obtained. However, BA could not be determined in real sample extracts.

Fully Automated Headspace Bubble-in-Drop Microextraction.

A fully automated headspace bubble-in-drop microextraction (automated HS-BID) method, coupled to gas chromatography/mass spectrometric (GC/MS) analysis, was developed for the analysis of nitro musks in environmental water samples. The entire procedure, including the extraction of the analytes by HS-BID and GC/MS analysis of the analyte-enriched solvent, was completely automated. In BID, a certain volume of air is introduced into the extraction solvent droplet, enlarging the surface area of the extraction solvent droplet in relation to the water sample without increasing its volume, significantly enhancing extraction efficiency. Compared to conventional single drop microextraction, the developed method has higher extraction efficiency due to the enlarged surface area of the extraction solvent droplet. Under the optimized conditions (1.0 mL of sample solution, using 1.0 μL of 1-octanol containing of 0.5 μL of air bubble, at 40 °C for extraction for 20 min), the automated HS-BID gave low limits of detections (between 0.012 and 0.042 μg/L), good linearity (from 0.1 to 20 μg/L and from 0.2 to 50 μg/L, with r(2) between 0.9909 and 0.9958, depending on analytes), and good repeatability of the extractions (relative standard deviations, below 4.7%, n = 5). The developed procedure was applied to determine nitro musks in environmental water samples and was demonstrated to be efficient, labor-free, economical, and environmentally benign.

Cationic Micellar Precipitation for Simultaneous Preconcentration of Benzimidazole Anthelmintics in Milk Samples by High-Performance Liquid Chromatography

A method using micellar precipitation process using cationic surfactant cetyltrimethyl ammonium bromide at ambient temperature was investigated for simultaneous determination of benzimidazoles coupled with high-performance liquid chromatography (HPLC) analysis. The studied benzimidazoles was selected as model compounds including thiabendazole, albendazole, mebendazole, and fenbendazole. The experimental parameters affected the extraction efficiency, including the kind and concentration of salt, pH, concentration of CTAB, volume of 1-octanol, and the centrifugation extraction time, was optimized. The optimum extraction condition: 0.030 mol L -1 CTAB, 10% (m/v) NaCl, pH 4.0, 300 µL 1-octanol and centrifugation time 10 min. Under optimum conditions, enrichment factors of between 60 and 90 fold were obtained, leading to lower limit of detection in the range of 0.5-0.7 µg L -1 , depending on the analytes. The calibration range of the method was linear over the wide range of 0.5-1000 µg L -1 , with correlation coefficients more than 0.999. Finally, the proposed method was successfully applied in the analysis of benzimidazoles in milk samples.

Simultaneous Determination of Environmental Contaminants with Different Volatilities in Tap Water Samples Using a New Approach to Single-Drop Microextraction Procedure

A new single-drop microextraction approach is proposed for the extraction of compounds with a wide range of volatilities from tap water samples with separation/detection by gas chromatographymass spectrometry. This new microextraction mode is called direct immersion-headspace-single drop microextraction (DI-HS-SDME). Trihalomethanes (THMs), hydrocarbons with low molecular weight (benzene, ethyl benzene and xylenes) and polycyclic aromatic hydrocarbons (PAHs) were the model compounds. Ten milliliters of tap water samples and drop volume of 1.5 µL of 1-octanol were used. The optimal condition for DI-HS-SDME mode was 80 min of total extraction time (48 min at 40 °C in DI-SDME mode and 32 min at 12 °C in HS-SDME mode) and the addition of 1.2 g of NaCl. The analytical figures of merit were evaluated, the limits of detection ranged from 0.03 µg L-1 for o-xylene and ethyl benzene to 6 µg L-1 for THMs. The proposed method represents a promising alternative for the analysis of aqueous matrices which contain compounds with very different ranges of volatility.

Optimization of parameters for the alcoholic-assisted dispersive liquid–liquid microextraction of estrogens in water

Extraction and determination of estrogens in water samples were performed using alcoholic-assisted dispersive liquid–liquid microextraction (AA-DLLME) and high-performance liquid chromatography (UV/Vis detection). A Plackett–Burman design and a central composite design were applied to evaluate the AA-DLLME procedure. The effect of six parameters on extraction efficiency was investigated. The factors studied were volume of extraction and dispersive solvents, extraction time, pH, amount of salt and agitation rate. According to Plackett–Burman design results, the effective parameters were volume of extraction solvent and pH. Next, a central composite design was applied to obtain optimal condition. The optimized conditions were obtained at 220 μL 1-octanol as extraction solvent, 700 μL ethanol as dispersive solvent, pH 6 and 200 μL sample volume. Linearity was observed in the range of 1–500 μg L−1 for E2 and 0.1–100 μg L−1 for E1. Limits of detection were 0.1 μg L−1 for E2 and 0.01 μg L−1 for E1. The enrichment factors and extraction recoveries were 42.2, 46.4 and 80.4, 86.7, respectively. The relative standard deviations for determination of estrogens in water were in the range of 3.9–7.2 % (n = 3). The developed method was successfully applied for the determination of estrogens in environmental water samples.

Application of surfactant assisted dispersive liquid–liquid microextraction as an efficient sample treatment technique for preconcentration and trace detection of zonisamide and carbamazepine in urine and plasma samples

A simple, rapid, and efficient method, based on surfactant assisted dispersive liquid–liquid microextraction (SA-DLLME), followed by high performance liquid chromatography (HPLC) has been developed for simultaneous preconcentration and trace detection of zonisamide and carbamazepine in biological samples. A conventional cationic surfactant called cethyltrimethyl ammonium bromide (CTAB) was used as a disperser agent in the proposed approach. 1.5mL of CTAB (0.45mmolL−1) (disperser solvent) containing 50.0μL of 1-octanol (extraction solvent) was injected rapidly into the 7.0mL of water or diluted plasma or urine. A cloudy solution (water, 1-octanol, and CTAB) was formed in the test tube. After formation of cloudy solution, the mixture was centrifuged and 20μL of collected phase was injected into HPLC for subsequent analysis. Some parameters such as the type and volume of the extraction solvent, the type and concentration of surfactant, pH, ionic strength and centrifugation time were evaluated and optimized. Under optimum extraction conditions, the limits of detections (LODs) were 2.1 and 1.5μgL−1 (based on 3Sb/m) for urine samples, and 2.3 and 1.6μgL−1 for plasma samples. Linear dynamic range of 5–300 and 5–200μgL−1 were obtained for zonisamide and carbamazepine in all samples. Finally, the applicability of the proposed method was evaluated by extraction and determination of the drugs in urine and plasma samples.

Determination of bisphenol A in thermal printing papers treated by alkaline aqueous solution using the combination of single‐drop microextraction and HPLC

A method for the quantitative determination of bisphenol A in thermal printing paper was developed and validated. Bisphenol A was extracted from the paper samples using 2% NaOH solution, then the extracted analyte was enriched using single-drop microextraction followed by HPLC analysis. Several parameters relating to the single-drop microextraction efficiency including extraction solvent, extraction temperature and time, stirring rate, and pH of donor phase were studied and optimized. Spiked recovery of bisphenol A at 20 and 5 mg/g was found to be 95.8 and 108%, and the method detection limit and method quantification limit was 0.03 and 0.01 mg/g, respectively. Under the optimized conditions, the proposed method was applied to the determination of bisphenol A in seven types of thermal printing paper samples, and the concentration of bisphenol A was found in the range of 0.53-20.9 mg/g. The considerably minimum usage of organic solvents (5 μL 1-octanol) and high enrichment factor (189-197) in the sample preparation are the two highlighted advantages in comparison with previously published works.

Hollow-Fiber-Based LPME as a Reliable Sampling Method for Gas-Chromatographic Determination of Pharmacokinetic Parameters of Valproic Acid in Rat Plasma

A sensitive and simple method based on two-phase liquid-phase microextraction in porous hollow fiber followed by gas chromatography-flame ionization detection was developed for quantification and pharmacokinetic study of valproic acid (VPA, an antiepileptic drug) in rat plasma after oral administration of pure sodium valproate (25 mg kg−1). Some parameters such as type of organic solvent, pH of sample solution, stirring speed, salt addition, extraction time, and volume of sample that affected extraction efficiency of VPA were optimized. Under optimized microextraction conditions, VPA was extracted with 10 μL 1-octanol from 0.5 mL rat plasma previously diluted with 4.5 mL acidified and salinated water (pH 2) using 1-octanoic acid as internal standard. The limit of detection was 17 ng mL−1 with linear response over the concentration range of 50–10,000 ng mL−1 with correlation coefficient higher than 0.998. The developed method was successfully applied to determination of pharmacokinetic parameters such as tmax (peak time in concentration–time profile), Cmax (peak concentration in concentration–time profile), t1/2 (elimination half-life), AUC0–t (area under the curve for concentration versus time), clearance, and apparent distribution volume in rats following oral administration of VPA.

A new strategy to simultaneous microextraction of acidic and basic compounds

The simultaneous extraction of acidic and basic pollutants from water samples is an interesting and debatable work in sample preparation techniques. A novel and efficient method named ion pair based surfactant assisted microextraction (IP-SAME) was applied for extraction and preconcentration of five selected acidic and basic aromatic species as model compounds in water samples, followed by high performance liquid chromatography–ultraviolet detection. A mixture including 1 mL of ultra-pure water (containing ionic surfactant as emulsifier agent) and 60 μL 1-octanol (as extraction solvent) was rapidly injected using a syringe into a 10.0 mL water sample which formed an emulsified solution. IP-SAME mechanism can be interpreted by two types of molecular mass transfer into the organic solvent (partitioning and ion pairing for non-ionized and ionized compounds, respectively) during emulsification process. The effective parameters on the extraction efficiency such as the extraction solvent type and its volume, type of the surfactant and its concentration, sample pH and ionic strength of the sample were optimized. Under the optimum conditions (60 μL of 1-octanol; 1.5 mmol L −1 cethyltrimethyl ammonium bromide (CTAB) as emulsifier agent and sample pH 10.0), the preconcentration factors (PFs), detection limits and linear dynamic ranges (LDRs) were obtained in the range of 87–348, 0.07–0.6 μg L −1 and 0.1–200 μg L −1 respectively. All of natural water samples were successfully analyzed by the proposed method.

Immersed single-drop microextraction combined with gas chromatography for the determination of sufentanil and alfentanil in urine and wastewater samples

An immersed single-drop microextraction (SDME) method coupled with gas chromatography flame ionization detection (GC-FID) was developed for the extraction and determination of sufentanil and alfentanil. These drugs were extracted from 4 mL stirred sample solution (pH 10.0) into a microdrop of 1-octanol, containing impurity C of fentanyl as internal standard. After the extraction, the microdrop was withdrawn into the syringe and injected directly into a GC injection port. The parameters influencing the extraction efficiency including the nature of the extracting solvent, pH and ionic strength of the solution, stirring rate and extraction time were investigated. At the optimized condition, (1.5 µL 1-octanol as extracting solvent, stirring rate of 200 rpm, pH 10.0 and 30 min sampling time at room temperature, no salt addition), enrichment factors were 153 and 103 for sufentanil and alfentanil, respectively. Very good dynamic linear ranges (DLRs) were obtained in the range of 50 to 1000 ng mL−1 for sufentanil and 60 to 1000 ng mL−1 for alfentanil. Limits of detection (LODs) were 5 and 6 ng mL−1 for sufentanil and alfentanil, respectively. Relative standard deviations (RSD) for five replications of both drugs were found to be less than 9%. Finally, the method was successfully applied to the extraction and determination of the sufentanil and alfentanil in urine and wastewater samples.

Quantitation of atorvastatin in human plasma using directly suspended acceptor droplet in liquid–liquid–liquid microextraction and high-performance liquid chromatography-ultraviolet detection

A simple and sensitive methodology based on liquid–liquid–liquid microextraction (LLLME) followed by high-performance liquid chromatography-ultraviolet detection (HPLC-UV) has been successfully developed for the determination of atorvastatin (AT) in human plasma. AT was first extracted from 4.5 mL acidic aqueous sample (diluted plasma, donor phase, pH 1) at temperature 45 °C through 400 μL 1-octanol for 4.5 min, while being agitated by a stirring bar at 1250 rpm. Then, a 5.5 μL free suspended basic aqueous droplet (acceptor phase, pH 10) was delivered to the top-center position of the organic membrane. The mixture was stirred at 650 rpm for 7.5 min and the analyte was back-extracted into the droplet. Finally, the acceptor phase was taken into a microsyringe and injected directly into the HPLC. An enrichment factor of 187 along with substantial sample clean up was obtained under the optimized conditions. The calibration curve showed linearity in the range of 1–500 ng mL −1 with regression coefficient corresponding to 0.996. Limits of detection (S/N = 3) and quantification (S/N = 10) were 0.4 and 1 ng mL −1, respectively. A reasonable relative recovery (91%) and satisfactory intra-assay (4.4–7.0%, n = 6) and inter-assay (4.9–7.7%, n = 8) precision illustrated good performance of the analytical procedure. This technique was eventually applied for the determination of AT in human plasma after oral administration of 40 mg single dose of drug. The protocol proved to be highly cost-effective and reliable for the screening purpose.

Determination of thiophanate-methyl and chlorotoluron in water samples by improved single-drop microextraction coupled with high-performance liquid chromatography

An improved single-drop microextraction method for the determination of thiophanate-methyl and chlorotoluron in water samples was developed, with analysis by high-performance liquid chromatography-ultraviolet detection (HPLC-UV). Several parameters such as solvent type, salt concentration, stirring rate, extraction time, pH and organic drop volume were investigated. The optimum experimental conditions found were: 20 µL 1-octanol, 10% (w/v) NaCl, 600 rpm stirring rate, 40 min extraction time, neutral sample pH and 5 mL water sample. Under the optimum conditions, the enrichment factors were 45.3 and 107.0 folds for thiophanate-methyl and chlorotoluron, respectively. The method exhibited a wide linear range (1–100 µg L−1), reasonable detection limits (0.35 µg L−1) and suitable repeatability (RSD < 9.6%) for both analytes. The proposed method was validated with three real water samples fortified at two levels, and reasonable spiked recoveries were achieved in the range of 84.0% ∼ 110.3%. The experimental results indicated that the improved SDME was a simple, reliable and convenient technique and could easily be used for the enrichment of other pollutants.

Evaluation of liquid-phase microextraction conditions for determination of chlorophenols in environmental samples using gas chromatography–mass spectrometry without derivatization

Determination of trace chlorophenols (CPs) in environmental samples has been evaluated using liquid-phase microextraction (LPME) coupled with gas chromatography–mass spectrometry (GC–MS) without derivatization. The LPME procedure used to extract CPs from water involved 15 μL 1-octanol as acceptor solution in a 5.0 cm polypropylene hollow fiber with an inner diameter of 600 μm and a pore size of 0.2 μm. Under the optimal extraction conditions, enrichment factors from 117 to 220 are obtained. The obtained linear range is 1–100 ng mL −1 with r 2 = 0.9967 for 2,4-dichlorophenol (2,4-DCP); 1–100 ng mL −1 with r 2 = 0.9905 for 2,4,6-trichlorophenol (2,4,6-TCP); 5–500 ng mL −1 with r 2 = 0.9983 for 2,3,4,6-tetrachlorophenol (2,3,4,6-TeCP), and 10–1000 ng mL −1 with r 2 = 0.9929 for pentachlorophenol (PCP). The limits of detection range from 0.08 to 2 ng mL −1, which is comparable with the reported values (12–120 ng mL −1). Recoveries of CPs in various matrices exceed 85% with relative standard deviations of less than 10%, except for PCP in landfill leachate. The applicability of this method was examined to determine CPs in environmental samples by analyzing landfill leachate, ground water and soil. The 2,4-DCP and 2,4,6-TCP detected in the landfill leachate are 6.68 and 2.47 ng mL −1. The 2,4,6-TCP detected in ground water is 2.08 ng mL −1. All the studied CPs are detected in contaminated soil. The proposed method is simple, low-cost, less organic solvent used and can potentially be applied to analyze CPs in complex environmental matrices.

Solvent-modified solid-phase microextraction for the determination of diazepam in human plasma samples by capillary gas chromatography.

This paper describes microextraction and gas chromatographic analysis of diazepam from human plasma. The method was based on immobilisation of 1.5 microliters of 1-octanol on a polyacrylate-coated fiber designed for solid-phase microextraction. The solvent-modified fibre was used to extract diazepam from the samples. The plasma sample was pre-treated to release diazepam from the protein binding. The fibre was inserted into the modified plasma sample, adjusted to pH 5.5 an internal standard was added and the mixture was carefully stirred for 4 min. The fibre with the immobilised solvent and the enriched analytes was injected into the capillary gas chromatograph. The solvent and the extracted analytes were evaporated at 300 degrees C in the split-splitless injection port of the gas chromatograph, separated on a methylsilicon capillary column and detected with a nitrogen-phosphorus detector. The method was shown to be reproducible with a detection limit of 0.10 nmol/ml in human plasma.