Solvent-free Extraction Research Articles

SPME Fibers for the Analysis of Pesticide Residues in Fruits and Vegetables: A Review

Food samples are usually analyzed with a preliminary step of sample preparation, because pesticide residues are present in low concentrations and embedded in complex matrixes. Solid phase microextraction (SPME) is a solvent-free extraction technique that is fast, relatively inexpensive, easily automated, and versatile with high sample throughput. Analyte extraction, pre-concentration, and introduction into the analytical instrument are achieved in a single uninterrupted process. SPME uses fibers coated with a polymeric stationary phase that can be either a solid, liquid, or a combination of both. The fiber coating extracts the target analytes from a complex food matrix by absorption in the case of liquid coatings or adsorption in the case of solid coatings. The SPME fiber is then transferred into the analytical instrument for desorption and analysis of the target analytes. The use of sol-gel technology in the production SPME coated fiber has helped to increase the range of pesticide residues that can be extracted with the SPME technique.

“Solvent-free” ultrasound-assisted extraction of lipids from fresh microalgae cells: A green, clean and scalable process

In order to comply with criteria of green chemistry concepts and sustainability, a new procedure has been performed for solvent-free ultrasound-assisted extraction (UAE) to extract lipids from fresh Nannochloropsis oculata biomass. Through response surface methodology (RSM) parameters affecting the oil recovery were optimized. Optimum conditions for oil extraction were estimated as follows: (i) 1000W ultrasonic power, (ii) 30min extraction time and (iii) biomass dry weight content at 5%. Yields were calculated by the total fatty acids methyl esters amounts analyzed by GC–FID–MS. The maximum oil recovery was around 0.21%. This value was compared with the one obtained with the conventional extraction method (Bligh and Dyer). Furthermore, effect of temperature on the yield was also investigated. The overall results show an innovative and effective extraction method adapted for microalgae oil recovery, without using solvent and with an enable scaling up.

Trace level arsenic quantification through cloud point extraction: application to biological and environmental samples.

A sensitive solvent-free extraction protocol for the quantification of arsenic at trace level has been described. It is based on the reaction of arsenic (V) with molybdate in acidic medium in presence of antimony (III) and ascorbic acid as a reducing agent to form a blue-colored arsenomolybdenum blue complex. The complex has been extracted into surfactant phase using Triton X-114, and its absorbance was measured at 690 nm. The detection limit, working range, and the relative standard deviation were found to be 1 ng mL−1, 10–200 ng mL−1, and 1.2%, respectively. The effect of common ions was studied, and the method has been applied to determine trace levels of As(III) and As(V) from a variety of samples like environmental, biological, and commercially procured chemicals.

Occurrence of aflatoxin M1 in Italian cheese: Results of a survey conducted in 2010 and correlation with manufacturing, production season, milking animals, and maturation of cheese

Aflatoxin M1 (AFM1), a carcinogenic metabolite secreted into milk by animals fed with crops contaminated by aflatoxin B1, can be found in dairy products because of its relative stability to treatments used to produce foodstuffs, and also to long-term storage. Maximum admissible limits of AFM1 in milk have been set up worldwides; specific regulations regarding dairy products have also been established in some countries. Nevertheless, little and rather discordant data on the occurrence of such a contaminant in cheese and other dairy products is available, and mainly in those countries which are important producers and consumers of cheese, such as, for example, Italy. Therefore, a one-year survey was conducted by measuring AFM1 contamination in cheese purchased on the Italian market. More than a hundred samples representing the highest variability in terms of type of cheese, origin, cheese-making process, and maturation were collected and analysed through a previously described ELISA method coupled to a very rapid, simple and solvent-free extraction. More than 83% of samples showed detectable levels of AFM1 (>25 ng kg−1); most of them were found to be contaminated at a level between 50 and 150 ng kg−1. The measured AFM1 concentration was correlated to four factors which were presumed to influence the contamination level: manufacturing, production season, milking animal, and maturation. Statistical analyses demonstrated that milking animals and manufacturing affect AFM1 concentrations, as cheeses obtained from cows’ milk and from artisanal production are more contaminated than cheeses produced with milk belonging to other animals and in industrial contexts. The others two factors showed statistically non-significant differences between groups.

Determination of venlafaxine in post-mortem whole blood by HS-SPME and GC-NPD

Venlafaxine is a phenethylamine derivative widely prescribed for the treatment of depression which inhibits both serotonin and norepinephrine reuptake (SNRI). In treatment with antidepressants of patient with depression and other psychiatric disorders there is also increased risk of suicidal thought and behaviour. Several lethal intoxications involving venlafaxine usually among psychotic patients have been reported in the literature. Sample preparation is of the greatest significance for a successful toxicological analysis. The development of simple, effective and rapid extraction procedures of drugs from post-mortem biological samples is a challenge. Headspace-solid phase microextraction (HS-SPME) offers significant advantages such as simplicity, low cost, compatibility with analytical systems, automation and solvent-free extraction. The aim of our work was the optimization of a HS-SPME procedure for the determination of venlafaxine in post-mortem biological samples by gas chromatography (GC) with nitrogen-phosphorous detection (NPD). Venlafaxine was extracted on 100 μm Polydimethylsiloxone Coating-Red (PDMS) SPME fiber and determined by GC-NPD. Salt addition, extraction temperature, preheating and extraction time were optimized to enhance the recovery of the extraction from aqueous solution spiked with venlafaxine. Finally the developed procedure was applied to post-mortem biological samples of a fatally poisoned woman by venlafaxine. The drug was quantified in post-mortem blood gastric and oesophagus contents of the deceased woman. A simple and rapid procedure using HS-SPME was developed for sample preparation of venlafaxine in post-mortem biological samples prior to GC-NPD determination. Validation data was satisfactory, thus enabling application in the toxicological analysis of forensic samples.

Solvent-free microwave-assisted extraction of fluoroquinolones from soil and liquid chromatography-fluorescence determination

Presented hereafter is a novel method entailing solvent free microwave-assisted extraction (MAE) and HPLC equipped with Fluorimetric Detector (HPLC-FD) for the simultaneous determination at μg kg −1 concentration of eight fluoroquinolone antibiotics (FQs) (Ciprofloxacin, Danofloxacin, Enrofloxacin, Flerofloxacin, Levofloxacin, Marbofloxacin, Norfloxacin and Orbifloxacin) in agricultural soils. The extraction was quantitatively performed, in a single step, by using an aqueous solution containing Mg(II) as complexing agent, thus avoiding consumption of organic solvents. The optimal MAE conditions have been established through a chemometric approach by considering temperature, irradiation time and matrix moisture or solvent, as the most important recognized variables affecting the extraction yield. Satisfying recoveries (69–110%, spikes 0.03–0.5 mg kg −1) were gained with a single MAE cycle of 20 min, at 80 °C in 20% (w/v) Mg(NO 3) 2 solution as leaching agent. MAE-SPE recoveries at 10 μg kg −1, concentration near method quantification limits (MQLs), were in the range 60–85%. Good repeatability and within-lab reproducibility were observed (both in the range 1–16%). The applicability of the method to real samples was assessed on natural contaminated soils. Compared to ultrasonic-assisted extraction (UAE), MAE was shown to be highly competitive in terms of extraction efficacy and analysis speed.

Novel pepper extract for enhanced P-glycoprotein inhibition

Abstract Objectives Piperine is one of the most promising bioenhancers to date. Methods used for its extraction suffer from drawbacks such as use of organic solvents, poor extraction efficiency, tedious and expensive methodology. These methods are not encouraged with a view to reducing global warming. The objective was therefore to develop an alternative solvent-free extraction method. Methods An aqueous extract of long pepper fruits was prepared using hydrophilic lipid Gelucire 44/14 as the extracting aid and this was compared with an alcoholic extract. Extracts were characterized using high-performance thin layer chromatography and differential scanning calorimetry. P-glycoprotein (P-gp) inhibitory activity of the aqueous and alcoholic extracts and pure piperine was compared using an in-vitro everted rat intestinal model using ornidazole as the model drug. The study was performed using two oral pretreatment dose levels (10 and 20 mg/kg) and durations (1 and 3 days). Exsorption of ornidazole from serosal to mucosal surface was monitored. Key findings P-gp inhibitory activity of the aqueous extract was comparable with that of pure piperine (P > 0.05) and was significantly higher than the alcoholic extract (P < 0.05). Pure piperine and the aqueous extract exhibited significant P-gp inhibitory activity compared with control, which was irrespective of oral pretreatment dose and duration levels. No significant effect of oral pretreatment duration of the aqueous extract was observed. The observed enhancement in P-gp inhibitory activity of the aqueous extract may have been attributed to the P-gp inhibitory potential of Gelucire 44/14 and its efficient extraction and solubility enhancement ability. Conclusions In the field of phytopharmaceuticals efficient and eco-friendly extraction processes are still a goal to be achieved. Extraction with Gelucire 44/14 could be a potential method of extraction for phytopharmaceuticals. Compared with conventional methods of extraction it is more efficient, easier to prepare, eco-friendly and scalable.

Nootropic activity of lipid-based extract of Bacopa monniera Linn. compared with traditional preparation and extracts

Abstract Objectives The aim was to design an alternative solvent-free extraction method using the hydrophilic lipid Gelucire (polyethylene glycol glycerides) for herbal extraction and to confirm the efficacy of extraction using biological screening. Methods Bacopa monniera Linn. (BM) was selected for the study. Conventional methanolic extract (MEBM), Ayurvedic ghrita (AGBM) and lipid extracts (LEBM) were prepared and standardised by high-performance thin-layer chromatography (HPTLC). Nootropic activity in rats was evaluated using the two-trial Y-maze test and the anterograde amnesia induced by scopolamine (1 mg/kg i.p.) determined by the conditioned avoidance response. The extracts were administered daily at doses of 100, 200 and 400 mg/kg orally. At the end of the conditioned avoidance response test, brain monoamine levels were estimated by HPLC. Key findings The LEBM, MEBM and AGBM contained 3.56%, 4.10% and 0.005% bacoside A, respectively. Significantly greater spatial recognition was observed with LEBM (P < 0.001 at 400 and 200 mg/kg) and MEBM (P < 0.001 at 400 mg/kg, P < 0.01 at 200 mg/kg) than AGBM. The conditioned avoidance response was significantly higher in the groups treated with high doses of LEBM and MEBM than AGBM. There were significant decreases in brain noradrenaline (P < 0.001) and 5-hydroxytryptamine (P < 0.01) levels and an increase in dopamine levels (P < 0.05) in the LEBM-treated groups compared with the stress control group. Conclusions The proposed LEBM is solvent free, does not have the shortcomings associated with conventional extraction, and had comparable nootropic activity to the MEBM.

Nootropic activity of lipid-based extract of <I>Bacopa monniera</I> Linn. compared with traditional preparation and extracts

The aim was to design an alternative solvent-free extraction method using the hydrophilic lipid Gelucire (polyethylene glycol glycerides) for herbal extraction and to confirm the efficacy of extraction using biological screening. Bacopa monniera Linn. (BM) was selected for the study. Conventional methanolic extract (MEBM), Ayurvedic ghrita (AGBM) and lipid extracts (LEBM) were prepared and standardised by high-performance thin-layer chromatography (HPTLC). Nootropic activity in rats was evaluated using the two-trial Y-maze test and the anterograde amnesia induced by scopolamine (1 mg/kg i.p.) determined by the conditioned avoidance response. The extracts were administered daily at doses of 100, 200 and 400 mg/kg orally. At the end of the conditioned avoidance response test, brain monoamine levels were estimated by HPLC. The LEBM, MEBM and AGBM contained 3.56%, 4.10% and 0.005% bacoside A, respectively. Significantly greater spatial recognition was observed with LEBM (P < 0.001 at 400 and 200 mg/kg) and MEBM (P < 0.001 at 400 mg/kg, P < 0.01 at 200 mg/kg) than AGBM. The conditioned avoidance response was significantly higher in the groups treated with high doses of LEBM and MEBM than AGBM. There were significant decreases in brain noradrenaline (P < 0.001) and 5-hydroxytryptamine (P < 0.01) levels and an increase in dopamine levels (P < 0.05) in the LEBM-treated groups compared with the stress control group. The proposed LEBM is solvent free, does not have the shortcomings associated with conventional extraction, and had comparable nootropic activity to the MEBM.

Novel pepper extract for enhanced P-glycoprotein inhibition

Piperine is one of the most promising bioenhancers to date. Methods used for its extraction suffer from drawbacks such as use of organic solvents, poor extraction efficiency, tedious and expensive methodology. These methods are not encouraged with a view to reducing global warming. The objective was therefore to develop an alternative solvent-free extraction method. An aqueous extract of long pepper fruits was prepared using hydrophilic lipid Gelucire 44/14 as the extracting aid and this was compared with an alcoholic extract. Extracts were characterized using high-performance thin layer chromatography and differential scanning calorimetry. P-glycoprotein (P-gp) inhibitory activity of the aqueous and alcoholic extracts and pure piperine was compared using an in-vitro everted rat intestinal model using ornidazole as the model drug. The study was performed using two oral pretreatment dose levels (10 and 20 mg/kg) and durations (1 and 3 days). Exsorption of ornidazole from serosal to mucosal surface was monitored. P-gp inhibitory activity of the aqueous extract was comparable with that of pure piperine (P > 0.05) and was significantly higher than the alcoholic extract (P < 0.05). Pure piperine and the aqueous extract exhibited significant P-gp inhibitory activity compared with control, which was irrespective of oral pretreatment dose and duration levels. No significant effect of oral pretreatment duration of the aqueous extract was observed. The observed enhancement in P-gp inhibitory activity of the aqueous extract may have been attributed to the P-gp inhibitory potential of Gelucire 44/14 and its efficient extraction and solubility enhancement ability. In the field of phytopharmaceuticals efficient and eco-friendly extraction processes are still a goal to be achieved. Extraction with Gelucire 44/14 could be a potential method of extraction for phytopharmaceuticals. Compared with conventional methods of extraction it is more efficient, easier to prepare, eco-friendly and scalable.

Solvent-free mechanochemical extraction of chondroitin sulfate from shark cartilage

A solvent-free mechanochemical extraction (SFMCE) technology was applied to the extraction of chondroitin sulfate (CS) from shark cartilage. This process was carried out via mechanical pretreatment (MPT) and mechanochemical treatment (MCT) in AGO-2 high-intensity planetary activator at room temperature under solvent-free condition. The yield of CS was increased from 8.50 ± 0.16% to 9.33 ± 0.14% and the purity of product was improved from 86.4 ± 0.88% to 95.1 ± 0.65%. The effectiveness of the MCT was confirmed by HPLC–ELSD analysis. The energy cost was decreased obviously due to the decrease of extraction time from 3 h to 3 min. SFMCE method was proved to be a high-efficient and energy-saving technique.

Forensic analysis of a single particle of partially burnt gunpowder by solid phase micro-extraction–gas chromatography-nitrogen phosphorus detector

Solid phase micro-extraction (SPME) was adopted to extract organic gun shot residues (OGSRs) from a single particle of partially burnt gunpowder. The partially burnt particle samples were collected from gun shot residue (GSR) deposited near the target areas. OGSRs, such as diphenylamine (DPA), methyl centralite (MC), ethyl centralite (EC), from only one single particle of partially burnt gunpowder were successfully extracted by SPME and analyzed by a gas chromatography coupled to a nitrogen phosphorus detector (GC-NPD). The results confirmed that the new extraction procedure is capable of extracting trace amount of MC and EC as signature molecules for the identification of GSR. The method represents a solvent-free extraction as a complementary analytical procedure for the forensic analysis of GSR-related evidences. The new extraction scheme with the capability of analyzing single particle of partially burnt gunpowder can also be applied to the identification of explosive residues, such as in post-blast investigations of improvised explosive devices.

Thermo-responsive Metal-chelating Surfactants: Properties and Use in Cloud Point Extraction of Uranyl Nitrate∗

Abstract The properties of new thermo-responsive functional surfactants, capable of forming a metal chelate, synthesized by grafting a diamide group (amino-acid residue) to the tip hydrophilic endgroup or in a branched position to polyoxyethylene nonionic surfactants [CiEj: CiH2i+1(OCH2CH2)jOH)], are studied. Their use in cloud point extraction of uranyl nitrate is tested. The reversible temperature-dependent behavior of classical non-ionic surfactants associated to phase separation of micellar solutions known as clouding behavior is exploited for separation based on cation specific binding to the chelating group. The functional surfactants under investigation combine surface-active properties and characteristic thermoreversible behavior with a capacity to bind uranyl cation. The influence of the complexation on the cloud points of functional surfactants is determined. The chelating surfactants are found efficient for the cloud point extraction of uranyl nitrate at low surfactant-to-uranyl ratio. These new thermoresponsive surfactants with chelating properties hold most promise for the development of new solvent free extraction processes.

Supramolecular solid-phase extraction of ibuprofen and naproxen from sewage based on the formation of mixed supramolecular aggregates prior to their liquid chromatographic/photometric determination

Sorbents made up of sodium dodecyl sulphate (SDS) hemimicelles, formed onto γ-alumina, were proposed for the quantitative and practically solvent-free solid-phase extraction (SPE) of ibuprofen and naproxen from sewage samples. The formation of drug–SDS mixed aggregates was proved by the pseudophase separation model and their composition as a function of the amount of drug was calculated. The overall hemimicellar SPE procedure consumed only 0.6 mL of methanol since non-organic solvent was required for cartridge conditioning and the drugs were completely eluted using 2 mL of a 0.3 M NaOH:methanol (70:30, v/v) solution. Breakthrough volumes of around 0.75 L and above 1 L were obtained for naproxen and ibuprofen, respectively. No clean-up steps were necessary for the determination of these drugs in sewage because the direct analysis of the eluates by liquid chromatography/UV was matrix effect-free. The identification of the analytes was based on retention times and UV spectra and it was confirmed by on-line fluorescence detection. The detection limits for naproxen and ibuprofen were 0.8 and 9 ng L −1 in wastewater influents and 0.5 and 7 ng L −1 in effluents, respectively. These limits were similar to or lower than those achieved by methods based on conventional sorbents (e.g. C 18–silica or polymeric resins), which invariably require the evaporation of the eluates. The accuracy and precision of the proposed method were assessed by analysing influent and effluent wastewater samples spiked with 2 and 0.4 μg L −1 of each analyte, respectively. The recoveries obtained and the corresponding standard deviations were in the ranges 93–101% and 2–9%. The method was applied to the determination of the target drugs in wastewater from three sewage treatment plants (STPs) in the south of Spain. The concentration of ibuprofen and naproxen ranged between 2.0 and 7.4 μg L −1 and 0.9 and 3.3 μg L −1 in influents and 0.4 and 1.4 μg L −1 and 0.2 and 0.8 μg L −1 in effluents, respectively.

Extraction of Aflatoxins B1 and G1 from Maize by Using Aqueous Sodium Dodecyl Sulfate

Aflatoxins are potent carcinogens produced by certain Aspergillus fungi. The aflatoxins were first discovered in the 1960s, and since then have been found to be distributed worldwide in a variety of commodities, foods, and feeds. Many of the early techniques for detecting aflatoxins involved extraction with halogenated solvents. With the increased availability and use of reversed-phase solid-phase extraction cartridges and the availability of immunoaffinity columns, aqueous mixtures of nonhalogenated solvents have been frequently used. To further reduce the need for solvents, we examined the effects of eliminating solvents during the extraction of maize, using aqueous mixtures of the detergent sodium dodecyl sulfate. After extraction and filtration, aflatoxins B1 (AFB1) and G1 (AFG1) were isolated by using commercially available immunoaffinity columns. The isolated AFB1 and AFG1 were derivatized with trifluoroacetic acid before separation by liquid chromatography with fluorescence detection. In spiked maize, the limits of detection were 0.5 and 1 ng/g for AFB1 and AFG1, respectively. Recoveries of AFB1 from maize spiked at 1-20 ng/g averaged 87.5% (range, 76.3-99.0%), with an average repeatability relative standard deviation (RSDr) of 4.0%. Recoveries of AFG1 from maize spiked at 2-20 ng/g averaged 80.4% (range, 70.3-85.8%), with an average RSDr of 3.5%. This is the first reported demonstration of an effective solvent-free extraction of aflatoxins from maize at ambient pressure, and this extraction procedure may serve to help reduce solvent consumption during aflatoxin analysis.

Development and Application of Solvent-free Extraction for the Detection of Aflatoxin M1 in Dairy Products by Enzyme Immunoassay

The official methods for the quantification of aflatoxin M1 in dairy products (cheese and yogurt) include extraction into dichloromethane or chloroform, evaporation of the solvent, partitioning of the reconstituted residue with hexane, and subsequent analysis. To secure a rapid and inexpensive screen for aflatoxin M1 contamination, a sensitive competitive ELISA, using a rabbit polyclonal antibody, was developed for measuring aflatoxin M1 in milk and used in a comparative study for measuring the extraction efficiency of aflatoxin M1 in aqueous or organic solvent buffers using yogurt samples. An aqueous sodium citrate solution was found to be suitable for extracting aflatoxin M1, thus eliminating the need for organic solvents. The citrate extraction proved to be efficient (recovery ranged from 70 to 124%) in fortified samples of very different kinds of dairy products, including yogurt and six types of cheese. Fourteen yogurt and cheese samples were extracted with citrate solution and analyzed by ELISA. A good correlation was observed (y=0.95x-0.59, r2=0.98) when the data were compared with those obtained through the official method, across a wide range of aflatoxin M1 contaminations (10-200 ng/kg).

Continuous-Flow Microextration Coupled with HPLC for the Determination of 4-Chloroaniline in Chlamydomonas reinhardtii

Aromatic amines are widely used as intermediates in the dye, photographic, pharmaceutical and pesticide industries, and as antioxidants in the polymer industry. Because of their toxicity (Shonali and Richard 1990), several of them have been listed on the priority blacklist released by US Environmental Protection Agency in 1970s. Among several types of methods for degrading aromatic amines, biodegradation is one of the most important methods. So far, many species of bacteria have been isolated to biodegrade aromatic amines (Schnell et al. 1989). Accordingly, it is necessary that a simple and sensitive method be founded to determine the residue of aromatic amines in biological samples. HPLC with UV detection is often applied for the analysis of aromatic amines (Lewin et al. 1997). It is essential that an enrichment step be conducted to achieve low detection limit prior to analysis. Liquid–liquid extraction (LLE) and solid-phase extraction (SPE) are conventional pretreatment methods (Smith et al. 2003). However, the procedure of LLE is time-consuming and requires large quantity of toxic solvent that can be harmful to the environment. SPE requires less solvent, but the presence of particulate matter in the sample often results in plugging of the cartridge. Solid-phase microextraction (SPME), which is a rapid and solvent-free extraction, has been widely used for detecting aromatic amines (Wang et al. 2004; Yan and Jen 2003). However, the main drawback of SPME is that the fiber is expensive yet with a limited lifetime. Liquid-phase microextraction (LPME) is an extremely simple, low-cost and virtually solvent-free sample-preparation technique. Now LPME has developed several different forms, for example static and dynamic LPME, hollow-fiber membrane LPME, headspace LPME, and continuous-flow microextraction (CFME). Among these, CFME is a relatively novel LPME method, first reported by Liu and Lee (2000). It possesses such advantages as low cost, simplicity of pretreatment process, little usage of organic solvent and amity to environment. Much research has been carried out so far on microextraction of aromatic amines from water samples (Zhao et al. 2002). However, little information is available on it from Chlamydomonas reinhardtii samples. Therefore, the objective of this research was to use CFME-HPLC technique for analysis of 4-chloroaniline (4-CA) in C. reinhardtii cells. The effects of different factors on CFME efficiencies were also investigated and these factors included the kind of extraction solvent, solvent drop volume, sample flow rate, extraction time and addition amount of salt. To evaluate its real application effect, the optimal method was used to determine 4-CA in C. reinhardtii cells and tap water samples.

Methods of separation of actinide elements based on complex formation in extraction and sorption systems

In the frame of development of improvements of current liquid–liquid extraction technologies for reprocessing spent nuclear fuel, and for development of effective schemes of HLW treatment, novel methods of recovery and separation of uranium, transuranium and rare-earth elements have been proposed. The methods of solvent-free extraction in supercritical CO 2, countercurrent chromatography, and sorption by fibrous “filled” sorbents are discussed.

Combination of supercritical fluid extraction and gas chromatography-mass spectrometry: Determination of impurities extracted from tablet preparations of the benzodiazepine series

A method is proposed for the determination of moderately volatile organic impurities in pharmaceutical tablet preparations based on a combination of solvent-free supercritical fluid extraction (SFE) and gas chromatography-mass spectrometry. The composition of moderately volatile impurities is determined in pharmaceutical tablet preparations of the benzodiazepine series (diazepam, phenazepam, nitrazepam, and clonazepam).

Development of water‐phase derivatization followed by solid‐phase microextraction and gas chromatography/mass spectrometry for fast determination of valproic acid in human plasma

In this study, a simple, rapid, and sensitive method was developed and validated for the quantification of valproic acid (VPA), an antiepileptic drug, in human plasma, which was based on water-phase derivatization followed by headspace solid-phase microextraction (HS-SPME) and gas chromatography/mass spectrometry (GC/MS). In the proposed method, VPA in plasma was rapidly derivatized with a mixture of isobutyl chloroformate, ethanol and pyridine under mild conditions (room temperature, aqueous medium), and the VPA ethyl ester formed was headspace-extracted and simultaneously concentrated using the SPME technique. Finally, the analyte extracted on SPME fiber was analyzed by GC/MS. The experimental parameters and method validations were studied. The optimal conditions were obtained: PDMS fiber, stirring rate of 1100 rpm, sample temperature of 80 degrees C, extraction time of 20 min, NaCl concentration of 30%. The proposed method had a limit of quantification (0.3 microg/mL), good recovery (89-97%) and precision (RSD value less than 10%). Because the proposed method combined a rapid water-phase derivatization with a fast, simple and solvent-free sample extraction and concentration technique of SPME, the sample preparation time was less than 25 min. This much shortens the whole analysis time of VPA in plasma. The validated method has been successfully used to analyze VPA in human plasma samples for application in pharmacokinetic studies. All these results show that water-phase derivatization followed by HS-SPME and GC/MS is an alternative and powerful method for fast determination of VPA in biological fluids.