High-performance Liquid chromatography-UV Detection Research Articles

Long-lasting concentrations of cefovecin after subcutaneous and intramuscular administration to Patagonian sea lions (Otaria flavescens)

Cefovecin is a third-generation cephalosporin developed as an aqueous solution for use by the subcutaneous route in dogs and cats. This study evaluated the duration of cefovecin plasma concentrations after single intramuscular (IM) or subcutaneous (SC) injection at different doses in 10 Patagonian sea lions (Otaria flavescens). Blood samples were collected serially from the day of the injection up to 60–90 days post-injection. Plasma drug concentrations were determined by high performance liquid chromatography–UV detection and pharmacokinetic parameters were calculated by non-compartmental analysis.No reactions or side effects associated with the drug were observed in any of the studied animals. Both routes showed very similar pharmacokinetic behaviour. Elimination half-life (11.3–21.6 days, SC; 13.1–15.9 days, IM) and mean residence time (17.6–36.8 days SC; 16.5–25.4 days IM) were, in all cases and doses, considerably longer than those previously reported for any other species. Based on these findings, and preliminary data on specific pathogen sensitivity, cefovecin was found to be a very promising antimicrobial for Patagonian sea lions, in particular those that are difficult to access or that are under certain rehabilitation conditions.

Polypyrrole/magnetic nanoparticles composite as an efficient sorbent for dispersive micro-solid-phase extraction of antidepressant drugs from biological fluids

In this study, polypyrrole/magnetic nanoparticles composites in the presence of two different dopants were synthesized with the aid of chemical oxidative polymerization process for dispersive-μ-solid phase extraction (D-μ-SPE). The synthesized magnetic sorbents were characterized by various techniques. The results exhibited that the nanocomposite modified by polypyrrole with sodium perchlorate as a dopant demonstrated higher extraction efficiency for citalopram (CIT) and sertraline (STR) as the model compounds. This nanosorbent in combination with high performance liquid chromatography-UV detection was applied for extraction, preconcentration and determination of CIT and STR in urine and plasma samples. The effect of various parameters on the extraction efficiency including: sample pH, amount of sorbent, sorption time, eluent and its volume, salt content, and elution time were investigated and optimized. The opted conditions were: sample pH, 9.0; sorbent dosage, 10mg; sorption time, 7min; elution solvent and its volume, 0.06molL−1 HCl in methanol, 120μL; elution time, 2min and without addition of salt to the sample. The calibration curves were linear in the concentration range of 1–800μgL−1. The limits of detection (LODs) were obtained in the range of 0.2–1.0μgL−1 for CIT and 0.3–0.7μgL−1 for STR, respectively. The percent of extraction recoveries and relative standard deviations (n=5) were in the range of 93.4–99, 4.8–8.4 for CIT and 94–98.4, 4.3–9.2 for STR, respectively. Finally, the applicability of the method was successfully confirmed by the extraction and determination of CIT and STR in human urine and plasma samples.

Assessment of Pharmacodynamic and Pharmacokinetic Interaction of Aqueous Extract of Cassia auriculata L. and Metformin in Rats.

Background:Cassia auriculata L. (CA) leaf extract might increase the body's production of insulin thereby suppressing the elevated blood glucose and lipid levels in diabetic rats. CA has been used as dietary supplement in India from ancient times.Objective:The present study was to elucidate the synergistic pharmacodynamic (PD) and pharmacokinetic (PK) interaction of metformin (MT) with CA.Materials and Methods:A simple, precise reverse phase high performance liquid chromatography - UV detection mode method was developed to quantify MT in rat plasma. In PD interaction, streptozotocin (45mg/kg, intraperitoneally) induced diabetic Wistar rats weighing 180–250 g of either sex were randomized to receive MT (90 mg/kg, MT-HD), CA (500 mg/kg) separately and in combination of MT (90 mg/kg, MT-HD) + CA (500 mg/kg), and MT (45 mg/kg, MT-LD) + CA (500 mg/kg) (all oral) along with normal and diabetic control groups for 21 days. PK of MT was carried out in normal rats with preadministration of CA (500 mg/kg) for 14 days.Results:PD data showed reasonable blood glucose lowering effect of CA. The reduction of MT dose with combination of CA achieved a similar blood glucose lowering effect of MT alone. PK data showed enhanced time taken to achieve maximum plasma concentration (Cmax), area under the curve (AUC0-t), and Cmax in combination group of MT (90mg/kg) and CA (500mg/kg), and reduction of MT dose in Group III had a reduced Cmax and AUC0-t compared to MT alone treated groups.Conclusion:Co-administration of CA with MT at varying dose showed a synergistic herb-drug interaction. Thus using the synergistic herb-drug interaction, the dose level of MT may be reduced to produce the same therapeutic effect as when taken alone.SUMMARY Elucidating the synergistic pharmacodynamic (PD) and pharmacokinetic (PK) interaction of metformin (MT) with Cassia auriculata L. (CA)PD data showed reasonable blood glucose lowering effect of CA. The reduction of MT dose with combination of CA achieved a similar blood glucose lowering effect of MT alonePK data showed enhanced time taken to achieve maximum plasma concentration (Cmax), area under the curve (AUC0-t), and Cmax in combination group of MT and CA, and reduction of MT dose had a reduced Cmax and AUC0-t compared to MT alone treated groupsCo-administration of CA with MT at varying dose showed a synergistic herb-drug interaction. Thus using the synergistic herb-drug interaction, the dose level of MT may be reduced to produce the same therapeutic effect as when taken alone. Abbreviations used: CA: Cassia auriculata L., PD: Pharmacodynamic, PK: Pharmacokinetic, MT: Metformin, RP-HPLC-UV: Reverse phase High Performance Liquid Chromatography-UV detection mode, Tmax: Time taken to achieve maximum plasma concentration, AUC0-t: Area under the curve, Cmax: Maximum plasma concentration.

Etched Stainless Steel Powder as Novel Sorbent Material for Solid-Phase Extraction Coupled with High-Performance Liquid Chromatography for Determination of Polycyclic Aromatic Hydrocarbons in Water

The etched stainless steel powder was prepared and explored as sorbent material for solid-phase extraction coupled with high-performance liquid chromatography (HPLC) for determination of trace polycyclic aromatic hydrocarbons (PAHs) in environmental matrices. The etched stainless steel powder was shown to be promising for solid-phase extraction of PAHs in environmental samples with subsequent HPLC separation and UV detection. This paper explored different factors that affected the adsorption efficiency of etched stainless steel powder, including the etched time of stainless steel powder, the mass of sorbent, and the volume of water sample, and so on. In the optimum conditions, nine kinds of PAHs, including trace naphthalene, acenaphthylene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benzanthracene and benzopyrene, were extracted by etched stainless powder and the extraction efficiency is satisfactory.

Electrochemical in situ fabrication of titanium dioxide-nanosheets on a titanium wire as a novel coating for selective solid-phase microextraction

A novel TiO2-nanosheets coated fiber for solid-phase microextraction (SPME) was fabricated by anodization of Ti wire substrates in ethylene glycol with concentrated NH4F. The in situ fabricated TiO2-nanosheets were densely embedded into Ti substrates with about 1μm long, 300nm wide and 80nm thick. The as-fabricated TiO2-nanosheets coating was employed to extract polycyclic aromatic hydrocarbons, phthalates and ultraviolet (UV) filters in combination with high performance liquid chromatography-UV detection (HPLC-UV). It was found that the TiO2-nanosheets coating exhibited high extraction capability and good selectivity for some UV filters frequently used in cosmetic sunscreen formulations. The main parameters affecting extraction performance were investigated and optimized. Under the optimized conditions, the calibration graphs were linear in the range of 0.1–400μgL−1. The limits of detection of the proposed method were between 0.026μgL−1 and 0.089μgL−1 (S/N=3). The single fiber repeatability varied from 4.50% to 8.76% and the fiber-to-fiber reproducibility ranged from 7.75% to 9.64% for the extraction of spiked water with 50μgL−1 UV filters (n=5). The SPME-HPLC-UV method was successfully established for the selective preconcentration and sensitive detection of target UV filters from real environmental water samples. Recovery of UV filters spiked at 10μgL−1 and 25μgL−1 ranged from 88.8% to 107% and the relative standard deviations were less than 9.8%. Furthermore the in situ growth of the TiO2-nanosheets coating was performed in a highly reproducible manner and the TiO2-nanosheets coated fiber has high mechanical strength, good stability and long service life.

Dispersive micro-solid-phase extraction of benzodiazepines from biological fluids based on polyaniline/magnetic nanoparticles composite

In this study, diverse types of Fe3O4 nanocomposites modified by polyaniline, polypyrrole, and aniline–pyrrole copolymer were synthesized through chemical oxidative polymerization process for dispersive-μ-solid phase extraction (D-μ-SPE) in the presence of various dopants. The results showed that the nanocomposite modified by polyaniline with p-toluene sulfonic acid as a dopant demonstrated higher extraction efficiency for lorazepam (LRZ) and nitrazepam (NRZ). Also the synthesized magnetic sorbents were characterized. The nanocomposite sorbent in combination with high performance liquid chromatography–UV detection was applied for the extraction, preconcentration and determination of lorazepam and nitrazepam in urine and plasma samples. Different parameters influencing the extraction efficiency including: sample pH, amount of sorbent, sorption time, elution solvent and its volume, salt content, and elution time were optimized. The obtained optimal conditions were: sample pH, 6; amount of sorbent, 5mg; sorption time, 5.0min; elution solvent and its volume, 0.5mM cethyltrimethyl ammonium bromide in acetonitrile, 150μL; elution time, 2.0min and without addition of NaCl. The calibration curves were linear in the concentration range of 1–2000μgL−1. The limits of detection (LODs) were achieved in the range of 0.5–1.8μgL−1 for NRZ and 0.2–2.0μgL−1 for LRZ, respectively. The percent of extraction recoveries and relative standard deviations (n=5) were in the range of 84.0–99.0, 6.1–7.8 for NRZ and 90.0–99.0, 4.1–7.0 for LRZ, respectively. Ultimately, the applicability of the method was successfully confirmed by the extraction and determination of NRZ and LRZ in human urine and plasma samples.

HOMOGENEOUS LIQUID–LIQUID MICROEXTRACTION VIA FLOTATION ASSISTANCE FOLLOWED BY HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY AS AN EFFICIENT AND SENSITIVE TECHNIQUE FOR THE DETERMINATION OF ABAMECTIN IN AQUATIC SAMPLES

Homogeneous liquid–liquid microextraction via flotation assistance (HLLME-FA) and high-performance liquid chromatography-UV detection was presented for the extraction and determination of abamectin in aquatic samples. Toluene at microliter volume level and acetone were used as extraction and homogeneous solvents, respectively. In this research, a special extraction cell was designed to facilitate collection of the low-density extraction solvent. No centrifugation was required in this procedure. The water sample solution was added into the extraction cell, which contained an appropriate mixture of extraction and homogeneous solvents. Using air flotation, extraction solvent was collected at the conical part of the designed cell. The effects of different variables on the efficiency of the extraction such as kind and the volume of extraction and homogeneous solvents, ionic strength, and extraction time were studied and optimized. Under the optimum conditions, the calibration graphs were linear in the range of 2.0–500 µ g L−1 for B1a and 4.0–500 µ g L−1 for B1b with detection limits of 0.5 µ g L−1 for B1a and 1.7 µ g L−1 for B1b. HLLME-FA is a fast, simple, and efficient method for the determination of abamectin in aquatic samples.

EXTRACTION OF SOME CHLOROPHENOLS FROM ENVIRONMENTAL WATERS USING A NOVEL GRAPHENE-BASED MAGNETIC NANOCOMPOSITE FOLLOWED BY HPLC DETERMINATION

A novel graphene-based magnetic nanocomposite (G-Fe3O4) was prepared and used as an effective adsorbent for the preconcentration of some chlorophenols (2-chlorophenol, 3-chlorophenol, 2, 3-dichlorophenol, 3, 4-dichlorophenol, and 2, 4, 6-trichlorophenol) in environmental water samples followed by high performance liquid chromatography-UV detection. Various experimental parameters that could affect the extraction efficiencies, such as the amount of G-Fe3O4, the extraction time, the pH of sample solution and the desorption conditions, have been investigated. Under the optimum conditions, a good linearity existed in the range of 1.0–100.0 ng mL−1 for all the analytes, with the determination coefficients (r2) ranging from 0.9954 to 0.9992. The limits of detection (S/N = 3) of the method were between 0.10 and 0.12 ng mL−1. The relative standard deviations (RSDs) varied from 2.2% to 7.5% (n = 6), and the recoveries of the method for the analytes at spiking levels of 5.0 and 10.0 ng mL−1 were in the range from 85.6% to 107.3%. The method has been successfully applied for the determination of some chlorophenols in environmental water samples.

Development and validation of a new method for determination of topiramate in bulk and pharmaceutical formulation using high performance liquid chromatography-UV detection after pre-column derivatization

Development and validation of a new method for determination of topiramate in bulk and pharmaceutical formulation using high performance liquid chromatography-UV detection after pre-column derivatization

Ionic liquid-based dispersive liquid-liquid microextraction combined with high performance liquid chromatography-UV detection for simultaneous preconcentration and determination of Ni, Co, Cu and Zn in water samples

Ionic liquid-based dispersive liquid-liquid microextraction (IL-DLLME) coupled with high performance liquid chromatography (HPLC)-UV detection was developed for simultaneous extraction and determination of nickel, cobalt, copper and zinc ions. In the proposed approach, salophen (N,N'-bis(salisyliden)-1,2-phenylenediamine) was used as a chelating agent; the ionic liquid, 1-hexeyl-3-methylimidazolium hexafluorophosphate, and acetone were selected as extracting and dispersive solvents, respectively. After extraction, phase separation was performed by centrifugation and the sedimented phase (ionic liquid) was solubilized in acetonitrile and directly injected into the HPLC for subsequent analysis. Baseline separation of metal ion complexes was achieved on a RP-C18 column using a gradient elution of the mixtures of methanol-acetonitrile-water as the mobile phase at a flow rate of 1.0 mL min-1. The influence of variables such as sample pH, concentration of the chelating agent, amount of ionic liquid (extraction solvent), disperser solvent volume, extraction time, salt effect and centrifugation speed were studied and optimized. Under the optimum conditions, the enrichment factor of 222 was obtained. The detection limits for Ni, Co, Cu and Zn were 0.8, 1.6, 1.9 and 2.8 ?g L?1, respectively. The relative standard deviations (RSDs) were in the range of 3.6-5.0 % for all of the investigated metal ions. The proposed procedure was successfully applied to the determination of the studied metal ions in water samples.

Application of high-performance liquid chromatography–UV detection to quantification of clenbuterol in bovine liver samples

A method for the determination of clenbuterol (CLB) concentration in bovine liver by reversed-phase high-performance liquid chromatography (HPLC) with UV detection was developed. The sample was extracted with acetonitrile and isopropanol, followed by HPLC analysis. A reverse-phase column C18 was used, with a UV detector at 214 nm and 0.05 M NaH2PO4 (pH 3.0)/acetonitrile (85:15, v/v) as the mobile phase. The accuracy of the analytical method was estimated by spiking bovine liver samples with three different concentrations of CLB (5.24 ng/g, 20.98 ng/g, and 41.96 ng/g) and recovery of 111.7%, 82.0%, and 84.8%, respectively, was obtained. The precision of the method was estimated by the relative standard deviation, which was < 4.74%. The limit of detection and quantification of CLB were 0.20 ng/g and 0.42 ng/g of liver sample, respectively, and the retention time was 24.82 minutes. The recent discovery of CLB contamination in Mexican food led to the specific inspection of a distribution center for this β-agonist, involving the analysis of a total of 78 bovine liver samples. Of all samples screened, 62% of them had concentrations above the maximum residue limit of 0.6 ng/g set by the United Nations Food and Agricultural Organization for CLB. The analytical method was found to be rapid, sensitive, accurate, repeatable, and reproducible, and could be applied to the measurement of CLB concentration in bovine liver.

Extraction of three nitrophenols using polypyrrole-coated magnetic nanoparticles based on anion exchange process

In this research, the applicability of polypyrrole-coated Fe3O4 nanoparticles (Fe3O4@PPy NPs) as an anion exchange magnetic nanosorbent is demonstrated. For this purpose, three nitrophenols were selected as models which are acidic compounds with low logP values and their extraction in neutral form (only based on hydrophobic interactions) is difficult. The extracted nitrophenols were separated and determined by high-performance liquid chromatography-UV detection. The size, morphology and surface coating of synthesized Fe3O4@PPy NPs have been characterized via different techniques such as Fourier transform infrared spectroscopy, transmission electron microscopy, scanning electron microscopy and thermo-gravimetric analysis. The important parameters influencing the extraction efficiency were studied and optimized. Under the optimum extraction conditions (300mL sample solution with pH 10, extraction and desorption times of 10 and 2min, respectively, 500μL of 0.1M HNO3 in acetonitrile as eluent, and 40mg of adsorbent), a linear range between 0.75 and 100μgL−1 (R2>0.997), and limits of detection ranging from 0.3 to 0.4μgL−1 were obtained. Preconcentration factors in the range of 125–180 were achieved and relative standard deviations (RSDs%) were less than 4.9 (n=4) for the three nitrophenols. The analytical method was successfully applied for environmental water samples such as tap water, rain water and river water. The recoveries varied within the range of 84–109% confirming good performance of the method in various waters samples. The results showed that the proposed method is a rapid, convenient and feasible technique for determination of nitrophenols in aqueous samples.

Determination of atorvastatin in human serum by salting out assisted solvent extraction and reversed-phase high-performance liquid chromatography–UV detection

A simple and rapid technique based on salting out assisted solvent extraction was developed for extraction of atorvastatin from serum sample and high performance liquid chromatography–UV was used for its detection. In the present study, 1.0mL serum was extracted by 0.5mL of acetonitrile and some parameters that can affect extraction such as type and volume of extraction solvent, type of salt, and pH were optimized. Under optimized experimental conditions, the calibration curve was found to be linear in the range of 0.001–10ngmL−1 in human serum and the correlation coefficient (R2) and the limits of detection were >0.99 and 0.0005ngmL−1, respectively. The accuracy of the method in terms of average recovery of the compound in spiked serum and water samples was better than 90%.

Determination of sildenafil, vardenafil and aildenafil in human plasma by dispersive liquid–liquid microextraction-back extraction based on ionic liquid and high performance liquid chromatography-ultraviolet detection

A novel method which involved dispersive liquid-liquid microextraction (DLLME)-back extraction based on ionic liquid (IL) was developed for the determination of three phosphodiesterase-5 (PDE-5) inhibitors, sildenafil (SD), vardenafil (VD) and aildenafil (AD), in human plasma. DLLME based on IL as the extractant solvent and methanol as the dispersive solvent was the first step to extract PDE-5 inhibitors from sample solution; the other step of back extraction was followed by transferring target analytes from the IL to acidified aqueous solution. This two-step extraction ensured the compatibility of the final extractant phase, acidified aqueous solution herein, with the reversed phase high performance liquid chromatography-UV detection, and afforded clean extractant phase. The optimal extraction condition was obtained after systematical optimization. The sample solution (960μL) was extracted by 20μL of 1-octyl-3-methylimidazolium hexafluorophosphate in the presence of 20μL methanol and 300mgmL(-1) NaCl with the assistance of vortex; IL phase enriched with the target analytes was then extracted by 10% acetic acid aqueous solution. Good linearity ranges (SD 1-500ngmL(-1), VD 2-2000ngmL(-1) and AD 2-2000ngmL(-1)) with suitable r(2) (=0.9999) were achieved. Limits of detection (LODs) in pure water were 0.15ngmL(-1), 0.30ngmL(-1) and 0.43ngmL(-1) for VD, SD and AD, respectively. Intra-day and inter-day relative standard deviations were below 6.38%. Finally, this method was applied for the determination of PDE-5 inhibitors in human plasma with satisfactory LODs of 0.92ngmL(-1), 1.19ngmL(-1) and 2.69ngmL(-1) for VD, SD and AD, respectively. Acceptable absolute recoveries were obtained from 100.4% to 103.9%. The developed method afforded a convenient, fast and cost-saving operation with high extraction efficiency for the test analytes. It has potential to be applicable to biological samples.

Determination and removal of antibiotics in secondary effluent using a horizontal subsurface flow constructed wetland

Increased attention is currently being directed towards the potential negative effects of antibiotics and other PPCPs discharged into the aquatic environment via municipal WWTP secondary effluents. A number of analytical methods, such as high performance liquid chromatography technologies, including a high performance liquid chromatography-fluorescence method (HPLC-FLD), high performance liquid chromatography-UV detection method (HPLC-UV) and high performance liquid chromatography-mass spectrometry method (HPLC-MS), have been suggested as determination technologies for antibiotic residues in water. In this study, we implement a HPLC-MS/MS combined method to detect and analyze antibiotics in WWTP secondary effluent and apply a horizontal subsurface flow constructed wetland (CW) as an advanced wastewater treatment for removing antibiotics in the WWTP secondary effluent. The results show that there were 2 macrolides, 2 quinolones and 5 sulfas in WWTP secondary effluent among all the 22 antibiotics considered. After the CW advanced treatment, the concentration removal efficiencies and removal loads of 9 antibiotics were 53-100% and 0.004-0.7307 μg m(-2) per day, respectively.

Characterization of phenolics of Sarcandra glabra by non-targeted high-performance liquid chromatography fingerprinting and following targeted electrospray ionisation tandem mass spectrometry/time-of-flight mass spectrometry analyses

In this study, we successfully characterised the phenolic profiles of Sarcandra glabra (Thunb.) Nakai by high-performance liquid chromatography (HPLC) fingerprinting analyses and mass spectrometry (MS) identification. We first established a specific and valid HPLC approach for fingerprint analysis of S. glabra based on HPLC–UV detection. Using several chemometric methods such as similarity evaluation and principal components analysis, we determined herb-markers peaks from many HPLC peaks. The structures of these herb-markers were further identified targetedly by electrospray ionisation tandem mass spectrometry (ESI-MS/MS)/time-of-flight mass spectrometry (TOF-MS) analyses. As results, four phenolics, including chlorogenic acid, caffeic acid, 4-O-glucopyranosyl rosmarinic acid and rosmarinic acid, were characterised as major herb-markers for the stems of S. glabra, while another three phenolics, including kaempferol-3-O-β-d-glucuronic acid, chlorogenic acid and rosmarinic acid, were characteristic components for the leaves. The compounds may be very useful for further phenolome analysis.

Restricted-access nanoparticles for magnetic solid-phase extraction of steroid hormones from environmental and biological samples

Restricted-access materials based on non-ionic surfactant-coated dodecyl-functionalized magnetic nanoparticles were prepared and applied to extract steroid hormones from environmental and biological samples. The magnetic nanoparticles were synthesized by co-precipitation, and were functionalized with dodecyltriethoxysilane, giving dodecyl-grafted magnetic nanoparticles (C12-Fe3O4). They were further modified with different non-ionic surfactants by self-assembly adsorption. Several types of non-ionic surfactants, Tween-20, 40, 60 and 85, and Span-40, 60 and 80, were investigated as the coatings. Tween surfactants coated C12-Fe3O4, named as TW-20 (40, 60, 85)-C12, exhibited good dispersibility in aqueous solution, which was a preferred character in extraction; besides, TW-20-C12 and TW-40-C12 showed good anti-interference ability and satisfactory reproducibility when they were used as magnetic solid-phase extraction (MSPE) sorbents. The factors that may influence the extraction, including the amount of magnetic nanoparticles, extraction and desorption time, the amount of salt addition, the type and volume of desorption solvent, the volume of methanol addition and pH of sample solution, were investigated in detail. High performance liquid chromatography–UV detection was employed for analysis of target analytes (steroid hormone compounds). The developed method was successfully used for the determination of the target analytes in environmental and urine samples. Both tested materials afforded good recovery, satisfactory reproducibility and low limits of detection for environmental samples, which indicates that the materials possessed anti-interference ability. However, compared to TW-40-C12, TW-20-C12 nanoparticles provided better recovery in relatively complex biological samples, which may indicate that the latter one is more appreciated in complex samples.

Evaluation of Dispersive Liquid–Liquid Microextraction–HPLC–UV for Determination of Deoxynivalenol (DON) in Wheat Flour

A fast and simple method for the extraction of deoxynivalenol (DON) from wheat flour using dispersive liquid–liquid microextraction (DLLME) followed by high-performance liquid chromatography–UV detection has been developed and compared with immunoaffinity column cleanup (IAC) process. The influence of several important parameters on the extraction efficacy was studied. Under optimized conditions, a linear calibration curve was obtained in the range of 50–1,000 μg/L. Average recoveries of DON from spiked wheat samples at levels of 500 μg/kg for DLLME and IAC ranged from 72.9 ± 1.6 and 85.5 ± 3.1, respectively. A good correlation was found for spiked samples between DLLME and IAC methods. The limit of detection was 125 and 50 μg/kg for DLLME and IAC method, respectively. Advantages of DLLME method with respect to the IAC have been pointed out.

Determination of Vitamin E Isomers of Grape Seeds By High-Performance Liquid Chromatography-UV Detection

A simple analytical method for the determination of vitamin E isomers in grape seeds by reversed-phase high-performance liquid chromatography with UV detection is described. The method is based on a solid-liquid extraction separation on an ODS column, and the analytes are monitored at 295 nm with a UV detector. Tocopherols are extracted in n-hexane and directly injected onto the column without using any purification step, such as saponification, prior to the separation and determination. The chromatographic separation of tocopherols is achieved in 12 min with a mobile phase that consists of n-hexane and isopropyl alcohol (99.99:0.01, v/v). The method is reproducible and accurate, with respect to demonstrating a relative standard deviation between 2.57% and 3.30% (n = 10, for 500 ng/mL) and a relative error between 0.84% and 6.54% (n = 10, for 500 ng/mL), respectively. The theoretical limits are estimated as 25 ng/mL for α-tocopherol, 43 ng/mL for γ-tocopherol, and 83 ng/mL for δ-tocopherols. The method is then applied for the determination of tocopherols in grape seeds grown in Turkey. The amounts of tocopherols are calculated by using the standard addition method.

Ultrasound-assisted emulsification microextraction using low density solvent for analysis of toxic nitrophenols in natural waters

An ultrasound-assisted emulsification microextraction (USAEME) based on low-density solvents was successfully applied for the extraction and pre-concentration of four toxic nitrophenols in water samples. The extracted analytes were analyzed by high-performance liquid chromatography-UV detection. The important parameters influencing the extraction efficiency were studied and optimized utilizing two different optimization methods: one variable at a time (OVAT) and central composite design (CCD). The results showed that the emulsification process can be completed in a few seconds using low-density solvents, but almost 10–20 min is necessary for high-density solvents. Under the optimum conditions (extraction solvent, 1-octanol; extraction solvent volume, 40 µL; sample pH, 3.0; salt concentration, 20% (w/v) NaCl; extraction temperature, 40 (±3)°C), limits of detection of the method were in the range of 0.25 to 1 µg L−1 and the repeatability and reproducibility of the proposed method, expressed as relative deviation, varied in the range of 2.2–4.2% and 4.7–6.9%, respectively. Linearity was found to be in the range of 1 to 200 µg L−1 and the preconcentration factors (PFs) were between 77 and 175. The relative recoveries of the four nitrophenols from water samples at spiking level of 10.0 µg L−1 were in the range of 92.0 to 115.0%.