Determination of Tetracyclines in Milk by Graphene-Based Solid-Phase Extraction and High-Performance Liquid Chromatography

A graphene-based solid-phase extraction (SPE) column was prepared for the isolation of tetracyclines from milk followed by determination by high-performance liquid chromatography. Graphene provided better separation for tetracyclines than amine-modified graphene and carboxyl-modified graphene. The optimized graphene-based SPE column showed high absorption capacities (greater than 4,660?ng) and high recoveries (exceeding 92%) for tetracycline, oxytetracycline, chlortetracycline, and doxycycline and was successfully reused at least fifty times. The limits of detection in milk were from 10 to 20?ng/mL, with recoveries between 82.3 and 103.6%. Furthermore, the system showed superior performance than two commercial SPE cartridges with respect to recovery, purification, and reusability. Therefore, this approach is suitable for the determination of tetracyclines in milk.     

Determination of Local Anesthetic Drugs in Human Plasma Using Magnetic Solid-Phase Extraction Coupled with High-Performance Liquid Chromatography

In this work, magnetic tetraethylenepentamine (TEPA)-modified carboxyl–carbon nanotubes were synthesized, characterized, and used as adsorbents to conduct magnetic solid-phase extraction (MSPE) for the preconcentration of seven local anesthetic drugs (procaine, lidocaine, mepivacaine, oxybuprocaine, bupivacaine, tetracaine, and cinchocaine) from human plasma. The separation and determination of analytes were performed on high-performance liquid chromatography with UV detection. Several factors affected the extraction efficiency, such as the amount of adsorbents used, extraction time, sample pH, and optimization of elution conditions. Under optimal conditions, satisfactory linear relationships were obtained in the range of 0.02–5.00 mg/L, with the limits of detection (LOD) ranging from 0.003 mg/L to 0.008 mg/L. The recoveries of analytes for spiked human plasma were in the range of 82.0–108%. Moreover, the precision with intra-day and inter-day RSD values were obtained in the range of 1.5–7.7% and 1.5–8.3%. The results indicated that this method could determine the concentration of seven local anesthetic drugs in human plasma with high precision and repeatability and provide support for the clinical monitoring of the concentration of local anesthetic drugs in human plasma.     

Determination of Tetracyclines by Solid-Phase Extraction with a Molecularly Imprinted Polymer and High-Performance Liquid Chromatography

Tetracyclines are widely used antibiotics classified as emerging pollutants and may lead to an increase in bacterial resistance in the environment. In order to determine these compounds at low concentrations, a water-compatible molecularly imprinted polymer was developed for solid-phase extraction followed by high-performance liquid chromatography analysis. The monomers 2-hydroxyethyl methacrylate and glycerol dimethacrylate were added 1 h after the start of the synthesis to provide hydroxyl groups on the polymer surface. This hydrophilic layer established hydrogen bonds with water, minimizing interferences of this solvent in the analyte-polymer complex, increasing analyte adsorption. The polymer was then used for solid-phase extraction to preconcentrate the tetracyclines. The method provided low limits of quantification (5 µg L^?1), good linearity, precision, and accuracy for tetracyclines, with preconcentration factors of 14, 19, 29, and 41 for oxytetracycline, tetracycline, chlortetracycline, and doxycycline, respectively.     

Rapid Determination of Phenolics in Food Packaging by Magnetic Solid-Phase Extraction and High-Performance Liquid Chromatography

A method for magnetic solid-phase extraction was developed for the preconcentration of bisphenol A, bisphenol AF, tetrabromobisphenol A, and 4-tert-octylphenol from food containers and packaging materials. Cetyltrimethylammonium bromide was added to a solution of magnetic nanoparticles to enhance adsorption of the analytes prior to high-performance liquid chromatography. The effects of the amount of surfactant, the amount of magnetic nanoparticles, the pH, the adsorption time, the desorption solution, and the reuse of the extractant were optimized. The linear dynamic ranges were from 0.05 to 25 milligrams per liter. The limits of detection were between 1.21 and 2.48 micrograms per liter, the limits of quantification were from 4.03 to 8.27 micrograms per liter, and the relative standard deviations were between 2.2 and 4.1 percent. This magnetic solid-phase extraction approach was successfully employed for the analysis of plastics with recoveries from 88.0 to 101.1 percent and relative standard deviations between 2.3 and 5.4 percent.     

Determination of Sulfamerazine in River Water Using Thermoresponsive Modified Silica for Solid-Phase Extraction with High-Performance Liquid Chromatography Detection

Four thermoresponsive silica-poly(N-isopropylacrylamide-co-butyl methacrylate) materials were prepared by grafting (N-isopropylacrylamide-co-butyl methacrylate) at different ratios on multimodal porous silica via surface-initiated atom transfer radical polymerization. The thermoresponsive materials were employed as the adsorbent for the rapid determination of sulfamerazine in river water by solid-phase extraction. The properties of silica-poly(N-isopropylacrylamide-co-butyl methacrylate) were characterized by scanning electron microscopy and Fourier transform infrared spectroscopy. Static adsorption measurements showed that the silica-poly(N-isopropylacrylamide-co-butyl methacrylate)₃ material had the highest adsorption characteristics (8.72?mg?g^?1) at 35°C. The solid-phase extraction conditions were optimized, including the elution solvent and its volume used. The thermoresponsive silica-poly(N-isopropylacrylamide-co-butyl methacrylate)₃ material provided satisfactory results for solid-phase extraction, with a recovery of 90.06%, allowing the rapid purification of sulfamerazine in river water.     

Solid-Phase Extraction and High-Performance Liquid Chromatography for Simultaneous Determination of Important Bioactive Ginsenosides in Pharmaceutical Preparations

A robust method based on high-performance liquid chromatography (HPLC) with ultraviolet (UV) detection has been developed for simultaneous determination of six important ginsenosides (Rg1, Re, Rb1, Rc, Rb2, and Rd) in pharmaceutical preparations. For sample preparation, simple and efficient extraction by ultrasonication, combined with solid-phase extraction (SPE) for clean-up, was effective without consuming large amounts of solvent. Chromatographic separation was performed on an ODS column with optimized gradient elution by means of a dual-solvent-pumping system. The validated method results in excellent separation, and quantitative determination is highly precise and accurate. The problem of co-elution of ginsenosides Rg1 and Re is also solved, with good resolution (R_S approx. 1.5). Intraday variation was between 0.2 and 4.4% and interday variation was between 0.4 and 6.5% (n=5 for both). The accuracy was satisfactory—in the range 93.9 to 103.4% from replicate evaluation at three different spiking concentrations. Overall limits of detection based on a typical injection volume of 5 μL were from 1.16 to 1.58 ng μL⁻¹. The validated method enabled complete assessment for quality control of ginseng samples. The technique may be performed with less sample preparation and, consequently, reduced possibility of sample loss.     

Determination of Antibiotics in Surface Water by Solid-Phase Extraction and High-Performance Liquid Chromatography with Diode Array and Mass Spectrometry Detection

A high-performance liquid chromatography method is reported for the determination of antibiotics in water. The antibiotics were simultaneously preconcentrated by solid-phase extraction. High-performance liquid chromatography was performed on a C18 modified column with gradient elution in 25?min at 40°C. The separation was performed using gradient elution with 90:10 acetonitrile:water and 0.1% aqueous formic acid. The antibiotics were identified by diode array detection and mass spectrometry. The established method was suitable for the determination of antibiotics in surface water.     

Bamboo Charcoal as Solid-Phase Extraction Adsorbent for the Determination of Organophosphorus Pesticides in Water Samples by High-Performance Liquid Chromatography

In this paper, bamboo charcoal was successfully developed for the solid-phase extraction adsorbent for the determination of six organophosphorus pesticides in water samples. After the bamboo charcoal was pretreated and packed in the solid-phase extraction cartridge, the organophosphorus pesticides in water samples were carried out the solid-phase extraction. To establish a perfect solid-phase extraction procedure, the experimental conditions including the eluent, eluent volume, pH of the sample, flow rate of the sample, and loading volume of the sample were all investigated. When 100 mL water samples in the pH range of 6–7 were loaded with the flow rate of 2.5 mL · min^?1 and then eluted with 10 mL acetonitrile, the proposed extraction method was validated by the recovery, correlation coefficient (R²), repeatability (RSD, n = 7) and LODs, which were 69.6–93.4%, 0.9982–0.9998, 2.9–5.6%, and 0.08–1.04 µg · L^?1, respectively. Furthermore, the analysis of the tap, snow, and river water samples demonstrated the feasibility of the proposed SPE method for real water samples. Based on the aforementioned factors, it could be concluded that bamboo charcoal was a good solid-phase extraction adsorbent, and this proposed solid-phase extraction method was suitable for the effective enrichment and determination of the organophosphorus pesticides in water samples.     

A High-Performance Liquid Chromatographic Method for the Determination of Doxefazepam in Human Plasma Using a Solid-Phase Extraction Column

Abstract

A procedure for the rapid, quantitative isolation of doxefazepam from plasma with Supelclean LC-18 cartridges is described together with a sensitive HPLC assay for the quantitative determination of the drug. The recovery of doxefazepam was greater than 80 % over an investigated range of 0.1–2.0 μg/ml of plasma. The column extraction of doxefazepam coupled with the versatility of HPLC make this procedure well suited for detailed pharmacokinetic studies and as well as routine plasma analysis of doxefazepam.     

Tocainide Determination by High-Performance Liquid Chromatography

Abstract

Tocainide has been assayed after serum deproteinization with acetonitrile by HPLC. The pH was critical in separating the drug from other interferences in the serum. The method is simple and fast.     

Determination of Elemental Sulfur in Bottom Sediments Using High-Performance Liquid Chromatography

A procedure for determining elemental sulfur in bottom sediments by microcolumn reversed-phase high-performance liquid chromatography was developed. The analytical range was 4–1200 g/g (in terms of the dry weight of a sediment). The procedure is based on the direct injection of acetone extracts of sediments into a chromatographic column. The detection limit was 5 ng/peak (signal-to-noise ratio of 3 : 1); the relative standard deviation was 5.6%. Errors introduced at particular stages of analysis and the total errors were evaluated for different sampling techniques. The results of determining elemental sulfur in the core samples of bottom sediments from Lake Baikal are presented.     

Determination of Squalene Using High-Performance Liquid Chromatography with Diode Array Detection

A high-performance liquid chromatographic method with photodiode array detection has been developed for the determination of squalene. After treated by extraction and fractional crystallization, squalene was analyzed on a C₁₈ column (150 × 3.9 mm, 5 m) with acetonitrile as mobile phase. Excellent linearity of the calibration curve was observed in the range of 100–40000 gL^–1 and the detection limit was 40 gL^–1. The recoveries were from 89.6% to 100.5% and the relative standard deviations were from 0.5% to 1.4%. The method was successfully applied to the determination of squalene in squalene capsules, olive oil, algal lipids and algal cells.     

Rapid Determination of Apomorphine in Brain and Plasma Using High-Performance Liquid Chromatography

Abstract

A new method for quantitative determination of apomorphine in mouse brain and rat plasma is described. The drug was extracted utilizing SEP-PAK C₁₈ cartridge, and quantified by high performance liquid chromatography with electrochemical detector. The average recovery was 92 ± 2.8% with a day-to-day coefficient of variation of 10.2%. Apomorphine concentration in mouse brain and in rat plasma, as a function of dose and time, after injection with apomorphine-HCl were determined. The results indicate that the method is adequate for pharmacokinetic studies.     

Targeted Separation of COX-2 Inhibitor from Pterocephalus hookeri Using Preparative High-Performance Liquid Chromatography Directed by the Affinity Solid-Phase Extraction HPLC System

Pterocephalus hookeri, as a kind of popular traditional Tibetan medicine, is reputed to treat inflammatory related diseases. In the present work, a cyclooxygenase-2 functionalized affinity solid-phase extraction HPLC system was developed and combined with preparative-HPLC for rapidly screening and separating cyclooxygenase-2 ligand from P. hookeri extracts. Firstly, ligands of cyclooxygenase-2 were screened from extracts by affinity solid-phase extraction HPLC system. Then directed by the screening results, the recognized potential active compounds were targeted separated. As a result, the major cyclooxygenase-2 inhibitor of P. hookeri was obtained with a purity of >95%, which was identified as sylvestroside I. To test the accuracy of this method, the anti-inflammatory activity of sylvestroside I was inspected in lipopolysaccharide-induced RAW 264.7 cells. The results show that sylvestroside I significantly suppressed the release of prostaglandin E₂ with dose-dependent, which was in good agreement with the screening result of the affinity solid-phase method. This method of integration of screening and targeted separation proved to be very efficient for the recognition and isolation of cyclooxygenase-2 inhibitors from natural products.     

Determination of Tetracycline in Water and Honey by Iron(II,III)/Aptamer-Based Magnetic Solid-Phase Extraction with High-Performance Liquid Chromatography Analysis

A novel aptamer-based adsorbent was prepared for the magnetic solid-phase extraction of tetracycline. The Fe₃O₄/aptamer adsorbent was fabricated by immobilizing an aptamer on the surface of Fe₃O₄ magnetic nanoparticles by the reaction between avidin and biotin. The parameters affecting the isolation efficiency such as the pH, extraction time, extraction temperature, eluent, and elution time were investigated in detail. Under the optimal conditions, a linear relationship between the peak area and the concentration of tetracycline was observed in the range from 10.0 to 3000.0?µg L^?1 with a correlation coefficient of 0.9985 and a limit of detection of 2.5?µg L^?1. The developed method was successfully employed for the determination of tetracycline in honey and water samples with recovery values from 82.9 to 107.3% and relative standard deviations less than 7.6%. Compared with previously reported methods for the determination of tetracycline, the proposed protocol provides improvements in the limit of detection and specificity with reduced consumption of adsorbent and organic solvents.     

High-Performance Thin-Layer Chromatography and Reversed-Phase High-Performance Liquid Chromatography Methods for Fingerprinting of Salvadora persica Root Powder Extract Using Benzyl Isothiocyanate as Biomarker

JPC – Journal of Planar Chromatography – Modern TLC - Salvadora persica plant having a number of antimicrobial substances and the roots of the S. persica shrub have been demonstrated to...     

Determination of Reserpine in Plasma Using High-Performance Liquid Chromatography with Fluorescence Detection

Abstract

A high-performance liquid chromatographic method for determining reserpine in plasma has been developed. The procedure involves extraction of reserpine from buffered plasma into benzene, oxidation of reserpine to a fluorophor by treatment with vanadium pentoxide in phosphoric acid, and chromatographic separation of the reserpine fluorophor on an octadecylsilane column by ion-pairing with heptanesulfonate ions. Fluorescence monitoring of the column effluent provides high sensitivity of detection and increases the specificity of the procedure. A detection limit of approximately 100 pg of reserpine per ml of plasma was obtained following analysis of 2 ml samples. Analysis of a number of samples demonstrated the applicability of this method in confirming the presence of reserpine in equine plasma specimens collected at various horse shows and in evaluating the pharmacokinetic behavior of reserpine following intramuscular administration to horses.