High-performance Liquid Chromatography-ultraviolet Detection Research Articles

Extraction and determination of strobilurin fungicides residues in apple samples using ultrasound-assisted dispersive liquid-liquid microextraction based on a novel hydrophobic deep eutectic solvent followed by H.P.L.C-U.V

ABSTRACT In this study, several novel and natural hydrophobic deep eutectic solvents (D.E.Ss) were prepared using methyl trioctylammonium chloride (M.T.O.A.C) as H.B.A and different types of straight chain alcohols as H.B.Ds. One of the D.E.Ss composed of M.T.O.A.C and n-butanol was advantageously used to develop an ultrasound-assisted dispersive liquid-liquid microextraction (U.A−D.L.L.M.E) method combined with high-performance liquid chromatography-ultraviolet detection (H.P.L.C−U.V) for the determination of some strobilurin fungicides in apple samples. Several important parameters influencing extraction efficiency were investigated and optimised, including the type and volume of extractant in ultrasound stage, sonication time, the type and volume of D.E.S, sample solution pH and effect of salt addition. Under optimal experimental conditions, the method showed good linearity with correlation coefficients (R 2) of 0.9985 − 0.9991 in the linear range of 4−1500 μg kg−1, low limits of detection of 1.5−2 μg kg−1 and acceptable extraction recoveries in the range of 76−92%. Enrichment factor was in the range of 95–115. The proposed method was successfully applied for the extraction and preconcentration of trace fungicides in apple samples, and the results demonstrated the potential of the synthesised D.E.S for the extraction and determination of contaminants in aqueous samples.

Graphene oxide/polydopamine-polyacrylamide nanocomposite as a sorbent for dispersive micro-solid phase extraction of diazinon from environmental and food samples and its determination by HPLC-UV detection

ABSTRACT Graphene oxide/polydopamine-polyacrylamide nanocomposite as sorbent for dispersive micro-solid phase extraction of diazinon from environmental and food samples was synthesised and coupled with high-performance liquid chromatography-ultraviolet detector. The prepared sorbent was characterised by analytical techniques such as Fourier-transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy–energy-dispersive spectroscopy and thermal gravimetric analysis. Main parameters affecting extraction efficiency of diazinon using dispersive micro-solid phase extraction such as sorbent amount, elution solvent and its volume, sorption and desorption times and pH of sample solution were investigated and optimised. The optimum values are as follow; sorbent amount, 0.2 g; elution solvent, methanol; elution solvent volume, 2.5 mL; sorption time, 10 min; desorption time, 4 min and pH of sample solution, 3. Under the optimised conditions, method detection limit and limit of quantitation values were 0.24 and 1.0 ng/mL, respectively. Relative recovery data for several real samples were obtained within the range of 82.0–98.0% with a relative standard deviation less than 6.5%. The proposed method was successfully applied to quantitative determination of diazinon in several environmental and food samples.

Simultaneous preconcentration of both polar and non-polar Q-markers of flavonoids in traditional Chinese medicine by reverse micellar floating solidification liquid-phase microextraction

A reverse micellar floating solidification liquid-phase microextraction was proposed for simultaneous preconcentration and determination of both polar (scutellarin, baicalin) and non-polar (scutellarein, luteolin, apigenin, wogonin) quality-markers of flavonoids in traditional Chinese medicine coupled with high performance liquid chromatography-ultraviolet detection. In this work, the reverse micelle of Aliquat 336/dodecanol as the extractant was used to enrich target analytes. The synthesis of the reverse micellar extractant was investigated, and its microstructure was characterized by fluorescence microscope and transmission electron microscope. The variables affecting the experimental procedure, including reverse micelle volume, sample phase pH, salt amount, extraction temperature, extraction time and stirring rate were investigated and optimized. Under the optimum conditions, enrichment factors between 155 and 329 for the target analytes, satisfactory linear ranges (r ≥ 0.9983), low detection limits (0.05–0.25 ng mL−1), acceptable precisions (relative standard deviations of 0.2–8.9%) and accuracies (recoveries of 87.2–108.5%) were obtained. The extraction mechanism based on reverse micelle was explored and elucidated. The characteristics of the proposed method were summarized by comparison with others. The developed approach was successfully applied for the extraction and concentration of six quality-markers of flavonoids with different polarities from a traditional Chinese medicinal herb of Scutellariae Barbatae Herba.

Thin film microextraction based on Co3O4@GO-Nylon‐6 polymeric membrane to extract morin and quercetin and determining them through high performance liquid chromatography-ultraviolet detection

The in-situ synthesis of one-dimensional Co3O4@GO nanosorbent and its fabrication into the layers of Nylon-6 polymer have been introduced in the present study. The extraction performance of the prepared membrane was studied through using the prepared membrane for thin-film microextraction of two selected flavonoids (as the model compounds) from different kinds of juice and black tea. The extracted analytes (morin and quercetin) were quantified via high performance liquid chromatography-ultraviolet detection (HPLC-UV). The experimental design optimization strategy including Central Composite Design (CCD) was employed to optimize different TFME variables. The selected factors that were once thought to be effective on TFME were screened by Plackett–Burman Design before the optimization. The following figures of merit were obtained under the achieved optimized condition: the Linear Dynamic Ranges (LDRs): 5.0–500.0 μg L−1 and 5.0–200.0 μg L−1, Limits of Determination (LODs): 1.3 μg L−1 and 1.6 μg L−1, Limits of Quantification (LOQs): 4.3 μg L−1 and 5.1 μg L−1, the Relative Standard Deviations (RSDs) <4.7% (at two concentration levels of 5.0 and 200.0 µg L−1), Absolute Recovery (AR%): 73.0 and 64.0 and enrichment factors of 73.0 and 64.0 for morin and quercetin, respectively. The above-mentioned method was finally used to extract and determine morin and quercetin in natural orange juice, commercial orange juice, natural pear juice, commercial peach juice and black tea. The obtained results showed satisfactory relative recoveries from 90.0% to 98.0% and acceptable precisions (4.8% < RSD < 7.2%). Therefore, the presented method can be considered as an appropriate alternative to the conventional extraction methods in measuring trace amounts of flavonoids in real samples.

Development of Simultaneous Analysis Method for Multi-Compounds Content of New Shilajit Using HPLC-UV and the Cognitive Enhancing Effect: Mongolian Shilajit

Shilajit has a longstanding use as an anti-aging and memory enhancing drug. It is known to have excellent anti-bacterial effects and is believed to be effective for cognitive enhancement, but is difficult to standardize because of the lack of quality control standards. This study, for the first time, proposes a quality control standard using a simultaneous analytical method for the drug’s multi-compound content using high-performance liquid chromatography-ultraviolet detection (HPLC-UV) as an aid for the internationalization of Mongolian Shilajit. Phenolic compounds 1-6 were isolated from Mongolian Shilajit extract using bioassay-guided isolation, and the isolated compounds were evaluated for cognitive-related anti-Alzheimer’s disease (AD) activities using 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical-scavenging, acetylcholinesterase (AChE), butyrylcholinesterase (BChE), β-site amyloid precursor protein-cleaving enzyme 1 (BACE1), and advanced glycation end-product (AGE) formation assays. The isolated compounds showed good effects for each activity. In addition, the isolated compounds were successfully quantified using a validated quantitative HPLC analysis method. As a result, the isolated compounds were suggested as standard marker compounds for Mongolian Shilajit. Also, we proved that the original material of Mongolian Shilajit is a lichen named Xanthoparmelia somloensis (Gyel.) Hale using HPLC-UV, ultra-high-performance liquid chromatography-electrospray ionization/hybrid linear trap-quadruple-orbitrap-high-resolution mass spectrometry (UHPLC-ESI/LTQ-HRMS).

Food frequency questionnaire is a valid assessment tool of quercetin and kaempferol intake in Iranian breast cancer patients according to plasma biomarkers

In epidemiological and clinical studies, the most common nutritional tool to assess dietary flavonol intake is the food frequency questionnaire (FFQ), which needs to contain a detailed list of plant-based foods and be previously validated. Our study aimed to assess the accuracy of dietary flavonol (quercetin, kaempferol, and isorhamnetin) intake from a food frequency questionnaire (FFQ) compared to fasting plasma flavonol concentrations, as biomarkers of exposure, in breast cancer patients. In a consecutive case series, newly diagnosed patients with breast cancer (n = 140) were recruited at Nour-Nejat Hospital, Tabriz, Iran. Flavonol intake was assessed using a validated FFQ. Plasma flavonol concentrations were measured using high-performance liquid chromatography-ultraviolet detection. The accuracy of dietary status was evaluated using a receiver operating characteristic (ROC) and area under the ROC curve (AUC). Dietary status was shown in dichotomous using ROC-cutoff point. The plasma concentrations of quercetin were moderately correlated with dietary intake of quercetin (Spearman's correlation coefficient (rs) = 0.188, P < .05; rpartial= 0.330, P < .01) and plasma concentrations of isorhamnetin (rs = 0.337, P < .001). A linear correlation between dietary levels and plasma concentrations of kaempferol was attained (rpartial = 0.240, P < .05). Using a ROC-cutoff of 61.9 nmol/L for plasma quercetin (test reference), we were able to differentiate between lower and higher consumers of quercetin with an AUCROC-based reference =0.65 (P < .01, sensitivity = 61.8%, and specificity = 60.0%). Using a plasma kaempferol concentration of 60.1 nmol/L (ROC-cutoff), it was possible to detect significant differences between higher and lower intakes of kaempferol (AUCROC-based reference = 0.64, P < .05). The correlations and diagnostic performance with plasma concentrations could present a significant accuracy rate (validity), which seems acceptable for a nutritional questionnaire (FFQ) to assess intakes intake levels of quercetin and kaempferol. An improvement in the accuracy of the flavonol exposure can provide more precise relationship with health outcomes, which may increase their clinical significance.

Quantification of Teicoplanin Using the HPLC-UV Method for Clinical Applications in Critically Ill Patients in Korea.

A high-performance liquid chromatography-ultraviolet detector (HPLC-UV) method has been used to quantify teicoplanin concentrations in human plasma. However, the limited analytical accuracy of previously bioanalytical methods for teicoplanin has given rise to uncertainty due to the use of an external standard. In this study, an internal standard (IS), polymyxin B, was applied to devise a precise, accurate, and feasible HPLC-UV method. The deproteinized plasma sample containing teicoplanin and an IS of acetonitrile was chromatographed on a C18 column with an acidic mobile phase consisting of NaH2PO4 buffer and acetonitrile (78:22, v/v) by isocratic elution and detection at 220 nm. The linearity was in the range 7.8–500 mg/L calculated by the ratio of the teicoplanin signal to the IS signal. This analytical method, validated by FDA guidelines with ICH Q2 (R1), was successfully applied to analyze the plasma samples of patients in the intensive care unit for treating serious resistant bacterial infectious diseases, such as those by methicillin-resistant Staphylococcus aureus and Enterococcus faecalis. The methods suggested the potential for use in routine clinical practice for therapeutic drug monitoring of teicoplanin, providing both improved accuracy and a wide range of linearity from lower than steady-state trough concentrations (10 mg/L) to much higher concentrations.

A fieldable, high-throughput, cost-efficient high performance liquid chromatography-ultraviolet absorption detection (HPLC-UV) method for the quantitation of bispyridinium quaternary aldoxime cholinesterase reactivators in blood

AbstractMono- and bis-pyridinium quaternary aldoximes (K-oximes) have long been employed as cholinesterase reactivator components of antidotes against lethal cholinesterase-inhibiting organophosphorous chemicals. Their positive charge poses difficulties in their chromatographic analysis, resulting in the publication of different approaches for each K-oxime. A multiplexed method is presented for the rapid quantitation of 10 K-oximes in blood with its utility demonstrated in vivo. Liquid chromatography with absorbance detection was employed. Reversed-phase separation was achieved on a highly nonpolar stationary phase. Method validation was based on the respective guideline of the European Medicines Agency. Times to peak concentrations and 120-min areas under the time–concentration curves were determined in rats following intraperitoneal administration. Adequate retention and separation of K-oximes with acceptable peak shapes in short isocratic runs was achieved by adjusting ionic strength, organic content and the concentration of the ion-pairing agent of the mobile phase. Chromatographic properties were governed by optimizing the concentration of dissolved ions. Accurate adjustment of the organic content was indispensable for avoiding peak drifting and splitting. Dose-adjusted exposure to K-347 and K-868 was exceptionally low, while exposure to K-48 was the highest. The method is suitable for screening systemic exposure to various K-oximes and can be extended.

Determination of teicoplanin in human plasma by reverse micelle mediated dispersive liquid-liquid microextraction with high performance liquid chromatography

A reverse micelle mediated dispersive liquid-liquid microextraction (RM-DLLME) combined with high performance liquid chromatography-ultraviolet detector (HPLC-UV) was developed for extraction and determination of 5 A2 components of teicoplanin (TA2-1, TA2-2, TA2-3, TA2-4, TA2-5) in human plasma, and the mechanism of RM-DLLME was analysed and explored. In this method, 80 µL of the reverse micelle solution of cetylpyridinium chloride/n-hexanol (15 mmol/L) was used as the extraction solvent for the separation, extraction and enrichment of the teicoplanin in plasma sample. All factors affecting the extraction efficiencies of the target analytes, such as the amounts of acetonitrile and chloroform, the type and volume of reverse micelle solution, pH and volume of sample phase, dispersant, salt addition, extraction mode and time, centrifugation rate and time, were investigated and optimized. Under the optimum conditions, the 5 A2 components of teicoplanin achieved effective enrichment with the enrichment factors of 228-347 and obtained good linearity in the range of 0.8375-100.5 µg/mL with correlation coefficients higher than 0.9960. The limits of detection were ranged between 0.5025-3.015 µg/mL. Relative standard deviation values of the method precisions were lower than 10.6% and the average recoveries were in the range of 82.7-111.3%. The determination results of the method were demonstrated with favorable characteristics, such as high enrichment, good selectivity and sensitivity, satisfactory precision and accuracy, and this method could be employed to analysis of the teicoplanin in human plasma samples.

Sensitive determination of methotrexate in plasma of children with acute leukemia using double-solvent supramolecular systemas a novel extractant for dispersive liquid-liquid microextraction

Methotrexate, as a folate antagonist, is one of the first anti-neoplasm drugs offered and is still used as an effective drug in the treatment of various malignancies. Methotrexate has a narrow treatment index and is associated with numerous side effects.In thisresearch, for the first time a double-solvent supramolecular system (DSS) was developed as an extractant without disperser solvent for dispersive liquid–liquid microextraction (DLLME). DSS − DLLME was applied to the extraction of methotrexate in plasma of children with acute leukemiaprior to itsdetermination by high-performance liquid chromatography–ultraviolet detection (HPLC − UV). In the present method, two long normal chain alcohols are mixed in a particular ratio, and then it is injected into the sample solution, which is on the magnetic stirrer. In this case, the mixture of the two alcohol changes to new supramolecular aggregate. This new supermolecule is used as an extractant, which has a higher extraction power than any of its components alone. Under the optimum conditions, the calibration graph was linear in the rage of 0.1–150 µg L−1 with detection limit of 0.03 µg L−1. Relative standard deviations (RSDs) including intra–day and inter–day of method based on7 replicate determinations of 100.0 µg L−1of methotrexate were 2.6% and 4.8%,respectively. The results proved that DSS − DLLME is a sensitive, very simple, inexpensive, environmental friendly, rapid and efficient method for the preconcentration of trace amount of drugs in biological samples.

Determination of three diphenyl ether herbicides in rice by magnetic solid phase extraction using Fe&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt;O&amp;lt;sub&amp;gt;4&amp;lt;/sub&amp;gt;@MOF-808 coupled with high performance liquid chromatography

利用溶剂热法构筑了Fe3O4@MOF-808吸附剂,将其用于大米中除草醚(NIT)、乙氧氟草醚(OXY)和甲羧除草醚(BIF)3种二苯醚类除草剂的富集,结合高效液相色谱法,建立了大米中该类除草剂的分析方法。研究通过傅里叶变换红外光谱、X射线衍射仪、扫描电子显微镜以及振动样品磁强计对构筑的磁性吸附剂的结构、表面形貌及磁强度进行表征。表征结果显示,球形的Fe3O4纳米颗粒与八面体形貌的MOF-808成功复合,Fe3O4@MOF-808饱和磁化强度可达40.35 emu/g,可以满足磁性固相萃取的需求;对吸附剂用于大米中3种二苯醚类除草剂富集的磁性固相萃取条件(吸附剂用量、吸附时间、洗脱溶剂种类以及洗脱体积)进行了优化。优化结果显示,25 mg吸附剂在6 min内即可达到对目标物的完全吸附,洗脱溶剂采用0.5 mL×2的甲醇。在最优的磁性固相萃取条件下,结合高效液相色谱-紫外检测法,建立了大米中3种二苯醚类除草剂的分析方法。方法在2~300 μg/L范围内线性关系良好(r > 0.998), NIT、OXY、BIF的检出限和定量限依次为0.6、0.6、0.4 μg/kg和2.0、2.0、1.5 μg/kg,在5、10和20 μg/kg 3个加标水平下的回收率为87.3%~96.7%,相对标准偏差不超过10.8%,且富集因子在25~29之间。将所建方法用于大米中NIT、OXY、BIF的分析,各样品均未检出这3种二苯醚类除草剂。该方法具有操作简单、快速、准确的特点,适用于大米样品中除草剂的残留分析。

Heterocyclic frameworks as efficient sorbents for solid phase extraction-high performance liquid chromatography analysis of nitroimidazoles in chicken meat

In this work, three aromatic heterocycle-based porous organic frameworks (heterocyclic POFs) were prepared through a simple Friedel-Crafts alkylation of furan, thiophene and pyrrole with p-dimethoxybenzene as crosslinker. The prepared heterocyclic POFs, featuring abundant heteroatoms and extended conjugated system, displayed high adsorption affinity for nitroimidazoles (NDZs) antibiotics. So, they were applied as adsorbents for solid phase extraction of NDZs (metronidazole, ronidazole, dimetridazole, ornidazole) from chicken meat before their determination by high performance liquid chromatography-ultraviolet detection. Good linearity range (2.0–100.0 ng g−1), low limits of detection (0.6–1.2 ng g−1), high recovery (84.0–114.5%) and satisfactory precision (relative standard deviations < 10%) for the NDZs were obtained under the optimized conditions. The developed method was successfully applied to determine NDZs s in chicken meat. This work provided a good alternative for the rapid and effective detection of trace NDZs residues in chicken meat samples.

In-situ synthesis of nanocubic cobalt oxide @ graphene oxide nanocomposite reinforced hollow fiber-solid phase microextraction for enrichment of non-steroidal anti-inflammatory drugs from human urine prior to their quantification via high-performance liquid chromatography-ultraviolet detection

The in-situ synthesis and application of nanocubic Co3O4-coated graphene oxide (Co3O4@ GO) was introduced for the first time to present a cost-effective, stable and convenient operation and a simple device for hollow fiber solid-phase microextraction (HF-SPME) of four selected nonsteroidal anti-inflammatory drugs (NSAIDs) including diclofenac, mefenamic acid, ibuprofen and indomethacin. The extracted analytes were desorbed by an appropriate organic solvent and analyzed via high-performance liquid chromatography-ultraviolet detection (HPLC-UV). The prepared sorbent was approved using different characterization methods such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The variables effective on the Co3O4@GO-HF-SPME method including extraction time, desorption time, desorption solvent volume, sample pH, stirring rate and ionic strength were screened via Plackett–Burman design and then optimized by Box–Behnken design. Under optimal condition, the calibration curves were linear within the range of 1.0–200.0 µg L−1 of analyte concentration with detection limits of 0.18–1.1 µg L−1 and the relative standard deviations less than 10.1%. The limits of quantification (LOQs) were in the range of 0.60–3.67 µg L−1. Matrix effect was not observed with this method; therefore, standard addition is not necessary for quantification of target compounds. The enrichment factors were obtained in the range of 49–68. The relative recoveries of the urine sample analysis were calculated in the range of 93–102%. Finally, the presented method exhibited good sensitivity, excellent repeatability, high reusability and acceptable precision, which will be a promising method to analyze various nonsteroidal anti-inflammatory drugs in urine samples.

Amino acids- based hydrophobic natural deep eutectic solvents as a green acceptor phase in two-phase hollow fiber-liquid microextraction for the determination of caffeic acid in coffee, green tea, and tomato samples

In this research, a series of new hydrophobic natural deep eutectic solvents (NADESs) were prepared and utilized as an acceptor phase in two-phase hollow fiber-liquid microextraction (HF-LPME) for the extraction and determination of caffeic acid in coffee, green tea, and tomato samples. The extraction solvent was prepared by mixing amino acids (as hydrogen bond acceptor) and lactic acid (as hydrogen bond donor). The highly stable NADESs (serine: lactic acid) were impregnated in the supported liquid membrane (SLM) and lumen of the hollow fiber. The amino acid-based deep eutectic solvent is a new generation of the extraction solvents for the HF-LPME method which is benefited from cost-effectiveness and lower toxicity. Physical properties of these NADESs, including their melting point, density, and viscosity were also determined. The extracted analyte was analyzed by high-performance liquid chromatography-ultraviolet detection (HPLC-UV). Response surface methodology (RSM) and central composite design (CCD) were applied to optimize the influence of the main extraction parameters. Under the optimal conditions, the proposed method exhibited a wide linear range of 1.0–500.0 ng mL−1 (R2 = 0.984) with satisfactory recoveries above 92.0%. The limit of detection (LOD) and Limit of quantification (LOQ) were of 0.3 ng mL−1 and 0.9 ng mL−1, respectively. The enrichment factor ranged in 418–438 while intra-day and inter-day RSD (relative standard deviation) (n = 5) were below 4.1%. Based on the results, the proposed simple, sensitive, effective, and eco-friendly method can be successfully applied for the analysis of caffeic acid in real food samples.

Determination and risk characterisation of bio-active piperine in black pepper and selected food containing black pepper consumed in Korea.

Piperine is a bio-active compound found in pepper, including Piper nigrum L. and P. longum L. It has a strong, pungent flavour and several pharmacologic benefits. However, the risks of piperine have not yet been characterized. In this study, piperine in black pepper and some selected foods was determined to characterise the risk of exposure to piperine. Piperine in black pepper, curry and noodle was analysed by high-performance liquid chromatography-ultraviolet detection, which was validated through the measurement of performance parameters. The mean concentrations of piperine in black pepper, powdered curry, retorted curry, instant noodle and cup noodle were 4,418, 28, 3.4, 4.3 and 4.2mg/100g, respectively. The estimated dietary exposure to piperine was 123.66μg/kg body weight/day, and the margin of exposure calculated by the no-observed-adverse-effect level of piperine, was 162. The piperine from food does not cause an adverse health effect to the public in Korea.

In-situ formation of Zn-Al layered double oxides on electrochemically anodized nanoporous aluminum film as sorbent for chlorophenols extraction from water and wastewater followed by determination using HPLC.

Herein, we present a simple, cost-effective, and robust strategy for the in-situ preparation of Zn-Al layered double oxides-anodized aluminum thin film via a facile hydrothermal method, followed by calcination treatment of the Zn-Al layered double hydroxide in the air atmosphere. The in-situ prepared Zn-Al layered double oxide-anodized aluminum film was implemented as sorbent for thin film microextraction of four selected chlorophenols (4-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol, and pentachlorophenol), followed by high-performance liquid chromatography-ultraviolet detection. The different variables of the thin film microextraction were screened via Plackett-Burman design and then optimized through Box-Behnken design. Under the optimum condition, the method showed good linear ranges (0.2-200 μg/L) with the coefficient of determinations higher than 0.9938. The calculated limit of detections were between 0.07 and 0.56μg/L. Relative standard deviations of the method for determination of the analytes at 5μg/L concentration level (n=3) were ranged from 3.5 to 3.9% (as interday). The enrichment factors were between 39 and 58. This extraction method was demonstrated to be fast, efficient, and convenient. To study the capability of the developed method for real sample analysis, tap, well, river, and two types of wastewater samples were satisfactorily analyzed.

Novel synthesized attapulgite nanoparticles-based hydrophobic monolithic column for in-tube solid-phase microextraction of thiosildenafil, pseudovardenafil, and norneosildenafil in functional foods.

In this study, a novel method which involved in-tube solid-phase microextraction (SPME) using an attapulgite (ATP) nanoparticles-based hydrophobic monolithic column was successfully developed. It was coupled with high-performance liquid chromatography-ultraviolet detection for the determination of three phosphodiesterase-5 (PDE-5) inhibitors, including thiosildenafil, pseudovardenafil, and norneosildenafil, in functional foods. The monolithic column was prepared by one-step polymerization, using 3-trimethoxysilylpropyl methacrylate-modified ATP nanoparticles and 1-butyl-3-vinylimidazolium bromide (VBIMBr) as the functional monomers, and ethylene glycol dimethacrylate (EDMA) as the cross-linker. The obtained poly(ATP-VBIMBr-EDMA) monolith was characterized by scanning electron microscopy equipped with energy-dispersive analysis of X-ray, Fourier transform infrared spectroscopy, thermogravimetric analysis, and X-ray diffraction. The adsorption capacity, up to 2.00μg/cm calculated by the Langmuir isotherm model, was about six times that of the poly(VBIMBr-EDMA) monolith. Crucial factors affecting the extraction efficiency, including sample solvent, elution solvent, flow rates of sampling loading and elution, sample loading volume, and elution volume, were investigated in details. Under the optimal in-tube SPME conditions, the proposed method showed good reproducibility with run-to-run, column-to-column, and batch-to-batch relative standard deviations less than 7.2%, and low limits of detection of 0.5-0.9ng/mL in real samples. Thiosildenafil was detected in four types of functional foods with the contents of 1.30-4.78μg/g. This newly proposed in-tube SPME method based on poly(ATP-VBIMBr-EDMA) monolith may provide a simple, efficient, and promising alternative to daily monitoring of PDE-5 inhibitors in functional foods.

Polyvinylidene difluoride film with embedded poly(amidoamine) modified graphene oxide for extraction of chlorpyrifos and diazinon

An effective, sensitive, relatively fast, and cost-effective method was developed to determine two types of selected organophosphorus pesticides (OPPs) including diazinon and chlorpyrifos in apple, peach, and four different water samples (river, sea, well, and agriculture wastewater samples) through applying poly(amidoamine)@graphene oxide-reinforced polyvinylidene difluoride thin-film microextraction (PAMAM@GO-PVDF-TFME). The extracted analytes were desorbed via organic solvent and determined using high-performance liquid chromatography-ultraviolet detection (HPLC-UV). The strong interactions between the sorbent and selected analytes (coordination bonds, intermolecular hydrogen bonding, π-π interactions, and hydrophobic effects) made this TFME capable of high extraction performance and capacity. Several factors involved in the PAMAM@GO-PVDF-TFME experiments such as desorption volume, desorption time, sample pH, extraction time, and stirring rate were screened via Plackett-Burman design and then optimized through Box-Behnken design with the purpose of reaching the highest extraction efficiency. The above method showed a good linear range (0.5-500 μg L-1 and 1-500 μg L-1) with the coefficient of determination better 0.9944, low limits of determination (0.12 and 0.20 μg L-1), good enrichment factors (99 and 98), acceptable extraction recoveries (99 and 98%), and good spiking recoveries (90-98%) under the optimized condition at three different spike levels for chlorpyrifos and diazinon, respectively. The results confirmed that the presented method would be promising for the determination of various types of these pesticides in environmental and beverage samples.

Simultaneous extraction and analysis of clozapine and lorazepam from human plasma using dual solvent-stir bar microextraction with different acceptor phases followed by high-performance liquid chromatography ultra-violet detection.

A new design of dual solvent stir bar microextraction (DSSBME) was developed and combined with HPLC-UV for the simultaneous extraction of clozapine (CLZ) and lorazepam (LRP) from human plasma with different acceptor phases. Two short hollow fibers immobilized with an organic extraction solvent were used as the solvent bars for microextraction of CLZ and LRP from the sample solution. The solvent bars were fixed with a staple pin which served as the stirrer. The target analytes were simultaneously and selectively extracted from the sample solution into their corresponding solvent bar. Extraction parameters such as organic solvent type, pH of the sample solution, the acceptor phase concentration, salt incorporation into the solution, stirring rate, and extraction time were optimized to achieve the best extraction results. Under the optimum conditions (1-undecanol as extraction solvent, pH of sample solution = 9.0, 10% w/v NaCl, concentration of HCl = 10 mM, concentration of NaOH = 100 mM, stirring rate of 1400 rpm and extraction time of 30 min at ambient temperature) the limit of detection for CLZ was 0.4 ng mL-1 and for LRP it was 1.1 ng mL-1. The linear range for CLZ was 1.3-1000.0 ng mL-1 (R2 = 0.9991) and for LRP it was 3.6-800.0 ng mL-1 (R2 = 0.9993). Extraction recovery and the enrichment factor for CLZ were 95.4% and 343 and for LRP they were 74.3% and 263, respectively. Finally, the method developed was successfully applied for the simultaneous determination of CLZ and LRP in human plasma samples.

Determination of Methocarbamol in Human Urine Using Dispersive Liquid–Liquid Microextraction Based on Solidification of Organic Drop and Response Surface Methodology for Optimization

A rapid and simple dispersive liquid−liquid microextraction method based on solidification of organic drop with high performance liquid chromatography-ultraviolet detection has been developed for the extraction and quantification of methocarbamol from human urine samples. The effect of extraction and disperser solvents (type and volume), sample solution pH, extraction time and salt effect was investigated. 1-Dodecanol and methanol were selected as extractive and disperser solvents, respectively. Placket-Burman experimental design and response surface methodology have been used for the method optimization. The linear dynamic range of 50–800 µg/L with a correlation coefficient of 0.9988 and a detection limit of 15 µg/L were achieved for the determination of methocarbamol under optimum conditions. The relative standard deviation was less than 3.2% (n = 6). After optimization, the method was successfully applied for the determination of methocarbamol in human urine samples.