HPLC-photodiode Array Detection Research Articles

Synthesis, characterization and application of a polyindole coated magnetic porous carbon nanoadsorbent for extraction and determination of toxic aromatic amines

In this research, a polyindole coated magnetic porous carbon (MPC@PIN) nanoadsorbent was synthesized and applied to the extraction of toxic aromatic amines from divers real water. The MPC was derived from MIL-53(Fe) as a metal–organic framework (MOF) source by calcination of the MOF under an inert atmosphere. After that, the functionalization process was performed by the polymerization of indole on the surface of the MPC. The synthesized nanoadsorbent (MPC@PIN) was characterized by various methods such as Fourier transform-infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and vibrating sample magnetometry (VSM). Separation and determination of the target analytes was performed by HPLC-photodiode array (PDA) detection system. The extraction performance of MIL-53(Fe), MPC, and MPC@PIN was compared toward the target analytes, and the results exhibit the best extraction efficiency for the MPC@PIN. After optimization of the affecting parameters, LODs and linear ranges were 0.05–0.2 µg/L and 0.15–400 µg/L, respectively. Precision (n = 3) of the method as intra-day RSD, and inter-day RSD values were obtained in the range of 3.5–8.2%, and 5.8–12.3%, respectively. Finally, the method applicability was affirmed by analyzing various water samples, satisfactorily. To prepare spiked water samples, a small volume of the AAs standard solution was added to each sample, and then the spiked sample was subjected to the MSPE process.

Purification and mass spectrometry study of Maillard reaction impurities in five acyclic nucleoside antiviral drugs

Maillard degradation products may lead to a decrease in active pharmaceutical ingredients and an increase in harmful substances. In this study, five acyclic nucleoside antiviral drugs (adefovir dipivoxil, famciclovir, tenofovir dipivoxil, acyclovir, and ganciclovir) were studied. Compatibility of APIs and lactose was performed, and the Maillard reaction products were monitored by HPLC–photodiode array detection and UHPLC–ESI–MS. Eight Maillard reaction products were detected, of which six were found to be new stable compounds (impurities 1–6) and were purified and identified by NMR spectroscopy. Moreover, the six new impurities were analyzed by MS/MS, and their mass spectrometric fragmentation mechanisms were proposed. The loss of a neutral fragment at 282 Da by the fragmentation of the lactose moiety was observed in the tandem mass spectra of all the impurities. This is the first systematic study of the Maillard reaction in the case of acyclic nucleosides antiviral drugs, and it has achieved good results. The results will be helpful for understanding the mass spectrometric fragmentation mechanisms of Maillard reaction products and the stability of acyclic nucleosides, and will provide suggestions for maintaining the stability and optimizing the storage and transportation conditions of these drugs.

Pressure-Mediated Reflection Spectroscopy Criterion Validity as a Biomarker of Fruit and Vegetable Intake: A 2-Site Cross-Sectional Study of 4 Racial or Ethnic Groups

BackgroundValid biomarkers of fruit and vegetable (FV) intake are needed for field-based nutrition research. ObjectivesTo examine criterion-related validity of pressure-mediated reflection spectroscopy as a proxy measure of FV intake, using plasma carotenoids and self-reported FV and carotenoid intake as primary and secondary criterion measures, respectively. MethodsHealthy adults 18–65 y of age, self-identifying as African American/black (n = 61), Asian (n = 53), white (n = 70), or Hispanic (n = 29), in North Carolina and Minnesota were recruited. Skin carotenoids were assessed via pressure-mediated reflection spectroscopy (Veggie Meter), skin melanin via spectrophotometer, and total plasma carotenoid concentration by HPLC–photodiode array detection. Self-reported carotenoid and FV intake was assessed using a semiquantitative FFQ. Relations between skin carotenoids, plasma carotenoids, FV, and carotenoid intake, with differences by race or ethnicity, age, sex, weight status, cholesterol, and melanin index, were examined by bivariate correlations and adjusted multivariate linear regressions. ResultsThe overall unadjusted correlation between skin and total plasma carotenoids was r = 0.71 and ranged from 0.64 (non-Hispanic black) to 0.80 (Hispanic). Correlations between skin carotenoids and self-reported FV intake ranged from 0.24 (non-Hispanic black) to 0.53 (non-Hispanic white), with an overall correlation of r = 0.35. In models adjusted for age, sex, racial or ethnic group, and BMI, skin carotenoids were associated with plasma carotenoids (R2 = 0.55), FV (R2 = 0.17), and carotenoid intake (R2 = 0.20). For both plasma carotenoid and FV measures, associations with skin carotenoids did not vary by race, but these relations did differ by skin melanin—those with lower melanin had a lower correlation between skin and plasma carotenoids. ConclusionsReflection spectroscopy–assessed skin carotenoids may be a reasonable alternative to measurement of plasma carotenoids, a biomarker used to approximate FV intake.

Determination of Chromatographic Assay of Deferasirox in Bulk and Pharmaceutical Dosage Form

Deferasirox belongs to the class antidote, which is not official in any pharmacopoeia. But only a few reported studies were availableemploying RP-HPLC technique. To validate the analytical process, we chose bulk powder and tablets of different intensity deferasirox tablets.The objective of the research or analysis is to develop a sensitive reverse phase chromatography method and validate quantitative perseverance of deferasirox in bulk and marketed formulation. A Simple, precise, accurate, economical and reliable UVspectrometric method has been developed toestimate deferasirox bulk and its tablet dosage form. The method was validated as per the international conference on harmonization (ICHQ2AR1) the validated dosage type was tested for device suitability, precision, linearity, specificity, robustness, and ruggedness.Statistical analysis proved that the method is repeatable and specific for the determination of the said drug. The established procedure or technique was done using Inertsil ODS 3V (C18 250mm X 4.6mm, 5µm) column oven temperature 40°C and sample temperature is 8°C with a flow rate of 1.5mL/min. By using HPLC waters PU-2487 pump and photodiode array detector at 245nm. The separation was carried out using a mobile phase consisting of amixture of sodium di hydrogen phosphate monohydrate buffer (pH3.0) and acetonitrile in the ratio of 45:55. The retention time of Deferasirox peak was considered to be about 7.5 min and the total run time was found to be 20 minutes.The calibration plot gave linear relationship over the concentration range of 6.28- 811.480 µg/ml The average percent recovery was proved to be 96.1,97.6&103.The correlation coefficient was found to be 0.999. The relative standard deviation (R.S.D) was found <2.0% for the UV-spectroscopic RP-HPLC method. The percent assessment of the drug was around 100% indicating the accuracy of the procedure. The suggested techniques were further confirmed and employed for the testing of the drug in tablet preparation.

High-Throughput Screening and Characterization of Phenolic Compounds in Stone Fruits Waste by LC-ESI-QTOF-MS/MS and Their Potential Antioxidant Activities

Stone fruits, including peach (Prunus persica L.), nectarine (Prunus nucipersica L.), plum (Prunus domestica L.) and apricot (Prunus armeniaca L.) are common commercial fruits in the market. However, a huge amount of stone fruits waste is produced throughout the food supply chain during picking, handling, processing, packaging, storage, transportation, retailing and final consumption. These stone fruits waste contain high phenolic content which are the main contributors to the antioxidant potential and associated health benefits. The antioxidant results showed that plum waste contained higher concentrations of total phenolic content (TPC) (0.94 ± 0.07 mg gallic acid equivalents (GAE)/g) and total flavonoid content (TFC) (0.34 ± 0.01 mg quercetin equivalents (QE)/g), while apricot waste contained a higher concentration of total tannin content (TTC) (0.19 ± 0.03 mg catechin equivalents (CE)/g) and DPPH activity (1.47 ± 0.12 mg ascorbic acid equivalents (AAE)/g). However, nectarine waste had higher antioxidant capacity in ferric reducing-antioxidant power (FRAP) (0.98 ± 0.02 mg AAE/g) and total antioxidant capacity (TAC) (0.91 ± 0.09 mg AAE/g) assays, while peach waste showed higher antioxidant capacity in 2,2′-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) assay (0.43 ± 0.09 mg AAE/g) as compared to other stone fruits waste. Qualitative and quantitative phenolic analysis of Australian grown stone fruits waste were conducted by liquid chromatography coupled with electrospray-ionization quadrupole time-of-flight mass spectrometry (LC-ESI-QTOF-MS/MS) and HPLC-photodiode array detection (PDA). The LC-ESI-QTOF-MS/MS result indicates that 59 phenolic compounds were tentatively characterized in peach (33 compounds), nectarine (28), plum (38) and apricot (23). The HPLC-PDA indicated that p-hydroxybenzoic acid (18.64 ± 1.30 mg/g) was detected to be the most dominant phenolic acid and quercetin (19.68 ± 1.38 mg/g) was the most significant flavonoid in stone fruits waste. Hence, it could be concluded that stone fruit waste contains various phenolic compounds and have antioxidant potential. The results could support the applications of these stone fruit wastes in other food, feed, nutraceutical and pharmaceutical industries.

A simple multi-residue method for determination of oxytetracycline, tetracycline and chlortetracycline in export buffalo meat by HPLC-photodiode array detector

The development of a simple, rapid and sensitive method for residue monitoring of oxytetracycline (OTC), tetracycline (TC) and chlortetracycline (CTC) in buffalo meat samples is described. The principal steps involved extraction in McIIvaine buffer (pH 3.85) followed by a solid phase clean up step. In HPLC, a reversed phase C8 (RP-C8) column was used and compounds were separated at 35°C using a mobile phase of 0.01 M oxalic acid buffer (pH 1.6)/acetonitrile/methanol (77:18:5, v/v/v) at a flow rate of 0.6 mL/min. A wavelength of PDA detector was set at 355 nm. The detection limit of the method was calculated to be 0.031 μg/g and the minimum detectable quantity was found to be 0.062 μg/g. The statistical evaluation demonstrated high absolute recoveries of OTC, TC and CTC from spiked samples at three fortification levels, which were higher than 78% for all drugs. Excellent method repeatability and reproducibility was found by intra- and inter-day assay precision, yielding the coefficients of variation not more than 11.4 and 14.5% at 0.062 μg/g spike concentrations, respectively. The method was also employed for monitoring of 122 export buffalo meat samples collected from different parts of India, in which only 5 samples showed detectable concentration of OTC residues but were lower than the maximum residue limits (MRLs) set by Codex Alimentarius Commission (CAC), European Union (EU), and United States Food and Drug Administration (US-FDA). TC and CTC were absent in all Samples.

Development and Validation of a Reversed Phase High Performance Liquid Chromatography-Photodiode Array Detection Method for Simultaneous Identification and Quantification of Coumarin, Precocene-I, β-Caryophyllene Oxide, α-Humulene, and β-Caryophyllene in Ageratum Conyzoides Extracts and Essential Oils from Plants.

Ageratum conyzoides is an aromatic plant. It is considered as an invasive and cosmopolite weed, widely spread in tropical and subtropical regions. Phytochemicals such as benzopyrenes, flavonoids, and terpenoids are reported from A. conyzoides. Development and validation of a reversed-phase HPLC-photodiode array (PDA) detection method for simultaneous identification and quantification of coumarin, precocene-I, β-caryophyllene oxide, α-humulene, and β-caryophyllene in extracts of A. conyzoides and essential oils was carried out. Separation of analytes was achieved on a RP-18 (250 mm × 4.6 mm, 5 µm) column using a solvent system comprising of a mixture of acetonitrile and water with 0.05% trifluoroacetic acid in gradient elution mode at ambient temperature with flow rate of 1 mL/min. The retention time of coumarin, precocene-I, β-caryophyllene oxide, α-humulene, and β-caryophyllene was 4.38, 12.86, 20.10, 33.34, and 35.11 min, respectively. Limits of detection for coumarin, precocene-I, β-caryophyllene oxide, α-humulene, and β-caryophyllene were 2.5, 2.5, 2.5, 0.025, and 2.5 µg/mL, respectively. Similarly, LOQ were 10, 10, 10, 0.10, and 10 µg/mL for coumarin, precocene-I, β-caryophyllene oxide, α-humulene, and β- caryophyllene, respectively. Repeatabilities (RSD, %) values for intraday and interday precision for coumarin, precocene-I, β-caryophyllene oxide, α-humulene, and β-caryophyllene was 0.765-2.086 and 0.886-2.128; 0.879-1.672 and 0.979-1.825; 0.696-2.418 and 0.768-2.592; 1.728-2.362 and 1.965-2.378; 1.615-2.897 and 1.658-2.906, respectively. The separation of five analytes was achieved within 50 min. The developed and validated HPLC-PDA method was successfully applied for identification and quantification of above five analytes in A. conyzoides extracts and essential oils. The method could be used for meeting the characterization criteria of phytoformulations.

Development of Fe3O4-modified-carboxylic MWCNTs for extraction and determination of pigments in beverage

A nanomaterial comprising Fe3O4-modified-carboxylic multi-walled carbon nanotubes (Fe3O4-MWCNTs-COOH) was prepared by a co-precipitation method. Combined with HPLC-photodiode array detector (DAD), Fe3O4-MWCNTs-COOH was used to determine pigments in beverage. Some important parameters that could influence extraction efficiency were optimized. The results indicated that Fe3O4-MWCNTs-COOH combined with HPLC-DAD is a promising solid-phase extraction material for the sample pretreatment in the determination of pigments.

Novel MIPs-Parabens based SPE Stationary Phases Characterization and Application.

In this work, the synthesis, characterization, and application of novel parabens imprinted polymers as highly selective solid-phase extraction (SPE) sorbents have been reported. The imprinted polymers were created using sol–gel molecular imprinting process. All the seven parabens were considered herein in order to check the phase selectivity. By means of a validated HPLC-photodiode array detector (PDA) method all seven parabens were resolved in a single chromatographic run of 25 min. These SPE sorbents, in-house packed in SPE empty cartridges, were first characterized in terms of extraction capability, breakthrough volume, retention volume, hold-up volume, number of theoretical plates, and retention factor. Finally, the device was applied to a real urine sample to check the method feasibility on a very complex matrix. The new paraben imprinted SPE sorbents, not yet present in the literature, potentially encourage the development of novel molecularly imprinted polymers (MIPs) to enhance the extraction efficiency, and consequently the overall analytical performances, when the trace quantification is required.

Pectin extraction from common fig skin by different methods: The physicochemical, rheological, functional, and structural evaluations

Four extraction methods of hot-water (HWE), ultrasound-assisted (UAE), microwave-assisted (MAE), and ultrasound-microwave assisted (UMAE) were utilized to determine the best technique to extract pectin from the common fig (Ficus carica L.) skin. UMAE (11.71%) significantly showed a more extraction yield than MAE (9.26%), UAE (8.74%), and HWE (6.05%). A significant dose-dependent antioxidant capacity for pectins 1,1-diphenyl-2-picryl-hydrazyl (DPPH), and 2,2′-azinobis (3-ethylbenzothiazoline-6-sulphonicacid) (ABTS) radical scavenging activity was found. The UMAE-pectin with the maximum galacturonic acid content (76.85%) and molecular weight (6.91 × 103 kDa) presented the highest emulsifying activity (61.2–61.3%) and emulsion stability (94.3–95.2%) with a monomodal droplet size distribution at cold and ambient storage temperatures. A non-Newtonian shear-thinning behavior was detected at 1.5–3.0% pectic-solutions. X-ray diffraction (XRD) analysis showed a non-crystalline nature for pectins extracted by UMAE. FTIR spectroscopy and HPLC photodiode array detector revealed that conventional and novel extraction technologies do not change the chemical structure and monosaccharide composition of pectin significantly.

Studies on the physicochemical characteristics of the New Zealand deer’s tail, Cervus elaphus var. scoticus (III)

This study was designed to determine the nutritional profile and functional components of the NZT (New Zealand deer's tail, Cervus elaphus var. scoticus Lönnberg). Twenty-nine fatty acids, eighteen amino acids, twenty-five minerals, chondroitin, and phospholipids were detected by the auto-fatty acid analyzer, auto-amino acid analyzer, inductively coupled plasma optical emission spectrophotometer, absorbance measurements, and by weighing after separating, respectively. 7-Ketocholesterol was isolated from alcohol extract by silica gel column chromatography analysis. Four steroid hormones (androstene-3,17-dione, β-estradiol, testosterone, and dehydroepiandrosterone), one base and seven nucleosides, and N-acetylneuraminic acid were detected by a HPLC-photodiode array and HPLC-fluorescence detector. As a result, NZT was composed of many nutritional and functional ingredients found in New Zealand deer's antler (NZA) which was one of deer co-products, and it was considered that NZT could be a novel health food resource such as NZA.

Extraction Optimization for Phenolic- and Withanolide-Rich Fractions from Withania somnifera Roots: Identification and Quantification of Withaferin A, 12-Deoxywithastromonolide, and Withanolide A in Plant Materials and Marketed Formulations Using a Reversed-Phase HPLC-Photodiode Array Detection Method.

Background: Both the roots and leaves of Withania somnifera are products of commerce. They contain active compounds of therapeutic value and mostly different withanolides. Several pharmacological activities of W. somnifera have links to one or more withanolides. The presence of phenolic compounds in extracts could play a vital role in the reduction of blood glucose levels in diabetic subjects. Objective: The present study was carried out for the selection of a solvent to prepare extracts rich in phenolics, withaferin A (WA), 12-deoxywithastromonolide (12WD), and withanolide A (WDA). A simple, rapid HPLC method was also developed for the identification and quantification of WA, 12WD, and WDA. Methods: The extraction efficiency of aqueous alcoholic solvents including hexane, chloroform, ethyl acetate, and methanol were compared for three selected withanolides and total phenolic content. The contents of WA, 12WD, and WDA and total phenolics were determined in the extracts. The quality of nine formulations containing W. sominfera were also compared in terms of the content of WA, 12WD, and WDA and total phenolics. Results: The maximum extract yield and the total withanolide and phenolic content were obtained from aqueous alcoholic compositions at 50:50 (v/v), 70:30 (v/v), and 100:0 (v/v), respectively. In the case of organic solvents, chloroform and ethyl acetate yielded the highest concentrations of phenolics and three withanolides, respectively. The total phenolic content in formulations was in the range of 1.84-3.13%, and total withanolide content showed wide variability. Conclusions: The outcome of the present investigation could be utilized for the selection of extraction solvents to prepare W. somnifera-enriched extracts and their quality monitoring by using the developed and validated HPLC-Photodiode array detection method. Highlights: A process for preparation of phenolics and withanolides (withaferin A, 12-deoxywithastramonolide and withanolide A) enriched extracts of Withania somnifera. Simple and rapid HPLC method was also developed and validated as per the ICH guidelines for identification and quantification of three major withanolides. The developed HPLC method was applied to analyze the quality of extracts and marketed herbal products (mono, as well as poly constituents). Optimized extraction process could be utilized for upscaling process development in preparation of enriched extracts from Withania somnifera, crop improvement, bio-prospection studies and quality control.

Determination of acidic, basic and amphoteric drugs in biological fluids and wastewater after their simultaneous dispersive micro-solid phase extraction using multiwalled carbon nanotubes/magnetite nanoparticles@poly(2-aminopyrimidine) composite

Determining of acidic, basic and amphiprotic drugs from different samples simultaneously is a remarkable and discussible topic in sample preparation methods. In this work, an easy and fast dispersive micro-solid phase extraction (D-μ-SPE) method was developed using a magnetic multiwalled carbon nanotubes/Fe3O4@poly(2‑aminopyrimidine) (MWCNTs/Fe3O4@PAPy) as a viable and efficient sorbent to preconcentrate and determine five model analytes in three different classes (nortriptyline, cetirizine, naproxen, diclofenac and ibuprofen). The nanosorbent was characterized by diverse characterization techniques. After the extraction step, HPLC-photo diode array detection (HPLC-DAD) was employed to quantify the model analytes. The effects of various parameters on the dispersive magnetic solid phase extraction method were explored thoroughly via design of experiment and desirability function. The highest extraction performance was obtained under the conditions of: a sample pH of 2, a sorbent amount of 8 mg, a sorption time of 5 min, a salt concentration of 20% w/v in the sample solution, 120 μL 0.01 mol L−1 HCl in acetonitrile as an eluent, and an elution time of 2 min. By employing the optimum conditions detection limits and linear dynamic ranges were obtained in the range of 0.07–3.5 μg L−1 and 0.25–1500 μg L−1, respectively. The relative standard deviations (n = 5) were between 1.4% and 10.5%. Eventually, this method was simply applied for determination and extraction of target analytes in different samples.

Fast SPE and HPLC–DAD determination of brucine in human urine using multi-walled carbon nanotubes modified with magnetic nanoparticles

A nanomaterial comprising Fe3O4-modified hydroxylated multi-walled carbon nanotubes (Fe3O4–MWCNTs–OH) was prepared by a co-precipitation method. Combined with HPLC-photodiode array detector (DAD), Fe3O4–MWCNTs–OH was used to determine brucine in human urine. Some important parameters that could influence extraction efficiency of brucine were optimized, including the extraction time, amounts of Fe3O4–MWCNTs–OH, pH of sample solutions, desorption solvent and desorption time. Under the optimal conditions, the recoveries of brucine from spiked urine samples were between 93.1 and 104.1%, and the relative standard deviations (RSDs) ranged from 3.1 to 5.7%. The correlation coefficient was 0.9997. The limits of detection and quantification were 6 and 21 ng/mL at a signal-to-noise ratio of 3 and 10, respectively. The results indicated that Fe3O4–MWCNTs–OH combined with HPLC–DAD is a promising solid-phase extraction material for the sample pretreatment in the determination of brucine.

Identification and quantification of phenolics in Australian native mint (Mentha australis R. Br.)

Australian native mints have traditionally been used by the aboriginal people for natural remedies; however, their bioactive components have not been studied. Antioxidant capacity and composition of phenolic compounds of Mentha australis R. Br., Lamiaceae were investigated for the first time. Phenolic compounds were analyzed by HPLC photodiode array detector, liquid chromatography high resolution mass spectrometry, tandem mass spectrometry and nuclear magnetic resonance spectroscopy. Aqueous methanolic extract of the mint exhibited comparable antioxidant capacity to the common spearmint. Major compounds identified in the extract were rosmarinic acid (160.4±0.85μgmg−1purified extract), neoponcirin (145.0±0.42μggallicacidequivalent(GAE)mg−1), narirutin (30.3±0.02μgGAEmg−1), chlorogenic acid (15.4±0.05μgmg−1) and biochanin A (9.6±0.06μgGAEmg−1), while minor compounds were caffeic acid, apigenin, hesperetin and naringenin. Neoponcirin and biochanin A were identified for the first time in the Mentha genus.

Activation of the silent secondary metabolite production by introducing neomycin-resistance in a marine-derived Penicillium purpurogenum G59.

Introduction of neomycin-resistance into a marine-derived, wild-type Penicillium purpurogenum G59 resulted in activation of silent biosynthetic pathways for the secondary metabolite production. Upon treatment of G59 spores with neomycin and dimethyl sulfoxide (DMSO), a total of 56 mutants were obtained by single colony isolation. The acquired resistance of mutants to neomycin was testified by the resistance test. In contrast to the G59 strain, the EtOAc extracts of 28 mutants inhibited the human cancer K562 cells, indicating that the 28 mutants have acquired the capability to produce bioactive metabolites. HPLC-photodiode array detector (PDAD)-UV and HPLC-electron spray ionization (ESI)-MS analyses further indicated that diverse secondary metabolites have been newly produced in the bioactive mutant extracts. Followed isolation and characterization demonstrated that five bioactive secondary metabolites, curvularin (1), citrinin (2), penicitrinone A (3), erythro-23-O-methylneocyclocitrinol (4) and 22E-7α-methoxy-5α,6α-epoxyergosta-8(14),22-dien-3β-ol (5), were newly produced by a mutant, 4-30, compared to the G59 strain. All 1–5 were also not yet found in the secondary metabolites of other wild type P. purpurogenum strains. Compounds 1–5 inhibited human cancer K562, HL-60, HeLa and BGC-823 cells to varying extents. Both present bioassays and chemical investigations demonstrated that the introduction of neomycin-resistance into the marine-derived fungal G59 strain could activate silent secondary metabolite production. The present work not only extended the previous DMSO-mediated method for introducing drug-resistance in fungi both in DMSO concentrations and antibiotics, but also additionally exemplified effectiveness of this method for activating silent fungal secondary metabolites. This method could be applied to other fungal isolates to elicit their metabolic potentials to investigate secondary metabolites from silent biosynthetic pathways.

Determination of phenolic acids and a flavonoid in Eleusine coracana (L.) by semi-preparative HPLC photo diode array detector

Semi preparative HPLC procedure is proposed for the determination of six phenolic acids and one flavonoid in Eleusine coracana (L.) with gradient elution and photodiode array detection. The influence of composition of the mobile phase concentration of the mix modifier and temperature on the separation of gallic acid, p-hydroxybenzoic, vanillic, caffeic, ferulic, and cinnamic acids and quercetin for 90 min is studied. The procedure was applied for the separation of phenolic compounds in methanolic extracts of Eleusine coracana (L.). The lower limits of quantification of phenolic compounds and the flavonoid are 0.050–0.150 μg/mL.

Optimization and validation of an HPLC-photodiode array detector method for determination of organic acids in vinegar.

A novel isocratic RP-HPLC method with UV photodiode array detection for the determination of seven organic acids in vinegar samples was developed and optimized. Samples were analyzed on a C18 (150 × 4.6 mm id, 5 μm) analytical column. Methanol-0.010 M sodium dihydrogen phosphate buffer adjusted with H3PO4 to pH 2.80 (2 + 98, v/v), was used as the mobile phase. The column oven temperature was optimized at 23.0°C, the flow rate was 0.80 mL/min, and the detection wavelength was 210 nm. Matrix-matched calibration curves were prepared for all analytes, and the correlation coefficients were greater than 0.99. LOD and LOQ ranged from 0.10 to 10.0 and 0.30 to 30.0 μg/mL, respectively. The results for interday and intraday precision and accuracy fell within the ranges specified. Vinegar samples were quantified by the standard addition method. The main advantages of this method are its selectivity, which is one of the main weaknesses of most methods when determining organic acids in complex matrixes, and its simplicity since little sample preparation is needed. Moreover, it is safe and inexpensive with low organic solvent usage.

Effect of consuming hi-oleic peanuts on adiposity and cardiometabolic health

Effect of consuming hi-oleic peanuts on adiposity and cardiometabolic health

Novel molecularly imprinted stir bar sorptive extraction based on an 8-electrode array for preconcentration of trace exogenous estrogens in meat

A novel 8-electrode array as stir bar was designed for selective extraction of trace level exogenous estrogens from food samples, followed by liquid desorption and HPLC-photodiode array detection. The array consisted of 8 screen-printed electrodes and each electrode was modified with Fe3O4@meso-/macroporous TiO2 microspheres and molecularly imprinted film (m-TiMIF). The fabrication of the imprinted film coating was very simple without organic solvents and chemical grafting. Both bisphenol A (BPA) and diethylstilbestrol (DES) were employed as templates in m-TiMIF fabrication in order to enrich both targets simultaneously. Interestingly, the imprinted stir bar array showed higher extraction capacity and selectivity for BPA and DES than the non-imprinted counterpart. Meanwhile, it exhibited fast adsorption and desorption kinetics due to increased mass transport in the ultra-thin film. Importantly, the m-TiMIF coating was robust enough for at least 20 uses without obvious alteration in extraction performance. The main parameters affecting the extraction efficiency, including stir speeding, sample pH, ionic strength, extraction time, desorption solvent and time, were optimized. Under optimal experimental conditions, the limits of detection (S/N=3) of the developed method were 0.28 and 0.47μgL−1 for BPA and DES respectively, with enrichment factors of 32.6 and 52.8-fold. The linear ranges were 3.0–1500μgL−1 and 4.0–1500μgL−1 for BPA and DES, respectively. The m-TiMIF-coating conferred better recovery and selectivity, compared with the commercial stir bar coating. The new method was successfully applied to assess BPA and DES in pork and chicken samples with satisfactory recovery.