Publications by authors named "Bahruddin Saad"

67 Publications

Removal of 4-chloro-2-methylphenoxyacetic acid from water by MIL-101(Cr) metal-organic framework: kinetics, isotherms and statistical models.

R Soc Open Sci 2021 Jan 13;8(1):201553. Epub 2021 Jan 13.

Department of Geography, Faculty of Earth and Environmental Science, Kano University of Science and Technology, Wudil, 3244 Kano Postal, Nigeria.

Effective removal of 4-chloro-2-methylphenoxyacetic acid (MCPA), an emerging agrochemical contaminant in water with carcinogenic and mutagenic health effects has been reported using hydrothermally synthesized MIL-101(Cr) metal-organic framework (MOF). The properties of the MOF were ascertained using powdered X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, thermal gravimetric analysis (TGA), field emission scanning electron microscopy (FESEM) and surface area and porosimetry (SAP). The BET surface area and pore volume of the MOF were 1439 m g and 0.77 cm g, respectively. Artificial neural network (ANN) model was significantly employed for the accurate prediction of the experimental adsorption capacity ( ) values with minimal error. A rapid removal of the pollutant (99%) was recorded within short time (approx. 25 min), and the reusability of the MOF (20 mg) was achieved up to six cycles with over 90% removal efficiency. The kinetics, isotherm and thermodynamics of the process were described by the pseudo-second-order, Freundlich and endothermic adsorption, respectively. The adsorption process is spontaneous based on the negative Gibbs free energy values. The significant correlation between the experimental findings and simulation results suggests the great potential of MIL-101(Cr) for the remediation of MCPA from water matrices.
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http://dx.doi.org/10.1098/rsos.201553DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7890509PMC
January 2021

A simple and efficient sequential electrokinetic and hydrodynamic injections in micellar electrokinetic chromatography method for quantification of anticancer drug 5-fluorouracil and its metabolite in human plasma.

Biomed Chromatogr 2021 May 20;35(5):e5050. Epub 2020 Dec 20.

Integrative and Regenerative Medicine Clusters, Advanced Medical and Dental Institute, Universiti Sains Malaysia, Bertam, Penang, Malaysia.

A simple and sensitive preconcentration strategy using sequential electrokinetic and hydrodynamic injection modes in micellar electrokinetic chromatography with diode array detection was developed and applied for the separation and determination of anticancer agent, 5-fluorouracil and its metabolite, 5-fluoro-2'-deoxyuridine, in human plasma. Sequential injection modes with increased analyte loading capacity using the anionic pseudo-stationary phase facilitated collection of the dispersed neutral and charged analytes into narrow zones and improved sensitivity. Several important parameters affecting sample enrichment performance were evaluated and optimized in this study. Under the optimized experimental conditions, 614- and 643-fold and 782- and 803-fold sensitivity improvement were obtained for 5-fluorouracil and its metabolite when compared with normal hydrodynamic and electrokinetic injection, respectively. The method has good linearity (1-1,000 ng/ml) with acceptable coefficient of determination (r  > 0.993), low limits of detection (0.11-0.14 ng/ml) and satisfactory analyte relative recovery (97.4-99.7%) with relative standard deviations of 4.6-9.3% (n = 6). Validation results as well as the application to analysis of human plasma samples from cancer patients demonstrate the applicability of the proposed method to clinical studies.
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http://dx.doi.org/10.1002/bmc.5050DOI Listing
May 2021

A Critical Review on Metal-Organic Frameworks and Their Composites as Advanced Materials for Adsorption and Photocatalytic Degradation of Emerging Organic Pollutants from Wastewater.

Polymers (Basel) 2020 Nov 10;12(11). Epub 2020 Nov 10.

Radiology and Medical Imaging Department, College of Applied Medical Sciences, Prince Sattam Bin Abduaziz University, Alkharj 11942, Saudi Arabia.

Water-borne emerging pollutants are among the greatest concern of our modern society. Many of these pollutants are categorized as endocrine disruptors due to their environmental toxicities. They are harmful to humans, aquatic animals, and plants, to the larger extent, destroying the ecosystem. Thus, effective environmental remediations of these pollutants became necessary. Among the various remediation techniques, adsorption and photocatalytic degradation have been single out as the most promising. This review is devoted to the compilations and analysis of the role of metal-organic frameworks (MOFs) and their composites as potential materials for such applications. Emerging organic pollutants, like dyes, herbicides, pesticides, pharmaceutical products, phenols, polycyclic aromatic hydrocarbons, and perfluorinated alkyl substances, have been extensively studied. Important parameters that affect these processes, such as surface area, bandgap, percentage removal, equilibrium time, adsorption capacity, and recyclability, are documented. Finally, we paint the current scenario and challenges that need to be addressed for MOFs and their composites to be exploited for commercial applications.
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http://dx.doi.org/10.3390/polym12112648DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7698011PMC
November 2020

Simultaneous Quantitative Assessment of Ochratoxin A, Patulin, 5-Hydroxymethylfurfural, and Bisphenol A in Fruit Drinks Using HPLC with Diode Array-Fluorimetric Detection.

Foods 2020 Nov 9;9(11). Epub 2020 Nov 9.

School of Chemical Sciences, Universiti Sains Malaysia, Penang 11800, Malaysia.

The analysis of regulated contaminants in fruit drinks often requires suitable validated and rapid analytical methods for cost-effective food control, and is of considerable interest among the fruit beverage industry. This study demonstrated a rapid and sensitive high-performance liquid chromatography approach for the simultaneous determination of ochratoxin A (OTA), patulin (PAT), 5-hydroxymethylfurfural (HMF), and bisphenol A (BPA) in various fruit drinks. The separations were achieved using a C18 core-shell column with both photo-diode array and fluorimetric detections connected in series. A gradient system consisting of methanol and 0.1% formic acid at a flow rate of 1.2 mL min, thermostated at 35 °C, provided fast elution with run time <9 min. Sample pretreatment was optimised to enable extraction of all analytes from fruit drink matrices. The optimised method was validated. Correlation coefficients of > 0.99 were achieved with detection limits of 0.5 ng mL (OTA), 1.1 ng mL (PAT), 7.9 ng mL (HMF), and 1.0 ng mL (BPA). Recoveries ranged from 82% to 99%. Good relative standard deviations for intraday retention times (≤3.54%) and peak area (≤3.5%) were achieved. The developed multi-contaminants analysis method was successfully applied to determine OTA, PAT, HMF, and BPA in various fruit drinks.
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http://dx.doi.org/10.3390/foods9111633DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7695309PMC
November 2020

Salting-out assisted liquid-liquid extraction coupled with high-performance liquid chromatography for the determination of vitamin D3 in milk samples.

R Soc Open Sci 2019 Aug 21;6(8):190952. Epub 2019 Aug 21.

School of Chemical Sciences, Universiti Sains Malaysia, 11800 Pulau Pinang, Malaysia.

In this study, salting-out assisted liquid-liquid extraction (SALLE) as a simple and efficient extraction technique followed by high-performance liquid chromatography (HPLC) was employed for the determination of vitamin D3 in milk samples. The sample treatment is based on the use of water-miscible acetonitrile as the extractant and acetonitrile phase separation under high-salt conditions. Under the optimum conditions, acetonitrile and ammonium sulfate were used as the extraction solvent and salting-out agent, respectively. The vitamin D3 extract was separated using Hypersil ODS (250x i.d 4.6 mm, 5 µm) HPLC column that was coupled with diode array detector. Vitamin D2 was used as internal standard (IS) to offset any variations in chromatographic conditions. The vitamin D3 and the IS were eluted in 18 min. Good linearity ( > 0.99) was obtained within the range of 25-600 ng g with the limit of detection of 15 ng g and limit of quantification of 25 ng g. The validated method was applied for the determination of vitamin D3 in milk samples. The recoveries for spiked samples were from 94.4 to 113.5%.
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http://dx.doi.org/10.1098/rsos.190952DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6731698PMC
August 2019

Electrochemically Modulated Liquid-Liquid Extraction for Sample Enrichment.

Anal Chem 2019 06 13;91(11):7466-7473. Epub 2019 May 13.

Laboratoire de Chimie Physique et Microbiologie pour les Matériaux et l'Environnement (LCPME) , UMR 7564, CNRS - Université de Lorraine , 405 rue de Vandoeuvre , Villers-lès-Nancy , F-54600 , France.

A new sample preparation method is proposed for the extraction of pharmaceutical compounds (Metformin, Phenyl biguanide, and Phenformin) of varied hydrophilicity, dissolved in an aqueous sample. When in contact with an organic phase, an interfacial potential is imposed by the presence of an ion, tetramethylammonium (TMA), common to each phase. The interfacial potential difference drives the transfer of ionic analytes across the interface and allows it to reach up to nearly 100% extraction efficiency and a 60-fold enrichment factor in optimized extraction conditions as determined by HPLC analysis.
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http://dx.doi.org/10.1021/acs.analchem.9b01674DOI Listing
June 2019

Molecularly imprinted silica gel incorporated with agarose polymer matrix as mixed matrix membrane for separation and preconcentration of sulfonamide antibiotics in water samples.

Talanta 2019 Jul 4;199:522-531. Epub 2019 Mar 4.

Integrative Medicine Cluster, Advanced Medical and Dental Institute, Universiti Sains Malaysia, Bertam,13200 Kepala Batas, Penang, Malaysia. Electronic address:

Molecularly imprinted silica gel (MISG) was incorporated through dispersion in agarose polymer matrix to form a mixed matrix membrane (MMM) and was applied for the determination of three sulfonamide antibiotic compounds (i.e. sulfamethoxazole (SMX), sulfamonomethoxine (SMM), and sulfadiazine (SDZ)) from environmental water samples. Several important microextraction conditions, such as type of desorption solvent, extraction time, amount of sorbent, sample volume, pH, and effect of desorption time, were comprehensively optimized. A preconcentration factors of ≥ 20 was achieved by the extraction of 12.5 mL of water samples using the developed method. This microextraction-HPLC method demonstrated good linearity (1-500 μg L) with a coefficient of determination (R) of 0.9959-0.9999, low limits of detection (0.06-0.17 μg L) and limits of quantification (0.20-0.56 μg L), good analyte recoveries (80-96%), and acceptable relative standard deviations (< 10%) under the optimized conditions. The method is systematically compared to those reported in the literature.
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http://dx.doi.org/10.1016/j.talanta.2019.02.096DOI Listing
July 2019

Thiol-functionalized magnetic carbon nanotubes for magnetic micro-solid phase extraction of sulfonamide antibiotics from milks and commercial chicken meat products.

Food Chem 2019 Mar 11;276:458-466. Epub 2018 Oct 11.

Division of Chemical Engineering, Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531, Japan.

Thiol-functionalized magnetic carbon nanotubes (TMCNTs) were employed as the sorbent in the magnetic micro-solid phase extraction (M-µ-SPE) of sulfonamide antibiotics (SAs) in water, milks and chicken meat products prior to high performance liquid chromatography-diode array detector (HPLC-DAD) analysis. The synthesized sorbent was characterized by several spectroscopic techniques. Optimum conditions were: 20 mg of TMCNTs at pH 4, 2 min extraction time, 10% addition of salt and 30 mL of sample volume. Under the optimized TMCNTs-M-µ-SPE and HPLC-DAD conditions, the method showed good linearity in the range of 0.1-500 µg L (r ≥ 0.9950), low limits of detection (0.02-1.5 µg L), good analytes recovery (80.7-116.2%) and acceptable RSDs (0.3-7.7%, n = 15). The method was applied to tap water (1), milks (15) and commercial chicken meat products (35), SAs were detected in five chicken meat samples (3.0-25.7 µg L). The method is critically compared to those reported in the literature.
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http://dx.doi.org/10.1016/j.foodchem.2018.10.044DOI Listing
March 2019

Determination of Biogenic Amines in Seawater Using Capillary Electrophoresis with Capacitively Coupled Contactless Conductivity Detection.

Molecules 2018 05 8;23(5). Epub 2018 May 8.

School of Chemical Sciences, Universiti Sains Malaysia, Penang 11800, Malaysia.

A rapid and green analytical method based on capillary electrophoresis with capacitively coupled contactless conductivity detection (C⁴D) for the determination of eight environmental pollutants, the biogenic amines (putrescine, cadaverine, spermidine, spermine, tyramine, 2-phenylamine, histamine and tryptamine), is described. The separation was achieved under normal polarity mode at 24 °C and 25 kV with a hydrodynamic injection (50 mbar for 5 s) and using a bare fused-silica capillary (95 cm length × 50 µm i.d.) (detection length of 10.5 cm from the outlet end of the capillary). The optimized background electrolyte consisted of 400 mM malic acid. C⁴D parameters were set at a fixed amplitude (50 V) and frequency (600 kHz). Under the optimum conditions, the method exhibited good linearity over the range of 1.0⁻100 µg mL (² ≥ 0.981). The limits of detection based on signal to noise (S/N) ratios of 3 and 10 were ≤0.029 µg mL. The method was used for the determination of seawater samples that were spiked with biogenic amines. Good recoveries (77⁻93%) were found.
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http://dx.doi.org/10.3390/molecules23051112DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6100306PMC
May 2018

Cyclodextrin based polymer sorbents for micro-solid phase extraction followed by liquid chromatography tandem mass spectrometry in determination of endogenous steroids.

J Chromatogr A 2018 Mar 20;1543:23-33. Epub 2018 Feb 20.

Anti-Doping Laboratory Qatar, Doha, Qatar.

Sorbents were prepared by cross-linking β-cyclodextrin (β-CD) using two different types of cross-linker units at variable reactant mole ratios. The resulting polymers containing β-CD were evaluated as sorbents in micro-solid phase extraction (μ-SPE) format for the extraction of the endogenous steroids testosterone (T), epitestosterone (E), androsterone (A), etiocholanolone (Etio), 5α-androstane-3α,17β-diol (5αAdiol) and 5β-androstane-3α,17β-diol (5βAdiol). The best sorbent (C1; cyclodextrin polymer) showed superior extraction characteristics compared with commercial sorbents (C18 and Bond Elut Plexa). Parameters influencing the extraction efficiency of the C1 sorbent such as extraction and desorption times, desorption solvent and volume of sample were investigated. The extracts were separated using a Hypersil Gold column (50 × 2.1 mm, 1.9 μm) under gradient elution coupled to a LC-MS/MS. The compounds were successfully separated within 8 min. The method offers good repeatability (RSD < 10%) and linearity (r > 0.995) were within the range of 1-200 ng mL for T and E, 250-4000 ng mL for A and Etio and 25-500 ng mL for 5αAdiol and 5βAdiol, respectively. The method was applied for the determination of steroid profile of urine from volunteers.
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http://dx.doi.org/10.1016/j.chroma.2018.02.032DOI Listing
March 2018

Salting-out assisted liquid-liquid extraction coupled with hydrophilic interaction chromatography for the determination of biguanides in biological and environmental samples.

J Chromatogr B Analyt Technol Biomed Life Sci 2018 Jan 9;1073:51-59. Epub 2017 Dec 9.

School of Chemical Sciences, Universiti Sains Malaysia, 11800 Penang, Malaysia; Fundamental & Applied Science Department, Universiti Technologi PETRONAS, 32601 Seri Iskandar, Perak Darul Ridzuan, Malaysia.

A new salting-out assisted liquid-liquid extraction (SALLE) sample preparation method for the determination of the polar anti-diabetic biguanide drugs (metformin, buformin and phenformin) in blood plasma, urine and lake water samples were developed. The SALLE was performed by mixing samples (plasma (0.2mL), urine or lake water (1.0mL)) with acetonitrile (0.4mL for plasma, 0.5mL for urine or lake water), sodium hydroxide powder was then added for the phase separation. The effects of type of salting-out reagent, type of extraction solvent, volumes of acetonitrile and sample, amount of sodium hydroxide, vortexing and centrifugation times on the extraction efficiency were investigated. The upper layer, containing the biguanides, was directly injected into a HPLC unit using ZIC-HILIC column (150mm×2.1mm×3.5μm) and was detected at 236nm. The method was validated and calibration curves were linear with r>0.99 over the range of 20-2000μgL for plasma and 5-2000μgL for urine and lake water samples. The limits of detection were in the range (3.8-5.6)μgL, (0.8-1.5)μgL and (0.3-0.8)μgL for plasma, urine and lake water, respectively. The accuracies in the three matrices were within 87.3-103%, 87.4-109%, 82.2-109% of the nominal concentration for metformin, buformin and phenformin, respectively. The relative standard deviation for inter- and intra -day precision were in the range of 1.0-17% for all analytes in the three matrices.
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http://dx.doi.org/10.1016/j.jchromb.2017.12.013DOI Listing
January 2018

Liquid Chromatographic Analysis of α-Dicarbonyls Using Girard-T Reagent Derivatives.

J Chromatogr Sci 2017 Nov;55(10):1043-1050

Fundamental and Applied Science Department, Universiti Teknologi Petronas, 33610 Seri Iskandar, Perak Darul Ridzuan, Malaysia.

The measurement of α-dicarbonyls and other degradation products of sugars has become important in view of their toxicity. Although there are several methods used for their analysis, most require long reaction times to form UV absorbing or fluorescent derivatives and the nonpolar nature of commonly used derivatives necessitates relatively high concentrations of organic solvents for elution in reverse phase liquid chromatography. The present method describes the use of Girard-T reagent in a simple, one step derivatization of α-dicarbonyls and conjugated aldehydes and analysis using ion-pair reverse phase liquid chromatography. The limit of detection was in the range of 0.06-0.09 μM (4-12 ng/mL) for glyoxal, methylglyoxal, 3-deoxyglucosone and 5-hydroxymethylfurfural with good linear response and reproducibility using UV detection. The hydrazone derivatives were stable for several days in solution. The method was used to study degradation of several sugars and quantification of the target α-dicarbonyls and 5-hydroxymethylfurfural in several soft drinks.
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http://dx.doi.org/10.1093/chromsci/bmx073DOI Listing
November 2017

Evaluation of extraction methods for the identification of proteins from date palm (Phoenix dactylifera L.) seed and flesh.

Prep Biochem Biotechnol 2017 Nov 31;47(10):998-1007. Epub 2017 Aug 31.

d Analytical Biochemistry Research Centre (ABrC) , Universiti Sains Malaysia (USM) , Minden , Pulau Pinang , Malaysia.

Date fruits are well known to be very nutritious. Nevertheless, the protein contents of the fruit, particularly the seed and flesh, are still understudied, largely due to their difficult physical characteristics. This study was conducted to compare three different protein extraction methods which were the trichloroacetic acid (TCA)-acetone (TCA-A), phenol (Phe), and TCA-acetone-phenol (TCA-A-Phe), and to perform proteomic analysis on date palm seed and flesh. Phe extraction method showed the highest protein yields for both seed (8.26 mg/g) and flesh (1.57 mg/g). Through sodium dodecyl sulfate-polyacrylamide gel electrophoresis, Phe, and TCA-A-Phe extraction methods were shown to be efficient in removing interfering compounds and gave well-resolved bands over a wide range of molecular weights. Following liquid chromatography-tandem mass spectrometry analysis, about 50-64% of extracted proteins were identified with known functions including those involved in glycolysis, Krebs cycle, defense, and storage. Phe protein extraction method was proven to be the optimal method for date flesh and seed.
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http://dx.doi.org/10.1080/10826068.2017.1365250DOI Listing
November 2017

Vortex-assisted liquid-liquid-liquid microextraction followed by high performance liquid chromatography for the simultaneous determination of fourteen phenolic acids in honey, iced tea and canned coffee drinks.

Talanta 2017 Nov 16;174:428-435. Epub 2017 Jun 16.

School of Chemical Sciences, Universiti Sains Malaysia, 11800 Penang, Malaysia. Electronic address:

A vortex-assisted liquid-liquid-liquid microextraction method followed by high performance liquid chromatography-diode array detection for the determination of fourteen phenolic acids (cinnamic, m-coumaric, chlorogenic, syringic, ferulic, o-coumaric, p-coumaric, vanillic, p-hydroxybenzoic, caffeic, 2, 4-dihydroxybenzoic, sinapic, gentisic and gallic acids) in honey, iced tea and canned coffee drink samples has been developed. The separation was achieved using a Poroshell 120-EC-C18 column under a gradient elution at a flow rate of 0.6mLmin and mobile phase composed of methanol and acetic acid (1%, v/v). Under the optimum chromatographic conditions, the fourteen phenolic acids were separated in less than 32min. The extraction was performed using a small volume (400µL) of ternary organic solvents (1-pentanol, propyl acetate and 1-hexanol) dispersed into the aqueous sample (10mL) and assisted by vortex agitation (2500rpm for 45s), the analytes were next back-extracted from the organic solvent using 0.02M KOH (40µL) with vortex speed and time of 2500rpm and 60s, respectively. Under these conditions, enrichment factors of 30-193-fold were achieved. The limits of detection (LODs) were 0.05-0.68µgL. Recoveries in honey, iced tea and canned coffee drinks were in the range 72.2-112%. The method was successfully applied for the determination of the phenolic acids in honey, iced tea and canned coffee drinks.
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http://dx.doi.org/10.1016/j.talanta.2017.06.039DOI Listing
November 2017

Determination of aflatoxin M in milk and dairy products using high performance liquid chromatography-fluorescence with post column photochemical derivatization.

J Chromatogr A 2017 Aug 19;1510:51-56. Epub 2017 Jun 19.

School of Chemical Sciences, Universiti Sains Malaysia, 11800, Pulau Pinang, Malaysia. Electronic address:

The determination of aflatoxin M in milk using high performance liquid chromatography with photochemical post-column derivatization and fluorescence detection is described. The samples were first extracted and clean-up using the immunoaffinity AFLATEST column originally targeted for aflatoxins B, B, G and G. The separation of aflatoxin M were performed using C18 Hypersil gold (150mm×4.6mm, 5μm) column at 40°C under isocratic elution. Fluorescence detector (FLD) was set at 360nm and 440nm as excitation and emission, respectively. The use of methanol to replace acetonitrile as the mobile phase resulted in ∼67% peak area enhancement of AFM. The limit of detection (LOD) and quantification (LOQ) of the analytical method after post-column derivatization without evaporation/reconstitution with mobile phase was 0.0085μgL and 0.025μgL respectively. However, LOD and LOQ improved to 0.002 and 0.004μgL respectively with the addition of evaporation/reconstitution step. The method was statistically validated, showing linear response (R>0.999), good recoveries (85.2-107.0%) and relative standard deviations (RSD) were found to be ≤7%. The proposed method was applied to determine AFM contamination in various types of milk and milk products. Only 2 samples were contaminated with aflatoxin M (10% incidence). However, the contamination level is below the Malaysian and European legislation limits.
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http://dx.doi.org/10.1016/j.chroma.2017.06.054DOI Listing
August 2017

Rapid ultrasound assisted emulsification micro-solid phase extraction based on molecularly imprinted polymer for HPLC-DAD determination of bisphenol A in aqueous matrices.

Talanta 2017 Aug 4;171:242-249. Epub 2017 May 4.

Faculty of Applied Sciences, Universiti Teknologi MARA, 40450 Shah Alam, Selangor Darul Ehsan, Malaysia.

Molecularly imprinted polymer (MIP) was employed as sorbent in ultrasound assisted emulsification molecularly imprinted polymer micro-solid phase extraction (USAE-MIP-µ-SPE) of bisphenol A (BPA) in water, beverages and the aqueous liquid in canned foods prior to high performance liquid chromatography-diode array detector (HPLC-DAD) analysis. Several effective variables, such as types of emulsification solvent and its volume, types of desorption solvent and its volume, salting out effect, pH of sample solution, mass of sorbent, extraction and desorption time, and sample volume, were optimized comprehensively. Under the optimized USAE-MIP-µ-SPE and HPLC-DAD conditions, the method demonstrated good linearity over the range of 0.5-700μgL with a coefficient determination of R=0.9973, low limit of detection (0.07μgL), good analyte recoveries (82.2-118.9%) and acceptable RSDs (0.7-14.2%, n=3) with enrichment factor of 49. The method was applied to thirty samples of drinking water, mineral water, river water, lake water, as well as beverages and canned foods, the presence of BPA was identified in four samples. The proposed method showed good selectivity and reusability for extraction of BPA, and hence the USAE-MIP-µ-SPE is rapid, simple, cost effective and environmentally friendly.
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http://dx.doi.org/10.1016/j.talanta.2017.05.006DOI Listing
August 2017

Ion-pair vortex assisted liquid-liquid microextraction with back extraction coupled with high performance liquid chromatography-UV for the determination of metformin in plasma.

Talanta 2016 Dec 26;161:398-404. Epub 2016 Aug 26.

School of Chemical Sciences, Universiti Sains Malaysia, 11800 Penang, Malaysia.

A new sample preparation method, ion-pair vortex assisted liquid-liquid microextraction (VALLME-BE), for the determination of a highly polar anti-diabetic drug (metformin) in plasma sample was developed. The VALLME-BE was performed by diluting the plasma in borate buffer and extracted to 150µL 1-octanol containing 0.2M di-(2-ethylhexyl)phosphoric acid as intermediate phase. The drug was next back-extracted into 20µL of 0.075M HCl solution. The effects of pH, ion-pair concentration, type of organic solvent, volume of extraction phases, ionic strength, vortexing and centrifugation times on the extraction efficiency were investigated. The optimum conditions were at pH 9.3, 60s vortexing and 2min centrifugation. The microextract, contained metformin and buformin (internal standard), was directly injected into a HPLC unit using C1 column (250mm×4.6mm×10µm) and detected at 235nm. The method was validated and calibration curve was linear with r>0.99 over the range of 20-2000µgL. The limits of detection and quantitation were 1.4 and 4.1µgL, respectively. The accuracy was within 94.8-108% of the nominal concentration. The relative standard deviation for inter- and intra-day precision was less than 10.8%. The method was conveniently applied for the determination of metformin in plasma samples.
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http://dx.doi.org/10.1016/j.talanta.2016.08.067DOI Listing
December 2016

Vortex- and CO2 -gas-assisted liquid-liquid microextraction with salt addition for the high-performance liquid chromatographic determination of furanic compounds in concentrated juices and dried fruits.

J Sep Sci 2016 Mar 2;39(5):947-55. Epub 2016 Feb 2.

School of Chemical Sciences, Universiti Sains Malaysia, Minden, Penang, Malaysia.

A novel microextraction method based on vortex- and CO2 -assisted liquid-liquid microextraction with salt addition for the isolation of furanic compounds (5-hydroxymethyl-2-furaldehyde, 5-methyl-2-furaldehyde, 2-furaldehyde, 3-furaldehyde, 2-furoic and 3-furoic acids) was developed. Purging the sample with CO2 was applied after vortexing to enhance the phase separation and mass transfer of the analytes. The optimum extraction conditions were: extraction solvent (volume), propyl acetate (125 μL); sample pH, 2.4; vortexing time, 45 s; salt concentration, 25% w/v and purging time, 5 min. The analytes were separated using an ODS Hypersil C18 column (250×4.6 mm i.d, 5 μm) under gradient flow. The proposed method showed good linearities (r(2) >0.999), low detection limits (0.08-1.9 μg/L) and good recoveries (80.7-122%). The validated method was successfully applied for the determination of the furanic compounds in concentrated juice (mango, date, orange, pomegranate, roselle, mangosteen and soursop) and dried fruit (prune, date and apricot paste) samples.
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http://dx.doi.org/10.1002/jssc.201501109DOI Listing
March 2016

Vortex-assisted liquid-liquid-liquid microextraction (VALLLME) technique: A new microextraction approach for direct liquid chromatography and capillary electrophoresis analysis.

Talanta 2015 Oct 11;143:394-401. Epub 2015 May 11.

School of Chemical Sciences, Universiti Sains Malaysia, 11800 Penang, Malaysia. Electronic address:

A new, rapid and sensitive microextraction technique named vortex-assisted liquid-liquid-liquid microextraction (VALLLME) is proposed. The complete extraction process involves two steps. First, a vortex-assisted liquid-liquid microextraction (VALLME) procedure was used to extract the analytes from a relatively large volume of sample (donor phase) to a small volume of organic solvent (intermediate phase). Next, a micro-vortex-assisted liquid-liquid extraction (µ-VALLE) was used to extract the target analytes from the intermediate phase to a smaller volume of aqueous solution (acceptor phase). The final extract (acceptor phase) can be directly injected into the high performance liquid chromatography or capillary electrophoresis units without any further treatments. The selection of the intermediate phase and the manipulation of pH are key parameters that ensure good extraction efficiency of the technique. The proposed technique has been successfully applied for the determination of carvedilol (used as model analyte) in biological fluid samples. The optimum extraction conditions were: toluene as intermediate phase (150 μL); pH of the donor phase, 9.5; vortex time of the VALLME, 45 s (maximum speed, 2500 rpm); 0.1M HCl (15 μL) as acceptor phase; vortexing time of the µ-VALLME, 75 s (maximum stirring speed, 2500 rpm) and salt concentration in the donor phase, 5% (w/v). Under these conditions, enrichment factors of 51- and 418-fold for VALLME step and VALLLME procedure, respectively, were achieved.
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http://dx.doi.org/10.1016/j.talanta.2015.05.011DOI Listing
October 2015

Determination of α-ketoglutaric and pyruvic acids in urine as potential biomarkers for diabetic II and liver cancer.

Bioanalysis 2015 ;7(6):713-23

School of Chemical Sciences, Universiti Sains Malaysia, 11800 Minden, Penang, Malaysia.

Background: A simple and sensitive hollow fiber-liquid phase microextraction with in situ derivatization method was developed for the determination of α-ketoglutaric (α-KG) and pyruvic acids (PA) in small-volume urine samples. 2,4,6-trichloro phenyl hydrazine was used as derivatization agent.

Results: Under the optimum extraction conditions, enrichment factors of 742 and 400 for α-KG and PA, respectively, were achieved. Calibration curves were linear over the range 1 to 1000 ng/ml (r(2) ≥ 0.998). Detection and quantitation limits were 0.03 and 0.02, and 0.10 and 0.05 ng/ml for α-KG and PA, respectively.

Conclusion: The concentrations in diabetic II and liver cancer samples were significantly lower than those from healthy people, showing their potential as biomarkers for these diseases.
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http://dx.doi.org/10.4155/bio.14.307DOI Listing
January 2016

Sequential hollow-fiber liquid phase microextraction for the determination of rosiglitazone and metformin hydrochloride (anti-diabetic drugs) in biological fluids.

Talanta 2015 Jan 20;131:590-6. Epub 2014 Aug 20.

School of Chemical Sciences, Universiti Sains Malaysia, 11800 Minden, Penang, Malaysia.

A new analytical method for the simultaneous determination of the antidiabetic drugs rosiglitazone (ROS) and metformin hydrochloride (MH) with marked differences in their affinity towards organic solvents (log P of 2.4 and -1.43, respectively) was developed. Prior to the HPLC separation, the drugs were subjected to a sequential hollow fiber liquid phase microextraction (HF-LPME) procedure. Two sequential HF-LPME approaches were considered, the preferred one involves the use of two vials containing solution mixtures for the extraction of ROS (vial 1) and MH (vial 2), respectively, but using the same fiber and acceptor phase. Important parameters that affect the extraction efficiency such as extracting solvent, donor phase conditions, HCl concentration, agitation, extraction time, addition of salt, etc. were studied. Under the optimum conditions, good enrichment factors (EF, 471 and 86.6 for ROS and MH, respectively) were achieved. Calibration curves were linear over the range 1-500 (r(2)=0.998) and 5-2500 ng mL(-1) (r(2)=0.999) for ROS and MH, respectively. The relative standard deviation values (RSD%) for six replicates were below 8.4%. Detection and quantitation limits based on S/N ratio of 3 and 10 were 0.12, 1.0 and 0.36, 3.0 ng mL(-1) for ROS and MH, respectively. The proposed method is simple, sensitive and opens up new opportunities for the microextraction of analytes with contrasting properties.
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http://dx.doi.org/10.1016/j.talanta.2014.08.037DOI Listing
January 2015

UPLC method for the determination of vitamin E homologues and derivatives in vegetable oils, margarines and supplement capsules using pentafluorophenyl column.

Talanta 2014 Dec 15;130:299-306. Epub 2014 Jul 15.

Laboratoire d'Etude et de Recherche sur le MAteriau Bois, Faculté des Sciences et Techniques, Nancy-Université, Bld des Aiguillettes, F-54500 Vandoeuvre-lès-Nancy, France.

A sensitive and rapid reversed-phase ultra performance liquid chromatographic (UPLC) method for the simultaneous determination of tocopherols (α-, β-, γ-, δ-), tocotrienols (α-, β-, γ-, δ-), α-tocopherol acetate and α-tocopherol nicotinate is described. The separation was achieved using a Kinetex pentafluorophenyl (PFP) column (150 × 2.1mm, 2.6 µm) with both photodiode array (PDA) and fluorescence (FL) detectors that were connected in series. Column was thermostated at 42°C. Under a gradient system consisting of methanol and water at a constant flow rate of 0.38 mL min(-1), all the ten analytes were well separated in less than 9.5 min. The method was validated in terms of linearity, limits of detection and quantitation, precision and recoveries. Calibration curves of the ten compounds were well correlated (r(2)>0.999) within the range of 100 to 25,000 μg L(-1) for α-tocopherol acetate and α-tocopherol nicotinate, 10 to 25,000 μg L(-1) for α-tocotrienol and 5 to 25,000 μg L(-1) for the other components. The method is simple and sensitive with detection limits (S/N, 3) of 1.0 to 3.0 μg L(-1) (FL detection) and 30 to 74 μg L(-1) (PDA detection). Relative standard deviations for intra- and inter-day retention times (<1%) and peak areas (≤ 4%) were obtained. The method was successfully applied to the determination of vitamin E in vegetable oils (extra virgin olive, virgin olive, pomace olive, blended virgin and refined olive, sunflower, soybean, palm olein, carotino, crude palm, walnut, rice bran and grape seed), margarines and supplements.
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http://dx.doi.org/10.1016/j.talanta.2014.07.021DOI Listing
December 2014

Development and Validation of a Stability-Indicating Capillary Electrophoresis Method for the Determination of Zolpidem Tartrate in Tablet Dosage Form with Positive Confirmation using 2D- and 3D-DAD Fingerprints.

Sci Pharm 2014 Apr-Jun;82(2):341-56. Epub 2014 Feb 27.

Pharmacy Program, Batterjee Medical College for Science and Technology (BMC), 21442 Jeddah, Kingdom of Saudi Arabia.

The aim of the current study was to develop a simple, precise, and accurate capillary zone electrophoresis method for the determination of zolpidem tartrate in tablet dosage form. Separation was conducted in normal polarity mode at 25°C, 22 kV, using hydrodynamic injection for 10 s. Separation was achieved using a background electrolyte of 20 mM disodium hydrogen phosphate adjusted with phosphoric acid (85%), pH at 5.50, and detection at 254 nm. Using the above optimized conditions, complete determination took place in less than 3 min using amiloride HCl as the internal standard. The method was linear over the range of 3-1000 μg mL(-1) with a correlation coefficient of 0.9999. Forced degradation studies were conducted by introducing a sample of zolpidem tartrate standard and pharmaceutical sample solutions to different forced degradation conditions, being neutral (water), basic (0.1 M NaOH), acidic (0.1 M HCl), oxidative (10% H2O2), temperature (60°C in oven for 3 days), and photolytic (exposure to UV light at 254 nm for 2 h). Degradation products resulting from the stress studies did not interfere with the detection of zolpidem tartrate and the assay can be considered stability-indicating.
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http://dx.doi.org/10.3797/scipharm.1401-11DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4065127PMC
June 2014

Vortex-assisted liquid-liquid microextraction coupled with high performance liquid chromatography for the determination of furfurals and patulin in fruit juices.

Talanta 2014 Mar 4;120:47-54. Epub 2013 Dec 4.

School of Chemical Sciences, Universiti Sains Malaysia, 11800 Minden, Penang, Malaysia; Doping Control Centre, Universiti Sains Malaysia, 11800 Minden, Penang, Malaysia. Electronic address:

A fast and simple solvent microextraction technique using salting out-vortex-assisted liquid-liquid microextraction (salting out-VALLME) was developed for the extraction of furfurals (2-furfural (2-F), 3-furfural (3-F), 5-methylfurfural (5-MF) and 5-hydroxymethylfurfural (5-HMF)) and patulin (PAT) in fruit juice samples. The optimum extraction conditions for 5 mL sample were: extraction solvent, 1-hexanol; volume of extractant, 200 µL; vortex time, 45 s; salt addition, 20%. The simultaneous determination of the furfurals and PAT were investigated using high performance liquid chromatography coupled with diode array detector (HPLC-DAD). The separation was performed using ODS Hypersil C18 column (4.6 mm i.d × 250 mm, 5 μm) under gradient elution. The detection wavelengths used for all compounds were 280 nm except for 3-F (210 nm). The furfurals and PAT were successfully separated in less than 9 min. Good linearities (r(2)>0.99) were obtained within the range 1-5000 μg L(-1) for all compounds except for 3-F (10-5000 µg L(-1)) and PAT (0.5-100 μg L(-1)). The limits of detection (0.28-3.2 µg L(-1)) were estimated at S/N ratio of 3. The validated salting out-VALLME-HPLC method was applied for the analysis of furfurals and PAT in fruit juice samples (apple, mango and grape).
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http://dx.doi.org/10.1016/j.talanta.2013.11.081DOI Listing
March 2014

Micro-solid phase extraction with liquid chromatography-tandem mass spectrometry for the determination of aflatoxins in coffee and malt beverage.

Food Chem 2014 Mar 19;147:287-94. Epub 2013 Sep 19.

School of Chemical Sciences, Universiti Sains Malaysia, 11800 Penang, Malaysia.

A single step extraction-cleanup procedure using porous membrane-protected micro-solid phase extraction (μ-SPE) in conjunction with liquid chromatography-tandem mass spectrometry for the extraction and determination of aflatoxins (AFs) B1, B2, G1 and G2 from food was successfully developed. After the extraction, AFs were desorbed from the μ-SPE device by ultrasonication using acetonitrile. The optimum extraction conditions were: sorbent material, C8; sorbent mass, 20mg; extraction time, 90 min; stirring speed, 1,000 rpm; sample volume, 10 mL; desorption solvent, acetonitrile; solvent volume, 350 μL and ultrasonication period, 25 min without salt addition. Under the optimum conditions, enrichment factor of 11, 9, 9 and 10 for AFG2, AFG1, AFB2 and AFB1, respectively were achieved. Good linearity and correlation coefficient was obtained over the concentration range of 0.4-50 ng g(-1) (r(2) 0.9988-0.9999). Good recoveries for AFs ranging from 86.0-109% were obtained. The method was applied to 40 samples involving malt beverage (19) and canned coffee (21). No AFs were detected in the selected samples.
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http://dx.doi.org/10.1016/j.foodchem.2013.09.049DOI Listing
March 2014

Rapid tea catechins and caffeine determination by HPLC using microwave-assisted extraction and silica monolithic column.

Food Chem 2014 Mar 3;147:262-8. Epub 2013 Oct 3.

School of Chemical Sciences, Universiti Sains Malaysia, 11800 Minden, Penang, Malaysia. Electronic address:

A rapid reversed-phase high performance liquid chromatographic method using a monolithic column for the determination of eight catechin monomers and caffeine was developed. Using a mobile phase of water:acetonitrile:methanol (83:6:11) at a flow rate of 1.4 mL min(-1), the catechins and caffeine were isocratically separated in about 7 min. The limits of detection and quantification were in the range of 0.11-0.29 and 0.33-0.87 mg L(-1), respectively. Satisfactory recoveries were obtained (94.2-105.2 ± 1.8%) for all samples when spiked at three concentrations (5, 40 and 70 mg L(-1)). In combination with microwave-assisted extraction (MAE), the method was applied to the determination of the catechins and caffeine in eleven tea samples (6 green, 3 black and 2 oolong teas). Relatively high levels of caffeine were found in black tea, but higher levels of the catechins, especially epigallocatechin gallate (EGCG) were found in green teas.
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http://dx.doi.org/10.1016/j.foodchem.2013.09.131DOI Listing
March 2014

Hollow fiber liquid phase microextraction with in situ derivatization for the determination of trace amounts of metformin hydrochloride (anti-diabetic drug) in biological fluids.

J Chromatogr B Analyt Technol Biomed Life Sci 2013 Dec 14;941:123-30. Epub 2013 Oct 14.

School of Chemical Sciences, Universiti Sains Malaysia, 11800 Penang, Malaysia.

A three phase hollow fiber liquid-phase microextraction with in situ derivatization (in situ HF-LPME) followed by high-performance liquid chromatography-ultraviolet detection (HPLC-UV) method was developed for the trace determination of metformin hydrochloride (MH) in biological fluids. A new derivatization agent pentafluorobenzoyl chloride (PFBC) was used. Several parameters that affect the derivatization and extraction efficiency were studied and optimized (i.e., type of organic solvent, volume of NaOH (4M) and derivatization agent in the donor phase, acceptor phase (HCl) concentration, stirring speed, temperature, time and salt addition). Under the optimum conditions (organic solvent, dihexyl ether; volume of NaOH (4M) and derivatization agent (10mg PFBC in 1mL acetonitrile) in the donor phase, 600 and100μL, respectively; acceptor phase, 100mM HCl (10μL); stirring speed, 300rpm; extraction time, 30min; derivatization temperature, 70°C; without addition of salt) an enrichment factor of 210-fold was achieved. Good linearity was observed over the range of 1-1000ngmL(-1) (r(2)=0.9998). The limits of detection and quantitation were 0.56 and 1.68ngmL(-1), respectively. The proposed method has been applied for the determination of MH in biological fluids (plasma and urine) and water samples. Prior to the microextraction treatment of plasma samples, deproteinization step using acetonitrile was conducted. The proposed method is simple, rapid, sensitive and suitable for the determination of MH in a variety of samples.
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http://dx.doi.org/10.1016/j.jchromb.2013.10.007DOI Listing
December 2013

Capillary electrophoresis with capacitively coupled contactless conductivity detection for the determination of cis/trans isomers of octadec-9-enoic acid and other long chain fatty acids.

J Chromatogr A 2013 May 16;1290:82-90. Epub 2013 Mar 16.

School of Chemical Sciences, Universiti Sains Malaysia, 11800 Penang, Malaysia.

A capillary electrophoresis (CE)-capacitively coupled contactless conductivity detection (C(4)D) method for the simultaneous separation of eleven underivatized fatty acids (FAs), namely, lauric, myristic, tridecanoic (internal standard), pentadecanoic, palmitic, stearic, oleic, elaidic, linoleic, linolenic and arachidic acids is described. The separation was carried out in normal polarity mode at 20 °C, 30 kV and using hydrodynamic injection (50 mbar for 1 s). The separation was achieved in a bare fused-silica capillary (70 cm × 75 μm i.d.) using a background electrolyte of methyl-β-cyclodextrin (~6 mM) and heptakis-(2,3,6-tri-O-methyl)-β-cyclodextrin (~8 mM) dissolved in a mixture of Na2HPO4/KH2PO4 (5 mM, pH 7.4):ACN:MeOH:n-octanol (3:4:2.5:0.5, v/v/v/v). C(4)D parameters were set at fixed amplitude of 100 V and frequency of 1000 kHz. The developed method was validated. Calibration curves of the ten FAs were well correlated (r(2)>0.99) within the range of 5-250 μg mL(-1) for lauric acid, and 3-250 μg mL(-1) for the other FAs. The method was simple and sensitive with detection limits (S/N=3) of 0.9-1.9 μg mL(-1) and good relative standard deviations of intra- and inter-day for migration times and peak areas (≤9.7%) were achieved. The method was applied to the determination of FAs in margarine samples. The proposed method offers distinct advantages over the GC and HPLC methods, especially in terms of simplicity (without derivatization) and sensitivity.
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http://dx.doi.org/10.1016/j.chroma.2013.03.014DOI Listing
May 2013

In-vial liquid-liquid microextraction-capillary electrophoresis method for the determination of phenolic acids in vegetable oils.

Anal Chim Acta 2012 Sep 5;742:59-66. Epub 2012 Mar 5.

School of Chemical Sciences, Universiti Sains Malaysia, 11800 Minden, Penang, Malaysia.

An in-vial liquid-liquid microextraction method was developed for the selective extraction of the phenolic acids (caffeic, gallic, cinnamic, ferulic, chlorogenic, syringic, vanillic, benzoic, p-hydroxybenzoic, 2,4-dihydroxybenzoic, o-coumaric, m-coumaric and p-coumaric) in vegetable oil samples. The optimised extraction conditions for 20 g sample were: volume of diluent (n-hexane), 2 mL; extractant, methanol: 5 mM sodium hydroxide (60:40; v/v); volume of extractant, 300 μL (twice); vortex, 1 min; centrifugation, 5 min. Recoveries for the studied phenolic acids were 80.1-119.5%. The simultaneous determination of the phenolic acid extracts was investigated by capillary electrophoresis (CE). Separations were carried out on a bare fused-silica capillary (50 μm i.d.× 40 cm length) involving 25 mM sodium tetraborate (pH 9.15) and 5% methanol as CE background electrolyte in the normal polarity mode, voltage of 30 kV, temperature of 25°C, injection time of 4s (50 mbar) and electropherograms were recorded at 200 nm. The phenolic acids were successfully separated in less than 10 min. The validated in-vial LLME-CE method was applied to the determination of phenolic acids in vegetable oil samples (extra virgin olive oil, virgin olive oil, pure olive oil, walnut oil and grapeseed oil). The developed method shows significant advantages over the current methods as lengthy evaporation step is not required.
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http://dx.doi.org/10.1016/j.aca.2012.02.045DOI Listing
September 2012

Micellar electrokinetic chromatography method for the simultaneous determination of furanic compounds in honey and vegetable oils.

Talanta 2012 Aug 27;97:23-31. Epub 2012 Apr 27.

School of Chemical Sciences, Universiti Sains Malaysia, 11800 Penang, Malaysia.

A simple micellar electrokinetic chromatography (MEKC) method for the simultaneous determination of 2-furfural (2-F), 3-furfural (3-F), 5-methylfurfural (5-MF), 5-hydroxymethylfurfural (5-HMF), 2-furoic acid (2-FA) and 3-furoic acid (3-FA) in honey and vegetable oils is described. Parameters affecting the separation such as pH, buffer and surfactant concentrations, applied voltage, capillary temperature, injection time and capillary length were studied and optimized. The separation was carried out in normal polarity mode at 20 °C, 22 kV and using hydrodynamic injection (17 s). The separation was achieved in a bare fused-silica capillary (46 cm × 50 μm i.d.) with a background electrolyte of 75 mM phosphoric acid (pH 7.3), containing 200 mM of sodium dodecyl sulphate (SDS). The detection wavelengths were at 200 nm (2-FA and 3-FA) and 280 nm (2-F, 3-F, 5-MF, 5-HMF). The furfurals were well separated in less than 20 min. The method was validated in terms of linearity, limit of detection and quantitation, precision and recoveries. Calibration curves of the six furfurals were well correlated (r(2)>0.991) within the range 1-25 μg mL(-1). Relative standard deviations of intra- and inter-day migration times and corrected peak areas ≤9.96% were achieved. The limit of detection (signal:noise, 3) was 0.33-0.70 μg mL(-1) whereas the limit of quantitation (signal:noise, 10) was 1.00-2.12 μg mL(-1). The method was applied to the determination of furanic compounds in honeys and vegetable oils (palm, walnut, grape seed and rapeseed). The effects of thermal treatment and gamma irradiation on the formation of the furanic compounds in honey were also investigated.
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http://dx.doi.org/10.1016/j.talanta.2012.03.056DOI Listing
August 2012