Benzoic and sorbic acid in soft drink,milk, ketchup sauce and bread by dispersive liquid–liquid microextraction coupled with HPLC

Benzoic acid and sorbic acid are widely used for food preservation. These preservatives are generally recognised as safe. The aim of this study was to determine the level of benzoic and sorbic acid in food samples that are usually consumed in Iran. Therefore, 54 samples, including 15 soft drinks, 15 ultra-high-temperature milk, 15 ketchup sauces and 9 bread samples, were analysed by high-performance liquid chromatography with UV detection. Benzoic acid was detected in 50 (92.5%) of the samples ranging from 3.5 to 1520 µg mL^?1, while sorbic acid was detected in 29 (50.3%) samples in a range of 0.8 and 2305 µg mL^?1. Limits of detection and limits of quantification for benzoate were found to be 0.1 and 0.5 µg mL^?1, respectively, and for sorbate 0.08 and 0.3 µg mL^?1, respectively. The results showed that benzoic acid and sorbic acid widely occur in food products in Iran.     

Aflatoxin B1 in eggs and chicken livers by dispersive liquid–liquid microextraction and HPLC

A rapid, low-cost and simple technique has been developed for the determination of aflatoxin B₁ (AFB₁) in eggs and livers using high-performance liquid chromatography (HPLC) with UV detection. In this study, the presence of AFB₁ was investigated in 150 eggs and 50 chicken livers from the local market of Tabriz, Iran. AFB₁ was extracted with a mixture of acetonitrile:water (80:20) and cleaned up by dispersive liquid–liquid microextraction which is a very economical, fast and sensitive method. AFB₁ was quantified by HPLC-UV without need for any complex derivatisation in samples to enhance the detection. The results showed that 72% of the liver and 58% of the egg samples were contaminated with AFB₁ ranging from 0.30 to 16.36 µg kg ^?1. limit of detection and limit of quantification for AFB₁ were 0.08 and 0.28 µg kg ^{? 1}, respectively. The proposed method is suitable for fast analysing of AFB₁ in egg and liver samples.     

Magnetic effervescent tablet-assisted ionic liquid dispersive liquid–liquid microextraction of selenium for speciation in foods and beverages

A novel, simple and rapid method based on magnetic effervescent tablet-assisted ionic liquid dispersive liquid–liquid microextraction (MEA-IL-DLLME) followed by graphite furnace atomic absorption spectrometry (GFAAS) determination was established for the speciation of selenium in various food and beverage samples. In the procedure, a special magnetic effervescent tablet containing CO₂ sources (sodium carbonate and sodium dihydrogenphosphate), ionic liquids and Fe₃O₄ magnetic nanoparticles (MNPs) was used to combine extractant dispersion and magnetic recovery procedures into a single step. The parameters influencing the microextraction efficiency, such as pH of the sample solution, volume of ionic liquid, amount of MNPs, concentration of the chelating agent, salt effect and matrix effect were investigated and optimised. Under the optimised conditions, the limits of detection (LODs) for Se(IV) were 0.021 μg l^–1 and the linear dynamic range was 0.05–5.0 μg l^–1. The relative standard deviation for seven replicate measurements of 1.0 μg l^–1 of Se(IV) was 2.9%. The accuracy of the developed method was evaluated by analysis of the standard reference materials (GBW10016 tea, GBW10017 milk powder, GBW10043 Liaoning rice, GBW10046 Henan wheat, GBW10048 celery). The proposed method was successfully applied to food and beverage samples including black tea, milk powder, mushroom, soybean, bamboo shoots, energy drink, bottled water, carbonated drink and mineral water for the speciation of Se(IV) and Se(VI) with satisfactory relative recoveries (92.0–108.1%).     

Use of hollow fibre-based liquid–liquid–liquid microextraction and high-performance liquid chromatography–diode array detection for the determination of phenolic acids in fruit juices

This paper describes a simple method based on three-phase hollow-fibre liquid-phase microextraction (HF-LPME) for the determination of phenolic acids in fruit juices. Analytes including gallic acid, p-hydroxy benzoic acid, caffeic acid, syringic acid, p-coumaric acid, ferulic acid, and cinnamic acid were separated and determined using high-performance liquid chromatography–photodiode array detection (HPLC–DAD). Parameters affecting the enrichment factors (EFs) were investigated. These compounds were extracted from 5 mL aqueous samples (pH 2) to a thin layer of organic solvent (hexyl acetate) phase impregnated into the pores of the polypropylene hollow fibre wall, and then back extracted to a basic acceptor solution (0.02 M NaOH). EFs ranged from 15 (gallic acid) to 408 (cinnamic acid). The RSD of the method for the analysis of spiked water and fruit juice samples varied from 3.1% to 11.3%. The LODs ranged from 0.01 (cinnamic acid) to 2.0 (caffeic acid) μg/L.     

Analysis of patulin in apple products by liquid–liquid extraction,solid phase extraction and matrix solid-phase dispersion methods: a comparative study

Patulin is a marker of quality in the apple and apple juice industry and due to the potential risk for human health, reliable and potential methods for extracting patulin from a sample are therefore needed. In this study, the three methods with liquid–liquid extraction, matrix solid-phase dispersion (MSPD) and with solid-phase extraction (SPE) were studied for extracting patulin from different apple products. Result showed that for AJC and apple sample, MSPD method is most suitable for extracting patulin among the three methods. The recovery rates of AJC and apple sample were 80.35–114.46 and 79.68–94.32%, respectively, the coefficient variations were 3.18–4.90%; For dilute juice, SPE procedure is suitable for analysis of patulin and the recovery rates were and 85.35–90.14%.     

Simultaneous derivatisation and preconcentration of parabens in food and other matrices by isobutyl chloroformate and dispersive liquid–liquid microextraction followed by gas chromatographic analysis

A simple, rapid and economical method has been proposed for the quantitative determination of parabens (methyl, ethyl, propyl and butyl paraben) in different samples (food, cosmetics and water) based on isobutyl chloroformate (IBCF) derivatisation and preconcentration using dispersive liquid–liquid microextraction in single step. Under optimum conditions, solid samples were extracted with ethanol (disperser solvent) and 200 μL of this extract along with 50 μL of chloroform (extraction solvent) and 10 μL of IBCF was rapidly injected into 2 mL of ultra-pure water containing 150 μL of pyridine to induce formation of a cloudy state. After centrifugation, 1 μL of the sedimented phase was analysed using gas chromatograph-flame ionisation detector (GC–FID) and the peaks were confirmed using gas chromatograph-positive chemical ionisation-mass spectrometer (GC–PCI–MS). Method was found to be linear over the range of 0.1–10 μg mL⁻¹ with square of correlation coefficient (R²) in the range of 0.9913–0.9992. Limit of detection (LOD) and limit of quantification (LOQ) were found to be 0.029–0.102 μg mL⁻¹ and 0.095–0.336 μg mL⁻¹ with a signal to noise ratio of 3:1 and 10:1, respectively.     

A simple,rapid and novel method based on salting-out assisted liquid–liquid extraction for ochratoxin A determination in beer samples prior to ultra-high-performance liquid chromatography coupled to tandem mass spectrometry

A novel, simple, easy and cheap sample treatment strategy based on salting-out assisted liquid-liquid extraction for ochratoxin A (OTA) ultra-trace analysis in beer samples using ultra-high-performance liquid chromatography-tandem mass spectrometry determination was developed. The factors involved in the efficiency of pre-treatment were studied employing factorial design in the screening phase and the optimal conditions of the significant variables on the analytical response were evaluated using a central composite face-centred design. Consequently, the amount of salt ((NH₄)₂SO₄), together with the volumes of sample, hydrophilic (acetone) and nonpolar (toluene) solvents, and times of vortexing and centrifugation were optimised. Under optimised conditions, the limits of detection and quantification were 0.02 µg l^?1 and 0.08 µg l^?1 respectively. OTA extraction recovery by SALLE was approximately 90% (0.2 µg l^?1). Furthermore, the methodology was in agreement with EU Directive requirements and was successfully applied for analysis of beer samples.     

Speciation of inorganic arsenic species and total inorganic arsenic in rice using microwave-assisted dispersive liquid–liquid micro-extraction and electrothermal atomic absorption spectrometry

Human exposure to inorganic arsenic (iAs) via rice consumption is of increasing concern. In the present study, microwave-assisted dispersive liquid–liquid micro-extraction (MADLLME) and electrothermal atomic absorption spectrometry (ETAAS) were developed for the speciation of iAs in rice samples. After microwave-assisted digestion, the As(III) ion reacted with diethyldithiophosphoric acid (DDTP) to form an As–DDTP complex and was extracted at the same time. Some parameters affecting digestion, complex formation, and extraction were studied and optimised. Under the optimised conditions, a detection limit of 0.2 µg kg^?1 with a correlation coefficient of 0.9901 were obtained with a calibration curve in the range of 0.5–200 µg kg^?1. Total iAs was determined after reduction of As(V) to As(III) with sodium thiosulfate and potassium iodide, and As(V) was calculated by difference. The proposed extraction procedure was successfully applied for the determination of iAs ions in certified reference materials (NIST CRM 1568a and NMIJ CRM 7503a) and 10 rice samples produced in Iran and other Asian countries.     

Multi-residue method for determination of seven neonicotinoid insecticides in grains using dispersive solid-phase extraction and dispersive liquid–liquid micro-extraction by high performance liquid chromatography

A method using dispersive solid-phase extraction and dispersive liquid–liquid micro-extraction cleanup followed by high performance liquid chromatography (HPLC) has been established for determination of seven neonicotinoid insecticides residues in grains including brown rice, maize, millet and oat. Based on an appraisal of the characteristics of HPLC, validation experiments were conducted for seven neonicotinoid insecticides. In the method, dispersive solid-phase extraction was carried out using PSA and bonded C₁₈ coupled with graphitised carbon black with acetonitrile as the eluted solvent. In the linear range of each pesticide, the correlation coefficient was R² ? 0.99. At the low, medium and high three fortification levels of 0.05–0.8 mg kg⁻¹, recoveries fell within 76–123%. The relative standard deviation was between 0.9% and 12.6% for seven neonicotinoid pesticides. Low limits of detection (0.002–0.005 mg kg⁻¹) and quantification (0.007–0.018 mg kg⁻¹) were readily achieved with this method for all tested pesticides.     

Assessment of strobilurin fungicides’ content in soya-based drinks by liquid micro-extraction and liquid chromatography with tandem mass spectrometry

Seven strobilurin fungicides were pre-concentrated from soya-based drinks using dispersive liquid–liquid micro-extraction (DLLME) with a prior protein precipitation step in acid medium. The enriched phase was analysed by liquid chromatography (LC) with dual detection, using diode array detection (DAD) and electrospray-ion trap tandem mass spectrometry (ESI-IT-MS/MS). After selecting 1-undecanol and methanol as the extractant and disperser solvents, respectively, for DLLME, the Taguchi experimental method, an orthogonal array design, was applied to select the optimal solvent volumes and salt concentration in the aqueous phase. The matrix effect was evaluated and quantification was carried out using external aqueous calibration for DAD and matrix-matched calibration method for MS/MS. Detection limits in the 4–130 and 0.8–4.5 ng g^?1 ranges were obtained for DAD and MS/MS, respectively. The DLLME-LC-DAD-MS method was applied to the analysis of 10 different samples, none of which was found to contain residues of the studied fungicides.     

Determination of phenolic compounds in olive oil: New method based on liquid–liquid micro extraction and ultra high performance liquid chromatography-triple–quadrupole mass spectrometry

A novel analytical approach has been performed and evaluated for the identification and quantification of phenolic compounds (phenolic alcohols, secoiridoid derivates, lignans, flavonoids, phenolic acids and aldehydes) which can be found in both virgin olive oil (VOO) and extra virgin olive oil (EVOO). An improved liquid–liquid micro extraction (LLME) method combining with ultra high performance liquid chromatography (UHPLC) coupled to electrospray ionization source (ESI) and tandem mass spectrometry (MS/MS) in Dynamic Multiple Reaction Monitoring (DMRM) mode has been developed, reducing the amount of sample, reagents and time consumed. The proposed methodology was applied to standard solutions, and the quality control parameters obtained were compared with those achieved in spiked refined olive oil (SROO). Generally, these parameters showed lower values in SROO than in standard solutions. Matrix effect, recovery and process efficiency have been studied using SROO. The recoveries were around 90% and the process efficiency of the whole method was higher than 80% for most of the phenolic compounds studied. Examination of these parameters revealed that work straight in the olive oil matrix, which is closer to behave as a real sample, provides better results. The applicability and reliability of this methodology have been confirmed using real samples.     

Determination of β-carotene content and vitamin A activity of vegetables by high-performance liquid chromatography and spectrophotometry

A fast and sensitive high-performance liquid chromatographic (HPLC) method for the determination of the provitamin A, β-carotene, in vegetables is described. After alkaline saponification and organic extraction β-carotene is separated from other carotenoids on a reversed-phase HPLC column and determined by measurement of its absorbance at 445 nm. The total amount of carotenoids is determined by measurement of the absorbance at 445 nm of the extract prior to HPLC.Results are presented of the analysis of β-carotene and total carotenoids in some vegetables bought at a local market in Dar es Salaam. The percentage β-carotene, of the total carotenoid content, showed a great variation. The vitamin A activity of the vegetables was calculated from the analytical results.     

Multi-residual analysis of 16 β-agonists in pig liver,kidney and muscle by ultra performance liquid chromatography tandem mass spectrometry

A delicate method was developed for simultaneous analysis of 16 illegal residual β-agonists in pork tissues including liver, kidney and meat. The samples were subjected to enzymatic hydrolysis, extracted with perchloric acid, and then dual Oasis HLB and MCX solid phase extraction (SPE) cartridges were used for cleanup. The analytes were quantified by ultra performance liquid chromatography coupled with electrospray ionisation tandem mass spectrometry (UPLC–ESI–MS/MS) operating in positive multiple-reaction mode (MRM). Matrix-fortified calibration curves were performed to compensate for the matrix effect and loss in sample preparation. CCα and CCβ of the analytes upon the method ranged from 0.02 to 0.79 μg/kg and from 0.04 to 1.62 μg/kg, respectively.     

Effervescent-assisted dispersive liquid–liquid microextraction based on the solidification of floating organic droplets for the determination of fungicides in vinegar and juice

ABSTRACT

A method of effervescent-assisted dispersive liquid–liquid microextraction based on the solidification of a floating organic droplet is reported. This approach was used to measure the fungicides myclobutanil, tebuconazole and epoxiconazole in vinegar and juice. Acidic vinegar and juice reacted with the carbonate to produce effervescence in situ, which then promoted contact of the sample with the extraction solvent. The 1-dodecanol extraction solvent helped solidify the floating organic droplets and could be fully dispersed by effervescence. The extraction solvent, salt, carbonate, and extraction time were optimised. The optimal conditions were 200 μL of 1-dodecanol, 100 mg of sodium chloride, 50 mg of sodium bicarbonate, and 30 s of extraction time. The proposed method has good linearity between 10 and 1000 ng mL^?1. Recoveries were between 70.4% and 103.1% in different vinegar and juice samples. This method was successfully used to measure fungicides in vinegar and juice. This system is simple, fast and environmentally friendly.     

Modified dispersive liquid–liquid microextraction followed by high-performance liquid chromatography for the determination of clenbuterol in swine urine

A modified dispersive liquid–liquid microextraction (DLLME) technique combined with an HPLC-UV procedure was developed for the extraction and determination of clenbuterol in swine urine. The modification involved the selection of methyl tert-butyl ether (MTBE) as the dispersive solvent, which had a low solubility in aqueous samples, playing the part of dispersion with the help of violent shaking. MTBE improved the partition of clenbuterol into the extractant, and helped the formation of phase separation. Various factors affecting the extraction efficiency including selection of the organic extractant and the dispersive solvent, the volume of extractant and dispersive solvent, salt concentration, NaOH concentration and centrifugation time were evaluated and optimised. Under the optimal conditions, precision, linearity (correlation coefficient, r ^2?=?0.996 over the concentration range of 10–1000?ng?ml^?1), detection limit (2.4?ng?ml^?1) and enrichment factor of 55 were obtained. The modification to the DLLME made it suitable for analytes with pronounced solubility, especially when the compounds are highly polar and thus more difficult to extract effectively by DLLME. The procedure was suitable for the fast screening of clenbuterol residue in swine urine.     

Salt-assisted liquid–liquid microextraction for the determination of iodine in table salt by high-performance liquid chromatography-diode array detection

2-Iodosobenzoate and N,N-dimethylaniline have been used at pH 6.4 for selective conversion of iodide to 4-iodo-N,N-dimethylaniline which was extracted with ethanol, when the phase separation occurred by addition of ammonium sulphate, a process called salt-assisted liquid–liquid microextraction (SALLME), and analysed by high-performance liquid chromatography-diode array detection. Iodate was reduced to iodide before derivatisation. The method has been optimised for extracting solvent, salt for phase separation, and reaction time. A linear calibration was obtained for 10 μg-10 mg L⁻¹ of iodide with correlation coefficient of 0.9989 and limit of detection of 3.7 μg L⁻¹. The SALLME produced 280-fold enrichment of the derivative. The commercial iodised table salt samples have been found highly inhomogeneous; the RSD in analysis of different aliquots of the same sample ranged 18.0-78.1%. The average recovery of spiked iodide to real samples was 98.4% with an average RSD of 7.9% (range 5.2-12.4%).     

Dispersive liquid–liquid microextraction for the determination of organochlorine pesticides residues in honey by gas chromatography-electron capture and ion trap mass spectrometric detection

A simple dispersive liquid–liquid microextraction (DLLME) protocol for the determination of 15 organochlorine pesticides residues in honey is proposed. The selected pesticides were separated using gas chromatography and detected by electron capture (ECD) or ion trap mass spectrometry (GC-IT/MS). Several parameters affecting the extraction efficiency namely type and volume of organic extraction solvent, type and volume of disperser solvent, sample pH, ionic strength, extraction time and centrifugation speed were systematically investigated. The final DLLME protocol involved the addition of 750 μL acetonitrile (disperser) and 50 μL chloroform (extraction solvent) into a 5 mL aqueous honey solution followed by centrifugation. The sedimented organic phase (chloroform) were analysed directly by GC-IT/MS or evaporated and reconstituted in acetonitrile prior to the GC-ECD analysis. The analytical performance of the GC-ECD and GC-IT/MS methods was compared and discussed. Under the selected experimental conditions, the enrichment factors varied between of 36 and 114. The limits of detection (LOD) were in the range of 0.02–0.15 μg L⁻¹ (0.4–3 ng g⁻¹) for GC-ECD and 0.01–0.2 μg L⁻¹ (0.2–4 ng g⁻¹) for GC-IT/MS which is adequate to verify compliance of products to legal tolerances. The proposed method was applied to the analysis of the selected organochlorine pesticides residues in various honey samples obtained from Greek region. Mean recoveries were ranged from 75% to 119% while the precision was better than 20% in both methodologies.