Effect of modifiers for As,Cu and Pb determinations in sugar-cane spirits by GF AAS

Palladium plus magnesium nitrates with and without Ir, Ru and W were evaluated for the simultaneous determination of As, Cu and Pb in cachaça by graphite furnace atomic absorption spectrometry. For 20 μL of sample, 5 μL Pd(NO₃)₂ and 3 μL Mg(NO₃)₂ dispensed together onto the Ir-coated platform of the THGA, analytical curves in the 0–30.0 μg L⁻¹ As, 0–1.50 mg L⁻¹ Cu and 0–60.0 μg L⁻¹ Pb were built up and typical linear correlation coefficients were always better than 0.999. The limit of detection was 1.30 μg L⁻¹ As, 140 μg L⁻¹ Cu and 0.90 μg L⁻¹ Pb. As, Cu and Pb contents in 10 cachaça samples agreed with those obtained by ICP-MS. Recoveries of spiked samples varied from 96% to 106% (As), 97% to 112% (Cu) and 92% to 108% (Pb). The relative standard deviation (n = 12) was typically 2.7%, 3.3% and 1.9%.     

Synthesis and application of a new functionalized resin for use in an on-line,solid phase extraction system for the determination of trace elements in waters and reference cereal materials by flame atomic absorption spectrometry

The synthesis and characterization of the resin Amberlite XAD-4 functionalized with 2,6-pyridinedicarboxaldehyde and its application in an on-line system for the preconcentration of cadmium, cobalt, copper, lead and manganese prior to determination using flame atomic absorption spectrometry (FAAS) is proposed. Metal ions retained on the modified resin were eluted using 1.0 mol L⁻¹ HNO₃ solution and aspirated directly to the nebulizer–burner system of a FAAS instrument using a flow injection system. Detection limits (3σ) were determined to be 0.13 μg L⁻¹ for Cd, 0.29 μg L⁻¹ for Cu, 0.23 μg L⁻¹ for Mn, 0.58 μg L⁻¹ for Co and 2.19 μg L⁻¹ for Pb using a 10 mL of water sample loading volume. The limits of detection would be 100 times higher with units of μg kg⁻¹ for the solid samples in which their dilution ratios as (volume/weight) were 100. Enrichment factors ranged from 23.6 to 28.9 (for Co and Mn, respectively). The proposed method was successfully applied to determination of the analytes in natural water samples and certified reference materials.     

Determination of Ge(IV) in rice in a mercury-coated glassy carbon electrode in the presence of catechol

Electrochemical adsorptive cathodic stripping voltammetry determination of Ge(IV) using the catechol complex on a mercury-coated (MC) electrode was prepared using a glassy carbon electrode (GCE), the peak potential of which was −0.5 V vs. Ag/AgCl on MCGCE. The various parameters of the catechol concentration, its pH, and others were optimized. The linear working ranges were obtained in the concentration of 2–700 μg L⁻¹ Ge(IV). The relative standard deviation at the Ge(IV) concentration of 50 μg L⁻¹ was 1.37% (n = 15) using the optimum condition, and the detection limit was found to be 0.6 μg L⁻¹ (8.26 × 10⁻⁹ M) (S/N = 3), with an adsorption time of 180 s. The Ge(IV) response was highly linear. This developed method was applied to Ge(IV) to determine the presence of rice grains.     

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.     

Determination of aflatoxins in eggs,milk, meat and meat products using HPLC fluorescent and UV detectors

Raw and pasteurised sheep’s, cow’s and goat’s milk, eggs, and beef samples from different local markets in Jordan were collected during a period of 5 months (January through May 2007) and examined for aflatoxins B1(AFB1), B2(AFB2), G1(AFG1), G2(AFG2), M1(AFM1) and M2(AFM2). The samples were analysed with high performance liquid chromatography (HPLC) using UV and Fluorescent detectors. The analysed samples of milk collected in January were found to contain 0.56 μg L⁻¹ AFM1 and 0.1 μg L⁻¹ AFM2 whilst, the concentration of AFM1 and AFM2 was < 0.05 μg L⁻¹ for milk samples collected between March and May. The AFB1, AFB2, AFG1 and AFG2 contents in the analysed food products ranged from 1.10 to 8.32 μg L⁻¹ and 0.15 to 6.36 μg L⁻¹ in imported and fresh meat samples collected during March, respectively. The mean recovery for the HPLC method was 92% to 109% and the quantification levels were 50 ng L⁻¹ for AFM1 and AFM2. The AFM1 was found in 10% of the tested samples with concentrations between 0.08 and 1.1 μg kg⁻¹ and AFM2 was only found in 1.82% of the tested samples with a level of 0.1 μg kg⁻¹. The AFM1 levels in the examined foods were higher than the maximum level of AFM1 in liquid milk set by the European Community and Codex Alimentarius of 50 ng L⁻¹.     

Response surface modelling of lead pre-concentration from food samples by miniaturised homogenous liquid–liquid solvent extraction: Box–Behnken design

In this study, a new method called miniaturised homogenous liquid–liquid extraction, followed by graphite furnace atomic absorption spectrometry, was developed for the extraction and determination of lead from food samples. The procedure was based on the fast extraction of lead from an acetic acid sample solution into 0.5 mL chloroform, as an extraction solvent. After adding water into the mixture, the extracting solvent phase immediately formed a distinct water-immiscible phase below the vial, which could easily be separated, evaporated and re-dissolved in 1.0 mL nitric acid 0.1 mol L⁻¹ for further analysis. The effects of various experimental parameters in extraction step were studied using two optimisation methods, one variable at a time and Box–Behnken design. The results showed that the amount of salt and extraction time did not have effect on the extraction efficiency. Therefore, a three-level Box–Behnken experimental design with three factors, which combined the response surface modelling, was used to optimise lead extraction. Three independent variables, including pH of solution (ranging from 6.5 to 10.5), concentration of dithizone as chelating agent (ranging from 0.05 to 0.5 μg L⁻¹) and extracting solvent volume (ranging from 300 to 900 μL) were respectively coded as pH, D and V at three different levels (−1, 0 and 1). In this study, the optimum condition was determined at pH 8.4, a volume of chloroform at 0.45 mL, and concentration of dithizone at 0.5 μg L⁻¹. Under the optimum condition, the limit of detection (LOD) was 0.05 μg L⁻¹. Furthermore, the relative standard deviation of the ten replicate was <5.0%. The developed procedure was applied to the extraction and determination of lead in the food samples.     

A novel quantum dot-based fluoroimmunoassay method for detection of Enrofloxacin residue in chicken muscle tissue

A rapid indirect competitive fluorescence-linked immunosorbent assay (cFLISA) based on quantum dots (QDs) as the fluorescent marker has been developed for the detection of Enrofloxacin (ENR) in chicken muscle tissue. The end-point fluorescent detection system was carried out using QDs conjugated with goat anti-mouse secondary antibody. The cFLISA method allowed for ENR determination in a liner working range of 1–100 ng mL⁻¹ with the 50% inhibition value (IC₅₀) of 8.3 ng mL⁻¹ and the limit of detection (LOD) of 2.5 ng mL⁻¹. The recoveries for chicken muscle samples spiked with ENR at levels of 50–200 μg kg⁻¹ ranged from 81% to 94% with coefficients of variation (CV) of 10–13%. In real chicken tissue sample analysis, the results of cFLISA were similar to those obtained from an indirect competitive enzyme-linked immunosorbent assay (cELISA) to a high performance liquid chromatography method (HPLC), which indicated that cFLISA is suitable as screening method for the monitoring of veterinary drug residues.     

Immobilization of pepsin on chitosan beads

In this study, chitosan beads were prepared by using a cross-linking agent and the resulting beads were employed in immobilization process. Studies on free and immobilized pepsin systems for determination of optimum temperature, optimum pH, thermal stability, pH stability, operational stability, storage stability and kinetic parameters were carried out. The optimum temperature interval for free pepsin and immobilized pepsin were 30–40 and 40–50 °C, respectively. Free and immobilized pepsin showed higher activity at pH 2.0–4.0. Apparent K_m = 12.0 g L⁻¹ haemoglobin (1.56 mM tyrosine) and V_max = 5220 μmol (mg protein min)⁻¹ values were obtained for free pepsin, while apparent K_m = 20.0 g L⁻¹ haemoglobin (2.16 mM tyrosine) and V_max = 2780 μmol (mg protein min)⁻¹ values were obtained for immobilized pepsin. Thermal stability and storage stability of immobilized pepsin were higher than that of free pepsin. Milk clotting activity was used for evaluation of the applicability of pepsin immobilization to industrial process. Optimum milk clotting temperature was found as 40 °C for free pepsin and 50 °C for immobilized pepsin.     

Determination of melamine by flow injection analysis based on chemiluminescence system

In this paper, based upon the phenomenon that melamine can obviously enhance the CL signal of the luminol–H₂O₂ system in basic medium, a simple, rapid and sensitive flow injection chemiluminescence (FI-CL) method for the determination of melamine has been developed. Under the optimum conditions, the linear range for the determination of melamine was 0.2–80 μg mL⁻¹ with a detection limit of 0.12 μg mL⁻¹ calculated as proposed by IUPAC and a relative standard deviation of 3.26% for 11 solutions of 10 μg mL⁻¹ melamine on the same day. The proposed method was satisfactorily applied to determine melamine in milk-based products and satisfactory results were obtained without interferences from the sample matrix. Moreover, one assay produce takes only 25 s and the minimum sampling rate is about 120 samples h⁻¹, which indicated that the FI-CL method was suitable for high throughput and real-time melamine analysis.     

Spectrofluorimetric determination of buparvaquone in biological fluids,food samples and a pharmaceutical formulation by using terbium–deferasirox probe

A simple spectrofluorimetric method is described for the determination of buparvaquone (BPQ), based on its quenching effect on the fluorescence intensity of Tb³⁺–deferasirox (DFX) complex as a fluorescent probe. The excitation and emission wavelengths were 328 and 545 nm, respectively. The optimum conditions for determination of BPQ were investigated considering the effects of various affecting parameters. The variations in fluorescence intensity of the system showed a good linear relationship with the concentration of BPQ in the range of 10–1500 μg L⁻¹, its correlation coefficient was 0.999 with the detection and quantification limits of 1.1 and 3.4 μg L⁻¹, respectively. Linearity, reproducibility, recovery, limits of detection and quantification made the method suitable for BPQ assay in biological fluids, meat, dairy products and BPQ parenteral solutions (vials). The method was applied to real samples of serum and milk of three cows receiving BPQ.     

Determination of lead and cadmium in food samples by the coprecipitation method

In this study, the coprecipitation method developed using a combination of 2-mercaptobenzothiazole (MBT) as a chelating reagent and copper as coprecipitate carrier was used for the determination of trace lead and cadmium in various food samples by graphite furnace atomic absorption spectrometry (GFAAS). The method was applied for the determination of Pb(II) and Cd(II) in salami, sausage, chicken, anchovy, spinach, cabbage, onion, dill, parsley, lettuce, tea and rice samples. The matrix modifiers were added as 50 μg NH₄H₂PO₄ + 3 μg Mg(NO₃)₂ for both Pb(II) and Cd(II). The signals were measured as peak area. The concentrations of Pb(II) and Cd(II) in the food samples were found to be in the range of 6.63 ng g⁻¹ (anchovy) −3.30 μg g⁻¹ (spinach) and 2.67 ng g⁻¹ (salami) −0.51 μg g⁻¹ (lettuce), respectively.     

Rapid determination of three alkaloids from Lotus Plumule in human serum using an HPLC-DAD method with a short monolithic column

An HPLC-DAD with a short monolithic column method was used for rapid, sensitive and simultaneous determination of liensinine, isoliensinine and neferine in human serum. Chromatographic separation was achieved on an RP-HPLC chromolithic column (50 mm × 4.6 mm i.d.), with a mobile phase of methanol–water–triethylamine–acetic acid (70:30:0.2:0.05), at a flow rate of 1 ml min⁻¹. The calibration curves of three alkaloids exhibit good linear relationship in the concentration range of 0.5–80 μg ml⁻¹. The limits of detection (LODs) of three alkaloids were 20, 20 and 25 ng ml⁻¹, respectively, and the separation time was 4 min. A comparative study has been performed with a normal C₁₈ packed column (150 mm × 4.6 mm i.d., 5 μm). The separation time was 16 min and the LODs of three alkaloids were 56, 56 and 65 ng ml⁻¹, respectively.     

Chemiluminescence microflow injection analysis system on a chip for the determination of nitrite in food

A new microflow injection analysis (μFIA) system on a chip for the determination of nitrite is described. The chip is produced by using two transparent poly(methylmethacrylate) (PMMA) slices measured 50 × 40 × 5 mm, and the microchannels etched by CO₂ laser are 200 μm wide and 100 μm deep with the volume of reaction area about 1.8 μL. Nitrite is sensed by the chemiluminescence (CL) reaction of luminol with ferricyanide that is the product of the reaction of ferrocyanide with nitrite in acidic medium. The syringe pump with an accurate timer controls all reagents, including the sample. The linear range of the nitrite concentration is 8–100 μg L⁻¹ and the detection limit is 4 μg L⁻¹ (S/N = 3). The proposed method has good reproducibility with the relative standard deviation 4.1% for 50 μg L⁻¹ of nitrite (n = 9) and is very sensitive and simple. It has been successfully applied to the determination of nitrite in food.     

Comparison of positive and negative ion detection of tea catechins using tandem mass spectrometry and ultra high performance liquid chromatography

Tea catechins are an important group of natural compounds associated with health promoting effects and desired commodities for the growing market of dietary supplements and functional foods. Consequently these compounds attract more interest of research groups worldwide. A reliable quantitative analysis of tea catechins is essential for human intervention studies, manufacturers of dietary supplements and quality control by authorities. UHPLC–ESI-MS/MS analytical method was chosen due to rapid runtime, high sensitivity and selectivity. The chromatographic separation of eight tea catechins was achieved within 2.5 min on C₁₈ BEH analytical column (100 mm × 2.1 mm i.d.; 1.7 μm), whilst the gradient elution mode was employed using water:methanol mobile phase with addition of volatile organic acid. The concentration of organic acids in the mobile phase was optimised within the range of 0.01–0.1% (v/v). High sensitivities were achieved in positive (10.2-16.8 fmol/inj.) and negative ion detection mode (102.1-168.1 fmol/inj.), through accurate and complex tuning of MS parameters. The UHPLC-ESI-MS/MS method was validated in terms of linearity (>0.9997; >0.9990), range (0.02–2.40 mg L⁻¹; 0.15-24.00 mg L⁻¹), LOD (3.0–4.8 μg L⁻¹; 30.1–48.0 μg L⁻¹), LOQ (9.9–15.8 μg L⁻¹; 150.5-240.0 μg L⁻¹), intra-day precision (4.4-7.1% RSD; 3.3-5.1% RSD), accuracy (94.06-113.7%; 89.5-108.4%), retention time repeatability (0.0-0.5% RSD; 0.0-0.6% RSD), and peak area repeatability (1.2-4.0% RSD; 2.4-3.5% RSD) for positive and negative ion detection modes, respectively. The statistical comparison of the quantitative results obtained in positive and negative ion detection mode was performed.     

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.     

Occurrence of patulin and its dietary intake through apple juice consumption by the Spanish population

A survey was conducted to determine levels and dietary intake of Patulin (PAT) from apple juices consumed in Spain. One hundred samples of apple juice were bought from distinct supermarkets. PAT was extracted by a liquid–liquid extraction technique and analysed with a micellar electrokinetic chromatography (MEKC) method. 66% of the samples contained PAT over the limit of detection of the method (0.7 μg L⁻¹). The PAT apple juice mean and median levels obtained were 19.4 and 4.8 μg L⁻¹, respectively, in a range between 0.7 and 118.7 μg L⁻¹. In 11% of the samples, PAT contamination exceeded the maximum permitted level of 50 μg L⁻¹ established by the EU regulation. In Spain, no significant variations were observed with respect to data published 15 years ago.     

Effect of foliar application of selenium on its uptake and speciation in carrot

Carrot (Daucus carota) shoots were enriched by selenium using foliar application. Solutions of sodium selenite or sodium selenate at 10 and 100 μg Se ml⁻¹, were sprayed on the carrot leaves and the selenium content and uptake rate of selenium were estimated by ICP–MS analysis. Anion and cation exchange HPLC were tailored to and applied for the separation of selenium species in proteolytic extracts of the biological tissues using detection by ICP–MS or ESI–MS/MS. Foliar application of solutions of selenite or selenate at 100 μg Se ml⁻¹ resulted in a selenium concentration of up to 2 μg Se g⁻¹ (dry mass) in the carrot root whereas the selenium concentration in the controls was below the limit of detection at 0.045 μg Se g⁻¹ (dry mass). Selenate-enriched carrot leaves accumulated as much as 80 μg Se g⁻¹ (dry mass), while the selenite-enriched leaves contained approximately 50 μg Se g⁻¹ (dry mass). The speciation analyses showed that inorganic selenium was present in both roots and leaves. The predominant metabolised organic forms of selenium in the roots were selenomethionine and γ-glutamyl-selenomethyl-selenocysteine, regardless of which of the inorganic species were used for foliar application. Only selenomethionine was detected in the carrot leaves. The identity of selenomethionine contained in carrot roots and leaves was successfully confirmed by HPLC–ESI–MS/MS.     

Spectrophotometric determination of melamine in milk by rank annihilation factor analysis based on pH gradual change-UV spectral data

A new spectrophotometric method has been developed in this paper to determine melamine in milk by applying rank annihilation factor analysis (RAFA) based on pH gradual change-UV spectral data (pH-spectra). In the proposed method, the spectra of the sample solutions at different pH data points were recorded and the pH-spectra bilinear data matrix was generated. Based on these data, the RAFA was then applied to calculate the concentration of melamine in milk. The experiments have been conducted and the results were satisfactory. Under the optimised conditions, linearity of the proposed method was in the range of 0.04–4.0 μg mL⁻¹ for calibration samples, and 0.04–3.5 μg mL⁻¹ for the mixed solutions of melamine with the background milk components. The detection limit (DL) was 12 ng mL⁻¹. The relative predictive error (RPEs) and root mean square error of prediction (RMSEP) of applying RAFA were 0.91% and 0.0151, respectively.     

Residue levels of food-grade antioxidants in postharvest treated in-pod peanuts during five months of storage

In order to investigate residue levels of butylated hydroxyanisole (BHA), propyl paraben (PP) and butylated hydroxytoluene (BHT) during storage, eight-hundred kilograms of bulk peanuts were treated with the following antioxidant emulsions: BHA (1802 μg g⁻¹), BHA–PP (1802 μg g⁻¹ + 1802 μg g⁻¹) M1 and BHA–PP–BHT mixtures (1802 μg g⁻¹ + 901 μg g⁻¹ + 2204 μg g⁻¹) M2 and (1802 μg g⁻¹ + 1802 μg g⁻¹ + 2204 μg g⁻¹) M3. Residues were determined in peanut pod and seed tissues at 1-month intervals during the storage. While the reduction levels of BHA and PP in pods at the end of the storage period ranged from 66% to 76%, BHT levels were decreased extensively (86%). Twenty-four hours after peanuts were treated, antioxidant emulsions effectively seeped into the seeds and low levels of these chemicals were detected during the assay. Residues of PP in seeds were lower (62%) than the other antioxidants. Although the doses used were higher than those approved for food-grade antioxidants in stored peanuts, the residue levels in seeds (32.8–0.02 μg g⁻¹) did not exceed the maximum residue limits during the storage period.     

Development of polyclonal antibody-based indirect competitive enzyme-linked immunosorbent assay for sodium saccharin residue in food samples

A sensitive and specific polyclonal antibody (PcAb)-based indirect competitive enzyme-linked immunosorbent assay (icELISA) for sodium saccharin is described. 6-Amino saccharin was coupled to carrier protein for artificial antigen by diazotisation. New Zealand white rabbits were immunised to obtain anti-sodium saccharin PcAb and then icELISA was developed. The assay showed high sensitivity and specificity to sodium saccharin, with the 50% inhibition value (IC₅₀) of 0.243 μg mL⁻¹, workable range (IC₃₀–IC₇₀) of 0.050–12.8 μg mL⁻¹ and limit of detection (LOD, IC₂₀) of 0.021 μg mL⁻¹. The average recoveries of sodium saccharin in spiked food samples were estimated ranging from 70.7% to 98.8%. A statistically significant correlation of results was obtained between this new ELISA and previously established HPLC approaches with the food-relevant sodium saccharin concentration range 0–320 μg mL⁻¹ (R² = 0.9887–0.9975). These results indicated that the established ELISA was a potential and useful analytical tool for rapid determination of sodium saccharin residue in food samples.