Simultaneous analysis of 21 elements in foodstuffs by ICP-MS after closed-vessel microwave digestion: Method validation

This paper describes a validation process for the simultaneous analysis of 21 elements: lithium (Li), aluminium (Al), vanadium (V), manganese (Mn), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), gallium (Ga), germanium (Ge), arsenic (As), strontium (Sr), molybdenum (Mo), silver (Ag), cadmium (Cd), tin (Sn), antimony (Sb), tellurium (Te), barium (Ba), mercury (Hg) and lead (Pb) in food samples by inductively coupled plasma-mass spectrometry (ICP-MS) after closed-vessel microwave digestion. This validation was realized in parallel with the analysis of the 1322 food samples of the second French Total Diet Study (TDS) by the National Reference Laboratory (NRL) of the French Food Safety Agency (AFSSA). Several criteria such as linearity, limits of quantification (LOQ), specificity, precision under repeatability conditions and intermediate precision reproducibility were evaluated. Furthermore, the method was supervised by several internal and external quality controls (IQC and EQC). Results indicate that this method could be used in the laboratory for the routine determination of these 21 essential and non-essential elements in foodstuffs with acceptable analytical performance.     

Nanofluid extraction of Ochratoxin A in food

Monitoring of Ochratoxin A (OTA), a toxic and carcinogenic metabolite of fungi, requires accurate and precise analytical methods. Quantitative determination of OTA at trace level in raisin samples was evaluated by nanofluid extraction coupled with HPLC–FLD. The experimental parameters affecting the extraction efficiency of OTA were investigated and optimized. The validated method has low detection and quantification limit (0.2 and 0.5 ng g⁻¹). Moreover, under optimum conditions, the repeatability of the method expressed as the relative standard deviation for intra-day and inter-day precision (RSD %) was below 15 % (n = 3). This method has also been successfully applied to the analysis of trace amounts of OTA in real samples with satisfactory relative recoveries in the range of 70.3–84.7 %.     

Determination of trace nickel in chamomile tea and coffee samples by slotted quartz tube-flame atomic absorption spectrometry after preconcentration with dispersive liquid-liquid microextraction method using a Schiff base ligand

In the present study, an accurate and selective preconcentration/extraction method was developed for the determination of nickel at trace levels. Slotted quartz tube flame atomic absorption spectrometry (SQT-FAAS) combined with dispersive liquid-liquid microextraction (DLLME) was used to obtain a very low detection limit for nickel. A Schiff base ligand derived from the reaction of 5-bromosalicylaldehyde and o-phenylenediamine was used for the formation of a coordinate nickel complex. Under the determined experimental conditions, the detection and quantification limits of the DLLME-SQT-FAAS system were calculated as 4.9 and 16.4 ng/mL, respectively. Satisfactory analytical performance values of the SQT-FAAS, DLMME-FAAS and DLLME-SQT-FAAS methods were obtained and 1.8, 32.0, 66.4-fold enhancements in detection power were respectively obtained over the conventional FAAS system. The percent recovery ranges obtained for two different spike concentrations were 88.1–113.2% and 102.1–120.2% for coffee and chamomile tea samples, respectively.     

超高效液相色谱法测定食品中的多种防腐剂

目的:建立了超高效液相色谱(UPLC)法测定食品中14种防腐剂的定性定量分析方法。方法:样品用饱和氯化钠、乙腈、正己烷3种溶液萃取提取,正己烷提取溶液经凝胶渗透色谱(GPC)净化后与乙腈提取溶液合并注入超高效液相色谱分析。14种化合物经ACQUITY UPLCTMBEH C18柱(150 mm×2.1 mm,1.7μm)柱分离,以乙酸铵-乙腈溶液作为流动相进行梯度洗脱,紫外检测器(UV)检测,检测波长为280 nm。结果:14种化合物在线性范围内具有较好的线性关系,相关系数(r)>0.99,定量限(LOQ)在0.01 mg/kg～0.6 mg/kg之间;空白样品添加回收率在63.4%～99.5%之间,精密度(RSD)在0.490%～16.3%之间。结论:该方法适用于食品中防腐剂的检测。     

Development of a reversed phase-high performance liquid chromatographic method for the analysis of glucosamine sulphate in dietary supplement tablets

Glucosamine sulphate can be taken orally from the dietary supplement tablets for the treatment of osteoarthritis. In these tablets, the determination of glucosamine sulphate concentration is very important for the identification of fraudulent products and quality-control studies. In this study, a simple, rapid, accurate and sensitive method was developed for the determination of glucosamine sulphate in the dietary supplement tablets by using isocratic reversed-phase high-performance liquid chromatography with diode array detector (RP-HPLC-DAD). The separation process was performed by Prodigy™ C18 reversed-phase column using an acetonitrile:H₂O mixture (50:50 (v/v), pH 4.0) as mobile phase. The method developed was optimized and subsequently validated. Method validation was performed to illustrate the reliability of new analytical method through various validation parameters including linearity, precision, accuracy, limit of detection (LOD), limit of quantification (LOQ), selectivity and stability. Relative standard deviation (%) values for the intra-day and inter-day precision studies were low. The calibration curve was linear in the glucosamine sulphate concentration range of 0.05-2.5 mg.L^-1. In this method, recovery values were obtained in the range between 85.15% and 118.86% and LOD and LOQ values were determined to be 0.014 mg.L^-1 and 0.046 mg.L^-1, respectively. Furthermore, all results confirmed that the new method is suitable for the determination of glucosamine sulphate in dietary supplement tablets.     

Spectrophotometric determination of aflatoxin B1 in food sample: Chemometric optimization and theoretical supports for reaction mechanisms and binding regions

A green, simple, and cheap analytical approach for extraction, preconcentration, and determination of aflatoxin B1 (AFB1) in food samples based on vortex-assisted room temperature ionic liquid-based microextraction (VA-RTIL-ME) was presented. Important parameters including pH, metal amount, ligand amount and vortex time were optimized by using Box–Behnken design. At pH = 5.6, a ternary complex between Zn(II), fluorescein and AFB1 was formed, and extracted into the fine droplets of Tri-n-butyl phosphate (room temperature ionic liquid, extraction solvent) which were dispersed with a vortex (disperser solvent) into the extraction solution. Quantum chemical parameters and tools are widely used to predict the reaction mechanisms of interactions and binding regions of molecules. Via calculated quantum chemical parameters and energy calculations, reactions mechanisms and binding regions for studied molecules were highlighted. Under optimized conditions, linear range, limit detection, enrichment factor were 3–500 ng mL^-1, 0.9 ng mL^-1 and 140, respectively. Detailed validation studies (accuracy, precision, measurement uncertainty, selectivity, robustness..etc.) were performed under optimum experimental conditions. The good recoveries (93.9–104.3%) and low relative standard deviation (RSD%, 1.5-3.0%) were a good remark of the proposed method. For the reliability of analytical results, the results obtained with the developed method were compared with the standard ELISA test for AFB1. The developed method was successfully applied to the extraction and determination of AFB1 in food samples.     

On the electrochemical biosensing of phenolic compounds in wines

A simple electrochemical sensor based on polyphenol oxidases was proposed for determination of the total phenol content in wine. Application of two oxidases: tyrosinase and laccase (separately) was examined and the results were compared. An analytical characteristic of proposed sensor towards gallic acid was evaluated. The influence of sample matrix components on the sensor response was studied according to Plackett–Burman experimental design. The potential interferents ethanol, tartaric acid, sorbate, sulfate(IV), putrescine, Fe(III) and glucose, which are usually encountered in wines, were taken into account in the examination. Because of the significant matrix effect found, analyses of wine samples towards polyphenol contents were carried out using standard addition method and expressed as gallic acid equivalents. For comparative quantification of phenolic compounds well-established Folin–Ciocalteu spectrophotometric method was applied. Significant inter-method differences were observed in electrochemical behaviour of standard substance – gallic acid – and phenolic constituents of real wine samples in the presence of tartaric acid.     

Validation of an ICP-OES method for macro and trace element determination in Laminaria and Porphyra seaweeds from four different countries

An Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) method for speedy simultaneous determination of 12 elements (Al, Ba, Ca, Cu, Fe, K, Mg, Mn, Na, P, Sr and Zn) in seaweeds used as human food was optimized and then validated according to Eurachem guidelines. First, instrumental parameters (nebulizer argon flow rate and incident power) were optimized and then analytical lines free from spectral interferences were selected. The method was validated using biological Certified Reference Materials (CRMs). Intra- and inter-assay precision varied from 0.79% to 5.74% and from 2.48% to 8.57%, respectively, depending on the element studied. Within the experimental error, concentrations measured for each element coincided with certified values. Sensitivities, linearity and detection and quantification limits were also determined. Samples of seaweeds (Porphyra and Laminaria) from France, Spain, Korea and Japan were analyzed by using the optimized and validated method. Some considerations on element composition of analyzed samples were made. Seaweeds from the Korean and Japanese coasts tended to display the highest concentrations of P and Al. In contrast, French Porphyra samples showed the lowest levels of Ba, Cu, Fe and Mn. Because great differences in element concentrations were observed due to costal origin and genus, any generalization regarding the algal mineral content may be considered misleading and scientifically inappropriate.     

Paper spray ionization mass spectrometry: Study of a method for fast-screening analysis of pesticides in fruits and vegetables

New faster and simpler methods for determination of pesticides in agricultural products are necessary as requirements for food safety are becoming increasingly stringent. One possibility is to introduce a fast, easy and low-cost screening method before liquid chromatography mass spectrometry analyses. We hereby present a systematic proof of concept study of paper spray mass spectrometry method for pesticide detection as a screening method. Two sampling approaches – wiping the surface with paper and applying the sample homogenate directly on the paper – were used. The wiping method was more extensively studied for imazalil and thiabendazole originally present in oranges. For homogenized samples three matrices – oranges, tomatoes and grapes – and five pesticides of different chemical nature and polarity – thiabendazole, aldicarb, imazalil, methomyl and methiocarb – were chosen. It has been shown that limits of detection below maximum residue levels can be achieved for both methods (e.g. imazalil and thiabendazole detection limits were found to be lower than 5 mg/kg). The methods are therefore suitable for fast screening of samples. Moreover, the wiping method was also applied for 11 samples – oranges, grapefruits, lemons, limes, mandarins, tomatoes, apples, pears, strawberries, grapes and sweet peppers – from the local supermarket to screen for different pesticides. Three positive samples for thiabendazole and imazalil and one positive sample for imazalil were found.     

Laboratory and field validation of a JXC charcoal sampling and analytical method for monitoring short-term exposures to ethylene oxide

A sampling and analytical method for the measurement of ethylene oxide (EtO) short-term exposure limits (STEL) was validated under both laboratory and field conditions. These studies were designed to examine the method against both the Occupational Safety and Health Administration (OSHA) EtO permissible exposure limit (PEL) method requirements and the National Institute for Occupational Safety and Health (NIOSH) industrial hygiene method validation criteria. The method's pooled accuracy was shown to be within both OSHA requirements and NIOSH guidelines. The EtO was collected on a JXC charcoal tube at a sample flow rate of 100 mL/min for 15 min. The samples were shipped on dry ice and were stored in a freezer until analyzed. The EtO was desorbed by carbon disulfide and the eluent was analyzed by gas chromatography with flame ionization detection (GC-FID). The desorption efficiency of EtO from JXC charcoal tubes was determined to be 84% over the 15-min time-weighted average concentrations: 2.5, 5.0 and 10 ppm EtO. The method limit of detection was determined to be 1.0 ppm. The coefficient of variation of the combined sampling and analytical method was 5.7%. A -7% method bias was calculated. Field validation of the method included data from a portable GC-FID for the determination of method bias. Results of the field validation study over the concentration range of 2.4 ppm to 19.9 ppm generated a field precision of 8.1% with an absolute bias of 3.9%. The method accuracy was determined to be +/- 20%.(ABSTRACT TRUNCATED AT 250 WORDS)     

A rapid method for simultaneous determination of nitrate,nitrite and thiocyanate in milk by CZE-UV using quaternary ammonium chitosan as electroosmotic flow inverter

This paper proposes a rapid method for the simultaneous determination of nitrate, nitrite and thiocyanate in different milk samples (cow, goat and soy) using capillary zone electrophoresis. The separations were conducted in a fused silica capillary dynamically coated with quaternary ammonium chitosan, with a total length of 48.5 cm (40 cm effective x 75 μm internal diameter) and direct detection in the UV region at 210 nm. The background electrolyte (BGE) was composed of 30 mmol L⁻¹ of aminocaproic acid and 24 mmol L¹ of perchloric acid (pH 3.85).A typical anodic electroosmotic flow of -31 × 10^-9 m² V⁻¹ s⁻¹ was observed at the pH of the separations. Bromate was used as the internal standard. The samples were injected by hydrodynamic pressure (50 mbar, 40 s) and the separation voltage was −30 kV. The proposed method was validated and presented good linearity (R²> 0.99) in the linear range of 0.1–4.0 mg L⁻¹. The ranges of the limit of detection (LOD) and limit of quantification (LOQ) were 0.03-0.04 and 0.05–0.07 mg L⁻¹, respectively. The intra-day and inter-day precision values were better than 4.2 and 8.7 %, respectively. Recovery values ranged from 85 to 104% for the different samples of milk. The proposed method was applied in 12 commercial samples with run times of less than 2 min. The good analytical performance indicates that the method proposed is a promising alternative for the determination of nitrate, thiocyanate and nitrite in milk samples.     

In-house method validation: Application in arsenic analysis

A detailed procedure for in-house method validation was proposed and applied to the validation of a method for determination of arsenic in bovine liver. Linearity and matrix effects were assessed by solvent and matrix-matched curves. Data were fitted by ordinary least squares method (OLSM). Violations of assumptions underlying OLSM residuals (normality, independence and homoscedasticity) were evaluated. F-tests were undertaken to check the adjustment to the model by evaluation of regression and lack of fit significances. The slopes and interceptions were compared for significant differences by t-test. Linearity was demonstrated and significant matrix effects were not observed between 0.5 and 8 ng mL⁻¹. Selectivity, trueness, precision and experimental limits of the method were established by assays with blanks and spiked samples. Recovery (means of 88.9–99.9%) was calculated and analysis of variance was carried out to estimate the standard deviation under repeatability (3.7–7.2%) and within-reproducibility (3.7–7.3%) conditions. The spiking experiments indicated precision and no lack of trueness. Experimental limits of detection and quantification were 15 and 30 μg kg⁻¹, respectively. The procedure was found to be suitable for in-house validation with respect to the evaluation of efficiency parameters, ease of application and cost-benefits.     

Rapid assessment of metal contamination in commercial fruit juices by inductively coupled mass spectrometry after a simple dilution

A simple and fast method for the determination of Ca, Cd, Co, Cu, Fe, Mn, Mo, Na, Ni, Pb, Rb, Sr, V and Zn in fruit juices samples, by inductively coupled plasma mass spectrometry (ICP-MS) after only a sample dilution, is proposed. For comparison, the samples were also digested with nitric acid and hydrogen peroxide in a microwave oven. The same conditions could be used for aqueous standard solution and diluted sample and the sensitivity was similar in both media, thus external calibration against aqueous standard solutions could be used for quantification. The results were in agreement with those obtained after digestion, according to the t-test at a 95% confidence level. The good accuracy was also confirmed by the recovery test. The precision expressed by the relative standard deviation (RSD) was between 1 and 3%. The detection limits were between 0.1 (Pb) and 2000 μg L⁻¹ (Ca). Similar values for detection limits and RSD were obtained after sample digestion or when the internal standard was not used. The compositions of 20 samples were evaluated by multivariate analysis techniques: principal component analysis (PCA) and hierarchical cluster analysis (HCA), showing that samples are grouped by the brand and not by the fruit, what could be due to soil characteristics where the plant was grown and to the different processing and storage conditions used by the different brands, including water and additives.     

Simultaneous enrichment/determination of six sulfonamides in animal husbandry products and environmental waters by pressure-assisted electrokinetic injection coupled with capillary zone electrophoresis

Pressure-assisted electrokinetic injection (PAEKI) as the online method was developed for the simultaneous enrichment of six sulfonamides (SAs), including sulfamethazine (SMZ), sulfamerazine (SMR), sulfamonomethoxine (SMM), sulfadizine (SDZ), sulfamethoxazole (SMX) and sulfacetamide (SFA) in different animal husbandry products and environmental waters samples, followed by capillary zone electrophoresis (CZE) determination. Various parameters affecting the separation performance of CZE and the enrichment efficiency of PAEKI were optimized in detail. Under optimal conditions, the six SAs were completely separated within 8.5 min, and the enrichment factors for SMZ, SMR, SMM, SDZ, SMX and SFA were 39, 47, 53, 50, 54 and 62 folds, respectively, compared with the direct CZE. The limits of detection (LOD) ranged from 0.0018–0.0163 μg/mL, 0.0083–0.0638 μg/mL and 0.0052–0.0478 μg/mL in milk, pork and egg samples, respectively, as well as limits of quantification (LOQ) within 0.0061–0.0503 μg/mL, 0.0253–0.1826 μg/mL and 0.0164–0.1475 μg/mL, respectively. Tap water, lake water and seawater were also examined for investigation of applicability of the proposed method. Satisfactory recoveries in the range of 89–113 % were obtained with the three spiked food samples, and the relative standard deviations were from 1.6 to 7.3%. Simple and effective online enrichment method provides a promising perspective for CZE measurements of SAs in complex matrices with high accuracy, sensitivity and rapidity.     

Direct atomic absorption spectrometry determination of arsenic,cadmium, copper,manganese, lead and zinc in vegetable oil and fat samples with graphite filter furnace atomizer

The article presents the results of optimization of operation parameters, investigation of analytical characteristics and the abilities of a graphite filter-furnace (FF) atomizer for the direct electrothermal atomic absorption spectroscopy (ET AAS) determination of trace amounts of Mn, As, Pb, Cu, Cd and Zn in some vegetable oils and fats. The effect of pyrolysis and atomization temperatures of the graphite FF atomizer on atomic absorbance values of the listed elements at their evaporation from some organic solutions in the presence of a Pd-Mg chemical modifier (CM) was investigated. For the ET AAS determination of As, Pb, Cd and Zn with Pd-Mg CM, the temperature of the graphite FF atomizer for the pyrolysis step can be raised by 250–350 °C. This mode allows to eliminate the background absorption, to increase the sensitivity of the elements to be analyzed and to enhance the total content of vegetable oils or fats in organic solutions up to 0.5 g mL⁻¹. The obtained limits of quantification for Mn, As, Pb, Cu, Cd and Zn were 0.002, 0.004, 0.004, 0.002, 0.0008, 0.0004 mg kg⁻¹, respectively. The relative standard deviation (RSD) varied between ∼3 and 8% and the time of one element determination did not exceed ∼3–5 min. The reliability of the proposed method was checked using the reference method. A paired Student's t-test showed no significant difference between the results obtained by both methods on a 95% confidence level.     

Environmental sampling and analysis for zeranol

Due to concern over health effects associated with the use of zeranol, a sampling and analytical method to monitor zeranol in the work environment was developed. The collection strategy included air samples on FHLP filters, area samples on gauze pads, hand/dermal samples on gauze pads and bulk samples. The sampling method evaluation included choice of media, flow rate and duration for air samples, sample preparation, extraction efficiencies and sample stability. Analysis of the samples was accomplished by high performance liquid chromatography with identification and quantification by UV and fluorescence detection. The analytical method evaluation included separation of possible interfering compounds, calibration curves, limits of detection (LOD), limits of quantitation (LOQ), precision and accuracy. The tested analytical range was 0.01 to 150 micrograms/mL with a LOD of 0.007 microgram/mL and a LOQ of 0.02 microgram/mL using UV detection. For the fluorescence detector, the LOD was 0.05 microgram/mL and the LOQ was 0.15 microgram/mL. Peak confirmation was achieved by retention time and comparing the two detector responses. Use of this method provided the sensitivity and specificity to analyze environmental samples for zeranol in the workplace environment.     

Drinking water,diet, indoor air: Comparison of the contribution to environmental micropollutants exposure

This study collated 254,441 analytical results from drinking water quality monitoring in order to compare levels of exposure of the French adult population from drinking water with that from total diet for 37 pesticides, 11 mineral elements, 11 polycyclic aromatic hydrocarbons (PAH), 6 non dioxin-like polychlorobiphenyls (NDL PCB), 5 ether polybromodiphenyl ethers (BDE), 2 perfluorinated compounds. It also compares levels of exposure from drinking water with that from inhalation of indoor air for 9 volatile organic compounds (VOC) and 3 phthalates. The vast majority of the water analysis results showed values below the limits of quantification and this comparison was primarily made on the basis of a highly pessimistic scenario consisting in considering the data below the limits of quantification as being equal to the limits of quantification. With this conservative scenario, it can be seen that tap water makes a minor but potentially non-negligible contribution for a few micropollutants, by comparison with diet and air. It also shows that exposure through drinking water remains below the toxicity reference values for these substances. Apart from a few extreme values reflecting exceptional local situations, the concentrations measured for the minority of positive samples (below the 95th percentile value) suggest a very low risk for human health. Lower limits of quantification would however be of use in better estimating the safety margin with regard to the toxicity reference values, in particular for BDE, PAH and NDL PCB.     

Zirconium nanoparticles based ligandless dispersive solid phase extraction for the determination of antimony in bergamot and mint tea samples by slotted quartz tube-flame atomic absorption spectrophotometry

A sensitive and effective analytical method was developed to preconcentrate antimony from the bergamot and mint tea samples for its determination at trace levels by slotted quartz tube-flame atomic absorption spectrophotometry (SQT-FAAS) system. The developed method was based on vortex assisted ligandless dispersive solid phase extraction (VA-LDSPE) using zirconium nanoparticles (Zr-NPs) as sorbent material for the adsorption of the target analyte. All variables involved in the DSPE method (pH value, nanoparticle amount, mixing and eluent type/volume) were optimized to boost the absorbance signal of antimony. Using the optimal parameters, the method provided satisfactory detection and quantification limits of 8.0 and 26.8 μg L⁻¹, respectively. A 180 folds enrichment factor was achieved by the developed method when compared with the detection power of the FAAS. Linear range of the proposed method was found to be 30–250 μg L⁻¹, with a coefficient of determination value of 0.9992. The established Zr-NPs-VA-LDSPE-SQT-FAAS method was successfully implemented to bergamot tea samples in order to check accuracy and applicability. The obtained recovery values ranged between 93–102%, and this demonstrated that the complex matrices tested did not affect the accuracy of quantifying antimony.     

Laboratory and field validation of the GC-NPD method for the measurement of formaldehyde in the workplace

Formaldehyde is classified as a suspected or probable human carcinogen by several organizations. Since conventional sampling and analytical methods for airborne formaldehyde show relatively poor sensitivity, an improved method is needed. The aim of this study was to develop a new analytical method for measuring the airborne formaldehyde concentrations in workplaces and to evaluate the performance of the method through laboratory and field tests. The method employs a sampling tube containing silica gel coated with 2, 4-dinitrophenylhydrazine (2,4-DNPH), which produces 2,4-DNPH-formaldehyde derivative with formaldehyde. Then the 2,4-DNPH-formaldehyde derivative is analyzed using gas chromatography (GC) equipped with a nitrogen-phosphorus detector (GC-NPD). In laboratory tests, the new method, referred to as the GC-NPD method, was as sensitive as the National Institute for Occupational Safety and Health (NIOSH) analytical method, which uses high-performance liquid chromatography equipped with ultraviolet detector. The total analytical precision and 95% confidence limit of the estimated total standard error for the GC-NPD method were 0.009 and +/- 12.0%, respectively, which satisfied the OSHA sampling and analytical criteria. In field tests, the overall uncertainty of the GC-NPD method was 11.2%, which satisfied the NIOSH criteria for sampling and analytical methods. The GC-NPD method with a 2,4-DNPH coated adsorbent sampler for the determination of airborne formaldehyde concentration showed good performance with acceptable accuracy and precision.