Determination of Cd and Pb in Honey by SF‐ICP‐MS: Validation Figures and Uncertainty of Results

Abstract

A method based on microwave‐assisted acid digestion of honey and quantification of Cd and Pb by Sector Field Inductively Coupled Plasma Mass Spectrometry was in‐house validated and the combined uncertainty was estimated according to the Eurachem/Citac Guide. Limits of detection and quantification were 0.07 and 0.20 ng g^?1 for Cd, and 0.70 and 2.10 ng g^?1 for Pb; recovery was 103.9% for Cd and 98.5% for Pb; repeatability was 10.7% for Cd and 18.5% for Pb; within‐laboratory reproducibility was 15.2% for Cd and 21.4% for Pb. Relative combined uncertainty in honey was 15% for Cd and 22% for Pb, with the main contribution coming from the within‐laboratory reproducibility. The method showed robustness when subjected to different working conditions and when applied to various Italian honeys. Cadmium content ranged 0.2–1.37 ng g^?1 and Pb 4.6–30.5 ng g^?1 in flower honeys, while the highest concentrations were presented by honeydew honeys.     

Atomic absorption spectrometric determination of selenium with carbon furnace atomization

A Varian Techtron model 63 carbon rod atomizer is used for the atomic absorption spectrometric determination of nanogram quantities of selenium. The pronounced interferences from the matrices in biological digests can be obviated by isolating selenium from sample matrices by precipitation with ascorbic acid. The precision of the determination is improved by incorporating 5000 μg Ni ml^?1 in the analytical solutions. Selenium at μg g^?1 and sub-μg g^?1 levels in a variety of biological samples can be determined. The detection limit is 25 ng Se g^?1.     

Selenium determination in cereal plants and cultivation soils by radiochemical neutron activation analysis

Selenium (Se) is an essential micronutrient for human health but it is deficient in at least 1?billion people around the globe. Cereals are by far the most significant agricultural crops, not only on a gross tonnage basis, but also by what they represent in terms of energy supply and dietary intake for human nutrition worldwide. Portugal is no exception to such pattern. The Portuguese situation is difficult to assess though, due to scarce information and lack of consistent studies on the subject. In these terms, the Se status of major cereals and their cultivation soils are dealt with herein. Two species of wheat?Cbread and durum wheat?Cwere sown at the end of November 2009, and then sampled in different growth stages. Rye was collected during harvest season, and cultivation soils were analyzed as well. Se results were within the range of: 100?C225?ng?g^?1 for soils; 3?C55?ng?g^?1 for durum wheat; 6?C80?ng?g^?1 for bread wheat; and 4?C30?ng?g^?1 for rye. Accuracy of the RNAA procedure was proved by analysis of reference materials NIST-SRM 1515 and NIST-SRM 8433.     

Validation of a highly sensitive method for the determination of neonicotinoid insecticides residues in honeybees by liquid chromatography with electrospray tandem mass spectrometry

The validation of a multi-residue method for the determination of five neonicotinoid insecticides (imidacloprid, clothianidin, acetamiprid, thiacloprid and thiamethoxam) in honeybees is described. The method involves the extraction of pesticides using acetonitrile and liquid partitioning with n-hexane. One clean-up is then performed on a florisil cartridge (1?g, 6?mL) and the extract is analysed by liquid chromatography-electrospray ionisation-tandem mass spectrometry (LC-ESI-MS/MS). The recovery data were obtained by spiking honeybees samples free of pesticides at two concentration levels of the various neonicotinoids. The recoveries were in the range between 93.3 and 104.0% with relative standard deviation (RSD) less than 20%. The limit of quantification (LOQ) was 0.5?ng?g^?1 (corresponding to 0.05?ng?bee^?1) for all pesticides except for acetamiprid which was 1?ng?g^?1 (corresponding to 0.1?ng?bee^?1).     

Micro Dry Ashing for Trace Selenium Determination in Organic Matrices

Abstract

A specific sample treatment method was established for determination of ng levels of Selenium in microquantities of organic compounds. Our task was determination of Selenium traces, in a new pharmaceutical product, as a result of a laboratory scale synthesis, in an amount of several tens of mg. GFAAS was chosen as an analysis method, due to its sensitivity and rapidity. Among the wet and dry methods for organic material digestion tried, the low temperature dry ashing using ashing aid, was the only one which gave satisfactory recoveries of Selenium. Micro dry ashing was performed, using an Ethanol solution of Magnesium Nitrate on samples spiked with Selenium Nitrate in the range of concentration of 1–6ng mg^?1 at a temperature of 450°C for two hours. The presence of Magnesium Nitrate and the heating suppress the atomization with approximately 15–25%. Recoveries of Selenium varies as a function of the organic matrix: for polyaromate compounds as Chrysene and Fluoranthene they lie between 90–103% and for oxygenated compounds as Dimethoxybenzoic acid or Phthalates 23–50% respectively.

Another aspect of chemical interference by organic matrices and the way how to overcome it, has been clarified.     

Determination of seven trace elements in natural waters by neutron activation analysis after preconcentration with 1-(2-pyridylazo)-2-naphthol

A procedure is described for the preconcentration of Cd(I), Co(II), Cr(III), Cu(II), Mn(II), U(VI) and Zn(II) from 800 ml of water and sea-water samples by coprecipitation with 1-(2-pyridylazo)-2-naphthol (PAN) prior to neutron activation. Chromium is reduced to Cr(III) by hydroxylammonium chloride at pH 4 before the preconcentration step. Coprecipitation of 30 mg of PAN was most effective at pH 9 with final recoveries of 76–91% for six elements and 50% for uranium. The scheme is based on double irradiation of the same samples. Short (10 min) irradiation followed by γ-spectrometry counting for 10 min gives data for Cd (^111mCd), Co, Cu, Mn and U (²³⁹U). A second 16-h irradiation permits determination of zinc and uranium (²³⁹Np) after a waiting time of 6 h, cadmium (¹¹⁵Cd) after 24 h and chromium after a waiting period of 2 weeks followed by counting for 30 min. Detection limits are 0.04 ng g^?1 for Co, 0.8 ng g^?1 for Cd, 0.3 ng g^?1 for Cu, 0.2 ng g^?1 for Cr, 0.006 ng g^?1 for Mn, 0.006 ng g^?1 for U and 0.3 ng g^?1 for Zn. A further decrease of the detection limit for chromium to 0.05 ng g^?1 can be achieved by separation of interfering nuclides and scintillation counting of ⁵¹Cr with a NaI(Tl) well-type detector.     

Working Methods Paper: Certification of methylmercury compounds concentration in marine sediment reference material,IAEA-356

An intercomparison exercise was organized between seven laboratories using various isolation procedures (extraction, distillation, ion-exchange and alkaline digestion) and detection systems (CV AAS, cold vapour atomic absorption spectroscopy; CV AFS, cold vapour atomic fluorescence spectroscopy; GC, ECD, gas chromatography electron capture detector and HPLC with CV AFS detection) for determination of methylmercury compounds in sediment sample. All certification criteria were fulfilled and therefore the value for total concentration of methylmercury compounds was certified to be 5.46 ng g^?1, with a 95% confidence interval from 4.07–5.84 ng g^?1. The acceptable range, calculated as two times the confidence interval of the mean is therefore from 4.68–6.23 ng g^?1. This is the first sediment reference material ever to be certified for concentration of methylmercury compounds. Comparison of the data obtained by various methodologies has shown that the most critical step is the isolation of methylmercury compounds from binding sites. Acid leaching only cannot release methylmercury compounds quantitatively. Total release of methylmercury compounds could only be achieved by alkaline digestion or distillation. This simple intercomparison exercise has shown that since large numbers of laboratories world-wide are performing methylmercury compound analyses using various improved and specific separation methods and sensitive detection systems, certification of methylmercury compounds in different biological and environmental samples should not be a problem in the future.     

A novel approach to decomposition of foodstuffs for stripping voltammetric determination of lead,cadmium and copper

Samples (ca. 0.3 g) are digested in 10-ml quartz vessels and the same vessel is used for anodic stripping voltammetry. Thus possible contamination during handling and dilution of the decomposed sample solution are avoided. A special design of column placed over the vessel provides digestion under reflux conditions without leakage and a glass cap fitted to another condenser enables the residual mineral acids (especially sulfuric acid) to be boiled out under low pressure conditions. The usual PTFE holder for electrodes and gas tubes is modified to facilitated insertion of the 10-ml vessel underneath. The system was checked on NBS standard reference materials (wheat flour and rice flour) and tested for the determinaton of Cd, Pb and Cu in baby foods. The limits of detection obtained for 3-min decomposition times were 0.3 ng g^?1, 4 ng g^?1 and 8 ng g^?1 for cadmium, lead and copper, respectively. The levels of these elements in various commercial baby foods are given.     

Validation of a multiresidue method for the determination of pesticides in honeybees by gas chromatography

The validation of a multiresidue method for the determination of organochlorine, organophosphorus, pyrethroid and dicarboximide pesticides in honeybees is described. The method involves the extraction of 25 pesticides using acetonitrile, liquid partitioning with n-hexane and a clean-up performed on a silica gel cartridge (1 g, 12 mL). Capillary gas chromatography with electron-capture and nitrogen–phosphorus detectors was used for analytes determination. Limit of quantification (LOQ), recovery and relative standard deviation (RSD) for each analyte were determined. The recovery data were obtained by spiking honeybee samples free of pesticides at three levels (LOQ, 4LOQ and 8LOQ) with organochlorine, organophosphorus, pyrethroid and dicarboximide pesticides. The recoveries were in the range between 90.0% and 101.5% for LOQ, between 90.3% and 104.8% for 4LOQ and between 88.1% and 101.6% for 8LOQ with RSD less than 20% for the three levels tested. The lowest LOQ value was 1 ng bee^?1 (corresponding to 10 ng g^?1) and the highest LOQ value was 10 ng bee^?1 (corresponding to 100 ng g^?1). These LOQ values are lower than the lethal doses LD₅₀ (acute contact toxicity and acute oral toxicity) of each pesticide for bees.     

Validation of a novel derivatization method for GC–ECD determination of acrylamide in food

This paper proposes a new method for quantitative analysis of acrylamide in cereal-based foods and potato chips. The method uses reaction with trifluoroacetic anhydride, and analyses the resulting derivative by use of gas chromatography with electron-capture detection (GC–ECD). The effects of derivatization conditions, including temperature, reaction time, and catalyst, on the acylation reaction were evaluated. Chromatographic analysis was performed on an SE-54 capillary column. Under the optimum conditions, good retention and peak response were achieved for the acrylamide derivative. The analytical method was fully validated by assessment of LODs and LOQs (1 ng g^?1 and 25 ng g^?1, with relative standard deviations (RSD) 2.1 and 3.6, respectively), linearity (R?=?0.9935 over the range 0.03–10 μg g^?1), and extraction recovery (>96 %, with RSD below 2.0, for acrylamide spiked at 1, 20, 50, and 100 ng g^?1; 99.8 % for acrylamide content >1000 ng g^?1). The method requires no clean-up of the acrylamide derivative before injection. The method has been successfully used to determine acrylamide levels in different commercial cereal-based foods, French fries, and potato chips.

Synthesis of derivatives and production of antiserum for class specific detection of pyrethroids by indirect ELISA

Two series of haptens including 3-phenoxybenzoic acid (PBA) and 3-(2-chloro-3, 3,3-trifluoroprop-1-enyl)-2,2-dimethylcyclo-propanecarboxylic acid (CF₃MPA) were used to prepare immunogens through attachment of 4-C or 6-C handles. Class selective antibodies were produced by immunising rabbits. Ab502 showed the highest reactivity towards tau-fluvalinate (IC₅₀ 1.3 ng mL^?1), λ-cyhalothrin (IC₅₀ 2.3 ng mL^?1), cyfluthrin (IC₅₀ 2.2 ng mL^?1) and fenpropathrin (IC₅₀ 18.5 ng mL^?1) among the antibodies in a competitive ELISA. The effects of methanol, pH and salt concentration were optimised for maximum efficiency of the ELISA (Enzyme-Linked ImmunoSorbent Assay). Ab502 (1:80000)/2-OVA-1(0.2 µg mL^?1) was chosen for ELISA optimisation. Finally, 0.05 M phosphate buffered saline (PBS) at pH 6.5 containing 30% methanol (v/v) was used to dilute the standards. Target analytes in honey samples were extracted with ethyl acetate by sonication. The samples were spiked with three different concentrations of each compound (tau-fluvalinate, 0.5 ng g^?1, 3 ng g^?1, 12 ng g^?1; λ-cyhalothrin and cyfluthrin 1 ng g^?1, 5 ng g^?1, 65 ng g^?1). The recoveries were 36–59% at the lowest spiking concentration and 61–81% at the higher concentration. This assay might be useful to screen pyrethroid residues in honey or other matrix.     

A critical study on the determination of selenium in gallium arsenide by polarographic techniques

A simple voltammetric method is described for the determination of traces of selenium in gallium arsenide. Differential-pulse cathodic stripping voltammetry permits a direct determination of selenium without preliminary enrichment or separation processes. Selenium can be determined down to levels of 1–2 μg g^?1, with relative standard deviations of about 10%, in ? 100-mg samples of gallium arsenide. Results for gallium arsenide doped with 7–75 μg g^?1 selenium agree in most cases with those obtained by spectrophotometry based on 4-chloro-o-phenylenediamine.     

Ionic alkyl-lead,tetra-alkyl-lead and total lead in fish from the Great Lakes

Fillets from a variety of fish species collected from Lakes Ontario, Superior and Erie, Canada, were examined for ionic alkyl-lead, tetra-alkyl-lead and total lead compounds. Diphenylthiocarbazone (dithizone)-derivatized extracts were collected at pH 8 and 9 for ionic alkyl-leads from enzymatically hydrolyzed samples. Butylated derivatives were formed prior to analysis by gas chromatography-atomic absorption spectrometry (GC AA). Tetra-alkyl-lead was extracted from the hydrolyzates with hexane. Most of the fillets contained low (<0.08–2 ng g^?1) levels of trimethyl-lead. Several samples contained triethyl-lead or tetraethyl-lead. Dimethyl-lead, diethyl-lead and tetramethyl-lead were detected by GC MS but were below the GC AA method detection limit of 0.06 ng g^?1, 0.09 ng g^?1 and 0.2 ng g^?1 respectively. Total lead levels were between <1.8 and 96.7 ng g^?1.     

Single robust RP-HPLC analytical method for quantification of curcuminoids in commercial turmeric products,Ayurvedic medicines,and nanovesicular systems

A single robust reversed-phase high-performance liquid chromatography (RP-HPLC) method was developed and validated as per International Conference on Harmonization guidelines for the accurate quantification of curcuminoids in commercial turmeric products, Ayurvedic medicines, and nanovesicular systems. The proposed chromatographic method was found to be specific, linear (r²?≥?0.999), precise at intra- and inter-day levels (percentage relative standard deviation <2.0%), accurate (percentage recovery 99.14–102.29%), and robust. The limits of detection and quantification were found to be 7.40 and 24.70?ng?mL^?1 for curcumin, 9.24 and 30.80?ng?mL^?1 for demethoxycurcumin, and 6.48 and 21.61?ng?mL^?1 for bisdemethoxycurcumin, respectively. Among different commercial turmeric products and Ayurvedic medicines tested, the contents of curcumin (3.54?±?0.06–25.8?±?0.08?mg?g^?1), demethoxycurcumin (1.28?±?0.02–9.97?±?0.03?mg?g^?1), and bisdemethoxycurcumin (0.50?±?0.01–5.97?±?0.01?mg?g^?1) varied significantly. The developed method was effectively applied to the determination of encapsulation efficiency of curcuminoids (ranged between 84.33?±?3.50 and 96.59?±?2.53%) in the nanovesicular systems. In conclusion, the reported method is suitable for the analysis of curcuminoids in a wide variety of turmeric products and used for the quality control of products that contain curcuminoids.     

Determination of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) in food and beverages

The determination of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonate (PFOS) in food and beverages sold in Turkey was carried out using liquid chromatography–tandem mass spectrometry (LC-MS/MS). A total of 123 samples of selected food and beverages such as fish, meat, offal, egg, cracker, chips, cake, chocolate, vegetable, milk and juice were examined. The highest PFOA concentrations were determined in cow meat (5.15 ng g^?1), cow kidney (5.65 ng g^?1), cow spleen (5.06 ng g^?1) and chicken liver (5.02 ng g^?1). The highest PFOS levels were found in horse mackerel (52.43 ng g^?1), pike-perch (45.87 ng g^?1), sardine (42.83 ng g^?1) and black cod (41.33 ng g^?1). Fish was found to be major source of the PFOS intake, while meat and offal were found to be major sources of the PFOA intake.     

Application of Solid Sampling Device for Direct Determination of Chromium and Nickel in Lubricating Oils by Graphite Furnace Atomic Absorption Spectrometry

Abstract

One method using a solid sampling device for the direct determination of Cr and Ni in fresh and used lubricating oils by graphite furnace atomic absorption spectrometry are proposed. The high organic content in the samples was minimized using a digestion step at 400°C in combination with an oxidant mixture 1.0% (v v^?1) HNO₃ + 15% (v v^?1) H₂O₂ + 0.1% (m v^?1) Triton X-100 for the in situ digestion. The 3-field mode Zeeman-effect allowed the spectrometer calibration up to 5 ng of Cr and Ni. The quantification limits were 0.86 µg g^?1 for Cr and 0.82 µg g^?1 for Ni, respectively. The analysis of reference materials showed no statistically significant difference between the recommended values and those obtained by the proposed methods.     

Monoclonal antibody-based enzyme-linked immunosorbent assay for detection of total malachite green and crystal violet residues in fishery products

A rapid easy-to-use trace level direct competitive enzyme-linked immunosorbent assay (dc-ELISA) detection of total residual malachite green (MG), crystal violet (CV) and their corresponding primary metabolites leucomalachite green (LMG) and leucocrystal violet (LCV) in fishery products in a single assay was developed. The monoclonal antibodies, anti-MG and anti-CV mAbs, were prepared using carboxyl-malachite green (CMG) and cationized bovine serum albumin (cBSA) conjugates as immunogen. The linear range for the quantitative detection of total MG, CV and their primary metabolites LMG and LCV was between 0.15 to 4.5?ng?mL^?1 with a half maximal inhibitory concentration (IC₅₀) at 0.56?±?0.04?ng?mL^?1 (n?=?5). The anti-MG mAbs exhibited 98% cross-reactivity to CV, less than 0.1% cross-reactivity with LMG and LCV, and no cross-reactivity with chloramphenicol, enrofloxacin, sulfadiazine, and tetracycline. Application of the dc-ELISA in fish tissue samples gave a limit of detection (LOD) of 0.37?ng?g^?1. The improved total detection lead to a recovery of 74.60?±?8.38% at 0.5?ng?g^?1 and 87.47?±?12.83% at 2.0?ng?g^?1 that was better than existing techniques. The dc-ELISA showed total MG in 7 out of 44 field fish samples that were confirmed with LC-MS/MS. The easy-to-use, inexpensive, and rapid dc-ELISA for the detection of total MG, CV and their corresponding primary metabolites holds promise for field applications.     

Rapid extraction and sample clean-up for the fluorescence densitometric determination of aflatoxin M1 in milk and mil powder

The diluted sample is passed through a SepPak C18 cartridge and the toxin is eluted with acetonitrile/water (3:7, v/v). The extract is cleaned up on a SepPak silica cartridge. The antidiagonal spot application technique is used for two-dimensional thin-layer chromatography. Spots are quantified by fluorescence densitometry. Recoveries of aflatoxin M1 added in the range 0.03-0.1 ng g^?1 of milk are 86–97%. The detection limit is about 0.005 ng g^?1 for milk and 0.05 ng g^?1 for milk powder.     

Hydrogen and Methane Production, Energy Recovery, and Organic Matter Removal from Effluents in a Two-Stage Fermentative Process

This study evaluates the potential for using different effluents for simultaneous H₂ and CH₄ production in a two-stage batch fermentation process with mixed microflora. An appreciable amount of H₂ was produced from parboiled rice wastewater (23.9?mL g^?1 chemical oxygen demand [COD]) and vinasse (20.8?mL g^?1 COD), while other effluents supported CH₄ generation. The amount of CH₄ produced was minimum for sewage (46.3?mL g^?1 COD), followed by parboiled rice wastewater (115.5?mL g^?1 COD) and glycerol (180.1?mL g^?1 COD). The maximum amount of CH₄ was observed for vinasse (255.4?mL g^?1 COD). The total energy recovery from vinasse (10.4?kJ g^?1 COD) corresponded to the maximum COD reduction (74.7?%), followed by glycerol (70.38?%, 7.20?kJ g^?1 COD), parboiled rice wastewater (63.91?%, 4.92?kJ g^?1 COD), and sewage (51.11?%, 1.85?kJ g^?1 COD). The relatively high performance of vinasse in such comparisons could be attributed to the elevated concentrations of macronutrients contained in raw vinasse. The observations are based on kinetic parameters of H₂ and CH₄ production and global energy recovery of the process. These observations collectively suggest that organic-rich effluents can be deployed for energy recovery with sequential generation of H₂ and CH₄.     

Determination of synthetic musks in the sediment of the Taihu lake by using accelerated solvent extraction (ASE) and GC/MS

Synthetic musks, substitutes for natural musks, are widely distributed in environment. They have been detected in water, sludge, fish, shrimp, mussels and other aquatic animals, and even in human's adipose tissue, blood and breast milk. In this study, a new extraction procedure, based on the accelerated solvent extraction (ASE) and in cell clean-up technique was developed and successfully coupled with gas chromatography-mass spectrometry (GC/MS) for the analysis of musks in sediment samples. With this method, the limits of detection as low as 0.03–0.05?ng?g^?1 and the recovery rate of 86.0%–104% are achieved. When compared with soxhlet extraction (SE) and ultrasonic extraction (USE), ASE not only has the best extraction efficiency but also has advantage in extraction time and solvent consumption. Eight synthetic musks, including six polycyclic musks (Tonalide (AHTN), Galaxolide (HHCB), Phantolide (AHDI), Traseolide (ATII), Cashmeran (DPMI) and Celestolide (ADBI)) and two nitro musks (musk xylene (MX) and musk ketone (MK)), were evaluated in sediment samples collected from 15 selected locations of the Taihu lake, one of the largest freshwater lakes in China. The contents of synthetic musks in sediment samples range from 0.336 to 3.10?ng?g^?1 for HHCB, 0.184 to 1.21?ng?g^?1 for AHTN, below detection limit (BDL) to 0.349?ng?g^?1 for MX, and BDL to 0.0786?ng?g^?1 for MK. The contents of DPMI, ADBI, AHMI and ATII are below detection limit in all samples. The results reflect current status of fragrance compound pollution in this area, and provide basic data for environmental policy making.