Simultaneous multi-channel hydride generation atomic fluorescence spectrometry determination of arsenic,bismuth, tellurium and selenium in tea leaves

A novel, rapid and sensitive method for the simultaneous multi-channel hydride generation atomic fluorescence spectrometry (HG-AFS) determination of total arsenic (As), total bismuth (Bi), total tellurium (Te) and total selenium (Se) in tea leaves was proposed. The operating parameters of self-made multi-channel HG-AFS were optimised, including negative high voltage of photo multiplier tube (PMT), the flow rates of carrier and shield gas, observation height and lamp currents. The conditions of hydride generation for As, Bi, Te and Se were studied in details. Under optimal conditions, the method detection limits (MDL) for As, Bi, Te and Se in tea leaves were 0.0152 μg g⁻¹, 0.0080 μg g⁻¹, 0.0022 μg g⁻¹ and 0.0068 μg g⁻¹, respectively. The proposed method was successfully applied to the simultaneous determination of As, Bi, Te and Se in various tea leaves and the spike recoveries were in the range of 90–103%. The accuracy of method was validated by analysing a tea certified reference material. The obtained values were consistent with the certified ones.     

Validation of antibiotics in catfish by on-line solid phase extraction coupled to liquid chromatography tandem mass spectrometry

For the first time automated on-line solid phase extraction coupled to liquid chromatography tandem mass spectrometry was developed for the simultaneous determination of 13 antibiotics (sulfonamides and tetracyclines) in catfish. The method proposed was validated according to Commission Decision 2002/657/EC, showing good linearity between 2 and 350 μg kg⁻¹, high recovery (80–99%) and reproducibility (13–20%) values, lower detection limits than 0.1 μg kg⁻¹, and quantification limits under 2.4 μg kg⁻¹ (between 39 and 84 times lower than the MRL fixed by the EU). Moreover, the proposed method was also used to determine sulfonamides and tetracyclines in 16 out of 107 samples, all previously analysed by microbiological screening that gave positive results. Five out of 13 antibiotics were found, having tetracycline the higher occurrence (10 samples); in all cases the concentrations were lower than the MRL established.     

Determination of patulin in fruit juices using HPLC-DAD and GC-MSD techniques

A high performance liquid chromatography with a diode-array detector (HPLC-DAD) and a gas chromatography with a mass spectrometer (GC-MSD) are described for the determination of patulin (PAT) in apple juice. The limits of detection (DL) and quantification (QL) for the HPLC-DAD and GC-MSD method were found to be (DL = 0.23 μg kg⁻¹ QL = 1.2 μg kg⁻¹) and (DL = 5.8 μg kg⁻¹ and QL = 13.8 μg kg⁻¹), respectively. The recovery factors for HPLC-DAD and GC-MSD were found to be 99.5% (RSD% = 0.73) and 41% (RSD% = 10.03), respectively. The HPLC-DAD method was used to determine the occurrence of PAT in 90 samples of fruit juices.     

Trace element levels in honeys from different regions of Turkey

A survey of 25 honey samples from different botanical origin, collected all over the Turkey was conducted to assess their trace element contents. The aim of this study was to determine the levels of cadmium (Cd), lead (Pb), iron (Fe), manganese (Mn), copper (Cu), nickel (Ni), chromium (Cr), zinc (Zn), aluminium (Al) and selenium (Se) in honey samples from different regions of Turkey. Trace element contents were determined by a flame and graphite furnace atomic absorption spectrometry technique after dry-ashing, microwave digestion and wet-digestion. The accuracy of the method was corrected by the standard reference material, NIST-SRM 1515 Apple leaves. The contents of trace elements in honey samples were in the range of 0.23–2.41 μg g⁻¹, 0.32–4.56 μg g⁻¹, 1.1–12.7 μg g⁻¹, 1.8–10.2 μg g⁻¹, 8.4–105.8 μg kg⁻¹, 2.6–29.9 μg kg⁻¹, 2.4–37.9 μg kg⁻¹, 0.9–17.9 μg kg⁻¹, 83–325 μg kg⁻¹ and 38–113 μg kg⁻¹ for Cu, Mn, Zn, Fe, Pb, Ni, Cr, Cd, Al and Se, respectively. Iron was the most abundant element while cadmium was the lowest element in the Turkish honeys surveyed. The results showed that trace element concentrations in the honeys from different regions were generally correlated with the degree of trace element contamination of the environment.     

Simplified pesticide multiresidues analysis in fish by low-temperature cleanup and solid-phase extraction coupled with gas chromatography/mass spectrometry

A simple and fast method for the simultaneous analysis of thiobencarb, deltamethrin and 19 organochlorine pesticide residues in fish by gas chromatography–mass spectrometry was investigated in this study. Samples are extracted with acetonitrile. Most of lipids in the extract are eliminated by low-temperature cleanup, prior to solid-phase extraction cleanup. The lipids extracted from the fish samples were easily removed without any significant losses of the pesticides. Aminopropyl (NH₂) cartridge was effective to eliminate the remaining interference. Spiked experiments were carried out to determine the recovery, precision and limits of detection (LODs) of the method. The method detection limits ranged from 0.5 μg kg⁻¹ to 20 μg kg⁻¹, whilst recoveries of the pesticides were in the range of 81.3–113.7% with relative standard deviations ?13.5% at a spiked concentration of 0.05 mg kg⁻¹, 0.02 mg kg⁻¹ and 0.1 mg kg⁻¹. The newly developed method is demonstrated to give efficient recoveries and LODs for detecting pesticide multiresidues in fish.     

A novel method for pesticide analysis in refined sugar samples using a gas chromatography–mass spectrometer (GC–MS/MS) and simple solvent extraction method

A sensitive method for the quantification of 11 pesticides in sugar samples to the μg kg⁻¹ level has been developed. These pesticides are often used in an agricultural context. A simple solvent extraction followed by selective analysis using a gas chromatography–mass spectrometric method was used. This method was accurate (?99%) as it possesses limits of detection in the 0.1-μg kg⁻¹ range, and the coefficients of variations are less than 15% at the low μg kg⁻¹ end of the method’s linear range. The percent recovery of all the pesticides at the lowest levels of detection ranges from 82% to 104%. This method was used for the quantification of pesticides in sugar samples collected from different factory outlets from different parts of India. In this study, 27 refined sugar samples were analysed in which one sample showed a detectable level of the chlorpyrifos pesticide. This study showed that Indian sugar is free from the commonly-used pesticides at the low μg kg⁻¹ levels.     

Quantification of organophosphate insecticides and herbicides in vegetable samples using the “Quick Easy Cheap Effective Rugged and Safe” (QuEChERS) method and a high-performance liquid chromatography-electrospray ionisation-mass spectrometry (LC-MS/MS) technique

A Quick Easy Cheap Effective Rugged and Safe (QuEchERS) extraction was developed and followed by selective analysis using a liquid chromatography-mass spectrometry method for the quantification of eighteen pesticides in vegetable samples. This method was accurate (?99.5%), and it exhibited limits of detection and quantification values in the 0.006-0.091 and 0.020-0.314 μg kg⁻¹ ranges, respectively. Furthermore, the coefficients of variations (?0.9999) were less than 1% at the low μg kg⁻¹ end of the method. Mean recoveries ranged between 94% and 102%, and relative standard deviations were below 10%. Based on these results, the methodology was proven to be highly efficient, robust, and suitable for monitoring the maximum residue limits (MRL) compliance of a wide range of commodity/pesticide combination. This method was successfully applied to the analysis of vegetable samples that were collected from different government farmers’ markets and street shops in urban areas. The presence of target pesticides was found in the range of 0.016 and 50.85 μg kg⁻¹.     

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 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.     

Multiresidue method for analysis of pesticides in pepper and tomato by gas chromatography with nitrogen–phosphorus detection

An analytical multiresidue method for the simultaneous determination of various classes of pesticides in vegetables (pepper and tomato) was developed. Vegetable samples are extracted with acetone and the pesticides are partitioned into ethyl acetate/cyclohexane. Final determination was made by gas chromatography with nitrogen–phosphorus detection. Confirmation analysis of pesticides was carried out by gas chromatography coupled with mass spectrometry in the selected ion monitoring (SIM) mode. The identification of compounds was based on retention time and on comparison of the primary and secondary ions. Recovery studies were performed at 0.05, 0.1 and 0.02 mg kg⁻¹ fortification levels of each compound and the recoveries obtained ranged from 70.1% to 128.5% with relative standard deviations lower than 7%. The method showed good linearity over the range assayed 50–1500 μg l⁻¹ and the detection and quantification limits for the pesticides studied varied from 0.1 to 4.4 μg kg⁻¹ and 0.4 to 14.5 μg kg⁻¹, respectively. The proposed method was used to determine pesticides levels in peppers and tomatoes grown in experimental greenhouses.     

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.     

Effects of skin and grilling method on formation of heterocyclic amines in chicken pectoralis superficialis muscle

Mutagenic heterocyclic amines (HAs) originate in processed proteinaceous foods. The effects of the presence of skin (with vs. without) and of grilling method (two plate vs. infrared) on the content of HAs in grilled chicken pectoralis superficialis muscle (temperature, 220 °C) were investigated. HA precursors (creatine, creatinine, free amino acids and carbohydrates) and HAs of these raw and grilled breast muscles were determined. The muscles originated from 24 birds of either sex (provenance Ross; aged 40-45 days). The HA content was determined in homogenates of the upper and lower surface slices of the grilled muscles (T_i = 82 °C). A higher content of total free amino acids was seen for the muscle (27.1 mmol kg⁻¹ raw meat) than for the skin (21.7 mmol kg⁻¹ raw meat). The creatine, creatinine and carbohydrate levels in the skin were below the limits of detection. The contents of creatine (31.8-38.7 mmol kg⁻¹) and creatinine (0.24-0.33 mmol kg⁻¹) in the breast muscle were determined. Relatively high levels were seen for glucose (23 mmol kg⁻¹ raw meat) and fructose (10 mmol kg⁻¹ raw meat) in the muscle, with other sugars present at low levels (<2 mmol kg⁻¹ raw meat). For the chicken muscle grilled on a two-plate grill, the contents of total HAs (PhIP, MeIQx, DiMeIQx, Harman and Norharman) were lower with the skin in place than in the muscle grilled without the skin (3.5 μg kg⁻¹vs. 4.8 μg kg⁻¹). Also, during infrared grilling with the skin, lower amounts of HAs were formed than with grilling on the two-plate grill (2.4 μg kg⁻¹vs. 3.5 μg kg⁻¹). On average, the infrared-grilled samples with skin contained 3-fold more total HAs than similar samples without the skin (2.4 μg kg⁻¹vs. 0.8 μg kg⁻¹), with the highest levels seen for PhIP and MeIQx.     

Speciation of organic and inorganic selenium in selenium-enriched rice by graphite furnace atomic absorption spectrometry after cloud point extraction

A new method was developed for the determination of organic and inorganic selenium in selenium-enriched rice by graphite furnace atomic absorption spectrometry detection after cloud point extraction. Effective separation of organic and inorganic selenium in selenium-enriched rice was achieved by sequentially extracting with water and cyclohexane. Under the optimised conditions, the limit of detection (LOD) was 0.08 μg L⁻¹, the relative standard deviation (RSD) was 2.1% (c = 10.0 μg L⁻¹, n = 11), and the enrichment factor for selenium was 82. Recoveries of inorganic selenium in the selenium-enriched rice samples were between 90.3% and 106.0%. The proposed method was successfully applied for the determination of organic and inorganic selenium as well as total selenium in selenium-enriched rice.     

Determination of trace elements in Croatian floral honey originating from different regions

The concentrations of As, Cd, Cu, Hg and Pb were determined in 54 multi-floral honey samples collected from five regions of Croatia during 2009 and 2010. Element contents decreased in the following order: Cu > Pb > As > Hg > Cd. Significant differences in lead and copper levels were observed between regions. Mean levels of elements (μg kg⁻¹) in all honey samples measured were: 19.7 for As, 1.51 for Cd, 1074 for Cu, 2.72 for Hg and 65.2 for Pb. Copper and lead were the most abundant elements in the Centre region, with range and mean contents of 108–41,271 and 3232 μg kg⁻¹ and 22.0–440 and 131 μg kg⁻¹, respectively. The highest element contents were: As 23.8 μg kg⁻¹ in the South region, Cd 2.11 μg kg⁻¹ in the Southwest region and Hg 2.63 μg kg⁻¹ in the Northeast region. The finding that lead contents in Croatian honey were higher than most reported lead levels in honey from other European countries is of particular concern. These indicate that attention must be focused on setting positions for honey production hives in areas distant from highways and railways.     

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.     

Supramolecular solvent-based microextraction of Sudan dyes in chilli-containing foodstuffs prior to their liquid chromatography-photodiode array determination

A supramolecular solvent made up of reverse micelles of decanoic acid was proposed for the simple and rapid extraction of Sudan I, II, III and IV from chilli-containing foodstuffs. The procedure involved the extraction of minute quantities (0.5–1 g) of homogenised food sample with an aqueous solution containing 10% THF and 200 mg of decanoic acid, conditions under which the supramolecular solvent (around 330 μL) formed in situ and instantaneously. The overall sample treatment took about 30 min and several samples could be simultaneously treated using conventional lab equipment. No clean-up or solvent evaporation were required before determination of Sudan dyes by liquid chromatography and photometric detection. Extractions were independent of salt addition (up to 1 M), the temperature (up to 60 °C) and the pH (below 4) rendering the method robust. The detection limits of the method were 4.2, 2.7, 6.5 and 7.4 μg kg⁻¹ for Sudan I, II, III and IV, respectively. Recoveries obtained by applying this approach to the analysis of six chilli-containing sauces fortified with Sudan dyes at the μg kg⁻¹ level were in the interval 86–108% with relative standard deviations between 2% and 7%.     

Determination of tetracyclines in multi-specie animal tissues by pressurized liquid extraction and liquid chromatography–tandem mass spectrometry

A specific, sensitive and robust pressurized liquid extraction (PLE) and liquid chromatography tandem mass spectrometry (LC–MS/MS) method for determining tetracycline, chlortetracycline, oxytetracycline and doxycycline in bovine, swine, poultry and lamb muscle tissues is presented. PLE was performed using an ASE^® 200 from Dionex and water as extractant, followed by solid-phase extraction (SPE) using an Oasis HLB cartridge. The method was validated for beef, chicken, pork and lamb meat in compliance with the requirements set by Commission Decision, 2002/657/EC [Commission Decision 2002/657/EC (2002). Implementing Council Directive 96/23/EC concerning the performance of analytical methods and interpretation of results. Official Journal of European Communities, L239, 66–98. (Available at: <http://europe.eu.int>)]. The average recoveries of the different meat samples, spiked with the four tetracyclines at three levels (1, 100 and 200 μg kg⁻¹ of each tetracycline), were always higher than 89% with intraday and interday precision lower than 15% and 17%, respectively. A good linearity was established for the four tetracyclines in the range from 5 to 10,000 μg kg⁻¹ with r > 0.995. The limits of quantification (LOQs) were between 0.5 and 1 μg kg⁻¹, which are well below the tolerance levels set by the European Union. The decision limit (CCα) and the decision capability (CCβ) were in the range 101–116 and 112–130 μg kg⁻¹, respectively. Compared with previous methods, sample preparation time required for the analysis and LOQs, are reduced. The method demonstrated its successful application for the analysis of 100 meat samples. Two samples of beef and one sample of chicken out of 25 of each type tested positive while none of 25 samples of either, lamb or pork, tested positive.     

Analysis of multi-pesticide residues in the foods of animal origin by GC–MS coupled with accelerated solvent extraction and gel permeation chromatography cleanup

A new analytical method was developed to simultaneously determine residues of 109 pesticides (including isomers) in the foods of animal origin. Acetonitrile was selected for accelerated solvent extraction (ASE) for effectively extracting the pesticides from the fatty samples. The cleanup was performed with an automated gel permeation chromatography (GPC) cleanup system. The prepared samples were analysed with GC–MS in the selected ion monitoring mode (SIM) using one target and two qualitative ions for each analyte. Chlorpyrifos-d₁₀ was used as an internal standard. The lowest limit of detection was 0.3 μg kg⁻¹ for some pesticides. The recoveries and relative standard deviations (RSDs) were checked by spiking untreated samples with pesticides at 0.05, 0.1 and 0.2 mg kg⁻¹. The average recoveries of most pesticides were from 62.6% to 107.8%. The precision values expressed as RSD were all ?20.5% (n = 6). Good linearity (r ? 0.99) was observed between 0.05 and 1.5 μg mL⁻¹.     

Analyses of selected non-authorized insecticides in peppers by gas chromatography/mass spectrometry and gas chromatography/tandem mass spectrometry

Two methods based on gas chromatography coupled with mass spectrometry and tandem mass spectrometry analyzers are described for the identification, confirmation and quantitation of two EU-banned insecticides: isocarbophos and isofenphos-methyl, detected in recent monitoring programmes in pepper samples. The proposed methodologies involved a liquid–liquid extraction with acetonitrile followed by a cleanup step by dispersive solid-phase extraction using primary–secondary amine as sorbent material. Recovery studies performed on peppers spiked at different fortification levels (10 and 50 μg kg⁻¹) yielded average recoveries in the range 85–98% with RSD values below 8%. Identification, confirmation and quantitation were carried out by gas chromatography/mass spectrometry (GC–MS) in selected ion monitoring mode and gas chromatography/tandem mass spectrometry (GC–MS/MS) using an ion trap operating in the multiple reaction monitoring (MRM) mode. The obtained limits of detection (LODs) were in the range 0.1–0.3 μg kg⁻¹, depending on the technique. The proposed methods were successfully applied to the analysis of suspected pepper samples.     

Fish and food safety: Determination of formaldehyde in 12 fish species by SPME extraction and GC–MS analysis

The formaldehyde (FA) content in different fish products was evaluated using a solid phase microextraction (SPME)-GC–MS method based on fiber derivatisation with pentafluorobenzyl-hydroxyl-amine hydrochloride. LOD and LOQ values of 17 and 28 μg kg⁻¹, respectively were calculated. Fish quality was assessed by the analysis of 12 species (sea-fish, freshwater-fish and crustaceans), revealing variable FA levels. Fresh, deep frozen, canned, boiled and roasted fish were analysed; cooking always produced a decrease in the analyte content. Fish belonging to the Gadidae family were the samples with the highest FA concentration (from 6.4 ± 1.2 mg kg⁻¹ to 293 ± 26 mg kg⁻¹), in four cases out of 14 exceeding the value of 60 mg kg⁻¹ proposed by the Italian Ministry of Health. Storage on ice was also investigated, showing moderate FA production also at temperature around 0 °C. FA contents lower than 22 mg kg⁻¹ were finally found in all the other samples.