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.     

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.     

Direct analysis of honey for the total content of Zn and its fractionation forms by means of flame atomic absorption spectrometry with solid phase extraction and ultrafiltration approaches

A method of direct analysis of honey by air–acetylene flame atomic absorption spectrometry for reliable determining of the total content of Zn was evaluated and compared with measurements completed after open vessel wet oxidative digestion of honeys with a mixture of HNO₃ and H₂O₂. Applying the proposed method, the concentration of Zn in 13 raw light to dark colour honeys was found to be within 0.26–2.61 μg g⁻¹. Additionally, solutions of selected honeys were subjected to functional speciation analysis using a two-column solid phase extraction with a non-ionic, apolar adsorbing resin Amberlite XAD-16 and a strongly acidic cation exchanger Dowex 50W-x8-200. Another set of solutions was subjected to physical fractionation using filtration with membranes of 0.45 μm pore size and molecular weight cut-off size of 100, 50, 30, 10 and 5 kDa. Both approaches used to partitioning of Zn enabled retrieving information on the fraction of total Zn that is predominant class of species (59–89%) and, regarding its positive charge and very low molecular size, seems to be the most available from honey and absorbable in digestion.     

Gas chromatographic–mass spectrometric characterisation of tri- and tetrasaccharides in honey

A GC–MS method has been used to characterize tri- and tetrasaccharides in honey after their derivatization into trimethylsilyloxime derivatives. Based on retention data and mass spectra, a total of 25 trisaccharides were characterized; 12 being unequivocally identified using standards and two of them detected for the first time in honey. Erlose and panose were the major trisaccharides in the 12 honeys under analysis, their concentrations ranging 30–1214 mg 100 g⁻¹ of honey and 17–863 mg 100 g⁻¹ of honey, respectively. The GC–MS method also allowed the analysis of tetrasaccharides. Besides nystose, another nine tetrasaccharides were characterized; six of them were sucrose derivatives. Tetrasaccharides were present in concentrations lower than 230 mg 100 g⁻¹ of honey.     

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.     

Solid phase extraction with flame atomic absorption spectrometry for determination of traces of Ca,K, Mg and Na in quality control of white sugar

A fast and straightforward pre-concentration procedure based on solid phase extraction with a strongly acidic cation-exchanger Dowex 50 W × 8–400 was proposed to determine traces of Ca, K, Mg and Na in white sugar samples by means of flame atomic absorption spectrometry. For this purpose, 20% (m/v) white sugar solutions (100 ml) were driven through resin beds at 10 ml min⁻¹ to retain Ca, K, Mg and Na ions and to separate sucrose that passed through unretained. Thereafter, columns were rinsed with water and elements of interest were recovered prior to measurements using 5 ml of a 2 mol l⁻¹ HCl solution. Detection limits of 0.04, 0.05, 0.02 and 0.01 μg g⁻¹ for Ca, K, Mg and Na, respectively, and precision of measurements within 1–3% were achieved. The proposed method enabled to determine Ca, K, Mg and Na in samples of white sugar within corresponding ranges: 0.66–0.99 μg g⁻¹ (Ca), 2.9–12.2 μg g⁻¹ (K), 0.53–1.57 μg g⁻¹ (Mg) and 0.06–0.30 μg g⁻¹ (Na). Accuracy of this sample pre-treatment procedure and analysis method was assessed by performing spikes and recovery experiments. Recoveries of added Ca, K, Mg and Na were found to be within 97–102%, demonstrating good reliability of results.     

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.     

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.     

Analysis of potential adulteration in herbal medicines and dietary supplements for the weight control by capillary electrophoresis

Four different phytopharmaceutical dosage forms for use in weight control programs were analyzed. Two different ground herbal blends and their correspondent infusions, a capsule and a tincture were investigated for the presence of compounds used as adulterants in these products. A capillary electrophoresis (CE) method was developed and validated. The optimized experimental conditions were: BGE, sodium tetraborate buffer 20 mM, pH 9.2, voltage applied 30 kV, capillary temperature 25 °C, injection sample at 0.5 Psi during 5 s. Ephedrine, norephedrine, caffeine and furosemide were baseline separated in less than 7 min; the migration times were found to be 2.65, 2.90, 3.75 and 6.58 min, respectively. The analysis showed in sample 3 concentrations of 0.45 ± 0.03 mg g⁻¹ (ephedrine), 0.33 ± 0.02 mg g⁻¹ (norephedrine), 1.09 ± 0.41 mg g⁻¹ (caffeine) and 0.80 ± 0.17 mg g⁻¹ (furosemide). Caffeine content in samples 1, 2 and 4 was 0.61 ± 0.06 mg g⁻¹, 15.66 ± 1.05 mg g⁻¹ and 2.27 ± 0.13 mg ml⁻¹, respectively. Linearity was obtained in the concentration range of 1–1000 μg ml⁻¹. Limits of detection (LOD) and quantification (LOQ) were determined as 0.42 μg ml⁻¹ and 1.40 μg ml⁻¹ (ephedrine), 0.47 μg ml⁻¹ and 1.40 μg ml⁻¹ (norephedrine), 0.12 μg ml⁻¹ and 0.48 μg ml⁻¹ (caffeine), 0.22 μg ml⁻¹ and 0.73 μg ml⁻¹ (furosemide).     

Comparison of the cell wall composition for flesh and skin from five different plums

Cell walls were isolated from flesh and skin of five plum varieties corresponding to three species (Prunus domestica L., Prunus salicina Lindl. and Prunus insititia Lindl.) using the alcohol-insoluble solids (AIS) procedure. Yields varied from 83 to 114 g kg⁻¹ dry weight in the flesh and from 192 to 361 g kg⁻¹ dry weight in the skins. Their main sugars were uronic acid (224–322 mg g⁻¹ AIS), cellulosic glucose (139–170 mg g⁻¹ AIS), galactose and arabinose. Galactose and arabinose ratio were variable between the varieties. The degrees of methylation were high (62–84).     

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 ultratrace levels of selenium in fruit and vegetable samples grown and consumed in Portugal

The selenium content in fruit and vegetable samples from two regions in Portugal were analysed using hydride generation atomic fluorescence spectrometry (HG-AFS) and radiochemical nuclear activation analysis (RNAA) – two analytical methods with very low limits of detection. The lower detection limits of HG-AFS, 3 μg kg⁻¹ and 8 μg kg⁻¹ (according to conditions used for digestion), and for RNAA, 10 μg kg⁻¹, meant that it was possible to determine selenium in samples previously analysed using the replicate sample instrumental nuclear activation analysis (RSINAA) with a higher detection limit associated.     

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.     

Analysis of some selected catechins and caffeine in green tea by high performance liquid chromatography

Green tea seems to have a positive impact on health due to the catechins-found as flavanols. Thus, the present study was aimed to develop a low cost reversed phase high performance liquid chromatographic (HPLC) method for simultaneous determination of flavanol contents, namely catechin (C), epicatechin (EC), epigallocatechin (EGC), epicatechin 3-gallate (ECG) and epigallocatechin 3-gallate (EGCG) and caffeine in 29 commercial green tea samples available in a Saudi Arabian local market. A C-18 reversed-phase column, acetonitrile–trifluoroacetic acid as a mobile phase, coupled with UV detector at 205 nm, was successfully used for precise analysis of the tested analytes in boiled water of digested tea leaves. The average values of N (No. of theoretical plates), HETP (height equivalent of theoretical plates) and R_s (separation factor) (at 10 μg ml⁻¹ of the catechins EC, EGC, EGCG and ECG) were 2.6 × 10³ ± 1.2 × 10³, 1.7 × 10⁻³ ± 4.7 × 10⁻⁴ cm and 1.7 ± 5.53 × 10⁻², respectively. The developed HPLC method demonstrated excellent performance, with low limits of detection (LOD) and quantification (LOQ) of the tested catechins of 0.004–0.05 μg ml⁻¹ and 0.01–0.17 μg ml⁻¹, respectively, and recovery percentages of 96–101%. The influence of infusion time (5–30 min) and temperature on the content of the flavanols was investigated by HPLC. After a 5 min infusion of the tea leaves, the average concentrations of caffeine, catechin, EC, EGC, ECG and EGCG were found to be in the ranges 0.086–2.23, 0.113–2.94, 0.58–10.22, 0.19–24.9, 0.22–13.9 and 1.01–43.3 mg g⁻¹, respectively. The contents of caffeine and catechins followed the sequence: EGCG > EGC > ECG > EC > C > caffeine. The method was applied satisfactorily for the analysis of (+)-catechin, even at trace and ultra trace concentrations of catechins. The method was rapid, accurate, reproducible and ideal for routine analysis.     

Determination of selenium in selected food samples from Argentina and estimation of their contribution to the Se dietary intake

An optimised FI-HGAAS method was applied to determine the total selenium concentrations in selected high consumption food (fish, beef, chicken, milk, rice, wheat flour, egg) and to estimate their contribution to the Argentinean dietary intake, whose information is scarce nowadays. Through several optimisation steps a suitable method was achieved showing satisfactory figures of merit for all matrices. Average recovery was 96%, RSD < 5%, LODs ranged 2.0–7.0 μg kg⁻¹ and the accuracy was assessed using DOLT-3 NRC certified reference material. Meat and eggs showed the highest values (in μg kg⁻¹, beef: 42–153; chicken: 62–205; fish: 94–314; canned tuna: 272–282; eggs: 134–217), minor values were found for wheat flour (22–42), rice: (<22), pasta (47–64) and milk (<7–9). An estimated intake of 32 and 24 μg day⁻¹ for adult men and women, respectively, suggested a deficient Se intake, leading to further comprehensive surveys of Se occurrence in Argentina.     

A validated matrix solid-phase dispersion method for the extraction of organophosphorus pesticides from bovine samples

A method based on matrix solid-phase dispersion (MSPD) was developed for the quantitative extraction of five organophosphorus (OPPs) pesticides from bovine samples. The determination was carried out by high performance liquid chromatography (HPLC) with diode array spectrophotometric UV detection. The MSPD extraction with octadecylsilyl (C18) sorbent combined with a silica gel clean-up and acetonitrile elution was optimised for chlorpyrifos, chlorfenvinphos, diazinon, fenitrothion, and parathion-methyl. The method was validated, yielding recovery values higher than 94%, except for chlorfenvinphos in liver (55%), and precision values, expressed as relative standard deviations (RSDs), which were less than or equal to 15% in liver and 11.5% in muscle at spiking levels of 0.25, 2.5 and 5 μg g⁻¹. Linearity was studied from 0.5 to 15 μg g⁻¹, and the limits of detection (LODs) were found to be lower than 0.1 μg g⁻¹_. This method was applied to the analysis of real samples with confirmative analyses performed using gas chromatography–mass spectrometry (GC–MS) in selected ion monitoring mode (SIM).     

Composition of oregano essential oil (Origanum vulgare) as affected by drying method

The influence of the drying method on volatile compounds of Origanum vulgare was evaluated. The drying methods tested were convective (CD) at 60 °C and vacuum-microwave (VMD), as well as a combination of convective pre-drying and VM finish-drying (CPD–VMFD). The volatile compounds of fresh and dried oregano were extracted by steam-hydrodistillation and analyzed by GC–MS. Oregano drying kinetics was described by a simple exponential model for CD and CPD–VMFD, while VMD kinetics consisted of two periods: linear until a critical point and exponential beyond that point. Thirty-four compounds were tentatively identified, with carvacrol, thymol, and γ-terpinene, being the major components. The total volatiles concentration of fresh oregano (33.0 g kg⁻¹) decreased significantly during drying, independently of the method used (CD: 10.2 g kg⁻¹, CPD–VMFD: 13.1 g kg⁻¹, and VMD: 27.9 g kg⁻¹). The final conclusion was that VM dehydrated Polish oregano was of better aromatic quality than that dried using hot air.     

Comparison of isoflavones composition in seed,embryo, cotyledon and seed coat of cooked-with-rice and vegetable soybean (Glycine max L.) varieties

In order to study the content and composition of isoflavones retained in soybean seed component, obtained each component part the embryo, cotyledon and seed coat tissues of nine different soybean varieties were analyzed for 12 isoflavones using high performance liquid chromatography with photo diode array detector (HPLC-PDA) and were compared to each other. A total average concentration of isoflavone was 2887 μg g⁻¹ in embryo, 575 μg g⁻¹ in whole seed, 325 μg g⁻¹ in cotyledon, and 33 μg g⁻¹ in seed coat. With respect to each tissue of soybean varieties, isoflavone content was highest in Geomjeongkong 2 embryo (5701 μg g⁻¹), Geomjeongolkong whole seed (1321 μg g⁻¹), Heugcheongkong cotyledon (951 μg g⁻¹), and Keunolkong seed coat (56 μg g⁻¹). Isoflavone was least present in Keunolkong embryo (341 μg g⁻¹), Hwaeomputkong whole seed (175 μg g⁻¹), Seonheukkong cotyledon (81 μg g⁻¹), and Seoklyangputkong seed coat (5 μg g⁻¹). Overall, embryo and seed coat of all nine varieties contained isoflavones at the highest and lowest level, respectively. Isoflavones accumulated in the order of malonylglycoside, glycoside, acetylglycoside, and aglycon, among which malonylglycoside was the most abundant form ranging from 66% to 79% of the total isoflavone content in all three tissues. The embryo of cooked-with-rice soybean with black seed coat appears to be the best source of isoflavone.     

Determination of methylmercury in marine and freshwater fish in Ghana using a combined technique of dithizone extraction and gas–liquid chromatography with electron capture detection

Concentrations of methylmercury (MeHg) residues were determined in different marine and freshwater fishes from Ghana. Samples were treated with ethanolic potassium hydroxide in water bath at 100 °C for 1 h. After neutralising with HCl and washing with hexane, MeHg was extracted with dithizone in toluene, cleaned up and determined by gas chromatography with electron capture detection (GC–ECD). The method was sensitive with good precision, detection limit of 0.0005 μg g⁻¹ (0.5 μg kg⁻¹) and provided good separation for organomercury compounds. The validity of the method was established using dogfish muscle certified reference material, DORM-2. The method was applied to different fish species. Concentration of MeHg in the edible muscle tissue of the tested fish ranged from 0.009 to 0.107 μg g⁻¹ wet weight. The concentrations of MeHg in the fish samples obtained do not however, constitute any significant mercury exposure to the general population through consumption of the tested fish species.     

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.