A fast and effective method of quantitative analysis of VB1, VB2 and VB6 in B-vitamins complex tablets based on three-dimensional fluorescence spectra

Scattering signals and partial overlapping of target peaks usually appear in fluorescence determination. In this study, the improved wavelet moment method was proposed and applied to the quantitative determination of multiple target components in real B-vitamins complex tablets based on three-dimensional (3D) fluorescence spectra. The correlation coefficients (R) were more than 0.9939, and the correlation coefficients of leave-one-out cross-validation (R_LOO-cv) were more than 0.9376. The inter-day and intra-day variations were less than 5.8% and 6.1%, respectively. The recovery ranged from 97.6% to 109.4%. The limits of detection (LODs) and quantification (LOQs) were less than 0.07 μg mL⁻¹ and 0.13 μg mL⁻¹, respectively. All the statistical parameters indicated that the method was stable and reliable. The application to the practical samples confirmed that wavelet moment method effectively extracted the features of target components in 3D spectra and the proposed method could be applied to the analyses of food or other complex samples.     

Determination of phytosterols in oenological matrices by liquid chromatography-atmospheric pressure chemical ionization and ion-trap mass spectrometry

The aim of the present study is the identification of plant sterols and the development of an analytical method that allows for the quantification of such family of compounds in oenological matrices. The application of liquid chromatography-atmospheric pressure chemical ionization ion-trap mass spectrometry (LC-APCI-ITMS) to sterol characterization is a useful tool and was selected to perform this research. Sterol separation was achieved using a C8 column with a mobile phase consisting of water and acetonitrile under gradient conditions and column temperature of 35 °C, which leads to analyte elution in less than 25 min. Retention times, precursor ions and MRM transitions of analytes allowed for the identification and sensitive quantitative determination of phytosterols in oenological matrices at trace levels. The method showed a dynamic linear range over the concentration ranges from 0.02 to 320 mg kg⁻¹ for the different parts of grapes and from 8 to 100 ng mL⁻¹ in case of wine. The most abundant phytosterol in all samples was β-sitosterol. The seeds are the richest source of phytosterols having a great amount of β-sitosterol, 314 mg kg⁻¹ fresh berry mass, followed by stigmasterol, fucosterol and campesterol at much lower concentrations (ranging from 3 to 10 mg kg⁻¹).     

Spectrophotometric method for determination of aluminium content in water and beverage samples employing flow-batch sequential injection system

A sensitive, precise and reliable flow-batch method for the determination of aluminium (Al) was developed using a sequential injection-monosegmented flow system incorporating a mixing chamber unit. Eriochrome cyanine R (ECR) was used as a chromogenic reagent in the presence of N,N-dodecyltrimethylammonium bromide (DTAB). The Al-ECR complex at pH 6 gave a maximum absorption at 584 nm. In-line single standard calibration and a standard addition procedure were developed employing the monosegmented flow technique. Under the optimum conditions, a linear calibration graph in the range of 0.0075–0.625 mg L⁻¹ Al was obtained with limits of detection and quantitation of 0.0020 and 0.0070 mg L⁻¹, respectively. Relative standard deviations were 0.8 and 1.3% for 0.010 and 0.025 mg L⁻¹ Al (n = 11), respectively. A sample throughput of 24 h⁻¹ using an in-line standard calibration approach and 6 h⁻¹ using four standard addition levels was achieved. The developed system was successfully applied to water samples and beverage samples. The results agreed well with those obtained from the ICP-AES method. Good recoveries between 85 and 104% were obtained.     

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.     

Determination of clothianidin in food products by using an automated system with photochemically induced fluorescence detection

A flow-through system based on the integration of solid-phase spectroscopic detection implemented with photochemically induced fluorescence (PIF) is proposed for the determination of clothianidin (a non-fluorescent neonicotinoid insecticide) through a multicommutated method. The pesticide is injected into the carrier stream (0.015 mol L⁻¹C₂H₄O₂/NaC₂H₃O₂, pH = 5.0) and flows towards a homemade photoreactor, which consists of a PTFE tubing loosely coiled around a low-pressure mercury lamp (15W). After the photochemical reaction of clothianidin, the generated fluorescent photoproduct is transported to a flow cell packed with Sephadex-SP C-25 where it is retained and monitored (λ_ex = 357 nm/λ_em = 418 nm). The method presents a detection limit of 1.5 ng mL⁻¹, a sample throughput of 23 h⁻¹ and inter-day relative standard deviation lower than 3%. The described system has been satisfactorily applied to the determination of clothianidin in samples of drinking water, rice and honey. Taking into account that the maximum residue limit specified in the Codex Alimentarius Commission for rice grains is 0.5 mg kg⁻¹, recovery experiments have been carried out for clothianidin concentrations in the 0.3-10.0 mg kg⁻¹ range.     

Quantification of 3-deoxyglucosone (3DG) as an aging marker in natural and forced aged wines

The Maillard reaction product 3-deoxyglucosone (3DG) was quantified in wines, by high-performance liquid chromatography-mass spectrometry analysis after derivatization with ortho-phenylenediamine. Both sweet red Port wines and dry white wines were analysed during natural and forced aging. In natural aging, and for dry white wines, 3DG is negatively correlated to age (r = −0.939), while for sweet red Port wines, 3DG is positively correlated to age (r = 0.782). The same tendency was observed during a wine forced aging protocol. For a dry white wine, with higher levels of α-amino acids, 3DG is consumed (k_consumption 0.077–0.098 day⁻¹) along the time protocol, while for a sweet red Port wine, with lower levels of α-amino acids, an accumulation of 3DG is observed with time (k_formation 0.041–0.060 day⁻¹). These results suggest that 3DG content can be used as an aging marker, as it has discriminated dry white and sweet red Port wines from different ages and cultivars. Analysis of wine-model solutions allowed verifying that the fructose content has a higher effect on 3DG formation than glucose, as well as that an increase on amino acids content does not lead to an increase of 3DG yields.     

Assessment of hydroxymethylfurfural and furfural in commercial bakery products

A survey was conducted on the presence of hydroxymethylfurfural (HMF) and furfural in bread and bakery products; for this purpose a reliable extraction procedure followed by high performance liquid chromatography (HPLC) was applied. The performance of the method was evaluated in terms of linearity (r always > 0.99); detection limits (0.001 mg L⁻¹ for furfural and 0.006 mg L⁻¹ for HMF); recovery percentages (98.5–100.5% for HMF and 94.9–98.9% for furfural); intraday precision (<4.65%) and interday precision (<7.51%). Two batches of a wide variety of products commercially available were analysed (a total of 88 samples). HMF and furfural levels presented high variability between products and batches of the same product. Cake/pastry samples showed the lowest HMF content (3.0 mg kg⁻¹ fw) while biscuits showed the highest content (7.8 mg kg⁻¹ fw) (p < 0.05). Regarding furfural, bread samples presented the highest furfural content (5.3 mg kg⁻¹ fw) (p < 0.05), cake/pastry and biscuits showed the lowest content (1.9 and 3.0 mg kg⁻¹ fw, respectively). Chocolate containing samples presented higher amounts of furfural (>20 mg kg⁻¹). These results indicate that special attention should be given to furfural content of bread (due to its daily high consumption) and re-evaluation of dietary exposure.     

A spectrophotometric method for determination of total proteins in cow milk powder samples using the o-nitrophenylfluorone/Mo(VI) complex

A new spectrophotometric method has been developed for the determination of protein in Tween 20 microemulsion medium. The method is based on the interaction between protein and o-nitrophenylfluorone–Mo(VI) complex as a spectral probe. Under the optimal conditions, Beer's Law is obeyed over the range of 0–16 μg mL⁻¹ bovine serum albumin (BSA) with the detection limit being 15 ng mL⁻¹. Both the influence of reaction variables and the interference of coexisting substance are studied. The proposed method has been applied to the whole milk powder samples with satisfactory results. The recoveries are between 97.6% and 105.8%, and the standard relative deviations are less than 4.3%. Molar ratio and slope ratio methods are used to determine the binding number of BSA with the complex and the value 96.     

Application of non-supervised pattern recognition techniques to classify Cabernet Sauvignon wines from the Balkan region based on individual phenolic compounds

Phenolic compounds in sixteen Cabernet Sauvignon wines from different wine-growing sub-regions in the Balkan region were investigated using HPLC with DAD and fluorescence detector and spectroscopic analysis, as well as statistical PC/F and cluster analysis. The HPLC analysis of investigated red wines showed that the content of total hydroxybenzoic acids, detected at 280 nm, was the highest in wines from Tikveš wine-growing subregion, Macedonia (127–140 mg L⁻¹). Total hydroxycinnamic acids, detected at 320 nm, were the highest in wines from Župa wine-growing subregion, Serbia (43–45 mg L⁻¹). The concentration of total flavonoids (flavan-3-ols, flavonols, flavons and flavanon), detected at 280, 360 and 322/275 nm, respectively, was the highest in wine from Katarzyna Estate wine-growing subregion, Bulgaria (167 mg L⁻¹). Finally, the concentration of total anthocyanins, detected at 520 nm, was the highest in wine from Šumadija wine-growing subregion, Serbia (1463 mg L⁻¹). The results of PCA and cluster analysis together confirmed that the content of phenolic compounds in Cabernet Sauvignon wines depends on agro-climatic factors, oenological practice in different wineries and the growing season in the Balkan region that were investigated. The areas in the Balkan region in this study with similar agro-climatic characteristics showed shorter clustering distance, indicating similar phenol profiling in the red wines tested.     

Non-destructive determination of β-carotene content in mango by near-infrared spectroscopy compared with colorimetric measurements

Non-destructive applications for the detection of food quality, especially internal properties, are highly relevant for process control in the food industry. In this respect, colour measurement and near-infrared spectroscopy (NIRS) were evaluated and compared for their ability to predict β-carotene content in mango cv. ‘Nam Dokmai’. Colorimetric analysis of peel and flesh colour as well as NIR measurements in the short- (700–1100 nm) and long-wave regions (1000–2500 nm) were analysed for prediction ability. It was found that β-carotene content could be estimated by multiple linear regression (MLR) models developed from b* and hue angle (h°) values of the flesh with good results for coefficient of determination (R²) and standard errors of cross validation (SECV) of 0.941 and 10.2 retinol equivalents (RE) 100 g⁻¹ edible part (EP), respectively, while peel colour showed poor results. However, flesh colour measurement is a destructive method. NIRS calibration showed good results with R² > 0.800 and standard error of prediction (SEP) 11.642–20.2 RE 100 g⁻¹ EP. Long-wave NIR provided better prediction ability than short-wave. From these results, NIRS can be recommended for non-destructive and reliable determination of β-carotene content in mango. The results have implications for quality control in the industrial handling and processing of fruits.     

An efficient,rapid and microwave-accelerated dispersive liquid–liquid microextraction method for extraction and pre-concentration of some organophosphorus pesticide residues from aqueous samples

In this paper, microwave-accelerated dispersive liquid–liquid microextraction has been developed for the extraction/preconcentration of some organophosphorus pesticides from aqueous samples prior to their analysis by gas chromatography–flame ionization detection. In this method, temperature of a high volume of aqueous sample is elevated by a microwave oven and then a mixture of extraction and disperser solvents is rapidly injected into the aqueous phase. After cooling to room temperature, the phase separation is accelerated by centrifuging. The main experimental factors affecting performance of the method including type and volume of the extraction and disperser solvents, temperature, pH, and salt addition were investigated and optimized. Under the optimum extraction conditions, the method resulted in low limits of detection and quantification within the ranges of 0.65–1.3 and 2.2–4.5 μg L⁻¹, respectively. Relative standard deviations were in the range of 2–7% (C = 40 or 100 μg L⁻¹) for intra-day (n = 6) and inter-day (n = 4) precisions. Finally, the proposed method was successfully applied to analysis of the target analytes in surface water and well water and fruit juice samples; diazinon was determined at μg L⁻¹ level in apple juice.     

The risk of high mercury accumulation in edible mushrooms cultivated on contaminated substrates

Mercury (Hg) exposures represent a significant worldwide health issue. At the same time its content in cultivated mushrooms is not effectively regulated. The present study investigated how substrate contamination with Hg (0.1–0.5 mM) affects its accumulation in stipes and caps of Agaricus bisporus E58, Pleurotus ostreatus H195 and Hericium erinaceus HE01, mushroom growth and composition of macronutrients. The greatest Hg accumulation was demonstrated for caps. Generally, Hg uptake increased in a concentration-dependent manner and exceeded 44 mg kg⁻¹ (P. ostreatus), 116 mg kg⁻¹ (A. bisporus) and 53 mg kg⁻¹ (H. ercinaceus) in caps after 0.5 mM was added to the substrate. Importantly, an increase in Hg accumulation was also significant and potentially hazardous for human health at the lowest assayed concentration. A. bisporus and P. ostreatus revealed high resistance to Hg and declined its biomass only at 0.4 and 0.5 mM concentration. The presence of Hg did not alter the macronutrient composition (total carbohydrates, proteins and fats). These results highlight the significant role of proper substrate selection in mushroom cultivation to avoid exposing consumers to harmful Hg levels and further health consequences.     

Mineral composition and bioaccessibility in Sarcocornia ambigua using ICP-MS

This study evaluates the nutritional potential of Sarcocornia ambigua as new a source of minerals. The mineral concentrations of two different growing populations (natural occurrence and irrigated) of S. ambigua were evaluated using inductively coupled plasma mass spectrometry. In all samples, the mineral present in highest amounts was potassium (K) (19–24 μg g⁻¹), followed by magnesium (Mg) (8.6–14 μg g⁻¹) and then calcium (Ca) (2.6–4.0 μg g⁻¹). In addition, in vitro bioacessibility assay demonstrated that very high fraction (65–80%) of these K and Mg (80 and 65%) of total concentration of these elements is bioacessible from S. ambigua analyzed. The trace elements vanadium (V), chromium (Cr), cobalt (Co), copper (Cu) and lithium (Li) have more than above 50% of total concentration was found bioaccessible. In all cases, mass balance was verified by carrying out the total digestion of the remaining residue and the relationship between total concentration and bioaccessibility. The data related to the concentrations and the bioaccessible fractions of the minerals provide a starting point for more complex and in-depth evaluations from the nutritional point of view, including the establishment of a recommended daily dietary intake for this plant.     

Synthesis and characterization of functionalized silica with 3,6-ditia-1,8-octanediol for the preconcentration and determination of lead in milk employing multicommuted flow system coupled to FAAS

Novel functionalized silica, containing 3,6-dithia-1,8-octanediol (Si-DIO), was synthesized and characterized by infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscope (SEM) and nuclear magnetic resonance (NMR) of ¹³C and ²⁹Si. The Si-DIO was used to pre-concentrate and determine the amount of Pb(II) in milk samples employing a multicommuted flow system coupled to flame atomic absorption spectrometry (FAAS). For the adsorption process, a pre-concentration minicolumn with 100 mg of Si-DIO, a solution of 0.005 mg L⁻¹ Pb(II) at pH 9.0 and HNO₃ as the eluent was used, obtaining an enrichment factor of 28 times with retention efficiency higher than 99%. The Pb(II) ion, using the multicommuted flow system coupled to FAAS, showed a linear response between 0.005 and 20.0 mg L⁻¹; a linear coefficient where r = 0.9939 and n = 7; a detection limit estimated at 0.001 mg L⁻¹ and a relative standard deviation of 3.8% (n = 50). Fifty pre-concentrations runs were tested in the minicolumn without significant variation in the analytical signal. The proposal system showed analytical applicability to determine Pb(II) ion in milk samples, presenting recovery of 90.7–102.5%.     

Heterocyclic aromatic amines in grilled beef: The influence of free amino acids,nitrogenous bases,nucleosides, protein and glucose on HAAs content

The aim of the study was to determine the content and profile of heterocyclic aromatic amines (HAAs) formed during the process of grilling beef under various conditions and involving different cuts of beef meat. 4,8-DiMeIQx was the most prevalent (4.50–7.55 ng g⁻¹) the next were: MeIQx (1.10–7.20 ng g⁻¹), MeIQ (1.70–5.30 ng g⁻¹), and IQ (0.38 2.00 ng g⁻¹). Changes in HAAs content, depending on the chemical composition of beef meat, were investigated; the compounds under analysis included free amino acids, glucose and protein as well as free nitrogenous bases and their nucleosides. It was demonstrated that HAAs formation strongly correlates with the presence of various amino acids in raw beef as well as that of glucose and protein (correlation coefficient 0.84–0.93). It was also demonstrated that free purine bases, pyrimidine bases and their nucleosides, which had never previously been studied in terms of their role as substrates for HAAs synthesis, correlate very strongly with HAA formation in grilled beef (correlation coefficient 0.78–0.99). The influence of thermal processing at high temperatures on the thermal decomposition of aminoimidazoazaarenes has not been corroborated by the present study.     

Genetic diversity of nutritionally important carotenoids in 94 pea and 121 chickpea accessions

Biofortification of staple crops via breeding is an attractive strategy for reducing human micronutrient deficiencies. The objective of this research was to examine the concentration of carotenoids in diverse pea and chickpea accessions grown in Saskatchewan (Canada) using high performance liquid chromatography. In pea accessions mean concentration of lutein was highest (11.2 μg g⁻¹) followed by β-carotene (0.5 μg g⁻¹), zeaxanthin (0.3 μg g⁻¹), and violaxanthin (0.3 μg g⁻¹). Green cotyledon pea accessions were richer in β-carotene and total carotenoids compared to yellow cotyledon accessions. In chickpea accessions mean concentration of lutein (8.2 μg g⁻¹) was highest followed by zeaxanthin (6.2 μg g⁻¹), β-carotene (0.5 μg g⁻¹), β-cryptoxanthin (0.1 μg g⁻¹), and violaxanthin (0.1 μg g⁻¹). Desi chickpea accessions had higher carotenoid concentration than kabuli accessions. This research identified pea and chickpea accessions that can be utilized in breeding for the improvement of carotenoid concentration through biofortification.     

Profiling antioxidant activity of two primocane fruiting red raspberry cultivars (Autumn bliss and Polka)

Fruit extracts of two raspberry (Rubus idaeus L.) cultivars (Autumn Bliss and Polka) were analysed for total phenolic (TPC) and anthocyanin (TACY) content. Correlation of TPC with total antioxidant capacity (TAC) showed higher free-radical scavenging properties of Autumn Bliss (r² = 0.9999) compared to Polka (r² = 0.8972). Correlation coefficient between TACY and TAC were higher in Autumn Bliss (r² = 0.9939) compared to Polka fruits (r² = 0.8419). Although total protein concentrations were similar in both cultivars (∼0.35 mg mL⁻¹), activities of peroxidases and polyphenol oxidases were much higher in Polka, which were confirmed with isoelectric focusing in cationic (pI 9.3) and anionic (pI 3.6) range. HPLC detection showed that among detected flavonoids (catechin, epicatechin, epicatechin gallate, rutin, myricetin, resveratrol, quercetin and kaempferol) epicatechin appears to be the most abundant compound. Chlorogenic, caffeic and p-coumaric acid were also detected. The results indicate that the changes in enzymes activities related to content of substrates play an important role in nutrient quality definition of raspberry fruits.     

Fast method for the determination of copper,manganese and iron in seafood samples

A slurry sampling flame atomic absorption spectrometric method is proposed for the determination of copper, manganese and iron in oysters (Crassostrea rhizophora), clams (Anomalocardia brasiliana) and mussels (Mytella guiyanensis; Perna perna). Optimization was carried out using univariate methodology involving the following variables: nature and concentration of the acid solution for slurry preparation, sonication time and sample mass. The optimized conditions were 80 mg of sample ground in a cryogenic mil, dilution using 1.0 mol L⁻¹ nitric /hydrochloric acid solution, sonication time of 30 min and a slurry volume of 10 mL. The calibration curves had been prepared using standards of copper, manganese and iron also in 1.0 mol L⁻¹ nitric/hydrochloric acid solution. This method allowed the determination of copper, manganese and iron by FAAS, with detection limits of 0.17, 0.09 and 0.46 μg g⁻¹, respectively. The precision, expressed as relative standard deviation (RSD), are 3.0%, 2.9% and 3.8% (n=10), for concentrations of copper, manganese and iron of 17, 22 and 719 μg g⁻¹, respectively. The accuracy of the method was confirmed by analysis of the certified oyster tissue (NIST 1566b). The proposed method was applied for the determination of copper, manganese and iron in samples of oyster, clams and mussels, collected in Ubatuba and Todos os Santos Bay, Brazil. The obtained concentrations varied between 17.1 and 143.9 μg g⁻¹, 17.9 and 29.7 μg g⁻¹ and 364 and 1388 μg g⁻¹, respectively, for copper, manganese and iron. These values agree well with other data reported in the literature. The results showed no significant differences (P>0.005) using the proposed method with those obtained after complete digestion and determination by inductively coupled plasma-optical emission spectroscopy (ICP-OES).     

PCBs,PCDD/Fs,and PBDEs in blood samples of a rural population in South Germany

The body burden of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), dioxin-like (dl-PCBs) and non-dioxin-like (ndl-PCBs) polychlorinated biphenyls, and polybrominated diphenyl ethers (PBDEs) was determined in blood samples from 70 subjects between 4 and 76 years old. The participants of the study were recruited in the neighborhood of a reclamation plant located in a rural area in Southern Germany.The median concentrations (95th percentiles in parentheses), expressed as WHO₂₀₀₅-TEQ (toxic equivalents), for PCDD/Fs and dl-PCBs were 4.5 (17.9) pg g⁻¹ l.w. and 2.6 (13.2) pg g⁻¹ l.w., respectively. The dl-PCBs contributed 40% of the total TEQ (median values), and the most abundant congener was PCB 156. Combined, the sum of the 6 non-dioxin-like PCBs had a median of 0.773 μg L⁻¹ and a 95th percentile of 4.895 μg L⁻¹. For the six tetra to hepta PBDE congeners, the median was 1.8 ng g⁻¹ l.w. (95th percentile: 16.2 ng g⁻¹ l.w.). None of our study subjects had a body burden that exceeded the biomonitoring equivalents for dioxins or PBDE congener 99 or the human biomonitoring values for ndl-PCBs. Likewise the study group did not exceed German reference values or values obtained in similar investigations.Overall, our study did not exhibit elevated internal exposures. The results also hint further decreasing tendencies for PCDD/Fs, PCBs, and PBDEs in Germany and demonstrates that people in the vicinity of a reclamation plant with no indication of an environmental contamination did not exhibit elevated internal exposures.     

Voltammetric determination of vitamin B6 in food samples and dietary supplements

A simple and rapid voltammetric method based on the use of disposable screen-printed electrodes is proposed for the determination of vitamin B₆. The influence of the pH on the voltammetric response was analyzed. Estimation of the linear range (2.0 × 10⁻⁶/7.2 × 10⁻⁵ M), calibration function, limit of detection (1.5 × 10⁻⁶ M) and reproducibility was performed along with the determination of possible interferences from species present in real samples. The proposed analytical system was successfully applied for the determination of pyridoxine in multivitamin supplements, energy drinks and breakfast cereals by using the standard addition method.