Development of an Efficient Acid Digestion Procedure Utilizing High-Pressure Asher Technique for the Determination of Iodine and Metallic Elements in Milk Powder

An effective wet digestion procedure for the determination of total iodine contents in milk powder samples was developed utilizing a high-pressure asher technique. The optimized method based on a two-stage digestion procedure. In the first stage, 500 mg samples were digested at 300 °C for 2 h using 15.2 mol L^?1 HNO₃ (5 mL) and 30 % H₂O₂ (3 mL). After the first digestion stage, digestion vessels were allowed to cool down and 1.2 mL of 20 % (w/v) Na₂S₂O₈ solution was added as an additional oxidizing agent to the samples. After that, the vessels were closed, and they were heated at 100 °C for 30 min, resulting in clear and colorless sample solutions. Iodine concentrations in the digested samples were measured with inductively coupled plasma mass spectrometry. The accuracy of the optimized method was confirmed by analyzing milk powder reference material (BCR-151, milk powder). The obtained value for iodine (5.29?±?0.37 mg kg^?1, n?=?6) was in good agreement with the certified value (5.35?±?0.14 mg kg^?1). Furthermore, the results obtained for reference material showed that the developed method can be applied also for the determination of other elements, e.g., copper, iron, and lead in the digested milk powder samples.     

Quantification of Se-Methylselenocysteine and Its γ-Glutamyl Derivative from Naturally Se-Enriched Green Bean (Phaseolus vulgaris vulgaris) After HPLC-ESI-TOF-MS and Orbitrap MS n -Based Identification

Orthogonal liquid chromatographic (ion exchange, reversed phase, and ion pairing) and mass spectrometric [electrospray ionization (ESI)-TOF-MS, ESI-Orbitrap MS, and inductively coupled plasma mass spectrometry (ICP-MS)] methods were addressed to identify and quantify selenium species from a naturally Se-enriched green bean (Phaseolus vulgaris vulgaris) sample after proteolytic digestion. While selenomethionine (10.1 mg/kg as Se) and selenate (9.5 mg/kg as Se) could be quantified in a straightforward way by anion exchange LC-ICP-MS technique, a multistep purification protocol was required to identify Se-methylselenocysteine and γ-glutamyl-Se-methylselenocysteine in an unambiguous way prior to quantification by using either in-source fragmentation (LC-ESI-TOF-MS) or collision-induced dissociation (LC-ESI-Orbitrap MS). Finally, Se-methylselenocysteine (2.6 mg/kg as Se) and γ-glutamyl-Se-methylselenocysteine (1.2 mg/kg as Se) could contribute to the overall selenium recovery of 72 %. This sample is the first of the Faboideae subfamily and Phaseolus ssp. to be speciated to such an extent for selenium including γ-glutamyl-Se-methylselenocysteine, a highly potential selenium species, which makes this bean material an ideal candidate for functional food purposes.     

Development of a Precolumn Derivatization Procedure Prior to Ultrasound-Assisted Cloud Point Extraction for Sensitive Determination of Fluoroquinolones in Eggs by High-Performance Liquid Chromatography with Fluorescence Detection

In this work, a 4-chloro-7-nitrobenzodioxazole (NBD-Cl) derivatization coupled with the ultrasound-assisted cloud point extraction (UACPE) method prior to high-performance liquid chromatography with fluorescence detection (HPLC-FLD) analysis was developed for the determination of four widely used fluoroquinolones (FQs) including norfloxacin (NOR), ciprofloxacin (CIP), sarafloxacin (SAR), and gatifloxacin (GAT) in eggs. The derivatives of FQs with NBD-Cl were extracted into the Triton X-114 surfactant-rich phase, which was analyzed by reversed-phase HPLC-FLD. Ultrasound was applied to accelerate the phase separation in extraction and enhance the extraction efficiency of target analytes. Variable parameters affecting the derivatization and UACPE procedure were systematically evaluated and optimized. Under the optimum conditions, four FQs were successfully separated within 30 min through an Agilent TC-C₁₈ column. Good recoveries of 86.2–103.5 %, which were calculated using a range of spiked samples at three concentrations, were obtained by UACPE. The calibration graphs were linear over the range of 1.2–73.0 μg kg^?1 for four FQs with correlation coefficients (R) no less than 0.9957. The limits of detection were 0.2, 0.5, 0.3, and 0.4 μg kg^?1 for NOR, CIP, SAR, and GAT, respectively. The precisions indicated by relative standard deviations ranged from 0.6 to 4.3 % for both intraday and interday analysis. The proposed method proved to be a selective, sensitive, and eco-friendly approach which was successfully applied to analyze FQs in eggs at the local farmers market, and none of the target analytes were detected in these samples.     

UV-Visible Spectroscopy and Multivariate Classification as a Screening Tool to Identify Adulteration of Culinary Spices with Sudan I and Blends of Sudan I + IV Dyes

This work propose a feasible, rapid, and simple method for detecting culinary spices adulterated either with Sudan I dye or blends of Sudan I + IV dyes at three concentration levels. The method is based on the use of UV-visible spectroscopy with multivariate analysis. Four types of spices were studied: three paprika varieties (mild, hot, and smoked) and a spice commonly consumed in Argentina called aji molido. Principal components analysis was firstly applied as an exploratory analysis and then, two classification techniques were used: K-nearest neighbors (KNN) and partial least squares-discriminant analysis (PLS-DA). Three classes were defined: unadulterated samples and adulterated samples with Sudan I or blends of Sudan I + IV dyes at 1, 2.5, and 5 ppm (mg L^?1). Classification techniques gave satisfactory results: between 89 and 100 % for PLS-DA and between 83 and 92 % for KNN. The sensitivity and specificity of the models were above 83 %. It has to be highlighted that none of the adulterated samples were assigned as unadulterated, which is very positive because of the implication that these results have on consumer health. The capability of detecting mixtures of Sudan dyes is a very important advantage because each Sudan dye generates different hazardous metabolites in human body so their toxicity may be enhanced by the simultaneous presence of such dyes.     

An LC-IT-MS/MS-Based Method to Determine Trichothecenes in Grain Products

The aim of this work was to evaluate the usefulness of the ion trap mass spectrometry coupled to high-performance liquid chromatography for simultaneous determination of selected trichothecenes (nivalenol, deoxynivalenol, fusarenon-X, neosolaniol, 3-acetyl-deoxynivalenol, diacetoxyscirpenol, HT-2 and T-2 toxins) in grain products. These compounds were extracted from the grain products and then cleaned up with the developed, simple and robust procedure using some mixture of neutral alumina, charcoal and diatomaceous earth. Method recovery was 88–125 % depending on combination of the analysed mycotoxins, sample matrix and the fortification level. Method precision expressed by relative standard deviation ranged from 2.6 to 27.4 %. The concentrations of the selected trichothecenes have been determined in 94 samples of cereal-based products. Maize-based next to wheat-based products were the most contaminated with deoxynivalenol, neosolaniol, 3-acetyl-deoxynivalenol, diacetoxyscirpenol and HT-2 toxin. In 83 % of wheat-based products, deoxynivalenol was determined at the average level of 249 μg kg^?1. The highest concentration of deoxynivalenol—2,026 μg kg^?1 (476?±?471 μg kg^?1 on the average)—was found in the maize-based product. Other mycotoxins were found much less frequently: 3-acetyl-deoxynivalenol in only one sample at the concentration of 59 μg kg^?1, neosolaniol, HT-2 toxin and diacetoxyscirpenol in a few samples on average concentrations close to respective limits of quantification.     

Rapid Quantification of Soyasaponins I and βg in Italian Lentils by High-Performance Liquid Chromatography (HPLC)–Tandem Mass Spectrometry (MS/MS)

In this work, an innovative and fast analytical method for the quantification of soyasaponins I and βg in lentils has been developed. Samples were extracted using 70 % aqueous ethanol at room temperature and then injected into a high-performance liquid chromatography–tandem mass spectrometry system. The correlation coefficients of calibration curves of the analyzed compounds were ≥0.9997. The recoveries obtained by spiking the lentil samples with a standard mixture of soyasaponins I and βg at 50 and 100 mg l^?1 were in the range of 96–101 and 98–103 %, respectively. The validated method was applied to the analysis of 30 lentil samples from central Italy. Soyasaponins I and βg were present in these lentils in concentrations that ranged from 54 to 226 mg kg^?1 and from 436 to 1,272 mg kg^?1, respectively. Our data indicated that lentils cultivated in fields at intermediate altitudes (1,142–1,387 m) showed the highest levels of soyasaponins, a finding confirmed by principal component analysis.     

Analysis of Fourteen β-Agonists in Weight-Reducing Dietary Supplements Using QuEChERS-Based Extraction Followed by High Resolution UHPLC-MS

In the present study, a method for analysis of 14 β-agonists in weight-reducing dietary supplements using the QuEChERS procedure followed by UHPLC-ESI/MS-MS based on two scan events (full scan FTMS and HCD data dependent MS/MS) in positive ionization mode has been developed. Sample extraction and purification were carried out using a modified QuEChERS method. Rapid analysis was carried out by ultra-high performance liquid chromatography coupled with high resolution Fourier transform mass spectrometer. Fourteen β-agonists were separated within 15 min with limit of detection in the range of 1.8–23.1 μg kg^?1. The average recoveries in spiked dietary supplements varied from 67.1 to 107.3 %, which were carried out with spiked samples at three concentration levels. Validation parameters including linearity and repeatability were satisfactory. Finally, based on the results, it is concluded that the proposed method is an appropriate procedure for β-agonists analysis in weight-reducing dietary supplements.     

Aluminium and Its Complexes in Teas and Fruity Brew Samples,Speciation and Ions Determination by Ion Chromatography and High-Performance Liquid Chromatography–Fluorescence Analytical Methods

The paper presents results of aluminium determination in samples of black and fruit teas. Total aluminium concentration was determined along with the concentration of aluminium in a cup of tea in tea samples in two price groups (>1€ and <1€). Based on the conducted study, no differences were found in aluminium concentration in black and fruit teas depending on the price group. Developed ion chromatography method was applied to determine inorganic and organic ions in tea samples, especially those which may form complexes with aluminium: fluoride, sulphate, oxalate and citrate ions. Analysis by this method using ion chromatography allowed for the determination of 12 anions: F^?, HCOO^?, CH₃COO^?, NO₂ ^?, Br^?, NO₃ ^?; Cl^?, CH₂(COO)₂ ^2?, SO₄ ^2?, C₂O₄ ^2?, PO₄ ^3? and C₃H₅O(COO)₃ ^3? in the time of 40 min. Speciation analysis of aluminium was performed in optimised HPLC-fluorescence analytical system (with Lumogallion as a post-column reagent). It was observed that organic aluminium complexes are quickly degraded to form Al³⁺ which is the reason why speciation analysis in tea samples does not provide the full image of speciation distribution. Nevertheless, this developed method was successfully used in the determination of aluminium complexes with fluorides in tea samples.     

Improvement of Determination of Trace Amounts of Arsenic and Selenium in Slim Coffee Products by HG-ICP-OES

A method for the determination of total inorganic arsenic and selenium in slim instant coffees using hydride generation inductively coupled plasma optical emission spectrometry (HG-ICP-OES) was proposed. Various sample preparation procedures, including the traditional total decomposition by the hot-plate or microwave heating in a HNO₃/H₂O₂ mixture and alternative procedures based on the solubilisation in aqua regia or tetramethyl ammonium hydroxide (TMAH) and the dilution only with water or a low concentrated HNO₃ solution were examined and compared. Corresponding As and Se hydrides were generated in the reaction of an acidified sample solution with the NaBH₄ reductant in the presence of antifoam A. A small sample preparation with aqua regia in an ultrasonic bath followed by the pre-reduction with KI–ascorbic acid in the HCl medium for total As and the boiling with HCl for total Se were found to be optimal. The external calibration using standards treated and measured as the same as samples were applied for the analysis. Limits of detection (LODs) of 0.96 and 0.55 ng ml^?1 were assessed for As and Se, respectively. The precision (as the relative standard deviation [RSD]) was within 1.6–7.1 %. The accuracy of the method was confirmed by the recovery test and the analysis of a standard reference material (non-fat milk powder, SRM 1459). The developed procedure was applied for the analysis of six commercial instant slim coffee products available in the Polish market and it was found that these products contain traces of As (0.114–0.247 μg g^?1) and Se (0.089–0.137 μg g^?1).     

Application of Box–Behnken Design in the Optimization of In Situ Surfactant-Based Solid Phase Extraction Method for Spectrophotometric Determination of Quinoline Yellow in Food and Water Samples

In this work, a simple, rapid and sensitive method using in situ surfactant-based solid phase extraction (ISS-SPE) combined with UV–vis spectrophotometry has been developed for the preconcentration and determination of trace amounts of quinoline yellow in food and water samples. The Box–Behnken design was employed to optimize the extraction efficiency. The variables of interest were pH, surfactant volume, extraction time and NaI volume. In the optimal conditions, the calibration graph was linear in the range of 10.0–750 μg L^?1 with a correlation coefficient of 0.9982. The limit of detection (LOD) was 2.1 μg L^?1, and the preconcentration factor was calculated to be 51.8.     

A New Gas Chromatography Method for Quality Control of Methylsulfonylmethane Content in Multicomponent Dietary Supplements

This paper reports the first gas chromatography method with flame ionization detection (GC–FID) for rapid assay of the quality control of methylsulfonylmethane (MSM) content in multicomponent dietary supplements. The proposed method was completely validated and used for quality control of multicomponent dietary supplements available in the local market. The study showed that the content of MSM varied in different commercial samples (77.7–112.3 % of the declared amount) and was dependent on different qualities of the dietary supplement producer. The developed method was based on the rapid extraction of MSM into acetone using ultrasound bath (5 min) and on the subsequent quantification of the MSM by gas chromatography. The used GC conditions were as follows: fused silica cyanopropylphenylmethylpolysiloxane capillary column Alltech AT^TM-624 (30 m?×?0.32 mm i.d., 1.8-μm film thickness), injection mode split of 1:10, sample volume of 1.0 μL, injector temperature of 190 °C, detector temperature of 190 °C, column temperature held at 190 °C for whole analysis time, and helium carrier gas flow rate of 0.7 mL min^?1. Nitrobenzene was chosen as internal standard for precise and accurate quantification of MSM in dietary supplements. Method precision evaluated as relative standard deviation was 1.7 %, and method accuracy evaluated as recovery was in the range of 102.5–106.2 %. The method required no special sample pretreatment, so it showed to be simple, robust, rapid (short analysis time of less than 4 min), and suitable for routine analysis of MSM in food quality control laboratories.     

Optimisation of Glucose Biosensors Based on Sol–Gel Entrapment and Prussian Blue-Modified Screen-Printed Electrodes for Real Food Analysis

In this study, we report the construction of amperometric screen-printed glucose biosensors for food analysis by using two procedures for Prussian Blue (PB) deposition and different membranes for enzymatic immobilisation. The comparison between the screen-printed electrodes modified with PB by electrochemical and chemical deposition showed higher analytical performance (detection limit of 1 μM, linear range from 0.5 to 500 μM and a sensitivity of 823 μA mM^?1 cm^?2) when the latter was employed. Then, the immobilisation of glucose oxidase (GOD) by silica sol–gel and polyvinyl alcohol (PVA) hydrogel was performed on electrochemically modified PB electrodes. The electrochemical response of two glucose biosensors was evaluated by flow injection analysis. Biosensors constructed by silica sol–gel entrapment showed a wider linear range (0.005–1 mM) and a detection limit (0.02 mM) that was 10-fold lower than using entrapped GOD in PVA. The selected glucose biosensor showed negligible interference from ascorbic acid when the Nafion membrane was used to cover the PB-modified electrode surface. Additionally, it exhibited an operating lifetime of 8 h under continuous glucose injections ranging from 0.01 to 2 mM. Finally, the biosensor was applied for specific determination of glucose in red and white wines, juices and dried fruit.     

A Fast and Accurate UPLC Method for Analysis of Proteinogenic Amino Acids

A reliable and inexpensive method for the measurement of proteinogenic amino acids was developed. It allows the screening of large sample volumes that is important for current food and feed applications, but also for future biobased applications. The method is based on acid hydrolysis and automated pre-column derivatision in the injection needle of the autosampler using o-phthalaldehyde/ethanethiol reagent in combination with 9-fluorenylmethyl chloroformate. The calculated mean limit of detection and limit of quantification of pure amino acids were 2.3 and 4.6 μM, respectively. With this method, it was possible to accurately analyse the amino acid composition of bovine serum albumin, soy meal, Jatropha press cake, and cyanophycin. Mean reproducibility of all amino acids from bovine serum albumin was 6.8 %, with a mean recovery of 95 %. The sample run time is 16 min with a total cycle time from injection to injection of an acid hydrolyzed sample of 22 min, resulting in a greener method due to a reduction in solvent consumption.     

Graphene Reinforced Hollow Fiber Liquid Phase Microextraction for the Enrichment of some Phenylurea Residues in Milk Sample

Graphene, as a kind of novel and interesting carbon material, has gained much attention in recent years. In this paper, a new sample preparation technique, graphene reinforced hollow fiber liquid phase microextraction (G-HF-LPME), was developed and used to pre-concentrate some phenylurea herbicides (chlortoluron, isoproturon, diuron, monolinuron, and buturon) in milk sample prior to high-performance liquid chromatography–ultraviolet detection. Different parameters influencing the extraction efficiency of the G-HF-LPME were investigated and optimized. Under the optimized conditions, a good linearity was observed in the range between 10.0 and 400.0 μg L^?1 with the correlation coefficients ranging from 0.9911 to 0.9987. The limit of detection (S/N?=?3) of the method was lower than 2.0 μg L^?1. The developed method is simple, efficient, and has been successfully applied to the determination of the phenylureas in milk samples.     

Determination of Deoxynivalenol-3-Glucoside in Cereals by Hydrophilic Interaction Chromatography with Ultraviolet Detection

A new hydrophilic interaction liquid chromatography (HILIC) method was developed for the determination of deoxynivalenol-3-glucoside (D3G) in cereals. D3G was extracted with water and cleaned with an immunoaffinity (IA) column, followed by chromatographic separation on a Syncronis HILIC column with acetonitrile-water (90:10, v/v) as the mobile phase, and detected at 220 nm by UV detection. The calibration curve was found to be linear in the range of 0.1–2.0 μg/ml. Limit of detection and limit of quantification were 8 and 25 μg/kg, respectively. The method was applied to the determination of D3G in 14 cereal samples, which were analyzed as well as by LC-MS/MS. The results indicate that the method can be considered as an alternative to LC-MS/MS and could be adopted by nonprofessional analytical labs.     

Optimization of Sample Preparation in the Determination of Minerals and Trace Elements in Honey by ICP-MS

In this paper, analytical procedures are proposed for determination of inorganic constituents in honey samples from different regions of Brazil. Inductively coupled plasma with mass spectrometry detection (ICP-MS) was used to determine the analytes, using two different sample preparation methods: acid mineralization in block digester and microwave-assisted acid digestion. The methods were optimized in order to minimize the final acidity and the residual carbon content after the sample preparation. It was observed that mineralization using microwave radiation with 2 mol L^?1 HNO₃ was the most suitable method for determination of minerals and trace elements by ICP-MS. Besides, Se, Mg, Ca, Al, P, Mn, Fe, Cu, Zn, Ba, and Pb were determined in 60 honey samples by ICP-MS. The appropriate instrumental conditions were also evaluated for this determination, as the need of the use of collision–reaction interface and internal standards. The accuracies were evaluated using two certified reference materials, and the recoveries ranged from 82 to 115 %. The results showed no evidence of contamination in the honey samples analyzed.     

Characterization of Volatile Organic Compounds of Vinegars with Novel Electronic Nose System Combined with Multivariate Analysis

A novel electronic nose system (also called artificial olfaction system) based on colorimetric sensor array was developed for characterization and identification of the volatile organic compounds (VOCs) of vinegars fermented from different raw materials. Fifteen chemo-responsive dyes including nine metalloporphyrins and six pH indicators were selected according to their sensitivity to volatile compounds from vinegar samples. The colorimetric sensor array was made by printing selected chemo-responsive dyes on a silica gel plate. A color change profile for each sample was obtained by differentiating the images of the colorimetric sensor array before and after exposure to the odorant of vinegar sample. The digital data (i.e., red, green, and blue components of the image) representing the color change profiles for the vinegar samples were analyzed. Genetic algorithm partial least squares was employed to select sensitive image digital variable to build a calibration model. Several methods (i.e., linear discrimination analysis, LDA; partial least square discrimination analysis; artificial neural network) were also used comparatively for classification, the result was evaluated by the % correct identification of samples. The optimal model was achieved by LDA model with 14 image digital variables used, and all the vinegar samples were correctly identified both in training and testing sets. This research suggests that the system shows significant potential in vinegar VOCs characterization and discrimination.     

Ridgetail White Prawns,Exopalaemon carinicauda,Storage Time Rapid Determination Using Electronic Nose

Ridgetail white prawns, Exopalaemon carinicauda, storage time rapid determination method based on electronic nose was investigated in this paper. Prawns were stored at 4 °C for 9 days. Each day, electronic nose responses, and total volatile basic nitrogen index were measured during the storage period. Total volatile basic nitrogen index provided a freshness standard according to China standard protocols. Signal-to-noise ratio spectrum calculated by stochastic resonance discriminates prawn samples under different storage days successfully. Prawns' storage time determination model was developed based on signal-to-noise ratio eigenvalues. Validating experiments demonstrated that this model predicted prawn storage time with an accuracy of 90 %. Prawn freshness critical value ?82.77066 was also obtained by referring to total volatile basic nitrogen index and the developed model. This method is promising in seafood freshness evaluation.     

A New Ultrasonic Thermostatic-Assisted Cloud Point Extraction/Spectrophotometric Method for the Preconcentration and Determination of Bisphenol A in Food,Milk, and Water Samples in Contact with Plastic Products

Bisphenol A (BPA) contamination in foods and beverages usually occurs as a result of migration from the packages that contain it. In this context, a simple, easy-to-use, and efficient method was developed for the spectrophotometric determination of BPA in food, milk, and water samples in contact with plastic products after preconcentration by ultrasonic-thermostatic-assisted cloud point extraction (UTA-CPE). The method is based on the charge transfer-sensitive complexation of BPA with 3-methylamino-7-dimethylaminophenothiazin-5-ium chloride (AzB) in the presence of cetyltrimethylammonium bromide (CTAB) at pH 8.5 and then extraction of the formed complex into the micellar phase of polyethylene glycol dodecyl ether (Brij 35). The effects of the analytical variables affecting complex formation and extraction efficiency were systematically studied and optimized. Under optimized conditions, a good linear relationship was obtained in the range of 1.2–160 μg L^?1 with a detection limit of 0.35 μg L^?1. After preconcentration of a sample of 20 mL, a sensitivity enhancement factor was found to be 180. The accuracy and reliability of the method were evaluated by recovery studies from the spiked quality control samples and intraday and interday precision studies. From the studies conducted, the extraction efficiency (E%) was in the range of 94–103% with a relative standard deviation lower than 5.2% (as RSD%, n = 5). The method was successfully applied to the preconcentration and determination of BPA from the selected sample matrices.

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Graphical Abstract Migration of bisphenol A into the foodstuffs

     

A Simple,Low-Cost,and Useful Preconcentration Method for Quantification of Soluble,Insoluble, and Total Oxalate in Selected Vegetables Through Spectrophotometry

The amount of dietary oxalate from food may be an important risk factor in the development of idiopathic calcium oxalate nephrolithiasis. The main aim of this research was to develop an accurate and reliable method by cloud point extraction (CPE) combined with spectrophotometry to measure the oxalate contents of selected vegetables. The method is based on ion association of stable anionic complex, which is produced by the reaction of oxalate with Mo(VI), with Toluidine blue (TBH²⁺), and then by extraction into micelles of octylphenol ethoxylate (Triton X-45) in the presence of NH₄F as a salting-out agent at pH 6.0. Using the optimized conditions, the calibration graph was highly linear in the range of 1.2–240 μg L^?1. The detection limit of the method (LOD (3σ _blank/m) was 0.36 μg L^?1, and the relative standard deviation (RSD %) as a measure of precision was in the range of 1.1–5.3 % (n?=?5 for 5, 25, and 50 μg L^?1). The method was successfully applied to the speciative determination of soluble and total oxalate in vegetables after ultrasonic-assisted extraction and dilution at suitable ratios. The amount of insoluble oxalate was calculated from the analytical difference between total oxalate and soluble oxalate contents of samples with and without acidic extraction under ultrasonic power (300 W, 50 Hz) for 15 min at 60 °C. The accuracy of the method was intrinsically controlled and verified by comparing the results obtained with those of an independent kinetic method as well as recoveries of spiked samples.

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Graphical Abstract Experimental steps of the proposed method