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 (3σblank/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.
A new indirect preconcentration procedure was developed for micellar sensitive detection of trace nitrite as analyte by spectrophotometry. The method is based on ion association of triiodide ion, I3? or I2, produced by the reaction of nitrite at low concentrations with excess iodide in presence of ion-pairing agent, Coomassie brilliant blue R 250 (CBB), and electrophilic attack of nitrosyl cation produced by disproportionation of nitrite depending on concentration to ion-pairing agent at higher concentrations than 5 μg L?1 in acidic medium, and then extraction of the ion-pairing complex formed from aqueous solution into the micelles of Triton X-114 at sodium acetate medium. The calibration graphs were rectilinear in the range of 0.5–5 and 5–200 μg L?1 with increasing and decreasing slopes in micellar phase, respectively. The detection and quantification limits of the method were 0.15 and 0.50 μg L?1, and the precision (as RSD) for five replicate measurements of different concentrations of nitrite was in the range of 2.3–4.8%. The average recoveries of spiked nitrite residues ranged from 97 to 104%. The method is free of matrix interferences and successfully applied to the indirect determination of nitrite, nitrate, and total nitrite in selected two groups of foods. Also, the accuracy was validated by analysis of a certified reference material as well as recoveries of spiked samples. The objective of the study is to provide an alternate economical method to determine the contents of nitrite, nitrate, and total nitrite after homogenization, extraction, reduction, and preconcentration from sample matrix.
In the current study, a new cloud point extraction (CPE) procedure was developed for the separation and preconcentration of inorganic soluble As species, As(III), As(V), and total As in water and beverage samples. Selective ion-pairing complex of As(III) with Neutral red (NRH+) being a cationic phenazine-based dye in presence of citric acid at pH 2.0 was extracted into the surfactant-rich phase of octylphenoxypolyethoxyethanol (Triton X-114) from samples. After phase separation, the preconcentrated As(III) was determined by means of spectrophotometer at 542 nm. After optimization of the CPE conditions, a preconcentration factor of 50 and the detection and quantification limits of 1.44 and 4.8 μg L?1 with a correlation coefficient of 0.9953 were obtained from the calibration curve constructed in the range of 5–1500 μg L?1 for As(III). The precision of the method (as RSD) was in the range of 2.2–4.5 % (25, 100, and 750 μg L?1, N?=?5). The As(V) contents of samples were calculated from the difference between As(III) and total As contents after the reduction of As(V) to As(III) with mixture of KI and ascorbic acid at HCl media. The method is very versatile and inexpensive because it exclusively used conventional UV–Vis spectrophotometry. The method was succesfully applied to the simultenous determination of inorganic arsenic species in different water and beverage samples. Its accuracy and precision were controlled by analysis of two certified reference materials (CRMs).
Olaquindox (OLA), used as a medicinal feed additive, has been put under ban due to hazard concerns over animal-derived food security. In this study, a simple, rapid, ultrasensitive, and quantitative gold immunochromatography assay (GICA) was established to analyze OLA in animal feed samples and surface water samples to monitor food security. Various trying has been experimented to improve the sensitivity. The IC50 of the optimized method is 3.35 μg L?1 for feedstuff and 0.35 μg L?1 for environmental water. The recoveries ranged from 77.33 to 86.91 % (CV <23.62 %) for spiked feedstuff and 96.30 to 117.83 % (CV <22.51 %) for spiked water samples. Then, the developed GICA was applied to animal feed and field water, followed by confirmation with ELISA and the consistency of results indicated that the developed GICA could be applied for rapid screening of OLA in real samples. Compared with previous assay, the developed GICA in this study was more sensitive and more rapid, which exhibited broader prospect to supervise the animal products and water rapidly.
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.
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. 相似文献
The effect of edible cassava starch–chitosan coatings incorporated with rosemary pepper (Lippia sidoides Cham.) essential oil and pomegranate peel extract on the shelf-life of tomatoes during storage at 25 °C for 12 days was investigated. Sixteen formulations, containing 10 g L?1 cassava starch and various concentrations of chitosan (5, 10, 20, 30 g L?1), essential oil (0, 2.5, 5, 10 mL L?1) and pomegranate peel extract (0, 5, 10, 20 mL L?1) were prepared and applied to tomatoes. Physical–chemical and microbiological analyses were performed on days 1, 4, 8 and 12. Most of the coatings delayed the ripening of tomatoes, lowering the total soluble solids (38?44 g sucrose kg?1) and weight loss (93?128 g kg?1) and maintaining constant firmness compared to the uncoated tomatoes (45 g sucrose kg?1, 175 g kg?1) at 12 days of storage. Conversely, except red intensity (a*), which was higher for the uncoated samples, the colour parameters (L*, b*) of the coated and control tomatoes were similar at the end of storage. Uncoated and coated tomatoes showed no contamination during storage. The coatings showed potential to maintain the quality of tomatoes during storage at 25 °C for 12 days. In this context, tomatoes coated with the formulation comprising 10 g L?1 cassava starch, 10 g L?1 chitosan, 10 mL L?1 essential oil and 20 mL L?1 pomegranate peel extract showed the lowest weight loss and reduced total soluble solids content compared with uncoated ones. 相似文献
A low-cost and portable LED-based photometer was developed and applied for in situ determination of copper in sugarcane spirit. The determination was based on the chelation reaction between copper(II) and cuprizone (bis(cyclohexanone)oxalyldihydrazone). After optimizing the best experimental variables, a dynamic linear range to determine copper(II) was linear from 1.0 to 12.0 mg L?1 (r2?=?0.999) with the limits of detection and quantification of 0.20 and 0.70 mg L?1, respectively. The recovery of copper ranged from 96.5 to 104.4%. The paired t test was performed, and the results agreed at 95% level of confidence. The analytical method LED-based photometer demonstrated that it can be employed to determine copper in sugarcane spirit for quality purpose, e.g., small rural producers can evaluate the drink quality before bottling due to the easy handling, portability, fast response, and low-cost of the materials used.
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. 相似文献
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. 相似文献
The antioxidant capacity (AC) of rapeseed, white flakes, and meal was determined by the novel cerium oxide nanoparticle-based (CeONP) method and a previously described assay based on the formation of silver nanoparticles (AgNP). Antioxidants present in rapeseed and its by-product extracts reduced cerium(IV) ions to red-purple solutions of cerium oxide nanoparticles at pH 5.6. The influences of time, temperature, pH, and the concentration of the cerium(IV) sulfate solution on cerium oxide nanoparticle generation were estimated. The average AC of the studied extracts of real samples ranged between 1037 and 3012 μmol sinapic acid (SA) 100 g?1 and 3859–12,534 μmol SA 100 g?1 for CeONP and AgNP assays, respectively. There is significant, positive correlation between the AC of the examined extracts determined by both analytical methods (r?=?0.8189). Satisfactory values of relative standard deviation (RSD?=?1.2–3.9 %) and recovery (95.8–103.3 %) demonstrate a good precision and accuracy of the novel CeONP method for the AC analysis of rapeseed and its by-products.
This study was conducted to design a biosensor as a new, rapid, and sensitive tool for investigation of binding of zearalenone with double-stranded DNA (dsDNA). Polydiallyldimethylammonium chloride (PDDA) as a polycation and multiwall carbon nanotubes (MWCNTs) provide a positively charged surface with a high surface area for the immobilization of dsDNA as a polyanion on the surface of pencil graphite electrode (PGE). Using the dsDNA/MWCNT–PDDA-modified PGE, it was possible to detect the interaction of zearalenone with dsDNA, which allowed us to apply the dsDNA-modified electrode for trace determination of zearalenone. The changes at the oxidation signal of adenine were evaluated before/after each modification/immobilization step. By using dsDNA/PDDA–MWCNT/PGE, zearalenone could be detected as low as 0.005 ng mL?1. The relative standard deviation of five measurements of 0.5 ng mL?1 zearalenone was found to be 4.2 %. Finally, the highly stable electrochemical biosensor was applied to analyze the zearalenone concentration in milk and wheat samples.
Polyether antibiotics have been widely used for the treatment and prevention of coccidiosis in chicken farming. In the present study, an efficient, simple and inexpensive competitive indirect enzyme-linked immunosorbent assay (ciELISA) method based on immunomagnetic sample clean up was developed for salinomycin. Monoclonal antibodies were immobilized on the surface of carboxylic acid magnetic beads (2.8 μm in diameter). After a simple extraction, residues in sample extracts were specifically adsorbed and the supernatant removed by magnetic separation. Analytes retained on the beads were then released by elution prior to ciELISA. The limit of detection for salinomycin in chicken muscle and liver was 22 and 18 ng mL?1, respectively, and the linear quantitative range was 47–653 ng mL?1. Intra-assay recoveries ranged from 86.00 to 99.32%, and inter-assay recoveries were between 85.68 and 96.34%. The inhibition efficiency and sensitivity of this method was improved compared with traditional hydrophilic-lipophilic balance column clean up ciELISA. Furthermore, the convenience and repeatability of the immunomagnetic cleanup renders the new method of high value for the analysis of drug residues in complex matrices.
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. 相似文献
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. 相似文献
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. 相似文献
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. 相似文献
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. 相似文献
White croaker surimi, an important raw material of traditional kamaboko industry, commonly has four grades, A, AA, FA, and SA which have distinct quality but are tough to be identified and discriminated rapidly and holistically by conventional methods. A Tri-step infrared spectroscopy, Fourier transform infrared spectroscopy (FT-IR) integrated with second derivative infrared (SD-IR) spectroscopy, and two-dimensional correlation infrared spectroscopy (2DCOS-IR), combined with statistical pattern recognition, was employed to rapidly characterize and discriminate four grades of white croaker surimi (A, AA, FA, and SA). The four surimis had similar IR, and SD-IR macro-fingerprints (similarity >0.9) especially for the absorption bands of amide groups due to proteins were the main compositions. However, relative contents of lipids in all surimis could be directly observed. Compared to the other three surimis, SA had a middle strong characteristic peak of lipids at 1745 cm?1, indicating that SA had the highest content of lipids. The sequence of lipid contents in the four surimis was SA > FA > AA > A, which was further verified by SD-IR spectra. Moreover, evident differences were disclosed visually in 2DCOS-IR spectra of 1680–1610 cm?1, indicating that the four surimis have fine differences in protein secondary structures. Furthermore, 76 parallel samples (18 A, 19 AA, 19 FA, and 20 SA) were objectively classified by soft independent modeling of class analogy (SIMCA) based on principal component regression (PCR). It has been demonstrated that the Tri-step infrared spectroscopy combined with cluster analysis could be a scientific and powerful tool for rapid discrimination and identification of different grades of surimi in a holistic manner.
Pesticides in food are a major issue due to their intensive use in agriculture. Thus, an appropriate control of their residues in food samples should be done. In this study, a multiresidue method for the quantification of 37 pesticides in whole wheat flour was developed and validated. The modified QuEChERS (without cleanup) procedure followed by ultra-high performance liquid chromatography coupled to tandem mass spectrometry (UHPLC–MS/MS) was used for analysis. The method was validated according to the European Union SANCO/12,571/ 2013 guidelines and Brazilian Manual of Analytical Quality Assurance. The following parameters were evaluated on the method validation: linearity, limit of detention, limit of quantification, matrix effect, precision, accuracy evaluating the percentage of recovery at three different spike levels, and robustness. Acceptable values were obtained. The linear range used was 1–200 μg kg?1, resulting to r2 of >0.99. The recovery was satisfactory with 70 and 120 % and RSD of <20 % for most compounds. Assessing the samples collected in the south Brazil region, some pesticide residues were detected in whole wheat flour (carbendazim, chlorpyrifos, deltamethrin, imidacloprid, malathion, pendimethalin, pirimiphos-methyl, triamedifom, and triadimenol). The applicability of this analytical approach was confirmed by successful determination of pesticides in whole wheat flour, a complex matrix.
