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.
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.
Interlaboratory validation procedures were proposed and performed to confirm the effectiveness of modified classical qualitative methods for the detection of adulterants in milk, including starch, chloride, and sucrose, which were previously validated by a single laboratory approach. Raw milk samples that were adulterated with 150 g L?1 of water and 0.0, 0.3, 0.8, and 1.2 g L?1 of starch, 0, 1.5, 2.0, and 2.5 g L?1 of chlorides, and 0.0, 2.4, 3.0, and 3.6 g L?1 of sucrose were sent to 10 collaborators in Brazil that represent the government, food control, food industry, and university affiliations. Reliability rates of 93 to 100, 98 to 100, and 99 to 100 % were obtained for the starch, chlorides, and sucrose methods, respectively. The prediction intervals for the probability of detection proved the sensitivity and selectivity of the methods. Concordance values were greater than 0.85 to starch, 0.98 to chlorides, and 0.99 to sucrose, indicating precision and that the procedures were properly standardized between the collaborators. The estimated detection limits and unreliability regions confirmed the fitness of the modified methods for their respective purposes.
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.
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 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.
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.
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.
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.
A polyvinylidene fluoride membrane-based dot immunoassay using nanobody (Nb) for rapid, qualitative, and visual detection of ochratoxin A (OTA) in cereals was developed. On the basis of optimal assay conditions, the cut-off level of this method assessed visually was 5 μg/kg for OTA, and the final results were obtained within 20 min. This method was simple with no time-consuming cleanup procedure. Good accuracy and reproducibility were obtained in recovery experiments. Results of the Nb-based dot ELISA are in agreement with the ELISA kit, except for samples that were negative for OTA presence assessed through Nb-based dot ELISA but found positive through the ELISA kit. These results indicated that the developed method could be a useful on-site screening tool for rapid detection of OTA in cereals without special instrument.
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.
Ethyl carbamate (EC), a multi-site genotoxic carcinogen, exists in fermented food and beverages. However, the existing analytical methods need precise instrument, complex sample pretreatment, time-consuming, and high cost. Therefore, a disposable electrochemical biomimetic sensor was developed for fast and selective detection of EC based on reduced graphene oxide/screen-printed carbon composite electrode (rGO/SPCE). Firstly, the SPCE is modified with rGO by electrodeposition process that increased current signal and decreased the impedance of contact interface. Secondly, the OAP/rGO/SPCE biomimetic sensor was synthesized through electropolymerization by cyclic voltammograms in mixed solution of template of EC and monomer of O-aminophenol (OAP). The sensor specifically bound to EC quickly without sample pretreatment. A linear range was from 100 to 1300 nM, and a detection limit of 37 nM was achieved. The detection time is less than 5 min. The sensor possesses advantages include good chemical and mechanical stability, simplicity, low cost of preparation, and sensitive and label-free determination.
This paper reports the production of a novel magnetic nanocomposite based on multi-walled carbon nanotubes (MWCNTs) decorated with magnetic core–shell Fe3O4@SiO2 nanoparticles which were used to fabricate a modified carbon paste electrode (Fe3O4@SiO2/MWCNT-CPE). The Fe3O4@SiO2/MWCNT-CPE was investigated for the simultaneous determination of sunset yellow (SY) and tartrazine (TT) in 0.1 mol/L phosphate buffer solution (pH 6.0) using square wave voltammetry (SWV). The synthesized nanocomposite was characterized by transmission electron microscopy, scanning electron microscopy, energy dispersive spectroscopy and Fourier transform infrared spectroscopy. The proposed electrode exhibits linear ranges of 0.5–100 μmol/L SY and TT with detection limits of 0.05 and 0.04 μmol/L for SY and TT, respectively. The novel proposed voltammetric method was successfully applied in the simultaneous determination of SY and TT in food products, with results similar to those obtained using a HPLC method at 95 % confidence level.
Graphical Abstract A magnetic nanocomposite based on MWCNTs decorated with core–shell Fe3O4@SiO2 was prepared and showed good ability to distinguish the response of SY and TT
Laser-induced breakdown spectroscopy (LIBS) exhibits excellent ability for rapid analysis of potential toxics elements. In this study, LIBS was employed to measure the Cu concentration in contaminated Tegillarca granosa. A framework was carefully developed for sample’s preparation and LIBS acquisition. Univariate models based on Cu characteristic spectral lines were validated, but with unsatisfactory performance. Wavelengths’ loadings and weightings of partial least square (PLS) model exhibited the most uninformative background, while they were selected by the supervised general variable selection methods that showed success in near-infrared spectroscopy. Thus, a strategy for clustering variables by their similar characteristics was proposed to screen the informative wavelengths using the unsupervised Kohonen self-organizing map (SOM). The PLS and least square support vector machine (LSSVM) models were calibrated based on these clustered units using the optimized parameters for the SOM network. LSSVM model exhibited the best performance based on the C3?×?3(2,2) variables with correlation coefficient of prediction of 0.906, as well as root mean squared error of prediction of 19.62 mg kg?1. SOM could more effectively cluster wavelengths from the complex LIBS spectrum than general variable selections, which have been proven their success in near-infrared spectra but fail in the LIBS spectra. Results indicated LIBS coupled with SOM-LSSVM calibration method could be used to quantitatively evaluate the potential toxics element Cu concentration in shellfish Tegillarca granosa. This study can be a good reference for screening the informative variables and measurement of other constituents in LIBS spectra.
Copaiba oil is a non-timber forest product utilized in popular medicine, in addition to the pharmaceutical, cosmetic, and food industries. Brazil is a chief producer and supplier of this oil, and due to an increasing demand and elevated market value, it causes for this product to be subject to adulterations. Thus, the goal of this study was to develop a direct, fast, and simple method to quantify the purity of the oil extracted from Copaifera langsdorffii Desf., specifically, when the oil was adulterated with soybean oil. Quantification was performed utilizing a portable NIR spectrometer and partial least squares regression (PLSR). In the development and validation of the method, 53 samples of copaiba oil expressing a purity ranging from 50 up to 100% were used. Of the 53 samples, 15 were pure, 31 were adulterated with unused soybean oil, 6 were adulterated with soybean oil used for frying, and 1 adulterated with an unknown vegetable oil. Four models were developed and the best among them presented RMSEP = 1.5%, R2 = 0.991, and REP lower than 2.0% and expressed precision with deviations below 0.7%. These results indicate that the method is suitable for quality control analysis. In addition, it was accurate in the identification of samples with that were not present in the developed model.
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
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
Malic acid is an important fruit ripening indicator. Fruit industry losses every year due to non-availability of rapid technology for early detection of ripening of fruits. Therefore, nanosensor was developed for detection of malic acid concentrations in tomato at early stage of ripening before transport to the market. The enzyme NADP-malate dehydrogenase (Malic enzyme) was covalently immobilized on to screen printed carboxylated-multiwall carbon nanotubes working electrode using EDC-NHS chemistry. The enzyme electrode was characterized using scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. The immobilized enzyme/c-MWCNT electrode was used for amperometric determination of different concentrations of malic acid in tomato using differential pulse voltammogram (DPV) at scan rate of 100 mv/s. The limit of detection of malic acid was 0.01 mM. The nanosensor showed low Km (0.12 mM), less response time (2 min), high sensitivity (0.01 mM) and better storage stability 180 days at 4 °C compared to earlier reported malate biosensor. The nanosensor was also validated at different stages of ripening of tomato using enzymatic method.
