Zinc In Food Samples Research Articles

Determinations of Cadmium, Tin, Copper, Iron and Zinc in Food Samples by Electrothermal and Flame Atomic Absorption Spectrometries

Cadmium, tin, iron, copper, and zinc in tea, rice, and liver samples, and standard reference materials (IRMM 804 Rice Flour, GBW 10010 Rice, Bovine Liver1577c and GBW 07605 Tea Leaves) were determined by using electrothermal and flame atomic absorption spectrometries. Cd and Sn in sample solutions were determined with electrothermal atomic absorption spectrometry by using palladium (Pd) as a matrix modifier. Pyrolysis and atomization temperatures and pyrolysis times of Cd and Sn in sample solutions were optimized in the absence or presence of Pd. Pyrolysis temperatures of Cd and Sn found in the presence of Pd were 800°C and 1200°C, respectively. Iron, Cu, and Zn in samples were determined by flame atomic absorption spectrometry. The accuracy and precision of the method were validated by determining elements in standard reference materials. Limits of detection for Sn, Cd, Fe, Cu, and Zn were found as 0.66, 0.26, 2.0, 1.9, and 1.2 μg/L, respectively. Concentrations of elements found in samples were compared with maximum values reported by World Health Organization (WHO) and other studies.

Violuric acid carbon dots as a highly fluorescence probe for ultrasensitive determination of Zn (II) in tomato paste

Zinc is an essential metal since it plays an important role in biological systems, therefore, determination of zinc in food samples is important. Violuric acid was used to prepare highly fluorescent carbon dots (CDs), when it irradiated with ultraviolet radiation at 365 nm, a strong violet fluorescence was observed which caused by the increased amount of nitrogen in the CD structure, which were then successfully used for sensing zinc ion based on quenching of fluorescence. Violuric acid's hydrothermal carbonization reaction's temperature and time were simply optimized for better-quality performance of the CDs as-synthesized. The probe was characterized by HRTEM, SEM, XRD, EDX, fluorescence, UV–Visible absorption spectrophotometry, and FTIR. With a lower LOD 0.32 nM, the developed approach demonstrates an exceptional sensitivity and good selective response to the Zn2+ at 25℃. Compared to the results from ICP, the sensor was successfully used for determination of Zn2+ ions in tomato paste samples.

Optimisation and Evaluation of Zinc in Food Samples by Cloud Point Extraction and Spectrophotometric Detection

The cloud point extraction (CPE) method was developed to determine the zinc prior to Ultraviolet-visible (UV-Vis) spectrophotometry detection. Triton X-100 was applied as extractant based on the complexation reaction of Zn(II) ions with ethylenediaminetetraacetic acid (EDTA). Under optimal conditions, the CPE was used to determine the concentration of zinc in canned food samples. The amounts of zinc found in the food samples were in the range of 0.005-0.007 mg/L with relative standard deviation (RSD) of < 8 %. This confirmed that the proposed CPE method is suitable for the determination of zinc in food samples, indicating the concentration of zinc was within the permissible limit.

MICROWAVE-ASSISTED LIQUID PHASE MICROEXTRACTION FOLLOWED WITH FLAME ATOMIC ABSORPTION SPECTROMETRY FOR TRACE DETERMINATION OF ZINC IN FOOD SAMPLES

In this work, microwave-assisted liquid phase microextraction (MA-LPME) was followed by flame atomic absorption spectrometry for determination of zinc in food samples. Zinc was complexed with a chelating agent to form hydrophobic species.1-hexyl-3-methylimidazolium hexafluorophosphate ([Hmim][PF6]) ionic liquid (IL) was used as environmentally-friendly extraction solvent. In order to disperse the extraction phase into the sample solution and improve the extraction efficiency, microwave irradiation was used as a disperser agent. The heating effect of microwave irradiation makes the ionic liquid dissolved and dispersed through the sample, which significantly improves the speed and efficiency of extraction. After extraction process, sample solution was centrifuged and the settled phase was diluted and introduced to flame atomic absorption spectrometry by conventional aspiration. Various parameters including amount of ionic liquid, microwave power, irradiation time, pH, amount of chelating agent and salt amount were studied and optimized. At optimized condition, a limit of detection (LOD) of 1.5 ng mL-1, a linear range of 5-32 ng mL-1 and a RSD of 4.3% were obtained. Finally, the developed protocol was utilized for determination of zinc in food samples.

Comparison of Wet and Microwave Digestion Methods for the Determination of Copper, Iron and Zinc in Some Food Samples by FAAS

In this study, the effects of wet and microwave digestion methods for the determination of cupper (Cu), iron (Fe), and zinc (Zn) in standard reference materials (SRMs) and food samples by using flame atomic absorption spectrometry (FAAS) were investigated. HCl, HNO3, and HNO3 + H2O2 mixture were applied to the digestions of the SRMs (IRMM-804 rice flour, GBW 10010 rice, GBW 10011 wheat flour, 1567a wheat flour and 1571 orchard leaves) for optimization and validation of the method by using wet and microwave digestion systems. Concentrations of Cu, Fe and Zn in SRMs were determined by FAAS, and the lowest percent relative errors of analytes (from −2.5 % to +3.0 %) were obtained by using HNO3 + H2O2 mixture in the microwave digestion. Limit of detection (LOD) and limit of quantification (LOQ) values for analytes obtained by using HNO3 + H2O2 mixture in the microwave digestion were 14.5 and 48.3 μg L−1 for Cu, 16.4 and 54.6 μg L−1 for Fe, and 10.8 and 36.0 μg L−1 for Zn, respectively. The concentrations of Cu, Fe and Zn in food samples such as wheat flour, corn flour, rice flour and tahini were determined by FAAS using the HNO3 + H2O2 mixture in both wet and microwave digestion systems. It was observed that the results obtained with microwave digestion were higher than those of wet digestion. The concentrations of Cu, Fe and Zn in samples found by microwave digestion were compared with the maximum permissible values given in the Turkish standards, regulations and some literature values.

Flame atomic absorption spectrometric (FAAS) determination of copper, iron and zinc in food samples after solid-phase extraction on Schiff base-modified duolite XAD 761

The present study involves the development of solid-phase extraction (SPE) procedure for the preconcentration of trace amounts of copper (Cu2+), iron (Fe3+) and zinc (Zn2+) ions on duolite XAD 761 modified by bis(2-hydroxyacetophenone)-2,2-dimethyl-1,3-propanediimine(BHAPDMPDI). The complexation between the metal ions and the proposed ligand was investigated potentiometrically. The metal ions retained on the sorbent were quantitatively determined via complexation with BHAPDMPDI. The complexed metal ions were efficiently eluted using 6mL of 4molL−1 nitric acid in acetone. The influences of the analytical parameters, including pH, amounts of the ligand and the solid phase, eluent conditions and sample volume, on the recoveries of the metal ions were optimized. Using the optimized parameters, the linear response of the SPE method for Cu2+, Zn2+ and Fe3+ ions were in the ranges of 0.01–0.34, 0.01–0.28 and 0.02–0.31μgmL−1, respectively, and the detection limits for Cu2+, Zn2+ and Fe3+ ions were 1.8, 1.6 and 2.4μgmL−1, respectively. The proposed method exhibits a preconcentration factor of 208 for all of the ions studied and an enhancement factor for Cu2+, Fe3+ and Zn2+ ions of 34, 28 and 38, respectively. The presented results demonstrate the successful application of the proposed method for the determination of these metal ions in some real samples with high recoveries (> 95%) and reasonable relative standard deviation (RDS <5%).

Pre-concentration procedure for determination of copper and zinc in food samples by sequential multi-element flame atomic absorption spectrometry

In this paper is proposed a simultaneous pre-concentration procedure using cloud point extraction for the determination of copper and zinc in food samples employing sequential multi-element flame atomic absorption spectrometry (FS-FAAS). The reagent used is 1-(2-pyridylazo)-2-naphthol (PAN) and the micellar phase is obtained using the non-ionic surfactant octylphenoxypolyethoxyethanol (Triton X-114) and centrifugation. The optimization step was performed using Box–Behnken design for three factors: solution pH, reagent concentration and buffer concentration. A multiple response function was established in order to get an experimental condition for simultaneous extraction of copper and zinc. Under the optimized experimental conditions, the method allows the determination of copper with a limit of detection (3 σ b/ S, LOD) of 0.1 μg L −1, precision expressed as relative standard deviation (R.S.D.) of 2.1 and 1.3% ( N = 10), for copper concentrations of 10 and 50 μg L −1, respectively. Zinc is determined with a LOD of 0.15 μg L −1 and precision as R.S.D. of 2.7 and 1.7% for concentrations of 10 and 50 μg L −1, respectively. The enhancement factors obtained were 36 and 32 for copper and zinc, respectively. The accuracy was assessed by analysis of certified reference materials, namely, SRM 1567a – Wheat Flour and SRM 8433 – Corn Bran from National Institute of Standards & Technology and BCR 189-wholemeal flour from Institute of Reference Materials and Measurements. The method was applied to the determination of copper and zinc in oats, powdered chocolate, corn flour and wheat flour samples. The copper content in the samples analyzed varied from 1.14 to 3.28 μg g −1 and zinc from 8.7 to 22.9 μg g −1.

Flow injection method for the fluorimetric determination of Zn with 8-(benzenesulphonamido) quinoline

The development of a fluorimetric method for the determination of zinc, based on the fluorescence of the zinc-8-(benzenesulphonamido) quinoline chelate in a micellar medium of sodium dodecylsulfate, is reported. The detection limit is 0.2 μg l–1, the working range is 0.5–700 μg l−1, and the sample throughput is 145 h−1. The method was evaluated for the determination of zinc in food samples.

Spectrofluorimetric determination of zinc in milk samples with tyrosine

A new method for the determination of zinc, based on the fluorescence of the zinc–tyrosine chelate in a weak alkaline medium, has been developed. The method allows the determination of 0.65–32.5 µg ml–1 of zinc and is relatively free from interferences. The method has been applied in the determination of zinc in food samples with satisfactory results.

Determination of zinc in foods by fluorescence spectroscopy in micellar media

The effect of cationic [cetyltrimethylammonium bromide (CTAB), Zephiramine], non-ionic (Triton X-100, Brij-35) and anionic (sodium lauryl sulphate) surfactant micelles on the fluorescence intensity of the zinc 5,7-dichloro-2-methylquinolin-8-ol chelate is described. In Brij-35 or CTAB micellar media, the fluorescence is about 25 times greater than that obtained in ethanol-water. The relationship between fluorescence intensity and experimental variables was studied in order to develop a procedure for the fluorimetric determination of zinc. Linear calibration graphs were obtained in the ranges 3–100 and 50–400 ng Zn ml −1. The detection limit is 3 ng ml −1. The method was successfully applied to the determination of zinc in food samples and drinking waters.