Nickel In Food Samples Research Articles

A novel post-synthetic modification of magnetic MIL-101(Cr) metal–organic framework with 1,8-diaminonaphthalene chelator and its utilization for separation/determination of cadmium and nickel in food samples

A novel post-synthetic modification of magnetic MIL-101(Cr) metal–organic framework with 1,8-diaminonaphthalene chelator and its utilization for separation/determination of cadmium and nickel in food samples

Cold-Induced Aggregation Microextraction Technique based on Ionic Liquid for Preconcentration and Determination of Nickel in Food Samples

The determination of nickel in food samples and well water using cold induced aggregation microextraction combined UV-Vis spectrophotometry is described. The extraction of nickel was performed in the presence of dimethylglyoxime (DMG) as the complexing agent. In this method, sodium hexafluorophosphate (NaPF6) was added to the sample solution containing small amounts of 1-hexyl-3-methylimidazolium hexafluorophosphate [Hmim][PF6] as extraction solvent. Parameters governing the extraction efficiency such as amount of ionic liquid, pH, temperature and ionic strength were optimized. The applicability of the technique was evaluated by the determination of trace nickel in different types of vegetables. Under the optimum conditions, the calibration curve was linear in the concentration range 8-200 ng mL-1 with correlation coefficient (r2) of 0.9996. The limit of detection (LOD) of 0.47 ng mL-1 and enhancement factor of 186 were obtained for nickel. The relative standard deviation (RSD) was 3.7% for 40 ng L-1 nickel (n = 10).

Determination of Nickel in Food Samples by Flame Atomic Absorption Spectroscopy after Preconcentration and Microextraction Based Ionic Liquids Using Full Factorial and Central Composite Design

In this research, a microextraction technique based on ionic liquids (ILs) termed in situ solvent formation microextraction (ISFME) was used for determination of nickel in solutions. 1-(2-pyridylazo)-2-naphtol (PAN) was chosen as a complexing agent. After preconcentration, the settled IL-phase was dissolved in 50 μL of ethanol and aspirated into the flame atomic absorption spectrometer (FAAS) using a home-made microsample introduction system. Injection of 50 μL volumes of analyte into an air-acetylene flame provided very sensitive spike-like and reproducible signals. ISFME is based on phase separation phenomenon of ionic liquids in aqueous solutions. This method is simple and rapid for extraction and preconcentration of metal ions from food samples and can be applied for the sample solutions containing very high concentrations of salt. Furthermore, this technique is much safer in comparison with the organic solvent extraction because of using ionic liquid. The effective parameters such as amount of IL, salt effect, concentration of the chelating agent and ion pairing agent were inspected by a full factorial design to identify important parameters and their interactions. Next, a central composite design was applied to obtain optimum point of the important parameters. Under the optimum conditions, the calibration graph was linear over the range of 2 to 80 ng/mL. The limit of detection and relative standard deviation (n= 6) were 0.6 ng/mL and 2%, respectively.

Simultaneous coprecipitation of lead, cobalt, copper, cadmium, iron and nickel in food samples with zirconium(IV) hydroxide prior to their flame atomic absorption spectrometric determination

A simple and new coprecipitation procedure is developed for the determination of trace quantities of heavy metals (lead, cobalt, copper, cadmium, iron and nickel) in natural water and food samples. Analyte ions were coprecipitated by using zirconium(IV) hydroxide. The determination of metal levels was performed by flame atomic absorption spectrometry (FAAS). The influences of analytical parameters including pH, amount of zirconium(IV), sample volume, etc. were investigated on the recoveries of analyte ions. The effects of possible matrix ions were also examined. The recoveries of the analyte ions were in the range of 95–100%. Preconcentration factor was calculated as 25. The detection limits for the analyte ions based on 3 sigma (n=21) were in the range of 0.27–2.50μgL−1. Relative standard deviation was found to be lower than 8%. The validation of the presented coprecipitation procedure was performed by the analysis certified reference materials (GBW 07605 Tea and LGC 6010 Hard drinking water). The procedure was successfully applied to natural waters and food samples like coffee, fish, tobacco, black and green tea.

Automatic determination of nickel in foods by flame atomic absorption spectrometry

A new sensitive and low cost flow injection method that combines acid extraction, preconcentration and flame atomic absorption spectrometric determination of nickel in food samples at μg/g levels is described. The dynamic acid extraction step was carried out by using a continuous ultrasound-assisted extraction system. The acid extract was preconcentrated on-line on a minicolumn packed with a chelating resin (Serdolit Che, with iminodiacetic groups) and nickel was eluted with diluted hydrochloric acid, being continuously monitored by flame atomic absorption spectrometry. An experimental design (Plackett-Burman 26×3/16) is used to optimise the methodology proposed. The method allowed a total sampling frequency of 13–28 samples per hour. Good precision of the whole procedure (1.9–3.6% expressed as relative standard deviation) and a detection limit of 0.12μg/g, for 60mg of sample were achieved. The method was successfully applied to the determination of trace amounts of nickel in food samples.

Determination of cobalt, copper and nickel in food samples after pre-concentration on a new pyrocatechol-functionalized polyurethane foam sorbent

Polyurethane foam functionalized with pyrocatechol by covalent coupling through –N C– group, is applied to an on-line pre-concentration system for cobalt, copper and nickel determination in food samples. The preparation of the packing material involved the reaction of 2,3-dihydroxybenzaldehyde with the amino groups of polyurethane foam. Metal ions were sorbed in the minicolumn, from which it could be eluted with acid solutions directly to the nebulizer-burner system of the flame atomic absorption spectrometer (FAAS). Under the optimum conditions, the enrichment factors obtained were 55, 42 and 54, for cobalt, copper and nickel, respectively, if used 180 s pre-concentration time. The detection limits of the proposed procedure were 0.5 (Co), 0.4 (Cu) and 0.6 (Ni) μg L −1. The method was applied to determination of the metals in spinach, rice flour, corn flour and black tea samples. The accuracy of the developed procedure was evaluated by analysis of the certified reference material NIST 1570a Spinach Leaves.

On-Line Preconcentration and Determination of Cadmium, Cobalt and Nickel in Food Samples by Flame Atomic Absorption Spectrometry Using a New Functionalized Resin

A new chelating sorbent has been developed using Amberlite XAD-2 resin anchored with pyrocatechol through the –CH2– group. This sorbent, characterised by elemental analysis and infrared (IR) spectra, was used as a packing material for a minicolumn in an on-line preconcentration system for cadmium, cobalt and nickel determination. Metal ions were sorbed in the minicolumn, from which it could be eluted directly to the nebulizer-burner system of the flame atomic absorption spectrometer (FAAS). Metals can be eluted from the minicolumn with 0.50 mol L−1 HCl or HNO3. The enrichment factors were 22 (Cd), 23 (Co) and 25 (Ni), for 60 s preconcentration time, and 44 (Cd), 40 (Co) and 48 (Ni), if 180 s preconcentration time was used. Under the optimum conditions, the procedure allowed the determination of cadmium, cobalt and nickel with detection limits of 0.27, 0.59 and 1.29 µg L−1, respectively, when preconcentration periods of 180 s were used. The accuracy of the procedure was sufficient and evaluated by analysing certified reference materials. The method was applied to the analysis of food samples (black tea and rice flour).

DETERMINATION OF NICKEL IN FOOD BY SPECTROPHOTOMETRY WITH o-CARBOXYLBENZENEDIAZO-AMINOAZOBENZENE

ABSTRACT A highly sensitive and relatively interference-free spectrophotometric method for the determination of nickel is described. The method is based on color reaction between o-Carboxylbenzenediazoaminoazobenzene (o-CDAA) and nickel(II). The absorbance (at λmax = 540 nm) is linear up to 0.24 µg ml−1 of nickel(II) in borax buffer solution (pH = 10) with a repeatability(RSD) of 1.0% at a concentration of 0.2 µg ml−1. The molar absorptivity of Ni-o-CDAA-TritonX-100 is 3.3 × 105 l mol−1 cm−1, its limit of quantification and the limit of detection were found to be 0.74 and 0.22 ng ml−1 respectively, it gives a better sensitivity than other reagents published. The influence of reaction variables and the effect of interfering ions are reported; most of metal ions in food can be tolerated in considerable amounts. Only zinc may interfere with determination of trace nickel, but it can be eliminated by using a prior separation with sulfhydryl dextran gel adsorbent easily. Moreover, the synthesis of derivatives of benzenediazoaminoazobenzene and sulfhydryl dextran gel and the conditions of color reaction were studied in detail. The proposed method is very sensitive, simple and rapid, it has been used for the determination of nickel in food samples with satisfactory results.