For the first time, alginate polymer has been applied to prevent dyes from leaching out of colorimetric oxygen indicator films, which enable people to notice the presence of oxygen in the package in an economic and simple manner. The dye-based oxygen indicator film suffers from dye leaching upon contact with water. In this work, UV-activated visual oxygen indicator films were fabricated using thionine, glycerol, P25 TiO2, and zein as a redox dye, a sacrificial electron donor, UV-absorbing semiconducting photocatalyst, and an encapsulation polymer, respectively. When this zein-coated film was immersed in water for 24h, the dye leakage was as high as 80.80±0.45%. However, introduction of alginate (1.25%) as the coating polymer considerably diminished the dye leaching to only 5.80±0.06%. This is because the ion-binding ability of alginate could prevent the cation dye from leaching into water. This novel water-resistant UV-activated oxygen indicator was also successfully photo-bleached and regained colour fast in the presence of oxygen.

A nuclear magnetic resonance (NMR) method was developed to quantify cations in mineral water. The procedure was based on integration of signals from metal-ethylenediaminetetraacetic acid (EDTA) complexes at δ 2.70ppm for Mg2+ and δ 2.56ppm for Ca2+. The limits of detection were below 0.5mg/L. Lack of precision did not exceed 5%. Linearity was between 1 and 500mg/L. Correlation between NMR and a reference chromatographic method was significant (p<0.0001, R2=0.99). PLS models were also established to estimate Na+ and K+ contents. R2 was 0.85 and 0.83, respectively. Root mean square errors of cross validation (RMSECV) were 8.0mg/L and 1.9mg/L for Na+ and K+, respectively. The method was applied successfully for the analysis of 31 mineral water samples. This method is a useful tool for quantification of important cations in mineral water and might easily be adapted to other food matrices.

A new, efficient, and sensitive cloud point methodology was developed for preconcentration of trace quantities of cobalt and nickel in water and food samples prior to their determination by flame atomic absorption spectrometry (FAAS). The metals react with 2-(benzothiazolylazo)-4-nitrophenol (BTANP) at pH 7.0 and micelle-mediated extraction using the nonionic surfactant Triton X-114 medium. The surfactant-rich phase was diluted with acidified methanol and the cobalt and nickel content was determined by FAAS. The optimum conditions (e.g. pH, reagent and surfactant concentrations, temperature and centrifugation times) were evaluated and optimized. The proposed CPE method showed linear calibration within the ranges 5.0–100 and 5.0–150 ng mL⁻¹ of cobalt and nickel, respectively, and the limits of detection of the method was 1.4 and 1.0 ng mL⁻¹ of cobalt and nickel, respectively. The interference effect of some cations and anions was also studied. The method was applied to the determination of both metals in water and food samples with a recovery from the spiked water samples in the range of 95–102%. The validation of the procedure was carried out by analysis of a certified reference material.

A simple, rapid, sensitive and environmentally friendly separation and preconcentration procedure, based on the carrier element free coprecipitation (CEFC) of Cu(II) and Cd(II) ions by using an organic coprecipitant, 2-{[4-(4-fluorophenyl)-5-sulphanyl-4H-1,2,4-triazol-3-yl]methyl}-4-{[(4-fluorophenyl) methylene]amino}-5-(4-methylphenyl)-2,4-dihydro-3H-1,2,4-triazol-3-one (MEFMAT) was developed. The analyte ions were determined by flame atomic absorption spectrometric (FAAS) determinations. The optimum conditions for the coprecipitation process were investigated on several commonly tested experimental parameters such as pH of the solution, amount of MEFMAT, sample volume, standing time, centrifugation rate and time. The influences of some anions, cations and transition metals on the recoveries of analyte ions were also investigated, and no considerable interference was observed. The preconcentration factor was found to be 50. The detection limits for Cu(II) and Cd(II) ions based on the three times the standard deviation of the blanks (N:10) were found to be 1.49 and 0.45μgL⁻¹, respectively. The relative standard deviations were found to be lower than 3.5% for both analyte ions. The method was validated by analyzing two certified reference materials (CRM-TMDW-500 Drinking Water and CRM-SA-C Sandy Soil C) and spike tests. The procedure was successfully applied to sea water and stream water as liquid samples and tobacco, hazelnut and black tea as solid samples.

A procedure for separation and enrichment of Cd(II) and Ni(II) ions based upon carrier element-free coprecipitation by using an organic coprecipitant, 2-{4-[2-(1H-Indol-3-yl)ethyl]-3-(4-methylbenzyl)-5-oxo-4,5-dihydro-1H-1,2,4-triazol-1-yl}-N′-(3-fluoro-phenylmethyliden) acetohydrazide, prior to their flame atomic absorption spectrometric detections has been developed. The effects of varied experimental conditions on the performance of the developed method such as pH, sample volume, amount of coprecipitating agent, etc. were evaluated in detail on the recovery of analyte ions, and the influences of some anions and cations were investigated. The limits of detection for Cd(II) and Ni(II) ions based on three times the standard deviation of the blanks (N: 10) were obtained as 0.70 μg L⁻¹ and 1.21 μg L⁻¹, respectively. The accuracy of the method was tested by analyzing a certified reference material and by spike tests. The method was applied to determine the levels of cadmium and nickel in stream and sea water, rice, red lentil, and wheat samples.

A new biodegradable polyhydroxybutyrate diethanol amine (PHB-DEA) polymer was used as adsorbent for the sensitive and selective separation, preconcentration and determination of Pb(II), Cd(II) and Zn(II) by using atomic absorption spectrometry. Diethyl dithiocarbamate was used as chelating reagent. Analytical parameters such as pH, eluent type and its volume, flow rates of sample solution, ligand amount, sample volume were optimized. Effects of some cations, anions and transition metal ions were also investigated. Enrichment factor and relative standard deviation were found to be 100 and 3%, respectively. The limits of detection based on three times standard deviation of blanks (N=21) were found 1.05μgL−1 for Pb(II), 0.42μgL−1 for Cd(II) and 0.13μgL−1 for Zn(II). Limits of quantification (10s, N=21) were found 3.47μgL−1 for Pb(II), 1.39μgL−1 for Cd(II) and 0.43μgL−1 for Zn(II). Accuracy evaluation of the method was confirmed with analyses of certified reference materials (NIST SRM 1515 Apple leaves, IAEA 336 Lichen, GBW 07605 Tea). Optimized method was applied to tap water and food samples after microwave digestion method. Cadmium and lead values in some samples were found higher than legal limits.

A newly synthesized polystyrene-g-polyoleic acid-g-polyethylene glycol graft copolymer (PoleS-PEG) was used as adsorbent in the solid phase microextraction of selenium ions by using electrothermal atomic absorption spectrometry (ETAAS). Neodymium magnet was used for separation of analyte ions. Various analytical parameters such as pH, adsorbent amount, mixing time, eluent solution, sample volume, etc. were optimized. The matrix effects of some cations and anions were also studied. The capacity of the adsorbent was found 11.5 mg g−1. The preconcentration factor was found to be 50. The detection limit (LOD) and quantification limit (LOQ) were found 6.06 ng L−1 and 20 ng L−1, respectively. The calibration curve was linear in the range of 0.02–4.0 μg L−1. Relative standard deviation was found 3.2%. The accuracy of the method was provided by using standard reference materials. The optimized method was successfully applied to natural water and food samples.

A simple and green ultrasound liquid-liquid microextraction method based on low viscous hydrophobic deep eutectic solvent (ULLME-LV-HDES) was proposed for the preconcentration and separation of selenium prior to HG-AAS detection. Six different DESs were prepared for the extraction of selenium. Quercetin was used complexing agent for Se(IV) ions. Various analytical parameters such as pH, quercetin amount, DES type and its volume, sonication time, sample volume were optimized. Tolerance limits of anion, cation and transition metal ions were studied. Preconcentration and enhancement factor were found 62.5 and 121. Under the optimum conditions, limit of detection was found 0.25 ng L⁻¹ with calibration range of 0.8–120 ng L⁻¹. Relative standard deviation was found 3.2%. The accuracy of the method was confirmed with certified reference materials (NIST 1567a Wheat flour and NIST 1548a Typical diet). Finally, the developed method was successfully applied to food and water samples.