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This study aimed optimizes the inductively coupled plasma–atomic emission spectrometry (ICP-AES) conditions for the determination of macro and microelements in the flowers and leaves of Trifolium species. After the optimization of instrumental parameters, plasma robustness was achieved under the following conditions: RF power 1350 W, nebulizer flow rate 0.5 L min−1, coolant gas flow rate 12 L min−1, auxiliary gas flow rate 0.5 L min−1, flush pump rate 100 rpm, analysis pump rate 50 rpm, sample flow 0.5 mL min−1, and sample uptake delay 30 s. The limits of detection (LOD) and limits of quantification (LOQs) were lower than literature values. The most abundant microelement in leaves is Ca, followed by K, Mg, P, and Na, and in flowers was K, followed by Ca, P, Mg, and Na. The average contents of microelements decreased in the orders S > Fe > Si > Al > Zn > Mn > Cu > Ni > Co > Pb > Cr > As > Cd for flowers and S > Fe > Si > Mn > Al > Zn > Cu > Ni > Co > Pb > Cr > As > Cd for leaves. Chemometrics were used for grouping samples based upon the elemental contents. [ABSTRACT FROM AUTHOR]

A simple, rapid, sensitive and selective kinetic spectrophotometric method for determination of Fe(III) traces was elaborated in this paper. It is based on the catalytic effect of Fe(III) ions on oxidation of potassium salt of disulphonated hydroquinone (K2S2Hy) by hydrogen peroxide in acidic media, at a constant ionic strength. At the working temperature of 20°C and the wavelength of 450.0 nm, optimal conditions for determination of iron were found so that iron (III) can be determined by the proposed method in the concentration range of 1.87 to 18.7 ng cm-3. Corresponding RSD values were determined to be in the range 4.22 to 10.33 %. The limit of detection (LOD) calculated in two ways was found to be 1.07 ng cm-3 i.e. 1.11 ng cm-3 Fe(III). In order to assess the selectivity of the method effects of different ions on the reaction rate were also determined. It was found that presence of oxalates and citrates in the w/w ratio to Fe(III) 1:1 under selected experimental conditions interferes with determination of iron. Then the method was applied for determination of Fe(III) traces in white radish juice. The results agreed well with those obtained by atomic absorption spectrometry.

A kinetic spectrophotometric method for determining residues of insecticide diflubenzuron 1(4-chlorphenyl)-3-(2,6-diflubenzoyl)urea (DFB) has been developed and validated. Kinetic method was based on the inhibitory effect of DFB on the oxidation reaction of sulfanilic acid (SA) by hydrogen peroxide in the presence of Co2+ ions in a phosphate buffer, which was monitored at 370 nm. DFB can be measured in the concentration interval 0.102 – 3.40 μg mL-1 and 3.40 – 23.80 μg mL-1. The detection and quantification limits of the method were calculated according to the 3σ criteria and found to be 0.077 μg mL-1 and 0.254 μg Ml-1, respectively. The relative standard deviations for five replicate determinations of 0.102, 1.70 and 3.40 μg mL-1 DFB were 2.08, 1.22 and 1.21 %, respectively, for the first concentration interval, and the recovery percentage values were from 94.12 to 97.35 %. HPLC method was used as a parallel method to verify results of the kinetic method. The kinetic method was successfully applied to determine diflubenzuron concentrations in spiked water and baby food samples after solid phase extraction of the samples. The F and t values at 95% confidence level are lower than the theoretical ones, confirming agreement of the developed and the HPLC method. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 172061]

BACKGROUND An inductively coupled plasma-optical emission spectrometry method for the speedy simultaneous detection of 19 elements in edible nuts (walnuts: Juglans nigra; almonds: Prunus dulcis; hazelnuts: Corylus avellana; Brazil nuts: Bertholletia excelsa; cashews: Anacardium occidentalle; pistachios: Pistacia vera; and peanuts: Arachis hypogaea) available on the Serbian markets, was optimized and validated through the selection of instrumental parameters and analytical lines free from spectral interference and with the lowest matrix effects. RESULTS The analysed macro-elements were present in the following descending order: Na > Mg > Ca > K. Of all the trace elements, the tested samples showed the highest content of Fe. The micro-element Se was detected in all the samples of nuts. The toxic elements As, Cd and Pb were either not detected or the contents were below the limit of detection. One-way analysis of variance, Student's t-test, Tukey's HSD post hoc test and hierarchical agglomerative cluster analysis were applied in the statistical analysis of the results. CONCLUSION Based on the detected content of analysed elements it can be concluded that nuts may be a good additional source of minerals as micronutrients. © 2014 Society of Chemical Industry [ABSTRACT FROM AUTHOR]