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BACKGROUND The determination of iodine in geochemical samples by inductively coupled plasma-mass spectrometry (ICP-MS) is treated mainly by closed sample melting, mixed acid solution, alkali fusion and semi-melting method. However, due to the complex existent morphology of iodine in soil and sediment samples, including periodate, iodate and iodide ions, and the first ionization energy of iodine being high as a halogen group element, there are problems such as incomplete dissolution, strong memory effect and poor precision during sample processing and measurement. OBJECTIVES To improve the determination of iodine in geochemical samples by ICP-MS. METHODS The samples were treated by sodium carbonate-zinc oxide semi-melting method, extracted with boiling water-ethanol, and separated by 732 cation exchange resin. Following this, iodine in the solution was determined by ICP-MS using an internal standard method. RESULTS The optimized detection limit of iodine was 0.045μg/g, the lower limit of detection was 0.15μg/g. The precision (RSD, n=12) and the accuracy (△logC) of the method were ≤5.93% and ≤0.01, respectively, which satisfied the analysis standards of geochemical survey sample. CONCLUSIONS This method meets the requirements of sample analysis for geochemical investigation, and can be used for the analysis of iodine in large quantities of soil and sediment samples.

The effects of pH on the foaming properties of egg white powder (EWP) improved by soy peptides (SP) were investigated. After adding various amounts of SP (3%, 6%, 9%, 12%) and adjusting the pH (4, 5.5, 7, 8.5), SP + EWP solutions were characterized according to their physicochemical properties, rheological behaviors, foaming performance, and microstructure. The results showed that 9% and 12% SP could improve the foaming properties of EWP. A more uniform size, greater foam elasticity, higher surface hydrophobicity and more flexible secondary structure were obtained when up to 9% SP was added. This facilitated interface adsorption, thereby significantly improving the foaming ability and foam stability. The SP + EWP solution had the largest expansion degree, most flexible structure, fastest interface adsorption rate, and highest elasticity of the foam film at pH 7, leading to the optimal foaming ability and foam stability. It was concluded that the optimal foaming performance was obtained by adding 9% SP to EWP under neutral pH conditions. [Display omitted] • SP and pH have significant effects on the foaming properties of EWP. • The foaming performance of SP + EWP is the best at pH7. • The secondary structure of egg white protein is significantly affected by SP and pH. • SP and pH have significant impacts on the rheological behaviors of foam. [ABSTRACT FROM AUTHOR]