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A new method for the rapid enrichment and highly sensitive determination of nickel ion has been developed by using a nanofiber-composite membrane filter, which was fabricated by stacking a nanofibrous material made of nylon 6 over a water-permeable membrane filter. The noncharged nickel-α-furil dioxime complex was adsorbed on a nanofibrous layer of the membrane filter under significantly higher flow rates than those used for conventional solid-phase extraction techniques. Highly sensitive determinations with detection limits at sub-parts per billion levels were achieved by enrichment from 50 mL of the complex solution, and the enrichment was completed within 3 min. The color that was developed on the membrane filter was successfully subjected to visual colorimetric analysis and quantitative determination by solid-phase spectrophotometry. In addition, colorimetric determination was feasible with a handheld spectrometer after elution of the colored agent with 50 μL of acetone. This combination of rapid enrichment and spectrometric measurement in a small-volume sample provides a useful analytical method suitable for on-site analysis, which requires neither expensive instruments nor high laboratory skills.

Herein, we determined the contents of Cu(I), Cu(II), and hydrophobic Cu in natural water using on-site sample treatment, solid-phase extraction (SPE), and inductively coupled plasma mass spectrometry (ICP-MS) analysis. To prevent Cu species changes in the sampling, filtering and preconditioning steps were performed in a closed system using plastic syringes and a disposable membrane filter. Bathocuproin disulfonate (BCS) and ethylenediaminetetraacetic acid (EDTA) were selected as a Cu(I)-selective complexing agent and a Cu(II) masking agent, respectively, whereas ascorbic acid (AA) was used to reduce Cu(II) to Cu(I). Pre-conditioned samples were passed through a hydrophobic SPE column, and the retained Cu species were eluted with ethanol. Subsequently, the eluate was concentrated, and the residue was re-dissolved in 2 M HNO 3 and subjected to ICP-MS analysis. No artificial changes of Cu(I) and Cu(II) species were observed at any time, with the analytical detection limit of total Cu and the blank value equaling 0.0008 and 0.0025 μg kg -1 , respectively. The developed method was applied to real estuarine, riverine, and seawater samples collected in Tokushima prefecture, Japan.

This study reports on a headspace gas chromatographic method (HS-GC) for the determination of formaldehyde in sanitary napkin samples. The method is based on the reaction of formaldehyde and sodium borohydride in a concentrated potassium carbonate solution (824 g/L), in which formaldehyde is quantitatively converted to methanol at 105°C in 45 min. The methanol from the conversion is determined by HS-GC. The repeatability of the method had a relative standard deviation of less than 4.5%; the limit of quantification (LOQ) was 1.17 µg, and the recovery ranged from 96.8 - 106%. The present method is simple, rapid, and accurate. It is suitable for use in the batch testing for product quality control of tissue papers during the manufacturing process and in analysis of point-of-sale samples from commercial markets.