セレン化ヒ素高屈折率媒質による水溶液赤外全反射吸収スペクトル法

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Usually, KRS-5, the mixed crystal of thallium iodide and bromide, has been used for infrared ATR (Attenuated Total Reflection) measurements as dielectric of high refractive index, but it is difficult to apply repeatedly in aqueous solution and is easily corroded by acidic and basic solutions. Because newly developed material i. e. As2Se3 has such excellent properties as water-, acid-, alkali-proof and chemical resistance, it enables to measure spectra of wide pH range that was usually difficult by KRS-5. The equipment was IR-S type infrared spectrophotometer provided with ATR-6 type multiple ATR attachment of Japan Spectroscopic Co., Ltd. make. The refractivity (nD) of As2Se3 (named SH-1) utilized as the new prism is 2.8, the number of multiple reflections is 7 and angle of incidence for samples is always 45°. Though the energy loss of the prism was about 50% in all spectral region and there are the weak bands in 3600 and 1570 cm-1 (Fig. la), the measurements by it were possible in 4000800 cm-1. The spectrum of water using it showed that it was possible to measure spectra of aqueous solutions in above region except 3200 and 1650 cm-1 regions where strong water bands existed (Fig. 1b). Applications for measurements of aqueous solutions with wide pH range by this method were mainly shown for the product solutions in initial condensation reaction of such thermosetting resins as resorcin formaldehyde, phenol formaldehyde and urea formaldehyde resin. As these reactions are proceeded in water and intermediate products in these systems are too unstable to take out from the mixtures for measurement of these spectra, it is very difficult to measure by the conventional infrared method in spite of the strong demands for infrared analysis. Therefore, analysis for these samples were generally done through determination of formaldehyde by such wet methods as hydroxylamine-hydrochloride method or potassium cyanide method up to the present. Now, however, these reactions can be analyzed easily by this new method. For example, the spectra of the aqueous solutions in initial condensation reaction of resorcin and formaldehyde showed remarkable changes with reaction time in the regions of 15001400, 12001100, 11001050, 1080, 980960 cm-1 (Fig. 2), and especially the bands of 1145 and 960 cm-1 which represent resorcin contents, were useful for the analysis. The calibration curves of them were found to be liner (Fig. 3). The changes of spectra of aqueous solutions with reaction time measured by this method in initial condensation reactions of phenol and formaldehyde or urea and formaldehyde were also shown (Fig. 4 and Fig. 5). As the other applied examples for aqueous solutions of wide pH range, the spectra of NaH2PO4 (pH 4.4), Na2HPO4 (9.1), Na3PO4 (12.1), NaNO3 (5.7), NaNO2 (8.0), β-naphthalene-sulfonic-acid (1.2) and ethylene vinyl acetate emulsion copolymer were shown (Fig. 6Fig. 9).
社団法人日本分析化学会の論文

セレン化ヒ素高屈折率媒質による水溶液赤外全反射吸収スペクトル法

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