Development of an Automatic pH Adjustment Instrument for the Preparation of Analytical Samples Prior to Solid Phase Extraction

• Published in: Analytical Sciences Vol. 36; no. 5; pp. 621 - 626
• Main Authors: ZHU, Yanbei, NISHIGORI, Sayaka, SHIMURA, Nobuaki, NARA, Tomio, FUJIMORI, Eiji
• Format: Journal Article
• Language: English
• Published: Singapore The Japan Society for Analytical Chemistry 10.05.2020; Springer Nature Singapore; Japan Science and Technology Agency
• Subjects: Ammonia; Analytical Chemistry; Automatic pH adjustment instrument; Chemical analysis; Chemistry; Light sources; Luminous intensity; nebulization; pH effects; pH indicating reagent; Pretreatment; Reagents; Real time; Seawater; solid phase extraction; Solid phases; spectrometer; Trace elements; Water analysis; Wavelength; Automatic pH adjustment instrument; pH indicating reagent; solid phase extraction; spectrometer; nebulization
• ISSN: 0910-6340; 1348-2246
• DOI: 10.2116/analsci.19SBN03

An automatic pH adjustment instrument was developed for the preparation of analytical samples prior to solid phase extraction, which is widely used as a pretreatment technique for the separation of sample matrixes and preconcentration of elements for analysis. Real-time monitoring of the sample pH condition was performed by observing the light signal intensity of the pH-sensitive wavelength of the pH indicating reagent. A light of pH-insensitive wavelength was selected as the reference light to cancel the signal intensity variation of the pH-sensitive light due to the difference of pH indicating reagent concentration, possible difference in transparency of sample vessels, and minute fluctuation of the light source. The pH condition was elevated by automatic addition of ammonia solution using a nebulizer in the flow line of which an electromagnetic valve was equipped. Open and close operation of the electromagnetic valve was controlled based on the difference between the real-time pH condition and the target pH condition. The effectiveness of the instrument was confirmed by using various pH indicating reagents and by analyzing trace elements in a seawater certified reference material.