Ultra-Trace Determination of Phosphate Ion Based on Filtration-Dissolution and Flow-through Spectrophotometric Measurement

• Published in: Analytical Sciences Vol. 11; no. 1; pp. 155 - 160
• Main Authors: MOTOMIZU, Shoji, SUSANTO, Joko P., OSHIMA, Mitsuko, MIKASA, Hiroshi, HORI, Yoshikazu
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Tokyo The Japan Society for Analytical Chemistry 1995; Japan Society for Analytical Chemistry; Japan Science and Technology Agency
• Subjects: Analytical chemistry; Chemistry; Exact sciences and technology; filtration-dissolution; molybdophosphate-Malachite Green ion associate; Phosphate determination; Spectrometric and optical methods; Trace analysis; Water; Phosphates; Absorption spectrometry; Chemical analysis; Interelement effect; Spectrophotometry
• ISSN: 0910-6340; 1348-2246
• DOI: 10.2116/analsci.11.155

A sensitive spectrophotometric method for the determination of ultra-trace amounts of phosphate ion is proposed. The colored ion associate formed between molybdophosphate and Malachite Green (MG) was filtered through a tiny membrane filter (cellulose nitrate; poresize, 1.0μm; 9mm diameter), dissolved together with the membrane filter in 1cm3 or less of Methyl Cellosolve; the absorbance of the solution was then measured at 627nm with a flow-through system equipped with an autosampler. The absorbance, the standard deviation and the relative standard deviation of the reagent blank were 0.0270, 0.0005 and 1.8%, respectively. A calibration graph was linear over the range from 0.018 to 1.0ng cm-3 (1ppb) of phosphorus using 40cm3 of sample solutions; the detection limit corresponding to two-times the standard deviation of the reagent blank was 3ppt of phosphorus. By using the proposed method, phosphate ion in pure water samples were determined.