Automated flow-injection pseudotitration of strong and weak acids, ascorbic acid and calcium, and catalytic pseudotitrations of aminopolycarboxylic acids by use of a microcomputer-controlled analyser

• Published in: Talanta (Oxford) 1985-05, Vol.32 (5), p.411-417
• Main Authors: Koupparis, M.A., Anagnostopoulou, P., Malmstadt, H.V.
• Format: Article
• Language: English
• Subjects: Analytical chemistry; Chemistry; Exact sciences and technology; Spectrometric and optical methods
• ISSN: 0039-9140; 1873-3573
• DOI: 10.1016/0039-9140(85)80108-9

A simple, inexpensive, fully automated spectrophotometric system for flow-injection pseudotitrations is used to perform acid-base, redox, complexometric and catalytic “titrations”. Peak widths (in time units) in the range 10–100 sec can be measured with a precision of better than 0.3% in most cases. Strong and weak acids in the range 5.0 × 10 −4–1.0 × 10 −2 M are measured by using sodium hydroxide-Bromothymol Blue “titrant”. Ascorbic acid (1 × 10 −4–1 × 10 −2 M) is “titrated” with 2,6-dichlorophenolindophenol, and calcium (5.0 × 10 −4–5.0 × 10 −2 M) with EDTA, with calmagite as indicator in the presence of magnesium. Aminopolycarboxylic acids (5 × 10 −6–1 × 10 −2 M) are measured by use of catalytic indication based on the manganese-catalysed periodate-diethylaniline reaction. The ascorbic acid method has been applied to analysis of pharmaceutical preparations, and the calcium method to water analysis.