Fluoride determination by its inhibitory effect on immobilised liver esterase

• Published in: Analytica chimica acta Vol. 310; no. 1; pp. 173 - 180
• Main Authors: Marcos, J., Townshend, A.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 25.06.1995
• Subjects: Ethyl butyrate; Flow injection; Fluoride; Inhibition; Liver esterase; Fluoride; Inhibition; Liver esterase; Ethyl butyrate; Flow injection
• ISSN: 0003-2670; 1873-4324
• DOI: 10.1016/0003-2670(95)00103-7

The inhibition of liver esterase (EC 3.1.1.1.) immobilised on controlled pore glass by fluoride ions was studied in a flow injection system. Ethyl butyrate was used as substrate, ethanol and butyric acid being produced as hydrolysis products. To monitor the reaction a second enzymatic reaction was employed, in which alcohol dehydrogenase, immobilised on controlled pore glass, catalysed the oxidation of ethanol and reduction of the coenzyme, NAD +, to NADH, the latter being determined spectrophotometrically at 340 nm. Fluoride inhibition of the immobilised liver esterase was fast and reversible, and there was a linear relationship between %inhibition and fluoride concentration over the range 8 × 10 −7−8 × 10 −6 M (15–150 μg 1 −1) fluoride. The relative standard deviation at mid-calibration range is below 4% ( n = 5). The more common inorganic compounds present in water samples do not interfere in the fluoride determination.