The Determination of Halides and Pseudohalides by the Vanadium Haloperoxidase Based Biosensor

• Published in: Analytical letters Vol. 31; no. 15; pp. 2607 - 2623
• Main Authors: Kulys, J., Vidziunaite, R.
• Format: Journal Article
• Language: English
• Published: Philadelphia, PA Taylor & Francis Group 01-12-1998; Taylor & Francis
• Subjects: Amperometry; Azide; Biological and medical sciences; Biosensor; Biosensors; Biotechnology; Bromide; Chloride; Chloroperoxidase; Cyanide; Fundamental and applied biological sciences. Psychology; Iodide; Methods. Procedures. Technologies; Nitrate; Thiocyanate; Vanadium; Various methods and equipments; Iodides; Enzyme; Vanadium; Carbon electrode; Cyanides; Nitrates; Enzyme electrode; Azides; Chloride peroxidase; Peroxidases; Halides; Biosensor; Chlorides; Graphite; Amperometry; Bromides; Thiocyanates; Oxidoreductases; Immobilized enzyme
• ISSN: 0003-2719; 1532-236X
• DOI: 10.1080/00032719808005330

A biosensor containing vanadium haloperoxidase (VHP) immobilized on a graphite electrode responded to the halides and hydrogen peroxide at electrode potentials from -0.1 to 0.25 V vs SCE. An apparent Michaelis-Menten constant (K
m
) of the biosensor was 12-14 μM for hydrogen peroxide at 0.1-0.2 mM of KCl and 0.1 mM of sodium vanadate. K
m
decreased up to 2.3 μM in a vanadate free solution. At the same conditions and at a fixed concentration (0.1 mM) of hydrogen peroxide K
m
for chloride changed from 0.6 to 2.5 mM. K
m
for bromide was 9-16 μM and for iodide it was 5.5 μM. The biosensor response was largest at pH 5.1-5.3 and at pH 6.1 in presence of chloride and iodide, respectively.
KNO
3
in a competitive manner inhibited the biosensor response; K
i
was 0.6 and 0.27 mM, for bromide and chloride. K
i
for thiocyanate and for the same halides was 0.25 and 0.08 μM. 10.1 μM of cyanide inhibited 50 % of the biosensor response at 5 mM of chloride. Sodium azide irreversibly inhibited the biosensor response at 1-2 nM and in the presence of 10 μM of bromide or 5 mM of chloride.