Nonmembrane amperometric sensor for dissolved oxygen in flow-through systems

Enzymic substrate determination in closed flow-through systems by sample injection and amperometric monitoring of dissolved oxygen levels

“…To take advantage of the latter, fast detection is needed, and in this paper we describe the application of the three-electrode nonmembrane system reported previously (11). Because of the relatively low price of glucose oxidase, the determination of glucose in:…”

Repetitive determinations of amylase, maltose, sucrose, and lactose by sample injection in closed flow-through systems

“…Pertinent kinetic considerations for this reaction, after sample injection into a streaming solution and into a mixing coil, and the detection (amperometric) of the monitored species have been presented in a previous paper (1). The reactions coupled with the indicator reaction and preceding it were, for amylase determination: «-amylase Starch + nH20-* ( + 1 -x) Malto-oligosaccharides (2) maltase Maltose + H20- For maltose determination, reaction 3 is directly coupled with the indicator reaction; for sucrose and lactose determination, reactions 4 and 5 below are the ones so coupled; invertase Sucrose + H20-D-Glucose + fructose (4) lactase Lactose + H20-D-Glucose + galactose (5) The /3-galactosidase used in the present work had a very high lactase activity (almost 100%); lactase preparations from (3,16) have determined maltose and lactose using the same set of reactions but using, basically, the "Beckman Glucose Analyzer" commercial system which monitors oxygen with an electrode of the membrane, Clark-type. Their determination rates are, however, lower than those for the method reported here.…”

“…The work reported here was designed to exploit the use of reaction 1 (with glucose as substrate and glucose oxidase as enzyme) as an "indicator reaction" for the determination of other chemical species entering into enzyme-catalyzed reactions producing glucose as a product. Detection is based on the amperometric measurement of oxygen decrease according to the reaction of Equation 1 by means of a three-electrode nonmembrane system reported previously (2). This paper describes the determination of maltose, sucrose, and lactose by their enzyme-catalyzed hydrolysis to glucose and the estimation of the enzyme amylase by its catalytic effect on the hydrolysis of starch to glucose.…”

“…Nitrites have been regarded as potentially hazardous compounds (1). They oxidize hemoglobin to methemoglobin which is unable to transport oxygen (2)(3)(4) and they react with amines and amides to form nitrosamines, which are potent carcinogens (5)(6)(7)(8)(9). In view of the ubiquitous presence of nitrites in the environment (10), a sensitive method for trace level determination of nitrites is desirable.…”

Continuous-flow analysis for uric acid in biological fluids, with immobilized uricase in a closed-loop system

“…Interferences with the enzyme-catalyzed reaction are documented in the literature (22) and will not be discussed here. Interferences with the amperometric technique have also been discussed earlier (1,23). In the repetitive determination of uric acid, allantoin [5-ureidohydantoin] accumulates as a product.…”