Published Online: 15 SEP 2006
Copyright © 2000 John Wiley & Sons, Ltd. All rights reserved.
Encyclopedia of Analytical Chemistry
How to Cite
Cardosi, M. F. 2006. Glucose Measurement. Encyclopedia of Analytical Chemistry. .
- Published Online: 15 SEP 2006
Because of the pivotal role of glucose in physiological processes, much effort has been devoted to the development of methods for measuring glucose in food, microbiological and clinical matrices. The development of direct methods to measure glucose has been hindered by the lack of a suitable chromophore or indeed an electrophore. Consequently, more complex indirect methods have been developed based either on the chemical reactivity of the sugar, a particular enzymatic reaction or an indirect electrochemical measurement based upon the measurement of tensametric peaks or waves.
Although accurate and offering good sensitivity, chemical methods for the analysis of glucose such as the o-toluidine approach are not specific for glucose. Other hexoses such as mannose and galactose, some of their derivatives, aldopentoses and some disaccharides may also react, thereby complicating the measurement.
Because of the lack of specificity associated with chemical methods of measuring glucose, enzymatic methods have gained in popularity. Enzymes are very selective biological catalysts which carry out the conversion of a particular substrate into a product under mild operating conditions, i.e. room temperature, low ionic strength and near neutral pH. An enzyme will usually catalyze a single chemical reaction or a set of closely related chemical reactions. Side reactions leading to wasteful formation of by-products rarely occur. Thus, quantitative assays may be done on crude materials with little or no sample preparation. The enzymes which are currently used for the measurement of glucose include hexokinase (EC 184.108.40.206; adenosine triphosphate (ATP): d-hexose-6-phosphotransferase), glucose oxidase (EC 220.127.116.11; β-d-glucose: oxygen 1-oxidoreductase) and glucose dehydrogenase (EC 18.104.22.168; β-d-glucose: (nicotinamide adenine dinucleotide phosphate (oxidized form)) NAD(P)+ 1-oxidoreductase). The mode of detection that is used to measure the activity and hence concentration of glucose, ultimately depends upon the nature of the enzymatic reaction itself and is usually colorimetric or electrochemical.
More recently, new analytical methodologies based upon the direct electrochemical detection of glucose using pulsed amperometric detection (PAD) have been developed. Coupled with liquid chromatography (LC), this technique is proving to be a highly selective and sensitive method for the measurement of glucose in a wide variety of sample matrices.