Dry reagent chemistry elements

CONSTRUCTION OF DRY REAGENT CHEMISTRY ELEMENTS 4.1. Layer Construction... 

Most dry reagent chemistries are designed to be self-contained analytical devices. Each element may have several functional zones that are introduced as single layers or combined into one layer during construction. Regardless of the number of layers present, all dry reagent elements have a support function, a reflectance function, and an analytical function (Fig. I). Some elements may also contain a sample-spreading function. 

A dry reagent chemistry is designed to simplify what otherwise is a complex multistep analytical procedure for the user. The sole function of the element is to convert an analyte in a sample to a specific qucuitifiable material. To accomplish this, all physical and chemical functions needed for an tinalysis must be integrated into one element. 

Dry reagent chemistries have been described for the analysis of a variety of blood constituents. These include metabolites, enzymes, electrolytes, hormones, and therapeutic drugs. A partial list is presented in Table 3. With the exception of electrolytes, nearly all analyses depend on enzyme-mediated chemistries and that includes immunochemical assays. A brief survey of element structures will illustrate how physical functions and chemical reactions used in conventional multistep procedures are integrated in the construction of dry reagent test devices. These examples will illustrate how reactions in dry reagent elements can be compartmentalized and how end produas are shunted to other compartments for further reaction. In its final form, each element provides a complete analytical procedure. 

The oldest example of an integrated dry reagent chemistry for quantitative analysis of a metabolite is the Dextrostix reagent strip (Miles Dia ostics) for whole blood glucose analysis. The cross section of the element is illustrated in Fig. 8a. The detection chemistry is the well-known glucose oxidase-peroxidase procedure. Approximately 50 pL of whole blood is applied to the surface of the... 

Dry rej ent chemistries open a new era in user convenience. The user needs only apply the sample to the element to initiate an analysis the analysis is usually rapid, taking only a few minutes. No rej ent preparation or analyte separations from sample components are required. By virtue of their stability and discrete formats, these elements allow both low- and high-volume testing to be cost effective. These devices are easy to store, requiring less space than reconstituted conventional wet chemistry reagents, and they are easily disposable after use. 

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