Dry chemistry analyser

Only solid samples are tested on dry chemistry analysers BECAUSE... 

RI28 Seftel, H.C., Panz, V.R., Baker, S.G., Joffe, B.I. and Mendelsohn, D. (1988). Determination of cholesterol and triglycerides in blood A comparison between wet chemistry methods and a dry chemistry analyser. Ann. Clin. Biochem. 25, 176-180. 

For n = 15 cereal samples from barley, maize, rye, triticale, and wheat, the nitrogen contents, y, have been determined by the Kjeldahl method values are between 0.92 and 2.15 mass% of dry sample. From the same samples near infrared (NIR) reflectance spectra have been measured in the range 1100 to 2298 nm in 2nm intervals each spectrum consists of 600 data points. NIR spectroscopy can be performed much easier and faster than wet-chemistry analyses therefore, a mathematical model that relates NIR data to the nitrogen content may be useful. Instead of the original absorbance data, the first derivative data have been used to derive a regression equation of the form... 

No final answer can be given to this question, for similar cases are also known in wet chemistry (for example, the Pack Analyzer ACA of DuPont de Nemours). Here, too, the apparatus or method is calibrated once for every batch and is rechecked daily or at regular intervals by means of the quality control sample. The system of dry chemistry can be viewed under the same aspect. The Ektachem system is known to be stable for more than 6 months, so that the apparatus or method need not be readjusted during this period but only supervised via quality control checks. The problem of calibration does not arise with Reflotron, since all the requisite data (calibration data) are stored on the reverse of the test slides. No data, however, are available on long-term studies of stability. The FDA has prescribed a 7-day or 30-day calibration rhythm for the Seralyzer system depending on the analyte to be analysed. 

The advantage of dry chemistry technology is that it eliminates the need for reagent preparation and many other manual steps common to liquid reagent systems, resulting in greater consistency and reliability of test results. Each test unit contains all the reagents and reactants necessary to perform analyses. 

Figure 6.4 Cross-section through a dry reagent slide for use in the Vitros Chemistry System, previously known as the Kodak Ektachem analyser. A range of slides, which vary in the nature, number and composition of the layers, is available for a variety of analytes in blood serum. The sample (approximately 10 /d) is applied to the spreading layer and reactions take place as it permeates through the various layers. Detection is by reflectance photometry.

In short, Zc and Utotal provide powerful, rigorous constraints on the interpretation of other analytical data from 13C NMR spectrometry or ultra-high-resolution mass spectrometry, which must ultimately be reconciled with the bulk chemistry of a sample of DOM. Calculations of Zc and f7total for bulk samples of DOM are only possible if elemental analyses for H and O are performed. This is a strong incentive for developing methods to more readily obtain suitable dry, ash-free samples of marine DOM. 

In interpreting marine precipitation-chemistry data, the differentiation of sea-salt and non-sea-salt (or excess sea-salt) components is essential. Uncertainties in such calculations arise from the uncertainties regarding (1) the composition of seawater, (2) the analyses, (3) the amount of dry-deposited sea salt in the samples,... 

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. 

Analyses for Which Dry Reagent Chemistries Have Been Reported... 

Constructing dry reagent chemistries for blood enzyme analysis presents new levels of complexity, since enzymes are too large to readily diffuse through most conventional matrices. In addition, many enzyme analyses require coupling multistep reactions which are frequendy catalyzed by other enzymes. Some dry reagent matrices have a large, open lattice that allows free diffusion of macro-... 

Proximate analyses of the fuel and char were run using a standard laboratory drying oven, muffle furnace, and analytical balance according to ASTM Standard Methods. Ultimate Analysis for percent C, H, N, S, and O in the fuel char, and condensate was conducted by the Chemistry Department, University of California, Berkeley. The energy content of the fuel and char was determined with a Parr Oxygen Bomb Calorimeter. 

Malley et al. (1993, 1996) also analysed N, P and C content in lake-water seston. The seston was captured on a glass fibre filter, dried and scanned on a NIR reflectance instrnment. A sub-set of the samples was used to develop calibration functions, while the remaining samples were nsed to test the prediction performance. The r -values between NIR predictions of C, N and P, and the wet chemical determinations, ranged between 0.88 and 0.97. The authors concluded that the prediction performance was as good as for the wet-chemistry techniques used. 

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