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Spectrophotometric method has low cost and acceptable specificity in comparison with radio ligand assay.The main advantages of this method are that it has a high sample throughput, it is easy to use, and it has high precision.But the main disadvantages involve its less sensitivity, its requirement of large sample, and the problems with refraction.Another method that is used is the flame atomic absorption spectrometry.The lowest concentration for quantitative recovery is ngcm of vitamin B.This method is so sensitive that it can measure one trillionth of grams of substance per milliliter of blood   and only small samples are required.These made RIA to quickly become a standard laboratory tool.RIA is based on the reaction of antigen and antibody in which very small amounts of the radio labeled antigen competes with endogenous antigen for limited binding sites of the specific antibody against the same antigen.The pump of the system must be able to generate high pressure, performing a pulsefree output and deliver flow rates ranging from. HPLC results are often precise, and it is very sensitive with detection limits of nmolL.It is one of the most <a href="http://www.targetmol.com/compound/Saccharin"></a> important instruments for both routine and research applications.MS actually measures mass to charge ratio and not just the mass.The first described ionization source is the electron ionization where the sample must be of low molecular weight, vaporizable and thermally stable.The analytes has to be vaporized and then ionized, and these limited the availability of such method for many biological samples and analytes so there was great need for developmental ionization sources.The linearity of MS is over the cobalamin concentration range of. ngml for both ICPMS and HPLCMS.This method employs various test principles for the measurement.The most important method in measuring vitamin B concentration is the competitive principle.The competitive principle is applied to low molecular weight molecules.It uses antibodies for vitamin B labeled with ruthenium complex.These antibodies are incubated with the sample, then biotinylated vitamin B and streptavidin which is coated with paramagnetic miroparticles are added to the mixture.The free binding sites of the labeled antibody become occupied with the formation of an antigen hapten complex.Then the entire complex is bonded to biotin and streptavidin.After incubation the reaction mixture is transported into the measuring cell where the immune complexes are magnetically entrapped on the working electrode and the excess unbound reagent and sample are washed away.Then the reaction is stimulated electrically to produce light which is indirectly proportional to the amount of vitamin B that is measured.. REVIEW OF SOME METHODS OF CHEMICAL ANALYSIS A given compound can often be measured by several methods.These methods are still widely used in official compendial assays, because of their robustness, cheapness and capability of high precision.They involve the use of volumetric flasks, burettes, conical flasks, beakers and pipettes.The chemical methods of analysis are sometimes referred to as stoichiometric methods, since an analyte is chemically reacted with a standard amount of solution of a reagent of precisely known concentration or with a concentration that can provide data for calculating the precise amount of the compound.

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