estimation of blood glucose with procedure and principle?

Nelson somogyi’s method, o toluidine method,Asatoor king method, folin wu, ferricyanide, GODPOD and hexokinase method

Methodology
There are two different major methods that have been used to measure glucose. The older one is a chemical method that exploits the nonspecific reducing property of glucose in a reaction with an indicator substance that acquires or changes color on its reduction. Since other blood compounds also have reducing properties (e.g., urea, which can build up in uremic patients), this method can have erroneous measurements up to 5 to 15 mg/dl. This is solved by the Enzymatic methods that are highly specific for glucose. The two most common employed enzymes are glucose oxidase and hexokinase.

I. CHEMICAL METHODS
A. Oxidation-Reduction Reaction

1. Alkaline Copper Reduction
Folin Wu Method Blue end-product
Benedict’s method Modification of Folin wu for Qualitative Urine Glucose

Nelson Somoygi Method Blue end-product
Neocuproine Method * Yellow-orange color Neocuproine
Shaeffer Hartmann Somygi Utilizes the principle of Iodine reaction with Cuprous byproduct.
Excess I2 is then titrated with thiosulfate.

2. Alkaline Ferricyanide Reduction
Hagedorn Jensen Colorless end product; other reducing substances interfere with reaction
B. Condensation
Orht-touidine Method Utilizes aromatic amines and hot acetic acid
Forms Glycosylamine and Schiff’s base which is emerald green in color
This is the most specific method, but the reagent used is toxic

Anthrone (Phenols) Method Forms hydroxymethyl furfural in hot acetic acid

II. ENZYMATIC METHODS
A. Glucose Oxidase

Saifer Gernstenfield Method Inhibited by reducing substances like BUA, Bilirubin, Glutathione, Ascorbic Acid
Trinder Method uses 4-aminophenazone oxidatively coupled with Phenol
Subject to less interference by increases serum levels of Creatinine, Uric Acid or Hemoglobin
Inhibited by Catalase

Kodak Ektachem A Dry Chemistry Method
Uses Reflectance Spectrophotometry to measure the intensity of color through a lower transparent film

Glucometer Home monitoring blood glucose assay method
Uses a strip impregnated with a Glucose Oxidase reagent

B. Hexokinase

NADP as cofactor
NADPH (reduced product) is measured in 340 nm
More specific than Glucose Oxidase method due to G-6PO_4, which inhibits interfering substances except when sample is hemolyzed

Diabetes Diet Guidelines : The Exchange Method for Blood Sugar & Diabetes