Methods of Glucose measurement Flashcards
Specimen considerations for glucose measurement to prevent glycolysis
Use of NaF or SST
Rate of glycolysis at room temperature if not prevented
7 mg/dL/h
Rate of glycolysis at 4°C if not prevented
2 mg/dL/h
Effect of 10% contamination with 5% dextrose
Artificially elevates glucose levels
Initial reaction of chemical glucose methods
Alkaline copper titrate (Benedict’s method)
Reaction involved in Folin-Wu method
Cu+ + phosphomolybdic acid → phosphomolybdenum (blue color)
Reaction involved in Nelson-Somogyi method
Cu+ + arsenomolybdic acid → arsenomolybdenum
Reaction involved in Neocuproine method
Cu+ + neocuproine → Cu-neocuproine complex (yellow/yellow-orange color)
Principle of Ferric Reduction (Hagedorn-Jensen method)
Ferricyanide (yellow-orange) reduced to ferrocyanide (colorless) by glucose
Reaction in condensation method (Dubowski method)
Glucose + o-toluidine → Schiff’s base (green color)
Glucose oxidase reaction in enzymatic method
β-D-glucose + O2 + H2O → Gluconic acid + H2O2
Detection method for glucose oxidase
Peroxidase-coupled (Trinder reaction)
End product of glucose oxidase detection (Trinder reaction)
Oxidized chromogen (quinonimine; red/red-purple) + H2O
Interference causing false increased glucose in Trinder reaction
Oxidizers
Interference causing false decreased glucose in Trinder reaction
Reducing agents (drug metabolites, ascorbic acid, ketoacids)
