Chemistry Equations Flashcards
Magnesium (Atellica)
Mg2+ + xylidyl blue
-> (OH-)
Xylidyl blue Mg complex
Increase in absorbance at 505/694
Calcium (Atellica)
Ca2+ + Arsenazo III
-> (pH 5.9)
Ca-Arsenazo III complex
Increase in absorbance at 658/694
Total protein (Atellica)
Peptide bonds react with cupric sulfate (biuret reagent) in an alkaline environment - “Weichselbaum method”
Protein + CuSO4 –> (OH-) Cuproproteinate complex
Measured at 545nm
Indirect (total) bilirubin and direct bilirubin - method
Indirect:
All bilirubin is made water soluble first by accelerator (caffeine benzoate in Jendrassik Grof method (reference method)
Addition on alkaline tartrate to shift absorption ?avoid haemolysis interference)
Bilirubin + vanadate (detergent + pH 2.9) –> Biliverdin
Decrease in absorbance (of bilirubin) at 451/545nm
Endpoint reaction
Direct:
Conjugated bilirubin + vanadate (pH3 + detergent) –> bilverdin
Decrease in absorbance at 451/545
What is delta-bilirubin, and which analyser can measure it?
conjugated bilirubin + albumin
determined on Vitros analyser
Biilirubin interferences
degraded by direct light
heparin effects
haemolysis - particularly conjugated on Abbott archi
Advantages of the Vitros dry method for bilirubin
Masking layer prevents proteins incl delta bili and hb from being included in measurement - delta-bilirubin measurement can be determined and excluded from the measurement of conjugated bilirubin in neonates - all neonatal bilrubins are done by Vitros at PathWest.
Less affected by haemolysis
CK (Atellica equation)
Modified procedure of Szasz
Concentration of NADPH measured by increase in absorbance at 340/596nm.
LDH (Atellica equation)
Amount of NADH produced measured by increase in absorbance at 340/410 nm
Amylase method/equation
Released p-nitrophenol is measured at 410/694nm
Lipase method
Production of methylresorufin is measured at 571/694nm
ALT method
Decrease in absorbance of NADH is measured at 340/410nm
AST method
Decrease in absorbance measured at 340/410nm
ALP method
Measured using a bichromatic rate technique. Change in absorbance of p-nitrophenol at 410nm directly proportional to ALP.
Creatinine method (Atellica)
Modified Jaffe reaction: Creatinine reacts with alkaline picrate to form red-coloured creatinine picrate, detected at 505/571nm. Modified to include rate blanking (to minimise bilirubin interference) and intercept correction (as non-specific protein interactions with the reagent produce a positive bias).
Phosphate method (Atellica)
Pi + ammonium molybdate (H2SO4) -> phosphomolybdate detected by spectrophotometry as an endpoint reaction at 340nm/658nm
Urea (Atellica)
Urea is hydrolysed by urease to ammonia and carbon dioxide. In the second step, glutamate dehydrogenase catalyses to conversion of ammonia and alpha-ketoglutarate to glutamate, oxidising NADH to NAD. The decrease in NADH concentration is measured as an inverse rate reaction at 340/410nm.
Ammonia (Beckman AU680)
Glutamate dehydrogenase catalyses the conversion of ammonia and alpha-ketoglutarate to glutamate, oxidising NADH to NAD in the process. Decrease in NADH is measured at 340/410nm.
LDH is added in excess to rapidly reduce endogenous pyruvate so that it does not interfere with the assay system
Uric acid method (Atellica)
Uric acid + water + O2 catalysed by uricase to allantoin, CO2 and hydrogen peroxide
Hydrogen peroxide enters a Trinder-like reaction to form a quinone diimine dye the absorbance of which is measured by spectrophotometry and is directly proportional to the uric acid concentration.
Glucose method (Atellica)
Glucose + ATP catalysed by hexokinase to glucose 6 phosphate
Glucose 6 phosphate + NAD catalysed by G6PD to 6 phosphogluconate + NADH
Absorbance of NADH measured by spectrophotometry proportional to concentration of glucose.
