Quick Review Cards for Medical Laboratory Science

Chemistry Calculations

FORMULA EXAMPLE

Beer’s law: Concentration of unknown =

Absorbance of unknown × concentration of standard

Absorbance of standard

mEq/L = mg/dL × 10

GEW*

mmol/L = mg/dL × 10

GMW†

Clinical Chemistry Review 131

A manual glucose assay gave the following results: Absorbance

of 100 mg/dL standard = 0.3.

Absorbance of patient = 0.4. What is the glucose concentration of the patient?

Concentration =0.4× 100 = 133 mg/dL

0.3

(Note: If a dilution is run, multiply answer by reciprocal of dilution.)

A calcium is reported as 10 mg/dL. What is the concentration in mEq/L?

(Atomic weight of calcium = 40. Valence of calcium = 2+.)

mEq/L = 10 × 10 = 5

20

A calcium is reported as 10 mg/dL. What is the concentration in mmol/L?

(Atomic weight of calcium = 40. Valence of calcium = 2+.)

mmol/L = 10 × 10 = 2.5

40

continued...

*GEW = gram equivalent weight (gram molecular weight ÷ valence).
†GMW = gram molecular weight