Calibration of Glassware – Class A vs Class B

Class A

• Higher accuracy and tighter tolerance limits.

• Calibrated to meet ISO, USP, or ASTM standards.

• Used in critical pharmaceutical and analytical work where precision is crucial.

• Example tolerance for 100 mL volumetric flask: ±0.10 mL.

Class B

• Lower accuracy with approximately double the tolerance limits of Class A.

• Used in general laboratory work where ultra-high accuracy is not required.

• Example tolerance for 100 mL volumetric flask: ±0.20 mL.

Calibration Principle:

• Based on gravimetric method using distilled water and a calibrated analytical balance.

• Actual volume is calculated from water weight and density, compared against nominal capacity.

Key Difference in Calibration Approach:

• Same procedure for both classes, but acceptance criteria differ as per tolerance limits.

• Class A must meet tighter specifications; Class B allows larger deviations.