The ISO and CDFA methods provide the most accurate determination of HA concentrations as they rely on gravimetric analysis. In these methods, HA is extracted from a liquid or solid sample of known weight, dried, and then its weight is divided by the weight of the original sample to calculate the HA concentration. Both these methods produce far more accurate results than the colorimetric test.
The ISO method is considered more precise than the CDFA method because it includes an analysis of the ash content in the extracted and dried HA. The HA concentration is then determined by dividing the ash-corrected weight of the HA (thus pure HA) by the weight of the original sample.
