How can the exact concentration of glycol in a coolant be determined?
Analysis with GC-FID
A refractometer reading will only work if there is one type of glycol, i.e. you will get a reading regardless of what has been mixed into the coolant, but the freezing point that is read off will not be correct.
For example, if 5% vodka and 10% ethylene glycol are mixed with water, a refractometer may tell you that the freezing point is -19°C and 23% glycol. This is incorrect. The exact concentration of glycol is determined by analysis with Gas Chromatography (GC). The freezing point can then be calculated based on the measured amount of glycol. GC analysis is an additional analysis that must be ordered