EtOH HS-GC agilent 8860


I'm using HS-GC 8860 for quantification of EtOH in DP.

I have some problem with Precision-repeatability -> analysing three replicates of same sample RSD% 8% (single data:89-85-76) and second analysis RSD% 4% (single data 88-91-95)

Oven temperature set is: gradient of 40°C/minute until 240°C

Sample Oven: 80°C

The problem could be related to HS tecnique or method or not?

  • Is DP == EastmanTm DP Solvent (Diethylene Glycol Monopropyl Ether) .  boiling point 201.9° C.  EtOH boiling point is 78.37° C, so your sample oven is so hot that the ethanol is boiling.   The typical sample oven temperature used for compounds is 10° C or more less than the boiling point of the highest boiling point ingredient.   The Agilent blood alcohol analyzer uses 70° C looking for ethanol. 

    Above its boiling point, every microliter of ethanol makes 507 microliters of vapor - 1/2 a milliliter. This will change the vial pressure and negatively impact reproducibility.  How much sample are you loading, what size vial, and what concentration of EtOH are you measuring?

    And...three replicates would be three separate vials of the same sample?  Just being careful as every time a HS vial is analyzed the headspace concentrations change.  

  • Hi, DP stands for Drug Product (I need to determine EtOH in a drug product not in a drug substance DS).

    I'm loading 3 mL of sample in vial size 20 mL. The concentration of EtOH 4 mg/mL.

    Yes of course, three replicates of three separate vials (same sample preparation).

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