Ascorbic acid assay from Vinpocetine etc solution
Posted: Tue Feb 06, 2018 5:05 pm
We've recently tried several chromatography methods for ascorbic acid assay:
- SAX, 0.1M AcONH4 / AcN 1/1: ideal peak and specificity
- NH2, 0.1M AcONH4 / AcN: tailing peak, no specificity
- C18, TBA HSO4 pH 5 / MeOH 95/5: tailing peak, poor specificity
Finally SAX wins
However method validation shows
+ quantification limit ~ 1 % from nominal concentration
+ recovery 100 ± 7 %
+ linearity with r2 > 0.999
- residual member ~ (minus 10 %) from nominal area
- unstable (day-to-day) slope coefficient (probably because of pH and UV spectra instability, however adsorption maximum seems to be constant)
Matrix:
- Adcorbic acid - 0.5 mg/ml
- Vinpocetine - 5 mg/ml
- Sorbitol
- Benzyl alcohol
- Metabisulfite sodium
- Tartric acid - up to pH from 3 to 4
Test solution: test sample as is.
Reference solution: ascorbic acid, sorbitol, tartric acid, water.
Any ideas are welcomed!
- SAX, 0.1M AcONH4 / AcN 1/1: ideal peak and specificity
- NH2, 0.1M AcONH4 / AcN: tailing peak, no specificity
- C18, TBA HSO4 pH 5 / MeOH 95/5: tailing peak, poor specificity
Finally SAX wins
However method validation shows
+ quantification limit ~ 1 % from nominal concentration
+ recovery 100 ± 7 %
+ linearity with r2 > 0.999
- residual member ~ (minus 10 %) from nominal area
- unstable (day-to-day) slope coefficient (probably because of pH and UV spectra instability, however adsorption maximum seems to be constant)
Matrix:
- Adcorbic acid - 0.5 mg/ml
- Vinpocetine - 5 mg/ml
- Sorbitol
- Benzyl alcohol
- Metabisulfite sodium
- Tartric acid - up to pH from 3 to 4
Test solution: test sample as is.
Reference solution: ascorbic acid, sorbitol, tartric acid, water.
Any ideas are welcomed!