Page 254 - Analytical method for food addtives

168 Analytical methods for food additives

Dilute grape juices at 1 to 20 volumes (concentrates 1 to 100) and directly use
them for HPLC analysis after filtration through a 0.45 µm membrane filter. (When
frozen samples are used, ensure that there is no sediment in the sample before
dilution).

Preparation of calibration solutions
Prepare the calibration solutions in the range of 100 mg/L to 500 mg/L of tartaric
acid using suitable solutions of the standard tartaric acid solution. Use the solutions
as described in HPLC analysis.

HPLC analysis
Inject the calibration solutions and the samples in an HPLC system with the
following conditions:
Eluent 0.005 mol/L sulphuric acid
Column Separation column, ion-exclusion column made of
sulphonated divinyl benzene–styrene copolymer in hydro-
gen form, typical particle size 10 µm, (300 mm × 7.8 mm)
+
with a cation H precolumn
Flow e.g. 0.6 mL/min (to avoid a high pressure the flow should be
increased slowly from 0.2 mL/min to 0.6 mL/min during
equilibration)
Wavelength 210 nm
Injection volume typically 15 µL
Running time 20 min
Retention time approximately 10 min for tartaric acid
Temperature 40 °C