3. Results and discussion
3.1. Method development
3.1.1. Liquid chromatographic conditions
A good separation of carmine and carminic acid can be achieved
with 15% methanol and phosphate buffer (pH 6.0) as the mobile
phase system under the isocratic elution condition described
above. Since carmine has the similar absorption spectrum of
carminic acid at the range of 200–500 nm, several C18 columns
were tested for the separation of carmine and carminic acid. Using
the conventional analytical column (NovaPak C18, Waters,