The Ascorbic Acid test strip is based on discoloration of blue red-ox indicator, depending on the concentration of ascorbic acid. The Ascorbic Acid test strip is calibrated from 0.01% (10 mg/100 ml) to 0.1% (100 mg/100 ml). Red-ox indicator is also sensitive to acidic compounds, and its blue color turns to purple in the presence of acids.
The Vitamin C strips are buffered to a certain extent to keep the blue color of the pad, but in the presence of strong acids, contained in some fruits or juices, the color can turn to a purple-pink instead of a blue-white. In such cases, we recommend using a special color chart (See “Ascorbic Acid Color Changes” chart below) which shows results for Vitamin C in the presence of different concentrations of citric acid. Lemons and limes contain the highest amount of citric acid at about 5 percent. Grapefruits and oranges also have high content of citric acid at about 2.5 and 2 percent, respectively.
In the “Ascorbic Acid Color Changes” chart (click button below), the values are as follows:
Low = 0.5%; Medium = 1%; High = 5%
