Figure 3 presents the correlation between peak area and wine volume at constant deposition time for the three elements studied.
As the cadmium concentration in many wine samples was very low (around 0.2 ng/mL), it was
necessary to use a minimum volume of 3 mL to generate an acceptable analytical signal. With this volume, the copper signal was often 200 times higher than the cadmium signal
. To improve the precision of the cadmium determination in wine, it was necessary to separate the cadmium determination from the copper determination. Only with some samples was it possible to determine all three elements simultaneously with similar precision.