as we know absorbance shouldnt go greater then 2. but i observed 4.398 for 20ppm. if i make low concentrations solution of 2-10ppm then absorbance will be within the range for standard line but what about next parameter like concentration effect, pH effect or dosage effect? if next i go with 25ppm to check other parameters then will it be fine? or i must do next parameters for 10ppm?