Each lens was placed into pre weight digestion tube. The sample was weighted to determine a dry weight (gram) after drying at 95°C overnight [7]. Next day reweighed to determine dry weight (gm), then (1 ml) of concentrated nitric acid was added digest tube which was placed in waterbath at 100°C, the sample digested for approxi- mately 1 h. until all tissues material has been dissolved, then (1 ml) perchloric acid was added until (deep brown color) with clear solution was obtain dilute each sample to mark with deionized water to 10 ml.