Reagents
All reagents used in the presented work were of analytical reagent grade unless otherwise stated. Double deionised water (Milli-Q Mliilpore 18.2 M /cm conductivity) was used for all dilutions. Acids like HNO3,H2O2, and HCl were of suprapur quality (E Merck). All the plastic and glassware were cleaned by soaking in dilute HNO3 (1+9) and were rinsed with distilled water prior to use. The standard solution of analytes used for calibration were produced by diluting a stock solution of 1000 mg/l of the given element supplied by Sigma-Aldrich (St Louis,MO,USA).