Experiments to determine the sample loading volume were performed by passing increasing volumes between 250-2000mL at increments of 250mL until 1500mL and at increments of 50 mL up to 2000 mL) of aqueous solutions at pH 7 containing 50 g of all ions, through the solid phase column filled with 1.0 g of alumina, 50 mg of SDS (hemimicellar/ admicellar region), and 20mg BMPBDA, then determining the amount of all analyte ions eluted with nitric acid. This trait gives the feasibility of determination of the sample with different analytes concentration levels. However, it should be pointed out that the larger amount of the sample solution, the more time (for passing it through solid phase) was required in the procedure. To trade off the enrichment
factor and analytical speed, 1800 mL sample and 6.0 mLHNO3 were used; therefore, an enrichment factor of 300 was obtained.