NOTE: If the concentration (M) of any of the following is expected to exceed the lead
concentration (M) by 10-fold or more, add 1 mL 1 M NfEDTA to each flask before dilution to volume: CO , PO4 , I , F , CH3COO . If Ca2+ or SO4 are present in 10-fold or greater excess, make all standards and samples 1% (w/w) in LS[3].