48-9
LEAD, continued
b) Swirl the sample to mix. Then test the sample as described in the
procedure. Each 0.1-mL of standard added should increase the lead
concentration determined in Step 20 by 10 µg/L.
Standard Solution Method
A 50-µg/L lead standard solution can be prepared by first pipetting
1.00 mL of Lead Standard Solution, 1000 mg/L as Pb, into a 100-mL
plastic volumetric flask and diluting to the mark with lead-free water to
make a 10 mg/L lead working solution (included in the reagent set).
Pipet 5.00 mL of this working solution into a 1-liter plastic volumetric
flask. Dilute to the mark with lead-free water. This 50-µg/L standard
solution should be prepared immediately before use.
Alternatively, a 50-µg/L lead standard solution can be prepared by using
a TenSette Pipet and pipetting 0.1 mL from a Lead Voluette Ampule
Standard Solution, 50 mg/L as Pb, into a 100-mL plastic volumetric
flask and diluting to volume with demineralized water. This solution
should be prepared immediately before use.
INTERFERENCE
Interference studies were conducted by preparing a known lead solution of
approximately 25 µg/L as well as the potential interfering ion. The ion was
said to interfere when the resulting concentration changed by ±10%.
Ion Interference Level
Aluminum, Al
3+
0.5 mg/L
Barium, Ba
2+
6 mg/L
Calcium, Ca
2+
500 mg/L
Chloride, Cl
-
1000 mg/L
Copper, Cu
2+
2 mg/L
Fluoride, F
-
10 mg/L
Iron, Fe
2+
2 mg/L
Magnesium, Mg
2+
500 mg/L
Manganese, Mn
2+
0.5 mg/L
Nitrogen, Ammonium, NH
4
+
500 mg/L
Nitrogen, Nitrate, NO
3
-
1000 mg/L
Sulfate, SO
4
2-
1000 mg/L
Zinc, Zn
2+
1 mg/L
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