SPSFAM Heavy Metals ERP Book

described above and use the calculated arsenic concentration in all future calculations. To prepare from a 10ug/mL stock solution, pipet (4) MMA working standard, As = 1 μg/g in H 2 O .—Tare a 125 mL HDPE or polypropylene bottle. Pipet 100 μL (~0. 1 g, accurately weighed) of 1000 μg/g MMA stock solution into the bottle. Dilute to 100 g total with DIW. Analyze for total arsenic as described above and use the calculated arsenic concentration in all future calculations. (5) As(V) working standard, As = 1 μg/g in H 2 O .—Tare a 125 mL HDPE or polypropylene bottle. Pipet 100 μL (~0.1 g, accurately weighed) of 1000 mg/L As(V) stock solution into the bottle. Dilute to 100 g total with DIW. This standard does not require concentration verification because the stock is traceable to a NIST SRM. (6) Multianalyte spiking solution, As(III), DMA, MMA, and As(V); 1000 ng/g As each .—Prepare the multianalyte spiking standard by weight in DIW using the 1000 μg/g DMA and MMA stock standards and the 1000 mg/L As(III) and As(V) stock standards. Pipet 100 μL (0.1 g) of each stock standard into a 125 mL HDPE or polypropylene bottle. Dilute to 100 g total with DIW. This multianalyte spiking standard may be used for up to 3 months if stored in tightly sealed polypropylene container in the dark at 4°C, but should be periodically checked (e.g., monthly) for As(III), As(V), DMA, and MMAconcentrations. (e) Calibration standards .—Prepare a minimum of four mixed analyte standards in DIW for instrument calibration. Record all weights to calculate standard concentrations in nanograms-per- gram units. Multianalyte calibration standards and calibration check standards should be prepared fresh on the day of use. However, multianalyte calibration standards may be used for up to 1 week if kept in the dark at 4°C and if standard chromatograms do not show evidence of interconversion of arsenic species. (1) 200 ng/g each As(III), DMA, MMA, and As(V) .—Tare a 15 mL HDPE or polypropylene tube. Pipet 1 mL (~1.0 g) each of As(III), DMA, MMA, and As(V) of the 1 μg/g working standards into the tube. Dilute to 5 g total with DIWand mix thoroughly. This standard is used in the preparation of calibration standards, but not analyzed. (2) For quantification using a calibration plot .—( a ) As(III), DMA, MMA, and As(V); 10 ng/g each .— Pipet 500 μL (~0.500 g) of the 200 ng/g multianalyte solution into a tared HDPE or polypropylene tube. Dilute to 10 g total with DIW and mix thoroughly. (b) As(III), DMA, MMA, and As(V); 4 ng/g each .—Pipet 200 μL (~0.200 g) of the 200 ng/g multianalyte standard solution into a tared HDPE or polypropylene tube. Dilute to 10 g total with DIW and mix thoroughly. (c) As(III), DMA, MMA, and As(V); 1 ng/g each .—Pipet 1.0 mL (~1.0 g) of the 10 ng/g multianalyte calibration standard solution into a tared HDPE or polypropylene tube. Dilute to 10 g total with DIW and mix thoroughly. (d) As(III), DMA, MMA, and As(V); 0.4–0.5 ng/g each .—Pipet 500 μL (~0.500 g) of the 10 ng/g multianalyte calibration standard solution into a tared HDPE or polypropylene tube. Dilute to 10 g total with DIW and mix thoroughly. Note : This standard should be at or slightly above the laboratory’s analytical solution quantitation limit (ASQL). (e) Calibration check standard .—Prepare a 2 ng/g mixed- species standard for the check standard . Pipet 100 μL (~0.1 g) of the 200 ng/g multianalyte standard solution into a tared HDPE or polypropylene tube. Dilute to 10 g with DIW and mix thoroughly.

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