MONITORING AND LABORATORY DIVISION
STANDARD OPERATING PROCEDURE

S.O.P. No. MLD 005, Rev. 6.1 - Metal Analysis by Atomic Absorption Spectrophotometry

SCOPE

This document details the analysis of lead (Pb) and chromium (Cr) by atomic absorption (AA) spectrophotometry.  The TSP filter extraction procedure is also suitable for analysis of dilute-acid soluble arsenic (As), beryllium (Be), and cadmium (Cd).  This method is currently used for determining the concentration of dilute-acid-soluble Pb collected on Total Suspended Particulate (TSP) glass micro-fiber filters.  This method is also in use for determining the total Cr concentration of source emission samples collected in 0.1 N (Normal) sodium bicarbonate (NaHCO3).  This method specifies the use of graphite furnace atomic absorption (GFAA) spectrophotometry.  Flame atomic absorption (Flame-AA) is an acceptable alternative for analysis of samples with concentrations expected in the parts-per-million (ppm) range or higher.

SUMMARY OF METHOD

Pb from TSP samples are collected over a 24-hour period by exposing a glass micro-fiber filter, sized 8" x 10", to an ambient airflow of approximately 1600 cubic meters (m3). A section, sized 1 ¾" by 4 ½", is cut from this exposed filter. Metals deposited on this section are extracted by dilute nitric acid using sonication with heating. The extraction solution is vacuum filtered, bottled, and stored at room temperature until Pb analysis by GFAA.

Total Cr from Source Testing Emission samples are collected at the source using “Method 425, Determination of Total Chromium and Hexavalent Chromium Emissions from Stationary Sources,” July 1997. An aliquot of the refrigerated NaHCO3 sample solution is acidified using ultra pure grade nitric acid, degassed by manual agitation via pipette, and analyzed for Cr-Total by GFAA.