Flameless atomic absorption spectrometry is a sensitive, rapid, selective and precise technique which is very attractive for the routine analysis of small liquid and solid samples. Little pretreatment of the samples is necessary, so that the risk of contamination is small. Recently, this technique has been applied by Omang' and by Woodriff and Lech' to the determination of lead in atmospheric particulates.
In the presenf study the optimal conditions for rapid atmospheric analysis were determined. Aerosols were collected by passing air through a cellulose filter. A fraction of this filter was subjected to ultrasonic vibration in a suit&le solvent to remove the particulate matter. The-lead content of this solution was determined directly by atomic absorption with a Massmann oven. This method has a routine sensitivity for lead of 0.01 pg rnN3 of air for one-eighth of a 24-h filter. c
EXPERIMENTAL
Apparatus arid instrll#l~nt settings
All measurements were done with a Perkin-Elmer Model 303 double-beam atomic-absorption spectrophotometer, equipped with a Perkin-Elmer HGA-70 graphite cell, a deuterium background corrector, i Hitachi-Perkin-Elmer recorder Model 159 and an Intensitron lead hollow-cathode lamp. Optimal operating conditions were found to be as follows: lamp current 40 mA, slit 4, monochromator U.V., wavelength 283.3 nm, program 2 (drying at 100") or program 5 (drying at 100" and charring at 490") and an atomization ' voltage of 9 V (24OOO). Samples of 10-50 ~1 were injected into the graphite tube with Eppendorf micropipettes. Ultrasonic removal of the lead from the filter was carried out with a Branson ultrasonic cleaner, consisting of an ultrasonic generator Model LG-150 and an ultrasonic tank-type transducer LTH-60.
The low-temperature asher was from International Plasma Corporation. The working conditions were as follows: temperature below lSO", oxygen flow 60-70 cm3 min-i, pressure 1 mm Hg, ashing period 1 h. The ash was dissolved in LOO ml of 0.1 M nitric acid.
Reagents and solutions
Merck Suprapure nitric acid (14 M) was diluted to 0.1 M. The lead stock