Portable, battery-powered, tungsten coil atomic absorption spectrometer for lead determinations

A compact, inexpensive atomic absorption spectrometer has been designed, constructed, and evaluated for the determination of lead at the mu g/L level. The new device is made feasible by the combination of a reliable tungsten coil atomizer, a miniature spectrometer/charge-coupled device combination mounted on a PC card, and a near-line background-correction method. The finished spectrometer can be powdered by a normal 12-V car battery, controlled with a laptop computer, and transported in any automobile. The overall dimensions of the original prototype system are 19 in. x 8 in. x 3 in. (excluding the computer), and it has no moving parts. The total estimated cost of the system including the computer is less than $6000. The limit of detection for Pb is 20 pg (20 mu L sample volume), the linear dynamic range is two orders of magnitude, and the precision for the technique is 5% RSD at concentrations ten times greater than the detection limit. The accuracy of the technique was determined with the use of NIST SRM #1579a ''Powdered Lead-Based Paint'' containing 11.995 wt % Pb and NIST SRM 955a ''Lead in Blood'' containing 54.43 mu g/dL Pb. The accuracy for the paint sample was 95.1% (11.41 wt % found) with the use of the calibration curve method (aqueous standards) and 97.2% (11.66 wt % found) with the method of standard additions. The accuracy for the blood sample was 93.5% (50.9 mu g/dL found) with the calibration curve method and 96.6% (56.3 mu g/dL found) with the method of standard additions. The limiting source of noise for the instrument is detector noise, so that the performance of the device can be improved by increasing the optical throughput of the system.