PORTABLE, BATTERY-POWERED, TUNGSTEN COIL ATOMIC-ABSORPTION SPECTROMETER FOR LEAD DETERMINATIONS

A compact, inexpensive atomic absorption spectrometer has been designe d, 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 rel iable tungsten coil atomizer, a miniature spectrometer/charge-coupled device combination mounted on a PC card, and a near-line background-co rrection 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 sy stem are 19 in. x 8 in. x 3 in. (excluding the computer), and it has n o moving parts. The total estimated cost of the system including the c omputer 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 magnit ude, and the precision for the technique is 5% RSD at concentrations t en times greater than the detection limit. The accuracy of the techniq ue was determined with the use of NIST SRM #1579a ''Powdered Lead-Base d 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 9 5.1% (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 sta ndard 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 n oise for the instrument is detector noise, so that the performance of the device can be improved by increasing the optical throughput of the system.