Development of a portable, inexpensive, tungsten coil atomic absorption spectrometer for lead determinations

An inexpensive, portable atomic absorption spectrometer has been developed. The device has a simple optical arrangement, and it has been characterized using a tungsten (W) coil atomizer. The W coil is removed from a 150 W projector bulb, and it is powered with a 12 V car battery. The coil is enclosed in a glass cell with quartz windows, and it is kept in a reducing atmosphere (10% H{dollar}sb2{dollar} in Ar). The temperature of the coil is set by a computer-controlled adjustable-current power board driven by a 12 V car battery. A single coil can withstand 200 atomization cycles at the Pb atomization temperature. Radiation from a normal Pb hollow cathode lamp is focused through the atomization cell using a single 2" focal length lens. The lamp may be powered by a simple dc-dc converter that accepts the 12 V input from a car battery and supplies a nominal 300 V to the lamp. The output is current-regulated and adjustable across the range 5-20 mA. The unabsorbed radiation is then focused onto the front end of a 200 {dollar}mu{dollar}m fiber optic cable using a second 2" lens. The opposite end of the fiber optic cable acts as the entrance aperture for a small charge-coupled device (CCD) spectrometer mounted onto a PC card (Ocean Optics Model PC-1000). The detector operates on the computer's internal power supply.; A calibration curve has been obtained for Pb with a coil current of 5.9 A (2600{dollar}spcirc{dollar}C), a coil height of 2 mm, a sample volume of 20 {dollar}mu{dollar}L, and a detector integration time of 163 ms. The limit of detection (3{dollar}sigma{dollar}) observed is 1 {dollar}mu{dollar}g/L (20 pg), and is linear up to concentrations of 200 {dollar}mu{dollar}g/L. The precision observed for these standard solutions is typically 5% relative standard deviation (RSD).; The work presented within the scope of this dissertation clearly demonstrates the feasibility of a portable, inexpensive, tungsten coil atomic absorption spectrometer for Pb determinations. The near-line background correction proves to be an accurate correction technique, especially with samples where background absorption poses a potential interference (paint, soil, and blood). Detection limits (20 pg observed) approaching those commonly associated only with graphite furnace atomization (reported 5 pg) can be achieved with only a 12 V car battery as the system's power supply.