Analysis of environmental lead contamination: comparison of LIBS field andlaboratory instruments

The Army Research Office of the Army Research Laboratory recently sponsored the development of a commercial laser-induced breakdown spectroscopy (LIBS ) chemical sensor that is sufficiently compact and robust for use in the fi eld. This portable unit was developed primarily for the rapid, non-destruct ive detection of lead (Pb) in soils and in paint. In order to better charac terize the portable system, a comparative study was undertaken in which the performance of the portable system was compared with a laboratory LIBS sys tem at the Army Research Laboratory that employs a much more sophisticated laser and detector. The particular focus of this study was to determine the effects on the performance of the field sensor's lower spectral resolution , lack of detector gating, and the multiple laser pulsing that occurs when using a passively Q-switched laser. Surprisingly, both the laboratory and p ortable LIBS systems exhibited similar performance with regards to detectio n of Pb in both soils and in paint over the 0.05-1% concentration levels. T his implies that for samples similar to those studied here, high-temporal r esolution time gating of the detector is not necessary for quantitative ana lysis by LIBS. It was also observed that the multiple pulsing of the laser did not have a significant positive or negative effect on the measurement o f Ph concentrations. The alternative of using other Ph lines besides the st rong 406-nm line was also investigated. No other Pb line was superior in st rength to the 406-nm line for the latex paint and the type of soils used in the study, although the emission line at 220 nm in the UV portion of the s pectrum holds potential for avoiding elemental interferences. These results are very encouraging for the development of lightweight, portable LIBS sen sors that use less expensive and less sophisticated laser and detector comp onents. The portable LIBS system was also field tested successfully at site s of documented Pb contamination on military installations in California an d Colorado. (C) 2001 Elsevier Science B.V. All rights reserved.