Plasma-cavity ringdown spectroscopy (P-CRDS) for elemental and isotopic measurements

Plasma-cavity ringdown spectroscopy ( P-CRDS) was. rst introduced for trace elemental measurements in 1997. During the last decade, this technique has rapidly advanced from the initial demonstration of the basic concept to the latest ( prototype) instrumentation. P-CRDS has been demonstrated to be a powerful technique for ultra-sensitive elemental and isotopic analysis of trace metals, radionuclides, and isotopes existing in solid, vapor, and/or liquid phases. Utilizing various plasma sources, such as an inductively coupled plasma ( ICP), a microwave-induced plasma ( MIP), and a tube-shaped MIP, and different laser sources, namely, pulsed and continuous wave lasers, several elements and isotopes, including Pb, U-238, U-235, Hg, Sr, and Mn, as well as the. ne structures of Hg, have been measured with P-CRDS, and the detection limits have ranged from mu g mL(-1) to pg mL(-1) levels. This paper presents a critical review of the P-CRDS technique with an emphasis on its application in elemental and isotopic analysis. Some critical issues encountered in the application of P-CRDS and its technological development during the last ten years, such as sensitivity, spectral interference, plasma optimization, evolution of plasma sources, laser beam behavior in the plasma, laser source effects, and instrument configurations are discussed. Technological and scientific barriers to be overcome for eventual instrumentation in the field of atomic/ isotopic spectrometry, including ( 1) portable UV laser sources, ( 2) novel plasma sources, and ( 3) detection of multiple analytes, are also discussed.