Microliter sample introduction into an inductively-coupled plasma by electrothermal carbon cup vaporization

An atomic emission spectrometric system is described for quantifying trace elements in microvolume samples. The system involves vaporizing the sample by electrothermal carbon cup vaporization followed by the atomization and excitation of the vapor cloud in an inductively coupled plasma (i.c.p.). The detection limits for 21 elements in 10-μl samples are at ng ml^-1 and sub-ng ml^-1 levels with linear dynamic ranges of over four orders of magnitude. Carbon cups coated with pyrolytic graphite are overcoated with tantalum carbide. These cups have resulted in improved detection levels (performances) for Al, As, Bi, Co, Cu and Sn relative to those not containing tantalum. However, cups not treated with tantalum are superior for Au, Cd, Ge, Hg, K, Li, Mg, Mn, Rb and Zn. Comparisons between the two types of carbon cups are presented and discussed. Results also are compared with literature values available for other electrothermal vaporization systems.