Hanging drop cathode-atmospheric pressure glow discharge as a new method of sample introduction for inductively coupled plasma-optical emission spectrometry

This work reports the use of hanging drop cathode-atmospheric pressure glow discharge (HDC-APGD) as a new method of sample introduction for inductively coupled plasma-optical emission spectrometry (ICP-OES). The developed arrangement was characterized by a low sample uptake (0.56 mL min(-1)) and the fact that the entire sample solution volume was consumed by the discharge. This resulted in a very high transport efficiency of analytes from the sample solution into the ICP torch (usually > 80%). Under the optimal operating conditions of HDC-APGD, intensities of emission lines of studied elements were, on average, 2 times higher as compared to those obtained with conventional pneumatic nebulization (PN). Moreover, in the case of I and Y, the observed signal enhancements were even higher, i.e., 6.2 and 6.1 times, respectively. It was also shown that in the case of B and some elements that are known to form different volatile species (Ag, Bi, Cd, Hg, Os, Pb, and Se), the presence of low molecular weight organic compounds in the sample solution, i.e., CH3OH, C2H5OH, HCOOH, CH3COOH, or HCHO, resulted in the additional enhancement of their signals. It was especially evident in the case of Hg for which a 8.6-fold signal enhancement in the presence of HCOOH was noticed. The system presented herein was distinguished from other competitive APGD-type discharges because it could be successfully used for the determination of a vast group of elements, including alkali metals, alkaline earth metals, transition metals, and non-metals.