ELECTRICALLY HEATED WIRE-LOOP, IN-TORCH VAPORIZATION SAMPLE INTRODUCTION SYSTEM FOR INDUCTIVELY-COUPLED PLASMA-ATOMIC EMISSION-SPECTROMETRYWITH PHOTODIODE-ARRAY DETECTION

A new sample introduction system that can be used for the analysis of microliter volumes of liquids by inductively coupled plasma atomic emi ssion spectrometry (ICP-AES) is described. The system consists of an e lectrically heated W wire-loop which is attached to a thermocouple cer amic insulator. Ceramic and wire-loop are inserted manually into the c entral tube of a modified ICP torch, with the top of the wire-loop pos itioned about 10 cm below the plasma. An inexpensive variac, which plu gs into a wall socket, is used as a power supply. This in-torch vapori zation (ITV) sample introduction system was characterized using an ICP optical emission spectrometer with a photodiode array detector. In th is pilot study aimed at testing the validity of the approach, spectral interference effects arising from W emission lines are documented for Be, Cu, Mn, Sc, Sr, V, Y and Zn and preliminary analytical performanc e characteristics using an unoptimized wire-loop/torch design are pres ented. Calibration curves were linear for over three orders of magnitu de for Sr, Y and Be; the non-linear calibration curves obtained for Cu were attributed to contamination from the power transfer cables, for Mg to contamination from the ceramic and for Ca to airborne particles adhering to the wire-loop. As well, Au-coated W wire-loops proved to b p sensitive to Hg-0-vapor in air. Precision varied between 1.9 and 4.5 % (10 mu l injection of single element standards) and, estimated absol ute detection limits were (in pg) Zn (710), V (20), Mn (10), Y (10), S c (9), Be (1) and Sr (0.4).