A PORTABLE TUNGSTEN COIL ATOMIC EMISSION SPECTROMETER WITH TWO COILS

Tungsten coils have been employed recently in instruments that may be used for field applications. Intense emission signals and g/L limits of detection (LOD) have been observed for alkali metals, alkaline earth metals, and some lanthanides (such as Yb and Eu). However, for many transition elements, relatively high LODs are observed due to the insufficient excitation energy provided by the coil at high temperature. In this study, two tungsten coils are employed in an attempt to increase the emission signal and lower the LOD. A lower coil is heated to vaporize the sample, and then a second upper coil is heated at high temperature to excite the sample atoms. The emission signal is viewed above the upper coil. Six test elements (Co, Fe, Ag, Cu, Cr, and Yb) are used to compare the performance with one and two coils. Double tungsten coil atomic emission is reported for the first time for all six elements. Addition of the second coil improved the LOD by a factor of 70 for Cu and Ag; a factor of 40 for Co; a factor of 12 for Fe; and a factor of 2 for Cr and Yb. All six elements can be determined in one simple spectrum with the two-coil system. Cobalt, Fe, Cr, and Cu were determined in a certified polluted water reference sample to evaluate the accuracy of the system. Recoveries were in the range of 93-102% for all elements.