Optimizing an inductively coupled plasma emission spectrometer analysis time with the use of a direct injection nebulizer

An inductively coupled plasma (ICP) emission spectrometer analysis time could be reduced if sample aspiration, spray chamber rinse, and equilibration time could be reduced. The objective of this project was to speed up ICP plant analysis time with a direct injection nebulizer (DIN; Cetac Technologies Inc., 5600 South 42nd St., Omaha, NE 68107) without sacrificing analytical accuracy. Plant samples were digested in a HNO3-H2O2 matrix and analyzed for their sulfur (S), phosphorus (P), potassium (K), sodium (Na), calcium (Ca), magnesium (Mg), zinc (Zn), manganese (Mn), copper (Cu), iron (Fe), boron (B), and aluminum (Al) content using a simultaneous Perkin Elmer Optima 3000 axial ICP. Sample throughput was increased to 5.3 samples per minute. To achieve this speed of analysis, the sample uptake was reduced to 3 sec/sample by using a vacuum pump to pull the sample through the system verses pushing the sample through with a peristaltic pump. Integration time was optimized at 2 sec/sample. Rinse time or equilibration which is usually necessary for normal spray chambers is 0 sec/sample with the DIN. These modifications did not sacrifice analytical quality when compared to referenced plant samples results. The vacuum pump/DIN/ICP system can reduce the normal ICP analysis dead-time to less than 3 sec/sample.