Techniques for Increasing Productivity in ICP Spectrometry

1. Helix O’ring=free Nebulizer fitting EzyFit Zero dead-volume Sample connector Integration AS to sample Rinse AS to rinse Smpl fills line Plasma equil Smpl empties line 7 5 6 3 4 2 1 Techniques for Increasing Productivity in ICP Spectrometry Jerry Dulude, Glass Expansion, Inc., 4 Barlows Landing Rd., Pocasset, MA 02559 Niagara™ Rapid Rinse Accessory BACKGROUND Effect of Sample Introduction Components Software Approaches The Niagara Rapid Rinse Accessory significantly shortens the analysis cycle time of an unattended ICP spectrometer run and as a result achieves higher productivity and faster sample turnaround times. The Niagara begins the rinsing of the nebulizer and spray chamber the instant the sample measurement is completed and continues to rinse until the next sample is ready. Thus the rinse is carried out in the time that is usually wasted waiting for the sample and the rinse solutions to flow from the autosampler to the nebulizer. The Niagara replaces steps 5 and 6 with step 7. The Niagara is controlled by built-in firmware and is triggered by the autosampler. Each kit includes an autosampler kit which has been designed for each of the major autosampler models. As both ICP-AES and ICP-MS spectrometers become more and more an integral part of the production laboratory, the emphasis on productivity is enhanced. This paper will examine a number of ways in which the length of the analytical cycle can be reduced without jeopardizing the quality of the results. These include the selection of the ICP-AES configuration, choice of sample introduction components, and software and hardware approaches for shortening or eliminating the rinse step. Decreasing Dead Volume Fast Pump during Rinse (stages 2, 6, and 7) • Double pump speed during the rinse step. • Pump stays in fast mode until the next sample is ready. • Must add 10 to 15 sec. of equilibration time prior to integration. • Reduces cycle time by 5 to 10% INTRODUCTION The graph below illustrates the stages of analysis for a typical autosampler run on an ICP-AES or ICP-MS spectrometer. Almost all of the stages can be shortened by one means or another. Some of these are dependent upon the specific hardware configuration of the spectrometer and autosampler. Some autosamplers are designed to move faster than others and should be investigated prior to purchase with respect to speed if productivity is an important criterion (stages 1 & 5). For AES spectrometers, particularly, the configuration of the optical and readout systems can significantly affect speed of analysis (stage 4). Dual view (radial and axial) spectrometers take two exposures for each analyses, increasing the integration time. Some chip-based spectrometers must take two exposures to cover the wavelength range of the method. Another aspect to investigate is the readout overhead time which can be significant on various makes and models. This paper will address ways to increase productivity once the spectrometer and autosampler have been procured and installed. The Helix o’ring-free nebulizer fitting eliminates the o’rings that are a source of dead volume. Likewise, the EzyFit eliminates dead volume in the nebulizer sample port. Predictive Rinse NORMAL (30-SEC. RINSE) Sample Mode • Estimate the sample uptake time. • Lift the sipper from sample prior to the measurement. • Conduct rinse and next sample loading during the previous sample • measurement. • Requires good estimates. • May not rinse out high concentration samples. • Not compatible with Auto QC Checking. • Good for crude assays. Niagara achieves 25% reduction in cycle time (all results in ppb) Faster Flows • Small ID pump tubes at fast speed • Small ID capillary tubes • Small ID autosampler probe • Minimize length of sample tubing Rinse Mode NIAGARA (10 SEC. RINSE) Trial performed using Elan 6000 ICP-MS by Gavin Robinson, Hill Laboratories, Hamilton, New Zealand Intelligent Rinse • Determine appropriate rinse based on the last sample. • If all elements below set point 1: NO RINSE • If an element exceeds set point 1 but not set point 2: STD RINSE • If an element exceeds set point 2: MONITOR RINSE SOLN • UNTIL UNDER SET POINT 1 • Excellent for high accuracy analyses. • Little time saving for dirty samples. CONCLUSIONS For greatest productivity for accurate analyses, minimize dead volume on all sample introduction components and combine Niagara with the Fast Pump mode of operation. The entire sample line from the autosampler probe to the nebulizer should be minimized in both length and internal diameter. Sample cycle for unattended ICP sample analysis