Definition, Stages and Training

Stages of a Trace Analysis

1. Planning - Prepare a plan that considers the objective. Planning should begin with a discussion between the analyst and the initiator during which all possible problems are defined. The analyst is responsible for method selection or development.
2. Sample Collection and Storage - Ideally the analyst is involved in this stage, but if not, the analyst should be informed of the sampling procedure at the very least. Sample representation and contamination issues must be considered.
3. Sample Preparation - Contamination issues are a major concern during this stage, but not the only concern.
4. Sample Measurement - The major concerns during this stage are:
   1. Availability of Certified Reference Materials for method validation, plus stable and accurate calibration standards, interference standards, and quality control standards.
   2. Achieving the required precision. It serves no purpose in acquiring a precision that has been reduced to less than one-third of the sampling error. In situations where the sampling error is small and the highest level of precision is required, the analyst faces a difficult task in acquiring precision equivalent to classical wet chemical techniques.
   3. Obtaining the required sensitivity and determining the detection limit of the measurement.
   4. Overcoming interferences using ICP-OES that include matrix differences between standards and samples; spectral interferences (i.e. - direct spectral overlap, wing overlap, interference with background point); chemical enhancement of atom lines by high matrix element compositions (axial view); and drift due to nebulizer plugging, changes in sample argon, power supply instability, or room temperature changes.
   5. Overcoming interferences using ICP-MS that include matrix differences between standards and samples; mass-discrimination effects; isobaric interferences; detector dead-time; and drift due to nebulizer plugging, changes in sample argon, power supply instability, or room temperature changes.
5. Calculating and Reporting the Data - Working with error budgets and calculating the uncertainty is the trickiest part of this stage. An article entitled Understanding Error Budgets is available online as an additional reference.

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