Linearity and Detection Limits

Overview

The next few parts of this guide will provide practical information for the operator in the realization and demonstration of the key performance characteristics designed into their ICP by the manufacturer.

I have personally had the opportunity to see the advancement of ICP instrumentation over the past 30 years. Current instrumentation and software provided by manufacturers has gone well beyond anything I could have imagined 30 years ago (and it costs less). In 2004 it takes $3.21 to purchase what cost $1.00 in 1975, yet during this time period the price of ICP instrumentation has gone down while the performance characteristics have improved by orders of magnitude. A ‘personal experience’ example is the detection limit for K by ICP-OES that has gone from 0.4 ppm to 1 ppb where the 0.4 ppm detection limit was measured on an instrument that in 1975 cost 1.5 times the 2000 price of the instrument that measured the 1 ppb detection limit (taking inflation into account, the 2000 price would be one fifth the 1975 price).

Although an ICP instrument can be wheeled into a laboratory and begin collecting data the same day, the operator is encouraged to realize and demonstrate the key performance characteristics of linearity, detectability, and spectral integrity and then go on to make decisions based upon the boundaries of these performance characteristics and the limitations of the analytical problem. Defining and being able to realize your instrument’s performance characteristic is an investment that will save time over the years to come and allow you to make the right choices.

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