INFICON Explorer Portable Gas Chromatograph - Manual (Page 303)

Explorer Operator Manual
301
Accurate Concentration Measurement
The following information is provided to assist you in understanding some of the
analytical issues regarding the analysis of your target compounds in ambient air.
When you are detecting compound concentrations in air samples using gas
chromatography, it is important to recognize that there are various potential sources
of error in the measurements. These sources of error combine to give scatter in
measured concentrations (measured as precision) and systematic bias to measured
concentrations. You must correct for these sources of error or your results will
become inaccurate.
Possible sources of error include:
Peak integration errors.
Sampling errors.
Compound dependent adsorption effects.
Detector response drift over the period of time since the last calibration.
System accuracy.
All of these effects may contribute to inaccurate measurements in any given set of
data.
Peak Integration Errors
Baseline noise, interfering peaks or excessive tailing of the target compound peak
can cause problems in starting or stopping the peak integration at the optimum
times. These can even cause differences in integration for consecutive runs at the
same concentration. Selection of one set of integration parameters over another may
result in a nonlinear area versus concentration curve.