Reproducibility, Stability, and Linear Range

The reproducibility of signal intensities and drift times had, before 1990, not been considered widely in reports or journal articles on IMS, possibly since detection limits were the main concern. Consequently, there is only a relatively brief record available in the literature on the repeatability of IMS measurements, which is a key to any quantitative analytical method. The few examples that are available are concerned with short-term repeatability, and the relative standard deviation (RSD) for peak areas in these is between 5% and 25%. In one study with a handheld IMS analyzer, reproducibility was 6 to 21% RSD for 5 to 2,500 ng of dialkylphthalates, as shown in Table 8.2. Measurements of hydrazine vapors at 10 to 200 ppb using the same instrument showed precision of about 3 to 16% RSD for these high-reactive and -adsorptive chanicals.  

A fourth example is for the determination of phenol through thermal desorption from filter paper. The repeatability was 42 to 0.7% RSD in the range of 10 to 10,000 ng, respectively experimental results are shown in Table 8.3 and include errors from sample handling. All of these studies occurred under carefully controlled laboratory conditions. 

Quantitative Response of a Mobility Spectrometer for Thermal Desorption of Phthalate Esters from Filter Paper 

Peak Area Mean Deviation Peak Area Mean Deviation 

Standard deviation includes the sample preparation and thermal desorption steps.  

---