Chapter 6 methods, 1 introduction to methods, 1 sensitivity – INFICON HAPSITE ER Chemical Identification System User Manual

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HAPSITE ER Operating Manual

Chapter 6

Methods

6.1 Introduction to Methods

The versatility of the HAPSITE lies in the variety of methods available. The
HAPSITE can be run in Analyze (GC/MS) mode or Survey (MS only mode) and
uses various sampling accessories to extend its capabilities. The accessories
include the Concentrator, the Headspace Sampling System and the SituProbe.
This chapter describes the various sampling methods.

6.1.1 Sensitivity

The sensitivity of the HAPSITE is dependent on the configuration and sampling
mode chosen. The Survey Mode is the least sensitive, requiring levels of greater
than 1 ppm (parts per million) for detectability. With a Concentrator installed and
using the probe, the HAPSITE can detect low ppb (parts per billion) to high ppt
(parts per trillion) levels.

6.1.2 Survey Method

Survey is used to quickly screen a location for volatile compounds. The sample is
drawn in through the probe and sent directly to the Mass Spectrometer. It bypasses
the GC to provide a quick response. The Survey mode of sample collection is also
referred to as MIMS (Membrane Interface Mass Spectrometry).

There are two ways the Survey Methods can provide tentative identification of
compounds. They can either extract target mass spectra from the MS response or
search the total MS response against the AMDIS or NIST library. Survey Methods,
when run from the HAPSITE, also provide an indication of the concentrations of
VOCs based on the response of the TIC (Total Ion Count). The LCD of the
HAPSITE provides a real time plot of response vs. sampling time. Survey Methods
can be Selected Ion Monitoring (SIM) or Full Scan methods. The sensitivity of a
Survey method in full scan will be approximately 1 ppm or greater. A Survey SIM
method gives an improved level of sensitivity compared to a Full Scan method.

NOTE: These sensitivity ranges should be viewed as general guidelines, as the

sensitivity of individual compounds can vary.