Analysis Method For Confirmation - Dräger DrugTest 5000 Manuel Technique

Appendix
9.2

Analysis method for confirmation

The Dräger DrugTest 5000 principle is based on the so-called
antigen-antibody reaction. Here the antibody specifically binds
with its "paratop" the corresponding "epitop" of the antigen.
This bond which is facilitated by hydrogen bridge bonds, ionic
bonds, hydrophobic interactions and van der Waals forces is a
balance reaction which is accordingly subject to the law of
mass action. With a sufficiently optimised test system it is
possible – in dependence on the antigen – to prove them in the
femtomol range and even quantify them
9.2.1 Why confirm?
State-of-the-art immunological testing procedures – especially
screening test kits – are designed to make sure that from a
defined substance concentration a positive result with a
probability of >90 to 95 % is actually positive
The remaining "vagueness" of this analytical statement and
the fact that immunochemical screening results are also
affected by cross-reactivity and interferences of other –
possibly chemically very similar – substances must always be
considered. Positive results must be confirmed by a second,
independent procedure
chromatography (GC) or liquid chromatography (LC) with
subsequent mass spectrometry (MS). Within the scope of
mass screenings and
recommended to conduct a defined random sample (e.g. 10 to
20 %) of the negative results on site with the help of GCMS or
LCMS.
9.2.2 Chromatography
The term chromatography comprises physical methods
whereby substances are separated by distribution between a
static (stationary) and a moving (mobile) phase.
9.2.3 Gas chromatography
GC is a very efficient separation method whereby a dissolved
mixture of substances (the sample) is guided with the aid of a
stream of gas (mobile phase) over a stationary phase. In doing
so the sample is split into its individual components. The inert
carrier gas is normally helium.
The stationary phase consists of a 10 to 50 m long quartz
column with an internal diameter of 0.2 mm which is charged
on the inside with an especially thin film of a separating
material. The individual components of the sample leave the
separating column after a specific period of time (retention
time) and can then be analysed by a sensitive detector.
In the field of drug analysis a mass spectrometer has been
successfully connected in series for many years for this
3)
purpose (GC/MS) .
9.2.4 Mass spectrometer
Mass spectrometers consist of an ion source in which gaseous
molecules are ionised, a mass analyser separating ions
1) Polzius, R. and Manns, A., (2002) Dräger booklet 373, p. 23-28
2) Luttmann, W. et al. (2006) The experimenter, immunology,
Elsevier GmbH Munich
3) Schwedt, G. (1992): Pocket atlas of analytics, published by Georg
Thiem, Stuttgart
30
1)
.
2)
.
such as, for example,
screening programmes
according to their mass/valency ratio (m/z) and a detector
counting the number of generated ions. As result of the
analysis a characteristic mass spectrum is generated for each
substance which shows which ions have been formed in which
relative quantities. This allows a definite analyte identification.
gas
it is
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