August EWJ 24 - Flipbook - Page 38
Treatment of Glass Sampling
Containers to Determine Trace
Amounts of Accelerants in Fire Samples
by Petra Bursíková, Milan Ruži ka, Ondrej Suchy
Ministry of the Interior, Directorate General – Fire Rescue Service of the Czech Republic,
Technical Institute of Fire Protection, S. Písková 42, 14300 Prague 412, Czech republic
The Technical Institute of Fire Protection (TIFP) is a
part of the Fire Rescue Service of the Czech Republic.
TIFP deals with testing and certification of fire equipment, fire investigation and applied research and
development in the field of fire science.
separated by their physical and chemical properties,
for example boiling point. A mass spectrum is measured for each substance, based on which they are
compared with already measured spectra in the spectrum libraries, and thus the substance essence of the
accelerant is determined.
Fig. 1. Adsorbing the sample onto SPME fibre.
The purpose of our research is to help (not only) our
investigators. They often go to a fire scene and try to
find the place where the fire started and the reason of
fire. In many cases, the fire is founded intentionally
by arsonists. Arsonists very often use substances supporting combustion (fire accelerants). The fire investigators take the samples of fire debris to our
laboratory to confirm/disprove the presence of fire accelerants. For this purpose, we use gas chromatography to prove the presence of small amounts of
organics trapped on solid samples or in liquid samples. Demonstrating the presence of traces of gasoline
or diesel fuel can significantly support the hypothesis
that a fire was started intentionally [1]. Recently, with
the development of gas chromatography instrumentation, the sensitivity of the measurement has increased and it is possible to measure lower
concentrations. Therefore, it is important to collect the
sample correctly, use clean sample containers, collection tools and equipment and prevent contamination
of the sample during transport to the laboratory [2],
[3].
For transport of samples, different containers are
used. The most typical containers are metal cans, vials,
sampling bags and glass containers. Glass containers
with TWIST OFF lids were confirmed as the best container according to previous studies [2], [4], [5]. The
biggest advantage of the container is in good protection against contamination due to an airtight lid.
Clean, new 720 ml glass sampling containers with a
TWIST OFF cap were used for testing. For the purposes of testing, we chose six different types of lids –
original, white pasteurized, white sterilized, gold
pasteurized, gold sterilized and silver sterilized lids.
The empty sampling container was placed in a hot air
drying oven and heated at 60 °C for 15 minutes. Then
the lid was pierced and the SPME fibre was inserted
into the opening and exposed in the space of the
sampling container for 20 minutes at 60 °C. This was
followed by placing the adsorbed SPME fibre into
the chromatograph inlet (Tinlet = 260 °C) and
chromatographic analysis with mass spectrometry.
The contribution deals with the testing of the cleanness of glass sample containers and suggests their
cleaning procedures. Gas chromatography with mass
spectrometry and solid phase micro extraction
(GCMS-SPME) was used to detect contamination in
new preserving jar with TWIST OFF caps. By testing
different types of lids from different manufacturers, it
was found that all of them are already contaminated
with similar substances to varying degrees. Various
methods of cleaning were tried, namely burning,
using sorbent materials and cleaning with solvents.
Based on these results, a procedure for their cleaning
was proposed.
The aim of this work was (1) determination of the
contamination of sampling containers and (2) to propose a procedure for cleaning of sampling containers.
For the first aim (determination of the contamination),
new lids without any treatment were used. The
experiments were performed three times to be sure
the results were correct and reproducible. The second aim (a procedure for cleaning) required the
treatment of the lids. Two methods for cleaning were
proposed. The first method was based on
thermal/heat cleaning. The lids were placed into a
Experimental setup
Contamination of the collection containers was
detected in new sample containers with TWIST OFF
lids by gas chromatography (GC) with mass spectrometry (MS TOF) and solid phase micro extraction
(SPME), see Fig. 1. Pegasus BT2 instrument was used
for chromatographic analyses. The result of gas
chromatography is a chromatogram with substances
EXPERT WITNESS JOURNAL
36
AUGUST 2024
