Category Archives: GCMS

Reasons why you should use us for Fire Debris Analyses

Blog GCMS Self Heating Oils No Comments

When vegetable oils self-heat, the first chemical compounds to diminish in concentration are the polyunsaturated fatty acids (PUFAs) such as linoleic and linolenic acids. At high temperatures or under prolonged heating the PUFAs can diminish to the extent they are no longer detectable. The presence of PUFAs in the analysis of fire debris is an essential element in determining whether self-heating is a possibility or not      (e.g. ASTM E2881). Once PUFAs have reacted, additional means of characterising the oils or fats present are needed.

PUFA comparison

Chromatograms of rapeseed oil prior to heating (green) and after heating (red) showing loss of PUFAs (peaks between 24.45 and 29 min)

 

SMS Analytical have been identifying some oxidation products of PUFAs in fire debris to help us establish whether any oils and fats that are present are capable of self-heating. We are continuing to improve our analyses and interpretation of results to provide more detailed reports for fire-related problems.

Contact us to discuss ways we can assist in fire debris analyses

 

 

 

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Don’t Leave Your Tumble Drier On Unattended!

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SMS Analytical have had an increasing number of cases relating to tumble drier fires in the last couple of years but these are not related to electrical faults like those with the subsequent recall shambles seen a few years ago. In these particular cases Fire Investigators pass the remains of semi burnt fabrics on to us for analysis of residual fats/greases/oils.

We provide a comprehensive report detailing any tiny traces found. The fire can be caused by particular chemical reactions of residual oils/fats with oxygen in the air, aided by some heat. I suspect this may be partly because of lower temperatures used in ‘Eco’ wash cycles, leaving traces of residual oils/fats which can lead to auto-oxidation reactions, causing self heating and then increased chances of a fire. Some oils are much more likely to cause this, their class is referred to as ‘drying oils’ and includes Rapeseed, one of the most commonly used cooking oils. Even after the drier has finished there may still be a critical core of heat within a stack of fabrics, containing residual oils, so best open and allow to cool after it finishes.

The general advice is not to overload the washer/drier and ensure a sufficiently high temperature is used to remove all oils before tumble drying and use regularly cleaned lint-trapping filters.

Which have provided a useful guide: Section 5 relates to oils.

Never leave a drier on unattended overnight. Sleep tight!

For more information visit our website https://www.smsanalytical.com or give us a call on +44(0)333 3580037

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Fire Debris Analysis – Self Heating – 1st June 2022

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BBC Reported Fire

Image Copyright BBC

A large scale laundry fire was recently reported by BBC, luckily no casualties, but the business will take considerable time to be re-established. No doubt fire investigators are working to determine the cause(s) – self-heating through oils/fats in fabric, lint, electrical or other?

At SMS Analytical we have recently received a number of laundry fire related samples for analysis. The causes of such fires is obviously of considerable interest.

Cotton- and linen-containing fabrics can retain significant quantities of oil even after washing at 40°C. The chemical composition of the oil is important if self-heating is to occur : polyunsaturated fatty acids (PUFA) facilitate self-heating.

Analysis of the fire residues can reveal a fatty acid profile which can give indications as to whether self-heating has occurred. Although once self-heating starts, there is a change in the fatty acid profile of the oils, with preferential loss of PUFAs. The analysis gives a snapshot of the composition of the oil after the fire so other information may be needed to confirm whether self-heating is a possibility.

We are undertaking a series of experimental analyses to get an idea of how quickly the fatty acid profile can change with time and temperature, which will be the subject of a later post.

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GC-MS Analysis of Bunkers

Blog GCMS spectroscopy No Comments

There has been much discussion recently on LinkedIn (see ref 1 and ref 2) about using GC-MS to analyse marine bunker fuels and whether this should be a routine test.

Firstly GC-MS is a fairly generic term covering a variety of techniques within that label such as

  • Headspace GC-MS
  • Direct Injection GC-MS
  • Direct injection GC-MS with derivatisation of the sample
  • Sample extraction with or without sample derivatisation GC-MS (“polars” analysis)

All of these will provide some information about the composition of the fuel, but none will provide every bit of compositional information.

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Kerosene and Diesel Fuel Analysis By GCMS

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In this article we show how we examine Kerosene  and Diesel fuel using GCMS.

Kerosene

Here is a typical chromatogram of a kerosene using a Mass Spectrometer as the detector. The number and distribution of the peaks forms a fingerprint of the fuel.

The chromatogram shows all the major peaks showing that this kerosene has an alkane range from heptane (C7) to hexadecane (C16). Kerosene contains different types of hydrocarbons: alkanes (or paraffins), cycloalkanes (also called naphthenes) and aromatics.

We can use selective ion monitoring to separate out these different classes of compounds.

The red chromatogram shows the whole range of compounds in the kerosene. By using selected ions we can see the straight chain and branched chain alkanes (green chromatogram) and the profile of the cycloalkanes (purple chromatogram).

The green chromatogram shows the alkylbenzenes present in the kerosene, ranging from toluene to C6 alkyl benzenes.

Diesel Fuel

Diesel fuel shows a mixture of hydrocarbons with a wider boiling range.

The alkanes in this diesel fuel range from nonane (C9) to dotriacontane (C32). The chromatogram shows an unexpected peak (labelled A). The mass spectrum from this peak identified it as di-octyl phthalate, a common plasticiser often found in plastic containers.

The green chromatogram shows the alkane distribution in the diesel fuel.

Sometimes contaminants are not seen in the main chromatogram because the hydrocarbons overlap the contaminant peak.

Selective ion monitoring can reveal contaminants.

 

The green chromatogram shows the selected ion chromatogram for alkyl benzenes. The peak at 29.24 min is unusual and indicates a possible contaminant. By checking the mass spectrum of this peak against the NIST mass spectral library, we found a match with triphenylphosphine oxide, which is not a normal component of diesel fuel.

The purple chromatogram shows the same peak is present in the chromatogram produced for the two main fragment ions for triphenylphosphine oxide.linkedin