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GC-MS Analysis of Bunkers

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.

Continue reading GC-MS Analysis of Bunkerslinkedin

Fire Debris Analysis – Self Heating – 1st June 2022

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.linkedin

Boiler Condensate Analysis

We are proud to now be able to offer a range of analyses and consultancy to support the condensing boiler manufacturing industry as they switch from gas and kerosene to alternative fuels such as hydrogenated vegetable oils (HVOs).

Over the last year have been working with a key player in the industry to help show that the newer fuels types are producing condensates that are acceptable.

To check out your boiler condensates for problems we offer a range of analyses is including pH, total acidity, particulate analysis, residual fuel analysis, corrosion analysis as well as selected anions and cations quantification.

See the following page links on our web site for more information boiler condensatesindustries

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ISO9001:2015 Certification Renewed

We are very pleased to announce that SMS Analytical Ltd has just renewed its ISO9001:2015 certification following another successful full audit by SGS, our accredited certification body. Our certificate is available for inspection by clicking on the SGS Certificate logo at the top right of our website: www.smsanalytical.com.

Our thanks go to our customers and in particular to those who have helped us prepare for the SGS audit by themselves visiting and auditing us earlier in the year.

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Water Content Apparatus

We have a new method for the determination of water in various materials.

It is based on the Dean and Stark method and uses a mixture of Toluene and mixture of Xylenes to carry the water over into a graduated receiver vessel where the water appears as a layer below the lighter solvent.

Hint: hover over the following images for zoom in and move around.

Dean and Stark recovery testing

Recovery testing using known % of water.

The sample (last image) shows the collected water as lower phase after about 3 hours of distillation.  In this case, a very small drop of methylene blue was added to the receiver afterwards to aid the visualisation.

Dean and Stark Distillation

The technique is quite tricky to get right and requires some practise.  In order to get a good recovery a long wire can be inserted from the top of the condenser and by twisting the wire against the droplets the water they are encouraged to coalesce and drop to the bottom of the receiver to join the rest of the water.  This is illustrated by the tiny remaining traces of blue still on the sides of the receiver in this case.linkedin

HPLC – Chemical Analysis Available

Exciting news for Christmas: SMS now have a High Performance Liquid Chromatography (HPLC) system to complement the existing range of other chromatographic techniques that we offer our customers.

The HPLC system comprises Pump with ternary solvent input, solvent de-gasser, UV detector, column oven and data system. Future expansion options might include a Fluorescence detector.

Examples of additional types of work we can now offer include:

  • Euromarker detection in Gas Oils (e.g Red Diesel) and kerosene
  • PAH analysis
  • identification of oxidation products from antioxidants used in polymers which can cause discoloration issues

HPLC System

SMS Analytical’s HPLC System

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Sample Retention in Nylon Evidence Bags

Nylon bags are frequently used in fire investigations to preserve samples such as fire debris for later analysis. They are considered to have very good resistance to vapour loss [1]. However, this does not mean that they hold onto all vapours forever, and this could make the difference between detecting accelerants or not, or mis-identifying the type of accelerant.

We showed in an earlier blog the type of profile seen for petrol (gasoline) vapours. Petrol and volatile solvents, such as naphthas are the most vulnerable to vapour loss because the molecules are very small and can diffuse through the polymer into the air.

We used bags from 2 different suppliers, adding 1µl of a synthetic mix of hydrocarbons in the gasoline boiling range to dry cellulose fabric, sealing the bag with a ‘swan-neck’ cable tie closure and encasing the bag with a second bag, also sealed with a swan-neck closure. The bags were then stored at ambient temperatures and the atmosphere inside each inner and outer bag tested after 20 days.

We used a synthetic mix in order to see if particular types of hydrocarbons migrated through preferentially.
This is the headspace GC-MS chromatogram of the synthetic mix (red chromatogram), showing C0-C3 aromatics (benzene through to trimethylbenzene) in the green chromatogram, alkanes from C5 pentane to C12 dodecane (purple chromatogram) and cycloalkanes and alkenes (C5 to C8) in the black chromatogram. The total aromatics content of the mix was 34%, similar to petrol.

 

Hydrocarbon synthetic mix

 

Hydrocarbon GCMS

Here are the chromatograms of the vapour from the inner and outer bags after 20 days ambient storage.

Hydrocarbon sampled from bag1 after 20 days

Nylon Bag 1

Hydrocarbon sampled from bag2 after 20 days

Nylon Bag 2

The red chromatogram is vapour from the Inner bag and the green chromatogram is for vapour sampled from the Outer bag.

After 20 days the levels of vapour in the inner bags were significantly lower than the vapour concentrations immediately after sealing the bags. The concentration of vapour in the outer bags was lower than for the inner bags and there appears to be a preferential loss of aromatic hydrocarbons. This could affect the interpretation of the analysis as the presence of the C1 and C2-benzenes in particular helps to define whether petrol (gasoline) is present or not.

In both the types of nylon bags used, volatile hydrocarbons permeated or diffused  through to the outer bag, and onwards to the atmosphere from the outer bag. But is this because of the inefficiency of the swan-neck closure, allowing volatiles to escape from the bag, or are the hydrocarbons permeating through the polymer bag itself ? [2]. We will be examining this in our next blog on this subject.

To summarise, it is best if analysis of fire debris for accelerants is carried out as soon after sample collection as possible. Contact SMS Analytical to discuss our rapid accelerant testing service.


References:

[1] E. Stauffer, JA Dolan, R Newman: Fire Debris Analysis, Academic Press, Elsevier, 2008

[2] Strijnik and Hong-You: Evaluation of the Effectiveness of Nylon Bags as Packaging for Fire Debris, 2004, Proceedings of 56th Annual Meeting of the American Academy of Forensic Sciences.linkedin

Kerosene and Diesel Fuel Analysis By GCMS

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