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GC/MS & GC/MS/MS Methods
Each sample will benefit from the latest in sample extraction techniques combined with a highly developed GC/MS analysis and detailed interpretation program. This represents the latest in technology. Its development was aided through research sponsored by the National Research Council of Canada. The methods used also comply with ASTM guidelines. Our services have been designed specifically for the needs of the Arson Investigator and have been thoroughly designed through interviews with investigators. This includes the pre-sampling information, detailed chain-of-custody, legal sample tracking, review by a Chartered Chemist, to a concise and carefully laid out final report. Activation Laboratories is a member of the International Association of Arson Investigators, the Canadian Association of Fire Investigators and the Canadian Society of Forensic Science, as well as the American Chemical Society and the American Society for Testing & Materials.
All samples are analyzed by GC/MS as per the latest ASTM guideline for E-1618. Our instrumentation is the most sensitive available. This is important for samples that have been in the field, held in storage for months, and for highly weathered samples. Our interpretation protocol is unparalleled and fully utilizes the power of GC/MS.
ULtraspecific GC/MS/MS for Confirmation of Ignitable Liquids in Weak, Complex or Weathered Samples
To our knowledge our GC/MS/MS confirmation analysis as applied to Fire Debris analysis is a first. As shown at our initial exhibit at the 1997 IAAI conference and presentation at the 1997 CSFS conference, GC/MS/MS has the ability to confirm the presence or absence of gasoline at trace levels lower than GC/MS can detect. This analysis has improved sensitivity, but most importantly, results in new daughter ion mass spectra. This significantly improves the confidence in the identification of ignitable liquid components. This re-analysis will be automatically conducted on the decision of the lab, for those samples that are negative by GC/MS but have some trace indications of the possible presence of gasoline.
This re-analysis will be at no extra charge to the client.
Activation Laboratories Ltd. has been at the very forefront of developing the application of GC/MS/MS, a well-proven technique, to the analysis of fire debris for Ignitable Liquids. We use this as a secondary confirmation analysis on weak, complex, or highly weathered samples. These samples often may show a few Ignitable Liquid characteristics by GC/MS but not enough to report a positive result. A second analysis by GC/MS/MS can be immediately conducted to confirm whether a sample is truly positive or negative. We have in essence been running GC/MS/MS in parallel with GC/MS since 1997 for these more difficult samples.
Why Use GC/MS/MS?
GC/MS/MS is a more powerful analytical technique that provides a method for detecting target compounds in complex matrices at trace levels. This method is designed to provide a better analysis for weak, highly weathered or older samples. It is particularly well suited for the detection of gasoline and can be used on any sample. This confirmatory analysis can provide the additional information necessary to determine a positive result, when singular GC/MS analysis fails, if an ignitable liquid is present.
What is GC/MS/MS?
Gas Chromatography coupled to Tandem Mass Spectrometry (GC/MS/MS) is used to separate the organic compounds in the mixture (fire debris). This technique is increasingly becoming the analytical tool of choice when analyzing target compounds in very complex matrices. MS/MS is a highly selective mass spectrometric technique, whereby target analytes are detected regardless of the sample matrix or coeluting interferences. In many GC/MS/MS applications the matrix is virtually eliminated. GC/MS/MS is ideal for fire debris analysis and has been used for the analysis of target compounds in various matrices such as complex environmental samples, pesticides in foods, drug metabolites, drug residues in biological fluids and other forensic trace evidence.
How Does it Work?
The basic MS/MS sequence involves:
1. ion creation (same for both GC/MS and GC/MS/MS)
2. ion selection (for GC/MS/MS only)
3. ion dissociation (for GC/MS/MS only)
4. mass analysis (same for both GC/MS and GC/MS/MS)
After separation by Gas Chromatography, the MS/MS operates by first selecting the target ion(s) of choice at a specific mass during the first stage of MS/MS, which separates the ions from the chemical background or matrix. These selected precursor ions or parent ions are then induced to further dissociate by collision with Helium molecules. The resultant unique product ion spectrum provides confirmation of the target analyte. This increased selectivity of MS/MS also results in an enhancement of the signal to noise; thus somewhat lower limits of detection are achieved. GC/MS/MS provides unequivocal identification in cases where GC/MS spectra of compounds are difficult to interpret. Thus, even if the matrix contains another compound with the same mass as the parent ion for the analyte of interest, it is extremely unlikely that the interfering ion would yield the same daughter ion spectra as the analyte, thus GC/MS/MS is more specific for an ignitable liquid. In order to overcome the pyrolysis product interference and improve detection levels, MS/MS can be utilized as the method of detection. As gasoline is one of the more common distillates used by arsonists, the identification of gasoline in fire debris samples is important. The parent ions and daughter ions are isolated and the MS/MS chromatograms for a variety of hydrocarbon distillates are obtained and subsequently compared to ignitable liquid standards, run under identical conditions.
In a survey of our records of the samples that required more information from a GC/MS/MS confirmatory analysis, 47% of these samples that would have been negative by GC/MS were in fact found to be positive for the presence of an ignitable liquid after GC/MS/MS.
Q. The question has been posed. Isn't GC/MS/MS so sensitive that it can determine the presence of an ignitable liquid in any sample since hydrocarbons are present almost everywhere?
A. No! Although GC/MS/MS is at most 20 times more sensitive that GC/MS for same components, the determination of a positive result is not due to the simple detection of hydrocarbons. The hydrocarbons detected must also be present in ratios that define a fingerprint to each other that is then similar to a known ignitable liquid reference materials that has been obtained and analyzed under the same conditions.
Q. How defensible is it in court?
A. The use of GC/MS/MS is well proven and well understood. In January 2002 sample analysis using GC/MS/MS in fire debris was used in testimony during a first degree murder trial. It has been used in the Environmental and Pharmaceutical fields as well as in the Drug Testing area of the Forensic field. This method has been presented in court in the analyses of fire debris in 2001. This is not a new technique; the use on Fire Debris samples is just a new application for GC/MS/MS.
Q. How does it compare to the sensitivity of the K9?
A. Our goal is to complement the use of the K9, and ideally obtain a similar level of sensitivity and specificity. In our observations we believe we are approaching the sensitivity of the average K9 on relatively typical fire debris. We do know as fact that the use of GC/MS/MS has improved the correlation of the samples identified by the K9 and the confirmations made by the lab.
Our GC/MS/MS analysis is some 2 to 20 times more sensitive than our routine GC/MS method depending on the components analyzed and has been developed/tuned to be specific for ignitable liquids. Samples that have trace indications of the presence of an ignitable liquid after our initial GC/MS analysis, but do not satisfy all of our criteria to enable a positive identification by GC/MS, are re-analyzed using GC/MS/MS to obtain the necessary information to provide a positive result that is court defensible should an ignitable liquid be found