Forensic Tools Featuring Deconvolution Of Complicated Mass Spectra

Co-Authors: Stephen Hilfiker, MS, CFEA, REPA and Albert Robbat, PhD, MBA

Effective Forensic Tools

Effective forensic project management should include an evaluation of multiple forensic tools based on site-specific circumstances.  The process of evaluation and the ultimate selection of the forensic tool are critical to a successful outcome.  When project budgets allow, combining forensic methods for corroborative evidence can substantially strengthen your client’s position in an effort to prevent or support litigation.  The effective forensic consultant must be well acquainted with an ever-expanding list of analytical methods, environmental regulations, assessment procedures and remedial technologies.  One of the forensic tools currently featured by ERMI is forensic software that deconvolutes complicated mass spectra.

Distinguishing and aging mixed contamination plumes are performed using Ion Fingerprint Detection software.  Soil and groundwater samples analyzed using Agilent GC/MS instruments can produce data in .d format.  This raw electronic data is input into the software which enables customized analytical methods to fingerprint and age samples.  Deconvolution algorithms untangle complicated mass spectra allowing for speciation of target compounds of interest.  Positively identifying indicator compounds for brand identification, biomarker analyses, cluster analyses, PIANO analyses, diagnostic alkylated benzene ratio analyses and other forensic analyses are aided through the use of the software.

According to the Environmental Protection Agency – by “seeing through” the matrix interferences, the software reduces the need for sample re-analysis and dilution, and increases confidence in surrogate, internal standard, and target compound identification and quantification.  Where standard methods fail to determine the cause and origin of the contamination, the Ion Fingerprint Detection software (aka IST for GC/MS), with its deconvolution algorithms is able to sort through the interference to determine product identity and age of contamination.

The aging capabilities are demonstrated in a case study where a service station operated for nearly 30 years with two fuel brands and numerous suspected discharges.  A known pollution event was affirmed as the sole source based on biomarker analyses and alkylbenzene ratios.  A set of target compounds was established for determining the age of the sample.  These compounds include BTEX as well as alkylated C3 and C4 benzenes.  Target compounds were identified and quantitated, and the ratios of BTEX to C3, C4 alkylated benzenes indicate that the product in the monitor wells is from a source that predates 1990.  The component distribution in the chromatogram confirms this conclusion.  The data indicate the product is old, and was subject to environmental degradation and washing for at least 15-20 years or more.  Opinions based on the data match a known date of a substantial gasoline discharge.

 

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