March 2022 – Want to Know What Else is in Your Previously Generated Sample Data?

Recently, Environmental Standards was retained to perform a forensic data review on groundwater samples with the objective of evaluating the possible presence of non-target biodegradation byproducts of specific “parent” target semivolatile compounds.

Non-target compounds refer to compounds that were not requested for quantitative analysis and, therefore, were not reported by the analytical laboratory.

Parent target compounds refer to compounds that were requested for quantitative analysis and reported by the analytical laboratory.

For this forensic assignment, Environmental Standards’ client was interested in gaining an understanding of whether the published non-target biodegradation products were present in previously collected groundwater samples and, if so, determine whether their presence could support a monitored natural attenuation remedy. Furthermore, such information could potentially assist in age dating the “parent” target compounds and provide a better understanding of the overall degradation process and movement of contaminants through the groundwater.

As part of the forensic data review, Environmental Standards received raw, instrument data files from the analytical laboratory. The raw instrument files provided information and data far beyond those provided in the image-based laboratory reports. Armed with the raw instrument files, the Environmental Standards Senior Chemists applied an internally developed workflow involving multiple software applications to forensically evaluate the past groundwater data that had been quantitively analyzed for the parent compounds. Using a knowledge of chemistry and the biodegradation pathway of the target compounds, our Senior Chemists were able to perform mass spectral searches within the raw instrument files to specifically search the data for the specific mass-to-charge (m/z) ratios of the biodegradation products. Once our Senior Chemists were able to qualitatively identify the biodegradation products with a reasonable level of confidence, they were able to predict the specific chromatographic retention times of the identified candidate biodegradation compounds. With this information, our Senior Chemists utilized software to provide chromatographic overlays showing the ratio of target to non-target compounds in each sample. The overlays provided easy-to-understand graphics for the client, even in some cases, highlighting samples for which the target compounds had been reported as “not-detected” by the laboratory, but the biodegradation products were qualitatively identified.

Environmental Standards’ Chemists have the tools and knowledge to perform forensic evaluations and desktop non-targeted analysis (NTA) to assist our clients in better understanding site contaminants, degradation products and migration pathways. This type of forensic evaluation can have critical implications for source identification and allocation, source control, and fate-and-transport assessments.