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VPH Analysis by the New GC/MS Method

Alpha Analytical is now offering VPH Analysis by the new MassDEP procedure – “Method for the Determination of Volatile Petroleum Hydrocarbons (VPH) by Gas Chromatography / Mass Spectrometry; January, 2017”.  This new GC/MS VPH method does not replace the original GC/PID-FID VPH method, Alpha continues to offer VPH analysis by both methodologies.  The GC/MS VPH does represent another option for VPH analysis however, and as such there are some advantages to the new method, depending on your project application.

Given the greater degree of qualitative certainty provided by GC/MS over GC/PID-FID, the GC/MS VPH analysis can exclude contributions from non-petroleum hydrocarbons.  Non-petroleum hydrocarbons can range from compounds of biogenic origin such as terpenes ; or alcohols and ketones, which may or may not have a natural origin; as well as chlorinated solvents which are present due to a release.  The GC/MS VPH method may be particularly useful for site applications where comingled plumes of petroleum hydrocarbons and chlorinated solvents exist. 

The presence of these non-petroleum compounds would not be included in the VPH aliphatic and aromatic hydrocarbon range totals if they can be identified as non-petroleum hydrocarbons and they are not co-eluting with another hydrocarbon chromatographic peak.  If the VPH by GC/MS method is requested, Alpha will automatically exclude those non-petroleum compounds that meet this criteria.  The report narrative will list the excluded compounds that were identified as non-petroleum hydrocarbons and state that they were not included in the associated VPH range total concentrations. 

Similar to the original GC/PID-FID VPH method, the GC/MS VPH method also could be subject to potential positive biases.  An evaluation of the MassDEP Round Robin Study that was conducted to validate the method showed that the GC/MS C9 – C12 aliphatic range could be biased high due to the difference in the mass spectrometer’s response between aliphatic and aromatic hydrocarbons.  The following table summarizes the MassDEP’s observations of the Round Robin data:

  GC/MS GC/PID-FID
Target VPH Analytes Equivalent Equivalent
C5 – C8 Aliphatics Equivalent Equivalent
C9 – C12 Aliphatics Potential high bias from MS response to aromatics in range  
C9– C10 Aromatics   Potential high bias from PID response to aliphatics in range

 

For more information about Alpha Analytical’s VPH analytical options, please contact us at This email address is being protected from spambots. You need JavaScript enabled to view it. or 800-624-9220 or reach out to your Alpha Analytical Project Manager or Account Service Representative.

 

 

 

 

 

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