Pittcon 2011: Poster on the Analysis of BTEX in Crude Oils Using Purge-and-Trap GC-MS.

 

Our original study focused on recoveries of light aromatic hydrocarbons in crude oil with and without dispersant compounds added. The results clearly showed there was no difference since the single-ringed aromatics are soluble in water at low ppm levels and readily partition out of the heavy crude. Even Maya (medium crude) and California (heavy crude) showed no visible solubility in water, but had respectable amounts of BTEX and other light hydrocarbons.  For more information on this part of the study I have included a printable version of the poster and you are also welcome to the poster as it was presented by Jack Cochran at Pittcon.

Links:         Pittcon presentation in printable format Crude Oil Analysis by Purge and Trap Paper

Pittcon Poster as presented at Show: Purge&TrapCrudeOil

All Pittcon 2011 Presentations: Found Here.

From this work came many interesting, probably not surprising, observations that I would like to share. During this study we took videos ( *.avi & *.mov format) to illustrate the differences between; dispersed / non-dispersed crude, addition of dispersants to two different crude oils in methanol, and Maya Crude in water. Below is a detailed explanation:

Clip#1: An example of a sample from the BP Gulf Oil Spill Riser pipe (MC252) spiked into 40ml vial with and without dispersant. The vial on the right marked “C” is crude oil only, where the vial on the left marked “C+D” is crude with 2-butoxyethanol and propylene glycol. The difference between the two is striking.

Clip#2: In this video we added equal amounts of crude and  equal amounts of methanol into three Accuform Micro-Vials (cat#21050). The vial on the left and the middle vial contain BP Crude oil from the bottom of the ocean (MC252). The vial on the right contains Maya crude oil. We added 2-butoxyethanol & propylene glycol to the MC252 crude (middle) and the Maya crude (right). Since the density for methanol and MC252 are similar the addition of the dispersant caused the lighter portion of this crude to float. The Maya oil is considered a medium crude with a density of 0.93. The addition of the dispersant compounds had little affect in the short term. Over a period of an hour a portion of this crude became opaque white and formed a partial emulsion.

Clip#3: Another example of the insoluble nature of Maya crude compared to the light sweet MC252 crude oil. When we added MC252 oil to water we observed a light brown cloud around the black oil drop. With the Maya crude it simply fell to the bottom as shown in the video. Interestingly we were able to observe BTEX in all samples even with minimal agitation.  BTEX recoveries were similar when standards were made up in water versus methanol.

Materials Used for Pittcon Presentation:

Column: Rxi-624Sil MS 30m x 0.25mm x 1.4df  (13868)
Liner: 1mm ID split liner (20973)
Inlet Seal: Dual Vespel Gold (22083)
Purge & Trap Split Injection Port Weldment for OI w/o split trap (22665)
 
Analytical Standards:
   BTEX (30051)
   Bromofluorobenzene (30026)
   1,4-Difluorobutane (30227)
   1,2-Dichlorobenzene-d4 (30049)
   Aromatic Calibration Mix (552316)
   Surrogate Mix (30067)
   Internal Standard Mix (30241)
   Unleaded Gasoline (30081)
 
Instrumentation:
OI Analytical 4660 Eclipse Purge & Trap Concentrator
OI Analytical 4551-A Autosampler
Agilent GC-MS: 7890 / 5975
 
 
 

 Restek’s Optimizing the Analysis of Volatile Organic Compounds can be found at the link below:

http://www.restek.com/pdfs/59887B.PDF

 

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