Application Note OI Analytical, a Xylem brand • 4491-01 Analysis of BTEX-MTBE by Purge and Trap (P&T) Concentration and Determination by GC/PID PETROCHEMICAL SERIES Introduction The analysis of Benzene, Toluene, Ethylbenzene, Xylenes, and Methyl-tert-butyl ether is a common analysis performed in many laboratories. BTEX compounds are naturally occurring constituents in crude oil and are created and used during the processing of refined petroleum products and during the production of chemical intermediates for many consumer products.1 BTEX compounds represent some of the most hazardous components in gasoline and are considered toxins of concern in fuels. These compounds, as well as MTBE a fuel oxygenate, are very mobile in soil and groundwater and are used as indicator compounds in various monitoring and clean-up programs such as the Underground Storage Tank (UST) Program.2 There are technology improvements available for analysis using the BTEX-MTBE method. Figure 1. OI Analytical Eclipse 4760 Purge and Trap and the 4551A Autosampler and LV20 Detector

Instrumentation Purge and trap concentration was performed with an OI Analytical 4760 purge and trap with a 4551A autosampler. The LV-20 Standard Additions Module was used to inject 5 µl of internal standard and surrogate standard to each sample. The LV-20 employs high-speed valves that inject a programmed volume of standard with no excess or waste. GC separation and detection utilized an Agilent 7890A GC and OI Analytical 4450 tandem photoionization/flame ionization detector (PID/ FID). The column used was a Restek Rxi-624Sil MS which can be programmed up to 320 ˚C if samples with very heavy...

Table 2. Calibration Data RL (ppb) Figure 2. BTEX-MTBE 100 (200) ppb Standard

The 4760/4551A purge and trap system coupled with the 4450 PID/FID gave excellent results using a very simple and rugged methodology. The total GC cycle time from injection to injection totaled 15 minutes, making this a fast method as well. References 1. Leusch, F. and Barktow, M. 2010. A Short Primer on Benzene, toluene, Ethylbenzene, and Xylenes (BTEX) in the Environment and in Hydraulic Fracturing Fluids. Griffith University. 2. Irwin, R. 1997. Environmental Contaminants Encyclopedia. National Park Service 3. USEPA Method 8021B. 2014 Aromatic and Halogenated Volatiles by Gas Chromatography...