Method Detection Limits for EPA Method 8015 Diesel Range Organics using Fully Automated Extraction and Concentration Michael Ebitson, David Gallagher, Horizon Technology, Inc. Key Words EPA Method 8015, ISO 9377-2, Diesel Range Organics, Oil Range Organics, SPE, Solid Phase Extraction Introduction One of the most frequently desired quantities in environmental chemistry is the amount of diesel range organics (DROs) contained within a sample. The analysis of DROs is performed in almost every major environmental laboratory under the US EPA Method 8015 1 or by using the similar ISO 9377-2 2. This method is commonly used to determine the contamination of alkanes from C10 to C28 caused by leaking underground storage containers. In addition to testing under Method 8015, many US staterun environmental agencies have used Method 8015 as the foundation for their own, more in depth, methods; for example, the Massachusetts Volatile Petroleum Hydrocarbons (VPH) and Extractable Petroleum Hydrocarbon (EPH) methods and the Florida Total Recoverable Petroleum Hydrocarbon (TRPH) method. The simplicity of EPA Method 8015 lends itself easily to automation. As such, the Method Detection Limit (MDL) extraction of the target range for the study was done using the Horizon Technology SPE-DEX 4790 automated extraction unit with Envision controller. The drying and concentration of the final extract was performed using the DryVap Concentrator System with DryDisk technology. Final analysis was done using a gas chromatograph (GC) with flame ionization detector (FID). The SPE-DEX 4790 is an automated solid phase extractor specifically designed to extract a wide range of target analytes from both influent and effluent sample matrices. The Envision controller is a web based controller system which provides a simple yet elegant method of interacting with up to eight extractor units. The DryVap Concentrator System used in conjunction with DryDisk allows for an automated way to both dry and concentrate a sample extract. The benefits of the Horizon Technology fully automated extraction and concentration systems are many and include such things as decreased solvent usage, no sodium sulfate cost, less human interaction, more precise and accurate results, and faster turnaround-times. Instrumentation Horizon Technology SPE-DEX 4790 Automated Extraction System Envision Controller Atlantic DVB Disk DryVap Concentration System DryDisk Solvent Drying System
Agilent 6890N GC-FID Supelco SPB-1 15 m x 0.53 mm x 0.1 um GC column #2 Diesel Fuel and 5W-30 Motor Oil Standard 1-Chlorooctadecane Surrogate Spike Method Summary 1. Obtain two liters of DI water and acidify to ph<2. 2. Spike the Diesel standard into one liter such that the final concentration is 0.5 mg/l and the Oil standard into another such that it is 0.8 mg/l. 3. Add the 1-Chlorooctadecane surrogate into each. 4. Extract the samples using the SPE-DEX 4790 and the method shown below in Table 2. 5. Dry and concentrate the extracts using the DryVap settings shown in Table 3 to a final volume of 5 ml. 6. Perform the final analysis using GC-FID. The carbon range which was integrated was from C10-C28 for DRO and C28-C40 for the Oil Range Organics (ORO). 7. To complete the MDL study, extract seven replicates of each type using steps one through six over three, non-consecutive, days. Table 1: Purge Method Step Solvent Dry Time Prewet 1 Methanol 15 s Prewet 2 MeCl 15 s Prewet 3 MeCl 15 s Rinse 1 Acetone 5 s Rinse 2 Acetone 5 s Rinse 3 MeCl 10 s Table 2: Extraction Method Step Solvent Soak Time Dry Time Prewet 1 MeCl 2:00 min 0:30 min Prewet 2 MeCl 2:00 min 0:30 min Prewet 3 Methanol 2:00 min 0:05 min Prewet 4 Reagent Water 1:00 min 0:05 min Prewet 5 Reagent Water 1:30 min 0:02 min Process Sample Air Dry 0:30 min Rinse 1 Acetone 3:00 min 0:30 min Rinse 2 MeCl 3:00 min 0:30 min Rinse 3 MeCl 2:00 min 0:30 min Rinse 4 MeCl 2:00 min 0:30 min Rinse 5 MeCl 2:00 min 2:00 min Table 3: DryVap Settings Dry Volume 20 ml Heater 1 Heater Timer Off Autorinse Off P a ge 2
Results The MDL study shown in Tables 4 and 5 below were produced over three non-consecutive days and includes seven replicates of each spike. They show that the diesel standard is easier to replicate than the oil standard, as indicated by their standard deviations. This is likely caused by the buildup of oil residue within the injection port and column of the GC. Also, Figures 1 and 2 show typical chromatograms from a GC-FID for diesel and oil respectively. These chromatograms were for 5 ppm spikes and showed average surrogate recoveries of 85.5%. Table 4: Diesel MDL Results Replicate Recovery (mg/l) 1 0.396 2 0.358 3 0.377 4 0.383 5 0.387 6 0.369 7 0.388 Average 0.380 Std. Dev.: 0.0129 MDL: 0.0404 Table 5: 5W-30 Motor Oil MDL Results Replicate Recovery (mg/l) 1 0.511 2 0.590 3 0.501 4 0.542 5 0.548 6 0.474 7 0.636 Average 0.543 Std. Dev.: 0.0554 MDL: 0.1742 P a ge 3
Figure 1: GC-FID Chromatogram of a 5 ppm Diesel Spike (82.8% Diesel recovery, 86% Surrogate recovery). Figure 2: GC-FID Chromatogram of a 5 ppm 5W-30 Motor Oil Spike (75.4% Diesel recovery, 85% Surrogate recovery P a ge 4
Conclusion From the MDL data shown we can see that, using the complete Horizon Technology solution for extraction, drying, and concentration, a laboratory will see highly reproducible results. Automated SPE will not only allow you continual compliance with the EPA, but will reduce labor and solvent costs, allow faster turnaround times, and improve on both laboratory precision and accuracy. Acknowledgement Horizon would like to thank Randall Heu and Hawaiian Electric Company for their assistance in performing this study. References 1. US EPA Method 8015D, Nonhalogenated Organics using GC/FID, US EPA (2003). 2. ISO 9377-2, Water quality Determination of hydrocarbon oil index -Part 2: Method using Solvent Extraction and Gas Chromatography, First edition 2000-10-15. www.horizontechinc.com AN0561409_02 16 Northwestern Drive, Salem, NH 03079 USA Tel: (603) 893-3663 Email: Support-Service@horizontechinc.com