Oil and grease analysis with automated SPE using the Biotage® Horizon 5000

Introduction

Hexane extractable material (HEM), also known as Oil & Grease extraction is a simple water quality measurement. The measurement can be used to assess pollution for compliance or as a measure of influent contamination to protect a waste treatment plant from levels that might cause malfunction.

This measurement is used around the world and regulatory agencies have developed methods such as US EPA 1664B, ISO 11349, and Standard Methods 5520G.^1,2,3 We have shown the feasibility of Oil & Grease measurement on a dedicated automated system, the Biotage® Horizon 3100 (previously known as the SPE-DEX® 3100).⁴ In this work we will demonstrate the performance of a general purpose automated Oil & Grease and semi volatile extraction system, the Biotage® Horizon 5000.

The performance of the system for this application will be demonstrated by showing compliance with the quality control requirement of US EPA Method 1664B for small modifications. A new extraction procedure would be considered a modification to the method; therefore the laboratory is required to repeat the initial precision and recovery (IPR) study in Section 9.2.2 9 to demonstrate that the modification produces results equivalent to or superior to results produced by this method.

If the detection limit is suspected to be affected by the new modification a Method Detection Limit study (MDL) would need to be demonstrated. In this case the same disk and chemistry is used, only the automation has changed. ⁵ In this study the laboratory confirming the performance of each typical solid phase extraction (SPE) configuration on the Biotage® Horizon 5000 by conducting an IPR study to satisfy the quality control requirements for a method modification.

Instrumentation

• Biotage
  » Biotage® Horizon 5000 (previously known as the SPE-DEX 5000) Extractor
  » Oil and Grease Standard 40 mg
  » Pacific® Premium disks (90 mm and 47 mm)
  » Atlantic® Fast Flow Pre-Filters (90 mm and 47 mm)
  » Dry Disk® Solvent Drying System (SDS)
  » DryDisk® Membranes
  »  Speed-Vap® IV Automated Evaporation System
  » Aluminum Pans
• Ohaus® Balance
  » Adventurer Pro Model: AV64
  » Max: 65 g, d=0.0001, 10 oC/30 oC
  
  

Method summary

1. Obtain sixteen 1 L samples of DI water.
2. Acidify each sample with hydrochloric acid until pH <2.
3. Add one Oil and Grease 40 mg Standard to each bottle (total concentration of 40 ppm).
4. Extract four samples using the Biotage® Horizon 5000 with 90 mm Pacific® Premium SPE Disks using the method shown in Table 1.
5. Extract four samples using the Biotage® Horizon 5000 with 47 mm Pacific® Premium SPE Disks using the method shown in Table 2.
6. Extract four samples using the Biotage® Horizon 5000 with 90 mm Pacific® Premium SPE Disks with Pre-filters using the method shown in Table 3.
7. Extract four samples using the Biotage® Horizon 5000 with 47 mm Pacific® Premium SPE Disks with Pre-filters using the method shown in Table 4.
8. Dry the extracts using the Dry Disk® SDS with a new DryDisk® for each sample (Sodium sulphate and decanting are allowed for some methods, check with your regulatory agency).
9. Label and pre-weigh twenty-four aluminium pans and add the extract of one sample to each pan.
10. Use the Speed-Vap® IV Evaporation System to evaporate each extract.
11. Weigh each pan and record the weight difference as mg/L of HEM.

Table 1. Biotage® Horizon 5000 Extraction Method for 90 mm Pacific® Premium Disks (No Pre-Filters).

Table 2. Biotage® Horizon 5000 Extraction Method for 47 mm Pacific® Premium Disks (No Pre-Filters).

Table 3. Biotage® Horizon 5000 Extraction Method for 90 mm Pacific® Premium Disks with Pre-Filters.

Table 4. Biotage® Horizon 5000 Extraction Method for 47 mm Pacific® Premium Disks with Pre-Filters.

Table below shows the initial demonstration of precision and recovery for the 90 mm disks without pre-filters.

Table below shows the same information for 90 mm disks with pre-filters

Table below shows the results for 4 samples using 47 mm disks without pre-filters.

Table below shows the results for 4 samples using 47 mm disks with pre-filters

In each case the recovery is better than 95%, well within the acceptable range specified in method 1664B of 83–101%. The standard deviation is well below the 11% limit specified in the method for each of the four configurations tested.

References

1. Method 1664, Revision B: n-Hexane Extractable Material (HEM; Oil and Grease) and Silica Gel Treated n-Hexane Extractable Material (SGT-HEM; Non-polar Material) by Extraction and Gravimetry, available at www.epa.gov, (2010).
2. ISO 11349, Water quality—Determination of low-volatility lipophilic substances—Gravimetric method, First edition 2010-09-15, available at http://www.iso.org/iso/home.htm
3. Method 5520G, Standard Methods for the Analysis of Water and Wastewater, 21 Edition, available at https://www.standardmethods.org/
4. Vinson Leung and Michael Ebitson, Modern Hexane- Extractable Material (Oil & Grease) Analysis in Wastewater Samples, AN102-HOR
5. David Gallagher, Complying with EPA Method 1664A and 1664B by Automated Solid Phase Extraction Utilizing the SPE-DEX® 4790 with Envision® Platform v1.02, AN025-HOR
   
   

Literature number: AN118-HOR