What is Solid Phase Extraction?
How does SPE work in EPA Method 1664A specifically?
Is EPA Method 1664A–SPE difficult?
What equipment do I need to perform EPA Method 1664A-SPE in my lab?
Which Xenosep Starter Kit for EPA Method 1664A-SPE is right for me and my lab?
Do I need to recover the hexane from the extract, which is distilled/evaporated to dryness?
What options are available to recover the hexane with the Xenosep SPE Starter Kits?
Do I have to prepare the Precision and Recovery (PAR) Standard myself?
How can I check to see if my PAR Standard is at the correct concentration of 4mg/mL?
Are aluminum pans easier to work with than glass flasks?
How do I perform the IPR (Initial Precision and Recovery) and MDL (Method Detection Limit) Studies to demonstrate laboratory capability to perform EPA Method 1664A?
How does the Manifold System work?
Can I process my sample containing high solids with the Xenosep SPE System?
Can I recover hexane if I’m using the Manifold System?
Do I have to acidify my QC samples to pH<2?
Q. What is Solid Phase Extraction?
A. Solid Phase Extraction (SPE) is a technique which utilizes a chemically treated SPE filter (or other device) to extract and concentrate (retain) analytes of interest onto the SPE filter as an aqueous sample is passed through it. Interfering substances are then removed so the analytes of interest can be efficiently eluted (or released) from the SPE filter using a series of rinses with an appropriate final extraction solvent.
Q. How does SPE work in EPA Method 1664A specifically?
A. The SPE filter is chemically treated to make it similar in nature to the hydrophobic Oil and Grease analytes. Once the SPE filter is properly conditioned, the wastewater sample is passed through the SPE filter under vacuum. As the Oil and Grease analytes contact the SPE filter, they are stick to it and are extracted (or retained) from the wastewater sample by the SPE filter. Then the SPE filter is then air dried for a minimum of 4 minutes with vacuum at 1 CFM. This air-dry step is very important as it removes any residual water trapped in the SPE filter, which can interfere with the efficient elution of the Oil and Grease analytes with hexane. After the SPE filter is properly air dried, 3 x 10mL rinses of hexane (the final extraction solvent) are used to elute (or release) the analytes of interest from the SPE filter into the final collection container.
Q. Is EPA Method 1664A–SPE difficult?
A. No. If you currently perform Total Suspended Solids (TSS) testing, you can easily perform EPA Method 1664-SPE. Watch a video on EPA Method 1664A-SPE performed using the Xenosep Starter Kit without Solvent Recovery, and download the written instructions for Oil and Grease, SPE Method 10300.
Q. What equipment do I need to perform EPA Method 1664A-SPE in my lab?
A. Besides choosing the right Xenosep Starter kit for your needs, the main components are:
1. An analytical balance capable of measuring 0.1mg
2. A vacuum capable of generating 1 CFM free air flow (3 CFM preferred)
3. A hot plate, slide warmer or other means for concentrating the final extracts to dryness
For a complete list of the equipment and supplies needed to perform EPA Method 1664A-SPE in your lab, download Oil and Grease, SPE Method 10300.
Q. Which Xenosep Starter Kit for EPA Method 1664A-SPE is right for me and my lab?
A. If you need to analyze 1-2 NPDES-type samples on a monthly or longer basis, we recommend either of the one place Starter Kits, Hach # 2943231 (Without Solvent Recovery) or Hach # 2943200 (With Solvent Recovery). If you need to analyze 1-2 samples on a daily/weekly basis or 3 or more samples at any time, we recommend the three-place manifold and Starter kit, Hach # 2946707 and Hach # 2943232 respectively.
Q. Do I need to recover the hexane from the extract, which is distilled/evaporated to dryness?
A. That depends on your laboratory’s waste management policy, any applicable regulations and if performed by a certified laboratory, at the discretion of your EPA and/or state regulatory authority. See the EPA website for more information.
Q. What options are available to recover the hexane with the Xenosep SPE Starter Kits?
A. If you prefer evaporation as the concentration technique and working with the 105mm aluminum pans, Xenosep offers an SPE Solvent Recovery Kit, Hach # 2514300. If you would prefer distillation and using the flat sided flasks, we recommend either the Xenosep Distillation Kit, Hach # 2946701 or for greater value, initially purchasing the Starter Kit with Solvent Recovery, Hach # 2943200.
Q. Do I have to prepare the Precision and Recovery (PAR) Standard myself?
A. No, these can be purchased in ready-to-use 30mL vials containing Stearic Acid and Hexadecane in Acetone at a concentration of 2 mg/mL each, Hach # 2943701. Warm to re-dissolve any visible precipitate, remove 10mL with a volumetric pipet and spike into 1L of acidified (pH<2) reagent water to obtain the 40 mg/L PAR sample. Alternatively, the PAR Standard can be prepared in your laboratory according to Hach Method 10300.
Q. How can I check to see if my PAR Standard is at the correct concentration of 4mg/mL?
A. Remove 10.0 ± 0.1 mL with a volumetric pipet, place in a tared aluminum pan, evaporate in a fume hood until dry spots start to appear in the bottom of the pan, desiccate for a minimum of 30 minutes until achieving a stable weight which must be 40 ± 1 mg. If not, prepare or obtain a fresh solution. Besides incorrect standard preparation, pipetting/ volumetric errors or concentration technique, other possible causes for high or low concentration values are 1) evaporation of the acetone over time, 2) pipetting visible and variable amounts of precipitates or 3) visible precipitates sticking to the PTFE cap liner of the container.
Q. Are aluminum pans easier to work with than glass flasks?
A. Yes. They tare much faster because they are made of metal and do not have the same static charge issues associated with glass flasks. In addition, they are lighter (2 – 7 grams) and it is easier to see the concentration end point of dry spots starting to occur in the bottom of the container.
Q. How do I perform the IPR (Initial Precision and Recovery) and MDL (Method Detection Limit) Studies to demonstrate laboratory capability to perform EPA Method 1664A?
A. Details for both of these studies are detailed in Hach Method 10300.
Q. How does the Manifold System work?
A. The manifold system works in the same fashion as the single place Starter Kit except multiple extracted (filtered) water samples are collected in a separate vacuum rated container that is attached between the manifold outlet and the vacuum pump/trap inlet.
Q. Can I process my sample containing high solids with the Xenosep SPE System?
A. The Xenosep SPE System with a 47mm diameter Xenomax® triple layer SPE filter were designed to process most samples containing less than 500 PPM (500mg/L) of TSS (Total Suspended Solids). An optional 42mm diameter Xenomax hi loft prefilter is available separately which can extend this sample range to 1,000 PPM (1,000mg/L). For samples containing higher levels of TSS, collection and analysis of smaller sample volume is an allowable EPA Method 1664A modification as long as all quality control requirements are achieved and the final results are expressed as mg/L.
Q. Can I recover hexane if I’m using the Manifold System?
A. Yes. Two separate Solvent Recovery apparatus are available depending on your preferred concentration technique. For aluminum pans/evaporation, use Hach # 2514300. For flat-sided flasks/distillation, use Hach # 2946701. Alternatively, any other solvent recovery apparatus that can accept a 24/40 (or 24/25) standard taper glass joint may be used as well, especially if it can process more than one sample at a time.
Q. Do I have to acidify my QC samples to pH <2?
A. Yes. All samples (including QC) must be acidified to pH<2 to inhibit microbiological activity and to insure accurate, high quality results as stearic acid solubility in water increases with increasing pH values