Processing Samples
This section describes the equipment and procedures for processing (i.e., filleting, homogenizing, compositing) the samples for analysis. An experienced fisheries biologist should train or supervise all laboratory personnel performing sample processing procedures.
Equipment
All instruments, work surfaces, and containers should be free of contamination. Thoroughly clean all equipment used for sample processing between each sample to avoid cross-contamination. Analyze blanks or rinsate samples to assess the effectiveness of cleaning procedures. For monitoring programs that have multiple target analytes, a universal decontaminant procedure for all equipment may be most appropriate. The U.S. Environmental Protection Agency uses the following procedure in its national fish studies. Prior to preparing any fillet samples, thoroughly clean utensils and cutting boards using the following series of procedures:
- Wash with a detergent solution (phosphate- and scent-free) and warm tap water
- Rinse three times with warm tap water
- Rinse three times with deionized (DI) water (or another form of contaminant-free water)
- Rinse with acetone
- Rinse three times with DI water (or another form of contaminant-free water)
- Rinse with 5% nitric acid
- Rinse three times with DI water (or another form of contaminant-free water)
To avoid contamination, select equipment materials based on the type of analysis: organics or metals.
Organics Analysis
- Equipment material - stainless steel, anodized aluminum, borosilicate glass, ceramic, or quartz. For PFAS analysis, use HDPE straight-sided jar with foil-lined lid. Do not use polytetrafluoroethylene (PTFE) if analyzing for PFAS.
- Do not use polypropylene and polyethylene (plastic) surfaces, instruments, gloves, or containers.
- Fillet on glass or stainless steel cutting boards that are cleaned properly between fish.
- Use corrosion-resistant stainless steel or quartz instruments or knives with titanium blades.
- Store homogenates in borosilicate glass, quartz, I or in heavy duty aluminum foil.
Metals Analysis
- Equipment material - quartz, polytetrafluoroethylene (PTFE), ceramic, polypropylene, or polyethylene.
- Corrosion-resistant stainless steel for sample processing equipment is acceptable if chromium and nickel are not metals of concern. Quartz utensils are ideal but expensive.
- Borosilicate glass is preferred over plastic for bench liners and bottles.
- Fillet on glass or PTFE cutting boards that are cleaned properly between fish or on cutting boards covered with heavy duty aluminum foil that is changed after each fish.
- Store homogenates in plastic, borosilicate glass, quartz, or PTFE containers
Procedures
Each time custody of a sample or set of samples is transferred from one person to another during processing, both parties must complete and sign the Personal Custody Record of the Chain of Custody form that originated in the field. Trace possession and location of the samples at all times as a part of Quality Assurance and Quality Control measures. Record data from each procedure in an accessible system such as a shared online system.
Program managers must select and document the sample type that best aligns with their study goals and the target audience for any advisories that are developed. Most of the general population consumes the fish fillet; therefore, the fish fillet sample type is the most common in monitoring programs. Another option for the sample collection is the whole fish. This option is appropriate if the target audience generally consumes the whole fish or parts other than the fillet. Additional details are on the Fish Sample Types webpage.
Sample processing procedures are described for: