In developing these methods, EPA found that one of the greatest difficulties in measuring pollutants at these [trace] levels was precluding sample contamination during collection, transport, and analysis.

– EPA Method 1669, Sampling Ambient Water for Trace Metals at EPA Water Quality Criteria Levels

Field Sampling Recommendations

The following Brooks Applied Labs (BAL) protocol is derived from EPA Method 1669: Sampling Ambient Water for Trace Metals at EPA Water Quality Criteria Levels (July, 1996). This brief summary is meant to be used as an overview and a reference. For more comprehensive instructions and a complete description of the proper methods for sampling ambient water for trace levels of metals, please refer to EPA Method 1669.

Gloves – Sampling personnel are required to wear clean, non-powdered gloves (made of latex, nitrile, polyethylene, or vinyl) at all times when handling sampling equipment and sample containers. Gloves must be changed in between each sample collected. Gloves should be tested prior to use to demonstrate low levels of trace metals, especially mercury and zinc. Tested-clean gloves can be purchased from BAL in packs of 12 or 100 gloves.

Dirty Hands/Clean Hands – Upon arrival at the sampling site, one member of the sampling team is designated as “dirty hands” and another member is designated as “clean hands”.

“Dirty Hands” is responsible for all activities that do not involve direct contact with the sample. Examples of activities performed by “dirty hands” include:

  • Removal of the double-bagged sample containers from the cooler
  • Holding and opening of the outer zip-type bag
  • Operation of any sampling apparatus involved in collection (e.g., peristaltic pump, grab sampling device, etc.)
  • If only two samplers are available, then “dirty hands” should also be responsible for performing all necessary documentation

“Clean Hands” only performs operations involving direct contact with the sample or sample collection container. These activities include:

  • Opening and closing the inner zip-type bag
  • All direct handling of the sample container, including attachment/detachment of  sample container to/from  collection device
  • Transfer of the sample from the sample collection device to the sample container

Sampling – Whenever possible, samples are collected facing upstream and upwind of the sampling team. “Clean hands” should remove the sample container from the inner bag and reseal the inner bag in order to minimize potential contamination.

Surface samples are collected using a grab sampling technique. This technique involves submersion of the sample container, filling and capping the container while still submersed to minimize exposure to airborne contamination. Prior to its final filling, the sample container should be partially filled and rinsed 3 times with the sample to be collected.

Note that some methods, such as EPA Method 1632 for arsenic speciation, require that samples be preserved in the field or collected into bottles pre-preserved with acid. For these methods, Brooks Applied Labs can include the proper amount of the appropriate preservative in each sample container. Sample containers with preservative must not be rinsed prior to sample collection or submerged below the water surface. Instead, tip the top lip of the container gently below the water surface so that the preservative remains in the container while filling. Alternatively, you may use a second container (tripled rinsed with the native sample) without preservative to serve as a sample collection container. After collection, pour the sample from the non-preserved container into the container with preservative. Extra sample transfer bottles may be purchased from BAL.

Any sampling equipment (e.g., tubing, in-line filter units, etc.) must be purged in the field prior to use for collecting samples. BAL has determined that purging the in-line filter units for 3 minutes (using 2-3 L of sample or ultra-pure reagent water) is sufficient to remove any metals contamination to levels below BAL’s reporting limits. EPA 1669 suggests that sampling tubing be purged for 5-10 minutes prior to collecting samples.

All sample containers should be completely filled to minimize contact with the atmosphere, and should immediately be tightly capped. Again, prior to its final filling, the sample container should be partially filled and rinsed 3 times. While “dirty hands” holds open the outer ziplock bag, “clean hands” opens the inner bag, returns the filled sample container to the inner bag, and reseals the inner bag. “Dirty hands” then reseals the outer bag and places the sample in the cooler.

Certified-clean bottles, tubing, filters, and reagent water are available from BAL.

Sample Handling Notices

Complete list of recommended sample containers, minimum volume/mass requirements, preservations, and holding time requirements for the analysis performed at BAL.

Coolant Materials: For analyses requiring samples to be kept cold (0 – 4 °C) until lab preservation and/or analysis, please either pack the samples in ice or refrigerate them immediately after collection. Then pack the samples with an abundant amount of ice when shipping them to BAL. Double-bag the ice to prevent leakage into the cooler – if a cooler is leaking water, the courier may refuse to carry it! Do not use “blue ice” as it will not effectively keep samples at the proper temperature for the analyses.

Note that if water samples are to be analyzed for low-level mercury (by EPA Method 1631) only, samples are not required to be kept cool. EPA Method 1631E allows samples to be shipped at ambient temperatures and then preserved with HCl or BrCl in the lab within 28 days of collection if oxidation is to take place in the original sample container.

Samples Requiring Filtration: All samples requiring filtration for dissolved analyses MUST be filtered within 2 days of sample collection and kept at 0-4 °C prior to filtration, with the following exceptions: (1) samples requiring filtration for dissolved mercury by EPA 1631 must be filtered within 24 hours (or 1 day) of sample collection, (2) samples requiring filtration for dissolved trace elements by EPA 200.8 must be filtered within 15 minutes of collection (field-filtration is required), and (3) samples requiring filtration for dissolved arsenic species by EPA 1632 must be field-filtered. 

Custody Seals: Two custody seals are included with each bottle shipment. Custody seals are intended for the outside of the cooler/package. If you would like to seal the sample itself, do not place the custody seal directly on the bottle. Instead, place the custody seal directly over the zipper of the inner zip-type bag containing the sample.

Field Preservation: BAL typically ships sample containers empty, but some methods, such as EPA Method 1632 for arsenic speciation, require that samples be collected into pre-preserved containers (or preserved in the field). In other cases, overnight shipping of the samples to BAL may not be feasible. In such cases, BAL includes the proper amount of the appropriate preservative in each sample container, which will be clearly marked as containing preservative (typically HCl). The sample container must not be rinsed prior to sample collection when the preservative is included in the sample container.

HDPE and FLPE Bottles: When collecting water samples for both mercury and for other metals, please be aware that the two bottle types that will be sent look very similar. HDPE bottles are generally intended for all other metals besides mercury and methylmercury. FLPE bottles are typically for mercury and methylmercury only. The difference can be noted by reading the imprint on the bottom of the bottle, which can be seen through the zip-type bag. Generally, labels identifying the bottle type are present on the outer bag.

Water Sample Field Blanks: For 1600-series methods, field blanks are required to be collected and analyzed at a frequency of 10%. If field blanks are to be collected, a bottle of ultra-pure reagent water (usually 1-L) should be requested to be included with the sampling kit. This bottle will be labeled “Reagent Water for Field Blanks”. The contents of this bottle should be decanted into the appropriate sample container at the same time and location that the other samples are being collected. The field blank should be treated as if it were a field sample. As with nearly all samples to be collected, the sample bottle (usually a 250-mL bottle for total mercury, for example) should be rinsed three times with the supplied reagent water before the collection of the field blank sample. Water for field blanks can be purchased from BAL in a wide variety of container sizes, including 10-L or 20-L carboys.

Trip Blanks: Trip blanks are containers with ultra-pure reagent water provided by BAL that travel with the containers provided to the client for their sampling purposes. Trip blanks have custody seals placed on them when they are prepared to confirm that the containers have never been opened prior to return receipt at BAL.

Sediment/Soil Samples: When collecting sediment/soil samples, avoid substances that may not be considered part of the sample matrix to be analyzed (e.g., rocks, twigs, roots, etc.). Avoid collecting excessively “wet” sediment samples, whenever possible. If any overlying water is present, decant it prior to shipping. BAL recommends collecting sediment/soil samples in HDPE jars. If glass jars are used, please do not fill more than 2/3 full; otherwise, the jars may break upon freezing. Sediment/soil samples for mercury and methylmercury analysis may be collected in HDPE jars.

Packing Instructions for Glass Containers: Wrap bottles individually in bubble wrap or a Styrofoam sleeve. Make sure samples are surrounded with packing materials so that they cannot move during shipment, and so that glass containers are never in direct contact with each other. If necessary, use standard Styrofoam (peanuts) or plastic (bubble wrap) packing materials. NEVER use vermiculite as it contains very high levels of metals.

BAL Sample Acceptance Policy

All samples received by BAL must meet the following requirements. Results for samples that do not meet the requirements will be appropriately qualified and fully narrated to make it clear that the samples did not conform to the policy.

Proper, Full, and Complete Documentation of the Sample: Documentation sent with the sample must include a chain-of-custody (COC) form listing the sample identification, date and time of collection, the collector’s name or initials, preservation type, and sample type.

Sample Labeling: The sample must be received with a durable, water-resistant label written with indelible ink. The sample must be uniquely identified so that it cannot be confused with any other sample in the shipment. This unique identifier must match the sample ID listed on the COC form.

Containers: The sample must be collected and received in a container appropriate to the analysis being requested.

Adherence to Holding Times: The sample must be received in adherence to the specific holding time for the analysis being requested. Sample holding time requirements will vary dependent upon whether the sample was preserved in the field or in the lab. Click here for a full list of holding times for the analyses that BAL performs.

Adequate Sample Volume or Mass: Sufficient sample volume or mass must be available to perform the necessary analyses. Click here for a full list of the minimum sample volume or mass requirements for the analyses that BAL performs.

Damage: The sample must be received without any evidence of damaged. Signs of damage may include a dented cooler or a broken sample container.

Contamination: Samples must be received without any evidence of possible contamination. Signs of potential contamination may include loose container caps, unzipped or ripped bag holding the sample container, broken custody seals, leakage from or into the sample container, etc.

Preservation: Samples must be received adequately preserved to meet the requirements of the analysis being requested. Click here for a full list of the preservation requirements for the analyses that BAL performs.

Circumstances Under Which Samples Will Not Be Received: Chemically or biologically hazardous samples that BAL personnel are not trained to handle safely or BAL does not have the proper facilities to store, prepare, or analyze safely and/or legally will not be accepted for delivery.