Lab Capabilities

Ready to send us samples? Download our Analytical Service Request form and Shipping Container Inventory form to include with your shipment. Please also contact the laboratory to ensure someone will be available to receive your shipment – especially for perishable materials. 

Analytical methods 

All our analytical methods and SOPs undergo annual internal review and are based on established procedures published in the peer-reviewed literature. For a complete list of analytical methods with accompanying SOPs and reference information, please click here.   

Laboratory Processing 

We offer multiple sample processing procedures at the USGS MRL and will tailor them to your project needs. Two of the most common procedures are in-lab filtration of waters and Lyophilization & homogenization of solid samples.  

In-lab filtration is typically performed on raw water samples, resulting in the separation of the sample into two phases: filter-passing and particulate matter. Several filter pore-sizes are available depending on your application. The mass of particulate matter captured, and the volume of raw water passed through the filter will be recorded. This data is used to calculate the particulate-bound mercury as both nanograms per liter of sample and nanograms per gram of solid. Standard filtration occurs under vacuum in our trace-metal clean lab using acid-cleaned Teflon equipment.  

Lyophilization & homogenization of biological tissues, plants, soils, or sediments is typically performed prior to mercury analysis. Solid sample data is reported on a dry-weight basis, along with the fraction solid (soil/sediment) or moisture (tissue) for conversion back to the original wet-weight concentrations. After receipt at the lab, solid samples are stored frozen until lyophilization (freeze-dried) and then they are homogenized by ball mill, rotary blades, or mortar and pestle. Throughout processing and storage, samples are protected from ambient moisture using a cabinet-style desiccator and Teflon-sealed glass vials. Any remaining sample is archived in perpetuity for future use.    

Quality Assurance 

The USGS MRL has been a leader in data traceability and quality assurance.  All samples are assigned a unique ID at the time of sampling or upon arrival at the laboratory. Sample information and analytical results are tied to the unique ID in our laboratory information management system. Analytical instrumentation is calibrated daily and each batch of samples includes a series of blanks, check standards, replicates, spikes and certified reference material to validate the results. For a complete description of our Quality Assurance plan, please click here.  The plan covers sample preparation, collection, and handling, as well as laboratory reagents, instrumentation, analysis, and documentation. Strict adherence to the quality control and quality assurance procedures described in this manual is our guarantee for delivering high-quality research and data. We are also implementing each aspect of the USGS Quality Management System as the rules are finalized and become available.  

Laboratory Workflow 

Immediately upon receipt at the laboratory, sample containers are checked against the Cooler Inventory form and Analytical Services Request forms. The forms are dated and signed by the person responsible for log-in of the samples. A log-in number is assigned to each sample container that relates the bar code to the project and site, date, time, and depth of collection.  

Sample information is entered into the database. Used or dirty sampling equipment is rinsed with tap water in the prep room and placed in bins to await cleaning. Samples requiring refrigeration or freezing upon receipt are handled appropriately and in a timely fashion to preserve their integrity.  

Samples are processed according to laboratory procedures and analysis type methods. Samples are tracked throughout processing using the bar code on the sample container.  

At any time before you receive lab results, if you determine that the site name, station ID, or other information on the Request for Analysis form is incorrect, contact the Lab immediately at mercury@usgs.gov.  

Data delivery: Lab analysis results are uploaded to our local database about every 4-6 weeks. You will receive an email message that your results are available.  If you have an NWQL customer code, your results will be uploaded into QWDX (qwdata). If you do not have a NWQL customer code, your results will be supplied as an Excel file email attachment. Questions about the following data results should be directed to John DeWild:  

• data unavailable  

• cannot access data  

• discrepancy in data results  

• missing or incomplete data in QWDX or XLS file  

• need to get different format of data  

• QA reports are currently generated for customers on request.

USGS MRL quality assurance reports are prepared by the Quality Assurance Officer and submitted to the project chiefs to ensure that QA/QC objectives are met. Quality assurance reports include:  

• an assessment of precision, accuracy, and completeness for each project,  

• significant quality control problems and the status of corrective action,  

• the results of QA performance audits, and  

• any changes to the QA Manual.  

Instrumentation  

The USGS MRL houses state-of-the-art instrumentation for the quantification of mercury in environmental samples. Major pieces of equipment are described below. Note: Commercial names are used for informational purposes only and do not represent an endorsement by the USGS, the US Department of the Interior, nor the Federal Government. 

Brooks Rand Total Mercury Manual System 

Model III Cold Vapor Atomic Fluorescence Spectrophotometer coupled with a Model TDM-II trap desorption module manufactured by Brooks Rand Instruments. This instrumentation is operated by the manual exchange of sorption traps for sample loading and subsequent trap desorption. Conforms to US EPA method 1631. Instrumentation is utilized for the analysis of total mercury in water. 

Brooks Rand Merx-T Automated Total Mercury System 

Model III Cold Vapor Atomic Fluorescence Spectrophotometer coupled with a MERX Total Hg Purge & Trap Module and a MERX autosampler – all manufactured by Brooks Rand Instruments. This instrumentation automates sample loading and trap desorption. Conforms to US EPA method 1631. Instrumentation is utilized for the analysis of total mercury in water, tissue, and soil/sediment. 

Brooks Rand Merx-M Automated Methylmercury System 

Model III Cold Vapor Atomic Fluorescence Spectrophotometer coupled with a MERX Methyl Hg GC & Pyrolysis Module, a  MERX Methyl Hg Purge & Trap Module, and a MERX autosampler – all manufactured by Brooks Rand Instruments. This instrument automates sample loading and trap desorption. Conforms to US EPA method 1630. Instrumentation is utilized for the analysis of methylmercury in biological tissue. 

Shimadzu TOC analyzer 

Model: TOC-VCSH manufactured by Shimadzu Corporation. This organic carbon analysis instrument features combustion and catalytic oxidation of the sample before non-dispersive infrared detection. This instrumentation is utilized for the analysis of total organic carbon in filter-passing water. 

Nippon MA-3000 Direct Combustion Analyzer 

Model: MA-3000 manufactured by Nippon Instruments Corporation. This automated instrument operates by direct sample combustion, sorption trap capture and subsequent trap desorption. Detection is by atomic absorbance. Conforms to US EPA method 7473. Instrumentation is utilized for the analysis of total mercury in soils/sediments and tissues.  

Thermo Scientific ICP-MS 

Model: iCAP RQ Inductively coupled plasma mass spectrometry instrumentation manufactured by Thermo Scientific. Instrumentation receives gaseous output from the Merx-T and Merx-M systems and measures isotopically enriched methyl and total mercury samples. Methylmercury quantification is by isotope dilution, total mercury quantification is by direct analysis. Instrumentation is utilized for the analysis of methyl and total mercury in waters and soils/sediments.    

Thermo Scientific MC-ICP-MS 

Model: Neptune XT multi-collection inductively coupled plasma mass spectrometry instrumentation manufactured by Thermo Scientific. The Neptune MC-ICP-MS is configured specifically for total mercury isotope analysis and is exclusively used for this purpose. Sample introduction is through a custom gas-liquid phase separator which additionally includes internal standardization with thallium. Instrumentation is utilized for the high-resolution isotope analysis of total mercury in soil/sediment, tissue, and water.  

Horiba Aqualog EEMS Analyzer 

The Aqualog simultaneously measures both absorbance spectra and fluorescence Excitation-Emission Matrices in aqueous samples.  Data from this instrument is used in combination with that of the TOC analyzer to determine the Specific UV Absorbance (SUVA) of organic carbon in filtered water. SUVA is a measure of the aromatic character of dissolved organic carbon and is related to the chemical functionality and type of carbon (allochthonous or autochthonous).