Interlab comparison study
With 66 participants each year for the last two years, this study continues to be the largest of its kind. You can download reports from previous years here: 2011, 2012, 2013, and 2014.You have been included in this email because of your participation in previous studies or because of your laboratory’s capabilities to measure THg and/or MeHg.
The study setup for 2015 will be largely the same as in previous years. Participating laboratories will receive nine 500 mL water samples in fluorinated polyethylene (FLPE) bottles. The samples will be collected from freshwater and coastal marine sites (at least one marine sample will be included) in the USA. Samples will be labeled as to whether they are freshwater or saltwater. Samples will be passed through 0.45 µm filters and preserved with 0.4% (v/v) trace metal grade hydrochloric acid (freshwater) or 0.2% (v/v) trace metal grade sulfuric acid (saline water), for analysis of total and/or methylmercury, depending on your laboratory’s capabilities. Please note: no mercury amendments (spikes) are added to these samples, so they generally contain fairly low levels of THg and MeHg (see previous year reports for examples). Studies have shown that measuring spiked mercury in intercomparison samples is less challenging than analyzing native mercury and likely overestimates between-lab precision (see Table 4 in this poster for a review of published data), which is why we do not spike samples in this study.
Prices have not increased since last year. For labs in the U.S., the total cost of participation is $275, including shipping. For labs in Canada, the total cost, including shipping, is $300. For labs in all other countries, the total cost of participation is $350, including shipping. Brooks Rand conducts this study as a service to the mercury analysis community and does not make any profit from it.
Samples will be shipped via FedEx Standard Overnight or International Priority on Monday, 2 February 2015. Samples must be analyzed and results reported no later than Monday, 2 March 2015, 28 days after the samples are shipped. Results reported outside of this window will generally not be included in the data analysis.
Results are reported to EcoChem, Inc., a neutral third party data handler with no affiliation to Brooks Rand. EcoChem will remove identifying information and assign each lab a unique code before forwarding the data to Brooks Rand for analysis. The report that will be released upon completion of the study will identify data by lab code only. Each participating lab will receive an email from the data handler with their own code.
Results from this study (with anonymity ensured) will be provided to all participants and will be submitted for presentation at conferences and publication in peer-reviewed journals.
This year, we are including an extra, optional additional comparison for THg to explore the effect of analyzing THg and MeHg on aliquots of sample from the same bottle. Braaten et al. 2013 (doi: 10.1080/03067319.2013.823489) found that pouring out an aliquot from a HCl-preserved freshwater sample for MeHg analysis and subsequently adding bromine monochloride (BrCl) to the original sample bottle for THg analysis can lead to a positive bias in the results. We aim to test this by sending out duplicate sample sets to those who opt to participate in this extra comparison. With one set, each participant will pour off an aliquot for MeHg analysis into a separate bottle and add BrCl to the original bottle for THg analysis. With the other set, each participant will add BrCl to the whole sample in the original bottle and analyze it for THg only. There is an additional fee of $125 to participate in this extra THg comparison, to cover the costs of the extra supplies, shipping, and data handling fees. I plan to write up the results of this extra THg comparison in a manuscript for submission to a peer-reviewed journal, in collaboration with Hans Fredrik Veiteberg Braaten, and to offer coauthorship credit to all participants. If you are interested in participating in the extra THg comparison, select the appropriate registration option on the registration page.
Once you have submitted your registration form and payment, you will receive an email confirmation of your registration. You will also receive more detailed instructions for study participation closer to the sample ship date.
Please contact me with any questions.
Sincerely,Joel Creswell, Ph.D.
Director of Research & Development