Inter-laboratory Comparison of Selenium in Mine Drainage

Inter-laboratory Comparison of Selenium in Mine Drainage 1West Virginia University, Division of Plant & Soil Science, Morgantown, WV 2Bratton Farm, Princeton, WV, 3Mallard Environmental Services, Shady Sp. WV 4University of Kentucky, Department of Plant and Soil Sciences, Lexington, KY Louis McDonald1, Donglin (Lynn) Huang1 , Ben Faulkner2, Ron Lilly3, and Jason Unrine4

Collection Procedure • Don powder free nitrile gloves at each sample location. • Label each tube with sample ID and indicate lab destination. • Reglove. • Uncap 5 borosilicate tubes and place caps on clean (dedicated plastic wrap). • Immerse all 5 bottles into standing pool or in flowing stream and fill completely. • Cap with no head space. • Place tube in 100 ml zip lock bag and prepare for shipment. Bubble wrap and ship in iced durable cooler overnight or 2 day express or hand deliver. COC sticker on container. • Tubes contain no preservative, sample is not filtered. • 250 ml certified, unpreserved and finally, pre-acidified poly sample bottles will then be filled and transported (also without filtering). * • Duplicate – one blind duplicate per location designated X-001 • Blind Field Blank (DI water supplied by REIC) - accomplished at exact field location at time of sample collection. Designated “B” • Certified Reference Material also submitted as blind sample – designated by “J”

Certified Reference Material ($352/250 ml = $5,330/gallon)

Samples • Eight (8) Total • Five (5) field samples • One (1) field blank • One (1) certified reference • One (1) duplicate field sample • Split five (5) ways for five (5) labs • All labs determined total Se • Se speciation at two (2) labs • Se determined three (3) times on three (3) different days

Samples – expected results • 01 Pond (5-10 µg/L) • 02 Pond (0-10 µg/L) • 05 Pond (0-10 µg/L) • 14 Sediment Channel inlet (5-10 µg/L) • X5 Blind DUPLICATE of 05 Pond • B Blind BLANK (DI Water) (nd) • J Standard Reference Material (11.97 µg/L)

Instrumentation • Graphite Furnace - Atomic Absorption (GF-AA) • Atomic Absorption Zeeman-Corrected(AAZ) • Hydride Generation –Atomic Fluorescence(HG-AF) • Hydride-Generation – Inductively Coupled Plasma(HG-ICP) • Ion Chromatography-ICP-Dynamic Reaction Cell-Mass Spectroscopy(IC-ICP-DRC-MS)

Sample Handling • Certified borosilicate glass bottles, 40 mL, unpreserved • Polyethylene plastic bottles, 250 mL • Preserved (2 mL HNO3) or Unpreserved • Filtered or unfiltered

Interpreting Results • Repeatability – If you send the same sample twice, do you get the same result for both? • Precision – If the same sample is run several times, how close are they to each other? • Accuracy – How close is the result to the ‘true’ value? AccurateNot Precise Not AccuratePrecise AccuratePrecise Image Credit: R. Allen Chem222. UVa

Total Se - Repeatability • One duplicate sample (05) - Are they different? • NO • No significant differences in duplicate sample for any lab. • Conclusion • Same sample submitted twice, you’ll get the same result.

Total Se – Precision CV = coefficient of variation = 100*standard deviation/mean Table 1. CV for CRM * = only two reps

Total Se - Precision Table 2. Mean and range CV for other samples Conclusion – reasonably good precision for all labs.

Total Se - Accuracy Figure 1. Accuracy in determination of Certified Reference Standard.

Total Se - Accuracy • Assume IC-ICP-DRC-MS method = true Table 3. Percent error in determinations of field samples.

Results - Speciation • IC – ICP – DRC – MS

Se fully oxidized Reduced to Se (IV) Se (IV) acidified with HCl Fully Reduced to Se (IV) Aliquot 3 Se (0) +Se (IV) +Se (VI) Aliquot 2 Se (IV) + Se(IV) Results - Speciation • HG - ICP Selenium Sample Aliquot 1 Se (IV)

Results - Speciation • Organic Se (selenocyanate, methylseleninic acid • IC-ICP-DRC-MS = not detected • HG-ICP = not measured • Selenite • IC-ICP-DRC-MS = not detected • HG-ICP = not detected

Results - Speciation • Selenate Table 4. Selenate concentrations in four samples by two instrumental methods

Summary – Total Se • That most labs accurately determined the Certified Standard is promising

Summary – Total Se • That most labs accurately determined the Certified Standard is promising. • That most CVs were small is encouraging • Little variation for different days

Summary – Total Se • The variability in some labs indicates the need for • Certified Standard(s) for mine drainages

Summary – Total Se • The variability in some labs indicates the need for • Certified Standard(s) for mine drainages • Broader use of standard addition method to account for matrix effects.

Summary – Total Se • The variability in some labs indicates the need for • Certified Standard(s) for mine drainages • Broader use of standard addition method to account for matrix effects • Further research into the causes of variability

Summary – Total Se • The variability in some labs indicates the need for • Certified Standard(s) for mine drainages • Broader use of standard addition method to account for matrix effects • Further research into the causes of variability • Continued program of Inter-laboratory Proficiency Testing • High CVs in our results • Replaced parts, now getting significantly better data

Summary – Total Se • The variability in some labs indicates the need for • Certified Standard(s) for mine drainages • Broader use of standard addition method to account for matrix effects • Further research into the causes of variability • Continued program of Inter-laboratory Proficiency Testing • The high CVs in our results • Replaced parts, now getting significantly better results • Work toward developing a SOP for sample handling

Summary – Se Speciation • Selenium speciation is difficult, expensive • Some techniques are limited in their ability • But – speciation defines toxicity and treatment

Recommendations for Users • Insist on a QA/QC plan that convinces you of data quality • Consider spiking samples with and checking recovery in-house • Move toward speciation to guide treatment decisions

Inter-laboratory Comparison of Selenium in Mine Drainage