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Ensuring High Level QA/QC Results in Analytical Chemistry. Development and improvement of analytical methods over 30 years Lian Liang, Cebam Analytical, Inc. The results speak for themselves. Comparing Cebam’s QA/QC Levels and Criteria of EPA 1631 and EPA 1630
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Ensuring High Level QA/QC Results in Analytical Chemistry Development and improvement of analytical methods over 30 years Lian Liang, Cebam Analytical, Inc
Comparing Cebam’s QA/QC Levels and Criteria of EPA 1631 and EPA 1630 for Analyses of Total and Methyl Mercury Precision (RPD, %) Accuracy (Recovery, %) * : Two samples per year **: Long term lab comparison program, 6 samples per year, organized by Health Canada
Is it necessary to pursue QA/QC levels higher than EPA method criteria? It definitely is to meet project needs!
Projects Floodplain methylmercury biomagnification factor higher than that of the contiguous river (South River, Virginia USA) Michael C. Newmana,*, Xiaoyu Xu a, Anne Condon b, Lian Liang c (Environmental Pollution, 159 (2011) 2840e2844) Summary of QC sample results generated by Cebam Cebam has provided Analytical services to this site since 2007
Projects • Project to evaluate mercury removal from contaminated soil • Analysis of methyl and total Hg in warm samples requested worms worms
Projects • Cebam received 30+ samples transferred from another lab that had failed to produce results from the worm samples. • Despite there being very little sample left to analyze, Cebam scraped the remaining tissue off the walls and generated valuable results in limited time (48 hours TAT). • Helped the client to meet their deadline and get their Hg removal work approved. • If we had not improved the methods, we would not have been able to help the client.
How to Approach High QA/QC Levels • Complying QA/QC requirements from DOECAP auditors as a minimum • Improving available methods • Developing new techniques and methods
How Time is Divided at Cebam Analytical 15 % 45 % 40%
Method Improvement and Development Without Research Funding Support • Both EPA and DOE have the Small Business Innovation Research (SBIR), but neither support development/improvement of analytical methods. • It is difficult for small commercial labs to compete with universities or institutes for research funding • In 1999, the American Water Association requested for proposals to develop a method for field isolation of As3+ in waters. • I submitted a proposal, and the proposal ranked the highest, but I did not receive the funding because the funding was intended to support universities.
What I Have Learned • Forget funding and be happy! • Conduct on-going research • Get returns from developed or improved methods.
Pay attention to individual projects, even individual samples, when deciding what to do and how to do it
Homogenization of Difficult Samples by digesting whole samples Whole fish Crayfish Feathers Plant
Difficulties Encountered in Analyzing Samples from Oak Ridge Site for Total Mercury (THg) THg concentration range: Sub-ppt to ppm in a SDG, →106 -fold difference
Effect of Carry-over Contamination from High Level Samples on the Results of Low Level Samples *: Based on 1% memory **: 1.3 ng/L is lowest water quality criterion for the Great Lakes System (Table 4, 40 CFR 132.6); ***: 12 ng is the lowest nationwide criterion (40 CFR 131.36).
Solution • Perform pre-analysis to eliminate positive bias • Analyze samples within the optimum area (red) of the calibration curve of EPA 1631.
Difficulties in Analyzing Oak Ridge Site Samples for Methylmercury(MeHg) • Ratio of methyl Hg to inorganic Hg: (where x can be between 3-6 or even higher) • Ratio for water samples from other sites: 10% to 50% (or even higher) • Using EPA 1630, high inorganic Hg may result in significant positive or negative bias on MeHg results.
Difficulties in Analyzing Oak Ridge Site Samples for Methylmercury (MeHg) • This difference may greatly affect MeHg results because MeHg fractions are already very small fractions compared to inorganic Hg. • Solution: modifying EPA 1630 method to eliminate positive or negative interferences caused by high level inorganic Hg
Improvement Related to EPA Method 1631 and EPA 1630, 1991 to 1994 Liang L., Horvat M., and Bloom N.S., 1994, An improved speciation method for mercury by GC/CVAFS after aqueous phase ethylation and room temperature precollection, Talanta, 41,3,371. Horvat M., Bloom N.S., and Liang L., 1993, A comparison of distillation with other current isolation methods for determination of methyl mercury compounds in low level environmental samples, Part 1: Sediment, Anal. Chim. Acta., 281, 135. Horvat M., Liang L., and Bloom N.S., 1993, A comparison of distillation with other current isolation methods for the determination of methyl mercury compounds in low level environmental samples, part 2: Water, Anal. Chim. Acta. 282,153. Liang L., and Bloom N.S., 1993, Determination of total mercury by single-stage gold amalgamation with cold vapor atomic spectrometry, JAAS, 8,591 Liang L., Bloom N.S., and Horvat M., 1994, Simultaneous determination of mercury speciation in biological materials by GC/CVAFS after Ethylation and room temperature precollection, Clin. Chem., 40,4,602. All published techniques are included in EPA 1631 and 1630.
Rewards From On-going Research Most of the method development and improvement has been presented at various ICMGP, and drawn great attention worldwide For example, after the 4th ICMGP (1996), using developed methods for analysis of Hg in crude oils, Cebam has provided services to almost all oil companies in the world.
Oil refinery facilities Mercury in Crude Oil • Environmental impacts • Industrial issues • Damage refinery facilities due to Al + Hg → Al•Hg (amalgam) • Poisonous catalysts in refinery processes • Crude oil price is dependent on Hg concentrations
Status of oil Hg in Analytical Chemistry Before 1993 • Both Hg and the matrix are volatile, reactive, and complex. • Lack of reliable, sensitive analytical methods • Historically, the mercury content in crude oil was overestimated up to • 20 000 µg/kg
Crude Oil Hg Related Work • Develop wet extraction method in 1993 • Develop combustion based methods in 1995 • Present combustion/wet extraction methods at 4th ICMGP in 1996 • Applied combustion method for crude oil Hg projects of USEPA and Environment Canada, 2003-2005 • Published 8 crude oil Hg relevant peer review articles, 1996-2007 • Made important contribution to establishment of background level of crude oil Hg in the United States for the EPA • Took the background level from 1000s µg/kgto 3.5 ±0.6 µg/kg
Cebam holds a long term project from NYDEC for analysis of biota samples for: • THg, MeHg, As, Se, Pb, Cd, and Ni • Because Cebam’s results are ranked No. 1 in the Inter-Lab comparison study. • Cebam relies on wet chemistry based methods for isolation and pre- concentration of trace metals prior to detection using instruments • Most other labs rely on ICPMS
Wet Chemistry Methods are Reliable 30 years ago, I worked as the head chemist for an environmental lab at CDC of Guangxi province in China.
When China first opened their doors to the world, the USEPA helped China to establish QA/QC for environmental monitoring. • Each province received 3American Standard Samples in 3 ampoules for three group analytes, • Trace Metals • Demand • Nutrients • All parameters in three USA PE samples were analyzed using wet chemistry methods.
Colorimetric Method With or Without Spectrophotometer. Blank 1 ug/L 3 ug/L 5 ug/L 7 ug/L 9 ug/L sample Standard curve: blank, 1, 3, 5, 7, 9 µg/L of the analyte Principle: Add a reagent to sample solution to form complex with a specific color. Then determine the concentration by looking at which color is most similar with the sample, here it’s 3 µg/L
Determination of Arsenic Based on Hydride Generation Principle: As5+ Sn2+ +I1-→ As3+ Sn2+ + HCl → H2↑ As3++ H2↑ → AsH3↑ AsH3↑ + HgBr2 → As2Hg3 (orange/brown mix color) Sample Standard curve: HgBr2 Saturated paper AsH3 generator Samp. Blank 1 ug 2 ug 3 ug 4 ug 5 ug
Sample Volumes for Analysis of Metals byColorimetric Method, 1982 Total sample volume was 1000 mL sample from dilution of a USA PE sample. No sample available for QC (dup/spike).
In 1982, my team in China analyzed US PE samples for 36 analytes using classic wet chemistry methods. • We got a score of 87 out of a possible 100, indicating classic wet chemistry methods are reliable.
Determination of gadolinium in biological materials using graphite furnace atomic absorption spectrometry with a tantalum boat after solvent extraction Liang L., D'Haese P.C., Lamberts L.V., Van de Vyver F.L., and De Broe M.E. Analytical Chemistry, 63,423, 1991 Lanthanoids • Gd-DOTA complex is used as a contrast agent for magnetic resonance imaging • It is used for tumor screening
Trace Metal Lab at Department of Nephrology-Hypertension, University of Antwerp, Antwerp, Belgium, 1991
Gd Chemistry • Gadolinium is a rare-earth metal which easily forms carbonate with the carbon in graphite furnace • This results in difficulties in atomization using • GFAAS method. • Solution: make a boat using high temperature metal-Ta- and inserting it into the graphite furnace to prevent the sample solution from coming into contact with the furnace • This eliminates the formation of carbonate