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
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!
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
Pay attention to individual projects, even individual samples, when deciding what to do and how to do it
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).
(where x can be between 3-6 or even higher)
10% to 50% (or even higher)
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,
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.
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.
30 years ago, I worked as the head chemist for an environmental lab at CDC of Guangxi province in China.
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
As5+ Sn2+ +I1-→ As3+
Sn2+ + HCl → H2↑
As3++ H2↑ → AsH3↑
AsH3↑ + HgBr2 → As2Hg3
(orange/brown mix color)
HgBr2 Saturated paper
Total sample volume was 1000 mL sample from dilution of a USA PE sample. No sample available for QC (dup/spike).
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
Trace Metal Lab at Department of Nephrology-Hypertension, University of Antwerp, Antwerp, Belgium, 1991