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Matrix Spike Recoveries
Carrie Miller Cryptosporidium Lab Approval Program
Technical Support Center Standards and Risk Management Division Office of Ground Water and Drinking Water
November 15, 2012 U.S. Environmental Protection Agency 1
Matrix Spike vs Field Samples
• Procedure and limitations • Improved accuracy with Method 1623.1
in challenging water matrices • Observed matrix spike recovery with
Method 1623.1, n = 165
November 15, 2012 2 U.S. Environmental Protection Agency
Matrix Spike Procedure
• Mix sample continuously • Spike with pre-determined number of
Cryptosporidium oocysts • Perform Method 1623 or 1623.1 • Compare number detected with quantity added • Typically two matrix spikes for each source
November 15, 2012 3 U.S. Environmental Protection Agency
Matrix Spike Limitations
• Method variability • Matrix interference • Assumption
– spiked sample recovery = field sample recovery
November 15, 2012 4 U.S. Environmental Protection Agency
Method 1623 Variable in Reagent Water
November 15, 2012 5 U.S. Environmental Protection Agency
Blind Spike Average, Method 1623 ~50 Laboratories
Tennessee River Sediment Diatomaceous Earth
U.S. Environmental Protection Agency November 15, 2012 6
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MS Recoveries Round 1 Method 1623 n=3,335
November 15, 2012 U.S. Environmental Protection Agency
8 November 15, 2012 U.S. Environmental Protection Agency
Method 1623.1 Variable in Reagent Water
9 November 15, 2012 U.S. Environmental Protection Agency
Improved Accuracy in River Matrix
10 November 15, 2012 U.S. Environmental Protection Agency
November 15, 2012 U.S. Environmental Protection Agency 11
Matrix Spike Results in Method Validations
Improved Recovery in Challenging Matrices
November 15, 2012 12 U.S. Environmental Protection Agency
Multi-Laboratory Improvement with Challenging Matrix
November 15, 2012 13 U.S. Environmental Protection Agency
14
Observed Matrix Spike Recovery With Method 1623.1 n=165
November 15, 2012 U.S. Environmental Protection Agency
Summary
Matrix spike recoveries with Method 1623.1 should be more accurate than recoveries with Method
1623 in challenging source waters.
November 15, 2012 15 U.S. Environmental Protection Agency
![UNITED STATES ENVIRONMENTAL PROTECTION AGENCY ... · MSH = Matrix spike recoveries were high (>125%) [% recoveries are in parenthesis] Reported results may be biased high CVH = A](https://img.pdfslide.us/doc/110x75/5e73c6d5f298d92b77630f69/united-states-environmental-protection-agency-msh-matrix-spike-recoveries.jpg)
