  |
|
|
Please refer to our most recent annual report for a full description of our quality control program and an evaluation of the most recent data.
Our laboratory's quality control program includes, among other aspects, spikes of environmental samples. The charts below depict the percent recovery of the spiked concentration. Ideally, 100 percent should be recovered. Recoveries of 80 to 120 percent are considered acceptable for most constituents, though a broader range is allowed for some constituents.
Spiked samples are used to determine whether there are interferences in the analysis of a particular sample matrix and their effect on analyte recovery. An aliquot of a sample is "spiked" with a known amount of the analyte of interest and analyzed along with the associated samples. The recovery of the spiked analyte is calculated as the amount of analyte found minus the amount of analyte found in the unspiked sample. Spiked samples are sometimes viewed as a way of measuring the efficiency with which an analyte is recovered from the sample. (source: Manchester Environmental Laboratory Lab User's Manual)
The power of individual spike results to determine interferences is somewhat limited for several reasons. However, over time spike recoveries should average about 100 percent. The plots below may be used to see if there has been a long-term bias in recoveries or inconsistent recoveries over time. Also, changes in precision may be inferred from changes in scatter over time.
If multiple matrix spikes were performed on a given day, only the first will be shown in the plot.
Last updated August 5, 2005 (Charts may have been updated more recently). Questions or comments may be sent to Dave Hallock.
Copyright © Washington State Department of Ecology. See http://www.ecy.wa.gov/copyright.html.
