The Use of Single and Double Blind Performance Test Samples in Evaluating Laboratory Performance

Oral Presentation

Prepared by J. Phillips1, J. Tomalia2
1 - Ford Motor Company, 290 Town Center Drive, FPN Suite 800, Dearborn, MI, 48126, United States
2 - Cadena, Inc., 1099 Highland Drive, Suite E, Ann Arbor, MI, 48108, United States

Contact Information: [email protected]; 313-845-1648


Accurate, defensible, timely and cost effective analytical data is critical to demonstrate environmental compliance. Two specific tools that are helpful for evaluating laboratory performance against these criteria are the single blind (SB) and double blind (DB) performance test (PT) samples. A multi-provider SBPT database for specific laboratories has been developed to monitor and compare performance across laboratories, methods and parameters. Various techniques to present, compare and assess laboratory SBPT performance will be demonstrated. A DBPT program is extremely useful for assessing laboratory performance from project set-up through final reporting of environmental data. The use of an integrated annual DBPT sample program for the past 10 years to evaluate laboratories overall performance will be discussed in detail.

Single blind performance test samples are commonly used by certifying bodies to verify the analytical performance of a laboratory in order to maintain accreditation. A SBPT sample can provide valuable information regarding a laboratory’s analytical method performance against other laboratories for a known concentration sample in a clean matrix. Advantages of the SBPT include; an unadulterated clean matrix, known, true and precise analyte concentrations, and a large number of participating laboratories for statistical evaluation of performance. Disadvantages of the SBPT include; the potential for bias handling of the test sample, the potential for multiple analysis of the test sample on multiple instruments and by multiple methods, a pristine sample matrix which does not challenge method preparation or analytical steps and the non-routine reporting of results.

The advantages of a DBPT include; whole volume samples, real world matrices, realistic analyte concentrations as well as the routine processing and handling of samples. Laboratory performance aspects which can be evaluated with the DBPT include; project set-up, project management, the bottle order process, sample shipping and handling and all method process steps. Additional aspects of laboratory performance which can be assessed include; sample preparation and analytical performance in various matrices, specific program requirements, report content, turn-around-time and cost. The mechanisms for setting up and evaluating a valid DBPT will be discussed. A significant body of data will be presented to demonstrate the utility of the DBPT for a wide variety of sample types for the CWA and RCRA programs.