NEW YORK STATE DEPT. OF HEALTHWADSWORTH CENTER

ENVIRONMENTAL LABORATORY APPROVAL PROGRAM

PROFICIENCY TESTING

HISTORY

1985 NYS ELAP established, with PT as an integral part.

1989 Program expanded to include full-volume solid waste samples

Current Status All analytes offered for accreditation by NY ELAP are proficiency tested if they are on the NELAC PT FOT list (except CN in SW)

Restricted to Potable and Non-Potable Water. All WS and WP analytes tested + many more

ANALYTES OFFERED TWICE YEARLY

POTABLE WATER: 137 (Asbestos by TEM is available to laboratories that are not NY ELAP

accredited)

NON-POTABLE WATER: 173

WATER BACTERIOLOGY: 4

AIR: 4

STATISTICAL TECHNIQUES FOR SAMPLE VERIFICATION

1. Verification of Prepared Value

• 5 samples for each parameter are analyzed in duplicate • Mean and standard deviation calculated• Prepared value verified if mean and standard deviation are within prescribed limits

[NIST Handbook 150.19, June 1999, 285.33(h)(5)]

STATISTICAL TECHNIQUES FOR SAMPLE VERIFICATION

2. Verification of Homogeneity

• 1 sample is collected at the beginning, ¼, ½, ¾, and finish of each prep. run• Each sample is analyzed in duplicate • One-tailed ANOVA applied: between sample set and within sample variances are compared

[NELAC Chapter 2, B.3.2]

STATISTICAL TECHNIQUES FOR SAMPLE VERIFICATION

3. Verification of Stability

• After the close of the study, 5 samples for each parameter are analyzed• Stability verified if mean is within prescribed limits of pre-distribution prepared value

[NELAC Chapter 2, B.5]

STATISTICAL TREATMENT OF PT DATA

All scoring conforms with NELAC requirements:

• Regression equations• Fixed acceptance limits • Statistical evaluation of study data

REPORTING

Report forms contain the following information:

• Matrix• Analyte Name• Concentration Units • Sample id• Method• Result• Mean/Target• Warning Limits (+/- 2 sd)• Acceptance Limits• Score (Satisfactory or Unsatisfactory)• X labs passed out of Y reported results

ADDITIONAL INFORMATION AVAILABLE TO ALL LABS AND ACCREDITING AUTHORITIES

Summary data:

• Matrix• Analyte Name• Concentration Units • Sample id• Target• Reported limits• Robust Mean• Standard Deviation• Median• Number of labs passing/ Number of labs failing• Histogram of no. of labs vs. result reported