TNI Logo The NELAC Institute

Standard Interpretation



SIR #: 10006
Standard: 2003 NELAC
Section: 5.5.5.2.2.1 (d)
Link to relevant standard

REQUEST:

The section in question states:
d) All initial instrument calibrations must be verified with a standard obtained from a second manufacturer or lot if the lot can be demonstrated from the manufacturer as prepared independently from other lots. Traceability shall be to a national standard, when commercially available. Our question is, does the requirement for second source standard include calibration curves for surrogate compounds?

TNI FINAL RESPONSE:

(Quality Systems Expert Committee / NELAP Board, 10-11-09)

Surrogates are intended to provide a measure of recovery for every sample matrix (D.1.1.3.3 a). A second source check is designed to assure that the analytes of concern are being correctly identified and quantified. Since surrogates are not analytes of concern, and may be held at a constant level in a calibration curve, they are not required to be verified by a second source.