Challenges in Providing Standard Reference Materials

The NIST Analytical Chemistry Division has supplied transmittance verification and wavelength calibration standard reference materials (SRMs) specialized to the needs of chemical and pharmaceutical spectrophotometric analysis since 1970. Growing demand for UV/visible standards stems from the increasingly routine use of spectrophotometers for pharmaceutical quality control and from the escalation in the documented use of standards for regulatory and voluntary quality control purposes. To meet the demand, NIST is studying ways to accelerate standards production. Projects include studies of the origin of transmittance drift (which necessitates aging during production), investigations of solid UV filters and of sealed liquid standards, and the development of a NIST-Traceable Reference Material (NTRM TM) optical filters program to involve the private sector. Recently, we have revised the optical specifications of our solid filter standards to meet the requirements of reversed-geometry (post-dispersion) instruments. In the near infrared, spectrochemical process control applications mandate the need for wavelength standards to support the stability and instrument-to-instrument transfer capability of multivariate analytical calibration models. We are presently producing one such standard and are investigating others. Finally, we are studying algorithms for locating peaks in wavelength 2 standards to find a consistent means for making wavelength assignments from the UV through the mid-infrared.