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An International Evaluation of Holmium Oxide Solution Reference Materials for Wavelength Calibration in Molecular Absorption Spectrophotometry

An International Evaluation of Holmium Oxide Solution Reference Materials for Wavelength Calibration in Molecular Absorption Spectrophotometry

John C Travis, Joanne C Zwinkels, Flora Mercader, Arquímedes Ruíz, Edward A Early, Melody V Smith, Mario Noël, Marissa Maley, Gary W Kramer, Kenneth L Eckerle, David L Duewer

Anal Chem. 2002 Jul 15;74(14):3408-15.

PMID: 12139047

Abstract:

Commercial spectrophotometers typically use absorption-based wavelength calibration reference materials to provide wavelength accuracy for their applications. Low-mass fractions of holmium oxide (Ho2O3) in dilute acidic aqueous solution and in glass matrixes have been favored for use as wavelength calibration materials on the basis of spectral coverage and absorption band shape. Both aqueous and glass Ho2O3 reference materials are available commercially and through various National Metrology Institutes (NMIs). Three NMIs of the North American Cooperation in Metrology (NORAMET) have evaluated the performance of Ho3-(aq)-based Certified Reference Materials (CRMs) under "routine" operating conditions using commercial instrumentation. The study was not intended to intercompare national wavelength scales but to demonstrate comparability of wavelength measurements among the participants and between two versions of the CRMs. It was also designed to acquire data from a variety of spectrophotometers for use in a NIST study of wavelength assignment algorithms and to provide a basis for a possible reassessment of NIST-certified Ho3+(aq) band locations. The resulting data show a substantial level of agreement among laboratories, instruments, CRM preparations, and peak-location algorithms. At the same time, it is demonstrated that the wavelength comparability of the five participating instruments can actually be improved by calibrating all of the instruments to the consensus Ho3+(aq) band locations. This finding supports the value of absorption-based wavelength standards for calibrating absorption spectrophotometers. Coupled with the demonstrated robustness of the band position values with respect to preparation and measurement conditions, it also supports the concept of extending the present approach to additional NMIs in order to certify properly prepared dilute acidic Ho2O3 solution as an intrinsic wavelength standard.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
LS75201	Holmium wavelength calibration standard			Price

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