Standard Reference Materials SRMs 2241 through 2243 are certified spectroscopic standards intended for the correction of the relative intensity of Raman spectra obtained with instruments employing laser excitation wavelengths of 785 nm, 532 nm, or 488 nm/514.5 nm. These SRMs each consist of an optical glass that emits a broadband luminescence spectrum when illuminated with the Raman excitation laser. The shape of the luminescence spectrum is described by a polynomial expression that relates the relative spectral intensity to the Raman shift with units in wavenumber (cm(-1)). This polynomial, together with a measurement of the luminescence spectrum of the standard, can be used to determine the spectral intensity-response correction, which is unique to each Raman system. The resulting instrument intensity-response correction may then be used to obtain Raman spectra that are corrected for a number of, but not all, instrument-dependent artifacts. Peak area ratios of the intensity-corrected Raman spectrum of cyclohexane are presented as an example of a methodology to validate the spectral intensity calibration process and to illustrate variations that can occur in this measurement.

Oxygenates are added to gasoline to reduce exhaust emission levels of carbon monoxide and to boost octane. The U.S. National Institute of Standards and Technology (NIST) provides 12 Standard Reference Materials (SRMs) for single oxygenates in reference gasoline. A previous study demonstrated the feasibility of nondestructively quantifying oxygenate concentration in SRM gasoline ampules using near-infrared (near-IR) spectroscopy combined with multivariate calibration techniques. A drawback of this approach has been that an average prediction uncertainty, rather than a sample-specific one, is obtained. Recent developments in multivariate calibration theory for prediction error variance cure this problem. This report characterizes the significant sources of uncertainties in multivariate calibration using principal component regression and partial least-squares, validating near-IR and other multivariate spectroscopic techniques for use in assigning certified values (expected value with specified uncertainty) to selected materials. This report interprets prediction results in terms of multivariate analytical figures of merit, enabling the visualization of complex multivariate models as univariate graphs.

Oxygenated fuels are gasolines blended with alcohol or ether additives. The U.S. National Institute of Standards and Technology (NIST) provides eight oxygenated gasoline standard reference materials (SRMs) each containing one of four oxygenates at both the 2.0% and 2.7% oxygen mass fraction levels in 20-mL sealed glass ampules. In this study, FT near-IR and FT Raman spectroscopic methods were investigated to nondestructively identify and quantitate the oxygenate concentration in ampules of SRM gasoline. The samples contained any one of the four SRM oxygenates, MTBE, ETBE, TAME, or ETOH. In addition, dual-oxygenate mixtures were examined. The multivariate, statistical calibration technique, partial least-squares, was employed for both near-IR and Raman data to obtain calibration methods to predict the mass fraction of the oxygenate in these gasoline samples. Both spectroscopic techniques were able to unambiguously identify the oxygen additives and quantitate oxygen concentration to an accuracy within 0.1% oxygen mass fraction.

NIST standard reference material (SRM) 2373 was developed to improve the measurements of the HER2 gene amplification in DNA samples. SRM 2373 consists of genomic DNA extracted from five breast cancer cell lines with different amounts of amplification of the HER2 gene. The five components are derived from the human cell lines SK-BR-3, MDA-MB-231, MDA-MB-361, MDA-MB-453, and BT-474. The certified values are the ratios of the HER2 gene copy numbers to the copy numbers of selected reference genes DCK, EIF5B, RPS27A, and PMM1. The ratios were measured using quantitative polymerase chain reaction and digital PCR, methods that gave similar ratios. The five components of SRM 2373 have certified HER2 amplification ratios that range from 1.3 to 17.7. The stability and homogeneity of the reference materials were shown by repeated measurements over a period of several years. SRM 2373 is a well characterized genomic DNA reference material that can be used to improve the confidence of the measurements of HER2 gene copy number.

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