Heterochromatic stray light in UV absorption spectrometry: a new test method

Abstract

A new method of estimating the amount of heterochromatic stray light in UV spectrophotometers is described. The method uses the same solution filters with sharp UV absorption edges as ASTM Test Method E387, but one measures the apparent absorbance of a 10-mm path-length cell in the sample beam relative to a 5-mm cell in the reference beam. Scanning toward shorter wavelengths, one records an apparent absorbance maximum which is a direct measure of the stray light. This method was found to be in satisfactory agreement with the ASTM method in comparative tests of several spectrophotometers at different wavelengths between 200 and 390 nm, using KC1, KI, Nal, acetone, and NaNO(2) solution filters. The new method proved to be simpler, the main advantage being that the apparent absorbance maximum occurs at considerably lower scale values than the corresponding absorbance plateau measured by the ASTM method. This reduces the need for successive attenuations of the reference beam every time the spectrophotometer runs off scale. In many instances the new method required no attenuation at all.

A spectrophotometric study of aqueous Au(III) halide–hydroxide complexes at 25–80°C

“…These bands can both interfere with the LMCT bands being measured and exceed the operational limits of the spectrometer (Mielenz et al, 1982), so a wavelength range must be chosen such that background correction may be successfully applied. Further, these bands undergo a red-shift to higher wavelength with increasing temperature, so the spectral window suitable for high temperature experiments is narrower than for those recorded at 25°C (e.g., Suleimenov and Seward, 2000;Brugger et al, 2001;Liu et al 2002;Migdisov et al, 2006).…”

Complete Theoretical Treatment of the Transmittance Ratio Ultraviolet/Visible Spectrophotometric Stray Radiant Energy Test Method

“…The relative SRE level in a spectrophotometer may be determined via the transmittance ratio spectrophotometric method of Mielenz et al 8 and Fleming. 9 Cuvette path length ratios of a ¼ 10, 5, 4, 2.5, and 2 are used throughout this paper via appropriate combinations of 100 mm, 50 mm, 20 mm, 10 mm, 5 mm, 2 mm, and 1 mm quartz-glass cuvettes.…”

“…Fleming and O'Dea 6 addressed this quandary via the direct transmittance spectrometry samplebased test method so that the SRE could be determined rather than estimated. Fleming 7 generalized the Mielenz et al 8 SRE sample-based test method to include the attenuating effect of the test sample on SRE but did not furnish a means of applying the same. This paper remedies that defect by incorporating the transmittance of the test sample towards SRE (i.e., t) into two separate exact expressions relating the observed differential absorbance of the Mielenz peak (i.e., DA max ) and the relative SRE level (i.e., s) to A, the separately observed monochromatic absorbance of the test sample at the Mielenz peak's wavelength, to t, and to a, the sample beam-to-reference beam cuvette path length ratio.…”

The Role of Photodiode Array Spectrometry in Analytical Chemistry

“…Using Mielenz et al's method [12] a stray light profile was obtained [ Figure 14]. This profile compares favourably with many modern single monochromator conventional instruments.…”