SPECTROSCOPY
Ocean SR2 spectrometer
SPECTROMETER SUCCESS STORY
Today’s modular spectrometers have demonstrated key performance gains, explains Rob Morris
T
he eff ectiveness of a new CCD- array spectrometer for measuring the absorbance of optical fi lters and potassium dichromate solution
standards was recently evaluated. T e Ocean SR2 spectrometer has a linear CCD-array detector, enhanced electronics for high-speed spectral acquisition (integration times to 10 µs), and excellent SNR (380:1) performance for absorbance measurements, plasma monitoring and other applications. T e following are some examples.
ABSORBANCE OF OPTICAL FILTERS Using an Ocean SR2 spectrometer with a deuterium-tungsten halogen light source and an optical fi lter holder, several colour, balancing and UV blocking fi lters were measured. When compared with a similar model spectrometer for the same measurements, the Ocean SR2 demonstrated higher absorbance values, suggesting lower stray light performance; and better SNR at longer wavelengths, the result of more balanced sensitivity across the spectral range (Fig. 1).
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BELOW: When blue fi lters are measured, the lower noise level of the Ocean SR2 delivers better SNR at longer wavelengths than a comparable spectrometer
Fig. 1.
ABSORBANCE OF POTASSIUM DICHROMATE STANDARDS Potassium dichromate is a crystalline solid typically used as an oxidising agent. Here, researchers used potassium dichromate solution standards to compare Ocean SR2 measurements to the calibrated absorbance wavelengths at 235nm, 257nm, 313nm, 350nm and 430nm. T e setup comprised the spectrometer with a 50 µm slit, a pulsed xenon light source balanced using a fi lter holder and diff user, a 1cm pathlength cuvette holder, and a pair of 600 µm solarisation- resistant optical fi bres. T e Ocean SR2 demonstrated high accuracy, especially at higher concentration measurements (Fig. 2). With absorbance measurements, its makers recommend setting the spectrometer integration time so the reference spectrum peaks at 80%-90% of the full scale of counts. T is takes advantage of the full dynamic range of the spectrometer, which improves SNR. Also, with a spectrometer that produces balanced output across the wavelength range, users can avoid saturating parts of the spectrum – and having to make unwelcome measurement trade-off s.
THE BIGGER PICTURE With absorbance measurements, spectrometer SNR can be the diff erence between excellent results and
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