Product category:
Gas monitoring and analysis
News Release from: Starna Cells | Subject: Starna Stray light
Edited by the Processingtalk Editorial
Team on 06 October 2004
Stray light in UV-visible
spectrophotometry
Track stray light traceably with Starna Stray light: this is an easily undetected source of error in UV-visible spectrophotometry, and when present causes depressed absorbance readings at high values
Track stray light traceably with Starna Stray light (also known as Stray Radiant Power Ratio or SRPR) is an easily undetected source of error in UV-visible spectrophotometry, and when present causes depressed absorbance readings at high absorbance values Instrument manufacturers usually quote stray light at one or sometimes two wavelengths, but it can and will vary over the range of the instrument, so there can be uncertainty about measurement accuracy at other wavelengths
This article was originally published on Processingtalk on 17 Dec 2007 at 8.00am (UK)
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It also often increases with time due to the ageing of optical components and light sources.
Good laboratory practice would therefore suggest that it is important to know the level of stray light as near as possible to the measurement wavelength, and the newly revised Test Method ASTM E387-04 specifies a range of liquid filters that can be used to measure stray light at 6 different wavelengths across the UV and visible spectrum.
Most of the standards are salt solutions.
For long-term stability and reliability it is preferable to seal such test solutions into the cuvettes (cells) that will be used for measurement.
Starna (Hainault, UK) have been supplying heat-sealed solution standards for calibrating spectrophotometers for many years.
However one of the stray light standards - used to check stray light at 280nm, an important wavelength for DNA and protein measurements - is liquid Acetone, so for this Starna have developed a special technique for heat-sealing acetone into the cuvette.
According to John Hammond, Starna Technical and Marketing Manager for Analytical Products, the company is the only supplier that can offer complete sets of sealed stray light standards for E387-04.
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