The absorbance (also called optical density) of a material is a logarithmic ratio of the radiation falling upon a material, to the radiation transmitted through a material. UV/VIS absorbance measurements encompass a wide variety of chemical and biochemical applications which involve many areas of research and industrial end uses. UV/VIS absorbance can be applied qualitatively and quantitatively in spectroscopic measurement applications ranging from blood parameters to chemical concentrations in process and reaction monitoring.
Fibre-optic spectrometers offer a tremendous value proposition for UV/VIS measurements because of their relatively low cost, small size and ability to be introduced in harsh environments through the fibre interface. Combined with a fibre-optic transmission dip probe, inline flow cells or the more traditional cuvette cell, a fibre-optic spectrometer can accurately and repeatably measure over the range from 200-1100 nm.
Scientists who are largely familiar with more traditional bench top spectrophotometers may have the perception that fibre-optic instruments cannot provide the resolution or stray-light rejection required for more demanding applications. In fact, fibre-optic spectrometer technology has come a long way and Avantes’ instruments are on the leading edge for this technology. Our instruments are capable of measuring at resolutions as high as 0.05 nm in the UV. In terms of stray-light rejection, Avantes has developed a special optical bench called the ultra-low stray-light (ULS) optical bench to provide optimal performance for our customers. AvaSpec ULS spectrometers have stray-light levels as low as 0.04%.
Typically UV/VIS absorbance systems consist of a spectrometer, stabilized light source and fibre optics, which are connected to some form of sampling accessory (probe or cuvette cell). Single fibre-optic spectrometers can be configured for broadband measurements (200-1100 nm) or narrow band (any range from 200-1100 nm) depending upon the desired wavelength range and resolution. Avantes UV/VIS instruments in our StarLine and SensLine are also fully compatible with our AvaSpec NIRLine spectrometers, which enable spectroscopic measurements out to 2500 nm.
Common System Configurations
Avantes modular platform enables users to configure systems in a variety of ways and also allows the flexibility of changing the system configuration later to provide additional functionality. The typical UV/VIS absorbance system consists of an AvaSpec spectrometer, AvaLight fibre-optic light source, fibre cables and a cuvette cell holder. To the left, this system configuration is shown with a cuvette cell holder above with a dip probe configuration below.
Our affordable AvaSpec-ULS2048CL-EVO provides excellent resolution (1.0 nm FWHM) over the entire range from 200-1100 nm, or higher resolution for a shorter-range configuration. For higher-resolution absorbance measurements, we recommend the AvaSpec-ULS4096CL-EVO. Customers who demand higher signal-to-noise performance and higher sensitivity in the UV or NIR should consider Avantes SensLine instruments. The AvaSpec-ULS2048XL-EVO has a high-performance back-thinned CCD detector and the AvaSpec-HERO is Avantes’ highest sensitivity spectrometer, with a thermoelectrically cooled CCD detector and a high numerical aperture optical bench.
Any of Avantes’ instruments can be combined with our AvaLight-DH-S-BAL deuterium halogen source and a CUV-UV/VIS cuvette cell holder. The CUV-DA-DHS is a nice alternative that enables the coupling of the cuvette cell holder directly to the front of the light source to minimize the use of fibre optics.
This same system configuration can be integrated into a single housing (AVS-Desktop) to provide an integrated spectrophotometer module with a shared power supply for the light source and spectrometer.
One of the key value propositions for fibre-optic instruments is the ease with which measurements can be made inline or in-process using a fibre-optic probe or accessory. Avantes offers a variety of sizes and configurations of fibre-optic transmission dip probes, which include special configurations for measurements in high temperatures (up to 500°C), either high pressure or vacuum. Also available are fibre-optic flow cells for standard and micro-fluidic applications.
Instrument Control Software
Avantes proprietary AvaSoft software is a Windows-based 32- and 64-bit compatible software package which enables full instrument control and includes a basic chemometry add-on module (AvaSoft-Chem) which is perfect for UV/VIS absorbance measurements. For customers requiring more sophisticated analytical software, which enables model development and multi-variate analysis, Avantes instruments are fully compatible with Panorama© software from LabCognition.
Avantes has developed a bundle especially designed for UV/VIS/NIR absorbance. This versatile bundle can measure absorbance in most situations and includes everything you need to get started.
These are some of the products mentioned above. To find the perfect setup for your specific application, contact one of our sales engineers for advice.
Below are some detailed application notes on various uses of absorbance spectroscopy in different applications and industries.
Why choose Avantes for your absorbance application?
- High resolution and speed with cooled and uncooled spectrometers
- Feasibility and sample testing at our headquarters in Apeldoorn
- Large assortment of accessories for absorbance including micro flow cells, dip probes and beam splitter/combiners
- Extensive knowledge on absorbance applications