UV-VIS Spectrophotometers - "Still a Rich Area for Innovation"

Despite the technique’s maturity, ultraviolet and visible (UV-Vis) spectroscopy has been a fertile area for innovation. The continuous xenon light source, which operates from UV to near-infrared, has been an enabling technology for UVVis, says Michael W. Allen, Ph.D., marketing manager for NanoDrop UV-Vis and fluorescence products at Thermo Fisher Scientific (Madison, WI). Xenon lamps replace older tungsten and deuterium lamps, which require extremely stable power supplies to deliver quality data.

The xenon flash lamp, a full-spectrum single source, remains on only during data acquisition. “This makes it a very long-lived source,” says Dr. Allen. Thermo offers xenon flash lamps in most of its mid- to high-end UV instruments, as do most other vendors, who continue to sell tungsten and deuterium continuous-source lamps as well.

Another push has been to make instrument footprints smaller. Part of that trend has been the introduction of micro-volume instruments that generate full UV-Vis spectra on microliter-sized samples.

Micro-volume spectroscopy preserves precious samples, but that is not the driver for adopting this format, Dr. Allen says. “The critical factor is the convenience of not having to prepare a cuvette, pipette in the sample, wait for the spectrum to run, and clean out the cuvette when it’s all over.” These workflow complications represent a barrier to fully utilizing traditional cuvette measurements for higher throughput applications, he says.

Unlike methods such as infrared and chromatography-mass spectrometry, UV-Vis is suited to analyzing known compounds. “The method’s bread and butter is concentration measurements,” Dr. Allen explains. Obtaining more information out of a UV-Vis spectrometer, particularly in a field application, requires additional reagents or sample preparation. Even then, it comes nowhere close to “gold standard” techniques for unknown compound identification, like NMR and mass spectrometry.

Yet software and automation improvements have helped to turn UV-Vis instruments into true analyzers, as opposed to standalone instruments.

“Instrument makers have to focus not on the science and the spectroscopy, but on helping users get answers. That’s where the field is going,” says Dr. Allen.

For the vast majority of routine UV-Vis applications, adapting instrumentation for ease of use is the overriding trend.

UV-Vis instruments have become smaller as a result of microelectronics miniaturization, but were always limited by the instrument’s components and pathways used for delivering radiation and measuring absorbance or transmittance.

Rob Morris, director of marketing at Ocean Optics (Dunedin, FL), sees bright days ahead for even more miniaturization and integration into what he terms Star Trek “tricorder-like” devices. Such handheld instruments might use filtering technology or spectral sensing to monitor just a few wavelengths (versus providing a full spectrum) for niche field applications. Connectivity to the Internet and radically redesigned user interfaces could help create virtual UV-Vis networks from nodes around the globe, with spectral libraries residing in the cloud.

Another change he sees is bundling all computing with the handheld instrument to eliminate the computer box altogether. One could imagine creating a global map of atmospheric conditions, such as ozone concentrations, from strategically placed cell phone-sized devices.

Cary 60

Features improved performance, ease-of-use and sample handling
Designed to enhance workflow in a wide variety of settings
Very low-cost, with a xenon lamp that typically lasts ten years
Superior fiber-optics capabilities allow for remote sampling of everything from bulk solutions to cold biological samples

Agilent
www.agilent.com

Libra

New sample handling options add increased capability and scalability
5-position thermostatted cell changer automatically measures samples that are at a controlled temperature
Other available accessories include a variable pathlength cell holder, automatic
snipper system, peltier thermocirculator, film holder and test tube holder

Biochrom
www.biochrom.co.uk

6800

Now available with comprehensive IQ/OQ documentation
Covers the UV/visible wavelength range from 190 to 1100nm
Double-beam provides stable optics and a 1.5nm spectral bandwidth for excellent resolution and accuracy
Includes a comprehensive range of measurement modes

Jenway
www.jenway.com

Torus

Features a flat field optical design and reflective holographic concave grating to disperse light
Features optical resolution of <1.6 nm FWHM with a 25 μm slit installed in the optical bench
Operates in the Visible range (360 to 825 nm), delivering low stray light and ideal for measuring color
Suitable for low-light applications

Ocean Optics
www.oceanoptics.com