UV-Visible Spectrometer

1. UV-Visible Spectrometer

Instrument Specification:

It is a PerkinElmer Lambda 25 spectrometer operating in the ultraviolet (UV) and visible (Vis) spectral ranges.

About the Instrument:

The spectrometer feature a double-beam, all-reflecting system. The monochromator is a holographic concave grating with 1053 lines/mm in the centre. Two radiation sources, a deuterium lamp and a halogen lamp, cover the working wavelength range (190 nm to 1100 nm) of spectrometer. It includes two photodiodes as detector one of which is for sample beam and another for the reference beam.

Theory of operation:

The instrument works in principle of Beer–Lambert law. The Beer-Lambert law states that the absorbance of a solution is directly proportional to the solution”s concentration. The method is most often used in a quantitative way to determine concentration of an absorbing species in solution, using the Beer-Lambert law:

A = -log₁₀(I/I₀) = ε.c.L

where A is the measured absorbance, I0 is the intensity of the incident light at a given wavelength, I is the transmitted intensity, L the path length through the sample, and c the concentration of the absorbing species. For each species and wavelength, ε is a constant known as the molar absorptivity or extinction coefficient. This constant is a fundamental molecular property in a given solvent, at a particular temperature and pressure.

http://en.wikipedia.org/wiki/Ultraviolet-visiblespectroscopy

2. Temperature-Controlled UV-Visible Spectrometer (Lambda 25)

About the Instrument:

Peltier based accessories are widely found in UV/VIS spectroscopy. A peltier accessory consists of a semiconductor junction bonded to two ceramic plates to which a DC current is applied. A temperature difference is created between the two plates and causes heat to be “pumped” from the cold side to the hot side – this is known as the “Peltier Effect”. For efficient operation, Peltier systems require a heat dispersal system to remove heat that builds up during operation. PerkinElmer provide peltier thermostatting accessories with two approaches to heat dissipation. The Routine Peltier is fitted with a heat sink and a fan. The Research Peltier accessories use fluid circulation to remove excess heat in the system.

Routine Peltier Accessories

Available as either a single cell holder or a cell-changer the Routine Peltier accessories accommodate up to nine, 10 mm cuvettes. Shorter pathlengths can also be used with the addition of the appropriate spacers.

Research Peltier Accessories (PTPs)

Available as either a single cell holder or a cell-changer, the PTP accessories accommodate up to six, 10 mm cuvettes. Shorter pathlengths can also be used with the addition of the appropriate spacers.