Chemical Processes & Instrument Development: Instruments

Ultra-violet/visible Spectrometer with Charge Coupled Device (UV(CCD)/vis Spectrometer)

UV(CCD)/vis Spectrometer
A princeton instruments Pixis 2k charge coupled device (CCD) allows for determining accurate UV absorption spectra (2048 x 512 imaging pixels; 13.5 x 13.5-mm pixels).

UV(CCD)/vis Spectrometer
Jacketed 90 cm pathlength absorption cell (in black) alongside a 100 cm absorption cell used for single wavelength absorption measurements.

schematic
Schematic of a UV-CCD measurement in a jacketed 50.4 cm UV cell combinated with a single wavelength (228 nm) absorption photodiode measurement through a 20.4 cm cell.

schematic
Schematic of a UV-CCD measurement in a jacketed 90 cm UV cell combinated with a single wavelength (254 nm) absorption photodiode measurement through a 50 cm cell.

Principle of the Measurement

UV/vis spectroscopy is principally governed by Beer's law, which states that the absorbance of a compound is proportional to the concentration of the compound multiplied by the pathlength of the absorption cell and the UV cross section at a particular wavelength.

Technical Specifications

Bandwidth: ~300 nm
Accuracy: ± 5 x 10-4 absorbance
Wavelength calibration: ± 0.1 nm

Applications

UV spectroscopy: monitoring and quantification of transient species, low volatility compounds, stable species, synthesized samples, and gas concentrations in kinetics measurements

Key Publications

McGillen, M.R., V.C. Papadimitriou, S.C. Smith, and J.B. Burkholder, FC(O)C(O)F, FC(O)CF2C(O)F, and FC(O)CF2CF2C(O)F: Ultraviolet and infrared absorption spectra and 248 nm photolysis products, Journal of Physical Chemistry A, doi:10.1021/acs.jpca.0c04607, 2020.

Papanastasiou, D.K., V.C Papadimitriou, D.W. Fahey, J.B. Burkholder, UV absorption spectrum of the ClO dimer (Cl2O2) between 200 and 420 nm, Journal of Physical Chemistry A, doi:10.1021/jp9065345, 2009.

Marshall, P., V.C. Papadimitriou, D.K. Papanastasiou, J.M. Roberts, and J.B. Burkholder, UV and Infrared absorption spectra and 248 nm photolysis of maleic anhydride (C4H2O3), Journal of Photochemistry and Photobiology A: Chemistry, doi:10.1016/j.jphotochem.2019.111953, 2019.