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level: Level 4

Questions and Answers List

level questions: Level 4

Question	Answer
Radiation/ light Source 1 UV 2 VIS	UV 1 DEUTERIUM lamp (ranges 190-350nm) 2 Xenon arc 3 Hg vapor lamp (more intense radiation VIS 1 quartz halogen 2 tungsten lamp (350nm to 900nm)
FUNCTION IS dispersion of energy/light into wavelengths by means of prism/ grating which are further selected by slit	Monochromator/ Radiant Energy Dispersing device
Where we place the cell containing the sample Samples are typically placed in a TRANSPARENT cell, known as a CUVETTE. Cuvettes are typically rectangular in shape; commonly with an internal width of 1 cm. Cuvettes are made of FUSED SILICA or QUARTZ GLASS because these are transparent throughout the UV, visible and near infrared regions. Visible = glass cuvette will do	Sample Compartment
Designed to split the light beam so that the beam passes thru 2 sample compartments, and, in such as double-beam compartment, a blank solution can then be used in one compartment to correct reading or spectrum of the sample. The blank is most commonly the solvent in which the sample is dissolved.	Optics
Usually a photomultiplier tube-> older PHOTODIODES	Diode array instruments Detector
null balance, manually operated, covers spectral range , uv, vis, near ir regions ( from 190 to 1000 nm)	Beckman DU-2 spectrophotometer
direct reading manually operated spectrophotometer (340-950 nm spectral range)	Bausch and Lomb Spectronic 20
Calibration of absorbance scale	BP- potassium dichromate 0.006% w/v solution in 0.005 M H2SO4 235 nm (122.9-126.2) 257nm 9142.4-145.7) 313 nm (47-50.3) 350 nm (104.9-108.2)
Calibration of wavelength scale	5% w/v solution of holmium perchlorate