Instrumentation Flashcards
Calibration is done every
3 months/quarterly
Disinfect centrifuge on a
Weekly basis
Check speed of centrifuge using
Tachometer/Strobe light
Which of the following measures speed
Timer
Strobe light
Tachometer
Minemeasure nito yung concentration ng isang substance sa solution by measuring the absorbed light pagkatapos malagyan ng treatment
Spectrophotometer
Theory of Light Waves
Electromagnetic radiation
Wavelength
Amplitude
Visible light
Photons travelling in waves
Electromagnetic radiation
Distance between two peaks
Wavelength
Distance between peak and trough
Amplitude
Visible light falls in between ____ - ____
400-700nm
Beer’s Law states na yung concentration of a substance is ____ sa amount of light na naabsorb or yung concentration ng substance is ______ sa logarithm of transmitted light
Directly
Inversely
Components of a Spectrophotometer
- Light Source
- Monochromators
- Sample Cell
- Photodetectors
Isolate the desired wavelength
Monochromator
Light Source
1) Incandescent tungsten
2) Deuterium-discharge lamp & Mercury
Most common source of light for work in the visible and near-infrared regions
Incandescent tungsten
Most commonly used for UV work
Deuterium discharge lamp
Monochromators
Prism
Diffraction grating
Interference filter
Colored-glass filters
Most commonly used monochromator
Diffraction grating
Sample cell
Round
Square
Glass
Quartz
Less error from the lens effect, orientation in the Spectrophotometer and refraction
Square
Used for applications in the visible range
Glass
For applications requiring UV radiation
Quartz
Photodetectors
Barrier-layer/photocell
Phototube
Photomultiplier
Photoiodide
Least expensive photodetector
Barrier-layer
Used in instruments designed to be extremely sensitive to very low light levels and light flashes of very short duration
Photomultiplier
Parameters routinely monitored in spectrophotometry
Wavelength/photometric accuracy
Absorbance check
Linearity
Stray Light
Implies that a photometer is measuring at the wavelength that it is set to.
Wavelength or photometric accuracy
Photometric accuracy can be assessed easily using special glass-typr optical filters. Two examples are:
Didymium
Holmium oxide
Didymium glass has a broad absorption peak around
600nm
Holmium oxide has multiple absorption peaks with a sharp peak at
360nm
Performed using glass filters or solutions that have a known absorbance values for a specific wavelength
Absorbance check
The ability of a photometric system to yield a linear relationship between the radiant power incident upon its detector and the concentration
Linearity
The linearity of a spectrometer can be determined using _____ or _____ that have known substances values for a given wavelength
Optical filters or solutions
Any light that impinges upon the detector that does not originate from a polychromatic light source.
Stray light
Stray light can be evaluated by using ______
Special cutoff filters
Meaures the quantity of light reflected by a liquid sample that has been dispensed onto a grainy or fibrous solid support
Reflectometry
Application of reflectometer
Urine dipstick analysis
Dry slide chemical analysis
Measurement of concentration is done by detecting the absorption of electromagnetic by atoms rather than molecules
AAS
Usual light source of AAS
Hollow-cathode lamp
This breaks chamical bonds and form free unexcited atoms that serves as sample cells (instead of a cuvet)
Flame