Flashcards in Analytical methods Chapter 5 Deck (88)
What is Spectrophotometric measurement?
It is a measurement of light intensity in a narrower wavelength
What is Photometric measurement?
It is a measurement of light intensity without consideration of its wavelength
Is described as photons of energy traveling in waves
What is the formula of the Beer's law?
Concentration of a substance is directly proportional to the amount of light absorbed or inversely proportional to the logarithm of the transmitted light
What is the use of Light source?
Incident light for the system
What are the common source of light used near infrared regions?
Incandescent tungsten and Tungsten light bulb
What are the alternatives used for UV spectrum?
Deuterium discharge lamp and mercury arc lamp
What is the use of Entrace slit?
It minimizes the unwanted straylight
What is Straylight?
It is a wavelength outside the band which can affect the measurement and cause absorbance error
What is the use of monochromator?
It isolates specific or individual wavelength of light
Kinds of monochromator
Prisms, Diffraction gratings and Interference Filters
The principle of prism
A narrow beam of light focused on a prism is refracted as it enters the more dense glass
Most commonly used monochromator that consists of many parallel grooves
Principle of constructive interference
Light waves enter one side of the filter and are refracted at the 2nd surface
What is the use of Exit Slit?
It controls the width of the light beam or band pass
The narrower the light beam
the greater the resolution
sample cell/ absorption cell/ analytical cell
kinds of cuvet and some definition
Alumina Silica glass- simple/ older
Quartz/ Plastic- used for UV spectrum
Borosilicate glass- can stand increase temperature
Soft glass- Common glass
scatter light and should be discarded
Produces etching and dissolves glass
What is a Photodetector?
It converts Light energy to Photoelectric Energy
Kinds of Photodetectors:
Photocell, Phototube and Photomultiplier tube
Requires external voltage and it gives off electron when light energy strikes it
Simplest detector and no external voltage
On a plate of iron covered with transparent layer of silver
Most common type which can detect low level of light and amplifies radiant energy 200x
What is Sensitivity and Specificity?
Sensitivity is a term that can measure even the smallest movement of light while Specificity is a term that can only detect a specific light
It detects less amount of light and not as sensitive as photomultiplier tube
Phototransistors and Photodiode
moving needle on a dial or a digital display that indicates the amount of light passing