Ch 8. Spectrophotometry Flashcards
Does photodiodes can give us the exact wavelength of the light or the exact color or color combination of a light signal? why?
No, it is just sensible to a wavelength range.
what technique/s is used for get detailed information of a light signal?
Spectophotometry
How current spectrophotometer are different from the old versions of the device?
old ones. bulky and expensive. Not considered for biosensors
current ones- small, and cheaper. becoming an integral part
of many sensor and biosensor devices.
what does spectrophotometry measure?
The light intensity absorbed or transmitted through a sample material. (liquid or gas)
what is photometry?
the intensity measurement of a specific wavelength.
what is spectrometry?
The measured intensity through a range of wavelengths.
What is the primary function of a spectrophotometer?
They typically measure the light intensity absorbed , transmitted, scattered, or reflected by a sample at specific wavelengths. generating an absorption spectrum
what are UV/Vis spectrophotometer?
The most common type of spectrophotometer uses UV and Vis light.
what is a FT-IR spectrophotometer?
Measures the absorption of IR light
how does light absorbance (A) is equated?
A=-log I/I_0
how is transmittance (T) equated?
T=I/I_0 | A=-log(T)
Why Absorbance is more common than transmittance?
it is related to the concentration of a specific component. A=εlc
ε :molar absorptivity
l : path length (the distance the light travels through the material)
c : molar concentration of a specific component
Beer-Lambert law.
if we have a solid sample, can be measure its absorbance?
No. In this case, only can be measured the intensity of reflected light using a reflectometer.
What is the difference between and spectrophotometer and a reflectometer?
The main difference is the change in the photodiode placement. A photodiode in a reflectometer is on the same side as a light source. In contrast, a spectrophotometer has its photodiode placed in front of the light source.
what is a absorption spectrum?
it is a plot of A-λ. A is recorded continuously while varying λ. A graph showing how much light a sample absorbs at different wavelengths.
what are the parameter that an oximeter measures?
Oxygen saturation in blood (SpO2%) and heart rate (pulse)
What is spectrophotometry?
A technique that measures the intensity of light absorbed or transmitted through a sample material, often as a function of wavelength
What physiological parameters can a pulse oximeter measure?
Pulse oximeters measure blood oxygen saturation (SpO2) and pulse rate
Define SpO2.
SpO2 is the percentage of oxygen-saturated hemoglobin relative to the total hemoglobin in the blood
Sketch the absorbance spectra of oxyhemoglobin and deoxyhemoglobin. Identify two wavelengths used by a pulse oximeter.
Oxyhemoglobin absorbs more at ~940 nm (infrared), while deoxyhemoglobin absorbs more at ~660 nm (red). These wavelengths are used for SpO2 calculation
What wavelengths does a pulse oximeter typically use?
Red (~660 nm) and infrared (~940 nm).
Describe the principle behind hemoglobin quantification using spectrophotometry.
Different forms of hemoglobin (oxy-, deoxy-, met-) have unique absorbance peaks that can be used for identification and quantification.
What is numerical aperture (NA) in optical fibers?
NA is the sine of the half-angle of the light acceptance cone, defining the fiber’s light-gathering ability.
Why is a miniature spectrophotometer advantageous?
Compact size, affordability, and versatility make it suitable for portable and field applications.
