UV-Vis Spectroscopy - Revision history

Dnanji: Dnanji moved page UV-Vis Spectrophotometer to UV-Vis Spectroscopy

2022-11-09T17:01:08Z

Dnanji moved page UV-Vis Spectrophotometer to UV-Vis Spectroscopy

← Older revision		Revision as of 13:01, 9 November 2022
(No difference)

Rzhou95 at 03:08, 6 October 2021

2021-10-06T03:08:29Z

← Older revision		Revision as of 23:08, 5 October 2021
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	{\|class="infobox"		{\|class="infobox"
	!style="font-size:135%;text-align:center;" \| Avantes AvaSpec UV-Vis System		!style="font-size:135%;text-align:center;" \| Avantes AvaSpec UV-Vis System [https://sites.gatech.edu/mse-mill/sop/uv-vis/ [SOP<nowiki>]</nowiki>]
	\|-		\|-
	\|[[File:UVvis-052621.png\|center\|300px]]		\|[[File:UVvis-052621.png\|center\|300px]]

Rzhou95 at 23:35, 17 July 2021

2021-07-17T23:35:40Z

← Older revision		Revision as of 19:35, 17 July 2021
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	{\|class="infobox"		{\|class="infobox"
	!style="font-size:135%;text-align:center;" \| Avantes AvaSpec-~~ULS2048CL-EVO~~		!style="font-size:135%;text-align:center;" \| Avantes AvaSpec UV-Vis System
	\|-		\|-
	\|[[File:UVvis-052621.png\|center\|300px]]		\|[[File:UVvis-052621.png\|center\|300px]]

Amarin32 at 17:12, 17 June 2021

2021-06-17T17:12:17Z

← Older revision		Revision as of 13:12, 17 June 2021
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	A beam of light from a visible and/or UV light source (colored red) is separated into its component wavelengths by a prism or diffraction grating <ref Name = "MSU"> UV-Visible Spectroscopy. (n.d.). https://www2.chemistry.msu.edu/faculty/reusch/virttxtjml/spectrpy/uv-vis/uvspec.htm#uv1. </ref>. Each monochromatic (single wavelength) beam in turn is split into two equal intensity beams by a half-mirrored device. One beam, the sample beam (colored magenta), passes through a small transparent container (cuvette) containing a solution of the compound being studied in a transparent solvent. The other beam, the reference (colored blue), passes through an identical cuvette containing only the solvent. The intensities of these light beams are then measured by electronic detectors and compared. The intensity of the reference beam, which should have suffered little or no light absorption, is defined as <math> I_0 </math>. The intensity of the sample beam is defined as <math> I </math>. Over a short period of time, the spectrometer automatically scans all the component wavelengths in the manner described. The ultraviolet (UV) region scanned is normally from 200 to 400 nm, and the visible portion is from 400 to 800 nm. PMMA, PS, or glass cuvettes are used when the primary wavelengths of interest are in the visible range and quartz cuvettes are used when those wavelengths are between 170 and 300 nm, because they are more transparent to these wavelengths.		A beam of light from a visible and/or UV light source (colored red) is separated into its component wavelengths by a prism or diffraction grating <ref Name = "MSU"> UV-Visible Spectroscopy. (n.d.). https://www2.chemistry.msu.edu/faculty/reusch/virttxtjml/spectrpy/uv-vis/uvspec.htm#uv1. </ref>. Each monochromatic (single wavelength) beam in turn is split into two equal intensity beams by a half-mirrored device. One beam, the sample beam (colored magenta), passes through a small transparent container (cuvette) containing a solution of the compound being studied in a transparent solvent. The other beam, the reference (colored blue), passes through an identical cuvette containing only the solvent. The intensities of these light beams are then measured by electronic detectors and compared. The intensity of the reference beam, which should have suffered little or no light absorption, is defined as <math> I_0 </math>. The intensity of the sample beam is defined as <math> I </math>. Over a short period of time, the spectrometer automatically scans all the component wavelengths in the manner described. The ultraviolet (UV) region scanned is normally from 200 to 400 nm, and the visible portion is from 400 to 800 nm. PMMA, PS, or glass cuvettes are used when the primary wavelengths of interest are in the visible range and quartz cuvettes are used when those wavelengths are between 170 and 300 nm, because they are more transparent to these wavelengths.
	[[File:Typical Plot.PNG\|thumb\|Typical UV-Vis absorption plot]]		[[File:Typical Plot.PNG\|thumb\|Typical UV-Vis absorption plot]]

	== Absorption and Transmittance ==		== Absorption and Transmittance ==

Amarin32: /* Principle */

2021-06-17T17:11:57Z

Principle

← Older revision		Revision as of 13:11, 17 June 2021
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	== Principle ==		== Principle ==
	[[File:UVVisDiagram.PNG\|thumb\|left\|Components of a typical UV-Vis spectrometer.]]		[[File:UVVisDiagram.PNG\|thumb\|left\|Components of a typical UV-Vis spectrometer.]]
	A beam of light from a visible and/or UV light source (colored red) is separated into its component wavelengths by a prism or diffraction grating <ref Name = "MSU"> UV-Visible Spectroscopy. (n.d.). https://www2.chemistry.msu.edu/faculty/reusch/virttxtjml/spectrpy/uv-vis/uvspec.htm#uv1. </ref>. Each monochromatic (single wavelength) beam in turn is split into two equal intensity beams by a half-mirrored device. One beam, the sample beam (colored magenta), passes through a small transparent container (cuvette) containing a solution of the compound being studied in a transparent solvent. The other beam, the reference (colored blue), passes through an identical cuvette containing only the solvent. The intensities of these light beams are then measured by electronic detectors and compared. The intensity of the reference beam, which should have suffered little or no light absorption, is defined as <math> I_0 </math>. The intensity of the sample beam is defined as <math> I </math>. Over a short period of time, the spectrometer automatically scans all the component wavelengths in the manner described. The ultraviolet (UV) region scanned is normally from 200 to 400 nm, and the visible portion is from 400 to 800 nm.		A beam of light from a visible and/or UV light source (colored red) is separated into its component wavelengths by a prism or diffraction grating <ref Name = "MSU"> UV-Visible Spectroscopy. (n.d.). https://www2.chemistry.msu.edu/faculty/reusch/virttxtjml/spectrpy/uv-vis/uvspec.htm#uv1. </ref>. Each monochromatic (single wavelength) beam in turn is split into two equal intensity beams by a half-mirrored device. One beam, the sample beam (colored magenta), passes through a small transparent container (cuvette) containing a solution of the compound being studied in a transparent solvent. The other beam, the reference (colored blue), passes through an identical cuvette containing only the solvent. The intensities of these light beams are then measured by electronic detectors and compared. The intensity of the reference beam, which should have suffered little or no light absorption, is defined as <math> I_0 </math>. The intensity of the sample beam is defined as <math> I </math>. Over a short period of time, the spectrometer automatically scans all the component wavelengths in the manner described. The ultraviolet (UV) region scanned is normally from 200 to 400 nm, and the visible portion is from 400 to 800 nm. PMMA, PS, or glass cuvettes are used when the primary wavelengths of interest are in the visible range and quartz cuvettes are used when those wavelengths are between 170 and 300 nm, because they are more transparent to these wavelengths.
	[[File:Typical Plot.PNG\|thumb\|Typical UV-Vis absorption plot]]		[[File:Typical Plot.PNG\|thumb\|Typical UV-Vis absorption plot]]

Amarin32: /* Principle */

2021-06-17T15:26:27Z

Principle

← Older revision		Revision as of 11:26, 17 June 2021
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	== Principle ==		== Principle ==
	[[File:UVVisDiagram.PNG\|thumb\|left\|Components of a typical UV-Vis spectrometer.]]		[[File:UVVisDiagram.PNG\|thumb\|left\|Components of a typical UV-Vis spectrometer.]]
	A beam of light from a visible and/or UV light source (colored red) is separated into its component wavelengths by a prism or diffraction grating <ref Name = "MSU"> UV-Visible Spectroscopy. (n.d.). https://www2.chemistry.msu.edu/faculty/reusch/virttxtjml/spectrpy/uv-vis/uvspec.htm#uv1. </ref>. Each monochromatic (single wavelength) beam in turn is split into two equal intensity beams by a half-mirrored device. One beam, the sample beam (colored magenta), passes through a small transparent container (cuvette) containing a solution of the compound being studied in a transparent solvent. The other beam, the reference (colored blue), passes through an identical cuvette containing only the solvent. The intensities of these light beams are then measured by electronic detectors and compared. The intensity of the reference beam, which should have suffered little or no light absorption, is defined as I0. The intensity of the sample beam is defined as I. Over a short period of time, the spectrometer automatically scans all the component wavelengths in the manner described. The ultraviolet (UV) region scanned is normally from 200 to 400 nm, and the visible portion is from 400 to 800 nm.		A beam of light from a visible and/or UV light source (colored red) is separated into its component wavelengths by a prism or diffraction grating <ref Name = "MSU"> UV-Visible Spectroscopy. (n.d.). https://www2.chemistry.msu.edu/faculty/reusch/virttxtjml/spectrpy/uv-vis/uvspec.htm#uv1. </ref>. Each monochromatic (single wavelength) beam in turn is split into two equal intensity beams by a half-mirrored device. One beam, the sample beam (colored magenta), passes through a small transparent container (cuvette) containing a solution of the compound being studied in a transparent solvent. The other beam, the reference (colored blue), passes through an identical cuvette containing only the solvent. The intensities of these light beams are then measured by electronic detectors and compared. The intensity of the reference beam, which should have suffered little or no light absorption, is defined as <math> I_0 </math>. The intensity of the sample beam is defined as <math> I </math>. Over a short period of time, the spectrometer automatically scans all the component wavelengths in the manner described. The ultraviolet (UV) region scanned is normally from 200 to 400 nm, and the visible portion is from 400 to 800 nm.
	[[File:Typical Plot.PNG\|thumb\|Typical UV-Vis absorption plot]]		[[File:Typical Plot.PNG\|thumb\|Typical UV-Vis absorption plot]]



	== Absorption and Transmittance ==		== Absorption and Transmittance ==

Amarin32 at 15:22, 17 June 2021

2021-06-17T15:22:01Z

← Older revision		Revision as of 11:22, 17 June 2021
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	== Absorption and Transmittance ==		== Absorption and Transmittance ==

	If the sample compound does not absorb light of a given wavelength, <math> I_0 = I. </math> However, if the sample compound absorbs light then <math> I < I_0 </math>, and this difference may be plotted on a graph versus wavelength. Absorption may be presented as transmittance <math> (T = I/I_0) </math> or absorbance <math> (A= log \frac{I_0}{I}) </math>. If no absorption has occurred, ''T = 1.0'' and ''A= 0''. Most spectrometers display absorbance on the vertical axis, and the commonly observed range is from 0 (100% transmittance) to 2 (1% transmittance). The wavelength of maximum absorbance is a characteristic value, designated as <math> \~~lambda_max~~ </math>.		If the sample compound does not absorb light of a given wavelength, <math> I_0 = I. </math> However, if the sample compound absorbs light then <math> I < I_0 </math>, and this difference may be plotted on a graph versus wavelength. Absorption may be presented as transmittance <math> (T = I/I_0) </math> or absorbance <math> (A= log \frac{I_0}{I}) </math>. If no absorption has occurred, ''T = 1.0'' and ''A= 0''. Most spectrometers display absorbance on the vertical axis, and the commonly observed range is from 0 (100% transmittance) to 2 (1% transmittance). The wavelength of maximum absorbance is a characteristic value, designated as <math> \lambda_{max} </math>.

	Different compounds may have very different absorption maxima and absorbances. Intensely absorbing compounds must be examined in dilute solution, so that significant light energy is received by the detector, and this requires the use of completely transparent (non-absorbing) solvents. The most commonly used solvents are water, ethanol, hexane and cyclohexane. Solvents having double or triple bonds, or heavy atoms (e.g. S, Br & I) are generally avoided. Because the absorbance of a sample will be proportional to its molar concentration in the sample cuvette, a corrected absorption value known as the molar absorptivity is used when comparing the spectra of different compounds. Molar Absorptivity <math> (\epsilon) </math> is defined by: <math> \epsilon = \frac{A}{cl} </math>, where <math> A </math> = absorbance, <math>c </math> = sample concentration in moles/liter & <math>l </math> = length of light path through the cuvette in cm (1cm for the MILL's UV-Vis) .		Different compounds may have very different absorption maxima and absorbances. Intensely absorbing compounds must be examined in dilute solution, so that significant light energy is received by the detector, and this requires the use of completely transparent (non-absorbing) solvents. The most commonly used solvents are water, ethanol, hexane and cyclohexane. Solvents having double or triple bonds, or heavy atoms (e.g. S, Br & I) are generally avoided. Because the absorbance of a sample will be proportional to its molar concentration in the sample cuvette, a corrected absorption value known as the molar absorptivity is used when comparing the spectra of different compounds. Molar Absorptivity <math> (\epsilon) </math> is defined by: <math> \epsilon = \frac{A}{cl} </math>, where <math> A </math> = absorbance, <math>c </math> = sample concentration in moles/liter & <math>l </math> = length of light path through the cuvette in cm (1cm for the MILL's UV-Vis) .

Amarin32 at 15:21, 17 June 2021

2021-06-17T15:21:42Z

← Older revision		Revision as of 11:21, 17 June 2021
Line 24:		Line 24:
	== Absorption and Transmittance ==		== Absorption and Transmittance ==

	If the sample compound does not absorb light of a given wavelength, <math> I_0 = I. </math> However, if the sample compound absorbs light then <math> I < I_0 </math>, and this difference may be plotted on a graph versus wavelength. Absorption may be presented as transmittance <math> (T = I/I_0) </math> or absorbance <math> (A= log \frac{I_0}{I}) </math>. If no absorption has occurred, ''T = 1.0'' and ''A= 0''. Most spectrometers display absorbance on the vertical axis, and the commonly observed range is from 0 (100% transmittance) to 2 (1% transmittance). The wavelength of maximum absorbance is a characteristic value, designated as \lambda_max.		If the sample compound does not absorb light of a given wavelength, <math> I_0 = I. </math> However, if the sample compound absorbs light then <math> I < I_0 </math>, and this difference may be plotted on a graph versus wavelength. Absorption may be presented as transmittance <math> (T = I/I_0) </math> or absorbance <math> (A= log \frac{I_0}{I}) </math>. If no absorption has occurred, ''T = 1.0'' and ''A= 0''. Most spectrometers display absorbance on the vertical axis, and the commonly observed range is from 0 (100% transmittance) to 2 (1% transmittance). The wavelength of maximum absorbance is a characteristic value, designated as <math> \lambda_max </math>.

	Different compounds may have very different absorption maxima and absorbances. Intensely absorbing compounds must be examined in dilute solution, so that significant light energy is received by the detector, and this requires the use of completely transparent (non-absorbing) solvents. The most commonly used solvents are water, ethanol, hexane and cyclohexane. Solvents having double or triple bonds, or heavy atoms (e.g. S, Br & I) are generally avoided. Because the absorbance of a sample will be proportional to its molar concentration in the sample cuvette, a corrected absorption value known as the molar absorptivity is used when comparing the spectra of different compounds. Molar Absorptivity <math> (\epsilon) </math> is defined by: <math> \epsilon = \frac{A}{cl} </math>, where <math> A </math> = absorbance, <math>c </math> = sample concentration in moles/liter & <math>l </math> = length of light path through the cuvette in cm (1cm for the MILL's UV-Vis) .		Different compounds may have very different absorption maxima and absorbances. Intensely absorbing compounds must be examined in dilute solution, so that significant light energy is received by the detector, and this requires the use of completely transparent (non-absorbing) solvents. The most commonly used solvents are water, ethanol, hexane and cyclohexane. Solvents having double or triple bonds, or heavy atoms (e.g. S, Br & I) are generally avoided. Because the absorbance of a sample will be proportional to its molar concentration in the sample cuvette, a corrected absorption value known as the molar absorptivity is used when comparing the spectra of different compounds. Molar Absorptivity <math> (\epsilon) </math> is defined by: <math> \epsilon = \frac{A}{cl} </math>, where <math> A </math> = absorbance, <math>c </math> = sample concentration in moles/liter & <math>l </math> = length of light path through the cuvette in cm (1cm for the MILL's UV-Vis) .

Amarin32: /* Absorption and Transmittance */

2021-06-17T15:21:20Z

Absorption and Transmittance

← Older revision		Revision as of 11:21, 17 June 2021
Line 24:		Line 24:
	== Absorption and Transmittance ==		== Absorption and Transmittance ==

	If the sample compound does not absorb light of a given wavelength, <math> I_0 = I. </math> However, if the sample compound absorbs light then <math> I < I_0 </math>, and this difference may be plotted on a graph versus wavelength~~, as shown on the right~~. Absorption may be presented as transmittance <math> (T = I/I_0) </math> or absorbance <math> (A= log \frac{I_0}{I}) </math>. If no absorption has occurred, ''T = 1.0'' and ''A= 0''. Most spectrometers display absorbance on the vertical axis, and the commonly observed range is from 0 (100% transmittance) to 2 (1% transmittance). The wavelength of maximum absorbance is a characteristic value, designated as \lambda_max.		If the sample compound does not absorb light of a given wavelength, <math> I_0 = I. </math> However, if the sample compound absorbs light then <math> I < I_0 </math>, and this difference may be plotted on a graph versus wavelength. Absorption may be presented as transmittance <math> (T = I/I_0) </math> or absorbance <math> (A= log \frac{I_0}{I}) </math>. If no absorption has occurred, ''T = 1.0'' and ''A= 0''. Most spectrometers display absorbance on the vertical axis, and the commonly observed range is from 0 (100% transmittance) to 2 (1% transmittance). The wavelength of maximum absorbance is a characteristic value, designated as \lambda_max.

	Different compounds may have very different absorption maxima and absorbances. Intensely absorbing compounds must be examined in dilute solution, so that significant light energy is received by the detector, and this requires the use of completely transparent (non-absorbing) solvents. The most commonly used solvents are water, ethanol, hexane and cyclohexane. Solvents having double or triple bonds, or heavy atoms (e.g. S, Br & I) are generally avoided. Because the absorbance of a sample will be proportional to its molar concentration in the sample cuvette, a corrected absorption value known as the molar absorptivity is used when comparing the spectra of different compounds. Molar Absorptivity <math> (\epsilon) </math> is defined by: <math> \epsilon = \frac{A}{cl} </math>, where <math> A </math> = absorbance, <math>c </math> = sample concentration in moles/liter & <math>l </math> = length of light path through the cuvette in cm (1cm for the MILL's UV-Vis) .		Different compounds may have very different absorption maxima and absorbances. Intensely absorbing compounds must be examined in dilute solution, so that significant light energy is received by the detector, and this requires the use of completely transparent (non-absorbing) solvents. The most commonly used solvents are water, ethanol, hexane and cyclohexane. Solvents having double or triple bonds, or heavy atoms (e.g. S, Br & I) are generally avoided. Because the absorbance of a sample will be proportional to its molar concentration in the sample cuvette, a corrected absorption value known as the molar absorptivity is used when comparing the spectra of different compounds. Molar Absorptivity <math> (\epsilon) </math> is defined by: <math> \epsilon = \frac{A}{cl} </math>, where <math> A </math> = absorbance, <math>c </math> = sample concentration in moles/liter & <math>l </math> = length of light path through the cuvette in cm (1cm for the MILL's UV-Vis) .

Amarin32: /* Absorption and Transmittance */

2021-06-17T15:20:32Z

Absorption and Transmittance

← Older revision		Revision as of 11:20, 17 June 2021
Line 24:		Line 24:
	== Absorption and Transmittance ==		== Absorption and Transmittance ==

	If the sample compound does not absorb light of a given wavelength, <math> I_0 = I. </math> However, if the sample compound absorbs light then <math> I <~~/math> is less than <math>~~ I_0 </math>, and this difference may be plotted on a graph versus wavelength, as shown on the right. Absorption may be presented as transmittance <math> (T = I/I_0) </math> or absorbance <math> (A= log \frac{I_0}{I}) </math>. If no absorption has occurred, ''T = 1.0'' and ''A= 0''. Most spectrometers display absorbance on the vertical axis, and the commonly observed range is from 0 (100% transmittance) to 2 (1% transmittance). The wavelength of maximum absorbance is a characteristic value, designated as \lambda_max.		If the sample compound does not absorb light of a given wavelength, <math> I_0 = I. </math> However, if the sample compound absorbs light then <math> I < I_0 </math>, and this difference may be plotted on a graph versus wavelength, as shown on the right. Absorption may be presented as transmittance <math> (T = I/I_0) </math> or absorbance <math> (A= log \frac{I_0}{I}) </math>. If no absorption has occurred, ''T = 1.0'' and ''A= 0''. Most spectrometers display absorbance on the vertical axis, and the commonly observed range is from 0 (100% transmittance) to 2 (1% transmittance). The wavelength of maximum absorbance is a characteristic value, designated as \lambda_max.

	Different compounds may have very different absorption maxima and absorbances. Intensely absorbing compounds must be examined in dilute solution, so that significant light energy is received by the detector, and this requires the use of completely transparent (non-absorbing) solvents. The most commonly used solvents are water, ethanol, hexane and cyclohexane. Solvents having double or triple bonds, or heavy atoms (e.g. S, Br & I) are generally avoided. Because the absorbance of a sample will be proportional to its molar concentration in the sample cuvette, a corrected absorption value known as the molar absorptivity is used when comparing the spectra of different compounds. Molar Absorptivity <math> (\epsilon) </math> is defined by: <math> \epsilon = \frac{A}{cl} </math>, where <math> A </math> = absorbance, <math>c </math> = sample concentration in moles/liter & <math>l </math> = length of light path through the cuvette in cm (1cm for the MILL's UV-Vis) .		Different compounds may have very different absorption maxima and absorbances. Intensely absorbing compounds must be examined in dilute solution, so that significant light energy is received by the detector, and this requires the use of completely transparent (non-absorbing) solvents. The most commonly used solvents are water, ethanol, hexane and cyclohexane. Solvents having double or triple bonds, or heavy atoms (e.g. S, Br & I) are generally avoided. Because the absorbance of a sample will be proportional to its molar concentration in the sample cuvette, a corrected absorption value known as the molar absorptivity is used when comparing the spectra of different compounds. Molar Absorptivity <math> (\epsilon) </math> is defined by: <math> \epsilon = \frac{A}{cl} </math>, where <math> A </math> = absorbance, <math>c </math> = sample concentration in moles/liter & <math>l </math> = length of light path through the cuvette in cm (1cm for the MILL's UV-Vis) .