Skip to main content

Questions tagged [spectrophotometry]

A method to measure how much a chemical substance absorbs light by measuring the intensity of light as a beam of light passes through sample solution.

Filter by
Sorted by
Tagged with
0 votes
1 answer
40 views

Do Electron-Withdrawing-Groups give an hypsochromic shift or a bathochromic one? and why?

I'm not familiar with this topic,but i know that bathochromic shifts occur when the energy gap between energy levels of the substituted molecule, are lower than the unsubstituted one;viceversa ...
BugsBunny's user avatar
2 votes
2 answers
100 views

Why aren't there different peaks for different IE in PhotoElectron Spectroscopy (PES)?

The way I understand PES is that you shine a light on a bunch of atoms and measure the kinetic energy of photons to determine ionisation energies (or energies of electrons... is that different?). I ...
Maddy's user avatar
  • 41
2 votes
0 answers
22 views

Is there a cheaper alternative to Liquid Color Standards?

I'm trying to create a sensor that measures the fluid color within a PVC tube that exits from a patient's surgical wound. I have a handheld spectrophotometer and a TCS3200 sensor, and I'm trying to ...
Bilal Bahadır Akbulut's user avatar
3 votes
0 answers
29 views

Can multispectral imaging be used for identification of materials, substituting for hyperspectral imaging?

Nowadays a lot of research and applications are using Hyperspectral Imaging for identification and segregation of plastics by material. But the cost of a HSI system is quite high. Could a ...
Aether's user avatar
  • 147
6 votes
1 answer
263 views

Lifetime components in phosphorescence decay

I'm studying the phosphorescence decay of diacetyl in acetonitrile (it has a high quantum yield of intersystem crossing). The fluorimeter than I'm employing has microsecond resolution and, since the ...
user avatar
1 vote
0 answers
28 views

Single or multiple calibration curves for interpreting datasets?

I ran three batches of samples through the HPLC. Each batch run contained standard solutions and a set of experimental samples. The standard solutions included in each batch run were exactly the same, ...
Dana Tran's user avatar
3 votes
0 answers
42 views

Reaction of BTNA, DMSO, and phosphate?

I prepared a solution of n-benzoyl L-tyrosine p-nitroanilide (BTNA) in dimethyl sulfoxide for use in an enzymatic assay. However, mixing it with a solution of phosphate buffer produced a color change ...
user73910's user avatar
  • 1,264
3 votes
2 answers
2k views

Why is the entire 3p sublevel peak shifted to the right on a PES of Sulfur vs Phosphorus?

Edit: Please see answer. I am going to leave the question here in case someone else has a similar misunderstanding. I am currently a student in AP Chemistry. I was working on an assignment with these ...
jb0's user avatar
  • 336
0 votes
1 answer
103 views

How can I derive the ratio of concentrations?

I need to derive the equation $$ \frac{[\ce{In^-}]}{[\ce{HIn}]} = \frac{A_\mathrm{int} - A_\mathrm{lo}}{A_\mathrm{hi} - A_\mathrm{int}} \tag1\label{eq1} $$ from the material balance equation that ...
user130306's user avatar
6 votes
2 answers
1k views

How does molecular structure contribute in the property of fluorescence?

Fluorescence is the property which is exhibited when electrons emit wavelength of light lower than the one they absorbed so does that mean we can make every molecule to become fluorescent? I wanted to ...
25 Simran Tiwari's user avatar
2 votes
0 answers
48 views

How would I find what specific wavelength I need to measure for a specific chemical in spectrophotometry (calcium perchlorate)?

I am currently doing a research project, and for it, I would like to use a photospectrometer to find the concentration of Calcium Perchlorate in my sample solutions. My current method of data ...
Joseph Field's user avatar
5 votes
1 answer
488 views

The reason for selection of wavelengths in the spectrophotometry of Quinoline Yellow SS

The absorption spectrum for Quinoline Yellow SS has peaks at 224 nm and 414 nm, and a trough at 337 nm. This experiment (see page 31), selects 224, 337 and 414 nm to be used in the spectrophotometric ...
StrugglingChemistryStudent's user avatar
-1 votes
1 answer
346 views

Help determining Absorption Coefficient & Concentration from Uv-Vis reading [closed]

hope you're doing well. I'm having some trouble determining the absorption coefficient and concentration values of a protein from its UV absorption results. The experiment in question involves an ion ...
windhypernovaowlbeat's user avatar
1 vote
1 answer
168 views

How to identify an error in cut off filter (optical) usage when running spectrophotometry?

In spectrophotometry, often a cut off optical filter is used. With reference to a long-pass filter, which rejects any wavelengths outside a predetermined interval: low transmission in short ...
bonCodigo's user avatar
  • 1,944
2 votes
0 answers
117 views

How to identify the wavelength to compare absorption at in spectrophotometry?

I boiled spinach solution (ground spinach leaves homogenized in 90% methanol) in solutions of varying pH, and am using spectrophotometry to determine chlorophyll content. My results show changes in ...
Chem Student's user avatar
4 votes
1 answer
2k views

How to determine chlorophyll content from spectrophotometry data (absorbance vs wavelength)?

I boiled spinach solution (spinach leaves and 90% methanol) in solutions of varying $\mathrm{p}H$. I used a spectrophotometer to obtain wavelength ($\lambda$) vs absorption, and want to investigate ...
Chem Student's user avatar
3 votes
0 answers
58 views

Are there any ways of modifying molecules to increase their probability of two photon absorption?

While checking two photon microscopy, the use of high flux femtosecond laser is required for the dual absorption of photons, due to the low probability of these two photons being absorbed. Is there ...
C-Consciousness's user avatar
3 votes
1 answer
2k views

UV-spectra of benzene

I measured the UV-absorption-spectrum of benzene vapor as well as solved in methanol and cyclohexane. The absorption of the vapor was much stronger than in solution. I also noticed that the peaks get ...
Christian's user avatar
  • 211
6 votes
1 answer
423 views

How does a spectrophotometer measure absorbance based on the intensity of detected light?

We know that $\displaystyle A = -\log\frac{I_t}{I_0}$, where $I_0$ is the intensity of light without a sample absorbing, and $I_t$ with the sample. For determining the absorption $A$, we need both $...
Gougni Adam's user avatar
1 vote
0 answers
43 views

How can I save an EEM file on a Fluoromax4?

I'm trying to run excitation-emission matrices on some water samples, but I'm running into some software issues that the manuals aren't helpful for. In order to use R studio to extract my data, I need ...
dogman's user avatar
  • 61
2 votes
1 answer
2k views

Slope ≠ 1 in Henderson-Hasselbalch graph for determination of pKa

The $\mathrm{p}K_\mathrm{a}$ of indicators can be determined via plotting a graph of $\log \left(\frac{\ce{In-}}{\ce{HIn}}\right)$ vs $\mathrm{pH}$ with the help of a spectrophotometer, from the ...
Owen 's user avatar
  • 21
0 votes
1 answer
646 views

Which of the following can be a source of error in Spectrophotometry? Mark the wrong answer

a) Differences in solvent b) Acid base equilibrium (differences of pH) c) Parasitic or stray radiation d) Monochromatic radiation I have some doubts about pH in spectrophotometry. I'm not sure if it ...
Luzbe26's user avatar
  • 27
2 votes
1 answer
3k views

The negative absorbance values in the baseline measurement

In the spectrophotometric analysis(uv-vis-NIR) of ITO Nanoparticles in tetrachloroethane using a double beam instrument baseline was measured with 2 identical cuvette with solvent only. This gives me ...
A K Mohan's user avatar
2 votes
1 answer
303 views

Heat of reaction for the decomposition of AgCl means?

Certain sunglasses have small crystals of $\ce{AgCl}$ incorporated into the lenses, on exposure to light of appropriate wavelength produces a grey colour to reduce the glare following the reaction: $$\...
Srijan's user avatar
  • 412
4 votes
0 answers
63 views

How to determine the source of sub-nm periodic error in NIR spectra

I've run into an issue collecting measurements on deionized water in the $1050-\pu{1200 nm}$ range. To determine the sensitivity of my spectrophotometer in this range, I've acquired measurements on ...
jfmhardigree's user avatar
0 votes
0 answers
47 views

Acorrect range of concentrations for the reactants in the equilibrium reaction

What would be a correct range of concentrations for the reactants in the equilibrium reaction, $\ce{Fe^3+(aq) + SCN-(aq) <=> FeSCN^2+}$? For a Chemistry project I am measuring the effects of ...
acertainfruit's user avatar
1 vote
1 answer
221 views

Is there an actual distinction between through-space charge transfer and excimer emission?

Variety of books and literature reviews consider excimer (or exciplex) emission something distinct from through-space charge transfer. Is this actually the case? This question arises, because the more ...
A small potato's user avatar
2 votes
1 answer
586 views

Connecting a computer to Genesys 10S Spectrophotometer

Has anybody ever connected a computer to a Thermo Scientific Genesys 10S Spectrophotometer without their (costly!) software? I'd like to pull absorbance data off of it to perform analyses. There are ...
E. Hunter's user avatar
  • 159
7 votes
2 answers
2k views

Why does ethylamine have two infra-red spectra? Are both correct?

The one I have in my textbook is this: Shouldn't the first trough at $3500$ to around $3000$ mean that it's an $\ce{O—H}$ group with a $\ce{C—H}$? And then the other trough at $1700$ be a $\ce{C=O}$? ...
Ollie's user avatar
  • 107
1 vote
2 answers
1k views

A Spectrophotometric technique to evaluate Vitamin C concentration in Citrus Fruit

Is there a visible spectrophotometric technique that can gage the concentration of vitamin C in solution? I plan on boiling different citrus fruit in water, and taking aliquotes of the boiled solution ...
Mas's user avatar
  • 467
2 votes
0 answers
1k views

Data analysis in TCSPC for fluorescene decay (reconvolution with measured IRF)

I am trying to understand the data analysis of fluorescence decay counts measured by TCSPC technique, particularly with reconvolution with measured IRF. I am able to get the fitted counts (given by ...
Crops's user avatar
  • 139
1 vote
0 answers
101 views

Common chemcials that produce phosphorescence

Are there any common lab chemicals or household stuff that produce phosphorescence? I am aware of ZnS, CaS, Fluorescein, Erythrosin B, Vanillin Benzaldehyde, Vitamin B2, Tryptophan etc. I just need ...
Crops's user avatar
  • 139
1 vote
0 answers
43 views

Measuring Testosterone Levels Using ELISA [closed]

I am new to this topic so please be patient. I am looking to understand ELISA better and how one may attempt to not only detect but measure the total calculated level present in a sample. I would ...
Invic18's user avatar
  • 19
4 votes
3 answers
929 views

Chemicals that form coloured complexes with Pb(II) cations

I’m currently conducting a photo-spectrometric analysis of lead concentration in water, and was looking into using Eriochrome Black T (EBT) as an indicator for $\ce{Pb^2+}$ (due to the complex forming ...
Mas's user avatar
  • 467
1 vote
0 answers
183 views

Spectrophotometry: shifting absorbance curves vertically so isosbestic points match

We're measuring reaction kinetic parameters of a hydration reaction (Co complex) by measuring the absorption spectrum a different time intervals, and calculating the ratio of product to reactant by ...
ibsrewed's user avatar
7 votes
1 answer
569 views

Haemoglobin literature spectra does not match

I am studying haemoglobin absorption spectra in its oxygenated and deoxygenated state and I compiled values from different sources including: A PhD thesis by van Assendelft [1], using extinction ...
mranvick's user avatar
  • 536
7 votes
1 answer
3k views

Beer's law: UV-Vis absorbance values exceeding 2

In classical analytical chemistry, absorbance values in Beer's law can theoretically range from 0 to infinity. As general rule of thumb neither high, nor very low absorbance are used for ...
ACR's user avatar
  • 41.2k
1 vote
0 answers
289 views

Calibration curves and dilution factors

I am currently taking a course where we are exploring nitrate concentrations in water samples. We are using a UV-Vis Spectrophotometer and have created a calibration curve in the first part of the ...
Sanuks's user avatar
  • 19
0 votes
0 answers
677 views

Preparation of standard Fe from FeSO4 • 7H2O

We were assigned to prepare a standard Fe for spectrophotometry determination of Fe. What we did is basically obtain a mass of FeSO4•7H2O, add a small a mount of distilled water before adding 18M of ...
Mochi's user avatar
  • 11
2 votes
3 answers
709 views

If Beer's Law appears to apply to a high concentration (>0.01M) of a solute, is it valid to use for concentration calculation?

Internet consensus seems to define "high concentration" for Beer's Law as >0.01M. If one has a solution at higher concentrations than that, but the absorbance vs. concentration is still linear, is it ...
Hali C.'s user avatar
  • 39
0 votes
0 answers
152 views

Absorption of UV Light and what color would be seen?

I am mathematically experimenting with different wavelengths of light that a fictional material would absorb. I thought of a material that absorbs a wavelength of $\pu{193 nm}$. This wavelength ...
Altraxian's user avatar
  • 111
12 votes
1 answer
2k views

Looking for a dye which emits around 680 nm

For a specific experiment, I'm looking for a dye which would emit around 680 nm. Preferably one I could buy easily commercially. Are there any databases which might give the emission spectra of ...
Tomi's user avatar
  • 590
0 votes
1 answer
59 views

Soluble compounds to absorb radio-frequency electromagnetic radiation

Are there any soluble compounds capable of absorbing radio-frequency or long microwave radio-frequency electromagnetic radiation? I have noted that metals are often used to absorb these signals, but ...
Hypnos Stratagem's user avatar
5 votes
1 answer
58 views

Measure low DOM absorbance values in a microplate reader. Is there a suitable deep well microplate with flat bottoms available?

I would like to use a microplate reader to measure the absorbance of dissolved organic matter (DOM), but the measured values are close to the lower detection limit. To overcome this, I thought of deep ...
M.Pucher's user avatar
1 vote
1 answer
466 views

Molar absorption coefficient for potassium hydrogen phthalate

I would like to draw a comparison of the sensitivity between several spectrometers. Therefor I measure the absorption of a serial dilution of potassium hydrogen phthalate (KHP). The idea is to compare ...
Helen's user avatar
  • 11
1 vote
0 answers
227 views

Determination of pKa and molar absorptivity coefficient using spectrophotometry [closed]

An indicator BPB (Brophenol Blue) is used and dissolved in solutions of various known $\mathrm{pH}$. Then, the absorbance of each solution at 590 nm was measured and the question asks for molar ...
user77146's user avatar
1 vote
2 answers
405 views

Determining Kc for the equilibrium involving iron thiocyanate using spectrophotometric data

$$\ce{Fe^3+(aq) + SCN-(aq) <=> [Fe(SCN)]^2+(aq)}$$ $\pu{12.0 mL}$ of $\pu{0.00110 mol L-1}$ $\ce{Fe^3+}$ was added to $\pu{6.00 mL}$ of $\pu{0.00140 mol L-1}$ $\ce{SCN-}$. The absorbance of the ...
Codeblockz's user avatar
3 votes
2 answers
17k views

Does a calibration curve of absorbance vs concentration need to pass exactly through the origin?

If you are making a calibration curve for $\ce{CuSO4}$ where you plot absorbance against concentration and the curve deviates slightly from the origin, does it make the calibration curve useless?
Prosti 's user avatar
-1 votes
1 answer
706 views

What is the molar extinction coefficient of azorubine (carmoisine, E 122)

I'd be grateful for the molar extinction coefficient ε of azorubine at the absorption maximum (about 520 nm), with an authoritative reference.
Martin's user avatar
  • 731
1 vote
0 answers
456 views

Choosing the right wavelength for calibration curve and for analysis of actual results

Introduction: I am currently conducting a series of experiments in which I am studying the transport of polystyrene nanoparticles (PNPs) through sand and soil. This is done in sand/soil columns, into ...
Don_S's user avatar
  • 1,410