Questions tagged [chromatography]
collective term for a set of laboratory techniques for the separation of mixtures
206
questions
-2
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18 views
Is it possible to extract taurine from energy drink by liquid liquid extraction, which solvent should I use?
I need to know how to extract taurine from energy drinks, because I'll be needing that for tlc analysis.
8
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3answers
468 views
What would a (gas) chromatogram look like if two compounds have the same retention times? [closed]
In gas chromatography, the number of peaks represents the number of compounds in an unknown sample, as retention times for each component differ.
But what would happen if two components have the same ...
2
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1answer
26 views
How do I interpret the results of this chromatogram and does it tell me about the compounds' polarities?
I am reading this journal article which discusses using high-performance liquid chromatography (HPLC) to separate dyes from wine. Here are the relevant facts about the experimental setup:
Two mobile ...
4
votes
1answer
130 views
ELSD detection principle
While documenting myself on the detectors used in HPLC, I came across one that I did not know: ELSD.
I understood that the sample with the mobile phase was nebulized at the column outlet but I do not ...
1
vote
1answer
45 views
What are the benefits of using zero capillary voltage for discarding fractions in LC–ESI–MS/MS?
In the second episode of The Association for
Mass Spectrometry & Advances in the Clinical Lab (MSACL) podcast, namely Getting going with mass spectrometry : Josh learns chromatography (aired 2021-...
2
votes
1answer
35 views
How can over grinding lead to reduced API extraction in HPLC analysis?
I am looking for some advice regarding particle size distribution (PSD) & how this can be affected by grinding a tablet.
During an assay by HPLC, the method requires grinding of a tablet before ...
-1
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0answers
21 views
TLC: Why does distance traveled and seperation change in MeOH:DCM and MeOH:DCM:AcOH?
Question about tlc: With the stationary phase being Silica, which is polar. And we have MeOH:DCM and MEOH:DCM:AcOH as the mobile phase 1 and mobile phase 2. If we have the compounds being: Benzoic ...
2
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0answers
11 views
Right conductivity of protein sample for Protein A purification of human IgG?
A sample from a cell culture has some IgG and this is to be purified using protein A chromatography. Based on the chromatography handbook from GE-Healthcare/Cytiva, the protein sample should have &...
4
votes
2answers
245 views
HPLC: Peak height calculation
I am trying to implement a small python script to detect peaks and calculate the corresponding area. The y-values are in mAU and x-values in minutes but there are some unit conversions in most HPLC ...
-1
votes
1answer
32 views
Chromatography- why tM is separated from other peaks? [closed]
tM in Chromatography is the time of exist mobile phase. But, the mobile phase exist together with all the compunds that tasted in the process. So, why in the graph of signal to time we can see a peak ...
1
vote
1answer
65 views
What is “silanol activity”?
In a previous post about how pyridine failed to move much from the baseline of a TLC, I was told to look into "silanol activity". However, I was unable to find a textbook-style description. ...
0
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0answers
16 views
Salting out worsens extraction efficiency
I'm currently writing a thesis about using dispersive liquid-liquid microextraction DLLME for extracting nitramines from aqueous solutions. We've been using octan-1-ol as the extractant and HPLC for ...
1
vote
1answer
53 views
Does using same calibration curve for chemical analysis introduce correlation in sample error/uncertainty values?
I am using a hypothetical case to explain my question
Let us consider a chemical analysis method A (using a certain instrument), which is used to quantify the value of a particular species b. ...
0
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1answer
39 views
Compound Polarity Lookup
I know from the literature that the following compounds have decreasing polarity: Rosmarinic Acid -> TMF -> Sinensetin and I guess comparing compounds of ...
0
votes
1answer
109 views
Determining the mass of a substance using calibration curve produced by HPLC
I hope everyone is doing well and safe! Yesterday, I was fortunate enough to be taught about how to read a chromatography calibration curve through this stackexchange! Special thanks to those who ...
2
votes
4answers
586 views
How to read a chromatography calibration curve?
I am a high school student who has been studying a bit of chromatography. I came across calibration curve during class and I trying to figure how to read it and use it? I have no clue how to read off ...
0
votes
1answer
110 views
Modifying a TLC mobile phase in order to increase the RF values [closed]
You are running a TLC using 50% ethyl acetate in hexane and find the resulting $R_f$ values are too low. How would you modify the TLC mobile phase in order to increase the $R_f$ values?
Would the ...
1
vote
1answer
186 views
Calculating the concentration of product in a solution based on the peak area of HPLC [closed]
Please help me resolving the following:
A sample solution, $\pu{0.24mg/mL}$ Compound A, is exposed to heat to form Compound B. From HPLC data report I have peak area for Compound A and Compound B. ...
2
votes
2answers
62 views
The best chromatographic technique to analyse a solution of benzene, toluene, and ethylbenzene in n-hexane
What is the best chromatographic technique to analyse a solution containing benzene, toluene, and ethylbenzene in n-hexane?
Is gas chromatography (GC) the best way to analyse this solution? Or is ...
3
votes
1answer
139 views
Types of chromatogram shapes [closed]
I'm trying to generate a testing set of different chromatograms to check peak detection (whether peak boundaries are detected correctly) and smoothing algorithms. Currently I'm figuring out which ...
1
vote
0answers
35 views
Column Dispersive Mass Balance analytical / numerical solution
Is there any analytical solution for the most common expression of column mass balance:
$\dfrac{\partial C}{\partial t} + \left(\dfrac{1+\varepsilon}{\varepsilon}\right)\dfrac{\partial q} {\partial t} ...
4
votes
1answer
169 views
Stronger ESI signal for deuterated substances
I observe a constant phenomenon in my ESI measurements, which indicates that deuterated substances give a stronger signal than the same substance in non-deuterated form. Unfortunately I can't make any ...
0
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1answer
127 views
Is there any database, or reference, for retardation factors (Rf)? [closed]
I'll like to compare the Rf of myrcene, obtained in Thin Layer Chromathography, for different species. Toluene:Ethyl Acetate (97:3) would be fine, but is not a necessity.
1
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1answer
71 views
Theoretical plates in Plate theory of chromatography
In "Chromatography theory" by Scott and Cazes,
The plate volume is given as ($v_m+Kv_s$) where $v_m$ and $v_s$ are the volume of stationary and mobile phase in the column and $K$ is the ...
2
votes
1answer
51 views
How do I analyze 17 different gases from a sample?
I am designing a test setup in which I heat a battery until it releases its gases, and I need to analyze the composition of the fumes. Below is the list of gases that are believed to be present in the ...
-1
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1answer
97 views
Elution and void volumes in a gel chromatography experiment
I was using gel-filtration for separation Hb from xylene cyanol FF with Blue Dextran to determine the void volume. Sephadex G-25 is stationary phase, and mobile phase was buffer $(\pu{0.020 mol dm-3}$ ...
1
vote
0answers
73 views
Disadvantages of SIM vs TIC in GC-MS [closed]
In GC-MS what are the relative advantages/disadvantages of using Selected-Ion Monitoring (SIM) vs using Total Ion Chromatograms (TIC)?
I know that SIM offers a better S/N ratio, however if the S/N is ...
4
votes
1answer
121 views
Purification of primary amines using Schiff base immobilization
I want to purify all primary amines containing compounds in a complex mixture (cell-extracted metabolites). I'm unaware of any published methods to do so. So I am thinking of making my own using a ...
3
votes
1answer
215 views
How do I import CSVs to OpenChrom?
My end objective is to compare GC outputs of samples in two groups using PCA. I have bene given the data in Excel format but have saved to CSV.
Whilst I can locate CSV files through OpenChrom, they ...
0
votes
1answer
82 views
What order would these compounds elute in a 3:1 hexanes:ethyl acetate TLC run? [closed]
I would figure the order would be (in order of smallest Rf to largest) W, Z, Y, X. Is the carboxylic acid more polar than the acetic anhydride?
2
votes
1answer
95 views
Why can zwitterions be difficult detect by HPLC-MS?
I understand that to separate molecules by HPLC (or SFC) you commonly adjust the pH of the mobile phase to get preferable charges (i.e. negative charges) on the molecules - so that they interact with ...
3
votes
1answer
90 views
Is there a list of must-have columns for LC-MS/MS used in biochemistry/clinical lab setting?
Considering a wide variety of chromatographic columns used for (U)HPLC based on
phase type (normal or reverse);
column dimensions (geometry, length, inner diameter);
particle material $(\ce{SiO2},$ $\...
-1
votes
2answers
400 views
What is the principle of RP-HPLC? [duplicate]
Is the following statement the correct way to explain principle of RP-HPLC?
It works on the principle of hydrophobic interactions hence the more nonpolar the material is, the longer it will be ...
1
vote
2answers
182 views
Can separated and purified substances be obtained from a chromatogram?
I am studying chemistry, and I am learning about chromatography.
But I am confused about how chromatography is used to ‘separate and purify’ substances.
I have learnt about chromatography paper, ...
2
votes
1answer
208 views
Conditions for choosing quantifying and qualifying ion in LC-MS/MS
In my PhD-work, we are trying to develop LC-MS/MS methods for targeted analysis. Usually, I determine my quantifying ion/fragment based on a few different criteria:
If there is a 13C internal ...
5
votes
1answer
104 views
How to recover C18 column after prolonged exposure to phosphate buffer?
A colleague of mine who occasionally does HPLC in a biochemistry lab discovered that a C18 column was not properly flushed after the previous experiment.
It appears that the column was stored for ...
2
votes
1answer
69 views
Can we use HPLC to purify an organic reaction product?
I know HPLC is a form of column chromatography that uses high pressure to pump a sample mixture/eluent through a column. However, I'm not sure if this technique is being used to purify and isolate ...
2
votes
1answer
109 views
Software platforms with integration of multi vendor mass spectrometer device data?
I know about ACD/Spectrus Processor which is a software platform to integrate analytical chemistry data from multiple mass spectrometer device vendors (e.g. Agilent Technologies, Bruker, Waters) to ...
2
votes
1answer
68 views
Why can DAP be used to elute a protein in affinity chromatography?
A little background: as part of my bioinformatics degree I have to take Protein Chemistry course, but I miss chemistry basics (have CS background), so that's why I'm asking the following question.
We ...
2
votes
2answers
126 views
Why n-alkanes can be found in organic solvent extract of rubber?
Sorry for the confusing title, I didn't know how to describe this better. So, if we douse rubber, say, a bicycle tire or a certain type of rubber glove, with organic solvent (n-heptane), we can find n-...
3
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2answers
577 views
What dictates cathode vs anode nomenclature use?
what was the justification for the use the cathode and anode terminology in IEF?
There is no redox taking place in IEF, just proteins interacting with an electric field
0
votes
1answer
90 views
When to use chromatographic separation vs vacuum-assisted rectification distillation?
I'm trying to understand a bit more about industrial scale separation processes. One particular element I'm interested in is the question as to when chromatography (HPLC or Simulated Moving Bed) may ...
0
votes
1answer
70 views
Why mustn't the sample be dipped in the mobile phase in paper chromatography?
As the title says it, I am curious about why the sample (ie, an extract of plant's chlorphyl transferred onto paper) must not be dipped into the mobile phase (ie, the solvent which goes up the paper)?
...
6
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3answers
661 views
In High Performance Liquid Chromatography, why are ratios of solvents used?
How do they allow for better separation? For example, why isn't 100% hexane used?
1
vote
1answer
74 views
Organic solvent for cleaning autosampler syringe
I work in a laboratory where gas chromatography is used extensively. We handle phthalates. What are the possible wash solvent for autosampler syringe? I've been using acetone.
3
votes
1answer
158 views
Choosing LC-MS modifier - why only acids?
During method selection our chromatographists have options like NH4, TFA, Formic Acid. What's the point of choosing only between acid? Why not use the strongest that guarantees ionization? The sample ...
1
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2answers
64 views
Can I normalize my data in order to compare it?
I have three chromatograms of the same eluted protein but at different concentrations, since it got diluted during purification process) and hence peak maximums at very different absorbances.
The ...
2
votes
1answer
458 views
How to pool fractions after chromatography?
I used chromatography to purify my protein and now I have fractions with different concentrations ranging from 1-16 mg/ml. Should I pool all these fractions or just the ones with high concentration (...
1
vote
0answers
20 views
I am having difficulties with analysing steroids in GC/MS [closed]
Is there anyone here that has already analysed estrone and 17beta-estradiol on GC/MS (HP5-MS column and MSTFA as derivatizing agent)?
Is it necessary to make a mixture of other reagents with MSTFA or ...
3
votes
1answer
42 views
How appropriate/adaptable is HPLC for in situ sample analysis on Titan?
I have a limited background in chemistry (nothing beyond general Chem 2), so I am asking for help with a group project. We have two chemists on our team, but communication is limited at the time and I ...
