Question about chromatography?
955885
In column chromatography, the elution of analytes is a function of both the stationary and mobile phases (among others things, like temperature).\n\nIf the analyte does not elute, then either the stationary or mobile phase was not chosen correctly.  K' might be very large without being infinite.  The compound may be moving through the column, but too slowly to elute entirely from the column.\n\nFor example:  if the stationary phase is silica gel and the compound does not elute with alcohol or water, then a basic or acidic aqueous solution might be needed to elute the compound.
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Links at\n\nhttp://www.itt.edu/staff/boyter/links/index.html#CHEMISTRY_CHROMATOGRAPHY
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Green pigments travel faster because the molecules are smaller than those of other colours. When you use chromatography paper, you are dissolving the dried pigments of colour -- as the water travels up the paper, it pulls the colour pigments with it. The smaller the pigments, the faster they travel.
1166070
For information on how to do the chromatography test choose from the following lists:\nhttp://search.yahoo.com/search?p=chromatography+test&prssweb=Search&ei=UTF-8&fr=ytff1-&x=wrt\nhttp://www.google.com/search?num=100&hl=en&lr=lang_en&q=chromatography+test&btnG=Search
721022
Well, I do not know that syllabus.  You will need to sift useful answers.\n\nI would use:\n\ndifferent solubility in solvents\ndifferent boiling points\nrecrystallise one out of a mixed solution\n\nYou might be at too junior a level to know about ion exchange resins, and other chromatography techniques.
888975
There is no such thing as "mass chromatography"\n\nThere is 2 other options that you can be refering to  LC/GC/MS systems that separate the elution and atomize the solvent as it comes off the column, and send it to the quadrapole in the MS for detection of mass.\n\nThere is also GPC (Gel Permeation) Chromatography which is perhaps more what you might be looking for.   This type of system is similar to HPLC, but is lower pressure (100 bar) and instead of separation by Polarity, this particular column will separate by molecular mass; with the larger molecules having the shortest elution time, and the smaller molecules having the longer elution time.  This works best if used with a Refractive index detector.
116691
Chromatographyis a way to seperate out different parts of a mixture.  The idea is that you pass a fluid (either a gas or a liquid) down a long path, and the different molecules will move at different rates.  THat's the long and short of it.  So the molecules that move fastest get to the end first, and the slowest come out last.  You seperate things by making them race, and similar chemicals will take a similar amount of time to finish the race.\n\nI'm assuming that you're getting confused by things like "solid phase" and "mobile phase" and "bind affinity" and such.  The idea though is that you set up different types of obstacles depending on which things you want to win the race.  Sometimes this is dine by using something with a lot of positive charges, so that things with negative charges will get stuck and the things that are neutral or positively charged will win the race. Sometimes you sort things by size, by using a gel as an obstable with a bunch of little pores in it: little guys get lost inside and the fat guy wins the race.  With gases, you can just make the race really, really, really long, and the lightest parts will move the quickest while the hevy boys lag behind (this is a way that uranium is enriched for nuclear reactors and bombs).
710499
Validation is a process that consists of at least four distinct steps:\n\n1.   software validation, \n2.   hardware (instrumentation) validation/qualification, \n3.   method validation \n4.   system suitability \n\nThe process begins with validated software and a qualified system. Then a validated method using the qualified system can be developed. Finally it is all wrapped together, in a total validation, using system suitability. Each step is critical to the overall success of the process\n\nMETHOD VALIDATION should include: \nLinearity: the range of linearity is checked by injections of 5-6 concentrations of the reference standards (in triplicates) below and above the expected concentration of the \nsamples (20%-120%). The slope and intercept are determined. r >= 0.999, and the range of linearity (in conc. terms) is established. \n\nAccuracy is measured as the (amount measured)/(amount claimed) in the following procedures: \nIn drug formulations: a standard is added to the placebo (80%, 100%, 120%), and the recovery is measured \nRecovery from sample preparation procedures (such as dilution, extraction or filtration) should be established. \n\nSolution stability of the samples (A fresh sample is compared to one which was left in solution for the entire duration of the test procedure). \n\n Intermediate precision or ruggedness: 5 measurements of the first step of accuracy under two different occasions (two columns, or two operators). \n\nLimit of detection (LOD) and limit of quantification (LOQ): \nThe intercept from the linearity test (in section 5.a) can be used for LOQ measurements (intercept x 5 or 10). \nAnalysis of repeatability at the quantification limit, using both sample and reference standard. Concentrations that yield 10-15% RSD will be acceptable as LOQ concentrations. \n\n Robustness of the chromatographic method: variables in this test can be the following: column batch #, solvent strength in the mobile phase, temperature, flow rate, pH of the mobile phase, ionic strength in the mobile phase, sample diluent, \ninjection volume, wavelength of detection. The parameter measured: response, retention time, selectivity and/or resolution. \n\n=)
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GC is gas chromatography, an analytical instrument used to isolate/identify organic compounds.\n\nThe packing in the column and the treating liquid is the stationary phase, while the inert gas flowing byu is the mobile phase.  Molecules are sorted accoding to their degree of interaction with the stationary phase.
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Either:\n\n(a) you're not getting a very clean separation, as the peaks should be vivid\n\nor\n\n(b) your detector is insuitable for the acids you're studying.\n\nAtleast, that's my analysis. Any A-Chem experts here?
210155
The current way would be ion chromatography.  There are older less reliable methods.  You test for the calcium separate form the anions.  The calcium can also be donw by ICP or AA.
269519
The test that I'm familiar with is thin layer chromatography.  This process uses the polarizability chararacteristics of each pigment in a plant sample.  In my experiment, spinach leaves are grounded and mixed with anhydrous sodium sulfate and sand.
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Rf values should be the same for the same plant pigments whenever you do the chromatogram. What will change is the pigments present and their amounts.
947826
You could check theses sites:\n\nhttp://www.liv.ac.uk/Chemistry/Links/reforganic.html\n\nhttp://matematicas.udea.edu.co/~carlopez/index2a.html\n\nhttp://www.anachem.umu.se/cgi-bin/jumpstation.exe?Chromatography\n\nhttp://www.organicworldwide.net/
480845
The two should be separable by HPLC
977136
A large number of biological compounds can be separated by thin layer chromatography (TLC). The specificity comes from the type of substrate that is deposited on the plates to use for separation and then the solvent systems that are used to develop the plates and separate the compounds.\n\nOne of the commonly used methods in research labs today is to differentiate between lipids or amino acids that have been phosphorylated by the action of a kinase enzyme. For instance, the presence of a newly added phosphate molecule onto a lipid like phosphatidyl inositol will create a new compound that can be separated from the original by TLC. Another example is when a protein is phosphorylated by the action of a kinase, you can digest the protein and compare it to an untreated sample and you will find a new spot corresponding to the phosphorylated peptide.\n\nDifferent types of sugars can also be separated by TLC. As can metabolites of various biological reactions. It is a little difficult to separate full-length intact proteins by TLC, but it is not impossible. The key features boil down to the choice of substrate and the mobile phase. In forensics, while I am not certain (not my area of expertise), I am relatively confident that drug metabolites can be isolated and verified by TLC.\n\nWhile TLC has a number of uses, it is most traditionally used to characterize substances that have undergone some sort of chemical alteration so that they can be identified when compared to an untreated sample of the same substance, for example, one sample plus or minus the addition of phosphate.
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Since your question refers to only the types of detectors used in HPLC, I assume that you understand how HPLC works so I will not go into that.  Each chemical refracts light differently.  As the various components elute from the column, a beam of light is passed through the eluted flow.  The components come out as bands of individual components.  Each band or component refracts the light and this refraction is measured by a detector.  The signal from the detector is amplified and sent to a recording device which records the refractive index of that component.  From the refractive Index, the component can be identified and by the strength of the signal, the amount can be determined.  \n\nThe UV/Visible detector simply uses the different wavelengths of light to determine the various components being eluted.  Each component absorbs light rays differently.  The wavelength Can be varied depending on the class of compounds being examined.  This allows for maximum sensitivity of the detector.  As each component is eluted, it passes through the detector.  The absorbence of light gives the identification of the component and the amount of light absorbed is directly related to its concentration.