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Chromatography
Chromatography is a set of techniques used to separate mixtures in a chemistry lab setting. The word chromatography means "color writing" and some of the first experiments in chromatography involved separating chlorophyll in plants.
649 Questions
Difference between isothermal and isoperibol calorimeter?
In an isothermal calorimeter, the temperature inside the calorimeter remains constant during the measurement, preventing any heat exchange with the surroundings. In an isoperibol calorimeter, the calorimeter is well-insulated and allows heat exchange with the surroundings, but the heat loss or gain is accurately measured and compensated for.
Which dyes adhere best to chromatography paper?
Dyes that are more polar tend to adhere better to chromatography paper because they interact more strongly with the cellulose fibers in the paper. Therefore, water-soluble dyes like food coloring or ink tend to work well for paper chromatography.
These components would travel the farthest up the filter paper in chromatography because they are less attracted to the paper and more attracted to the solvent. They are likely to be found closer to the top of the paper where the solvent front has reached.
How to prepare 100 ppm solution of KMnO4?
I will assume that you will start from the crystals of permanganate:
Calculations:
M.M. potassium permanganate: 158.04 g/mol
mol KMnO4 in 10mL sol'n: 1.5 mol/L x 10 mL x (1 L / 1000 mL) = 0.015 mol
grams potassium permanganate: 0.015 mol x 158.04 g/mol = 2.3706 g / 10 mL sol'n
Preparation:
1. Weigh out analytically 2.3706g KMnO4 into a 10 mL volumetric flask.
2. Dilute to the mark with dH2O.
What detectors are used in HPLC?
The detector for an HPLC is the component that emits a response due to the eluting sample compound and subsequently signals a peak on the chromatogram. It is positioned immediately posterior to the stationary phase in order to detect the compounds as they elute from the column. The bandwidth and height of the peaks may usually be adjusted using the coarse and fine tuning controls, and the detection and sensitivity parameters may also be controlled (in most cases). There are many types of detectors that can be used with HPLC. Some of the more common detectors include: Refractive Index (RI), Ultra-Violet (UV), Fluorescent, Radiochemical, Electrochemical, Near-Infra Red (Near-IR), Mass Spectroscopy (MS), Nuclear Magnetic Resonance (NMR), and Light Scattering (LS). Refractive Index (RI) detectors measure the ability of sample molecules to bend or refract light. This property for each molecule or compound is called its refractive index. For most RI detectors, light proceeds through a bi-modular flow-cell to a photodetector. One channel of the flow-cell directs the mobile phase passing through the column while the other directs only the mobile phase. Detection occurs when the light is bent due to samples eluting from the column, and this is read as a disparity between the two channels.
Ultra-Violet (UV) detectors measure the ability of a sample to absorb light. This can be accomplished at one or several wavelengths:
A) Fixed Wavelength measures at one wavelength, usually 254 nm
B) Variable Wavelength measures at one wavelength at a time, but can detect over a wide range of wavelenths
C) Diode Array measures a spectrum of wavelengths simulateneously
UV detectors have a sensitivity to approximately 10-8 or 10 -9 gm/ml.
Fluorescent detectors measure the ability of a compound to absorb then re-emit light at given wavelengths. Each compound has a characteristic fluorescence. The excitation source passes through the flow-cell to a photodetector while a monochromator measures the emission wavelengths.
Has sensitivity limit of 10-9 to 10-11 gm/ml.
Radiochemical detection involves the use of radiolabeled material, usually tritium (3H) or carbon-14 (14C). It operates by detection of fluorescence associated with beta-particle ionization, and it is most popular in metabolite research. Two detector types:
A) Homogeneous- Where addition of scintillation fluid to column effluent causes fluorescence.
B) Heterogeneous- Where lithium silicate and fluorescence caused by beta-particle emission interact with the detector cell.
Has sensitivity limit up to 10-9 to 10-10 gm/ml.
Electrochemical detectors measure compounds that undergo oxidation or reduction reactions. Usually accomplished by measuring gain or loss of electrons from migrating samples as they pass between electrodes at a given difference in electrical potential.
Has sensitivity of 10-12 to 10-13 gm/ml
Mass Spectroscopy (MS) Detectors- The sample compound or molecule is ionized, it is passed through a mass analyzer, and the ion current is detected. There are various methods for ionization:
A) Electron Impact (EI)- An electron current or beam created under high electric potential is used to ionize the sample migrating off the column.
B) Chemical Ionization- A less aggresive method which utilizes ionized gas to remove electrons from the compounds eluting from the column.
C) Fast Atom Bombarbment (FAB)- Xenon atoms are propelled at high speed in order to ionize the eluents from the column.
Has detection limit of 10-8 to 10-10 gm/ml.
Nuclear Magnetic Resonance (NMR) Detectors- Certain nuclei with odd- numbered masses, including H and 13C, spin about an axis in a random fashion. However, when placed between poles of a strong magnet, the spins are aligned either parallel or anti-parallel to the magnetic field, with the parallel orientation favored since it is slightly lower in energy. The nuclei are then irradiated with electromagnetic radiation which is absorbed and places the parallel nuclei into a higher energy state; consequently, they are now in "resonance" with the radiation. Each H or C will produce different spectra depending on their location and adjacent molecules, or elements in the compound, because all nuclei in molecules are surrounded by electron clouds which change the encompassing magnetic field and thereby alter the absorption frequency.
Light-Scattering (LS) Detectors- When a source emits a parallel beam of light which strikes particles in solution, some light is reflected, absorbed, transmitted, or scattered. Two forms of LS detection may be used to measure the two latter occurrences:
A) Nephelometry- This is defined as the measurement of light scattered by a particulate solution. This method enables the detection of the portion of light scattered at a multitude of angles. The sensitivity depends on the absence of background light or scatter since the detection occurs at a black or null background.
B) Turbidimetry- This is defined as the measure of the reduction of light transmitted due to particles in solution. It measures the light scatter as a decrease in the light that is transmitted through the particulate solution. Therefore, it quantifies the residual light transmitted. Sensitivity of this method depends on the sensitivity of the machine employed, which can range from a simple spectrophotometer to a sophisticated discrete analyzer. Thus, the measurement of a decrease in transmitted light from a large signal of transmitted light is limited to the photometric accuracy and limitations of the instrument employed.
Near-Infrared Detectors- Operates by scanning compounds in a spectrum from 700 to 1100 nm. Stretching and bending vibrations of particular chemical bonds in each molecule are detected at certain wavelengths. This is a method which offers several advantages: speed (sometimes less than 1 second), simplicity of preparation of sample, multiple analyses from single spectrum, and nonconsumption of the sample.
What is the stationary phase in DB-624?
In DB-624, the stationary phase is a phenyl arylene polymer that has a 6% cyanopropyl substituent. This phase is commonly used in gas chromatography for separating a wide range of analytes, especially non-polar and moderately polar compounds.
What is carbon load in hplc column?
Carbon load is the percent by weight of carbon on the stationary phase. It measures how much organic material has been chemically attached to the surface of silica. For a reversed phase column, more carbon load usually means more retention for nonpolar compounds like protines. general rane of carbon load is 8-12%.
What is the principle behind the Gas Chromatography?
Gas is pushed threw a filimint gas is broken down into 4 gases and total gas so there is gas c1 c2 c3 c4 and tg or total gas so say 100 units of gas come in to a cromatograph 20 units burn at c1 level that means there is 20 units of c1 c2 level 30 units of gas burns away. I used to be a mud logger in the oilfields :) the most easy job i ever had 300 dollars a day for doing nothing :)
What happens in paper chromatography in inorganic ions?
In paper chromatography, inorganic ions can be separated based on their different affinities to the paper and mobile phase. As the mobile phase moves through the paper, ions with stronger affinities to the paper will move more slowly, causing them to separate from ions with weaker affinities. This differential migration will result in the separation of inorganic ions on the paper chromatogram.
The molar absorptivity of Cu2+ at 620 nm can be calculated using Beer-Lambert law equation A = εlc, where A is the absorbance, ε is the molar absorptivity, l is the pathlength (1.00 cm), and c is the concentration. Using the concentration- absorbance curve given (y = 0.727x + 0.0557), at 620 nm, x = c = 1. Therefore, substituting these values into the Beer-Lambert equation will give you the molar absorptivity of Cu2+ at 620 nm.
Mass spectrometer. The combination of gas chromatography and mass spectrometry (GC-MS) allows for the separation of compounds based on their physical properties in the gas chromatograph, followed by the specific identification of those compounds based on their mass-to-charge ratio in the mass spectrometer. This coupling provides enhanced specificity and sensitivity in compound identification compared to using gas chromatography alone.
What is the difference between absorption and emission spectrum?
Emission spectrum: lines emitted from an atom.
Absorption spectrum: absorbed wavelengths of a molecule.
The 10 examples of biotechnology products?
- Insulin for diabetes treatment
- Genetically modified crops for increased yield and resistance
- Monoclonal antibodies for cancer treatment
- Enzymes for laundry detergents
- Recombinant vaccines for infectious diseases
- Biodegradable plastics from bio-based materials
- Biofuel production from algae or crops
- Gene therapy for genetic disorders
- Assisted reproductive technologies for infertility treatments
- Diagnostic tests for genetic diseases
Why does fluorene move faster down the column chromatography than fluorenone?
Well it depends on the solvent you are using, but lets assume you use pentane as the solvent for fluorene and diethyl ether as the solvent for fluorenone. Used in this order, fluorene should actaully move slower down the column due to the the polarity of the alumina and the nonpolarity of the solvent (pentane). Since fluorene is less polar so, remember the rule like dissolves like? Well, this kind of applies to chromatography wherein rather than dissolve just replace it with moves with, so like moves with like. That being said the pentane will "carry" the fluorene through the alumina slower than the latter (which I will explain). Fluorenone is polar because of its C=O bond, that being said the dielectric constant of diethyl ether is 4.3 which means it has intermediate polarity (remember that pentane has a dielectric constant of 2.1 I think, so it is nonpolar). Since the alumina, diethyl ether, and the fluorenone are all polar, the fluorenone will travel faster through the alumina than would the fluorene, because there is no attraction between all these polar compounds which will allow it to move faster, rather than a nonpolar and polar chemical having an attration towards each other and thus moving more slowly.
Hope this helps,
Branden
Is ion-exchange chromatography is reverse phase chromatography?
The principal of ion exchange chromatography is the most popular method for purifying protein compounds.Other charged molecules are also called an ion exchange if of a protein nature.
[Fig 1. Principle of anionic and cationic exchangers.]
Biomolecular binding strength depends on solution pH, since it affects the number of ions available for exchange. Proteins can be zwitterions, so you'll need to use either an anionic or cationic exchanger. Whatever the conditions, we have to determine the isoelectric point of the protein at different pHs to see what charges the proteins can have and where it's electroneutral. When pH < pI of a given molecule, it will be positively charged and we'll need a cation exchanger; vice versa when pH > pI. The amphoteric character (ability to react as either acid or base) of proteins allows us to detect ionic interference of other substances and improve our own protein separation. The principle of ion exchange processes will be explained more clearly using an anionic exchange as an example. Today, most people use synthetic organic ion exchangers on a polystyrene base (DOWEX) or natural polymers like cellulose, dextran, or silicate. The macromolecules of the ion exchanger normally make up a 3D network, onto whose surface a huge number of ionizable groups are covalently bonded. Whereas the type of matrix material is generally flow characteristic (the type of ions used and their chemical/mechanical stability are more solid), the groups covalently-bonded to the matrix and the strength of those bonds determine what the exchangable ions can be: every group gives an exchange of very basic (anion exchanger) for very acidic (cation exchanger) character.
[Fig 2. Principle of an ion exchange process.]
Typical functional groups in an anion exchanger are quaternary amines such as diethyl aminoethyl groups (DEAE - non-denaturing, sorbents have good loading capacity), while those for cation exchangers include organic and inorganic acids like carboxymethyl groups (CMs) or sulfonates. These groups are covalently coupled to the matrix material (Fig. 3). Since exchange groups are only inserted in their ionic form, it's important to know their pK values. Such values can be found by a simple titration curve, as shown for a CM sephadex in Fig 4. Because so many biologically important substances contain ionizable functional groups (amino acids, proteins, nucleotides, nucleic acids, metabolites, etc), biochemical methods for the isolation and separation of charged compounds are quite valuable - some charged compounds are electrostatically bound to the exchanger and others are not.
Retention time in High Performance Liquid Chromatography (HPLC) refers to the time it takes for a compound to travel through the chromatography column and elute from the detector. It is a key parameter for identifying and characterizing compounds in a sample. Retention time is influenced by factors such as the column type, mobile phase composition, and compound properties.
o-nitroaniline will elute first in column chromatography because it has a lower affinity for the stationary phase due to its higher polarity compared to p-nitroaniline. This results in o-nitroaniline moving more quickly through the column and being eluted first.
Chromatography is the methods used to separate complex mixtures. The components to be separated are distributed between two phases, a stationary and mobile phase. There are many types of chromatography: Liquid Chromatography, Gas Chromatography, Thin-layer Chromatography, and Paper Chromatography. As the separation occurs, a mixture is separated into its components. As a result, the molecules of the components have different masses, and so they travel along a medium at different rates.
The process of chromatography can be used on a T-shirt. The mobile phase would be the alcohol and the stationary phase is the permanent markers. The solvent is the alcohol and the solutes are the marks made by the permanent markers. When the solvent, in this case, the alcohol, is distributed onto the shirt, some of the marks dissolve in the solvent. After a period of time, the marks on the medium, the T-shirt, end up spread out between the original spot and the point the solvent reaches. In designing the shirt, the alcohol spread the marker making concentric rings of different colors. This effect of concentric rings occurs since the different components of the permanents markers travel at different rates.
In any chemical or bio-processing industry, the need to separate and purify a product from a complex mixture is a necessary and important step in the production line. For example, pharmaceutical industry uses chromatography to isolate penicillin and other antibiotics. Proteins can even be separated into amino acids through the process of chromatography. Chromatography is also used in crime scene investigation for DNA and RNA sequencing as well as in many scientific studies to identify unknown organic and inorganic compounds. This separation of mixtures is useful to us in various ways.
Using notes outside of a given key to produce heightened color is referred to as?
Using notes outside of a given key to produce heightened color is referred to as chromaticism. This technique involves incorporating notes that are foreign to the key signature, adding tension and interest to the music. Chromaticism is commonly used in various musical styles to create unique and expressive harmonies.
Why is plasma called a high-energy state of matter?
Let's consider for a moment what we usually mean when we refer to states of matter. Typically, we think of four states: solid, liquid, gas, and possibly plasma. There are more, but for this explanation it will be easiest to think of it this way.
Now, let's look at how we move from one state to another. Suppose you have a block of ice, and you want to melt it. How are you going to do this? Most likely, you would suggest heating it. But heating is really just the introduction of thermal energy to your block of ice. In other words, you're adding energy, and as the molecules of water get more energetic, they change states so they can move around more easily. Thus, you go from solid to liquid.
The same reasoning goes for the other phase transitions. So, in our four-state scheme (again, solid->liquid->gas->plasma), plasma is the highest energy state of matter.
What Variables that affect column chromatography?
Answer:
The factors which affect the chromatography are:
Temperature
Pressure
Flow rate of mobile phase
Sample preparation
What are the similarities between paper chromatography and electrophoresis?
Chromatography is a collective term for a family of lab techniques for the separation of the mixtures.It involves a passing a mixture dissolved in a mobile phase through a stationary phase.
Electrophoresis is the process by which molecules (such as proteins, DNA, or RNA fragments) can be separated according to size and electrical charge by applying an electric current to them. Each kind of molecule travels through the medium at a different rate, depending on its electrical charge and molecular size
In the electrophoresis techniques electricity is required and positive charge goes to the cathode whereas the negative charges goes to the anode (opposite charges attraction)
but in Chromatography there is no need for the current or electricity .
What are the disadvantages of paper chromatography over thin layer chromatography?
Fear god and think about your death (the eternal life if you are a christian woe to you jesus is not god or the son of god if you are an atheist woe to you who is making you live now and if you are a muslim job well done may allah make your life easy for and have mercy on you.
Why is there an Iron chloride impurity in chromatography experiment?
Iron chloride impurity may arise in chromatography due to its presence in the sample or from contamination in the solvent or column material. It can cause interference with the separation process and lead to inaccurate results. Proper precautions should be taken to minimize the presence of impurities in chromatography experiments.
Why do colors show up on paper chromatography?
I'm working on the same thing in school. I think that it has something to do with food coloring mixed with wax to make different color crayons. Then rubbing the hardened wax on the papper makes colors appear. I hope i helpped but just to make sure check other websites because i dont even beleive myself lol.
