Using spectrophotometer to measure the concentration of compounds

Column Chromatography Apparatus The equipment needed for column chromatography is not elaborate, consisting only of cylindrical glass or Teflon tube that has a restricted outflow orifice. The dimensions of the tube are not critical and may vary from 10 to 40 mm in inner diameter and from to mm in length. For a given separation, greater efficiency may be obtained with a long narrow column, but the resultant flow rate will be lower.

Using spectrophotometer to measure the concentration of compounds

Principle[ edit ] Figure 1. The Coomassie Brilliant Blue G dye exists in three forms: If there's no protein to bind, then the solution will remain brown. The dye forms a strong, noncovalent complex with the protein's carboxyl group by Van der Waals force and amino group through electrostatic interactions.

These pockets Using spectrophotometer to measure the concentration of compounds the protein's tertiary structure bind non-covalently to the non-polar region of the dye via the first bond interaction van der Waals forces which position the positive amine groups in proximity with the negative charge of the dye.

The bond is further strengthened by the second bond interaction between the two, the ionic interaction.


The binding of the protein stabilizes the blue form of the Coomassie dye; thus the amount of the complex present in solution is a measure for the protein concentration, and can be estimated by use of an absorbance reading. The anionic bound form of the dye which is held together by hydrophobic and ionic interactions, has an absorption spectrum maximum historically held to be at nm.

Sodium dodecyl sulfate SDSa common detergent, may be found in protein extracts because it is used to lyse cells by disrupting the membrane lipid bilayer and to denature proteins for SDS-PAGE.

While other detergents interfere with the assay at high concentration, the interference caused by SDS is of two different modes, and each occurs at a different concentration. This can cause underestimations of protein concentration in solution. When SDS concentrations are above CMC, the detergent associates strongly with the green form of the Coomassie dye, causing the equilibrium to shift, thereby producing more of the blue form.

A high concentration of buffer will cause an overestimated protein concentration due to depletion of free protons from the solution by conjugate base from the buffer. This will not be a problem if a low concentration of protein subsequently the buffer is used. This requires spectrophotometers capable of measuring in the UV range, which many cannot.

Not all proteins contain these amino acids, a fact which will skew the concentration measurements. It is done in one step where the Bradford reagent is added to a test tube along with the sample. After mixing well, the mixture almost immediately changes to a blue color.

Only the molecules that bind to the proteins in solution exhibit this change in absorption, which eliminates the concern that unbound molecules of the dye might contribute to the experimentally obtained absorption reading.

This process is more beneficial since it is less pricey than other methods, easy to use, and has high sensitivity of the dye for protein. This assay is one of the fastest assays performed on proteins. The dye reagent is a stable ready to use product prepared in phosphoric acid.

It can remain at room temperature for up to 2 weeks before it starts to degrade. Protein samples usually contain salts, solvents, buffers, preservatives, reducing agents and metal chelating agents.

These molecules are frequently used for solubilizing and stabilizing proteins. Other protein assay like BCA and Lowry are ineffective because molecules like reducing agents interfere with the assay. It is a sensitive technique.

It is also very simple: This method can also make use of a Vis spectrophotometer. In making these dilutions, error in one dilution is compounded in further dilutions resulting in a linear relationship that may not always be accurate.

Basic conditions and detergents, such as SDS, can interfere with the dye's ability to bind to the protein through its side chains. The Bradford assay depends on the sequence of the protein.

Thus, if the protein does not contain an ideal number of aromatic residues, then the dye will not be able to bind to the protein efficiently. Another disadvantage of the Bradford Protein Assay is that this method depends on comparing the absorbance of the protein to that of a standard protein.

So if the protein does not react to the dye in a similar way as the standard protein, it is possible that the concentration is off. The reagents in this method tend to stain the test tubes. Same test tubes cannot be used since the stain would affect the absorbance reading.

This method is also time sensitive. When more than one solution is tested, it is important to make sure every sample is incubated for the same amount of time for accurate comparison.

This modified Bradford assay is approximately 10 times more sensitive than the conventional one. This is a disadvantage because the preference of the dye to bind to these amino acids can result in a varied response of the assay between different proteins.

Using spectrophotometer to measure the concentration of compounds

Changes to the original method, such as increasing the pH by adding NaOH or adding more dye have been made to correct this variation.In chemistry, spectrophotometry is the quantitative measurement of the reflection or transmission properties of a material as a function of wavelength.

It is more specific than the general term electromagnetic spectroscopy in that spectrophotometry deals with visible light, near-ultraviolet, and near-infrared, but does not cover time-resolved spectroscopic techniques. Bee pollen is a good source of bioactive compounds.

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• The composition of bee pollen depends strongly on plant source. • Solvent extraction has been the most used sample treatment. Using Spectrophotometer to measure the concentration of compounds The spectrophotometer can mensurate the strength of light absorbed indirectly by the solutes in solution because each solution has its ain characteristic soaking up movables.

Withdrawn Standards. ANSIZ American National Standard for Personal Protection - Protective Footwear. A4- Withdrawn Specification for Medium-Carbon-Steel Splice Bars. A chemical formula is a way of expressing information about the proportions of atoms that constitute a particular chemical compound, using a single line of chemical element symbols and numbers.

Published: Mon, 5 Dec The spectrophotometer can measure the intensity of light absorbed indirectly by the solutes in solution because each solution has its own characteristic absorption chattels.

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