Explore BrainMass


Chromatography refers to a set of physical techniques used for separating or analyzing mixtures. Preparative Chromatography focuses on the separation of chemical compounds from a mixture. This is a form of purification, where pure compounds can then be used in further experiments. Analytical chromatography focuses on the analysis of chemical mixture, usually to determine the identity of certain components, or to measure the relative concentrations of the analytes in a mixture. The process of chromatography involves dissolving the components of a chemical mixture in a fluid called the mobile phase. This carries the dissolved analytes through a specific material called the stationary phase. Depending on the identity of the analyte, the mobile phase will travel at varying speeds through the stationary phase. The speed of the specific analyte will correlate to a certain length, which is then compared to the length of the entire mobile phase to give the ‘Rf value.’ The Rf value has the formula: Rf = length of component travelled / total length of mobile phase By calculating the Rf value, identification of a chemical compound can be easily determined by calculating the speed at which it travels through the stationary phase. Thus, understanding the concept of chromatography is crucial for understanding how to separate or quantitatively analyze chemical mixtures.

Chromatography of River Water

Please help with the following problem. Suppose that you must go into court and testify as to the level of X in the river water. Your lawyer is concerned that your analytical results are lower than they should be because you cannot extract with benzene (distribution Ratio K=4) all of X from your samples. Assume the concentra

Reversed-phase liquid chromatography Questions

A mixture of organic acids was separated by reversed-phase liquid chromatography. The data obtained for the chart recording were as follows: For acid A, the peak appeared 22 cm after injection with a full width at baseline of 8 cm. For acid B, the peak appeared 34 cm after injection with a full width at baseline of 6 cm. A non-r

The Interpretation of Gas Chromatograms

A chromatogram would feature lines instead of peaks if: a) the best equipment available is used b) the separation is done by capillary electrophoresis c) if the temperature nears (or is equal to) the absolute zero d) neither of the above cases would suffice. B. Most modern chromatography instruments are equipped with: a)

Surface Acidity and Fluorine-Doping

In the attached paper, the authors claim that F-doping enhanced surface acidity. Why does the presence of fluorine increase surface acidity? Reference: Li, D., Haneda, H., Hishita, S., Ohashi, N., & Labhsetwar, N. K. (2005). Fluorine-doped TiO< sub> 2</sub> powders prepared by spray pyrolysis and their improved photocatalyt

Gas Chromatography

Please help with the following problem: Refer to the GLC traces given in Figure 6.16. These are analyses of the various fractions collected during the fractional distillation of the mixture of cyclohexane and toluene. The weight and mole correction factors (flame ionization detector) for cyclohexane are 0.84 and 0.78, respec

Solubility of Organic Compounds Lab Report

Lab 3: Solubility of Organic Compounds Objectives: - Understanding the relative solubility of organic compounds in various solvents. - Exploration of the effect of polar groups on a nonpolar hydrocarbon skeleton. Introduction: The solubility of a solute (a dissolved substance) in a solvent (the dissolving medium) is


1. Why is it dangerous to heat a liquid in a distilling apparatus that is closed tightly at every joint and has no vent to the atmosphere? 2. In your distillation of the binary mixture, which fractions contained more of the higher boiling component, the earlier fractions or the later fractions? expriment procedure

Reverse Phase HPLC - Why would myoglobin and hemoglobin give two separate peaks?

I conducted HPLC analysis of myoglobin and hemoglobin using a C18 and C4 column. Both proteins were in a buffer solution only. On the C4 column the order of the peaks was a reverse of the C18 column. The chromatographic output showed two peaks. Looking at the UV absorbance, I can attribute one of the peaks to the heme group (

Protein Purification Questions

Hey I am did a multiweek experiment doing a protein purification of Glutamate-Oxaloacetate Transaminase (GOT). I have a few questions about my experiment. 1. How does protein purification help in the real world? What's the larger picture? 2. I preformed a GOT Assay, GDH(Glutamate Dehydrogenase) Assay, Folin-Ciocalteau Ass

High-performance liquid chromatography

I recently did an experiment on high-performance liquid chromatography I am having a little trouble in the introduction. The introduction should just be a description of High-performance liquid chromatography and what I will learn from the experiment. I wrote a draft but my TA said that it could use some work. I was wondering if

Questions about HPLC Lab

Hey I am about to do a lab to determine the amount of caffeine and sodium benzoate in soft drinks via HPLC. To prepare I had to answer a series of questions before the lab. I am confused on some of them and request your help. The questions are: Why is it necessary to perform the HPLC separation at a pH of 3? How does the pH a

Quantitative Analysis : HPLC Chromatographs and Beer's Law

Please see the attached file for the fully formatted problems. 1.Based on the following figure explain which particle size produce the best resolution in HPLC and why? 2. To find the Ce4+ content in a solid, 4.37 g were dissolved and treated with and excess of iodate to precipitate Ce(IO3)4. The precipitate was filtered, w

Combined Gas Law and Mixtures of Gases

Introduction to the Ideal Gas Law A balloon is floating around outside your window. The temperature outside is 31 , and the air pressure is 0.700 . Your neighbor, who released the balloon, tells you that he filled it with 3.60 of gas. What is the volume of gas inside this balloon? Express your answer numerically in liters.

NMR Spectrum of Caffeine and Vapor Pressure of Sublimation

A. How many peaks would you expect to fin in the NMR spectrum of caffeine? B. What characteristic absorptions of bands would you expect to find in the infrared spectrum of caffeine?And show the infrared spectrum C. the vapor pressure of 1,2-dipheneylethane, p-dichlorobenzene, and 1,3,5-trichlorobenzene are 0.06, 11.2,

Gas Chromatography Questions

1. in gc (gas chromatography), what is the stationary phase? what is the moving phase? 2. as with the other chromatographic techniques we've studied, the polarity of the compounds affects their separation in gc. what is the other dominant factor that affects separation? 3. what would be the effect of increasing column temperat


-Why is a layer of sand above the alumina in the column in column chromatography? - What are the differences between column chromatography and thin layer chromatography? - If a compound had an Rf value of .5 in a particular solvent, how many column lengths of that solvent would it theoretically require for the compound to

Why Didn't my Chromatography Experiment Work Properly?

I did a lab on column chromatography and thin layer chromatography, and our sample was a spinach extract. I am trying to figure out if there is a correlation between the partition coefficient and the Rf used in thin layer chromatography. Is there one? For the column chromatography we used a 9:1 hexane: acetone, thenn 1:1 h

VOC Machine Printout

Help my understand and interrupt the VOC machine print out on three water samples.

Conversion of formalin to a solution of methanol

I am a pathologist and would like to know just how hard it would be to convert the used formalin (10% formaldehyde in water) to a solution of methanol. It seems to me that I just need a long column and bubble hydrogen gas through it. When the hydrogen gas is able to make it all the way to the top of the column all the formalin

Rf value on structural basis

1. The relative movement of the substance is related to polarity of the substance. The TLC sheet is coated with highly polar silica gel and the solvent has a much lower polarity. Explain the relative Rf values on a structural basis. 2. Explain why leaves " change color" in the fall. 3. How does the Structure of chlorophyll

Advantage of Sequencing a Protein in Separate Samples

The advantage of treating separate samples of a protein with two or more enzymes when sequencing a protein is that the products are a. more homogeneous b. sequenceable with out further chromatography c. fragments with the same N- and C-terminal amino acids d. fragments with sequence overlaps e. all are true

PI (isoelectric poin)

Based on predicted pI (for example, a pI for turnip peroxidase is 9.10), how can you use DEAE-sepharose to further purify peroxidase?

Separating and Identifying Isomers

(See attached file for full problem description with diagram) Question 1: List three methods in laboratory (I guess this means not involving high-tech instrumentation like in gas-liquid chromatography) to separate and identify the four reaction products in the above reaction. What are the advantages and disadvantages for each

Biochemistry Questions: Ionization and Substrate Binding

1. If the active site of a dipeptidase contains a glutamic acid residue (pKa 3.3) and a histidine residue (pKa 6.7), both of which must be charged for the substrate to bind, what is the optimal pH for substrate binding? 2. Lysozyme catalyzes the hydrolysis of C-O-C bonds between sugar residues in bacterial cell walls. The p

Determining amino acid sequences of peptide and octapeptide

1. What is the amino acid sequence of the peptide? The complete hydrolysis of an unknown nonapeptide revealed the presence of Glu, Val, Val,Gly,Lys, Lys, Tyr, Thr and Phe residues. The first amino acid to be detected as a phenylthiohydantoin derivative on Edman degradation of the peptide was glutamic acid. The only amino ac

Determine the primary structure of the peptide

In trying to deduce a primary structure of an peptide sequence... When does a polypeptide NOT contain a free carboxyl group? Are all peptides linear (or can they have a cyclic C-terminus)? What happens when treatment of the intact peptide with 2,4-dinitroflourobenzene (followed by complete hydrolysis and chromatography) y