Paper chromatography experiments

Products from the Reaction of Vanillyl Alcohol with Aqueous Alkali. Table VI shows the results of a paper chromatography experiment comparing the R/ values of compounds formed by the reaction of vanillyl alcohol and sodium hydroxide with R/ values of reference com-... 

Conduct a paper chromatography experiment with three different water-soluble colored markers. 

Those of you that did the paper chromatography experiment will recall how large the spots were beeause an 18-hour development allowed time for lateral difiiision. Here, with only 5-10 minutes of developing time, the spots don t have time to diffuse so they are small. The more uniform spots make both quantitative and qualitative analysis easier. 

Deleted. Three experiments that use mercury have been deleted. The paper chromatography experiment is deleted because thin-layer chromatography is predominantly used in its place today. For space reasons, the presentation of catalytic methods and the corresponding experirnent are deleted from the text in favor of enzymatic kinetic methods. Also, the anion chromatography separation of cobalt and nickel is omitted. 

The first of the two experiments given below illustrates the separation of amino-acids, now an almost classic example of the use of paper chromatography the second illustrates the separation of anthranilic acid and iV-methylanthranilic acid. Both experiments show the micro scale of the separation, and also the fact that a mixture of compounds which are chemically closely similar can be readily separated, and also can be identified by the use of controls. 

FIGURE 16.15 Suggested pattern for paper chromatography in Experiment 61, step 1. 

Experiment 61 Identification of Amino Acids in Food by Paper Chromatography... 

Many types of substances can be separated and analyzed using this technique. In this experiment, you will use paper chromatography to separate the dyes in water-soluble black ink. 

Partition chromatography as described in this section may be applied to two major types of problems (1) identification of unknown samples and (2) isolation of the components of a mixture. The first application is, by far, the more widely used. Paper chromatography and TLC require only a minute sample size, the analysis is fast and inexpensive, and detection is straightforward. Unknown samples are applied to a plate along with appropriate standards, and the chromatogram is developed as a single experiment. In this way any changes in experimental conditions (temperature, humidity, etc.) affect standards and unknowns to the same extent. It is then possible to compare the Rf values directly. 

The primary structure of a peptide or protein is defined by the sequence of amino acids. In this experiment the procedures that are in common use to determine protein primary structure are applied to an unknown dipeptide. Amino acid composition of the peptide will be determined by acid hydrolysis followed by HPLC, CE, or paper chromatography. The identity of the NH2-terminal amino acid will be achieved by the dansyl method followed by thin-layer chromatography. 

Other Gaseous Oxygen Oxidations. Other, almost identical oxidations were performed in the same manner at 160°-170°C. and at 170°-180°C. for longer reaction times. Five experiments in all were made. Qualitative paper chromatography indicated very little difference between the individual experiments. However, quantitative differences were noted for the several isolated fractions. 

Experiment I. The sample was first separated into fractions by a partition column, and the fractions were further fractionated by descending paper chromatography. A schematic representation of these procedures and the results is shown in Figure 2. 

Proteinoids accelerate the conversion of pyruvic acid to acetic acid and carbon dioxide. In a typical experiment, a mixture of 20 mg of proteinoid and 0.4 mg of radioactive pyruvic acid in 20 ml of 0.2 NTris buffer, pH 8.3, is incubated at 37.5 °C for 1, 2 or 3 days. The evolved 14C02 is absorbed in NaOH solution, and acetic acid is identified by paper chromatography and by preparing a derivative of acetic acid, namely p-bromophenacyl acetate 20). 

While you are waiting for the paper chromatogram to develop (step no. 7), you can perform the column chromatography experiment. Take a 25-mL buret. (You may use a chromatographic column, if available, of 1.6 cm diameter and about 13 cm long see Fig. 29.8. If you use the column instead of the buret, all subsequent quantities below should be doubled.)... 

Paper chromatography uses paper (cellulose) as the stationary phase, to separate slightly polar organic compounds from each other it is used particularly in undergraduate laboratory experiments. 

A fourth method, analysis of sugar alcohols after reduction by [3H]-NaBH4 and separation by paper chromatography, is described in detail in Experiment 11. 

A number of other experiments carried out at tracer level concentrations are consistent with the formation of the hydroxide of Po and the polonite ion. Deposits of polonium on gold electrodes are solnble in boiling water and this has been attribnted to formation of Po(OH)4. Tracer level Po can be precipitated from its aqneons solntions in the presence of Bi(OH)3 or Fe(OH)3 carriers with alkali and is presumably carried as the hydroxide. Tracer level Po dissolves in aqneons alkah and the solnbihty increases with increasing concentration of hydroxide ion. Also, a nentral species, postulated to be Po(OH)4 was identified by paper chromatography. 

It is important to confirm the identity of pesticide residues convincingly. Some methods, such as TLC, paper chromatography, or p-values share the same physical property of partition in achieving separations of mixtures. They do not give independent evidence for the identity of a compound. Similarly, GLC retention times for a compound on different stationary phases are often highly correlated. Thus, the choice of confirmatory techniques should be carefully made. Although powerful methods such as GC/MS are being studied, there is a need for simpler operations—for instance, the formation of chemical derivatives. Experiments with aldrin and dieldrin have revealed a number of reactions which are convenient for the confirmation of residues of these compounds. 

As would be expected from the above considerations, substitution at C6 of a hexose has, at most, only a minor effect on the course of saccha-rinic acid formation. Thus, 6-0-(a-D-galactosyl)-D-glucose (melibiose) plus lime-water gives lactic acid and a mixture of the corresponding metasac-charinic, isosaccharinic, and saccharinic acids.The qualitative experiments with melibiose and with 6-0-methyl-D-glucose, based mainly on paper chromatography, suggest that the metasaccharinic acids may be the principal products from hexoses substituted at C6. 

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