Chromatography Be able to describe in detail the process of TLC (sample preparat

Question

Chromatography Be able to describe in detail the process of TLC (sample preparation, spotting, developing, visualization, and analysis). Know the uses for TLC in organic chemistry Know the physical property in operation for TLC separation and how the dielectric constant for a solvent influences the Rf values. Know the following terms: adsorption, eluent, spotter, visualization, developing, stationary phase, and Rf value. Know how to calculate Rf values. Know how to use Rf values for identification of an unknown or the components of an unknown sample. Know how to use TLC to determine purity. Know how to use TLC to follow the progress of a reaction. Know how to choose the correct solvent for the best separation. Know how to visualize the compounds of the TLC plate (UV light and others).

Explanation / Answer

1. Sample preparation:- Solvent is transferred into the container with 0.5-1cm in dept from the bottomSolvent is transferred into the container with 0.5-1cm in dept from the bottom

TLC Plate Preparation:-

ØCommercialy obtained with 5cm x 20cm in size

ØPrepare your size when neccesary

ØLine 1 cm from the bottom with a pencil as a part should be spotted.

Spotting TLC Plates:-

ØMake sure that your sample is liquified already.

Ø stick it using capillary pipe & spott onto the line you have made

Developement of Plate:-

Øafter spotting, put the plate inside the chamber in the ascendant position

ØMake sure that the dept of solvent doesn’tb touch the spots

ØLet it develop up to the 1cm from the top of plate

ØAfter that, pull out the plate from the cahmber and let the solvent be vaporized

Detection of Spot:- The color samples are easy to be seen and no need to use UV lamp to detect them

1)Iodination-put the plate in which the spots face to the iodine crystall and see what is the spot color changing

2)Ninhydrin:

-spesific identification of amino acid compounds.

       - Ninhydrin solution will show a purple spot when it is sprayed to the amino acid spot.

3)KMnO4

       used to identify a reducing agent such as glucose, fructose, vitamin C and others.

4)Alkaline tetrazolium blue

      specificaly used for corticosteroid identification

Qstn2.USE OF TLC:-

Qstn.3 Ans:-

The distance taken through by the solvent to move up will be assigned as solfent front

- The distance taken trrough by the sample to move up will be assign as sample front

- Rf value is obtained by dividing the sample front toward solvent front

Rf = sample front

       solvent front

Qstn.4: Eluent:-When the TLC plate is placed in the jar, the eluent serves as the mobile phase – moving up the silica on the plate (also by capillary action). The different compounds in the analyte mixture will be carried in the eluent (up the plate) at different rates depending on polarity

Spotters;-TLC spotters are made from glass capillary tubes, available from most suppliers of chemicals or glassware

Related Questions

Navigate

• Browse (All)
• Browse C
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.