Indirect method

This method involves reaction of the enantiomeric mixture with a suitable chriral reagent to make the corresponding diastereomeric derivatives prior to chromatography; the choice of chiral selector is

Table 17 values of amino acids on untreated plates and plates impregnated with metal sulfates

Aminoacids Unimpregnated Plate impregnated with plate -

Asp

21

51

54

50

62

58

52

59

64

Glu

25

51

63

55

59

61

54

58

65

Phe

45

64

74

67

72

74

69

68

65

Tyr

46

66

73

68

72

70

72

68

71

Lys

7

15

21

22

18

18

16

32

25

Orn

28

15

23

23

19

23

20

28

T

Arg

30

20

25

30

28

28

25

35

33

Ala

30

50

52

53

60

55

49

58

73

Val

48

60

70

58

71

65

59

65

70

Ser

29

45

57

48

57

52

44

56

48

Hypo

26

42

52

47

48

50

43

57

45

Gly

20

43

58

48

52

40

45

54

55

Leu

50

67

72

69

75

71

74

69

SF

Cys

SF

24

37

32

34

35

30

34

40

T, Tailing; SF, migrates with solvent front. hRF values are the average of at least five determinations.

Table 18 TLC of amino acids on impregnated silica gel layers

Solvent system

Impregnation iso-Amyl alcohol-H2O-HOAc 6:5:3

0.1 mol L~1 HOAc in aq. 50% MeOH Aq. MeOH + I2 (KCl or HOAc added)

Aq. NH4NO3 or HNO3 or H2O-HOAc-MeOH (79 : 1 : 20) H2O

H2O-butanol-anhyd. HOAc n-Butanol-acetic acid-water

Propan-2-ol-EtOAc-acetone-methanol-n-pentyl alcohol-aq. 26% NH3-water in first direction; and Butanol-acetone-propan-2-ol-formic acid-water in second direction 1 mol L~1 NH4NO3-0.1 mol L~1 HNO3

MeOH-butyl acetate-HOAc-pyridine 4 : 4

n-Butanol-acetic acid-CHCl3 3 :1

n-Butanol-acetic acid-ethanol 3 :1

Butyl acetate-MeOH-HOAc-pyridine 4 : 4

Pyridinium tungstoarsenate Silanized silica and triethanol amine. SDS, sodium di-octylsulfonate, dodecyl benzene sulfonic acid Dodecyl benzene sulfonic acid Ammonium tungstophosphate and dodecyl benzene sulfonic acid Ammonium tungstophosphate

Polyamide

Kieselguhr or cellulose Starch-agar (1:1) Cellulose

Ammonium tungstophosphate Copper sulfate and polyamide

Hydroxides of Mg, Ca, Ba, Sr

limited due to the feasibility of its reaction with the analyte.

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