AHydroxycarboxylic Acids

Table 7 reports the separation and resolution data for aliphatic and aromatic dl-a-hydroxycarboxylic acids on HPTLC-CHIR plates with concentrating zone where the selectivity coefficients appear to be higher than those obtained on Chiralplates using the same eluent (dichloromethane-methanol, 45:5 v/v). Vanadium pentoxide may be used for detection of aromatic and aliphatic compounds. The oxide (1.82 g) is dissolved in 30 mL of 1 molL"1 sodium carbonate by ultrasonic bath and, after cooling, 46 mL of 2.5 mol L"1 sulfuric acid and acetonitrile to 100 mL are added. Plates dipped in this solution and allowed to stand at room temperature give blue spots on a yellow background. All racemates studied were

Table 3 Retention and resolution data for racemic amino acids on home-made and precoated cellulose plates

Racemate

hRF1a

hRF2

ab

Eluent

Remarks

Trp

50(D)

53

1.12

A

Home-made microcrystalline cellulose plates

5-HydroxyTrp

25(D)

31

1.35

A

(Avicel SF, Funakoshi, Japan) 20 cm x 20 cm.

Kynurenine

54(D)

61

1.33

A

Development time 2.3 h; visualization: UV365.

3-Hydroxykynurenine

47(D)

53

1.27

A

A = methanol-butanol-benzene-water

5-Hydroxykynurenine

20(D)

26

1.40

A

2:1:1:1 (v/v/v/v).

3-Methoxykynurenine

55(D)

62

1.33

A

A/-a-acetylkynurenine

74(D)

82

1.60

A

Diaminoadipic acid

23(D, D)

28

1.30

B

Cellulose plates (Merck); B = methanol-

Diaminopimelic acid

25(D, D)

37

1.76

B

water-acetic acid 40 : 10 : 2 (v/v/v).

Trp

46(L)

52

1.27

C

DC-Alufolien Cellulose F254 plates (Merck)

5-HydroxyTrp

34(L)

41

1.34

C

(20 cm x 20 cm x 0.1 mm). Development time

Kynurenine

38(D)

47

1.44

C

1.8-4.5 h; migration distance 15 cm; visualiz-

4-AminoPhe

40(L)

45

1.22

D

ation: ninhydrin. Eluents: methanol-water 3 : 1

Phe-4-sulfonic acid

70(L)

73

1.15

Ec

(D), 7: 3 (F), 3: 2 (C); n-butanol-acetic

o-Tyr

57

61

1.17

F

acid-water 1:1:1 (E).

m-Tyr

55

59

1.17

F

Layers heated at 110°C for 5 min before use.

p-Tyr

81(L)

83

1.14

Fc

p-Tyr-3-sulfonic acid

30(L)

40

1.55

E

Dopa

53(L)

57

1.17

C

Trp

40(L)

49

1.44

G

Avicel SF plates 20 cmx 20 cm, Lot 8390,

His

11(D)

13

1.20

G

Funakoshi, Japan. Development time 11.5 h at

Phe

55(L)

59

1.17

G

0°C. Visualization: ninhydrin.

Tyr

53(L)

60

1.33

G

G = ethanol-pyridine-water 2:3:1 (v/v/v) or

Dopa

43(L)

50

1.32

G

1:1:1 (v/v/v).

Cys

6(D)

8

1.35

G

Thr

51(D)

56

1.22

G

Tyr

75(L)

81

1.42

H

DC-Plastikfolien Cellulose plates (Merck, Cat.

Trp

57(L)

62

1.23

H

No. 5577), 20 cm x 20 cm x 0.1 mm.

4-MethylTrp

29(L)

36

1.37

H

Migration distance 10 cm.

42(L)

52

1.50

I

Visualization: iodine vapour.

5-MethylTrp

37(L)

46

1.45

H

Eluents: 0.1 mol L_1 NaCl (H); ethanol-

48(L)

54

1.27

I

pyridine-water 1:1:1 (I).

6-MethylTrp

32(L)

39

1.35

H

47(L)

55

1.37

I

7-MethylTrp

34(L)

41

1.34

H

4-FluoroTrp

38(L)

44

1.28

H

53(L)

60

1.33

I

5-FluoroTrp

39(L)

45

1.27

H

59(L)

64

1.23

I

6-FluoroTrp

41(L)

46

1.22

H

61(L)

65

1.18

I

5-HydroxyTrp

31(L)

36

1.25

H

41(L)

48

1.33

I

Kynurenine

48(L)

55

1.32

H

43(L)

51

1.38

I

Two successive developments with the same eluent.

Two successive developments with the same eluent.

completely resolved, the d forms being the most retained.

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