Miscellaneous Nitrogen Compounds

Because of the possible presence of nitroso carcinogens in foods, the separation and determination of

Table 6 Retention data (hRF) of indole derivatives under different experimental conditions3

Indole derivative

Silica gel G

Sil Cw-50/UV254

EluentA

Eluent B

Eluent C

Eluent D

Eluent E

Indole

84

73

16

13

97

Skatole

87

78

-

-

-

3-Hydroxymethylindole

84

45

-

-

-

Indole-3-aldehyde

81

20

25

18

60

Indole-3-acetaldehyde

86

46

32

22

96

Indole-3-ethanol

-

-

29

23

74

Indole-3-acetone

-

-

24

18

95

Indole-3-acetonitrile

85

46

23

17

95

Indole-2-carboxylic acid

-

-

34

78

63

Indole-3-carboxylic acid

-

-

-

-

-

Indole-5-carboxylic acid

-

-

69

89

75

Indole-3-acetic acid

31

28

62

84

61

Indole-3-propionic acid

38

34

22

77

75

Indole-3-butyric acid

40

38

14

69

81

Indole-3-glyoxylic acid

-

-

61

82

0

Indole-3-lactic acid

-

-

59

80

4

Indole-3-acrylic acid

33

29

15

24

64

5-Hydroxyindole-3-acetic acid

19

4

78

92

18

Indole-3-acetamide

-

-

41

36

34

Indole-3-ethylacetate

-

-

9

7

98

Indole-3-glyoxylamide

-

-

25

20

52

Isatin

75

27

42

40

78

Gramine

77

0

-

-

-

Tryptamine

77

0

47

2

0

Serotonin

65

0

62

8

0

Tryptophan

23

0

64

67

0

5-Hydroxytryptophan

14

0

-

-

-

aEluents: A = methyl acetate-isopropanol-25% ammonium hydroxide (9:7:4); B = chloroform-96% acetic acid (95: 5); C = water-methanol-acetic acid (59:40:1); D = 0.1M NH4OH in 40% methanol; E = n-hexane-ethyl acetate-acetic acid (72:27:1).

Source: Adapted from Stahl E and Kaldeuoey H (1951) Trace analysis of physiologically active, simple indole derivatives. Zeitschrift fur Physiologische Chemie 323: 183-191; Lepri L, Desideri PG and Heinler D (1983) High-performance thin-layer chromatography of indole derivatives on layers of Sil C18-50 untreated or impregnated with N-dodecylpyridinium chloride and on anmonium tungstophos-phate. Journalof Chromatography 260: 383-389.

aEluents: A = methyl acetate-isopropanol-25% ammonium hydroxide (9:7:4); B = chloroform-96% acetic acid (95: 5); C = water-methanol-acetic acid (59:40:1); D = 0.1M NH4OH in 40% methanol; E = n-hexane-ethyl acetate-acetic acid (72:27:1).

Source: Adapted from Stahl E and Kaldeuoey H (1951) Trace analysis of physiologically active, simple indole derivatives. Zeitschrift fur Physiologische Chemie 323: 183-191; Lepri L, Desideri PG and Heinler D (1983) High-performance thin-layer chromatography of indole derivatives on layers of Sil C18-50 untreated or impregnated with N-dodecylpyridinium chloride and on anmonium tungstophos-phate. Journalof Chromatography 260: 383-389.

N-nitrosamines are of interest. Silica gel, magnesium silicate, cyano- and diol-bonded silica have been used as stationary phases to separate these compounds. Alkyl- and arylnitrosamines can be separated on silica gel with w-hexane-diethyl ether-dichloro-methane (4:3:2 v/v) and cyclic nitrosamines with the same solvent mixture in a ratio of 5:7:10

The chromatographic behaviour of 26 compounds derived from 1,1-diphenylhydrazine was investigated by normal and reversed-phase chromato-graphy. The same techniques were used for the separation of several thiosemicarbazides and 1,2,4-triazoline-3-thiones on silica gel, alumina, and C18-modified silica-gel layers, and nonaqueous and aqueous eluents.

Amides are physiologically active compounds and a knowledge of possible interactions of the amide group and of different substituents under conditions close to those in physiological systems is highly important.

The separation of formanilide and ten para-substituted acetanilides was investigated on starch and cellulose layers, as an alternative to RP-18, using aqueous mobile phases with methanol, acetonitrile, acetone and 1-propanol as modifiers. Because RM values are related to the partitioning of solute molecules in the given system, they can be regarded as a measure of solute hydrophobicity.

The retention behaviour of three series of aromatic amides was investigated on silica gel with eight binary solvent mixtures (benzene-CHCl3 20 : 30 v/v; benzene-ethyl acetate 45 : 5 v/v; benzene-acetone 45 : 5 v/v; benzene-dioxane 45 : 5 v/v; heptane-ethyl acetate 40 : 10 v/v; carbon tetrachloride with ethyl acetate, acetone or dioxane in a 45 : 5 v/v ratio). The

Table 7 Retention data (hRF) of various heterocylic bases under different chromatographic conditions3

Compound

Silica gel G

RP-2

RP-8

RP-18

EluentA

Eluent B

Eluent C

Eluent D

Eluent E

Eluent E

Eluent E

Pyridine

29

54

20

-

70

55

56

2,2'-Bipyridyl

-

-

40

-

72

53

52

2,2',2"-Tripyridyl

-

-

35

-

66

46

41

2-Methylpyridine

30

54

-

-

-

-

-

3-Methylpyridine

35

55

-

-

-

-

-

4-Methylpyridine (y-picoline)

27

48

0

26

61

49

46

y,y'-Bipicolyl

-

-

24

20

60

49

43

2,4-Dimethylpyridine

28

49

-

-

-

-

-

2,6-Dimethlypyridine

36

59

-

-

-

-

-

2,4,6-Trimethylpyridine

26

51

-

-

-

-

-

2-Ethylpyridine

42

62

-

-

-

-

-

2-n-Propylpyridine

47

64

-

-

-

-

-

2-Hydroxypyridine

6

20

-

-

-

-

-

3-Hydroxypyridine

23

53

-

-

-

-

-

4-Hydroxypyridine

0

2

-

-

-

-

-

2-Aminopyridine

27

50

-

-

-

-

-

3-Aminopyridine

18

45

-

-

-

-

-

4-Aminopyridine

5

14

-

-

-

-

-

Pyridine-2-carbinol

18

45

-

-

-

-

-

Pyridine-3-carbinol

13

39

-

-

-

-

-

Pyridine-4-carbinol

4

39

-

-

-

-

-

Pyridine-2-aldehyde

51

67

-

-

-

-

-

Pyridine-3-aldehyde

33

58

-

-

-

-

-

Pyridine-4-aldehyde

36

56

-

-

-

-

-

Pyridine-2-carboxylic acid

2

4

-

-

-

-

-

Pyridine-3-carboxylic acid

6

6

-

-

-

-

-

Pyridine-4-carboxylic acid

5

5

-

-

-

-

-

Pyridine-2,6-dicarboxylic acid

3

5

-

-

-

-

-

2-Acetylpyridine

57

69

-

-

-

-

-

2-Benzoylpyridine

62

71

-

-

-

-

-

2-Fluoropyridine

62

69

-

-

-

-

-

2-Chloropyridine

61

70

-

-

-

-

-

2-Bromopyridine

63

72

-

-

-

-

-

3-Chloropyridine

56

65

-

-

-

-

-

3-Bromopyridine

57

67

-

-

-

-

-

3-Iodopyridine

58

70

-

-

-

-

-

Pyrazine

-

-

10

13

73

54

57

2,2'-Bipyrazyl

-

-

24

40

73

52

51

Quinoline

-

-

33

65

78

58

57

2,2'-Biquinolyl

-

-

70

67

74

53

45

6,6'-biquinolyl sulfide

-

-

5

36

73

36

31

8,8'-Biquinolyl sulfide

-

-

47

78

-

-

-

Quinoxaline

-

-

32

54

82

56

56

2,2'-Biquinoxalyl

-

-

54

83

70

43

32

Thieno[2,3-b; 4,5-b']biquinoxalyl

-

-

8

-

74

51

39

2-Methylquinoxaline

-

-

20

55

74

55

49

3,3'-Dimethyl-2,2'-biquinoxalyl

-

-

34

59

67

41

28

aEluents: A = ethylacetate; B = acetone; C = chloroform-ethanol-acetone (50 + 1+2); D = n-propanol-n-hexane (45 + 55); E = methanol-water (90 + 10).

Source: Adapted from Petrowitz HJ, Pastuska G and Wagner E (1965) Thin layer chromatography of some pyridines and quinolines. Chemiker-Zeitung 89: 7-12; Baranowski I and Swierczek S (1994) A study of the retention of azines and diazines in RPTLC with bonded alkyl stationary phases. Journal ofPlanar Chromatography - Modern TLC 5: 399-405.

anilides used were: N-substituted amides of 2,2- as substituent at the para position. Spots were ob-

dimethylpropanoic acid; N-substituted benzamides served under UV light at X = 254 nm.

and a-phenylacetamides, with -F, -Cl, -Br, -CF3, Dialkylaminoethyl dialkylamido fluorophosphates,

-CH3, -C2H5, -OCH3, -CN, -N(CH3 )2 or -N(C2H5)2 which exhibit choline esterase-inhibiting effects, were

Table 8 Retention data (hRF) of pyrimidine derivatives under different experimental conditions2

Pyrimidine derivative

opti-upc12

Sil C18-50 + 4%HDBS

EluentA

Eluent B

Eluent C

Eluent D

4-Amino-2-hydroxypyrimidine (cytosine)

54

42

7

24

3-Methylcytosine

53

19

8

25

5-Hydroxymethylcytosine

61

52

11

33

5-Methyl-2,4-dihydroxypyrimidine (thymine)

30

29

78

79

1-Methylthymine

13

19

71

73

2,4-Dihydroxypyrimidine (uracil)

55

51

86

86

4,6-Dihydroxypyrimidine

70

75

83

84

4,6-Dihydroxy-2-methylpyrimidine

63

66

72

74

5-Nitrouracil

57

52

84

87

5-Hydroxymethyluracil

63

60

87

90

6-Methyluracil

31

30

80

83

5,6-Dimethyluracil

14

19

67

76

5-Aminouracil

64

64

73

96

6-Aminouracil

54

58

84

85

Uracil-5-carboxylic acid

87

87

84

94

Uracil-6-carboxylic acid (orotic acid)

68

73

90

89

Orotic acid methyl ester

20

29

77

80

Uracil-6-acetic acid

68

71

90

90

6-Chlorouracil

34

56

69

78

5-Chlorouracil

41

47

68

77

5-Bromouracil

36

40

63

73

5-Iodouracil

27

31

57

66

6-Chloromethyluracil

29

34

62

71

5-Trifluoromethyluracil

40

47

60

66

6-Chloro-1,3-dimethyluracil

3

7

44

48

5-Hydroxyuracil (isobarbituric acid)

66

68

91

93

2-Thiouracil

48

56

70

77

4-Phenyl-2-thiouracil

3

17

23

28

5-Methyl-2-thiouracil

28

34

65

70

6-Hydroxy-2-thiouracil (2-thiobarbituric acid)

68

72

83

85

aEluents: A = 3% KCl in water; B = 0.5 M Na2CO3 in water; C = 1 M acetic acid in water-methanol (20%); D = 1 M acetic acid #0.5 M HCl in water-methanol (20%).

Source: Adapted from Lepri L, Coas V, Desideri PG and Zocchi A (1988) Planar chromatography of purines, pyrimidines and nucleosides on untreated and detergent-impregnated silanized silica plates. Journal of Planar Chromatography - Modern TLC 1: 317-324.

aEluents: A = 3% KCl in water; B = 0.5 M Na2CO3 in water; C = 1 M acetic acid in water-methanol (20%); D = 1 M acetic acid #0.5 M HCl in water-methanol (20%).

Source: Adapted from Lepri L, Coas V, Desideri PG and Zocchi A (1988) Planar chromatography of purines, pyrimidines and nucleosides on untreated and detergent-impregnated silanized silica plates. Journal of Planar Chromatography - Modern TLC 1: 317-324.

separated on silica-gel plates developed with meth-anol-pyridine-formamide, 80 + 15 + 5 (v/v) and detected with ninhydrin.

The lipophilicity of fused-ring nitrogen heterocyc-lic was determined by reversed-phase TLC on paraffin oil impregnated Silkoplat plates (Labor, MIM) using acetonitrile-aqueous solutions of different pH as eluents.

Lastly, amino-PAHs have been identified in sewage sludge after separation of the DMF extracts on a silicic acid column into three groups: carbazoles, aminoarenes and azaarenes. RP-18 F254 (Merck) layers were developed with acetonitrile#water (9 : 1 v/v), observed under UV illumination at X = 254 and 365 nm and then sprayed with specific reagents for detection of the amino group. Aminonaphthalene, aminoquinoline and/or aminoisoquinoline, amino-fluorene, aminoanthracene and/or aminophenanthrene, aminopyrene, aminophenylnaphthalene and amino-chrysene were found in the sludge.

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