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The application of chromatographic visualization test to determination of hydrophobic properties of aliphatic compounds
The Application of Chromatographic Visualization Test to Determination of Hydrophobic Properties of Aliphatic Compounds
INTRODUCTION The determination of hydrophobic properties of organic compounds is an important analytical problem. In this paper investigations are presented concerning the application of visualizing properties of new fuchsine for comparison of compounds showing strong and weak hydrophobic properties on thin layers. New fuchsine has been widely used in thin-layer chromatography of different classes of organic compounds and has proved to be a particularly useful visualizing agent with higher aliphatic acids (2), higher alcohols (3). amines, and esters (I). The following homologous groups of organic compounds were selected for the purpose of comparing the strongly and weakly hydrophobic substances: (a) fatty acids, the carbon atom numbers between C, and C2,,; (b) primary fatty alcohols, the carbon atom numbers between C, and Go; (c) primary aliphatic amines. the carbon atom numbers between C, and C2,,; (d) ethyl esters of fatty acids, the carbon atom numbers between C,,) and C,,,. EXPERIMENTAL All the determinations were performed with the help of ready-made chromatographic glass plates (E. Merck, Darmstadt), covered with a 0.25mm-thick Kieselgel 60 layer. These plates were activated at 110 2 5°C for 0.5 hr. Then 10 ~1 of the 0.25% benzene solution of each organic compound (22 pg of the developed substance) was placed at the starting points, 2 cm from the edge of the plate. As a mobile phase the chloroform-acetone systems were applied. The volume ratios of the components of the mobile phase are given in Table 1. The chromatograms were developed to a height of 12 cm and after careful evaporation of the solvents at 110 IT 5°C they were visualized with the 0.005% aqueous 121 0026-265X’78/0231-0121$01.00/0 Copyright 0 1978 by Academic Rew. Inc. All rights of reproductmn in any form reserved.
122
SLIWIOK
AND
MACIOSZCZYK
TABLE I THE VOLUME
Substances examined Fatty acids Fatty alcohols Primary aliphatic amines Ethyl esters of fatty acids
RAXOS
OF THE MOBILE
Mobile phase Chloroform-acetone Chloroform-acetone Chloroform-acetone Chloroform-acetone
PHASES APPLIED
Volume ratio of components in the mobile phase 96:4 9614 10:90 96:4
solution of new fuchsine. To visualize each chromatogram (20 x 20 cm), 15 ml of the new fuchsine solution was used. Photographs 1 and 2 show the chromatograms of fatty acids and alcohols, which represent the model forms of the chromatograms obtained also in other cases. Differences are observed in both the color and the surface areas of chromatographic spots of various compounds visualized with the 0.005% aqueous solution of new fuchsine. The dependence of the surface areas of these spots on the carbon atom numbers in a molecule is shown in Fig. 1. As shown in Fig. 1, with the carbon atom numbers above
PHOT. 1. The chromatogram of fatty acids visualized with the aqueous solution of new fuchsine. (1) caprylic acid; (2) capric acid; (3) lauric acid; (4) myristic acid; (5) palmitic acid; (6) stearic acid: 22 pg of each acid (10 ~1 of the 0.25% benzene solution) was placed on a chromatographic plate.
PHOT. 2. The chromatogram of fatty alcohols visualized with the aqueous solution of new fuchsine. (1) decyl alcohol: (2) dodecyl alcohol; (3) myristyl alcohol: (4) cetyl alcohol: (5) stearyl alcohol: (6) eicosyl alcohol: 22 pg of each alcohol 1011 of the 0.25% benzene solution was placed on a chromatographic plate.
HYDROPHOBIC
PROPERTIES
123
FIG. 1. The surface areas of chromatographic spots vs the carbon atoms number in a molecule of fatty acids, fatty alcohols, primary aliphatic amines and ethyl esters of fatty acids, developed in the amount of 22 pg (10 ~1 of 0.25% benzene solution).
16 the surface area of a chromatographic spot rapidly decreases. The results of the experiment prove that with the visualizing of chromatograms with the aqueous solution of new fuchsine two main processes take place: dissolving of the spot of the tested compound and absorption of the dye on the molecules of a developed compound (4, 5). On the basis of the experimental results dealing with visualizing of fatty acids, fatty alcohols, primary aliphatic amines, and esters on a thin layer, the conclusion can be drawn that the aqueous solution of new fuchsine can be used in chromatographic determination of hydrophobic properties of organic compounds. With the strongly hydrophobic substances the process of adsorption of a dye by the molecule of a developed sample predominates, and the dissolving of the substance plays a less important role. In this case the chromatographic spots are purple. With the weakly hydrophobic compounds the chromatographic spots obtained are usually white and dissolved, and have a purple framing. The process of dissolving the organic compound predominates, while the adsorption of a dye is rather insignificant. The a/m observations allow us to build the following scheme, describing the dependence between the color effects while using new fuchsine as a visualizing agent in thin-layer chromatography of organic compounds and the hydrophobic properties of these substances:
124
$LIWIOK
AND
MACIOSZCZYK
The method of comparing the hydrophobic properties of aliphatic compounds presented here is of high analytical importance, especially with chromatographic investigations and when selecting proper extracting systems. SUMMARY The experimental material obtained shows the possibility of using new fuchsine to compare the hydrophobic properties of aliphatic compounds. The test presented here seems to be of analytical importance, especially with chromatographic investigations and when selecting proper extracting systems.
REFERENCES I. Sliwiok, J., Barwniki fuksynowe jako nowe odczynniki wywo]ujace substancje organiczne w chromatogratii cienkowarstwowej, ,%A;. Nalrk. Polirrch. SlqsX., nr 290 (Cltrm. z. 54). Gliwice (1970) (Polish; “The Fuchsine Dyes as New Visualizing Agents in a Thin-Layer Chromatography of Organic Compounds”). 2. Sliwiok, J., The application of fuchsine dyes in the detection of higher fatty acids by thin-layer chromatography. Microchrm. J. 13, 108- 110 (1968). 3. Sliwiok, J., The Application of fuchsine dyes in the detection of higher fatty alcohols in thin-layer chromatography. Microchrm. J. 13, 11I- 112 (1968). 4. Sliwiok, J., and Kocjan, B., Investigation of the mechanism of visualization of fatty acids with new fuchsine in TLC by means of IR spectroscopy. Mic~roc~hrm..I. 20, 541-542 (1975). 5. Sliwiok, J.. and Kocjan, B., On the mechanism of detecting aliphatic monocarboxylic acids by means of new fuchsine in thin-layer chromatography. Microchrm. ./. 17, 273-275 (1972).
INTRODUCTION The determination of hydrophobic properties of organic compounds is an important analytical problem. In this paper investigations are presented concerning the application of visualizing properties of new fuchsine for comparison of compounds showing strong and weak hydrophobic properties on thin layers. New fuchsine has been widely used in thin-layer chromatography of different classes of organic compounds and has proved to be a particularly useful visualizing agent with higher aliphatic acids (2), higher alcohols (3). amines, and esters (I). The following homologous groups of organic compounds were selected for the purpose of comparing the strongly and weakly hydrophobic substances: (a) fatty acids, the carbon atom numbers between C, and C2,,; (b) primary fatty alcohols, the carbon atom numbers between C, and Go; (c) primary aliphatic amines. the carbon atom numbers between C, and C2,,; (d) ethyl esters of fatty acids, the carbon atom numbers between C,,) and C,,,. EXPERIMENTAL All the determinations were performed with the help of ready-made chromatographic glass plates (E. Merck, Darmstadt), covered with a 0.25mm-thick Kieselgel 60 layer. These plates were activated at 110 2 5°C for 0.5 hr. Then 10 ~1 of the 0.25% benzene solution of each organic compound (22 pg of the developed substance) was placed at the starting points, 2 cm from the edge of the plate. As a mobile phase the chloroform-acetone systems were applied. The volume ratios of the components of the mobile phase are given in Table 1. The chromatograms were developed to a height of 12 cm and after careful evaporation of the solvents at 110 IT 5°C they were visualized with the 0.005% aqueous 121 0026-265X’78/0231-0121$01.00/0 Copyright 0 1978 by Academic Rew. Inc. All rights of reproductmn in any form reserved.
122
SLIWIOK
AND
MACIOSZCZYK
TABLE I THE VOLUME
Substances examined Fatty acids Fatty alcohols Primary aliphatic amines Ethyl esters of fatty acids
RAXOS
OF THE MOBILE
Mobile phase Chloroform-acetone Chloroform-acetone Chloroform-acetone Chloroform-acetone
PHASES APPLIED
Volume ratio of components in the mobile phase 96:4 9614 10:90 96:4
solution of new fuchsine. To visualize each chromatogram (20 x 20 cm), 15 ml of the new fuchsine solution was used. Photographs 1 and 2 show the chromatograms of fatty acids and alcohols, which represent the model forms of the chromatograms obtained also in other cases. Differences are observed in both the color and the surface areas of chromatographic spots of various compounds visualized with the 0.005% aqueous solution of new fuchsine. The dependence of the surface areas of these spots on the carbon atom numbers in a molecule is shown in Fig. 1. As shown in Fig. 1, with the carbon atom numbers above
PHOT. 1. The chromatogram of fatty acids visualized with the aqueous solution of new fuchsine. (1) caprylic acid; (2) capric acid; (3) lauric acid; (4) myristic acid; (5) palmitic acid; (6) stearic acid: 22 pg of each acid (10 ~1 of the 0.25% benzene solution) was placed on a chromatographic plate.
PHOT. 2. The chromatogram of fatty alcohols visualized with the aqueous solution of new fuchsine. (1) decyl alcohol: (2) dodecyl alcohol; (3) myristyl alcohol: (4) cetyl alcohol: (5) stearyl alcohol: (6) eicosyl alcohol: 22 pg of each alcohol 1011 of the 0.25% benzene solution was placed on a chromatographic plate.
HYDROPHOBIC
PROPERTIES
123
FIG. 1. The surface areas of chromatographic spots vs the carbon atoms number in a molecule of fatty acids, fatty alcohols, primary aliphatic amines and ethyl esters of fatty acids, developed in the amount of 22 pg (10 ~1 of 0.25% benzene solution).
16 the surface area of a chromatographic spot rapidly decreases. The results of the experiment prove that with the visualizing of chromatograms with the aqueous solution of new fuchsine two main processes take place: dissolving of the spot of the tested compound and absorption of the dye on the molecules of a developed compound (4, 5). On the basis of the experimental results dealing with visualizing of fatty acids, fatty alcohols, primary aliphatic amines, and esters on a thin layer, the conclusion can be drawn that the aqueous solution of new fuchsine can be used in chromatographic determination of hydrophobic properties of organic compounds. With the strongly hydrophobic substances the process of adsorption of a dye by the molecule of a developed sample predominates, and the dissolving of the substance plays a less important role. In this case the chromatographic spots are purple. With the weakly hydrophobic compounds the chromatographic spots obtained are usually white and dissolved, and have a purple framing. The process of dissolving the organic compound predominates, while the adsorption of a dye is rather insignificant. The a/m observations allow us to build the following scheme, describing the dependence between the color effects while using new fuchsine as a visualizing agent in thin-layer chromatography of organic compounds and the hydrophobic properties of these substances:
124
$LIWIOK
AND
MACIOSZCZYK
The method of comparing the hydrophobic properties of aliphatic compounds presented here is of high analytical importance, especially with chromatographic investigations and when selecting proper extracting systems. SUMMARY The experimental material obtained shows the possibility of using new fuchsine to compare the hydrophobic properties of aliphatic compounds. The test presented here seems to be of analytical importance, especially with chromatographic investigations and when selecting proper extracting systems.
REFERENCES I. Sliwiok, J., Barwniki fuksynowe jako nowe odczynniki wywo]ujace substancje organiczne w chromatogratii cienkowarstwowej, ,%A;. Nalrk. Polirrch. SlqsX., nr 290 (Cltrm. z. 54). Gliwice (1970) (Polish; “The Fuchsine Dyes as New Visualizing Agents in a Thin-Layer Chromatography of Organic Compounds”). 2. Sliwiok, J., The application of fuchsine dyes in the detection of higher fatty acids by thin-layer chromatography. Microchrm. J. 13, 108- 110 (1968). 3. Sliwiok, J., The Application of fuchsine dyes in the detection of higher fatty alcohols in thin-layer chromatography. Microchrm. J. 13, 11I- 112 (1968). 4. Sliwiok, J., and Kocjan, B., Investigation of the mechanism of visualization of fatty acids with new fuchsine in TLC by means of IR spectroscopy. Mic~roc~hrm..I. 20, 541-542 (1975). 5. Sliwiok, J.. and Kocjan, B., On the mechanism of detecting aliphatic monocarboxylic acids by means of new fuchsine in thin-layer chromatography. Microchrm. ./. 17, 273-275 (1972).