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α-Al2O3 as an adsorbent in thin-layer chromatography
MICROCHEMICAL
a-AK&
JOURNAL
17, 632-637
as an Adsorbent
(1972)
in Thin-Layer
Chromatography
B. KORCZAK, J. W~GRZYNEK, H. HABLA AND J. SLIVJIOK Institute of Chemistry, Silesian University, 9, Szkotna Str., Katowice, Poland Received
J~tly 12, 1972
INTRODUCTION
Among the several important factors which determine the chromatographic separation of tested components, the kind of adsorbent has the principal significance. Besides silica gel and cellulose, aluminum dioxide is one of the most often used adsorbents in the thin-layer c~omatograpby. Some efforts were made to examine the usability of aluminum dioxide for TLC purposes (3). In the present paper we show the results of our investigations dealing with the effect of cr-Al&, on the chromatographic separation of selected organic compounds. EXPERIMENTAL
METHODS
~uminum hydroxide (USSR) was sieved to unify the diameter of granules. The 0.5 kg samples were placed in evaporating dishes and roasted in the muffle bake to get some polymorphous forms. The temperatures of roasting were 200, 500, 700, 1000 and 1250°C and the time of roasting was 5 hr in every case. Our substrate and roasted samples were examined by means of X-ray radiography. Rentgeno~~s were done with the help of Rigaka-Denki Japan diffractometer, using Co& radiation. Owing to our phase identification (I) by the X-ray radiographic method, the structure of our substrate was defined as y-Al,O,s 3H,O (Fig. 1). The samples roasted at 125O’C showed the 1y-Al~0~structure (Fig. 2). In Fig. 3 one observes the X-ray photograph of the obtained W-A&~, mixed with 2.5% of gypsum. The complementary measurements of the specific surfaces were done by means of BET method, the adsorption gas being nitrogen educed from natrium nitride, The working conditions were as follows: pressure lo-4 mm Hg, temperature gO”C, time 2 hr. The adsorption surface of nitrogen molecule was accepted as 16.2 AZ. Adsorption was run at the temperature of liquid nitrogen. The obtained results are shown in Table 1. On the base of the X-ray radiographic results one appIied CU-Al,O, received by roasting of AI( at 1250°C (identified as r-A&O,* 632 Copyright @ 1972 by Academic Press, Inc. All rights of reproduction in any form reserved.
633
(Y-AL~O~AS ADSORBENT IN TLC
FIG. 1. Difraction
pattern of a substrate y-Al,O,*3H,O;
CoKa
radiation.
3H,O) for the chromatographic purposes. The chromatographic test mixture was composed of butter yellow, Sudan G and indophenol. The comparative sample was AlzO, produced by “Woelem” (West Germany). Aluminum dioxide without any binding material cannot be used as a chromatographic adsorbent and therefore 2.5% gypsum must be added. The coated plates were dried at room temperature for 24 hr and then the test dyes were placed on their start-points. Our purpose was to determine the chromatographic usability of PALO,. Therefore the chromatographic separation was defined by the following coefficients : 1. RI values;
L 80
li
70
I-I.I,Yu.
Fm. 2. Diffraction
pattern of wAl,O,;
Co&
radiation.
634
KORCZAK ET AL.
FIG. 3. Diffraction radiation.
pattern of a mixture of wAl,O,
plus 2.5% gypsum;
Cdu
2. “geometric index” values, I, (2) ; 3. number of theoretical plates, Lpt (4) ; 4. time of migration of the mobile phase t. The fust stage of our chromatographic experiment was to find the proper mobile phase. These inquiries were conducted with the original (i.e., Woelem) A1,03. Among the 25 examined phases the following compositions were the best: heptane-benzene (7 : 3 ) , pentane-benzene (7 : 3)) pentanebenzene (8:2), cyclohexane-benzene (7:3), hexane-benzene (7:3), hexanebenzene (8 : 2) octane-benzene (7 : 3). Therefore determination of chromatographic usability of ar-Al,Oj was conducted with the help of those mixtures. The chromatographic separation of the discussed dyes on the firm-made Al’,O, and ~cu-Al,Os,using mobile phase composed of heptanebenzene (7: 3, v/v) is shown in Figs. 4 and 5 as an example. The obtained results are shown in Table 2. On the basis of the performed experiments one can state that the more satisfactory separation of butter yellow, Sudan G and indophenol was obtained on cu-Al,O,. The chromatographic spots of the analyzed dyes are much better separated in the case of that adsorbent than on Al,Os produced by Woelem. The same observation refers to the number of theoretical plates. For (Y-AI~O~one got much higher values TABLE THE
SPECIFIC
SURFACE
VALUFS
1
OF THE EXAMINED
ADSORBENTS
Symbol
Sample
Specific surface (m2/g)
A
A1203 (“Woelem”)
346.4
B
c+A1203(got at 1250°C)
47.9
B’
a-A1108 (got at 1250°C f 2.5% gyps)
77.2
~-AL~O~
AS ADSORBENT IN TLC
635
4
FIG. 4. Chromatogram of the separated dyes; mobile phase: heptane-benzene (7 : 3, v/v) ; adsorbent: AZ,O, Woelem.
of Lpt. The comparison of the times of mobile phase migration shows that they are 8-10 times shorter with a-A1203 than with the Woelem product. Only the I, values are more satisfactory with Woelem A&,0,. 5
0 0 0
-” FIG. 5. Chromatogram of the separated dyes; mobile phase: heptane-benzene (7:3, v/v); adsorbent: a-A120,.
(7 : 3)
Octane-benzene (7:3)
Hexane-benzene (8 : 2)
Cyclohexane-benzene (7:3) Hexane-benzene (7: 3)
Pentane-benzene (S: 2)
OF
---
MOBILE
~
.---__-
Rf values
ADSORBWJTAND
ON -rtt~ R,, Lpt AND
I,
0.71 2.85 1.00 1.66 0.64 3.40 1.00 1.54 1.37 3.00 1.55 2.50 1.00 2.18
1.00 1.71 1.00 1.81 0.99 2.75 1.00 1.80 1.00 1.83 1.00 4.33 1.00 2‘20
1.71 3.57 1.05 1.90 0.99 3.50 1.00 2.00 1.00 3.00 1.00 4.46 1.00 3.00
Butter Indoyellow Sudan G phenol
Geometrical index values
PHASE
Butter IndoAdsorbent yellow Sudan G phenol -~ ---~ .-~ A 0.26 0.08 0.03 B’ 0.86 0.55 0.42 A 0.40 0.14 0.07 B’ 0.93 0.78 0.63 A 0.57 0.36 0.32 B’ 0.80 0.44 0.25 A 0.48 0.14 0.07 B’ 0.88 0.69 0.58 A 0.34 0. IO 0.05 8’ 0.90 0.60 0.45 A 0.25 0.06 0.03 B’ 0.76 0.41 0.25 A 0.14 0.03 0.01 B’ 0.71 0.38 0.23
INFLUWZE
Pentane -Benzene (7 : 3)
Hcp~e-inane
Mobile phase
THI!
TABLE 2
-
3600 338 3003 305 3600 174 3136 55 2043
1632 55 3944 64 4409 28 2496 10 739
576 21 3225 16 2502 6 871 2 416
Butter Indoyellow Sudan G phenol -. ..f89 56 I6 8464 4356 2342 494 134 37 5184 3648 2368 705 686 532
I~
OP THE EXAMND
No. of theor. plates values
VALL’ES
92 IO.5
234 21 172 11 _-
75 13 1.5 12 -
Time of migration of the mobile phase 15 cm high _ Onin)
DYFS
F
z
E
6 R
a-AL~O:~
AS ADSORBENT
IN TLC
637
In the case of the latter one chromatographic spots are very symmetrical and the I, values are nearly 1. Summing up our discussion we emphasize again that aluminum dioxide prepared in the described way showed several advantages of the proper adsorbent for TLC purposes. SUMMARY The laboratory-made a-A&O, was applied in TLC as an adsorbent. The usability of it was determined by the separation of a mixture of test-dyes (butter yellow, Sudan G and indophenol) and calculation of the following coefficients: Rf, Lpt, I, and t. The comparison was made conducting the same experiments with Al,O, produced by Woelem. It was stated that the self-made adsorbent permitted satisfactory results to be obtained. 1. Brown, G., “The X-Ray Identification
and Crystal Structures of Clay Minerals.” Mineralogical Sot., London, 1961. 2. Gregorowicz, Z., Jalowiecki, H., and Bobrowska, E., The geometric index in thin-layer chromatography. MicEochem. J., 16, 241-244 (1971). 3. Halpaap, H., and Reich, W., Chromatographische Eigenschaften von Aluminiumoxiden unterschiedlicher Struktur, J. Chromatogr. 33, 70-79 (1968). 4. Kwapniewski, Z., Mastalerz, .I., and Gliwifiski, K., Rozdzial chromatograficzny, interpretowany wartoiciami ARf i liczbq p6lek teoretycznych w metodzie chromatografii bibulowej. (transl. “The chromatographic separation in paper chromatography interpreted with the AR, and number of theoretical plates values)“. Zesz. Nauk. WSP w Katowicach, Sekcja Chem. 7, 63-65 (1967).
a-AK&
JOURNAL
17, 632-637
as an Adsorbent
(1972)
in Thin-Layer
Chromatography
B. KORCZAK, J. W~GRZYNEK, H. HABLA AND J. SLIVJIOK Institute of Chemistry, Silesian University, 9, Szkotna Str., Katowice, Poland Received
J~tly 12, 1972
INTRODUCTION
Among the several important factors which determine the chromatographic separation of tested components, the kind of adsorbent has the principal significance. Besides silica gel and cellulose, aluminum dioxide is one of the most often used adsorbents in the thin-layer c~omatograpby. Some efforts were made to examine the usability of aluminum dioxide for TLC purposes (3). In the present paper we show the results of our investigations dealing with the effect of cr-Al&, on the chromatographic separation of selected organic compounds. EXPERIMENTAL
METHODS
~uminum hydroxide (USSR) was sieved to unify the diameter of granules. The 0.5 kg samples were placed in evaporating dishes and roasted in the muffle bake to get some polymorphous forms. The temperatures of roasting were 200, 500, 700, 1000 and 1250°C and the time of roasting was 5 hr in every case. Our substrate and roasted samples were examined by means of X-ray radiography. Rentgeno~~s were done with the help of Rigaka-Denki Japan diffractometer, using Co& radiation. Owing to our phase identification (I) by the X-ray radiographic method, the structure of our substrate was defined as y-Al,O,s 3H,O (Fig. 1). The samples roasted at 125O’C showed the 1y-Al~0~structure (Fig. 2). In Fig. 3 one observes the X-ray photograph of the obtained W-A&~, mixed with 2.5% of gypsum. The complementary measurements of the specific surfaces were done by means of BET method, the adsorption gas being nitrogen educed from natrium nitride, The working conditions were as follows: pressure lo-4 mm Hg, temperature gO”C, time 2 hr. The adsorption surface of nitrogen molecule was accepted as 16.2 AZ. Adsorption was run at the temperature of liquid nitrogen. The obtained results are shown in Table 1. On the base of the X-ray radiographic results one appIied CU-Al,O, received by roasting of AI( at 1250°C (identified as r-A&O,* 632 Copyright @ 1972 by Academic Press, Inc. All rights of reproduction in any form reserved.
633
(Y-AL~O~AS ADSORBENT IN TLC
FIG. 1. Difraction
pattern of a substrate y-Al,O,*3H,O;
CoKa
radiation.
3H,O) for the chromatographic purposes. The chromatographic test mixture was composed of butter yellow, Sudan G and indophenol. The comparative sample was AlzO, produced by “Woelem” (West Germany). Aluminum dioxide without any binding material cannot be used as a chromatographic adsorbent and therefore 2.5% gypsum must be added. The coated plates were dried at room temperature for 24 hr and then the test dyes were placed on their start-points. Our purpose was to determine the chromatographic usability of PALO,. Therefore the chromatographic separation was defined by the following coefficients : 1. RI values;
L 80
li
70
I-I.I,Yu.
Fm. 2. Diffraction
pattern of wAl,O,;
Co&
radiation.
634
KORCZAK ET AL.
FIG. 3. Diffraction radiation.
pattern of a mixture of wAl,O,
plus 2.5% gypsum;
Cdu
2. “geometric index” values, I, (2) ; 3. number of theoretical plates, Lpt (4) ; 4. time of migration of the mobile phase t. The fust stage of our chromatographic experiment was to find the proper mobile phase. These inquiries were conducted with the original (i.e., Woelem) A1,03. Among the 25 examined phases the following compositions were the best: heptane-benzene (7 : 3 ) , pentane-benzene (7 : 3)) pentanebenzene (8:2), cyclohexane-benzene (7:3), hexane-benzene (7:3), hexanebenzene (8 : 2) octane-benzene (7 : 3). Therefore determination of chromatographic usability of ar-Al,Oj was conducted with the help of those mixtures. The chromatographic separation of the discussed dyes on the firm-made Al’,O, and ~cu-Al,Os,using mobile phase composed of heptanebenzene (7: 3, v/v) is shown in Figs. 4 and 5 as an example. The obtained results are shown in Table 2. On the basis of the performed experiments one can state that the more satisfactory separation of butter yellow, Sudan G and indophenol was obtained on cu-Al,O,. The chromatographic spots of the analyzed dyes are much better separated in the case of that adsorbent than on Al,Os produced by Woelem. The same observation refers to the number of theoretical plates. For (Y-AI~O~one got much higher values TABLE THE
SPECIFIC
SURFACE
VALUFS
1
OF THE EXAMINED
ADSORBENTS
Symbol
Sample
Specific surface (m2/g)
A
A1203 (“Woelem”)
346.4
B
c+A1203(got at 1250°C)
47.9
B’
a-A1108 (got at 1250°C f 2.5% gyps)
77.2
~-AL~O~
AS ADSORBENT IN TLC
635
4
FIG. 4. Chromatogram of the separated dyes; mobile phase: heptane-benzene (7 : 3, v/v) ; adsorbent: AZ,O, Woelem.
of Lpt. The comparison of the times of mobile phase migration shows that they are 8-10 times shorter with a-A1203 than with the Woelem product. Only the I, values are more satisfactory with Woelem A&,0,. 5
0 0 0
-” FIG. 5. Chromatogram of the separated dyes; mobile phase: heptane-benzene (7:3, v/v); adsorbent: a-A120,.
(7 : 3)
Octane-benzene (7:3)
Hexane-benzene (8 : 2)
Cyclohexane-benzene (7:3) Hexane-benzene (7: 3)
Pentane-benzene (S: 2)
OF
---
MOBILE
~
.---__-
Rf values
ADSORBWJTAND
ON -rtt~ R,, Lpt AND
I,
0.71 2.85 1.00 1.66 0.64 3.40 1.00 1.54 1.37 3.00 1.55 2.50 1.00 2.18
1.00 1.71 1.00 1.81 0.99 2.75 1.00 1.80 1.00 1.83 1.00 4.33 1.00 2‘20
1.71 3.57 1.05 1.90 0.99 3.50 1.00 2.00 1.00 3.00 1.00 4.46 1.00 3.00
Butter Indoyellow Sudan G phenol
Geometrical index values
PHASE
Butter IndoAdsorbent yellow Sudan G phenol -~ ---~ .-~ A 0.26 0.08 0.03 B’ 0.86 0.55 0.42 A 0.40 0.14 0.07 B’ 0.93 0.78 0.63 A 0.57 0.36 0.32 B’ 0.80 0.44 0.25 A 0.48 0.14 0.07 B’ 0.88 0.69 0.58 A 0.34 0. IO 0.05 8’ 0.90 0.60 0.45 A 0.25 0.06 0.03 B’ 0.76 0.41 0.25 A 0.14 0.03 0.01 B’ 0.71 0.38 0.23
INFLUWZE
Pentane -Benzene (7 : 3)
Hcp~e-inane
Mobile phase
THI!
TABLE 2
-
3600 338 3003 305 3600 174 3136 55 2043
1632 55 3944 64 4409 28 2496 10 739
576 21 3225 16 2502 6 871 2 416
Butter Indoyellow Sudan G phenol -. ..f89 56 I6 8464 4356 2342 494 134 37 5184 3648 2368 705 686 532
I~
OP THE EXAMND
No. of theor. plates values
VALL’ES
92 IO.5
234 21 172 11 _-
75 13 1.5 12 -
Time of migration of the mobile phase 15 cm high _ Onin)
DYFS
F
z
E
6 R
a-AL~O:~
AS ADSORBENT
IN TLC
637
In the case of the latter one chromatographic spots are very symmetrical and the I, values are nearly 1. Summing up our discussion we emphasize again that aluminum dioxide prepared in the described way showed several advantages of the proper adsorbent for TLC purposes. SUMMARY The laboratory-made a-A&O, was applied in TLC as an adsorbent. The usability of it was determined by the separation of a mixture of test-dyes (butter yellow, Sudan G and indophenol) and calculation of the following coefficients: Rf, Lpt, I, and t. The comparison was made conducting the same experiments with Al,O, produced by Woelem. It was stated that the self-made adsorbent permitted satisfactory results to be obtained. 1. Brown, G., “The X-Ray Identification
and Crystal Structures of Clay Minerals.” Mineralogical Sot., London, 1961. 2. Gregorowicz, Z., Jalowiecki, H., and Bobrowska, E., The geometric index in thin-layer chromatography. MicEochem. J., 16, 241-244 (1971). 3. Halpaap, H., and Reich, W., Chromatographische Eigenschaften von Aluminiumoxiden unterschiedlicher Struktur, J. Chromatogr. 33, 70-79 (1968). 4. Kwapniewski, Z., Mastalerz, .I., and Gliwifiski, K., Rozdzial chromatograficzny, interpretowany wartoiciami ARf i liczbq p6lek teoretycznych w metodzie chromatografii bibulowej. (transl. “The chromatographic separation in paper chromatography interpreted with the AR, and number of theoretical plates values)“. Zesz. Nauk. WSP w Katowicach, Sekcja Chem. 7, 63-65 (1967).