the microscale laboratory vanillyl-OH).GC-MS: 7.79 min; no M+ ion was observed under our conditions. Acknowledgment The Experimental Techniques 1Class of Winter 1992 is acknowledged. Literature Cited 1. Gmas, M A n n u o l Rep.Med Chem. 1990,25,32&231. 2. Remos T o m b G.M.: Bellus, D.Anpelu Chem. Inl. Ed. E n d 1993.30, 1193-1215. 5. Csuk,R.; Glanzer, B. I. Chem Re". 1991,31,41C97. 6 . Nimitz J. S. Er~rrimpnfsin O w n i c Chemistry : Rentice-Hall: Endewood Clifi,
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7 . Banesbv,A.R.:Stauton, J.;Wfitshire,H.R.J C S . Perkin 1 1 W h 11561162
11. Ward, D.; Rhee, C. K lbhohedmn Lett 1991,32,7165-7166. 12. Yamaguehi, S. hkymmtric Synthosla;Mamison, J. D., Ed.:Academic Reas, Ine.: New York. 1983: Val. 1,pp 125-152.
Acknowledgment Support from NSF-ILIP and NSF-Young Scholars grants (USE-8851427 and RCD-9055029) are gratefully acknowledged. Literature Cited 1. Lehman, J. W. Opmtioionol O~gonicChemlafry;A l l p andBsmn: Bostrm, 1981. 2. Ranman, P J Chem. Edrrc. 1985,62,640. 3. Wiltiaman, K L. Mocmsmlaond Microscale OgonicExprimntn, D.C. Heath: hington, MA, 1989. 4. Fieser, L.F.:Williamson, K L. organic Experiments, 6thed.;D.C.Heath: Lexingtrm, M A 1987 5 . McKone, H . T . J Chem.Edue. 1973,56,6'76.
6 . Tantillo, M.J . Chem. Edue. IS-, 65,254. 7 . p s n a , D. L.; L-pman, G. M.; and k e , 0 . S. Infmdudion to Organic Iabomtory Tmhniguss; Q.B. Saunders Ca.:Philadslphia,PA, 1976. 8 . Sadier, G.;Davis, J.; Derman, D.J. FoodSci. 1990, hi, 1460.
Separation of Methylene Blue and Fluorescein: A Microscale Undergraduate Experiment in Column Chromatography
The Microscale Separation of Lycopene and p-Carotene from Tomato Paste James Goodrich. Chris Parker. and Ruff Phelos Lou~s~ana State ~ n ~ ; e r sIn~~hreve~orl t~ Shrevepoll. LA 71 115
Experiments for the isolation and analysis of carotenoids from carrot andlor tomato pastes are popular in instructional chemistry laboratories (Id)but oRen require 3.5-5 h. We have developed an experiment for the isolation and separation of p-carotene and lycopene from tomato paste on the microscale level that affords the isolation of two compounds from a single common foodstuff and requires less than 3 h to complete. The compounds can be rapidly analyzed. It provides experience with column chromatography (for separation) and UV-VIS spectrometry (for analysis). The column is prepared with insertion of a glass plug into the tip of a 5.75 in. Pasteur pipet. Alayer of alumina (80-200 mesh) (dry-packed or slurried in 99:l petroleum ether-acetone) ( 6 ) is added to a height of -8 an.An optional layer of sand (3 mm) may be added to complete the column. The use of approximately 3 g of tomato paste provides enough lycopene extract for spectral analysis. The tomato paste is extracted with petroleum ethedacetone (50:50) (3 x 10 mL) and filtered. The combined extracts are washed with saturated aqueous sodium chloride (25 mL), 10% aqueous potassium carbonate (25 mL), water (25 mL), and dried with sodium sulfate. After concentrating the volume in vacuo to several milliliters, it is placed on the column for separation. The C)-carotene1s eluted with petroleum ether acetone (99:11andthe lycopene ~selutedwitha 9W10 mlxture. Positive oressure noolied with a ruhber bulh will soeedelution but can cause band spreading, particularly with the lycopene. Eluants were analyzed spectrophotometrically using (90:lO) petroleum ether-acetone as a reference. The characteristic absomtions of lvco~enewere observed near 504, 473, and 446 i m ; whereas, 'p-carotene occurs at 476 and 450 nm (7).Quantitative vields can be calculated using the molar absorptivity at 470 nm (1.85 x 105) (8). A158
Journal of Chemical Education
Paris ~voronos'and Edward Sarlo Queensborough College of the City University of New Yorh Bayside. NY 11364
Often column chromatography (CC) is used to separate mixtures and/ or purify compounds. The procedure is so commonly employed that the technique usually is included in the first semester of an oreanic chemistrv course. However, many of the procedures-found in laborkary manuals are both tedious and comdicated for students in a beeinning organic labllratory c k w ctable,. We offer a simple microscale CC experiment for separatin~and isolating the componentsofa 5Q50 methylme hlue-fluorescein mixture that uses a disp~~sahle pipet, two nontoxic solvents (water and ethanol.. and aluminn and that allows the student to see the clean separation of the blue and yellow colored nontoxic dves. The exneriment is suitable for laree " laboratom sections because it requires inexpensive and easily disposable eaui~mentand cheniicals. In addition. the results can be qu&&ied by measuring the collected ðylene blue spectrophotometrically.
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Procedure Asmall uniform plug of glass wool is placed into the bottom of a disposable pipet with the aid of a thin glass rod, wire or "unfolded" paper clip. Alumina is added until it forms a 3-in. high column. The pipet is filled with 95% ethanol and, with a finger placed on top, inverted and shaken vigorously to ensure that the alumina is evenly suspended in the solvent and that all air bubbles are eliminated. The pipet is turned right-side up and secured over a test tube using a clamped, one-hole rubber stopper. Traces of alumina adhering to the glass may be washed down with a few drops of ethanol. The solvent level must be kept above the top of the column of alumina throughout the experiment by continuously adding ethanol. Two to three drops of a green dye solution composed of 5%methylene blue and 5% fluorescein in 95% ethanol is added directly to the column, which is then eluted using 95% ethanol. The first component, methylene blue, is collected in a test tube placed under the tip of the pipet. When the eluate is no
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