Alumina for chromatography

Alumina for chromatography. The equivalent of acid-washed material can be prepared by stirring ordinary alumina with ethyl acetate, letting the mixture stand for 1-2 days, filtering, and drying at 80°. Alumina washed with 5-10% acetic acid in water is suitable for adsorption of base-sensitive substances (enol acetates, ot, -unsaturated acetates). For chromatography of /3,y-unsaturated ketones without isomerization, the alumina can be washed with warm aqueous alkali, then warm acetic acid followed by water (to neutrality) it is then reactivated at 200° for 30 hrs. K. R. Farrar, J. C. Hamlet, H. B. Henbest and E. R. H. Jones,/. Chem. Sac., 2657 (1952) R. B. Clayton, A. Crawshaw, H. B. Henbest, E. R. H. Jones, B. J. Lovell, and G. W. Wood, ibW., 2009 (1953)... 

Non-activated y grade alumina for chromatography is sufficiently basic to promote hydrogen abstraction to rather acidic carbon acids (pKa<15) [19]. In such a way, numerous anionic condensations are described, for example, an aldolization [Eq. (10)] [20] leading to aurone, a basic compound in flower pigmentation, a Knoevenhagel reaction [Eq. (11) ] [21 ], or a case of a Henry reaction [Eq. (12)] [22]. 

Alumina for chromatography comes in three forms (basic, pH 10 neutral, pH 7 acidic, pH 4) whose activity can be varied quantitatively by the addition of measured amounts of water. The most active form of alumina ( activity I or Brockmann Number I ) is too active for normal applications and is rarely used. Activity III alumina is best for most applications, and it should be used when alumina is first being tested as an adsorbent. If it is found that the compounds are adsorbed too tenaciously or an excessive amount of tailing of components occurs after the peaks, a less active grade of alumina is used. If the compounds elute rapidly and are insufficiently separated, a more active grade should be investigated. The activity can be checked with a special series of dyes.f... 

Activated neutral alumina (for chromatography) Soxhlet apparatus... 

Mottier [11] has developed a TLC-variant. He activates Merck alumina for chromatography (No. 1097) by heating 45 min at 300—500° C and applies it to the plate without a binder. He chromatographs the sodium salts instead of the free amino acids and his approach differs from that of Stahl in other respects also. 

Physical properties of TLC alumina are somewhat similar to TLC silica in terms of particle size, surface area, and average pore diameter. Aluminas for chromatography have surface areas between 50 and 350 m /g, average pore diam-eters..between 20 and 150 A, and specific pore volumes between 0.1 and 0.4 ml/ g (Rossler, 1969 Hahn-Deinstrop, 1992 Robards et al., 1994). 

If the solution (after dissolution of the substance) is colored or if it contains impurities, it may be useful to use certain adsorbents, i.e., the solutions in polar solvents are briefly boiled with a small amount of charcoal, those ill nonpolar solvents are shaken (without boiling) with alumina (the powder remaining after sieving alumina for chromatography may be used). 

Alumina for chromatography (Wako Pure Chemicals Co. Ltd.), sieved between 200 to 300 mesh, was washed 5 times with tap water and 5 times with distilled water (adjusting pH of the supernatant to 4.3—4.7 with HCl), dried at 110 °C, and calcinated for 3—4 h over a Teclu burner. The alumina was then rinsed twice with 0.48 M K2HPO4, pH 9.0—9.2, and left overnight. The precipitate suspended in the buffer was transferred into a column. 

Liquid chromatography is a separation technique based on the selective adsorption on a solid, siiica or alumina for example, or a mixture of the two, of the different components of a liquid mixture. 

Aluminum compounds, particularly the hydroxides and oxides are very versatile. Properties range from a hardness iadicative of sapphire and comndum to a softness similar to that of talc [14807-96-6] and from iuertness to marked reactivity. Aluminas that flow and filter like sand may be used for chromatography (qv) others are viscous, thick, unfilterable, and even thixotropic (1). 

Alumina Number 1076, aktiv basisch, for chromatography (E. Merck, Darmstadt) was usually employed. Occasionally, when alumina Number 1077, aktiv neutral, from the same company, was used, a longer reaction time was required (compare Note 15). 

Table 3.3 lists bulk aluminas for the preparation of homemade PLC plates for straight phase chromatography. 

The first thing you need is an adsorbant, a porous material that can suck up liquids and solutions. Paper, silica gel, alumina (ultrafine aluminum oxide), corn starch and kitty litter (unused) are all fine adsorbants. Only the first three are used for chromatography. You may or may not need a solid support with these. Paper hangs together, is fairly stiff, and can stand up by itself. Silica gel, alumina, corn starch, and kitty litter are more or less powders and will need a solid support to hold them. 

Merck silica gel (0.05-0.2 mm., 70—325 mesh ASTM) was used. The filtration column (1.4 x 7 cm.) is prepared in the same way as one used for chromatography, only one (200-ml.) fraction is collected. Use of alumina for the filtration gives variable results. 

The inorganic contribution, Kio, for chromatography-grade silica was found to depend weakly on K (log Kg 0.16 KQW) (55), which is consistent with the results for silica and alumina obtained by Schwarzenbach and Westall (56). 

The nature of the surface of alumina is important in its application as an adsorbent for chromatography. This subject is covered by special literature. Inorganic ions can be separated on alumina as well as on silica (241). Anions are adsorbed together with bivalent cations, but not together with univalent cations indicating, again, equimolecular... 

A Perkin-Elmer Model 21 infrared spectrophotometer was used to detect and to estimate the hydroxylic and carbonyl functions in the oxidized product mixtures. The organic hydroperoxide and peroxide functional groups in the product mixtures were determined by an iodine liberation and titration procedure (11). In order to get reproducible results, it is necessary to pretreat the olefins with about 10 weight % activated silica or alumina for several hours with agitation to remove adventitious peroxides and impurities. Sodium bisulfite solution rapidly destroys hydroperoxides but does not destroy peroxides completely. The hydroperoxides and peroxides decomposed extensively during attempted distillation at about 1 mm. of Hg partial vacuum. We had some success in concentration by liquid chromatography over silica gel the unconverted olefins are eluted with n-hexanes, and a hydroperoxide-peroxide... 

Method A. To an alumina (Harshaw Chemical Co. 80 mesh alumina, slightly basic type used for chromatography is dried at 160°-170°C for 5 days before use) column (1.7 x 11 cm) is added a solution of 0.77 gm of l-(p-bi-phenyl)-3-phenyl-l-propyne in n-pentane. After 45 min the product is eluted with -pentane and concentrated at room temperature using a nitrogen atmosphere (with a water aspirator) to afford 0.53 gm (69%), m.p. 84.8°-86.4°C. 

Attempts have been made to solve the problem of selective substitution in sucrose octaacetate. Adsorption of the latter onto alumina for 46 hours gave a complex mixture from which, after extensive chromatography, were isolated the 2,3,4,6,l, 3, 4 -heptaacetate in 9% yield,11 the 2,3,6,l, 3, 4, 6 -heptaacetate in 2.7% yield,117 and the 2,3,4,6,1, 3, 6 -heptaacetate in 6% yield.117 Although selective deacylation of the octaacetate apparently occurs at secondary positions, as well as at 0-6, it is likely that heptaacetates containing 4- and 4 -OH groups... 

Thirteen different supports have been used commercial silica (Si02) from Merck (Kieselgel 60, 70-230 mesh) a commercial alumina (AI2O3) (aluminum oxide active acidic for chromatography) from Merck three AIPO4 PrePar eti according to... 

The choice of the type of aluminum oxide is important, and it is suggested that it have a pH near 7.0-8.0 with an activity grade of 1. If too acidic or basic, this adsorbent can have deleterious effects on certain phospholipids. Aluminum oxide (alumina) suitable for chromatography is available from commercial biochemical supply houses. 

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