Straight-phase HPLC

BASIC PROTOCOL 2 HPLC ANALYSIS OF REGIO- AND STEREOCONFIGURATION OF PRODUCTS In order to thoroughly characterize the LOX of interest, an optional procedure is offered to determine the regio- and stereospecificity of oxidation. For this purpose a reaction volume is used that is somewhat larger than that described in Basic Protocol 1 and the Alternate Protocol. The product hydroperoxides are reduced to their corresponding hydroxides, purified by TLC, methyl esterified, and separated by straight-phase HPLC followed by chiral-phase HPLC. In this way a complete structural analysis is obtained. 

Standard straight-phase HPLC (SP-HPLC) column (e.g., 5 pm silica, 4.6 x 250 mm e.g., Rainin)... 

Stern model in interface studies, 626 Stokes law, in emulsion creaming, 601 Storage, of emulsions, stability test, 591-594, 597-598, 604-606 Straight-phase HPLC, lipoxygenase activity measurement, 411-412 Strain response, see Stress/strain responses... 

Bergqvist and Olin (34) have described a straight-phase HPLC method for the analysis of chloroquine as follows ... 

Concerning the mobile phases used in straight-phase HPLC, the reader is also referred to the discussion on mobile phases in Volume 23A of this series Chromatography of Alkaloids Part A Th1n-layer chromatography. 

The general outlines of a straight-phase HPLC-system for basic compounds is given in Scheme 1.2. 

GENERAL OUTLINES OF A STRAIGHT-PHASE HPLC SYSTEM FOR THE SEPARATION OF BASIC COMPOUNDS... 

Bauer and Untz analyzed a series of cinchona alkaloids by means of straight-phase HPLC (Fig.5.15). They found that the addition of 2.65 ml of water to 1 liter of the mobile phase (chloroform - isopropanol - diethylamine(940 57 l)), which corresponds to about 75% saturation, gave optimum separation, as regards resolution versus time of analysis. To obtain the correct percentage of water in the mobile phase, the water content present in the mixture was deter-ined by the Karl Fischer method, and water was then added to obtain a final concentration of 2.65 ml/1. 

Straight phase HPLC-system column, Partisil 5 pm(250x4.5 mm I.D.), mobile phase methanol -2 M ammonia - 1 M ammonium nitrate (30 2 1), flow rate 0.9 ml/min. 

Fig. 7.16. Straight-phase HPLC separation of opium alkaloids...

Sitar et al. used straight-phase HPLC to analyse theophylline in biological fluids. A microparticulate silica gel column and a mobile phase consisting of chloroform - isopropanol -... 

STRAIGHT-PHASE HPLC SEPARATION OF SOME XANTHINE DERIVATIVES51,53,67... 

A straight-phase HPLC method was developed by Gimet and Filloux. The alkaloids, including aconitine, were separated on silica gel using a mobile phase of water saturated diethyl ether, to which some diethylamine was added (see Chapter 7, Fig.7.14). 

Straight-phase HPLC was used by Dunn et al.1 , whereby the alkaloids were separated on silica gel with hexane - 2% ammonia in propanol (7 3). To avoid interference of UV absorbing... 

Synthesis of ketone (3a). The ketone (3a) (Ar1 = Ar2 = Ph) was obtained after hydrolysis of 2a using 6 M HC1/TBME (24 hours) and preparative straight-phase HPLC (eluent hexane/ethyl acetate (99/1)) in 65% yield (>95% by GC-MS) calculated from the starting phenyl bromide in the first Heck arylation of the sequence. 

Straight phase HPLC Zorbax SIL 10 90 isopropanol hexane... 

Two basic types of the LC separation processes can be distinguished. By adsorption chromatography on classic column or straight phase HPLC, usually ordinary (unlabeled) compounds elute first, i.e., the separation factor is less than unity. (a = i/ 2capacity factor). As mentioned above, deuterated or tritiated compounds are more polar and thus are more strongly bound to polar stationary phases. 

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