Separation of Saccharides and Alcohols

The mechanism for separation of sulfate, chloride and nitrate is not entirely clear. Anions that are completely ionized normally cannot be separated by an ion-exclusion process. A weak hydrophobic effect might account for the slight differences in retention of these anions. 

Two general chromatographic methods are available for the determination of carbohydrates. Sugars are anionic around pH 10-12 and can be determined by anion-exchange chromatography. Hydrophilic carboxylate anions are often separated in the same run. The other approach is to separate carbohydrates and sugar 

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Fig. 3-105. Separation of various sugar alcohols and saccharides. - Separator column CarboPac PA-1 eluent 0.15 mol/L NaOH flow rate 1 mL/min detection pulsed amperometry at a Au working electrode injection volume 50 pL solute concentrations 10 ppm xylitol, 5 ppm sorbitol, 20 ppm each of rhamnose, arabinose, glucose, fructose, and lactose, 100 ppm sucrose and raffmose, 50 ppm maltose.

After benzoylation, it was possible to analyze together the food substances of varying chemical structures, such as alcohols, esters of 4-hydroxybenzoic acid, phenolic antioxidants, saccharides, and sugar alcohols. The method allowed the determination of these substances in different matrices by the same analytical procedure, using the same cleanup. The preservatives were separated on an RP-18 column. Acetonitrile-water (50 35) or acetonitrile-water-butylmethyl ether (110 35 40) were used as mobile phases. Detection was UV at 230 nm (71). 

Aldol reaction of (5)-2-benzyloxypropanal with the lithium enolate of methyl 2-methoxy-propanoate gives a 7 2 1 mixture of (3-hydroxyesters (Scheme 13.70). After protection of the alcohol moiety, the isomeric mixture is reduced with LiAlH4 and the resulting primary alcohols separated by chromatography on silica gel. Oxidation of the major alcohol 223 (isolated in 40% yield) into an aldehyde is followed by Wittig methylenation. This provides 224. Hydroboration of 224 gives a primary alcohol that is oxidized (Swem) into aldehyde 225. Hydrogenation yields L-cladinose, a saccharide moiety of erythromycin A [127]. 

Fig. 3-25. Gradient elution of different sugar alcohols and saccharides. - Separator column Ion Pac AS6A eluent (A) water, (B) 0.05 mol/L NaOH + 0.0015 mol/L acetic acid gradient 7% B isocratically for 15 min, then to 100% B in 10 min flow rate 0.8 mL/min detection pulsed ampero-metry on a Au working electrode (post-column addition of NaOH) injection volume 50 pL solute concentrations 15 ppm inositol (1), 40 ppm sorbitol (2), 25 ppm fucose (3), deoxyribose (4), 20 ppm deoxyglucose (5), 25 ppm arabinose (6), rhamnose (7), galactose (8), glucose (9), xylose (10), mannose (11), fructose (12), melibiose (13), isomaltose (14), gentiobiose (15), cellobiose (16), 50 ppm turanose (17), and maltose (18).

Fig. 3-105 reveals that a variety of sugar alcohols, saccharides, and oligosaccharides can be separated under isocratic conditions using sodium hydroxide at a concentration... 

Cyclodextrins exhibit chiral recognition characteristics, because the cavities inside are formed from optically active sugars. Cyclodextrins have been introduced as ligands in NPLC as early as 1989 for the separation of sugar alcohols and various saccharides [35]. Risley and Strege [36] used such a stationary phase for the separation of polar chiral compounds, which could not be resolved under nonaqueous NP conditions. 

Figure 10.316 Separation of alcohols, glycols, and saccharides relevant for fermentation monitoring. Separator column CarboPac MAI eluent 0.48 mol/L NaOH flow rate 0.4 ml7 min detection pulsed amperometry on a gold working electrode peaks (1) 2,3-...

Figure 10.318 Separation of alcohols, glycols, and saccharides in an LB fermentation broth before (a) and after incubation (b) with coll. Chromatographic conditions see Figure 10317 sample preparation centrifuged sample diluted 1 10 with deionized water peaks (1) and (2)...

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