Sorbitol electrodes

Creighton An electrolytic process for reducing sugars to their corresponding polyols. Glucose is thus reduced to sorbitol, mannose to mannitol, and xylose to xylitol. The electrodes are made of amalgamated lead or zinc the electrolyte is sodium sulfate. Invented in 1926 by H. J. Creighton. 

Electrochemical detection of carbohydrates at nickel-copper and nickel-chromium-iron alloy electrodes has been reported for sorbitol, and has been used as a detector for HPLC analysis [36]. Oxidation of various carbohydrates at the electrodes was used for detection, and baseline separation was achieved for mixtures of sorbitol, rhamnose, glucose, arabinose, and lactose. 

Hazemoto et al (1+0) developed an ion-selective electrode sensitive to saccharin, by establishing an ion association between Fe2+-bathophenanthroline chelate and saccharin in nitrobenzene. The electrode developed could measure saccharin ion in presence of other sweetening agents e.g., sucrose, glucose, sodium cyclamate and sorbitol in the concentration range of 10 - - to 10 M. 

Sugars with a potential aldehyde function can be reduced electrochemically at electrodes of mercury or amalgamated lead [23]. The rate of this process is controlled by the rate for the conversion of the cyclic to the open-chain form of the sugar. A technical-scale plant [24] for the conversion of glucose to either sorbitol or mannitol was operated in the past, but this method has largely been ousted by other processes. Glucose is converted to... 

Some details are given by Merck in Ref. 112. The electrochemical oxidation is performed in alkaline solution using nickel or nickel oxide electrodes [113]. Hydrogen evolved at the cathode can be used for the hydrogenation of D-glucose to D-sorbitol, the first step in the vitamin C synthesis by the Reichstein route. Obviously, Merck doesn t use electrodes with high specific areas but prefers to stop the electrolysis at a conversion rate of 90%. The oxidation is completed with sodium hypochlorite solution. 

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. 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.

FIGURE 6.19 Deconvoluted linear scan voltammograms for paraffin-impregnated graphite electrodes modified with different cohalt cordierites (a) cordierite glass, (h) p-cordicrile, and (c) a-cordierite, immersed into 2.0 mM sorbitol plus 0.10 M NaOH. Potential scan rate 20 mV/sec. 

The effect of surface structure, the role of the various crystal faces polyols on gold, sorbitol at polycrystalline and single crystal platinum electrodes, 2,3 butanediol stereoisomers at platinum single crystal electrodes, studies on the behavior of oxocarbons (squaric and croconic acids) on single crystal platinum surfaces. 

Thamsen ], Hie acidic dissociaticm ccmstants of glucose, mannitol and sorbitol, as measured by means of the hydrogen electrode and the glass electrode at O and 18 C, Acta Chem. Scand., 6, 270-284 (1952). 

The examples illustrate the diversity as well as the common features of a paired electrosynthesis. One can start with one or two substrates to generate one or two products. Electrode processes can be mediated or direct. Undivided and divided cells are employed in paired electrosyntheses. But as in the BASF phthahde example, it is crucial for the synthesis of glyoxylic acid, sorbitol, and methyl ethyl ketone that the cathodic process is the reduction of the substrate and not the reduction of protons because in these cases protons are generated at the anode and the electrolysis takes place in aprotic solvent. Therefore effects that minimize the overpotential of hydrogen have to be omitted. Reaction control is important in all described examples, and consequently the cell and the setup have to fit for each case. Work-up and product isolation are significant for a successful synthesis and can be even more challenging in a paired synthesis. 

Fig. 3-178. Separation of the artificial sweetener palatinitol. — Separator column CarboPac PAl eluant 0.1 mol/L NaOH flow rate 1 mL/min detection pulsed amperometry on a gold working electrode injection volume 50 pL peaks (1) sorbitol, (2) mannitol, (3) 10 mg/L a-D-glucopyranosido-1,6-sorbitol (GPS), 10 mg/L a-D-glucopyranosido-1,6-mannitol (GPM), and (4) isomaltose.

Fig. 3 -193. Separation of aiditois and aldoses. - Separator column CarboPac MAI eluant 0.75 mol/L NaOH flow rate 0.4 mL/min detection pulsed amperometry on a gold working electrode solute concentrations 2 nmol each offucitol (1), N-acetylgalactosamine (reduced, 2), N-acetylglucosamine (reduced, 3), xylitol (4), arabitol (5), fucose (6), sorbitol (7), dulcitol (8), N-acetylglucosamine (9), mannitol (10), N-acetylgalactosamine (11), mannose (12), glucose (13), and galactose (14).

A simpler version of this method was also developed for the same purpose, requiring only the integration of sorbitol dehydrogenase into an electrode whose surface was modified with hyaluronic acid, carbon nanotubes, and toluidine blue [65]. Although the sensitivity of the determination is not significantly altered by the modifications, the determination rate increases enormously to 65 h h so that this strategy becomes more attractive than the previous one. 

Still in the field of amperometric detection, sorbitol can also be determined by a non-enzymatic methodology employing a nickel oxide-modified electrode that functions as a sensor for alditols [44],... 

---