Hiba

Bridot JL, Faure AC, Laurent S, Riviere C, Billotey C, Hiba B, Janier M, Josserand V, Coll JL, VanderElst L, Muller R, Roux S, Perriat P, Tillement OJ (2007) J Am Chem Soc 129 5076... 

Escambia (1) A process for oxidizing isobutene to a-hydroxy-isobutyric acid (HIBA), for use as an intermediate in the manufacture of methacrylates. The oxidant was dinitrogen tetroxide, N204. Operated by the Escambia Chemical Corporation, FL, in 1965 before its destruction by an explosion in 1967. It has not been used again. 

The effect of the hydration radius of these cations is very important, and mobilities are sometimes very close or the same as for potassium and ammonium. For this reason, a complexing agent is added to the buffer. Several complexing agents such as a-hydroxyiso-butyric acid (HIBA), 18-crown-6, phthalic, malonic, tartaric, lactic, citric, oxalic, or glycolic acid may be used. 

A second way to improve resolution is the modification of mobility by complexation of the analyte. Many buffers for analysis of cations use HIBA or 18-crown-6 to improve the resolution between sodium, potassium, calcium, magnesium, etc. as well as some aliphatic amines. By diluting an existing validated buffer, one can change the concentration of the complexation agent and thus also the selectivity of the system. 

Sagara, N. (1999). Mycological approach to the natural history of talpid moles—A review with new data and proposal of habitat-cleaning symbiosis, in Recent Advances in the Biology of Japanese Insectivora (Y. Yokohata and S. Nakamura, Eds.). Shobara, Hiroshima Hiba Society of Natural History, 33-55. 

Fig. 1.22. Direct injection of aluminium processing solution. Conditions Supelcosil LC-18-DB column gradient programme at a flow-rate of 1.0 ml/min from 1.05 M HIBA to 0.4 M HIBA over 10 min. and held at 0.4 M for 5 min. modifier, 1-octanesulphonate at 0.01 M (A), eluents at pH 4.5 (B), eluents at pH 3.8 detection at 658 nm after post-column reaction with Arsenazo III sample injected, 50 pi sample dilution, (A) 10 ml to 100 ml,...

Fig. 1.24. Effect of pH on the retention time of the rare earths. Conditions Supelco LC-18 DB column gradient program at a flow rate of 1.0 ml/min from 0.05 mol/1 HIBA to 0.4 mol/1 HIBA over 10 min and held at 0.4 mol/l for 5 min modifier, concentration of 1-octanesulfonate at 1 x 10 -.

Fig. 1.26. Direct injection of a solution of neodymium (80%)-iron (20%) alloy. Conditions Supelco LC-18 DB column curve (A), gradient program at pH 4.5 from 0.05 mol/1 HIBA to 0.4 mol/1 HIBA in 10 min at flow rate of 1.0 ml/min modifier, 0.01 mol/1 1-octanesulfonate sample size, 50 pi sample dilution, 0.965 g per 100 ml. Curve (B), gradient program at pH 4.5 from 0.25 mol/1 HIBA to 0.5 mol/1 HIBA in 8 min at 1.0 ml/min modifier, 0.02 mol/1 1-octanesulfonate sample size, 50 pi sample dilution, 0.965 g per 100 ml and 5 ml/100 ml.

Studies with essential oils in human beings have also shown beneficial effects. For instance, anxiolytic effects were observed in patients awaiting dental care treatment in a waiting room previously aromatized with essential oils from Citrus sinensis (L.) Osbeck [378]. In another controlled study, 14 patients undergoing hemodyalisis benefited from hiba and lavender aromas and presented a feeling of calm [379]. Several studies on aromatherapy have attracted the attention of researchers in a study of chemical, pharmacological, and therapeutic properties of these substances [380]. 

Addition of a weak complexing anion (L), such as tartrate or a-hydroxyisobutyrate (HIBA), will convert part of a metal ion to a complexed form that is uncharged or has a lower positive charge than the free metal ion. This will cause the metal ion to elute more rapidly. Referring to Eq. 5.20, the metal ion in solution (Is,in) will be partially complexed ... 

Our ability to separate free metal cations by CE is limited because many of the metal ions have similar electrophoretic mobilities. An excellent way to enhance the separation of metal ions is to add a relatively weak complexing ligand (L ) such as tartrate, lactate or a-hydroxyisobutyric acid (HIBA) to the BGE. Now part of each metal ion will remain as the free ion (M, for example) and part will be converted to a complexed form (ML , ML2, ML3, for example). The total mobility (p) will be the sum of the mole fraction of each species (a) multiplied by its mobility. 

Jones et al. obtained exeellent separation of 15 alkali, alkaline earth, and divalent transition metal ions with 6.5 mM HIBA at pH 4.4 to partially complex some of the cations [11]. A protonated amine cation containing a benzene ring (Waters UV Cat 1) was used for indirect UV detection. All of the 13 lanthanides have been separated using HIBA under similar conditions (Fig. 10.12). 

Lactate has the same a-hydroxycarboxylate complexing group as tartrate and HIBA, but it is a smaller molecule and forms somewhat weaker complexes than tartrate with most metal ions. Shi and Fritz found that a lactate system gave excellent separations for divalent metal ions and for trivalent lanthanides. A brief optimization was first carried out to establish the best concentrations of lactate and UV probe ion and the best pH. Excellent separations were obtained for all thirteen lanthanides, alkali metal ions, magnesium and the alkaline earths, and several divalent transition metal ions. All of these except copper(II) eluted before the lanthanides. An excellent separation of 27 metal ions was obtained in a single run that required only 6 min (Fig. 10.13). 

Figure 10.12. Separation of 13 lanthanides using HIBA. Electrolyte 4 mM HIBA, 5 mM UV Cal I, pH...

Further insight into the separation is given by the separation of lanthanides with 4 mM HIBA at pH 4.3 as the complexing agent (Fig. 10.12). Using published formation constants, the fraction of rare earths present in various chemical forms was calculated by a well-known method under the same conditions of pH and HIBA concentration used for the CE separation in Fig. 10.12. The calculated distribution of chemical species for each rare earth is shown in Table 10.4. 

Table 10.4. Fractions of free (o m) and complexed (o(mi..O rare earth metal ions and average number of ligands (n) in 4 mM HIBA electrolyte solution at pH 4.1...

The proposed mechanism necessitates a very fast rate of equilibrium between the free metal ions and the various complexed species. This condition is fulfilled with lactate and HIBA for the metal ions studied. However, metal ions that have slow com-plexation kinetics cannot be determined by a partial complexation CE system. For example, aluminum(IIl) gave no peak in a lactate system. 

Abbreviations 2-AP = 2-aminopyridine a-La = a-lactoalbumin P-Lg = P-lacto-globulins CAPS = 3-[cycloheylamino]-1-propane-sulfonic acid CN = caseins DMF = dimethylformamide HIBA = a-hydroxyisobutyric acid Hx = Hypoxanthine HxR = inosine ID = inner diameter IMP = inosine 5 -monophosphate MeOH = methanol MHEC = methylhydroxycellulose PA = polyacrylamide PEG = polyethylene glycol PBS = phosphate buffered saline PTFE = polydetrafluoroethylene. 

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