Polar bonded phase

Even with mobile-phase modifiers, however, certain polymer types cannot be run due to their lack of solubility in organic solvents. In order to run aqueous or mixed aqueous/organic mobile phases, Jordi Associates has developed several polar-bonded phase versions of the PDVB gels as discussed earlier. Figures 13.60 thru 13.99 detail examples of some polar and ionic polymers that we have been able to run SEC analysis of using the newer bonded PDVB resins. 

Figure 4.27 Flow chart for coluwi selection based on sample type (m - molecular weight). PLC precipitation-liquid chromatography SEC = size-exclusion chromatography lEC - ion-exchange chromatography HIC hydrophobic interaction chromatography LSC liquid-solid chromatography RPC - reversed-phase liquid chromatography BPC (polar) bonded-phase chromatography and IPC - ion-pair chromatography.

S.O. Jansson, Effect of counter-ions in ion-pair liquid chromatography of hydrophobic amines on non-polar bonded phases , J. Liq. Chromatogr., 1982, 5, 677. 

Riggin and Howard (1979, 1982), Matsui et al. (1983), Fabre et al. (1984), and Ahuja et al. (1988) reported that High Performance Liquid Chromatography (HPLC) with UV or electrochemical detection is capable of analyzing 1,2-diphenylhydrazine. Reversed phase chromatographic columns have been used most often (Ahuja et al. 1988 Fabre et al. 1984 Riggin and Howard 1979, 1982). Cyano-amino polar bonded phase columns also have been used (Matsui et al. 1983). Using a reversed phase and UV detection, the minimum amount detected (on column amounts) is approximately 6-7 ng and the minimum amount quantifiable is less than 1 pg (Ahuja et al. 1988 ... 

Carotenoid separations can be accomplished by both normal- and reversed-phase HPLC. Normal-phase HPLC (NPLC) utilizes columns with adsorptive phases (i.e., silica) and polar bonded phases (i.e., alkylamine) in combination with nonpolar mobile phases. In this situation, the polar sites of the carotenoid molecules compete with the modifiers present in the solvent for the polar sites on the stationary phase therefore, the least polar compounds... 

Several new phases applied to maltosaccharide analysis that seem to be promising have been described in the literature, for instance, a silica-phase covered with polymeric polyamine resin, and an entirely polymeric resin containing an amide function (35). In any case, partition chromatography is restricted mainly to the utilization of polar-bonded phases, as already described. Nevertheless, there have been a certain number of applications of reversed-phase chromatography that permit relatively simple separations to be achieved. Octadecyl-bonded silica phases are the most widely used, although few applications involve carbohydrate analysis. Their interest lies rather in the analysis of derivated sugars, where the selectivity increases (36). 

Of the polar bonded-phase packings that have been investigated, the interactions between carotenes and nitrile stationary phases are very weak thus the limitations described for silica apply (164). Amino-bonded phases eluted with iso-octane containing 0.5% stabilized tetrahydrofu-ran separate a- and /3-carotene (unresolved) from y-carotcnc canthaxanthin and /3-cryptoxanthin are not eluted (161). The cis isomers of /3-carotene are separated from the all-trans isomer thus amino columns offer an alternative option to alumina columns for determining all-trans-/3-carotene without its cis isomers interfering. 

Semipreparative HPLC has been employed to obtain a vitamin D-rich fraction of the unsaponifiable matter for subsequent quantitative HPLC. Combinations of chromatographic modes used for offline semipreparative and quantitative analysis have included polar bonded-phase/adsorption (211,212), reversed-phase/adsorption (194,213), and adsorption/reversed-phase (70,125). An online two-dimensional HPLC technique using two polar bonded-phase columns has also been described (214). 

In general, there is a wide variety of chromatographic modes (types) that can be employed for the HPLC determination of food components, but only a few have been used for the determination of NOC. These include partition/adsorption on silica gel, liquid-liquid partition on polar-bonded phase (e.g., cyano, amino) or nonpolar hydrophobic-bonded phase (e.g., reversed-phase), and anion-exchange chromatography. Macrae (61) discussed the theories behind the various modes of chromatography. 

Bonded diol Si-O-Si-C OH OH 1 1 -c—c-1 Polar bonded phase A polar phase that has a hydrogen bonding capability similar to that of unbonded silica useful in size-exclusion chromatography and in the analysis of glycols and glycerol, oils, lipids, and related compounds... 

Carboxylic acid (CBA) Si-O-Si-C -CH2CH2COOH Polar bonded phase Medium-polarity phase that has a weak cation exchange capability useful for strong cations above pH of 4.8, most of the functional groups are negatively charged, and therefore the phase can be used for cationic compounds lowering pH to 2.8 elutes retained analytes... 

Cyclohexyl (CH) Si-O-Si-C -CeH, Moderately polar bonded phase A moderately polar phase that is used for aqueous samples moderate polarity derives from the polar substrate, silica has a polarity similar to a C2 bonded phase... 

Bonded nitrile Si-O-Si-C -CH2CH2CH2-CsN Moderately polar bonded phase Moderate polar phase, but with selectivity modified with respect to silica less sensitive to mobile phase impurities than silica also called cyanopropyl phase... 

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