Eluant boric acid

If necessary, adjust the pH to 8.4-8.5 using boric acid crystals or 0.1 M sodium hydroxide the pH of the eluant is critical. 

Polyspher IC AN-1 from Merck AG (Darmstadt, Germany), consisting of a hydrophilic polymethacrylate packing with a particle diameter of 12 pm, exhibits a similar selectivity. Depending on the type of application, this column can be operated with eluants based on phthalic acid, p-hydroxybenzoic acid, tartaric acid, oxalic acid, or boric acid. Figure 3-16 shows a typical chromatogram obtained with a phthalic acid eluant. Under these chromatographic conditions (pH 4) orthophosphate elutes as a monovalent anion ahead of chloride. 

Boric acid is especially suitable for lowering the pH value. Because of its low degree of dissociation, it contributes only marginally to the increase in background conductivity. In general, an increase in the eluant pH is accomplished with sodium hydroxide, because it suppresses to water and hardly affects the background conductivity. 

As an example, Fig. 6-26 shows the separation of mono-, di-, and tri-ethyl-amine, accomplished by using octanesulfonic add as the ion-pair reagent The less hydrophobic hexanesulfonic acid is used in combination with boric add as the eluant for the separation of ethanolamines, as shown in Fig. 6-27. These compounds are detected by measuring the electrical conductivity, so the background conductivity is generally lowered with a membrane suppressor. The addition of boric acid to both the eluant and the regenerant serves to enhance the sensitivity for di- and tri-ethanolamine. 

Quaternary ammonium compounds can be analyzed under similar chromatographic conditions, but without the addition of boric acid. This includes choline (2-hydroxyethyl-trimethylammonium hydroxide), which is commonly found in fauna and flora as a basic constituent of lecithin-type phospholipids. The ion-pair chromatographic separation of choline requires an eluant, in addition to... 

Fig. 9-46. Trace analysis of silicate in a high-purity water sample after pre-concentration. -Separator column lonPac AS4A-SC (2-mm) eluant 10 mmol/L boric acid -i- 10 mmol/L NaOH flow rate 0.25 mL/min detection ...

Fig. 9-67. Trace analysis of cations in high-purity boric acid. - Separator column lonPac CS12A eluant 20 mmol/L methanesulfonic acid flow rate 1 mL/min detection suppressed conductivity injection 500 pL...

Detection methods. - Various metallic wires were investigated for use in constant-potential amperometric detection of carbohydrates in HPAEC eluates. Copper proved best, and when conditions were optimized, picomole amounts of various sugars could be detected. Conditions fcH-post-column generation of fluorescence by reaction of mono- to tri-saccharides with an ethanolamine-boric acid reagent were optimized, and applied to the h.p.Lc. analysis (anion-exchanger, alkaline aq. borate eluant) of mono- and di-saccharides in wine. The detection of disaccharides was markedly improved if a post-column acid-catalysed hydrolysis reactor was added prior to detection. ... 

---