Eluents sodium tetraborate

The buffer system is a combination of buffer for electrophoresis and eluent for the particular chromatographic mode being employed. Figure 5.14 shows the separation of a group of neutral molecules using a capillary packed with a reversed-phase material.38 The buffer was a mixture of 4 mM sodium tetraborate (pH 9.1) and acetonitrile (20 80, v/v). The separation was compared with a micro-HPLC separation in which the same capillary was used but the eluent was pressure driven. As can be seen in Figure 5.14, sharper peaks were obtained with the EOF-driven system. 

Fig. 8.21. FAB mass spectra of steroids separated by CEC. Column, 350 x 0.05 mm i.d. packed with 3 pm Hypersil ODS eluent, 4 mmol/1 sodium tetraborate, 80% acetonitrile applied voltage, 21.5 kV detection, CFFAB-MS, 230-500 amu matrix, post column addition of 1% glycerol in 50% water-50% methanol, 5 pl/min sample, testosterone ([M+H]+ 209), hydrocortisone ([M+H]+ 363), aldosterone ([M+H]+ 361) (in order of elution). (Reproduced from ref. [25] with permission of John Wiley Sons).

The borate buffer is necessary to complex the neutral carbohydrates to give them ionic properties that then allow separation by anion exchange chromatography. A sodium tetraborate-boric acid buffer (pH 8.5) whose composition varies from 0.169 to 0.845 Af in the borate ion is used as the eluent. The anion exchange separation column is maintained at a constant 55°C. 

Bertoldi and colleagues (2004) performed analysis of BAs in grape juice by automatic pre-column derivatization with OPA solution (45 mg OPA, 200 pX 2-mercaptoethanol, 1 mL methanol, sodium tetraborate decahydrate 0.1 M pH 10.5 buffer solution added up to final volume of 10 mL). Chromatographic separation of derivatives (see Figure 4.13) was achieved on a C18 (4.6 x 150mm, 5 pan) column kept at 40 °C at flow rate lmL/min. Eluent A was 0.05 M sodium acetate buffer/tetrahydrofuran 96 4 (v/v) and eluent B was methanol. The gradient program is reported in Table 4.1. 

An exact quantification of fluoride is possible if the advantage of simultaneous analysis is eliminated, and if the chromatographic conditions are changed in the way that fluoride is separated from the carbonate and bicarbonate traveling with the mobile phase. An increase in fluoride retention is achieved by using an eluent of lower elution strength. A dilute solution of sodium tetraborate is particularly suited in this respect. 

To a limited extent, sodium tetraborate is also suited for gradient elution, because boric acid as the suppression product is only weakly dissociated. As an alternative to carbonate/bicarbonate systems, amino acids (a-aminocarboxylic acids) may be used as an eluent [90,91]. Their dissociation behavior is depicted in Figure 3.102. At alkaline pH, amino acids exist in the anionic form due to the dissociation of the carboxyl group and thus may act as an eluent ion. The product of the suppressor reaction is the zwitterionic form with a correspondingly low background conductance. This depends on the isoelectric point, pi, of the amino acid. 

Figure 3.204 Gradient elution of inorganic and organic anions with a sodium tetraborate eluent. Separator column lonPac ASM eluent Na2B407 gradient 2 mmol/L isocratically for 6 min and then linearly to 17.5 mmol/L flow rate 1.5 mL/min detection suppressed...

Figure 10.125 Trace analysis of anions in high-purity boric acid. Separator column lon-Pac ASM eluent 9mmol/L sodium tetraborate flow rate 1 mL/min detection suppressed conductivity injection volume ...

Eluent 0.05 M sodium tetraborate containing 12% isopropanol and 6% bovine serum albumin (BSA), pH 9.30-9.92... 

Eluent 6% bovine scrum albumin (BSA) in 0.05 M sodium tetraborate contg. 6% isopropanol, pH 9.30 Eluent 6% bovine serum albumin (BSA) in 0.05 M sodium bicarbonate + 0.05 sodium carbonate containing 6% isopropanol. pH 9.80... 

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