Phosphate-Borate Buffer

Fig.Sa-f. The sensorgram of the repeated injection of the aqueous viologen dimer 2 (a, c, e) and the antibody (b, d, f) solutions. [Viologen dimer 2]=2.0 pM and [antibody]=2.0 pM in phosphate borate buffer. Injection period 60 s for a-c and 120 s for d-f. A solution of viologen dimer 2 or the antibody passes over the surface of the sensor chip for 60 or 120 s at a constant flow rate of 20 pL min. The surface of the sensor chip was subsequently washed with buffer...

Fig. 12a,b. The sensorgrams for the binding of the antibody dendrimer (a) or IgG (b) to the anionic porphyrin immobilized onto the surface of the sensor chip. Phosphate borate buffer (0.1 M, pH 9.0) was used. TCPP was immobilized via hexamethylenediamine spacer onto the sensor chip and then a solution of IgG or the dendrimer was injected to the flow cell. After 60 s from the injection of the antibody solutions, flow ceU was filled with buffer... 

In the case of L-rhamnulose-1-phosphate aldolase (RhaD), we found that the problem of phosphorylated substrate requirement (dihydroxyactone phosphate (DHAP)) could be overcome by a simple change in buffer. Thus, when using borate buffer, reversible borate ester formation created a viable substrate out of dihydroxyacetone, which is not otherwise accepted by the wild-type enzyme (Figure 6.6) [23]. The process was used in a one-step synthesis of... 

Non-volatile buffers such as phosphates, borates, perchlorates and phosphoric acid should be avoided at all costs because of high background ion current, source contamination and blockages, and in the case of perchlorates, explosions. Figure 6.4 shows the mass spectrum of typical background when using phosphoric acid in the eluent. If the solvent system for a particular analysis does not assist the electrospray process, it is possible to enhance ionisation by postcolumn addition of a suitable volatile buffer. 

Phosphate-borate buffer is the most frequently used solution for the preparation of microemulsion systems. An increase in the buffer concentration... 

Natural-product analysis 75 mM SDS, 1000 mM n-butanol, 90 mM n-octanol, phosphate-borate buffer, pH 7 29, 37... 

The separation was carried out using a 0.05 mm x 50 cm capillary at 15 kV with a phosphate/borate running buffer. Figure 14.6 shows separation at the optimal pH of 9.7 of atenolol (50 jug/ml) from its impurities spiked into solution at concentrations of 5 pg/ml. The elution order is as would be predicted from the ionisable groups in the molecules. Atenolol (AT) elutes first since it bears a positive charge on the basic secondary amine group (p/Ca 9.6). The dimer (TA) also carries one positive charge... 

This was not a subject of systematic research except the approval that phosphate buffer was preferred due to data of the 1970s from Laux [4]. Up to now, there is only one scientific prove out of chemical neutralization experiments on borate buffer, phosphate buffer, or Diphoterine in the beaker [5]. In clinical context, there is only one systematic study of Merle and Gerard who... 

This mode of electrophoresis, in which the electrolyte migrates through the capillary, is the most widely used. The electrolyte can be an acidic buffer (phosphate, citrate, etc.) or basic buffer (borate) or an amphoteric substance (a molecule that possesses both an acidic and an alkaline function). The electro-osmotic flow increases with the pH of the liquid phase, or can be rendered non-existent. 

Dissolve the protein or other amine-containing macromolecule to be modified at a concentration of 1-10 mg/ml in a buffer having a pH from 7 to 10. The higher the pH, the more efficiently Schiff base formation will occur. Phosphate, borate, and carbonate buffers at 0.01—0.1 M are acceptable. Avoid amine-containing buffers like Tris and glycine, since they will react with glutaraldehyde. 

Figure 5.8 Separation of eleven water-soluble vitamins by MECC. Peaks 1, pyridoxamine 2, nicotinamide 3 pyridoxal 4, vitamin B6 5, vitamin B2 6, vitamin B12 7, vitamin B2 phosphate 8, pyridoxamine 5 -phosphate 9, niacin 10, vitamin Bi 11, pyridoxal 5 -phosphate. Conditions buffer, 50 mM SDS in 20 mAf phosphate-borate buffer, pH 9.0 applied voltage, 20 kV detection, UV absorbance at 210 nm. (Reprinted from Ref. 20 with permission.)...

Gilar et al. have also applied CE to the separation of dihydropyridine calcium antagonists [25]. Their method used an uncoated capillary (76 cm x 75 pm i.d.) at 20 kV, a running buffer of 20-25 M phosphate-borate buffer (pH 9-9.5) containing 1% urea, and detection at 240 nm. The buffer also contained 10 mM p-cyclodextrin, and varying amounts of SDS. 

For most purposes, phosphate, borate, citrate, and phosphate-borate buffers can be used. Zwitterionic buffers (Tris, CHAPS, etc.) are sometimes necessary to enable work at high concentrations without excessive currents and consequently high temperatures in the capillary. 

The successful use of MEKC for the analysis of illicit heroin and cocaine was also reported by Staub and Plaut (1994), who used 50 mM SDS in phosphate-borate buffer (10 and 15 mM, respectively) containing 15% of acetonitrile (pH 7.8). In 25 minutes, these authors achieved separation and determination of paracetamol, caffeine, 6-monoacetylmorphine (6-MAM), acetylcodeine, procaine, papaverine, heroin, and noscapine, although with peaks sometimes skewed. On-line recorded UV spectra of the peaks helped the identification of the individual peaks. 

The use of the cationic micellar agent CTAB (50 mM) in phosphate-borate buffer (10 mM of each salt), pH 8.6, with 10% acetonitrile was preferred because of a faster separation (about 15 min) of heroin and related substances. Because the cationic surfactant, which coats the capillary silica wall with a positively charged layer, reverses the electroosmotic flow (EOF), the voltage (-15 kV) must be applied with a reversed polarity (with the cathode at the injection point). Detection was by UV absorption at 280 nm. 

Wernly and Thormann (1991) used a phosphate-borate buffer pH 9.1 with 75 mM SDS for the qualitative determination in urine of many drugs of abuse (and their metabolites), including benzoylecgonine, morphine, heroin, 6-monoacetylmorphine, methamphetamine, codeine, amphetamine, cocaine methadone, methaqualone, and benzodiazepines. 

An MEKC system quite similar to that described earlier (50 mM SDS in phosphate-borate buffer, pH 7.8) allowed, also, a high resolution separation of barbiturates, including barbital, allobarbital, phenobarbital, butalbital, thio-... 

Another MEKC separation (75 mM SDS, phosphate-borate buffer, pH 9.1) was reported for die determination of ll-nor-A-9-tetrahydrocannabinol-9-carboxylic acid, the major metabolite of A-9-tetrahydrocannabinol present in urine (Wemly and Thormann, 1992a). Sample treatment included basic hydrolysis of urine (5 mL), solid phase extraction, and concentration. The resulting sensitivity was 10 to 30 ng/mL (i.e., comparable to the cutoffs of immunoassays). Again, detection was by on-line recording of peak spectra, by means erf fast-scanning UV detector. 

Quite recently, Schafroth et al. (1994) determined the major urinary compounds of eight common benzodiazepines (flunitrazepam, diazepam, midazolam, clonazepam, bromazepam, temazepam, oxazepam, and lorazepam). The used MEKC with 75 mM SDS in a phosphate-borate buffer (pH 9.3). After enzymatic hydrolysis and extraction with commercial double-mechanism cartridges, the sensitivity was reportedly better than that obtained with the common immunoassay EMIT (enzyme-multiplied immunoassay technique). 

Other common species that have an effect on the pH and buffering capacity of natural systems include phosphates, borates, amino acids, and some organic compounds (generally weak acids). Phosphoric acid is a polyprotic acid that liberates one proton in each of its three dissociation steps, leaving a weaker acid... 

Disodium hydrogen phthalate-sodium dihydrogen orthophosphate Dipotassium hydrogen phthalate-potassium dihydrogen orthophosphate Potassium dihydrogen orthophosphate-sodium hydroxide Borate buffer, phosphate buffer... 

In aqueous solution, phosphate, borate, and carboxylate buffers are applicable, but in mixed solvents the solubility of phosphate and borate buffers is low in such mixtures, carboxylate buffers may be used in slightly acid, and amine buffers in slightly alkaline medium. To avoid excessive buffer concentrations it is advisable to maintain pH in the bulk of the solution constant by means of a pH-stat. 

MEKC, 60 mM SDS in 6 mM phosphate-borate buffer pH 8.5,15% methanol (by volume)... 

A micellar electrokinetic chromatographic method allows the separation of optically isomeric diltiazem hydrochloride using bile salts as chiral surfactants. The chiral separation of diltiazem hydrochloride from several analogs is achieved at ambient temperature using 0.05M sodium taurodeoxycholate in a 0.02M aqueous phosphate-borate buffer solution of pH 7.0. Separation is performed using a fused-silica capillary tube (650 mm x 50 mm I.D.) and a voltage up to +25 kV. Detection is achieved on-column using UV adsorption at 210 nm (31). 

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