Separation factor phosphate buffers

The effect of concentration of cationic (cetylpyridinium chloride, CPC), anionic (sodium dodecylsulfate, SDS) and nonionic (Twin-80) surfactants as well as effect of pH value on the characteristics of TLC separ ation has been investigated. The best separ ation of three components has been achieved with 210 M CPC and LIO M Twin-80 solutions, at pH 7 (phosphate buffer). Individual solution of SDS didn t provide effective separation of caffeine, theophylline, theobromine, the rate of separ ation was low. The separ ation factor and rate of separ ation was increase by adding of modifiers - alcohol 1- propanol (6 % vol.) or 1-butanol (0.1 % vol.) in SDS solution. The optimal concentration of SDS is 210 M. 

Results after annealing of the polymers under vacuum in the dry state at 120°C for 24 h and heating of the polymers at 130°C for 4 h in the mobile phase. The MIP using benzene (C6H6) as diluent was evaluated using acetonitrile/0.05 M potassium phosphate buffer, pH 7 7/3 (v/v) as mobile phase. The separation factor prior to the heat treatment was 4.1 in this mobile phase. Data from [7]... 

Fig. 5.37. 3D-representation of the capacity factors of five different triazines injected separately (10 nmol) on a reference column (REF), an ATR imprinted column and a PRO imprinted column in the mobile phase acetonitrile/potassium phosphate buffer, 0.05 M, pH 4 30/70 (v/v). The amount of CYA injected on the reference column was 100 nmol. The hydrophobicity of the triazines decrease from front to back of the graph. From Dauwe and Sellergren [32]. 

Local considerations. There are many other local factors which dictate the path of method development. An increasingly common example is the development of a method which, as well as serving for quantitation, may be directly transferred to HPLC-mass spectrometry (commonly referred to as LC-MS) to allow the identification of minor components in a sample. This is achievable if the desired separation can be obtained using an ammonium acetate buffer instead of the more usual phosphate buffer. On the other hand, if it was intended that the unknown minor components should be isolated in milligram quantities to allow full structural elucidation using techniques such as H NMR as well as mass spectrometry, then conditions would be developed especially for the isolation unless the conditions for quantitative work coincidentally also lent... 

Animals were inoculated with Enterobacter cloacae and hemolymph was collected as described (11,12). Hemolymph proteins were separated by isoelectric focusing (IEF) on LKB PAG plates at pH 3.5-9.5 according to the manufacturers instructions. To detect antibacterial activity after IEF, the electrophoretic plates were overlaid with phosphate buffered LB agar seeded with E coli strain D31. The antibacterial factors diffused from the IEF plate into the bacteria-containing overlay thus blocking bacterial growth and revealing bands of activity (13). 

Separation of bile acid-CoA derivatives from unreacted coenzyme A can be effected by high-performance liquid chromatography. With a radial compression C,g column containing 5-/tm particles, coenzyme A was eluted with or immediately following the solvent front with a solvent system of 2-propanol/50 mM phosphate buffer (pH 7.0) (160/340) and a UV-detector set at 254 nm. Capacity factors for the above CoA derivatives are 1.50, 3.50, 4.18 and 9.50. CoA derivatives of comparable 5a-bile acids, purified and separated in a similar manner were eluted just prior to the comparable 5)8-derivative [36]. CoA derivatives of 5jS- and 5a-cholate and de-oxycholate were separable with this solvent system. 

Despite the drawbacks of interferences, ICP-MS is extensively used as detector in As speciation research. The consumption rate of liquid sample by ICP is often similar to that of HPLC and the combination of instmmentations can easily be achieved, simply by connecting the effluent line of the column to the input line of the nebulizer. Nevertheless, HPLC column conditions are selected primarily to get optimum separation, but of course, here too, the limiting factors of ICP-MS must be taken into account for instance the use of phosphate buffer as mobile phase is not suitable for ICP-MS. 

The pH of the phosphate buffer as well as the percent acetonitrile in the mobile phase are the major factors affecting the separation of the anilines on the C-18 columns. By employing a low pH, the halogenated aniline compounds are separated not as the neutral free bases but as their corresponding anilinium ions. Thus the use of a lower pH buffer will decrease the elution time for all the compounds (74). 

Although the target function of neutral CDs is to exert chiral selection in the EKC separation of optical isomers, they have often been used as auxiliary complex ligands as a means of improving resolution of closely eluting achiral positional and structural related compounds or to reduce significantly apparent retention factors. The separation of seven positional and structural naphthalenesulfonate isomers (pH 3.0 phosphate buffer/p-CD) " and five 2,4-dinitrophenylhydrazine (DNPH)-aldehyde derivatives in vehicular emission (pH 9.0 borate buffer/SDS/p-CD) are examples of neutral CD-mediated separations. 

This has been repeatedly confirmed in several studies see, for example. Figure 4.4. Here, the retention (bars) and separation factors (lines) of tricyclic antidepressants in acidic acetonitrile/phosphate buffer are shown. In the case of quite different retention factors depending on the hydrophobic character of the phases (differently strong interactions), apart from a few exceptions very similar separation factors result. Although the analytes are retained for different lengths of time on the stationary phases, they show a similar selectivity behavior. This is observed especially with neutral or - by means of the pH-neutralized molecules. In this case, mainly hydrophobic interactions between the analytes and the surface of the material dominate. These are not especially specific the individual differences of the phases with respect to selectivity do not come into effect. 

Fig. 1 Dependence of the retention factor, fe, on temperature, T. The solutes are (1) resorcinol, (2) phenol, (3) p-nitroaniline, (4) o-cresol, (5) nitrobenzene, (6) 2,6-xylenol, (7) 2,4-xylenol, (8) toluene, (9) 2-naphthol, (10) p-propylphenol, (11) p-butylphe-nol, and (12) p-amylphenol. Capillary 50 p,m I.D. X 570 mm (effective length, 500 mm) separation solution 50 mM SDS in 100 mM borate-50 roM phosphate buffer (pH 7.0) applied voltage 15 kV detection wavelength 214 nm.

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