Water-soluble basic analytes

Ion-pairing reagents are detergent-like molecules added to the mobile phase to provide additional retention or selectivity for the analytes with opposite charge. Long-chain alkyl sulfonates are commonly used for the separation of water-soluble basic analytes as shown in Figure 16 in the analysis of water-soluble vitamins (WSV). Hexanesulfonate binds with... 

In a typical acid—base titration, the analyte is a solution of a base and the titrant is a solution of an acid or vice versa. An indicator a water-soluble dye (Section J), helps us detect the stoichiometric point, the stage at which the volume of titrant added is exactly that required by the stoichiometric relation between titrant and analyte. For example, if we titrate hydrochloric acid containing a few drops of the indicator phenolphthalein, the solution is initially colorless. After the stoichiometric point, when excess base is present, the solution in the flask is basic and the indicator is pink. The indicator color change is sudden, so it is easy to detect the stoichiometric point (Fig. L.3). Toolbox L.2 shows how to interpret a titration the procedure is summarized in diagram (3), where A is the solute in the titrant and B is the solute in the analyte. 

Supercritical fluid chromatography has some inherent restrictions. As the polarity of C02 is low, many analytes of interest are simply insoluble and cannot be analysed. Also compounds with acid and basic functional groups in their structure, and compounds which are water-soluble only cannot be satisfactorily analysed using pSFC techniques [363],... 

FIGURE 16 HPLC chromatogram of water-soluble vitamins using ion-pair chromatography. LC conditions and peak identification are shown in the inset.The retention times of basic analytes (pyridoxine and thiamine) are strongly dependent of the concentration of ion-pairing reagent (1-hexanesulfonate) in the mobile phase. Reprinted with permission from Reference 17. 

The SP procedure of water-soluble vitamins from multivitamin tablets is particularly challenging due to the diverse analytes of varied hydrophobicities and pfC. Water-soluble vitamins (WSVs) include ascorbic acid (vitamin C), niacin, niacinamide, pyridoxine (vitamin B ), thiamine (vitamin Bj), folic acid, riboflavin (vitamin B2) and others. While most WSVs are highly water soluble, riboflavin is quite hydrophobic and insoluble in water. Folic acid is acidic while pyridoxine and thiamine are basic. In addition, ascorbic acid is light sensitive and easily oxidized. The extraction strategy employed was a two-step approach using mixed solvents of different polarity and acidity as follows ... 

Many water soluble analytes can be sampled by bubbling the air through water in an impinger. Acid vapors, alkali vapors, or their dusts can be collected in water and their aqueous solutions analyzed by wet methods. Often, water is made basic or acidic to trap acidic or basic analytes, respectively. Other solvents can be used in the impinger, depending on the solubility of the analytes and the vapor pressure of the solvents. Certain organics in the air can also be trapped in impingers if one uses the proper solvents. 

Analytical Procedure Microscopic Examination Place a small amount of a crushed tablet or capsule contents on a slide, mix with a drop of water, and cover carefully with a cover-slip avoiding trapped air bubbles. Observe under low-power magnification. Effervescence will be obvious. If crystalline material is visible, note if it is water-soluble. Check the pH of the solution. An alkaline reaction may indicate the presence of a sodium salt of an acidic drug. Introduce a small drop of silver nitrate solution along one edge of the cover-slip a visible precipitate indicates the possible presence of a hydrochloride salt of a basic drug. 

Liquid chromatography has also been widely used for the determination of dissociation constants [88-92] since it only requires small quantity of compounds, compounds do not need to be pure, and solubility is not a serious concern. However, the effect of an organic eluent modifier on the analyte ionization needs to also be considered. It has been shown that increase of the organic content in hydro-organic mixture leads to suppression of the basic analyte pKa and leads to an increase in the acidic analyte pK compared to their potentiometric pKa values determined in pure water [74]. 

ZrOfHjPO jj.SHjO, a toxic, dense white powder that is insoluble in water, soluble in acids and organic solvents decomposes on heating used as an analytical reagent, coagulant, and ra oactive-phosphor carrier. Also known as basic zirconium phosphate zirconium orthophosphate. 

Extracting solvent To achieve the required selectivity, the most adequate solvent should be chosen. The rule like dissolves like" can be a good approach. Different water-immiscible solvents with different polarity and water solubility can be tested. The solvent must satisfy some basic requirements high surface tension to form a drop, selectivity, extraction efficiency, low volatility, incidence in the drop loss, rate of drop dissolution, and solvent toxicity and its peaks should be well separated from the analyte peaks [211]. 

Analytical work is much aggravated by the different states of preservation of the chemical agents inside and outside of the container walls and by the fact that the assortment includes chemical munitions captured from the Allies as well as German munitions. Nevertheless, because of other priorities, little basic research has been done. Analytical work has been mainly confined to determination of total arsenic, water soluble arsenic, and residual mustard (i.e., that does not pour out). 

C refractive index (20°C) 1.4010 density (20°C) 0.73g/mL viscosity (25°C) 0.36 cP polarity index (P) 1.8 solubility in water (20°C) 5.5% water solubility in triethylamine (20°C) 4.6%. TWethy-lamine is commonly used in reversed-phase HPLC as a basic mobile phase modifier. TEA interacts with residual silanol groups on the support surface and limits the interaction of a basic analyte with these sites thereby decreasing peak taUing. 

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