Columns potentiometric

Preconcentration carried out with Metrosep A PCC 1 HC column Complexation of SRP with Molybdenum Blue reagent Phosphomolybdenum complex H3P04(Mo03)i2 Use of 2 precolumns and 2 injector valves to elute excess chloride to waste prior to redirection to analytical column Potentiometric titration of sulphate with lead perchlorate to remove sulphate and boost phosphate sensitivity... 

Titrate the effluent from the cation-exchange column potentiometrically with ethanolic 0.1 M sodium hydroxide through two points of inflection at pHs below and above 7. 

Dissolve 20 g of tetra-n-butylammonium iodide in 100 mL of dry methanol and pass this solution through the column at a rate of about 5 mL min - L the effluent must be collected in a vessel fitted with a Carbosorb guard tube to protect it from atmospheric carbon dioxide. Then pass 200 mL of dry methanol through the column. Standardise the methanolic solution by carrying out a potentiometric titration of an accurately weighed portion (about 0.3 g) of benzoic acid. Calculate the molarity of the solution and add sufficient dry methanol to make it approximately 0.1M. 

Many IC techniques are now available using single column or dual-column systems with various detection modes. Detection methods in IC are subdivided as follows [838] (i) electrochemical (conductometry, amper-ometry or potentiometry) (ii) spectroscopic (tJV/VIS, RI, AAS, AES, ICP) (iii) mass spectrometric and (iv) postcolumn reaction detection (AFS, CL). The mainstay of routine IC is still the nonspecific conductometric detector. A significant disadvantage of suppressed conductivity detection is the fact that weak to very weak acid anions (e.g. silicate, cyanide) yield poor sensitivity. IC combined with potentiometric detection techniques using ISEs allows quantification of selected analytes even in complex matrices. The main drawback... 

Vol. 66 Solid Phase Biochemistry Analytical and Synthetic Aspects. Edited by William H. Scouten Vol. 67 An Introduction to Photoelectron Spectroscopy. By Pradip K. Ghosh Vol. 68 Room Temperature Phosphorimetry for Chemical Analysis. By Tuan Vo-Dinh Vol. 69 Potentiometry and Potentiometric Titrations. By E. P. Serjeant Vol. 70 Design and Application of Process Analyzer Systems. By Paul E. Mix Vol. 71 Analysis of Organic and Biological Surfaces. Edited by Patrick Echlin Vol. 72 Small Bore Liquid Chromatography Columns Their Properties and Uses. Edited by Raymond P.W. Scott... 

After passing through the column, the separated solutes are sensed by an in-line detector. The output of the detector is an electrical signal, the variation of which is displayed on a potentiometric recorder, a computing integrator or a vdu screen. Most of the popular detectors in hplc are selective devices, which means that they may not respond to all of the solutes that are present in a mixture. At present there is no universal detector for hplc that can compare with the sensitivity and performance of the flame ionisation detector used in gas chromatography. Some solutes are not easy to detect in hplc, and have to be converted into a detectable form after they emerge from the column. This approach is called post-column derivatisation. 

Ishibashi et al. devised a potentiometric sensor for the determination of non-ionic surfactants which they improved in several steps. Initially, the authors used a sensor based on a PVC membrane plasticized with 2-nitro-phenyl octyl ether that was responsive to cationic complexes formed between a dissolved metal ion and non-ionic surfactants in the sample [116]. At a later stage, they studied the effect of foreign species and elucidated the perturbation from ionic surfactants [117], which they eventually overcame by inserting an ion-exchange column into the base system [118]. 

In the method proposed by van Staden for the determination of three halides, these are separated in a short colunm packed with a strongly basic ion-exchange resin (Dowex i-X8) that is placed in an FI manifold. A laboratory-made tubular silver/silver halide ion-selective electrode is used as a potentiometric sensor. Van Staden compared the response capabilities of the halide-selective electrodes to a wide concentration range (20-5000 pg/mL) of individual and mixed halide solutions in the presence and absence of the ion-exchange column. By careful selection of appropriate concentrations of the potassixun nitrate carrier/eluent stream to satisfy the requirements of both the ion-exchange column and the halide-selective electrode, he succeeded in separating and determining chloride, bromide and iodide in mixed halide solutions with a detection limit of 5 /xg/mL [130]. 

Elemental composition H 1.25%, Br 98.75%. The normality of the acid may be measured by titration against a standard solution of a base using a suitable color indicator or by potentiometric titration. The bromide ion, Br, may be measured quantitatively by ion chromatography after appropriate dilution. Concentration of HBr gas in air may be measured by passing a known volume of air through water and determining concentration of acid in aqueous solution by titration or ion chromatography. Alternatively, HBr gas may be analyzed by GC or GC/MS. A very polar column should be used for such measurements. An FID or a TCD type detector may be used for GC analysis. 

Elemental composition H 5.04%, F 94.96%. The total acidity of an aqueous HF solution may be measured by titration with a standard solution of base using phenolphthalein or another suitable color indicator. Alternatively, the end point may be determined by potentiometric titration. The fluoride ion may be analyzed using a fluoride ion-selective electrode or by ion chromatography. The HF gas may be analyzed by GC/MS using a GC column having... 

Nitrogen pentoxide may be dissolved in water and the aqueous solution analyzed for nitric acid by acid-base titration or potentiometric titration. Alternatively, the oxide is dissolved in chloroform, diluted appropriately, and analyzed by GC/MS using a polar GC column. 

The values given in column 3 of Table IV were obtained from the data in column 2 ((2) and (6)]. A comparison of the results for 14 and 15 indicates that the introduction of methyl groups at sites 4 and 5 (see 12), leading to central chirality R at both carbon atoms, is the main cause of enantiomer selectivity. This is in agreement with the only slightly different enantiomer selectivity of 16 relative to 15. As expected, the effect of 17 is reversed by 18. Although valinomycin 1 is chiral, no enantiomer selectivity was detectable (see Table IV). The potentiometrically determined enantiomer selectivity AEMF is correlated to the transport selectivity [(2), (6), (10), and (11)]... 

Fig. 18. An ion exchange reaction followed acoustically via a microphone attached to the outside of the column and potentiometrically via an ion-selective electrode in the effluent (solid line — electrode response dotted line — integrated acoustic energy). Inset The raw plot of acoustic power versus time...

It would be necessary to decouple the radio frequency to prevent it interfering with the function of the potentiometric recorder (or signal processing amplifier). The resistance capacity decoupling shown in their circuit appears hardly sufficient to achieve this in a satisfactory manner and consequently, the circuit shown in figure 11 may be only schematic. The column was connected directly to the sensor and the eluent passed through the annular channel between the central electrode and the sensor wall. 

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