Chromatographic measurement

In a series of papers published throughout the 1980s, Colin Poole and his co-workers investigated the solvation properties of a wide range of alkylammonium and, to a lesser extent, phosphonium salts. Parameters such as McReynolds phase constants were calculated by using the ionic liquids as stationary phases for gas chromatography and analysis of the retention of a variety of probe compounds. However, these analyses were found to be unsatisfactory and were abandoned in favour of an analysis that used Abraham s solvation parameter model [5]. 

Where FCl is the solute gas-liquid partition coefficient, r is the tendency of the solvent to interact through k- and n-electron pairs (Lewis basicity), s the contribution from dipole-dipole and dipole-induced dipole interactions (in molecular solvents), a is the hydrogen bond basicity of the solvent, b is its hydrogen bond acidity and I is how well the solvent will separate members of a homologous series, with contributions from solvent cavity formation and dispersion interactions. 

Some exceptions to this general observation were found halide and nitrite salts have unusually high hydrogen-bond basicities (as would be expected), while penta-cyanopropionide, picrate, triflate, and perfluorobezenesulfonate salts not only had unusually low hydrogen-bond basicities (also as would be expected) but also lower s values, perhaps due to the weakening of the Coulombic interactions by delocalization of the charge on the anions. 

It was noted that, on going from tetrabutylammonium to tetrabutylphosphoni-um, salts with a common anion displayed identical solvation properties. FLence, with these simple cations, the solvent properties are dominated by the choice of anion. It is possible that, had cations with acidic protons, such as triallcylammoni-um and trialkylphosphonium, been included in the study, these may then have also had an influence. 

Finally, none of the ionic liquids were found to be hydrogen bond acids [5], although this may well be a consequence of the salts selected, none of which had a cation that would be expected to act as a hydrogen bond donor. Earlier qualitative measurements on ionic liquid stationary phases of mono-, di-, and trialkylammo-nium salts suggest that hydrogen bond donation can be important where a potentially acidic proton is available [7-9]. More recent work, with [BMIM] salts, also indicates that these ionic liquids should be considered to be hydrogen bond donor solvents [10]. However, this has yet to be quantified. 

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Hafnium metal is analy2ed for impurities using analytical techniques used for 2irconium (19,21,22). Carbon and sulfur in hafnium are measured by combustion, followed by chromatographic or in measurement of the carbon and sulfur oxides (19). Chromatographic measurement of Hberated hydrogen follows the hot vacuum extraction or fusion of hafnium with a transition metal in an inert atmosphere (23,24). 

As already mentioned, there are two so called "dead volumes" that are important in both theoretical studies and practical chromatographic measurements, namely, the kinetic dead volume and the thermodynamic dead volume. The kinetic dead volume is used to calculate linear mobUe phase velocities and capacity ratios in studies of peak variance. The thermodynamic dead volume is relevant in the collection of retention data and, in particular, data for constructing vant Hoff curves. 

In their work on the precision of contemporary liquid chromatographic measurements, Scott and Reese (3) also evaluated the precision that could be expected from a computer measuring peak heights and peak areas. They again used twelve replicate samples and the results they obtained are shown in table 2. 

For the NO+propene reaction the values were obtained directly from experiment by gas chromatographic measurement of the N2 production. 

Quantitation is performed by the calibration technique. Prepare a calibration curve by injecting pyrithiobac-methyl standard solutions, equivalent to 0.2,0.5,1.0,2.0,3.0 and 4.0 ng, into the gas chromatograph. Measure the heights of the peaks obtained. Plot the peak heights in millimeters against the injected amounts of pyrithiobac-methyl in nanograms. 

Experimental variables such as temperature, flow rate, sample concentration and mobile phase composition can cause changes in the elution volume of a polymer [439,457,460-464]. Chromatographic measurements made with modem equipment are limited more by the errors in the absolute methods used to characterize the molecular weight of the calibration standards than any errors Inherent in the measurements themselves, since the determination of molecular weights by SEC is not an absolute method and is dependent on calibration [462]. The Influence of temperature on retention in SEC is not very great, since no strong sorptive interactions are involved in the retention mechanism. Temperature differences between the column and solvent delivery... 

Torsi, G., Chiavari, G., Laghi, C., and Asmudsdottir, A., Responses of different UV-visible detectors in high-performance liquid chromatographic measurements when the absolute number of moles of an analyte is measured, /. Chromatogr., 518, 135, 1990. 

Janos, R, Determination of stability constants of metal complexes from ion chromatographic measurements, /. Chromatogr., 641, 229, 1993. 

Wyatt, P. J., Hicks, D. L., Jackson, C., and Wyatt, G. K., Absolute gel permeation chromatographic determination of molecular weight and sizes. Part 2. Incorporation of gel permeation chromatography-size exclusion chromatographic measurements, Am. Lab., 20, 108, 1988. 

Ong, S. Liu, H. Qiu, X. Bhat, G. Pidgeon, C., Membrane partition coefficients chromatographically measured using immobilized artificial membrane surfaces, Anal. Chem. 67, 755-762 (1995). 

The determination of acrylonitrile in air may be accomplished by collection on a solid sorbet, such as activated charcoal, followed by elution and gas chromatographic measurement (NIOSH 1984). 

Hamilton, D. J. (1980) Gas chromatographic measurement of volatility of herbicide esters. J. Chromatogr. 195, 75-83. 

Jenke, D.R., Hayward, D.S., Kenley, R.A. (1990) Liquid chromatographic measurement of solute/solvent partition coefficients application to solute/container interactions. J. Chromatogr. Sci. 20, 609-6612. 

An increase in absorbance at 351 nm and a concomitant decrease in absorbance at 380 nm in the ultraviolet visible spectrum of methylcobalamin during the abiotic transfer of the methyl group to Hg2+ are characteristic for the loss of the methyl group and formation of aquocobalamin. In experiments monitored by both analytical techniques, gas chromatographic measurements of methylmercury formation were in good agreement with the spectropho-tometric measurement of aquocobalamin formation from methylcobalamin at 351 nm. Aerobic versus anaerobic reaction conditions had no measurable effect on either the methyl transfer rates, the stability of the reactants, or on the reaction products. 

Yang, Q., Liu, X. Y., Umetani, K., Kamo, N. and Miyake, J. (1999). Partitioning of triphenylalkylphosphonium homologues in gel bead-immobilized liposomes chromatographic measurement of their membrane partition coefficients, Biochim. Biophys. Acta-Biomem., 1417, 122-130. 

Another RP-HPLC method was applied for the investigation of the effect of TiOz on the photocatalytic degradation of the leather dye Acid brown 14. The chemical structure of Acid brown 14 is shown in Fig. 3.54. Chromatographic measurements were performed in an ODS column using methanol-water (10 90, v/v) as the mobile phase. The flow rate was 1 ml/min and analytes were detected at 212 nm. The results demonstrated that Acid brown 14 is rapidly decomposed under solar light in the presence of a Ti02 photocatalyst [125],... 

The effect of nanoporous Ti02 thin-film electrodes on the removal and degradation of the reactive textile dye Reactive orange 16 (R3R) was investigated by physicochemical analytical procedures including RP-HPLC. The chemical structure of the dye is shown in Fig. 3.67. Liquid chromatographic measurements were employed for the separation and detection of the decomposition products of the dye. They were realized in an ODS column... 

RP-HPLC was also employed for the investigation of the hydrolysis behaviour of two fluorotriazine reactive dyes Cibacron blue F-R and Cibacron yellow F-4G. Chromatographic measurements were performed in an ODS column (50 X 4.6 mm i.d. particle size 5 /jm) at room temperature. The mobile phase was ACN-0.05 M ammonium acetate buffer containing 1 mM acetyhrimethylammonium bromide (47 53, v/v). Flow rates were 0.8 and 0.6 ml/min depending on the dyes to be separated. Dyes were detected at 275 nm. The hydrolysis of dyes was investigated both in the absence and presence of... 

The effect of biofilters has been studied by Kowalewsky (4). In these studies he used both Dragerrof as well as photometric and gas chromatographic measurements to study the reduction of certain odours such as ammonia and hydrogen sulphide. The measurements showed that the concentration of the gases studied decreased by, on average, 50%. When the moisture content of the filter was at an optimum level the reduction was 80%. 

Gel permeation chromatographic measurements were performed oj a Waters Associates HPLC with i-Styragel columns (10, 10, 10, and 500ANG) in chloroform with a polystyrene calibration. 

Hue B, Palomba B, Giacardy-Paty M, Bottai T, Alric R, et al. 1998. Concurrent high-performance liquid chromatographic measurement of loxapine and amoxapine and of their hydroxylated metabolites in plasma. Ther Drug Monit 20(3) 335-339. 

Kaune, A., Bruggemann, R., and Kettrup, A. High-performance liquid chromatographic measurement of the 1-octanol-water partition coefficients of s-triazine herbicides and some of their degradation products, J. Chromatogr. A, 805 (1-2) 119-126. 1998. 

The molar fraction ratio between helium and nitrogen in the flue gas was determined from gas chromatographic measurements. The molar flow of the tracer gas of helium was measured. Because Rogers applied batch methods to measure water vapour in flue gas and the helium-nitrogen ratio, the overall method become a semi-continuous method. The water vapour of the flue gas was measured batchwise by freezing it out in an U-tube placed in an acetone-dry ice mixture. 

The contributions of L.A.J. Swerts and J. Boven, who performed the chromatographic measurements and extraction probe synthesis, respectively, are gratefully acknowledged. 

Chromatographic measurements discussed here are based on the evaluation of the effect of the concentration of the complexing agent (hetaeron) in the eluent on the retention factor of the eluite aS treated in Section VI. If the stoichiometry of the hetaeron-solute association process is 1 1. then Eq. (89) of Section VI can be used to calculate the retention factor. A more general expression is available for the scheme presented in Fig. 59. In view of the equilibria involved mass balance yields an expression for the retention factor as follows... 

Abraham, M.H., Ibrahim, A. and Zissimos, A.M. (1037) Determination of sets of solute descriptors from chromatographic measurements. Journal of Chromatography. A, 2004, 29-47. 

Table 2.1 Enantiomeric ratios (E) obtained in hydrolysis of butanoates la-15a and transesterifrcation of alcohols lb-9b and 13b-15b using 2-chloroethyl butanoate as acyl donor and lipase B from Candida antarctica (CALB) as catalyst. For significance of and R2 see Figure 2.9. F-values were determined from chromatographically measured ee and ee at several degrees of conversion and using the computer program E K calculator version 2.03. Note that the stereopreference of CALB changes from (R) to (S) when R2=F, ClandBr.

The capacity ratio of a solute, (k ), was introduced to develop a chromatographic measurement, simple to calculate, independent of flow-rate and one that could be used in solute identification. Although helpful, the capacity ratio is so dependent on the accurate measurement of extra column volume and on very limited solute exclusion by the support and stationary phase, that it is less than ideal for solute identification. An alternative measurement, the separation ratio (a) was suggested where, for two solutes (A) and (B),... 

Reaction 1, in which 02 evolves from superconductor when it is dissolved in acid, is the basis for another analytical procedure useful for YBa2Cu307 x when the oxygen content is greater than 6.5. Methods have been described involving volumetric (27)(28) or gas chromatographic measurement (29) of the evolved oxygen. 

Figure 3 System for gas chromatographic measurement of Oz evolution from superconductors dissolved in acid (29) (A) enlarged view of reaction flask, (B) circulating system including flask (G), NaOH U-tube (T), three-way valves (S), 1 mL loop (L), pulse pump (PP) and vacuum system (V), At the right is the gas chromatograph (G.C.). (From Reference 29. With Permission.)...

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