HPLC methods effects

Therefore, hplc methods seem more effective. By usiag a combiaed uv and electrochemical detection technique (52), the gem-chlotinated cyclohexadienones, the chlorophenols, and the phenoxyphenols present ia the chlorination mixtures can be determined with great accuracy. 

We first note the very large differences in column performance for the two methods. Effective plates per second represents the speed characteristics of a column (e.g., the number of plates that can be generated in a given time interval) (13). As can be seen, HPLC is 100 to 1000 times faster than classTcal LC. (We shall discuss the differences between PLB and PB in the next section.) This improved performance arises mainly from the use of significantly smaller particle sizes in HPLC. Moreover, in classical LC, the mobile phase is delivered to the column by gravity feed, hence, the very low mobile phase velocities. In HPLC, it is desireable to improve performance... 

Parameters that should be tested in HPLC method development are flow rate, column temperature, batch and supplier of the column, injection volume, mobile phase composition and buffer pH, and detection wavelength [2], For GC/GLC methods, one should investigate the effects of column temperature, mobile phase flow rate, and column lots or suppliers [38], For capillary electrophoresis, changes in temperature, buffer pH, ionic strength, buffer concentrations, detector wavelength, rinse times, and capillaries lots and supplier should be studied [35, 36], Typical variation such as extraction time, and stability of the analytical solution should be also evaluated [37],... 

A similar RP-HPLC method has been employed for the determination of the effect of reduced glutathion (GLT) and hydroxypropyL/Tcyclodcxtrin (HP-/LCD) on the stability of the colour pigments of paprika. Samples were prepared by mixing 5 per cent GLT (w/w) and 5 per cent HP-/TCD (w/w) with paprika powder and stored at room temperature (22 1°C) in diffuse light in Petri dishes covered by glass plates. Samples without additives served as a control, lg of paprika was taken after 14, 28, 42 and 56 days of storage... 

The composition and amount of pigments in marine environments have also been vigorously investigated. Thus, on RP-HPLC method has been developed for the study of the effect of variable irradiance on the xanthophyll cycle of the seagrass Zostera marina. Extraction of pigments from seagrass was carried out by grinding the samples with acid-washed sand in the presence of 1 ml of 90 per cent acetone and the liquid phase was... 

An HPLC method was employed for the study of the effect of pH on cream particle formation and solid extraction yield of black tea. Broken black tea (60g) was brewed with 21 of boiling distilled water for lOmin then filtered. After cooling down, pH of aliquots of 45 ml were adjusted to 1.2, 2, 3, 7, 9, 11 and 13 with 3 M HC1 and NaOH, respectively. 

An RP-HPLC method was employed for the investigation of the effect of solar light and TiOz on decomposition of the textile dye Reactive blue 4 (RB4). The chemical structure of Reactive blue 4 is shown in Fig. 3.51. RP-HPLC measurements were performed in an ODS column. Chromatographic profiles demonstrating the effect of irradiation time and the... 

Lewis, E.R., Johansen, E. and Holman, T.R. (1999). Large competitive kinetic isotope effects in human 15-Upoxygenase catalysis measured by a novel HPLC method. J. Am. Chem. Soc. 121, 1395-1396... 

Dreux M, Lafosse M, Gilbert M, et al. 1985. Analytical determination of inorganic chlorination products in water treatment by an HPLC method. In Jolley RL, Bull RJ, Davis WP, et al., eds. Water chlorination-Chemistry, environmental impact and health effects. Vol. 5. Williamsburg, VA Lewis Publishers, Inc. 

The CLD methods for HPLC using isoluminol (190) with microperoxidase catalysis, for determination of lipid hydroperoxides in clinical fluids, have been reviewed. Determination of phospholipids hydroperoxides by luminol (124) CL has been reviewed . A fast RP-HPLC method (retention times 1 to 2 min) for determination of hydroperoxides and other peroxide compounds includes UVD, which is not always effective, and CLD, attained on injection of luminol (124), the CL reagent (Scheme 3), hemin (75a), a catalyst, and NaOH to raise the pH of the solution. A FLD cell may act as CLD cell if the excitation source is turned off. The selectivity of CLD is of advantage over UVD in industrial analysis thus, for example, UVD of a sample from a phenol production line based on cumene oxidation (equation 13) shows peaks for cumyl hydroperoxide (27), unreacted cumene, cumyl alcohol and acetophenone, whereas CLD shows only the 27 peak. The... 

The RP-HPLC method based on the CL reaction of luminol (124) catalyzed by Co(II) (Section in.B.2.c) can be applied for determination of peroxycarboxylic acids, esters and diacyl peroxides (see examples of LOD in equation 67, Section V.B.2.c) . The biosensor prepared according to equation 70, that is effective in the determination of hydroperoxides (Section V.B.6.b), becomes deactivated after three days of operation when trying to determine t-butyl peracetate. ... 

A stability-indicating HPLC method has been described for isoxsuprine [11]. The mobile phase consisted of methanol / pH 7 phosphate buffer, and detection was effected on the basis of the absorbance at 276 nm. 

Another reversed phase HPLC method reported the use of a Spherisorb column to effect the analytical separation [34]. The mobile phase consisted of methanol, to which perchloric acid was added at a level of 100 pL/L. The k value was reported to be 0.8. 

---