Radial compression

It is thus evident that the experimental results considered in sect. 4 above are fully consistent with the interpretation based on absolute reaction rate theory. Alternatively, consistency is equally well established with the quantum mechanical treatment of Buhks et al. [117] which will be considered in Sect. 6. This treatment considers the spin-state conversion in terms of a radiationless non-adiabatic multiphonon process. Both approaches imply that the predominant geometric changes associated with the spin-state conversion involve a radial compression of the metal-ligand bonds (for the HS -> LS transformation). 

Radial compression columns are used by Waters Associates (see section 4.3.1) [144-146,603]. A flexible-walled plastic... 

The Waters system uses a plastic cartridge which is inserted into a device (the Z-module) that subjects the column to radial compression, ie pressure is applied along the radial axis of the column tube. The flexible wall of the column then moulds itself into the voids that are present in the wall regions of the column. This method is claimed to produce an improvement in the packed bed structure, better column performance and longer useful column life. 

Turner and Warnock [56] determined miconazole in human saliva using high performance liquid chromatography. Deproteinated human saliva samples containing miconazole was chromatographed on a C8 reversed-phase radial compression column using 77% methanol in 0.01 M EDTA with 0.005 M w-nonylamine at a flow... 

Apparatus. The HPLC instrument used was a Water s Associates model 6000A pump for the solvent supply, a U6K septumless injector and a radial compression module with standard Radial Pak columns. Immediately after the column a low dead volume tee was inserted and another 6000A pump was used to deliver a solution of OPT for the post-column derivatization of histamine. Twenty feet of 9 thousandths (id) coiled stainless steel tubing was used as a mixing chamber and held at 60 C in a water bath. The reaction mixture then passed through a Water s 420 fluorescence detector which was connected to a recorder. The detector was equipped with a 340-nm excitation filter and a 440-nm emmission filter. 

The radial (compressive) stress, qo, is caused by the matrix shrinkage and differential thermal contraction of the constituents upon cooling from the processing temperature. It should be noted that q a, z) is compressive (i.e. negative) when the fiber has a lower Poisson ratio than the matrix (vf < Vm) as is the normal case for most fiber composites. It follows that q (a,z) acts in synergy with the compressive radial stress, 0, as opposed to the case of the fiber pull-out test where the two radial stresses counterbalance, to be demonstrated in Section 4.3. Combining Eqs. (4.11), (4.12), (4,18) and (4.29), and for the boundary conditions at the debonded region... 

Bushway, R. J. (1982). High-performance liquid chromatographic separation of potato glycoalkaloids using a radially compressed amino column. J. Chromatogr., 247,180-183. 

In the initial phases of the analytical method development a Waters Associates C-jq y-Bondapak column was used. With certain dyes, such as C.I. Direct Black 38, aniline is used as a terminal group (Figure 1). This column caused the benzidine peak of the reduced dye to obscure a peak due to aniline. If these two compounds were not resolved, the method could not differentiate between benzidine-based and aniline-based dyes. This problem was removed by use of the Waters Radial Compression Module Model RCM 100 with a Radial Pak A cartridge. 

The majority of published HPLC techniques used in fat-soluble vitamin assays have utilized 5- or 10-/zm particles of porous silica or derivatized silica packed into stainless steel tubes of typical length of 250 mm and standard internal diameter (ID) of 4.6 mm. Radially compressed... 

For the determination of supplemental vitamin E in infant formulas, Woollard and Blott (222) employed a radially compressed Radial-PAK cartridge. This enabled lipid material to be rapidly cleared by stepping up the mobile-phase flow rate from 2 ml/min to 10 ml/min after elution of the a-tocopheryl acetate. Fluorescence detection, using a filter-type fluorometer, allowed the indigenous a-tocopherol to be conveniently estimated, while UV absorbance detection was used to quantify the a-tocopheryl acetate. Supplemental retinyl acetate could be assayed simultaneously with either added or indigenous vitamin E using the appropriate detection mode. With the aid of a dual-monochromator spectrofluorometer, a-tocopheryl acetate and a-tocopherol could be determined simultaneously with wavelengths of 280 nm (excitation) and 335 nm (emission), but the increased selectivity eliminated detection of the vitamin A esters (233). 

Methanol/water/ phosphoric acid 100 X 8-mm-ID NovaPak C18 5-/on cartridge under radial compression No Ambient 313 28... 

Fig. 3 Resolution of the six major iso-a-acids in beer into five bands by reverse-phase HPLC. Mobile phase acetonitrile water methanol 0.2 M magnesium acetate (aq) formic acid trifluoroacetic acid (840 490 480 24 3.6 1.2 v/v/v/v/v/v). Column NovaPak C18 5 /rm cartridge (100 X 8 mm i.d.) under radial compression. Mobile phase flow rate = 2 ml min-1. (Chromatogram redrawn from original).

A calculated radial compressive stress of 246 MPa on the fibre (corresponding to a frictional stress as large as 24.6 MPa) was obtained by Yu et al. (2002b), which was big enough to cause the SiC fibres to break when they were torn from the a-sialon matrix. 

Pietrzyk, D.J. and Cahill, W.J., Amberlite XAD-4 as a stationary phase for preparative liquid chromatography in a radially compressed column, J. Liq. Chromatogr., 5, 781, 1982. 

J. S. Landy, J. L. Ward, and J. G. Dorsey, A critical evaluation of some stainless steel and radially compressed reversed-phase HPLC columns, J. Chromatogr. Sci., 21 45 (1983). 

Columns made of glass and Kel-F with operating pressures of up to 4000 psi have been manufactured. Radially compressed plastic cartridges containing sorbent are also a viable alternative [40]. 

Using a radial compression Q8 column and a mobile phase of aqueous tetramethylammonium phosphate Kok et al. [320] analysed mixtures of nitrate and nitrite at the O.lmg L 1 level (3a) and compared the results obtained with those found by ultraviolet spectroscopic screening methods. 

---