Columns Complexing acids

Oxine (5) fonns complexes of analytical applicability with various metal ions. A RP-HPLC-FLD method (Xex = 370 nm, Xg = 516 nm) was proposed for simultaneous determination of Al(III) and Mg(II), using a Cjg column. Various details of the method are noteworthy Optimization of the method showed that for both ions it is best to have also precolumn and in-column complex formation, caused by the presence of 5 in the injection loop and in the carrier solution FLD detection is preferable to simple UVD because it avoids the background of 5 and interference of various ions forming nonfluorescent chromogenic complexes, e.g. Ca(II) and Zn(II) the intensity of the fluorescence can be increased by micelle formation on addition of SDS and neutralized Af,Af-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid (6). The LOD (SNR = 3) were 0.74 (xM (18 ppb) Mg(n) and 0.60 (xM (16 ppb) Al(III) the latter was attributed in part to residual impurities in the purified water -... 

Several inorganic acids exhibit a complexing effect for metal ions. The complexing acids include HF, HCI, HBr, HI, HSCN, and H2SO4. The complexed metal ions are converted into neutral or anionic complexes and are rapidly eluted, while the other cations remain on the cation-exchange column. 

Some of the most successful separations of metals have been on anion exchange columns. A complexing acid is added in high concentration to form anionic complexes of the metals. Concentrated hydrochloric acid forms anionic chloro-complexes with all the common metals, with the exception of the alkali and alkaline earth metals and A1(III), Ni(II), and Cr(III), and so all of these can be adsorbed on a quaternary ammonium anion exchange column. 

The most commonly used method for the analysis and purification of peptides mixtures is reversed-phase liquid chromatography (RPLC). The experimental system usually comprises an -alkylsilica-based stationary phase material from which peptides are eluted with gradients of increasing concentration of acetonitrile in the presence of ionic modifier, e.g., trifluoroacetic acid (TFA). With modern instrumentation and columns, complex mixtures of peptides can be separated and low picomole amounts of resolved components can be collected. Separations can be easily manipulated by changing the gradient slope... 

Bentone-34 has commonly been used in packed columns (138—139). The retention indices of many benzene homologues on squalane have been determined (140). Gas chromatography of C —aromatic compounds using a Ucon B550X-coated capillary column is discussed in Reference 141. A variety of other separation media have also been used, including phthaUc acids (142), Hquid crystals (143), and Werner complexes (144). Gel permeation chromatography of alkylbenzenes and the separation of the Cg aromatics treated with zeofltes ate described in References 145—148. 

Modem commercial wet-acid purification processes (see Fig. 4) are based on solvents such as C to Cg alcohols, ethers, ketones, amines, and phosphate esters (10—12). Organic-phase extraction of phosphoric acid is accompHshed in one or more extraction columns or, less frequently, in a series of countercurrent mixer—settlers. Generally, 60—75% of the feed acid P2 s content is extracted into the organic phase as H PO. The residual phosphoric acid phase (raffinate), containing 25—40% of the original P2O5 value, is typically used for fertilizer manufacture such as triple superphosphate. For this reason, wet-acid purification units are almost always located within or next to fertilizer complexes. 

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