Multi-anion analysis

Liquid membrane anion ion-exchanger type sensors are best illustrated by the nitrate ISE (95-96). This has seen a role in the environmental screening of waters and effluents (97,) fo> nitrate, but such use has been somewhat diminished by the high sensitivity and facility for multi-ion analysis of the newer approach of ion-chromatography. 

Figure 2.1 Ion chromatograms obtained with Dionex instrument using (anodic) AMMS and CMMS micromembrane suppression, (a) anions with micromembrane suppressor (b) multi-component analysis by ion chromatography. Source Author s own files)...

Gonzalez et al. [8] have applied micelle analysis in the kinetic multi-component analysis for the simultaneous determination of thiocyanate, sulphite and sulphide in non saline waters. The method involved reaction of the anions with S,S dithiobis(2-nitrobenzoic acid) in aqueous cetyl-trimethyl ammonium bromide micelles. Cyanide, sulphide and sulphite were determined at concentrations, respectively, down to 0.5-1.5 x 10 0.2-1 X 10 and 0.2-1.5 X 10 with a relative error of less than 5%. 

New methodologies for the laboratory analysis of cations and metals include the use of inductively coupled plasma emission spectrometry (ICP/ES) or the combinahon of ICP with mass spectrometry (ICP/MS) (e.g., Ivahnenko et al., 2001). The advantages of plasma techniques include (i) a wide and linear dynamic concen-trahon range (ii) multi-element capabihty and (iii) relatively free of matrix interferences. The use of ion chromatography (1C), gas chromatography (GC), and GC/MS has increased for the analysis of anions and dissolved organics (Barth, 1987 Kharaka and Thordsen, 1992 Ivahnenko et al., 2001). 

This is not the case for both cationic and anionic compounds which are difficult to remove from peptide mixtures even after multi-stage purification. Hence, they can still be present in the final MS analysis step, and this results in significant suppression of ESI-MS peptide ion current (7). 

C. Pons, R. Forteza, V. Cerda, The use of anion-exchange disks in an optrode coupled to a multi-syringe flow-injection system for the determination and speciation analysis of iron in natural water samples, Talanta 66 (2005) 210. 

HPTS fluorescence has been employed in the study of proton diffusion within inverted micelles [24], in liposomes [4a], in apomyoglobin and the inter-membranal hydration layers of multi-lamellar vesicles [4b]. The simplest case for analysis involves the HPTS molecule in the center of a sphere (inverted micelle, liposome) whose walls are impermeable to protons on the timescale of the experiment. This outer wall is therefore described by an additional reflective boundary condition. Inside such a sphere, even a single proton/anion pair ultimately reaches an equilibrium situation The long-time tail approaches a plateau, rather than decaying to zero. The smaller the radius of the sphere, the higher the expected asymptotic plateau. 

Ion chromatography can also be applied for ultra-trace analysis of transition metals. In comparison to ICP-MS it offers the advantageous ability to specify the oxidation state of metals and, moreover, to carry out multi-element determinations in the lowest ng/L range after pre-concentration. Transition metal separation is performed with ion exchangers that have defined anion and cation exchange capacities detection is carried out photometrically after derivatization... 

Dabre R, Azad N, Schwaemmle A, Laemmerhofer M, Lindner W. Simultaneous separation and analysis of water- and fat-soluble vitamins on multi-modal reversed-phase weak anion exchange material by HPLC-UV. J. Sep. Sci. 2011 34 761-772. 

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