Anion trace

Kfivankova, L., Pantiickova, P., Gebauer, P., Bocek, P., Caslavska, J., and Thormann, W. (2003). Chloride present in biological samples as a tool for enhancement of sensitivity in capillary zone electrophoretic analysis of anionic trace analytes. Electrophoresis 24, 505—517. 

Most recently, it was found that the thermal stability of geminal dicationic ILs is considerably higher than their monocationic analogs [22]. Figure 4.1 illustrates the increase in thermal stability of dicationic ILs containing the [TfjN] anion (traces D-G) compared to the monocationic l-butyl-3-methyl-imidazolium ILs containing Cl , PF, and TfjN anions. 

Figure 11 Analysis of a human serum by capillary zone electrophoresis with inherent transient isotachophoretic stacking of analytes. The BGE co-ion, mandelate, acts as terminator in the system where chloride surplus present naturally in the sample acts as the leading type stacker and conditions for transient isotachophoretic stacking of phosphate, citrate, malate, and acetoacetate with mobilities between chloride and mandelate are ensured. BGE is composed of 5 mmol r mandelic acid-h e-aminocaproic acid, pH 3.8. Reprinted with permission from Kfivankova L, Pantuckova P, Gebauer P, et al. (2003) Chloride present in biological samples as a tool for enhancement of sensitivity in capillary zone electrophoretic analysis of anionic trace analytes. Electrophoresis 24 515.)...

Heumann, K.G. Schindlmeier, W. Zeininger, H. Schmidt, M. Application of an Economical and Small Thermal Ionization Mass Spectrometer for Accurate Anion Trace Analyses. Fresenius Zeitschrift fur Analytische Chemie 1985, 520,457-462. 

Unless the p keto ester can form a stable anion by deprotonation as m step 4 of Figure 21 1 the Claisen condensation product is present m only trace amounts at equi librium Ethyl 2 methylpropanoate for example does not give any of its condensation product under the customary conditions of the Claisen condensation... 

Ethyl 2 2 4 tnmethyl 3 oxopentanoate (cannot form a stable anion formed in no more than trace amounts)... 

Control led-Potential Coulometry The majority of controlled-potential coulometric analyses involve the determination of inorganic cations and anions, including trace metals and halides. Table 11.8 provides a summary of several of these methods. 

Suitable catalysts include the hydroxides of sodium (119), potassium (76,120), calcium (121—125), and barium (126—130). Many of these catalysts are susceptible to alkali dissolution by both acetone and DAA and yield a cmde product that contains acetone, DAA, and traces of catalyst. To stabilize DAA the solution is first neutralized with phosphoric acid (131) or dibasic acid (132). Recycled acetone can then be stripped overhead under vacuum conditions, and DAA further purified by vacuum topping and tailing. Commercial catalysts generally have a life of about one year and can be reactivated by washing with hot water and acetone (133). It is reported (134) that the addition of 0.2—2 wt % methanol, ethanol, or 2-propanol to a calcium hydroxide catalyst helps prevent catalyst aging. Research has reported the use of more mechanically stable anion-exchange resins as catalysts (135—137). The addition of trace methanol to the acetone feed is beneficial for the reaction over anion-exchange resins (138). 

When dissolved ia water, the solution is identical with that obtained by dissolving sodium carbonate ia aqueous hydrogen peroxide. There is some evidence for the presence of the traces of tme peroxocarbonate anion, HCO , ia these solutions (95). If the peroxohydrate is heated for about an hour at 100°C and then allowed to cool to room temperature, some decomposition occurs and the product effervesces when placed ia water. Electron spia resonance experiments (64) iadicate that free radicals are present ia this partially decomposed material, but the nature of these radicals is obscure. 

The sodium hydroxide is titrated with HCl. In a thermometric titration (92), the sibcate solution is treated first with hydrochloric acid to measure Na20 and then with hydrofluoric acid to determine precipitated Si02. Lower sibca concentrations are measured with the sibcomolybdate colorimetric method or instmmental techniques. X-ray fluorescence, atomic absorption and plasma emission spectroscopies, ion-selective electrodes, and ion chromatography are utilized to detect principal components as weU as trace cationic and anionic impurities. Eourier transform infrared, ft-nmr, laser Raman, and x-ray... 

Reactions of alkylazoles involving traces of reactive anions... 

In aqueous or alcoholic solution, certain alkylazoles react with bases to give traces of anions of type (367). With suitable electrophilic reagents, these anions undergo reasonably rapid and essentially non-reversible reaction. 

By using an anionic collector and external reflux in a combined (enriching and stripping) column of 3.8-cm (1.5-in) diameter with a feed rate of 1.63 ni/n [40 gal/(h ft )] based on column cross section, D/F was reduced to 0.00027 with C JCp for Sr below 0.001 [Shou-feld and Kibbey, Nucl. AppL, 3, 353 (1967)]. Reports of the adsubble separation of 29 heavy metals, radioactive and otheiwise, have been tabulated [Lemlich, The Adsorptive Bubble Separation Techniques, in Sabadell (ed.), Froc. Conf. Traces Heavy Met. Water, 211-223, Princeton University, 1973, EPA 902/9-74-001, U.S. EPA, Reg. 11, 1974). Some separation of N from by foam fractionation has been reported [Hitchcock, Ph.D. dissertation. University of Missouri, RoUa, 1982]. 

The aqueous micellai solutions of some surfactants exhibit the cloud point, or turbidity, phenomenon when the solution is heated or cooled above or below a certain temperature. Then the phase sepai ation into two isotropic liquid phases occurs a concentrated phase containing most of the surfactant and an aqueous phase containing a surfactant concentration close to the critical micellar concentration. The anionic surfactant solutions show this phenomenon in acid media without any temperature modifications. The aim of the present work is to explore the analytical possibilities of acid-induced cloud point extraction in the extraction and preconcentration of polycyclic ai omatic hydrocai bons (PAHs) from water solutions. The combination of extraction, preconcentration and luminescence detection of PAHs in one step under their trace determination in objects mentioned allows to exclude the use of lai ge volumes of expensive, high-purity and toxic organic solvents and replace the known time and solvent consuming procedures by more simple and convenient methods. 

Pretreatment of the collected particulate matter may be required for chemical analysis. Pretreatment generally involves extraction of the particulate matter into a liquid. The solution may be further treated to transform the material into a form suitable for analysis. Trace metals may be determined by atomic absorption spectroscopy (AA), emission spectroscopy, polarogra-phy, and anodic stripping voltammetry. Analysis of anions is possible by colorimetric techniques and ion chromatography. Sulfate (S04 ), sulfite (SO-, ), nitrate (NO3 ), chloride Cl ), and fluoride (F ) may be determined by ion chromatography (15). 

In dry air and in the presence of polymerisation inhibitors methyl and ethyl 2-cyanoacrylates have a storage life of many months. Whilst they may be polymerised by free-radical methods, anionic polymerisation is of greater significance. A very weak base, such as water, can bring about rapid polymerisation and in practice a trace of moisture on a substrate is enough to allow polymerisation to occur within a few seconds of closing the joint and excluding the air. (As with many acrylic monomers air can inhibit or severely retard polymerisation). 

This is opposite from the order in solution as revealed by the pK data in water and DMSO shown in Table 4.14. These changes in relative acidity can again be traced to solvation effects. In the gas phase, any substituent effect can be analyzed directly in terms of its stabilizing or destabilizing effect on the anion. Replacement of hydrogen by alkyl substituents normally increases electron density at the site of substitution, but this effect cannot be the dominant one, because it would lead to an ordering of gas-phase acidity opposite to that observed. The dominant effect is believed to be polarizability. The methyl... 

NMR and visible spectra have established that a number of S-N anions are present in such solutions.The primary reduction products are polysulfides Sx, which dissociate to polysulfur radical anions, especially the deep blue 83 ion (/Imax 620nm). In a IM solution the major S-N anion detected by NMR spectroscopy is cycZo-[S7N] with smaller amounts of the [SSNSS] ion and a trace of [SSNS]. The formation of the acyclic anion 5.23 from the decomposition of cyclo-Sjl is well established from chemical investigations (Section 5.4.3). The acyclic anions 5.22 and 5.23 have been detected by their characteristic visible and Raman spectra. It has also been suggested that a Raman band at 858 cm and a visible absorption band at 390 nm may be attributed to the [SaN] anion formed by cleavage of a S-S bond in [SSNS]. ° However, this anion cannot be obtained as a stable species when [SsN] is treated with one equivalent of PPhs. 

Even polyalkoxy-s-triazines are quite prone to nucleophilic substitution. For example, 2,4,6-trimethoxy-s-triazine (320) is rapidly hydrolyzed (20°, dilute aqueous alkali) to the anion of 4,6-dimethoxy-s-triazin-2(l )-one (331). This reaction is undoubtedly an /S jvr-4r2 reaction and not an aliphatic dealkylation. The latter type occurs with anilines at much higher temperatures (150-200°) and with chloride ion in the reaction of non-basified alcohols with cyanuric chloride at reflux temperatures. The reported dealkylation with methoxide has been shown to be hydrolysis by traces of water present. Several analogous dealkylations by alkoxide ion, reported without evidence for the formation of the dialkyl ether, are all associated with the high reactivity of the alkoxy compounds which ai e, in fact, hydrolyzed by usually tolerable traces of water. Brown ... 

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