Potassium ionization

Without authentic standards or a spectroscopic detection scheme, compound identification is difficult. Our choice of a desorption/ionization method is potassium ionization of desorbed species (K+IDS) with mass spectrometric detection (n. 12) which provides a rapid qualitative tool for compound identification. Using K+IDS, molecular weight data is available and fragmentation is minimal. Ions appear as M[K], the mass of the analyte plus 39 Da, the mass of potassium. Hence, structure identification is possible based on a knowledge of starting materials and the molecular weight data afforded by K+IDS. 

SiOEt-terminated carbosilane dendrimers were prepared and characterized using potassium ionization of desorbed species mass spectrometry74. Preliminary investigations into the sol-gel chemistry of these dendrimers were also carried out. 

Only chemical interferences were observed sodium and potassium ionized in the air-acetylene flame, and aluminum ionized in the nitrous oxide-acetylene flame magnesium and calcium exhibited evidence of interference by both phosphorus and aluminum. All the other elements were found to be interference-free. The addition of 1000 ppm of cesium as an ionization suppressor effectively removed the ionization interference in the sodium and potassium solutions. Similarly, 1000 ppm of lanthanum removed the interference due to phosphorus and aluminum in the magnesium and calcium solutions and suppressed the ionization of aluminum. 

Adding an excess of a more easily ionized element to all standards and samples eliminates ionization interference. This addition creates a large number of free electrons in the flame. The free electrons are captured by the analyte ions, converting them back to atoms. The result is to suppress the ionization of the analyte. Elements often added as ionization suppressants are potassium, rubidium, and cesium. For example, in the AAS determination of sodium, it is common to add a large excess of potassium to all samples and standards. Potassium is more easily ionized than sodium. The potassium ionizes preferentially and the free electrons from the ionization of potassium suppress the ionization of sodium. The detection limit of the sodium determination thereby decreases. The ionization suppression agent, also called an ionization buffer, must be added to all samples, standards, and blanks at the same concentration for accurate results. An example of the use of ionization suppression is shown in Fig. 6.20. Absorbance at a barium resonance line (atomic absorption) and absorbance at a barium ion line (by barium ions in the flame) are plotted as a function of potassium added to the solution. As the potassium concentration increases, barium ionization is suppressed the barium stays as barium atoms. This results in increased atomic absorption at the resonance line and a corresponding decrease in absorbance at the ion line. The trends in absorbance at the atom and ion lines very clearly show that barium ion formation is suppressed by the addition of 1000 ppm of the more easily ionized potassium. 

Static secondary ion mass spectrometry (SSIMS) 1976 Atmospheric pressure chemical ionization (APCI) 1976 Thermospray (TSP) 1978 Electrohydrodynamic ionization (EH) 1978 Fast atom bombardment (FAB) 1982 Potassium ionization of desorbed species (KIDS) 1984 Electrospray ionization (ESI) 1984 Multiphoton ionization (MPI) 1987... 

Potassium Ionization Suppressant Solution containing an oil-soluble potassium compound in kerosine at 2.0 0.1 g potassium/litre of solution. 

We have investigated several samples of oriental lacquer by a combination of capillary gas chromatography, supercritical fluid chromatography, high resolution NMR spectroscopy and two techniques of mass spectrometry, especially potassium ionization of desorbed species (K" IDS) mass spectrometry for the isolation and characterization of the components of urushiol. The composition of the urushi fraction of these samples was found to consist in general of the components that had been found by former analyses of urushi samples. Our new understanding allows us to recognize quickly and more accurately individual components of oriental lacquers. 

The ketone is added to a large excess of a strong base at low temperature, usually LDA in THF at -78 °C. The more acidic and less sterically hindered proton is removed in a kineti-cally controlled reaction. The equilibrium with a thermodynamically more stable enolate (generally the one which is more stabilized by substituents) is only reached very slowly (H.O. House, 1977), and the kinetic enolates may be trapped and isolated as silyl enol ethers (J.K. Rasmussen, 1977 H.O. House, 1969). If, on the other hand, a weak acid is added to the solution, e.g. an excess of the non-ionized ketone or a non-nucleophilic alcohol such as cert-butanol, then the tautomeric enolate is preferentially formed (stabilized mostly by hyperconjugation effects). The rate of approach to equilibrium is particularly slow with lithium as the counterion and much faster with potassium or sodium. 

Potassium is more easily ionized than sodium. The high concentration of potassium in the sample suppresses the ionization of sodium, increasing its emission relative to that of a standard of equal concentration that does not contain potassium. 

Fig. 2. MHD-steam power plant where HRSR is heat recovery seed recovery and the seed is an easily ionizable potassium salt. See text.

Potassium, a soft, low density, silver-colored metal, has high thermal and electrical conductivities, and very low ionization energy. One useful physical property of potassium is that it forms Hquid alloys with other alkah metals such as Na, Rb, and Cs. These alloys have very low vapor pressures and melting points. 

Anionic Polymerization of Cyclic Siloxanes. The anionic polymerization of cyclosiloxanes can be performed in the presence of a wide variety of strong bases such as hydroxides, alcoholates, or silanolates of alkaH metals (59,68). Commercially, the most important catalyst is potassium silanolate. The activity of the alkaH metal hydroxides increases in the foUowing sequence LiOH < NaOH < KOH < CsOH, which is also the order in which the degree of ionization of thein hydroxides increases (90). Another important class of catalysts is tetraalkyl ammonium, phosphonium hydroxides, and silanolates (91—93). These catalysts undergo thermal degradation when the polymer is heated above the temperature requited (typically >150°C) to decompose the catalyst, giving volatile products and the neutral, thermally stable polymer. 

Analytical Techniques. Sorbic acid and potassium sorbate are assayed titrimetricaHy (51). The quantitative analysis of sorbic acid in food or beverages, which may require solvent extraction or steam distillation (52,53), employs various techniques. The two classical methods are both spectrophotometric (54—56). In the ultraviolet method, the prepared sample is acidified and the sorbic acid is measured at 250 260 nm. In the colorimetric method, the sorbic acid in the prepared sample is oxidized and then reacts with thiobarbituric acid the complex is measured at - 530 nm. Chromatographic techniques are also used for the analysis of sorbic acid. High pressure Hquid chromatography with ultraviolet detection is used to separate and quantify sorbic acid from other ultraviolet-absorbing species (57—59). Sorbic acid in food extracts is deterrnined by gas chromatography with flame ionization detection (60—62). 

The performance of many metal-ion catalysts can be enhanced by doping with cesium compounds. This is a result both of the low ionization potential of cesium and its abiUty to stabilize high oxidation states of transition-metal oxo anions (50). Catalyst doping is one of the principal commercial uses of cesium. Cesium is a more powerflil oxidant than potassium, which it can replace. The amount of replacement is often a matter of economic benefit. Cesium-doped catalysts are used for the production of styrene monomer from ethyl benzene at metal oxide contacts or from toluene and methanol as Cs-exchanged zeofltes ethylene oxide ammonoxidation, acrolein (methacrolein) acryflc acid (methacrylic acid) methyl methacrylate monomer methanol phthahc anhydride anthraquinone various olefins chlorinations in low pressure ammonia synthesis and in the conversion of SO2 to SO in sulfuric acid production. 

What trend is observed in the first ionization energy as you move from lithium down the column I metals On this basis, can you suggest a reason why potassium or cesium might be used in preference to sodium or lithium in photoelectric cells ... 

Potassium, 93 atomic radius, 399 atomic volume, 410 chemistry, 95 electron configuration, 271 heat of vaporization, 305 ionization energy, 268 properties, 94... 

Both the a- and a -hydrogens of dibenzyl sulfone were shown to be ionized by means of two equivalents of potassium amide in liquid ammonia322. 

Account for the fact that the ionization energy of potassium is less than that of sodium despite the latter having the smaller effective nuclear charge. 

Buffers are used in HPLC to control the degree of ionization of the analyte and thus the tailing of responses and the reproducibility of retention. A range of buffers is available but those most widely used are inorganic, and thus involatile, materials, such as potassium or sodium phosphate. 

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