Phosphates molecular ions

ToF-SIMS of SAM Surfaces. For the series of mixed self-assembled monolayer surfaces ( (oh-ddpo4 = 0, 0.25, 0.5, 0.75, 1), two negative ion spectra per sample were recorded for three independent series. The dodecyl phosphate molecular ion peak, with the loss of one hydrogen (M — H) in the negative secondary ion spectrum. 

Bhaumik, A., Inagaki, S. 2001. Mesoporous titanium phosphate molecular sieves with ion-exehange capacity J Am Chem Soe 123 691-696. 

Molecular orbital theory may provide an explanation for stereochemical differences between carboxylate-metal ion and phosphate-metal ion interactions. Detailed ab initio calculations demonstrate that the semipo-lar 1 0 double bond of RsP=0 is electronically different from the C=0 double bond, for example, as found in H2C=0 (Kutzelnigg, 1977 Wallmeier and Kutzelnigg, 1979). The P=0 double bond is best described as a partial triple bond, that is, as one full a bond and two mutually perpendicular half-7r bonds (formed by backbonding between the electrons of oxygen and the empty d orbitals of phosphorus). Given this situation, a lone electron pair should be oriented on oxygen nearly opposite the P=0 bond, and these molecular orbital considerations for P=0 may extend to the phosphinyl monoanion 0-P=0. If this extension is valid, then the electronic structure of 0-P=0 should not favor bidentate metal complexation by phosphate this is in accord with the results by Alexander et al. (1990). 

The fragmentation of isomeric 5- and 6-nitro-l-/Molucncsulfonyl-2-alkylbenzimida-zoles[695,710],S- 5(6)-nitrobenzimidazol-2-ylmethyl iV-morpholino-dithiocarbamate [1090], 4-, 5-, and 6-nitro-l-[)-A)-ribofuranosyl benzimidazole 3, 5 -phosphates [711], and the products of alkylation of 5(6)- and 4(7)-nitrobenzimidazole derivatives [702] has been studied. The molecular ion peaks of 2-alkylthio- and 2-ethylsulfono-5(6)-nitrobenzimidazole are reported [718],... 

First let s note the "inorganic" (sometimes called mineral) molecules and molecular ions oxygen (O2), water (H2O), carbon dioxide (CO2), ammonia or ammonium ion (NH3 or NH4 ), nitrate ion (NOs"), nitrogen (N2), phosphate ion (P04 -) and sulphate ion (SO42-). These are mostly metabolites, though the ions can also serve as counter ions along with chloride in creating the intracellular media. 

Flanigen s review describes the structures, chemistry, and potential applications of alumino-phosphate molecular sieves (ALPO4-S) [41]. There are many ALPO4 structures with a wide variety of pore sizes and shapes. The Al/P ratio in the ALPO4 framework is always 1. All ALPO4-S are therefore neutral, have no ion-exchai e capacity, and cannot be made acidic. This excludes acid catalytic applications except where the acid sites should be extremely weak. Olefin isomerization, certain aromatic alkylations, and MTO are potential applications [42]. 

A. Bhaumik and S. Inagaki, Mesoporous Titanium Phosphate Molecular Sieves with Ion-exchange Capacity. J. Am. Chem. Soc., 2001, 123, 691-696. 

By use of SIM, the selectivity and thereby the sensitivity of the MS for organophosphates can be enhanced. For alkylated phosphates, no or very weak molecular ions are observed, while a m/z 99 fragment corresponding to protonated phosphoric acid can be considered to be characteristic. Due to the extensive fragmentation of alkylated phosphates using GC-MS-EI, it is often necessary to apply the GC-MS-PICI technique for identification. Arylated phosphates, on the other hand, exhibit an intense molecular ion and do not show the fragment of m/z 99 in its MS-El spectra. 

In MALDI-MS, impurities at low to intermediate concentrations form adducts with analyte molecules that can obscure the relevant data and reduce the overall signal intensity. Figure 7b and c contain representative EWOD-MALDl-MS spectra for rinsed and nominsed samples of angiotensin n prepared with 20 mM sodium phosphate. In the spectrum of the nmuinsed sample (Fig. 7b), peaks at M + 23, M + 45, and A/ + 67 corresponded to the mmiosodium, disodium, and trisodium adducts of the parent molecule. These adduct peaks are barely visible in the spectrum of the rinsed sample. The intensities of the molecular-ion peaks in the rinsed spectra were about twice as great as those observed in the cmitrol spectra [12]. 

Figure 1.22c shows the LD/EI/FT/ICR mass spectrum of a second phosphite additive, WESTON 618 diphosphite. Although the molecular ion miz 732) is readily observed, its abundance is lower than for Ultranox 626 diphosphite or XF 2502, presumably because WESTON 618 diphosphite has saturated hydrocarbon chains in place of aromatic rings and therefore fragments more easily. Similar behaviour has been reported for other phosphate additives [43]. 

The molecular ion (M — H) intensity of the methyl-terminated phosphate is 1 order of magnitude greater than that of the hydroxy-terminated phosphate. It has been reported that the detection of molecular mass ions M - H is correlated with the degree of order in self-assembled monolayers, resulting from energy transfer and stability effects. We assume that the higher count rate... 

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