Reagent gases amine

Several gases are used in Cl ionization methane, propane, isobutane, hydrogen, ammonia, water, tetramethyl silane, or dimethyl amine. The Cl ion source is similar to the El source but is designed to have an ionization chamber. In positive chemical ionization, the ion source is filled with a reagent gas which is ionized to create a species of the proton donator type that can form a... 

The composition of the reagent gas plasma is controlled by the mobile phase composition. It contains reactant ions of the type HsO, CH30H2, CHsCNH, etc., in most cases solvated by solvent molecules, for example, CH30H2 (H20)n(CH30H)ni with n + m < 4. The presence of ammonia vapor, for example, as a result of the evaporation of ammonium acetate added to the mobile phase, causes rapid removal of protonated solvent ions with formation of ammonium ions that become the dominant reagent gas ions. The addition of alkylamines or acids to the mobile phase results in the formation of protonated amines or anions as the dominant species in the reagent gas plasma. Since highly reactive ions, such as CHs" ", can not be formed by APCI in the presence of solvents, it is not possible to ionize saturated hydrocarbons or other compounds of low gas-phase basicity. 

How would you expect the El and Cl mass spectra of stearyl amine (MW = 269) to differ If the Cl mass spectmm is collected using methane as a reagent gas, would you expect to see any peaks in the spectrum at m/z > 269 Explain. 

FIGURE 18.4 Mobility spectra showing the formation of volatile amines from the spoilage of pork, turkey, beef, and chicken during storage at room temperature for 1 day. Calibration was with 2 ng of TMA (trimethylamine). TMA and cadaverine (CAD) are apparent in the mobility spectrum for each muscle food. The reagent gas was n-nonylamine. (From Karpas et al.. Determination of volatile biogenic amines in muscle food products by ion mobility spectrometry, AmZ. Chim. Acta 2002, 463(2) 155-163. With permission.)... 

Aluminum chloride [7446-70-0] is a useful catalyst in the reaction of aromatic amines with ethyleneknine (76). SoHd catalysts promote the reaction of ethyleneknine with ammonia in the gas phase to give ethylenediamine (77). Not only ammonia and amines, but also hydrazine [302-01-2] (78), hydrazoic acid [7782-79-8] (79—82), alkyl azidoformates (83), and acid amides, eg, sulfonamides (84) or 2,4-dioxopyrimidines (85), have been used as ring-opening reagents for ethyleneknine with nitrogen being the nucleophilic center (1). The 2-oxopiperazine skeleton has been synthesized from a-amino acid esters and ethyleneknine (86—89). 

Trimethylsilyl cyanide. This reagent readily silylates alcohols, phenols, and carboxylic acids, and more slowly, thiols and amines. Amides and related compounds do not react with this reagent. The reagent has the advantage that a volatile gas (HCN is highly toxic) is the only byproduct. 

Diglycolamine Systems. The Fluor Econamine process uses digl> co lamine (DGA) to sweeten natural gas. The active DGA reagent is 2-(2-tunino-ethoxy) ethanol, w hich is a primary amine. The reactions of DG, with acid gases are the same as for MEA. Degradation products from reactions with COS and CS2 can be regenerated in a reclaimer. 

Acylation of various oxygen functions by use of common and commercially available fluonnated carboxylic acid denvatives such as trifluoroacetic anhydride or the corresponding acyl halides have already been discussed sufficiently in the first edition [10] Therefore only exceptional observations will be described in this section In the past 15 years, many denvatizations of various nonfluonnated oxygen compounds by fluoroacylation were made for analytical purposes. Thus Mosher s acid chlorides for example became ready-to-use reagents for the determination of the enantiomeric purity of alcohols and amines by NMR or gas-liquid chromatographic (GLC) techniques [//] (equation 1)... 

Ion pair extraction has also been used to extract polar analytes in bioanalytical procedures. Figure 15.2 exemplifies the determination of the amino acid taurine by gas chromatography-mass spectrometry (GC-MS) this figure also illustrates a useful property of amines (and phenols), which is that they will react more rapidly than water with an acylating reagent in an aqueous environment thus improving their organosolubility. After acylation and ion pair extraction with tetrabutyl ammonium sulphate the taurine is converted to an amide prior to analysis by GC-MS. 

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