Ammonia derivatizing

FIGURE 9.16 Ammonia derivatization process involving benzene sulfonylation with benzenesulfonyl chloride and subsequent reaction with dimethylformamide dimethyl acetal to form benzesulfonyldimethyl-aminomethylene derivative. 

Reactions can also occur during chromatographic development. These can either be undesired reactions or planned derivatizations. Thus, Weicker and Brossmer [11] have reported, for example, that hexoses, pentoses and disaccharides can be ammated when ammonia-containing mobile phases are employed on silica gel G layers. On the other hand, fluorescamine or ninhydrin have been added to the... 

Summary If the molecular weight is odd, then the compound contains an odd number of nitrogens. Fragment ions observed at even-mass numbers suggests the presence of nitrogen. The loss of ammonia is fairly common in nitrogen compounds and may not indicate exclusively that an amine is present. Chemical derivatization will easily determine if the unknown is a tertiary amine. 

In Olin s attempts to derivatize dilithiated products of o-carborane with chlorosilanes for further reaction with ammonia, it was observed that cyclic compounds, instead of polymers, were produced by the interaction of the substituents on the adjacent carbon atoms in the o-carborane units.11 However, when a linear dimethoxy intermediate of m-carborane was reacted as an equimolar mixture with dichlorosilane in the presence of the catalyst FeCl3, the quantitative evolution of CH3C1 was observed... 

Although Certify is a mixed mode sorbent with C8 and sulfonic acid moieties, the authors rationalized that the hydrophobic retention on this sorbent is more dominant and caused the nonretention of certain drugs during methanol wash. The weak WCX ion exchanger was also excluded for similar reasons. Both the mixed mode strata-X-C and the ion exchange sorbent SCX were found to be most amenable for the derivatization-based GC/MS analysis and both yielded pure extracts. However, the yields were consistently lower with strata-XC than SCX and the authors hypothesized that this was due to the inability of the 5% ammonia/methanol eluent to completely disrupt the hydrophobic and dipolar interactions between the analytes and XC. 

If polyribonucleotides are treated simultaneously with methoxylamine and bisulphite, cytidine residues are converted into 5,6-dihydro-7V4-methoxycytidine-6-sulphonate,154 and uridine into 5,6-dihydrouridine-6-sulphonate.155 Treatment with dilute ammonia regenerates the uridine residues, leaving the dihydrocytidine derivatives unaffected. When only the cytidine residues have been derivatized, pancreatic ribonuclease becomes uridyl ribonuclease, since it is unable to cleave the chain on the 3 -side of the modified cytidine.154 This allows the isolation of blocks of modified cytidine residues. T2 ribonuclease may also be used. Alternatively, a ribonuclease from Physarum polycephalum has been found to hydrolyse CpX links very slowly, allowing the isolation of cytidine blocks.156 If both uridine and cytidine residues are modified, T2 ribonuclease acts as puryl ribonuclease, allowing the isolation of cumulative blocks of pyrimidines.155 This ability to alter the specificity of nuclease cleavage is a useful tool in sequence analysis. 

The presence of hexamethylenediamine (4c) in hydrolyzed human urine is indicative of exposure to hexamethylene diisocyanate. The diamine was determined after derivatization with heptafluorobutyric anhydride followed by GC-CI-MS, using ammonia as the ionizing reagent and deuterated hexamethylenediamine as internal standard LOD 0.5 j.ig/L urine97. 

Polypropylene (PP) is a hydrophobic and chemically inert polymer which needs to be activated in order to be functional as a support for NA immobilization. Typically, PP membranes are aminated by exposure to an ammonia plasma generated by radiofrequency plasma discharge. Once aminated, the PP membranes can be reacted with derivatized ONDs using common coupling methods [56-58]. 

Elemental composition C 52.96%, 0 47.04%. It may be analyzed by treatment with water. The product malonic acid formed may be measured quantitatively by direct injection of aqueous solution into a GC for FID detection. Alternatively, the aqueous solution may be evaporated and the residue may be derivatized to methyl ester and identified by mass spectrometry. Also, the gas may react with ammonia or an amine, and the amide derivative may be identified and quantitatively determined by GC-FID, GC-NPD, GC/MS or infrared techniques. 

A new gas chromatography (GC) method was developed to characterize artemether 28a and its metabolites in body fluids. The extracts were derivatized and then separated on an optimized capillary GC system and identified by chemical ionization MS using ammonia as the reagent gas <1998JCH(B)101>. A sensitive, selective, and reproducible GC-MS-SIM method has also been developed for the determination of artemether 28a and dihydroartemisinin 29a in plasma, using artemisinin 9a as an internal standard <1999JCH(B)251>. 

Supercritical fluid chromatography (sfc) combines the advantages of gc and hplc in that it allows the use of gc-type detectors when supercritical fluids are used instead of the solvents normally used in hplc. Carbon dioxide, n-petane, and ammonia are common supercritical fluids, For example, carbon dioxide employed at 7.38 MPa (72 9 atm) and 31.3°C has a density of 448 g/mL. Derivatization of primary and secondary amines using 9-fluorenylmethy] chlorofomiate to form a nonpolar, uv-absorbing derivative lias been reported. 

Fig. 11 Separation of amino acid standards derivatized with PITC. Eluent A sodium acetate/triethy-larnine buffer (pH 6.4) eluent B 60/40 acetonitrile/water. Pico-Tag column. Peak identification 1 Asp, 2 Glu, 3 Ser, 4 Gly, 5 His, 6 Arg, 7 Thr, 8 Ala, 9 Pro, 10 ammonia, 11 Tyr, 12 Val, 13 Met, 14 Cys, 15 lie, 16 Leu, 17 Phe, 18 Lys. (From Ref. 184. Copyright 1984 Elsevier Science.)...

Ammonia derivative formation The derivatization is carried out using a 10% ammonia solution mixed with the column effluent (64). The main advantages are an increase in sensitivity (1.7 times the signal of the underivatized ochratoxin A), and the availability of a confirmation test for ochratoxin A, as a consequence of this change of sensitivity. A second HPLC pump, similar to that described in Fig. 2 for aflatoxins, and a reaction coil of 10 cm are necessary. Conditions are as follows 0.5 ml/min as flow rate, room temperature, excitation wavelength of 370 nm, and emission wavelength... 

Solutions ofLiOCH and NaCsCH in liquid NH3 are mostly prepared by the so-called titration method, which involves controlled addition of pieces of metal to boiling ammonia while introducing acetylene. The blue colour of the dissolved metal serves as an indicator. This method is also applicable in the case of homologues, but is less attractive for economical reasons (one third of the acetylene is reduced to ethene). Derivatization of solutions of HteCM obtained from MNH2 or M and acetylene, in most cases gives only minor amounts of disubstituted acetylenes RC=CR, so it is inferred that di-metallated acetylene C C- occurs at best in only very small concentrations in liquid ammonia. 

Nitrogenase reduces N2 and several nitrogen-containing substrates to ammonia and amines. This assay uses a dabsyl precolumn derivatization method in quantitating the products. 

The reaction was stopped by addition of 0.1 mL of 1 N HC1 in saturated KI03. Following centrifugation, derivatization was performed on a 0.4 mL aliquot by adding 0.4 mL of 0.164 M borate buffer (pH 10.0) followed by 0.4 mL of 1.67 mM dansyl chloride (dissolved in acetone). After 90 minutes of incubation at room temperature, a 20 /xL sample was injected directly into the HPLC. To minimize background ammonia and methyl amine, it was important to prepare all reagents in HPLC-grade water. 

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