Nitrogen-containing compounds analysis

Where the target analyte contains heteroatoms such as nitrogen, phosphorus and sulfur, atom-selective detectors can provide an ideal detection method. A number of examples appear in the literature of the use of a detector called a thermal energy analyser (TEA) for the measurement of A-nitroso compounds [14-17] and aromatic nitro compounds [18]. This has also been used as an HPLC detector [19, 20], and a modified TEA has been reported to be useful for analysis of amines and other nitrogen-containing compounds [17]. Unfortunately, this technique appears not to have gained in popularity, since no reports have appeared in the literature for over two decades. 

Bound nitrogen includes all nitrogen-containing compounds, except N2, dissolved in water. Kjeldahl nitrogen analysis, described in Section 7-2, is excellent for amines and amides but fails to respond to many other forms of nitrogen. An automated combustion analyzer converts almost all forms of nitrogen in aqueous samples into NO, which is measured by chemiluminescence after reaction with ozone 17... 

Nitrogen-containing compounds with basic groups can successfully be trapped on silica. This implies for nitrogen mustards as well as for their precursors. As an example, triethanolamine (CAS CAS 102-71-6) was detected in air at low levels by trapping on activated silicagel (ORBO 53 tubes), desorbed and trimethylsilylated prior to GC/MS analysis. Using the SIM mode at mlz 262 ([M - CH2-0-TMS]+, a detection limit of l-2pg was reached for the method (38). 

Other detectors in use include the thermal conductivity detector (TCD) and the phosphorus-nitrogen detector (PND) which is much used in toxicology because of its selectivity for nitrogen-containing compounds. It is a feature of gas-liquid chromatography that spectrophotometric detectors can be coupled readily to the outflow for detection this includes IR, NMR and, particularly, mass spectrometers, in combined GC-MS analysers. Spectroscopic analysis allows structural information to be... 

A substrate (5-10 mmol.) was added to the autoclave containing I-H4 (3.5 g) at-78°C under a nitrogen stream. Then, the apparatus was heated to 120-180°C under nitrogen pressure (0.5 MPa) for 3 h with shaking. After the end of the reaction, products were extracted with benzene and analyzed with GC and GC-MS. In the case where nitrogen-containing compounds were used as a substrate, the products were isolated and purified by silica gel chromatography (with benzene-ethyl acetate as the eluant) and were identified with NMR and MS analysis. 

The volatile compounds of these samples were analyzed using SPME-GC-MS. 15 of the compounds included in Table 1 were identified in most samples of at least a group and underwent statistical analysis butane-2,3-dione, acetic acid, 3-methylbutanal, pentanal, hexanal, butanoic acid, hex-( )-2-enal, 3-methylbutanoic acid, heptan-2-one, hept-( -2-enal, octanal, oct-( )-2-enal, 1-octen-3-ol, and non-( )-2-enal. The effect of sodium chloride content, sodium nitrite, added amino acids and reaction time on these compounds is shown below. None of the esters, sulfur and nitrogen containing compounds included in Table 1 could be statistically analyzed. 

No significant differences were found for any compound when proline was added (Figure 3). Proline is an important precursor of the nitrogen containing compounds included in Table 1 but it was not possible to identify them by using SPME-GC-MS. However, proline addition caused an increase in the cured note when a sensory analysis was performed (30),... 

Items which have never been included in a kinetic analysis of the HDN network of quinoline are the formation and disappearance rates of PCHA, a key C-N bond cleavage intermediate, and the inhibition effect on the conversion of OPA, another important HDN intermediate. Furthermore, the absolute adsorption constants of these nitrogen-containing compounds on the catalytic sites for the different reaction steps, which are very important for the understanding of the chemistry of HDN and for extrapolating the laboratory data to the practical hydrotreating process, are not available. 

FIGURE 8.16 Representative nitrogen-containing compounds found in petroleum. Source K. H. Altgelt and M. M. Boduszynski, Composition and Analysis of Heavy Petroleum Fractions (New York Marcel Dekker, 1993), chap. 10. With permission. 

Kjeldahl analysis of nitrogen-containing compounds, proteins, p. 287... 

Since its introduction in 1964 the thermionic alkali bead detector has been successfully used for the specific detection of phosphorus compounds, particularly pesticides, and has been developed for the analysis of nitrogen-containing compounds such as drugs [62,69-72]. The NPD was originally... 

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