Nitrogen-specific

A iridine traces in aqueous solution can be determined by reaction with 4-(p-nitroben25l)pyridine [1083-48-3] and potassium carbonate [584-08-7]. Quantitative determination is carried out by photometric measurement of the absorption of the blue dye formed (367,368). Alkylating reagents interfere in the determination. A iridine traces in the air can be detected discontinuously by absorption in Folin s reagent (l,2-naphthoquinone-4-sulfonate) [2066-93-5] (369,370) with subsequent chloroform extraction and hplc analysis of the red dye formed (371,372). The detection limit is ca 0.1 ppm. Nitrogen-specific thermal ionisation detectors can be used for continuous monitoring of the ambient air. 

The effort required to establish identity of a nitrosamine in an environmental sample depends on the nature of the problem and the specificity of the primary detection system. TEA response is much stronger evidence of identity than response from a flame ionization or nitrogen-specific detector. If TEA response is supported by chemical (9) or ultraviolet photolysis (8) supporting data, identification is adequate for many... 

The sample is homogenized with acetonitrile. An aliquot of the extract is evaporated to dryness and the residual material is dissolved in ethyl acetate-toluene (3 1, v/v), and subjected to cleanup by gel permeation chromatography (GPC). After GPC, the sample is subjected to an alumina and Florisil SPE cleanup procedure. The concentrated eluate is analysed by gas chromatography/thermionic nitrogen-specific detection (GC/TSD). 

Gas chromatograph fitted with a thermionic nitrogen-specific detector Gas chromatograph fitted with a quadrupole mass-selective detector... 

CLND Total nitrogen specific Easy quantitation (single standard) High linearity (105) [43,44]... 

This section summarizes the literature on biodenitrogenation, with focus on BDN studies using quinoline, carbazole, pyridine and indole as model organonitrogen molecules. Research related to biodegradation (vs. nitrogen-specific conversion) of organonitrogen molecules is also considered, since it can be a viable option for relatively low-nitrogen feedstocks. 

Materials. Na-Kaolinite A homoionic sample of kaolinite was prepared from a well-crystallized sample purchased from Source Clays, University of Missouri, using a standardized technique (14) which involved repeated washing with distilled water and by treatment with NaCl solutions to remove exchangeable ions such as Ca, and freeze-drying of the final product. Nitrogen specific surface area of this kaolinite was estimated to be 9.4nr/g and X-ray analysis showed the characteristic pattern of kaolinite. 

Leppert et al. [86] have described a procedure for the determination of Carbosulphan and Carbofuran (2,3-dihydro 2,2-dimethylbenzofuran-7-yl-methyl carbamate) utilizing gas chromatography with a nitrogen specific detector. Extraction was carried out using hexane-2-propanol or a methanol buffer. 

Bilikova and Kuthan [87] developed a gas chromatographic method for the determination of submicrogram concentrations of Carbofuran (2,3-dihydro-2, 2,-dimethylbenzofuran-7-yl-methyl carbamate) in soils. Soil samples are mixed with methanol-water (80 20) and water samples are extracted with chloroform. After separation of the chloroform, and weak alkaline hydrolysis, derivatization is performed with l-fluoro-2,4-dinitrobenzene. The ester produced is isolated from benzene and cleaned up with acetone. The acetone extract is used to determine Carbofuran by gas chromatography with a nitrogen-specific detector. 

Cotterill [100] studied the effect of ammonium nitrate fertilizer on the electron capture or nitrogen specific gas chromatographic determination of Triazine plus other types of herbicide (Atrazine(2-chloro-4-ethylamino-6-isopropylamino, 1,3,5 triazine), Simazine (2-chloro-4.6 bis ethyl amino 1,3,5 triazine), Linuron (3,4,-chlorophenyl-l-methoxy-l-methyl urea), Metribuzin, Triallate and Phorate) residues in soil. 

Low detection limits (low ng/mL) have been achieved using a headspace/gas chromatographic (GC) technique (Seto et al. 1993). The sample is acidified and incubated, and the headspace analyzed by GC with a nitrogen-specific detector (NPD) (Carseal et al. 1993 Levin et al. 1990 Seto et al. 1993). Reported recovery is good (>90%) (Carseal et al. 1993), and precision is good as well (<15% RSD) (Carseal et al. 1993 Levin et al. 1990 Seto et al. 1993). Blood samples may be treated with chloramine T priorto incubation to produce a derivative which can be determined by GC with electron capture detection (ECD). Cyanate and thiocyanate do not interfere in this method (Odoul et al. 1994). The detection limit is 5 pg/L (ppb) precision is good (<15% RSD) (Odoul et al. 1994). 

Nitrophenols in fog and atmospheric particles were determined by GC of the underiva-tized compounds and their corresponding acetate esters. Four fused-silica columns were used with three alternative detection modes, namely mass-selective detection, nitrogen-specific detection and ECD. GC-ECD of the acetate derivatives gave the best results501. A capillary GC-UVD method was developed for the determination of small amounts of nitrophenols present in the environment. The method was compared with HPLC-UVD from the point of view of selectivity and sensitivity. LOD for GC were about one-tenth of those for HPLC502. 

In both systems the flow of helium carrier gas through the columns was 0.7-0.8 ml min-1, with a septum purge of 0.5 ml min-1 and a split valve flow of 4-4.5 ml min-1. The injection ports were maintained at 260°C and the detector ovens at 240° C. The detector employed was either a flame ionisation or a nitrogen-specific NPD-40 thermionic detector (Erba Science (UK) Ltd) and the output was recorded on a HP 3390 integrator (Hewlett Packard Ltd, Wokingham, UK). 

Fujinari EM, Courthaudon LO. Nitrogen-specific liquid-chromatography detector based on chemiluminescence—Application to the analysis of ammonium nitrogen in waste-water. Journal of Chromatography 592, 209-214, 1992. 

Nitromethane can be determined in workplace air by adsorbing the air sample on Chromosorb, desorbing with ethyl acetate and analysing by gas chromatography with nitrogen-specific detection (method 2527) (Eller, 1994). 

Lawrence JF, Iverson F. 1975. Analysis of the diazinon metabolites G 27550 and GS 31144 by gas liquid chromatography with nitrogen-specific detection after derivatization. J Chromatogr 103 341-347. 

However, by no means are microbore HPLC columns nonoptimal when sample volumes are limited. Because of the substantially reduced mobile-phase volumes necessary to carry out a given separation, microbore columns are more easily interfaced to many useful detection systems, for example, electron-capture detectors, nitrogen-specific thermionic detectors, and mass spectrometers. 

It is, perhaps, relevant to say a few words about the problem of other reactive species in active nitrogen, specifically as it pertains to the NO titration technique of nitrogen atoms and NO chemistry. 

EM Fujinari, JD Manes. Nitrogen-specific detection of peptides in liquid chromatography with chemiluminescent nitrogen detector. J Chromatogr A 676 113-120, 1994. 

RR Laski, RR Watts. Gas chromatography of organonitrogen pesticides, using a nitrogen-specific detection system. J Assoc Off Anal Chem 56 328-332, 1973. 

Thus, Caverley and Unwin [158] have described a rapid and sensitive technique for the determination of residues of the fungicides, furalaxyl and met-alaxyl in plants. Plants are macerated with acetone and after filtration and dilution with water, partitioned with chloroform. The extracts are subjected to GC with a nitrogen-specific detector after removal of chloroform and dissolution in acetone. Recoveries are generally better than 80%, with detection limits of 0.1 mg/kg for lettuce. 

Nussbaum MA, Baertschi SW, Jansen PJ. Determination of relative UV response factors for HPLC by use of a chemiluminescent nitrogen-specific detector. J Pharm Biomed Anal 2002 27 983-993. 

GC using a nitrogen-specific detector (NPD) (i.e., NPD in N-specific mode), and (2) reverse phase HPLC using an UV detector. 

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