Nitrogen-specific detector

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... 

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

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. 

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). 

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. 

Atrazine, simazine demetryn, prometryn Nitrogen specific detector 10 8M [423]... 

The major advantage of using the urinary S R ratio as a phenotypic trait for assessing CYP2C19 activity is that the method is fairly robust with regard to any incompleteness of urine collection or noncompliance with respect to dose administration. This is because the R-enantiomer serves as an in vivo internal standard. On the other hand, the required enantiospecific assay uses chiral capillary column gas chromatography with a nitrogen-specific detector, and such instmmentation is not commonly available. For this reason, an alternative phenotypic trait measure based on the formation and urinary elimination of 4 -hydroxymephenytoin has also been frequently used. 

The method is not only applicable to the EU-official aqueous and fatty food simulant but also to foodstuffs such as beverages and soft margarine. Indeed the collaborative trial included fruit juice, wine and sunflower oil. The level of migrated acrylonitrile is determined by headspace gas chromatography, preferably with automated sample injection and using a nitrogen specific detector, for instance an alkali flame ionization detector (AFID). This gives the method the necessary sensivity to meet the... 

FID = flame ionization detector GC = gas chromatography HPLC = high performance liquid chromatography NMR = nuclear magnetic resonance NS = not stated NSD = nitrogen specific detector TMS = tetramethylsi 1ane UV = ultraviolet. 

Hewlett Packard 5880 gas chromatograph with nitrogen specific detector (NPD), (Hewlett-Packard, Palo Alto, CA, USA). 

The acetone extract of the polymer is analyzed by gas chromatography, using N-(3-methoxypropyl)pyrrolidone as an internal standard. A nitrogen-specific detector (NSD) is used. 

Coating of the glass surface as well as the diatomaceous earth (Procedure A) produced results for morphine that showed less adsorption relative to a hydrocarbon than when diatomaceous earth only was treated. With the nitrogen-specific detector there was, however, only a slight difference between the methods A and B over a range of about 25-100 ng of morphine. 

Whereas detection limits for heroin with conventional FID are reported as 0.05 mg/ml in blood from illicit preparations, a nitrogen specific detector can quantitate levels of 100 ng/ml - and detection limits can be as low as 20 ng/ml according to Smith and Cole3 3. They determined heroin and its metabolite 6-0-acetylmorphine in blood after extraction and deriva-tization to its trifluoroacetate, to prevent adsorption during the gas chromatographic analysis when the free hydroxyl group was present. Ethylmorphine, derivatized in the same way was used as an internal standard. 

Separation of hydrazine and dimethylhydrazines from environmental samples is by acid extraction when necessary. Air samples are usually collected in a bubbler with acid or on an acid-coated silica gel (NIOSH 1977a, 1977b, 1984). When GC is employed, detection may be by electron capture detector (ECD), FID, nitrogen-specific detector (NSD), thermionic ionization detector (TID), and/or MS as described above (Section 6.1). 

Figure 1. GC of Shale-I basic nitrogen compounds using a 100-m OV-101 WCOT glass capillary column and a nitrogen-specific detector. Organic bases were extracted from the jet fuel with 1N aqueous HCl. Known compounds elute at indicated times.

Cyanide in aqueous matrices is usually measured by colorimetric, titrimetric, electrochemical methods or by headspace gas chromatography with a nitrogen-specific detector, after pretreatment to produce hydrogen... 

Since GC instrumentation is available in most analytical laboratories, it has been the principal method of analysis for volatile A -nitrosamines. Many detectors have been coupled to GC for the detection of A -nitrosamines. The conventional flame ionization detector (FID) was initially used but was found to be limited for Ai-nitrosamines. Nitrogen-specific detectors such as the Alkali Hame Ionization (AFID), the Coulson Electrolytic Conductivity (CECD) and Hall Electrolytic Conductivity (HECD) are useful for routine screening. Although the HECD is the most selective, it is not specific to A-nitrosamines and an independent confirmation is necessary for each analysis. The efficiency of common GC detectors for the analysis of A-nitrosamines has been compared by several authors. 

Method 2501. Air is passed over a solid sorbent tube containing 2-(hydroxy-methyl)piperidine on XAD-2. It is converted to 9-vinyl-l-aza-8-oxabicyclo[4.3.0]nonane, desorbed with toluene and analyzed by GC with a nitrogen specific detector. 5% SP-2401-DB on Supelcoport (100-120 mesh) is a suitable column. 

Aliphatic amines may be analyzed by GC using a flame ionization detector. Aqueous samples may be injected directly into the GC. A nitrogen-specific detector is more sensitive and can be used for nonaqueous solutions. 

Analysis of dimethyl- and diethylamine in air may be performed in accordance to NIOSH Method 2010 (NIOSH 1984, Suppl. 1989). About 3-30 L of air at a fiow rate of 10-1000 mL/min is passed through a silica gel (20/40 mesh, 150 mg front and 75 mg back) sorbent tube. The analytes are desorbed with dilute sulfuric acid in 10% aqueous methanol (3-h ultasonication) and injected into a GC equipped with a FID. A packed column, 4% Carbowax M over 0.8% KOH on Carbosieve B (60/80 mesh) was used in the NIOSH laboratory. A nitrogen-specific detector may be used for amine analysis instead of an FID, using a DB-5 fused-silica capillary column. This method may be applied for the analyses of other aliphatic amines in air and also for certain ethanolamines (NIOSH 1984, Suppl. 1989, Method 2007). Alternatively, ethanolamines may be analyzed by NIOSH Method 3509 (NIOSH 1984, Suppl. 1989). These compounds present in air (5-300 L of air) are... 

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