Nitrogen-phosphorous detector

NPD Nitrogen phosphorous detector or PDPI Photodissociation-photoionisation... 

IR = infrared spectrometry GC = gas chromatography FID = flame ionization detector NPD = nitrogen-phosphorous detector IDMS = isotope dilution mass spectrometry MS = mass spectrometry. 

MS, Mass spectrometry El, electron impact Cl, chemical ionization MID, multiple ion detection PICI, positive-ion chemical ionization NICI, negative-ion chemical ionization SIM, selected ion nmonitoring TSP, thermospray PPINICI, pulsed positive ion-negative ion chemical ionization ECD, electron-capture detector NPD, nitrogen/phosphorous detector NSTD, nitrogen-selective thermionic detector FT-IR, Fourier transform infrared spectrometry. 

Detector Technology. The second advance in GLC is detector technology. Five detectors are used widely in toxicant detection the flame ionization (FID), flame photometric (FPD), electron capture (ECD), conductivity, and nitrogen-phosphorous detectors. Other detectors have application to toxicant analysis and include the Hall conductivity detector and the photoionization detector. 

Ar-methyl-Ar-(trifluorosily)trifluoracetamide Ammonium hydroxide Nitrogen phosphorous detector Phosphate buffer Propanol... 

A stereoselective GC method for determination of etodolac enantiomers in human plasma and urine was first reported as a preliminary method [35], and then as a validated method [36]. Sample preparation involved addition of (S)-(+)-naproxen (internal standard) and sodium hydroxide to diluted plasma or urine. The samples were washed with diethyl ether, acidified with hydrochloric acid, and extracted with toluene. ( )-(+)-naproxen was used as a derivatizing agent to form diastereomeric derivatives of etodolac. The gas chromatograph system used in this work was equipped with fused-silica capillary column (12 m x 0.2 mm i.d.) coated with high-performance cross-linked methylsilicone film (thickness 0.33 pm) and a nitrogen-phosphorous detector. The operating conditions were injector 250°C detector 300°C column 100-260°C (32 °C/min). 

Traditional detectors (i.e., FID electron capture detector, BCD nitrogen-phosphorous detector, NPD) supply only retention data. However, in many cases this is not enough for proper identification of analytes. Application of GC coupled with an MS detector gives much more information (i.e., the mass spectmm of each compound). GC-MS is a well known and frequently used technique that combines the highly effective separation of GC with the high sensitivity and selectivity of MS. Moreover, improvements in analytical instruments based on different types of mass analyzers (ion trap, quadrupole, and TOF) and the development of hybrid Q-TOF has enhanced the analytical capabilities of modem hardware. Different kinds of mass spectrometers are presented in Table 14.2 [119]. 

Derivatization and Extraction. Modifications of the procedures of Ebeler et al. (49) were used for all aldehyde analyses. Briefly, 3.0 mL of wine were mixed with 60 pL of internal standard (10 mg 2,4,5-trimethylthiazole/mL in 10% aqueous ethanol) and 1 mL of 0.03 M aqueous cysteamine (pH 8.5) the pH was adjusted with HCl or NaOH (pH s from 2-10 were evaluated as discussed below). Following reaction at room temperature for 1 hour, the pH was re-adjusted to 8.5 and the solution was extracted two times with 1.5 mL of chloroform the chloroform layer was removed each time and then combined to give a total of 3.0 mL of extract. Samples were injected onto a gas chromatograph fitted with either a mass spectrometer or nitrogen phosphorous detector. Peak area ratios of the internal standard to the analyte were used for all quantitative calculations. 

Gas Chromatographic Conditions. All analyses were performed on a Hewlett Packard 5890 GC equipped with a 5970 Mass Selective Detector or a Hewlett Packard 6890 GC equipped with a Nitrogen Phosphorous Detector (Hewlett Packard, Inc., Avondale, PA). A DB 35 (35% phenyldimethylpolysiloxane), 30 m x 0.25 mm ID X 0.25 [im column (J W Scientific, Inc., Folsom, CA) was used for all analyses. Carrier gas was helium at a linear velocity of 30 cm/sec. Samples were analyzed using split injections (split ratio = 30 1) with injector and detector (NPD) temperatures of 260°C and 250°C, respectively. Oven temperature programming was as follows initial temperature of 80°C for 1 min increase temperature at 3.5°C/min to 115°C increase at 15°C/min to 180°C increase at 60 C/min to 190°C hold at 190°C for 6 min. 

Figure 6.1 GC and nitrogen-phosphorous-detector (GC-NPD) analysis of a organophosporus insecticides standard solution...

Figure 5.9 (e) Organophosphorous pesticides using a nitrogen/phosphorous detector and splitless injection onto a wide bore column. Rtx-5,30m, 0.53mm i.d., 0.5pm, 100°C, 2°Cmin , to280 C,... 

Let us focus on the WCOT columns used to implement EPA Method 507 Determination of Nitrogen- and Phosphorus-Containing Pesticides in Water by GC with a Nitrogen-Phosphorous Detector . The method is summarized as follows (50) ... 

The connection to an appropriate detector flame ionization detector, thermal conductivity detector, flame photometric detector, nitrogen phosphorous detector (FID, TCD, FPD, NPD, etc.) is achieved via the four- or six-port valve being operated manually or electronically. The carrier gas (helium, nitrogen, argon, artificial air, etc.) flows via the valve only through the sampling column, at low flow rates (e.g., 25 cm /min) held constant during the experiments. 

Whenever possible, avoid using phases containing the specific element which interferes with specific detectors [e.g., do not use cyanopropyl phases with a nitrogen-phosphorous detector (NPDs) or trifluoropropyl phases with an electron-capture detector (BCD)]. 

Quantitative analysis of Ephedra alkaloids using a GC or GC/MS devices is difficult considering their retention time and the task of distinguishing them from diastereomers. Cui et al. analyzed 12 species of Chinese Ephedra by trimethylsilyl (TMS) derivatization of Ephedra alkaloids using a GC/MS device equipped a nitrogen phosphorous detector and helium as the carrier gas with a flow rate of 0.9 mL min the smallest quantity detected by this method was less than 2 ng [5]. 

It is a common opinion of the majority of analytical chemists that GC-based separation procedures should be preferred to LC-based separation procedures, when derivatization or conversion of the analytes of interest is not necessary. The success of the GC technique is also due to the possibility of using selective and robust detectors, such as the electron capture detector (ECD), nitrogen-phosphorous detector (NPD), and, chiefly, the nowadays relatively economic MS detector. 

LOD, limit of detection MS, mass spectrometry ECD, electron capture detector NPD, nitrogen-phosphorous detector. 

The thermionic detector (TID), also known as the nitrogen-phosphorous detector (NPD), is based on the phenomenon that a metal anode emits positive ions when heated in a gas. It is a commonly used gas chromatographic detector for the selective determination of organic compounds containing nitrogen (N) and phosphorus (P) atoms. These include the detection of pharmaceuticals, pesticides, and environmental pollutants. The detector would appear to function as the FID however, its operation is based on a completely different principle. 

Lee and his co-workers (57) combined adsorption chromatography and capillary-column GC to characterize the liquid fraction from the SRCll process. A fused-silica column (20 m x 0.3 mm coated with SE-52) was used along with a flame ionization detector (FID) and either a nitrogen-phosphorous detector or a flame photometric detector. Four hydrocarbon fractions were isolated and characterized. They were found to contain the following functionalities ... 

A selective thermionic specific detector (TSD) was developed by Albert (107) but it is more commonly referred to as a nitrogen-phosphorous detector (NPD). It is basically an alkali FID. Figure 13.36 compares the TSD and the microcoulometric detector. More resolution is obtained through the TSD with elimination of the mixing in the transfer line, reactor tube, and titration cell of the... 

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