Determination Of Nitrogen Content Research Articles

Quantitative determination of nitrogen content in plant tissue by a colorimetric method

This study was to evaluate the applicability of a colorimetric method in measuring the nitrogen (N) concentration in samples of vegetable origin. In order to do this, the same samples were analyzed with a colorimetric, and macro‐ and microKjeldahl methods. The colorimetric method has been used successfully in the determination of N in nutritional studies with rats and humans. The present procedure has the advantage of eliminating the distillation and titration steps of the Kjeldahl method and it is practical for nutritional studies, since many samples can be run in a single day. The N concentration was measured in leaves of two tropical grasses: Paspalum fasciculatum Willd. ex Flugge and Hyparrhenia rufa (Nees) Stapf, and a Standard Reference Material (SRM 1547 Peach Leaves). In all cases, there were no significant difference (P>0.05) in N concentration in these plant materials using the colorimetric, and micro‐ and macroKjeldahl methods. There was a good agreement between the N concentration of Peach leaves determined by the colorimetric method (2.94%) and the certified N concentration (2.94%). Hyparrhenia rufa, the African grass, and P. fasciculatum, the native species, showed very low N concentration in their leaves, respectively. These results indicate that the colorimetric method, with some light adjustments, is capable of determining the N concentration in plant samples of diverse origin and in very low N levels. The low N concentrations of the grass species suggest the strong limitation imposed by the low soil fertility for the growth and establishment of forage species in tropical savannas.

The determination of nitrogen in Cr-N system by RBS and the weight gain technique

Precise quantitative compositional analysis of hard coatings based on transition metal nitrides and other compounds by means of standard analytical techniques (AES, XPS, EDX, RBS) is possible only using a standard reference material (SRM). However, such standards are still in the course of development. In this paper we show that RBS analysis and the weight gain (WG) technique can be used for the evaluation of atomic concentrations of coating constituents without using an SRM. RBS methods based on the use of two detectors and a sample prepared in the form of a multilayer structure were proposed and tested. Additionally, weight gain measurements were used as a second method to determine nitrogen content in single Cr-N layers. The N/Cr atomic ratio of the as-deposited sample was evaluated from the weight change induced after complete oxidation of the as-deposited films, assuming reactions in which Cr 2O 3 oxide is formed. The results of the two analytical techniques were in very good agreement. The AES depth profile of the same multilayer structure was also measured. All samples were prepared by reactive sputter deposition in a Sputron apparatus at 200 °C.

Indirect and Direct Determination of the Casein Content of Milk by Kjeldahl Nitrogen Analysis: Collaborative Study

The classic method for determination of milk casein is based on precipitation of casein at pH 4.6. Precipitated milk casein is removed by filtration and the nitrogen content of either the precipitate (direct casein method) or filtrate (noncasein nitrogen; NCN) is determined by Kjeldahl analysis. For the indirect casein method, milk total nitrogen (TN; Method 991.20) is also determined and casein is calculated as TN minus NCN. Ten laboratories tested 9 pairs of blind duplicate raw milk materials with a casein range of 2.42-3.05% by both the direct and indirect casein methods. Statistical performance expressed in protein equivalents (nitrogen x 6.38) with invalid and outlier data removed was as follows: NCN method (wt%), mean = 0.762, sr = 0.010, sR = 0.016, repeatability relative standard deviation (RSDr) = 1.287%, reproducibility relative standard deviation (RSDr) = 2.146%; indirect casein method (wt%), mean = 2.585, repeatability = 0.015, reproducibility = 0.022, RSDr = 0.560%, RSDR = 0.841; direct casein method (wt%), mean = 2.575, sr = 0.015, sR = 0.025, RSDr = 0.597%, RSDR = 0.988%. Method performance was acceptable and comparable to similar Kjeldahl methods for determining nitrogen content of milk (Methods 991.20, 991.21, 991.22, 991.23). The direct casein, indirect casein, and noncasein nitrogen methods have been adopted by AOAC INTERNATIONAL.

Total cross section of the 14N(d,pγ) 15N nuclear reaction for analytical applications

In order to supply long-needed basic data for nitrogen determination in thin films by the deuteron induced gamma-ray emission method (DIGE, or d-PIGE), gamma yields of the reaction 14N(d,pγ) 15N were measured by bombarding thin Si 3N 4 films on silicon substrates. The γ-rays were detected by a high efficiency detection system (solid angle around 4π, photo-peak-efficiency 47% for 8 MeV γ-rays) including a 12 in. × 12 in. NaI(Tl) bore hole detector. Total cross section curves for the γ-rays of 7.3 and 8.3 MeV are presented in the deuteron energy range of 500–1500 keV. An example of its use in determining nitrogen content of an ultra-thin silicon oxynitride films is given.

A methodology of measuring nitrogen content in thin nitrogenated carbon overcoats on magnetic thin film media

Thin nitrogenated carbon overcoats were deposited on magnetic rigid disks by unbalanced DC‐magnetron sputtering using a mixture of argon and nitrogen gases. Nitrogen content of nitrogenated carbon is important in determining its tribological performance. Two techniques, including Raman spectroscopy and reflectometry, were evaluated to measure nitrogen content. It will be shown that conventional deconvolution of Raman spectra into D‐ and G‐band cannot be correlated to nitrogen content in thin nitrogenated carbon unambiguously. On the other hand, a trend in the optical constants of nitrogenated carbon will be described that allows rapid quantitative determination of nitrogen content calibrated against ESCA. Measurements of nitrogen content ranging from 0 to 25 at.% will be presented.

Optical characterization of nitrogenated carbon overcoats

Protective wear coatings for disks that incorporate a layer of nitrogenated carbon (CN X) have recently attracted attention. The thickness and nitrogen content of such a layer affects the electrical resistivity, mechanical wear behavior, as well as lubricity and hydroscopic affinity of a disk. An optical methodology will be presented that can measure the thickness and optical constants of such CN X overcoats. The methodology relies on broad-band spectrophotometry and the Forouhi-Bloomer dispersion equations for refractive index ( n) and extinction coefficient ( k). A trend in the optical constants of CN X films will be described that allows rapid quantitative determination of nitrogen content. Measurements of nitrogen content ranging from about 4% to 25% will be presented. Results obtained with this methodology are compared to results from X-ray photoelectron spectroscopy (XPS). Additional outputs of optical spectra are utilized to further elucidate chemical structure.

Microscopic processes during electron cyclotron resonance microwave nitrogen plasma-assisted molecular beam epitaxial growth of GaN/GaAs heterostructures: Experiments and kinetic modeling

A set of δ-GaNyAs1−y/GaAs strained-layer superlattices grown on GaAs (001) substrates by electron cyclotron resonance (ECR) microwave plasma-assisted molecular beam epitaxy (MBE) was characterized by ex situ high resolution X-ray diffraction (HRXRD) to determine nitrogen content y in the nitrided GaAs monolayers as a function of growth temperature T. A first order kinetic model is introduced to quantitatively explain this y(T) dependence in terms of an energetically favorable N for As anion exchange and thermally activated N-surface desorption and surface segregation processes. The nitrogen surface segregation process, with an estimated activation energy Es∼0.9 eV appears to be significant during the GaAs overgrowth of GaNyAs1−y layers, and is shown to be responsible for strong y(T) dependence.

Calibration Method for Determination of Nitrogen Content in Steel by Thermo-Conductimetry after Fusion in the Current of an Inert Gas

A calibration method for determining the nitrogen content in steel by a thermo-conductimetric method after fusion in the current of an inert gas is proposed. In this calibration method, a pure chemical substance whose nitrogen content can be calculated based on its molecular weight is used as a calibrant. The nitrogen recovery and thermostability of 9 chemical substances in the fusion procedure were investigated; it was found that potassium nitrate is the most suitable as a calibrant. The results of analysis of 9 steel samples of certified reference materials demonstrate that the proposed calibration method is applicable to determination of nitrogen contents between 0.001% and 0.5%.

Determination of nitrogen using the 14N(α, p) 17O nuclear reaction

A technique for quantifying nitrogen in thin films using the 14N(α, p) 17O reaction is reported. An incident alpha particle beam with energy near 3.9 MeV is used and emitted protons are detected at a lab angle of 135°. A 15 μm Kapton foil is placed over the detector to stop elastically scattered alpha particles. A thin film containing a known areal density of nitrogen is used for calibration. We present relative yield data on protons from the 14N(α, p 0) 17)O reaction at 135° lab angle from 3.4 MeV to 4.0 MeV as well as an example of the application of this technique in determining nitrogen content in thin films. Possible interfering reactions, particularly 28Si(α, p) 31, are also discussed.

Determination of nitrogen content in thick TiN layers by proton backscattering

Non-Rutherford proton backscattering has been employed for the determination of the nitrogen content in TiN layers of a thickness of several micrometres deposited on a steel backing. The required proton scattering cross section has been measured using standards comprising thin TiN films on a light substrate. The scattering cross section of 2 MeV protons of nitrogen for θ lab = 160° was found to be 5.7 times the Rutherford value. Nitrogen detection limits in thick TiN samples are discussed.

Determination of Nitrogen Content in Milk by the Kjeldahl Method Using Copper Sulfate: Interlaboratory Study

Copper sulfate was substituted for mercury as the catalyst in the International Dairy Federation (IDF) Standard 20A:1986 method for the determination of nitrogen content in milk. The substitution was supported by results obtained in an interlaboratory study by 24 laboratories in 12 countries. Each laboratory analyzed 12 test samples of milk as blind duplicates in a double split level design with high, medium, and low nitrogen concentrations. The method protocol requires the concurrent analyses of an ammonium salt solution and a tryptophan solution as internal quality control standards with a minimum nitrogen recovery between 99 and 100% for the former and at least 98% for the latter. The repeatability and reproducibility relative standard deviations are 0.5 and 1%, respectively, for the range 0.35-0.70 g N/100 g. The performance of the laboratories that did not meet the required quality control specifications was clearly poorer than that of those that did meet the specifications.

Determination of nitrogen content of fats and oils by the method of combustion/ion chromatography

AbstractA method of combustion/ion chromatography (C/IC), initially developed for the determination of sulfur, has been extended to determination of total nitrogen in fats and oils. It is shown that nitrogen gas dissolved in the sample interferes with the determination, and that it is necessary to degas the sample before analysis. Moreover, there is a procedural blank for the nitrogen in the cylinder oxygen employed. Despite these drawbacks, the method has advantages over conventional methods, in that (i) measurements can be carried out with standard laboratory equipment, and (ii) nitrogen and sulfur, and possibly halogens and selenium, can be determined simultaneously.

Spectrographic determination of nitrogen content in petroleum coke

Determinations were made according to the band of cyanogen formed by reaction of carbon with nitrogen in the zone of an ac arc. Spectra were recorded on an ISP-51 spectrograph with a three-lens system of slit illumination. The accuracy of the determination was influenced by the presence of atmospheric nitrogen in the discharge zone and the presence of adsorbed nitrogen in the graphite electrodes, and the samples. The absence of any nitrogen loss in preburning the electrodes was confirmed by data presented in a table. Calibration curves were plotted for raw and calcined coke samples from different sources; results are presented, obtained by the proposed method on raw cokes and compared with results obtained by the Kjeldahl method.

Nitrogen determination using the14N/p, α/11C reaction at low energies

Nitrogen determination with the14N/p, α/11C reaction at 6.81 MeV, has been performed in organic compounds. Positron annihilation from11C allowed determination of nitrogen contents as low as 0.35% dried weight. Comparison of these results with those from the standard Kjeldahl method showed a 0.999 linear correlation coefficient.

Determination of nitrogen by neutron activation in meteorites and rocks

The results of determination of nitrogen content in meteorites by neutron activation are reported. The method is based on the14N(n,p)14C reaction, which occurs upon irradiation of the samples by neutrons. The use of proportional gas-filled countes for the recording of14C made it possible to obtain the low nitrogen detection limit of 0.001 μg.

A study of some nuclear reaction interferences in determination of nitrogen content of plant materials by 14-MeV neutron-activation analysis

The nitrogen content of 10 medicinal plant species has been determined by fast-neutron activation analysis (FNAA). Correction factors for the effects of the 16O(p, α) 13N knock-on proton-induced reaction and the (n, 2n) reactions, which produce interfering positron-emitting radionuclides, have also been determined. The total relative interference from the 16O(p, α) 13N and (n, 2n) reactions of K, Cl, Fe and Br was found to be 5.1–32.1% for the plant samples.

Determination of nitrogen in petroleum crudes and products

This article presents data from a feasibility study of the application of a chromatographic method of nitrogen determination to the analysis of petroleum crudes and products. Even very small amounts of nitrogen will reduce the activity of cracking catalysts and lower the stability of petroleum products in extended storage. The proposed measuring method is based on oxidative breakdown of the organic substances under static conditions in a reactor of the tube type in a bed of heat-resistant oxidizer (NiO). The method can determine nitrogen contents of 0.1% and higher. Advantages of the method include completeness of oxidation of the organic matter, including heterocyclic compounds; a smaller sample weight, which ensures complete decomposition; a shorter time required for analysis; the absence of any particularly toxic reagents; and the elimination of the operations with boiling sulfuric acid. Includes a table.

Sulphate, total sulphur and total nitrogen accumulation by petunia leaves exposed to ozone, sulphur dioxide and nitrogen dioxide

Petunia plants exposed to either 80 pphm sulphur dioxide (SO 2) or to 80 pphm SO 2 with 40 pphm ozone (O 3) for 4 h daily for 4 days accumulated significantly more sulphate-sulphur in their leaves than did those exposed to clean air or O 3 alone. Young leaves accumulated less than middle-aged or old leaves. Cultivar responses depended on relative humidity levels and pollutant composition. Generally, less sulphate-sulphur was accumulated after exposure to the mixture of the two gases than after exposure to SO 2 alone. Leaves exposed to either SO 2 alone or to SO 2 with O 3 and 80 pphm nitrogen dioxide (NO 2) accumulated significantly more total sulphur than those exposed to SO 2 and O 3 or to SO 2 or NO 2. Total nitrogen content of leaves exposed to NO 2 was significantly reduced compared with that of control plants. Sulphate and total sulphur accumulation in petunia leaf tissue may be useful indicators of SO 2 activity but are not good indicators of cultivar sensitivity to SO 2-induced leaf injury. Determination of nitrogen content in petunia leaves is not a suitable method for detecting NO 2 exposure.

High temperature proportional counter designed for conversion electron Mössbauer spectrometry

A new proportional counter for CEMS, in which the sample temperature can be raised up to 740 K, is described. Unlike the reported design by Isozumi et al. [1], where the entire chamber was heated from outside, only the sample and sample holder as well as the flow-gas were heated in the present design. Counting characteristics of several flow-gases were compared at room temperature and at 507 K, and 90%He/10%CH 4 gas was found to give the most stable counting. Promising applications of the counter are demonstrated by presenting the CEM spectrum of the stainless steel surface at 738 K, the comparison of Mössbauer parameters of α-iron for TMS and CEMS up to 600 K and the determination of nitrogen content together with the chemical states of iron in the ion nitrided steel surface.

Determination of Nitrogen Concentration in GaP Epitaxial Layers by Two Independent Methods

AbstractThe nitrogen concentration in GaP is determined by optical absorption in the A‐line at T = 77 K. The concentration of the isolated nitrogen atoms is given for T = 77 K by the modified LIGHTOWLERS' relation [NA] cm−3 = 8.2 · 1014 phαmax, where α is measured in cm−3, h in meV. p is a dimensionless line shape factor. It is shown that at higher N concentrations considering only the A‐line absorption the impurity density is underestimated because the nitrogen atoms included in NNi pairs give no contribution to the absorption. The measurements have been made in the range from [N] = 5 · 1016…︁ 1019 cm−3 in layers grown by vapour phase epitaxy. The results are compared with nitrogen concentrations obtained by precision lattice parameter measurements. The change of the lattice parameter is calculated using VEGARD's law. The good agreement between the nitrogen densities obtained by two different independent methods reveals (i) that the LIGHTOWLERS' calibration factor is valid also at higher N‐concentrations and (ii) that the nitrogen atoms are predominantly incorporated into P‐lattice sites.