Nitration method, determination

To establish the well drainage boundaries and fluid flow patterns within the TFSA-waterflood pilot, an interwell chemical tracer study was conducted. Sodium thiocyanate was selected as the tracer on the basis of its low adsorption characteristics on reservoir rocks (36-38), its low and constant background concentration (0.9 mg/kg) in produced fluids and its ease and accuracy of analysis(39). On July 8, 1986, 500 lb (227 kg) of sodium thiocyanate dissolved in 500 gal (1.89 m3> of injection brine (76700 mg/kg of thiocyanate ion) were injected into Well TU-120. For the next five months, samples of produced fluids were obtained three times per week from each production well. The thiocyanate concentration in the produced brine samples were analyzed in duplicate by the standard ferric nitrate method(39) and in all cases, the precision of the thiocyanate determinations were within 0.3 mg/kg. The concentration of the ion in the produced brine returned to background levels when the sampling and analysis was concluded. 

Chen used a second-derivative spectrophotometric method for the determination of miconazole nitrate in Pikangshuang [22]. Sample of miconazole nitrate was dissolved in anhydrous ethanol and the second-derivative spectrum of the resulting solution was recorded from 200 300 nm miconazole nitrate was determined by measuring the amplitude value between the peak at 233 nm and the trough at 228 nm. The recovery was 99.8% with a relative standard deviation (n = 6) of 0.2%. 

Xue et al. [30] prepared a vaginal suppository formulation containing miconazole nitrate and determined its content by P-matrix ultraviolet spectrophotometry. The production of the suppository was finished with melting by the excipient of glyceryl esters fatty acid of artificial synthesis. Quantitative assay was conducted with a P-matrix ultraviolet spectrophotometer. The suppository was smooth and met the clinical requirement of vaginal disease treatment. The method of assay was accurate. 

Determination in Biological Fluids and Tissues All the advances in pharmacokinetics and drug metabolism described in Sections 7 and 8 would not have been possible without the availability of the proper analytical methods. The following is a tabulation of publications in this field, most of which have already been discussed in Section 5. It should be mentioned that a few publications talk about aspirin blood levels, but really mean salicylate levels. The following tabulation covers only those papers where aspirin was differentiated from other salicylates by chromatography or other means. It seems that the "workhorse" for serum salicylate levels is still the colorimetric (ferric-nitrate) method of Brodie, Udenfriend and Coburn153 published in 1944, or modifications thereof. Simplified versions (cf. 206) may lead to erroneous results under certain conditions.207 The method is also applicable for urinary metabolites after proper hydrolysis (cf. 208). For other methods restricted to salicylic acid, see Section 5.61. 

Bulk physical property tests, such as density and heating value, as well as some compositional tests, such as the Orsat analysis and the mercuric nitrate method for the determination of unsaturation, are still used. However, the choice of a particular test is dictated by (1) the requirements of the legislation, (2) the properties of the gas under study, and (3) the selection by the analyst of a suitable suite of tests to meet the various requirements. For example, judgment by the analyst is necessary whether or not a test that is applied to liquefied petroleum gas is suitable for process gas or natural gas insofar as inference from the nonhydrocarbon constituents will be minimal. 

Stoichiometry Studies. The HCl-NaCl system was studied to determine if Cl" ion was removed stoichiometrically with H30+ as the acid sorption reaction occurred. Two 1-liter solutions were prepared at pCn+ — 3.00 and 10"3Af NaCl two 1-liter solutions at pCH+ = 3.00 and 2 X 10 3M NaCl and two 1-Hter solutions at pCH+ — 2.70 and 10 3M NaCl. A five-gram quantity of coconut-shell carbon was added to each of the pCH+ = 3.00 solutions, and a ten-gram quantity to each of the pCH+ — 2.70 solutions. After one day of stirring, the residual H30+ concentration was measured with a pH meter and corrected for activity, and the residual Cl" ion concentration was determined by means of the Mercuric Nitrate Method (24). The percent stoichiometry was then calculated from the data obtained. 

Keay and Menage [13] have described an automated method for the determination of ammonium and nitrate in 2 M potassium chloride extracts of soil. In this method, a sample of soil (2 g) is shaken for one hour with 2 M potassium chloride (20 ml) and the filtrate is diluted, in the AutoAnalyser, with a 0.25% suspension of magnesium oxide the ammonia evolved is absorbed in 0.1 M hydrochloric acid and determined spectrophotometrically at 625 nm by the indophenol method. The sum of ammonium plus nitrate is determined similarly, but with addition of 4.5% titanous chloride solution before distillation this reduces nitrate but not nitrite. 

Table6.2. Regression equations and correlation coefficients between the three methods for nitrate-nitrogen determination (from [25])...

Standard nitration rates, determined by the method outlined in Chapter 3, are shown in Table 9.7 [75JCS(P2)1600, 75JCS(P2)1624],... 

The nitro group position in the phenyl ring of 3-aryl-4-nitrofurazans during nitration was determined by proton resonance [520], The structure of a large series of 3-(R-amino)-4-nitrofurazans formed by nucleophilic substitution of nitro group in dinitrofurazan with secondary and tertiary amines has been established by H and 13C NMR method [136],... 

The DP results rendered by most of these methods are low and inaccurate, especially when the celluloses are alkali-sensitive, i.e., contain carbonyl groups bringing about chain cleavage in alkaline solutions or active carbonyls, which initiate the stepwise depolymerization of the cellulose chains (known as the peeling reaction) according to the carbonyl elimination mechanism of Isbell et al. [416-420]. The most accurate method for DP determination in all celluloses is the nitration method, in which the cellulose is nitrated in a solution of nitric and phosphoric acids and phosphorus pentoxide, and dissolved in butyl acetate [420-422]. 

Part 13 of ISO 787 determines water-soluble sulfates, chlorides and nitrates. The sample extract can be prepared by either cold or hot extraction method described in Section 4.28. The sulfates in the extract are determined by precipitation with barium chloride, the chlorides are determined by titration with silver nitrate, and the nitrates are determined by a colorimetric method using Nessler reagent." Part 19 gives an alternative method of determination of nitrates by a salicylic acid method. 

Bulk physical property tests, such as density and heating value, as well as some compositional tests, such as the Orsat analysis and the mercuric nitrate method for the determination of unsaturation, are still used. 

Formaldehyde levels are determined by the chromotropic acid method using midget impingers to collect samples. Total oxidant is measured periodically with a coulometric ozone meter (Mast Development Co.). The response of the meter to ozone, nitrogen dioxide, and peroxyacyl nitrate is determined by calibration experiments, and the oxidant level is expressed as ozone, with the contribution of nitrogen dioxide removed. 

Several methods can be used for the determination of chloride in water [2], The argentometric and mercuric nitrate methods are based on the titration of chlorine in the presence of an indicator. Experimental procedures are easy, but many substances may interfere with the results. There are also other methods such as potentiometry, capillary electrophoresis and other automated methods (ferricyanide method or flow injection analysis). 

Silva et al.[44] developed an indirect Fl-AAS method for the determination of nitrate and nitrite in meats and vegetables following liquid-liquid extraction. Nitrate forms an ion pair with bis(2,9- dimethyl-l,10-phenanthrolinato)copper(l) which is extracted into IBMK. Copper is then determined in the separated mganic phase. When the nitrite is oxidized by cerium(VI) into nitrate before the extractirm, total nitrate is determined. When nitrite is ccmverted to nitrogen with sulfamic acid, only the origina] nitrate is determined. 

The comprehensive method determines the nitrogen content for all forms of nitrogen compounds (nitrite, nitrate, urea, organic nitrogen, and ammonia), which upon distillation can be collected in a known amount of sulfuric acid and titrated with sodium hydroxide. A great deal of time is consumed in performing this classical nitrogen method. Note Boric acid may be used for collection of ammonia in the distillation step rather than sulfuric acid. 

Nitrite may be determined by its absorbance at 522 nm after extraction from foods such as cheese or flour and reaction with a color reagent comprising sulfanilic acid and 1-naphthylamine in aqueous acetic acid. Nitrate is determined by this method after reduction to nitrites using cadmium in a modified Jones Reductor as described in AOAC method 976.14. 

Nitrate may also be determined by LC with an anion-exchange column. A comparison has been made between the traditional method of nitrate determination using a reducing cadmium column and spectrophotometric determination with a reversed-phase LC method with orthophosphoric acid adjusted to pH 3.5 with sodium hydroxide as the mobile phase. A high correlation was observed between the nitrate content determined by the two methods. However, LC was found to be more precise, reproducible, and appropriate for routine work. 

Nitrogen-containing species The nitrate content in waters is usually low but can rise to appreciable levels in farming wastewater as a result of soil fertilization. Nitrite originates from the microbiological reduction of nitrate or the oxidation of ammonia. Nitrite is usually determined spectrophotometrically using the Griess reaction. Nitrate is determined by the same method after prereduction to nitrite. 

This analytical instrument was successfully used in several cruises for real-time monitoring of nutrient concentrations in seawater, incorporating a sampling unit for the in situ collection and online determination of phosphate, nitrate, and nitrite. The method is based on the initial determination of phosphate as its phosphoantrmonylmolybdenum blue complex, which is then oxidized online by nitrite and the decrease in absorbance is monitored at 880 nm. Nitrate is determined as the difference between total and initial nitrite content in a separate flow after reduction to nitrite in a cadmium-reductive column. 

Most spectrophotometric methods consist of colorimetric detection of nitrite at 520-540 nm, based on the classical reaction with N-(l-naphthyl)ethylenediamine and sulfanilamide (Griess reaction). Nitrate is determined colorimetrically in the same way after reduction to nitrite by means of a cadmium column (ISO Standard 14673-1 2004/ IDF Standard 189-1 2004). Different SIA systems based on the Griess reaction have been developed for the determination of nitrate and nitrite in infant formulas and milk powder, in dairy samples, in cured meat and infant formulas and milk powder (Oliveira et al., 2004, 2007 Reis Lima et al., 2006 Piston et al., 2011). 

Most FIA methods include the online reduction step (nitrate to nitrite) prior to the color reaction (Griess or other reaction), following the same procedure as in the case of nitrite determination. The sample is then treated with azo dye reagent and the absorbance due to the sum of nitrite and nitrate is measured nitrate is determined from the difference in absorbance values (Figure 7.3) (Ruiz-Capillas et ah, 2006, 2007). In this way, nitrates and nitrites can be determined in the same system. In fact, FIA systems have been developed for simultaneous determination of nitrates and nitrites, with the saving... 

The Food and Agriculture Organization of the United Nations has recommended methods for the determination of mercury in pesticides. The method selected depends on the other constituents of the formulation and in the presence of copper the method of Brookes and Solomon (see p. 419) is most suitable. In the presence of most other constituents the selected method is one in which the sample is refluxed with concentrated sulphuric acid and potassium nitrate before determining the mercury volumetrically with thiocyanate. When large amounts of calcium carbonate or highly chlorinated compounds e,g, benzene hexachloride) are present, the mercury is isolated as a sulphide before conversion to the ionic form with strong acid. 

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