A spectrophotometric method is described for the determination of nitrate in the 0.5 to 50μg range using chromotropic acid as the reagent and masking agents for the elimination of possible critical interferences due to chloride, chlorine, iron(III) and oxidants. The method can be applied directly for the determination of 0.2–20 mg of nitrate/l in 2.5-ml samples of water. Over 4000 mg of chloride/l can be tolerated. The method is simple, rapid and reliable. At the 1 mg/l level for nitrate the coefficient of variation at the 95% confidence limit is 4% There are no interferences. 相似文献
Nitrite and nitrate are used as additives in ham industry to provide colour, taste and protect against clostridia. The classical colorimetric methods widely used to determine nitrite and nitrate are laborious, suffer from matrix interferences and involve the use of toxic cadmium. The use of chromatography is potentially attractive since it is more rapid, sensitive, selective and provides reliable and accurate results. A rapid and cost-effective RP-HPLC method with diode array detector was optimized and validated for quantification of nitrites and nitrates in ham. The chromatographic separation was achieved using a HyPurity C18, 5 μm chromatographic column and gradient elution with 0.01 M n-octylamine and 5 mM tetrabutylammonium hydrogenosulphate to pH 6.5. The determinations were performed in the linear range of 0.0125–10.0 mg/L for nitrite and 0.0300–12.5 g/L for nitrate. The detection limits were 0.019 and 0.050 mg/kg, respectively. The reliability of the method in terms of precision and accuracy was evaluated. Coefficients of variation lower than 2.89% and 5.47% were obtained for nitrite and nitrate, respectively (n = 6). Recoveries of residual nitrite/nitrate ranged between 93.6% and 104.3%. Analysis of cooked and dried ham samples was performed, and the results obtained were in agreement with reference procedures. 相似文献
This study describes a fast and accurate method for the sample preparation, identification, and quantitation of nitrilotriacetic (NTA) acid in environmental aqueous samples at a concentration of ppb level. The method is sensitive, specific, and free from the interferences of fatty and amino acids. The tri-n-propyl- and tri-n-butyl-NTA acid esters were prepared by the reaction of n-propyl-HCl and n-butyl-HCl solutions and NTA acid, respectively. The derivatives were analyzed by a gas chromatograph equipped with a mass spectrometric detector. The method detection limit, 0.006 mg/L of each NTA ester, was determined and validated by an analysis of a fortified water sample. The overall recoveries were 103-115%, n = 8. The method was applied to a real sample and a 0.90 mg/L concentration of NTA acid was found. Mass fragmentation patterns of the derivatives are also reported. 相似文献
The preconcentration of aluminium(III) traces in the form of anionic complexes on an anion-exchanger is described. The ligands used to form anionic complexes are hydroxide, sulphosalicylic acid, chromotropic acid and 2-(4-sulphophenyl)-1,8-dihydroxynaphthalene-3,6-disulphonic acid. Recoveries were evaluated under different conditions and in the presence of potential interferences (surfactants, inorganic salts, organic anions). The experimental behaviour is compared with that which can be predicted from the computed distribution of the different species. The results show that chromotropic acid is superior for the recovery and preconcentration of Al(III). 相似文献
In the present paper, nitrate and nitrite in foodstuffs and saliva were simultaneously determined using a non-suppressed ion chromatography (IC) method with a bulk acoustic wave sensor (BAW) as detector, and 1.5 mmol/L potassium hydrogenphthalate (KHP) as mobile phase. The IC-BAW method is simple, rapid and accurate. The determination limits for nitrite and nitrate are 0.20 and 0.30 mg/L, respectively. The IC-BAW is comparable and agrees with the conventional spectrophotometric method for nitrite and nitrate determination. 相似文献
Modification of the luminol solution by means of addition of various complexones and surfactants has been investigated to eliminate interferences from gaseous co-pollutants in the determination of ambient nitrogen dioxide using a chemiluminescence aerosol detector. The simultaneous presence of EDTA and triton X-100 or X-405 together with sulphite and iodide in the luminol solution suppressed interferences from ozone and peroxyacetyl nitrate to a negligible level and no scrubbers or corrections of the NO2 measurements were needed.
In general, the best composition of the reagent solution included luminol, KOH, Na2SO3, KI, Na2EDTA and triton X-100. From the point of view of selectivity of NO2 determination, an optimum reagent solution consisted of luminol (0.002 M), KOH (0.5 M), Na2SO3 (0.2 M), KI (0.1 M), Na2EDTA (0.05 M) and triton X-100 (0.5 vol.%). Interferences from ozone (170 ppb (v/v)) and peroxyacetyl nitrate (81 ppb (v/v)) were 0.2 and 1.2%, respectively, for nitrogen dioxide at a concentration of 50 ppb (v/v) and 0.25 and 1.7%, respectively, for 0.5 ppb (v/v) NO2. The calibration graph was linear for NO2 concentrations ranging from 3 to 665 ppb (v/v). Below 3 ppb (v/v) NO2 the detector response to nitrogen dioxide can be fitted with a linear equation of the third order. 相似文献
Summary Complexometric titration of thorium with di-sodium versenate solution has been carried out using three dyes: SNADNS, di-SNADNS and nitroso-SNADNS obtained from chromotropic acid. Determinations are suitable with these dyes in the pH range from 2 to 3, the colour changes at the end point are very distinct with nitroso-SNADNS and di-SNADNS while the colour change with SNADNS at the end point is very difficult to detect. Study of interferences revealed that quite a number of elements like, lead, zinc, mercury, cobalt, nickel etc. do not interfere, whereas heavy interference is caused by iron, zirconium, copper, gold and alkaline earths, Thorium may be separated from them by precipitating it with phthalanilic acid obtained from o-anisidine and the thorium salt on breaking with acid may be determined by versene by the same method. This titrimetric method is expected to become more accurate if the final measurement at the end point is made spectrophotometrically rather than visually. 相似文献
l,8-Dihydroxynaphthalene-4-sulfonic acid (DHNS) is described as a new reagent for the extraction—spectrophotometric determination of boric acid. The reagent and its boron complex are extracted into 1,2-dichloroethane as ion-associates with tetradecyldimethyl-benzylammonium chloride (zephiramine). The extracted complex of boron—DHNS—zephiramine has the composition 1:2:3 and is stable to back-washing with 1 M sodium chloride solution (pH 9.2), whereas the excess of reagent co-extracted is removed to the aqueous phase. The apparent molar absorptivity of the complex in the organic phase is 2.45 × 104 l mol-1 cm-1 at 341 nm, which is 1.7 times larger than that with chromotropic acid. Addition of EDTA prevents most interferences. The improved method with DHNS is successfully applied to the determination of boron as boric acid in waters. The exchange equilibrium constants, , for the reagent and complex were also determined for four monovalent anions (X- = Cl-, Br-, NO3-and I-). Some of these constants are compared with those pertaining to chromotropic acid and 1,8-dihydroxynaphthalene. 相似文献
The endogenous nitrate concentration in fresh meat and the residual nitrate and nitrite contents after curing are related to food quality and safety. Most ion chromatography (IC) methods suffer from interferences, especially in fresh meat samples, in which the endogenous nitrate content is low, and in cured meat products, in which other nitrogenous compounds can interfere with the separation of inorganic anions. One of the major classes of interfering compounds in fresh meat are sugar phosphates, which originate from glycolysis during the conversion of muscle glycogen to lactic acid. Nitrate can be separated from interfering compounds with a high-capacity anion-exchange column that was manufactured for use with hydroxide eluents (i.e., hydroxide-selective). This column has a different selectivity than traditional IC columns that use carbonate eluents and facilitates the determination of nitrate in both fresh and cured meats. Nitrate was detected by both suppressed conductivity measurement and mass spectrometry (MS). The identifications of nitrate and glucose-6-phosphate were confirmed by MS detection. The described IC/MS method is robust, sensitive to nitrate concentrations as low as 0.10 mg/kg, and can determine sugar phosphates that are useful for monitoring meat freshness. We successfully used this method to determine nitrate in nearly 100 muscle tissues and cured meat samples. 相似文献
Although anions are usually determined by suppressed ion chromatography (IC), carbonate and bicarbonate ions can not be determined, because a mixed solution of sodium carbonate and sodium hydrogencarbonate is used as the eluent. This paper describes an IC method for the determination of carbonate ion and common anions using an IonPac AG17/AS17 column, an EG 40 eluent generator and a conductivity detector. The proposed IC method could determine carbonate ion and anions within 6 min. The relative standard deviations (n = 5) for chloride (0.4 mg L(-1)), nitrite (0.8 mg L(-1)), carbonate (100 mg L(-1)), nitrate (1.0 mg L(-1)) and sulfate (2.0 mg L(-1)) ions were 5.1%, 1.1%, 4.2%, 5.1% and 1.1%, respectively. In addition, the absorbing solution of carbon dioxide was examined, and 2-amino-2-methyl-1-propanol was found to be a good absorbing solution. The proposed IC method was applied to the determination of carbon dioxide and acid components in flue gas and automobile exhaust gas. 相似文献
A suitable and sensitive ion chromatographic measuring system for determining the main components at nanogram to milligram per liter levels in water samples from the electrodeionization process is presented. A modified Dionex system offers the possibility for the determination of anions and cations in the samples at ng/L, μg/L and mg/L levels. The ng/L level of anions and cations in 20–130 mL high-purity water can be analyzed immediately after preconcentration on appropriate exchange columns. The mg/L level samples are successfully determined by use of an auto-sampler. The quantification of each ion is achieved using the suppressor technique and a conductivity detector. Samples are taken from 5 steps of the electrodeionization process and stored in pre-cleaned FEP (fluorinated ethylene propylene) at 7?°C in darkness prior to the determination of chloride, nitrate, sulfate, carbonate, sodium, ammonium, potassium, calcium and magnesium. Eluents, ultrapure water and samples for the determination of carbonate were passed through special glass containers and flushed with helium gas to avoid the effect of atmospheric carbon dioxide. Results of the investigation of the cationic and anionic composition in water samples within the electrodeionization process are presented and discussed. 相似文献
A facile headspace solid-phase microextraction (HS-SPME) procedure using 85 microm polyacrylate (PA) fiber is presented for the simultaneous determination of preservatives (sorbic and benzoic acids) in food dressing, including Thousand Island Dressing, HellMANN'S Salad Dressing and Tomato Ketchup, by gas chromatography (GC) with flame ionization detector (FID). The method presented preserves the advantages typical of HS-SPME such as simplicity, low intensity of labor, low cost and solvent free. The main factors affecting the HS-SPME process, such as extraction temperature and time, desorption temperature and time, the acidity and salt concentration of the solution, were optimized. Limits of detection (LODs) of the method were 2.00 microg/L for sorbic acid and 1.22 microg/L for benzoic acid. Relative standard deviations (RSDs) for quintuplicate analyses at three concentration levels of 0.10, 2.0 and 20 mg/L ranged between 3.86 and 14.8%. The method also showed good linearity n a range from 0.02 to 40 mg/L with correlation coefficients (R2) of 0.9986 for sorbic acid and 0.9994 for benzoic acid. Recoveries for the two analytes in all the samples tested ranged from 83.44 to 113.2%. Practical applicability was demonstrated through the simultaneous determination of sorbic and benzoic acids in the three complex samples. 相似文献