Flow injection catalytic spectrophotometric simultaneous determination of nitrite and nitrate

A new flow injection catalytic spectrophotometric method is proposed for the simultaneous determination of nitrite and nitrate based on the catalytic effect of nitrite on the redox reaction between crystal violet and potassium bromate in phosphoric acid medium and nitrate being on-line reduced to nitrite with a cadmium-coated zinc reduction column. The redox reaction is monitored spectrophotometrically by measuring the decrease in the absorbance of crystal violet at the maximum absorption wavelength of 610 nm. A technique of inserting a reduction column into sampling loop is adopted and the flow injection system produces a signal with a shoulder. The height of shoulder in the ascending part of the peak corresponds to the nitrite concentration and the maximum of the peak corresponds to nitrate plus nitrite. The detection limits are 0.3 ng ml⁻¹ for nitrite and 1.0 ng ml⁻¹ for the nitrate. Up to 32 samples can be analyzed per hour with a relative standard deviation of less than 2%. The method has been successfully applied for the simultaneous determination of nitrite and nitrate in natural waters.     

流动注射化学发光法测定痕量NO_2~-的研究与应用

Based on the principle of the reaction of NO2-with I-and formation of I2 in HCl solution,and the chemiluminescence(CL) reaction between luminol and I2 in an alkaline medium.A fairly sensitive,simple and rapid flow-injection analysis-chemiluminescence method for the determina-tion of trace nitrite with the luminal-I——NO2-coupling luminescence system has been developed.Experiment conditions of flow-injection analysis are optimized.When satisfying the condition that Luminol as 4.0×10-4 mol/L,0.7 % KI,0.04 mol/...     

Flow injection kinetic spectrophotometric method for the determination of trace amounts of nitrite

In this work, a new, simple and sensitive flow injection catalytic kinetic spectrophotometric determination of nitrite is reported based on catalytic effect of nitrite on the redox reaction between sulfonazo III and potassium bromate in acidic media. The reaction was monitored by measuring the decrease in the absorbance of sulfunazo III at 570 nm. Various chemical (such as the effect of acidity, reagents concentrations) and instrumental parameters (flow rate, reaction coil length, injection volume and temperature) were studied and were optimized. Under the optimum conditions calibration graph was linear in the nitrite concentration ranges of 8.00 × 10⁻³-3.00 × 10⁻¹ μg/ml (with slope of 2.40) and 3.50 × 10⁻¹-1.80 μg/ml (with slope of 0.42). The detection limit was 6.00 × 10⁻³ μg/ml of nitrite, the relative standard deviation (n = 10) was 1.25% and 0.88% for 5.00 × 10⁻² and 2.00 × 10⁻¹ μg/ml of nitrite respectively. About 60 samples in 1 h can be analyzed. The interfering effects of various chemical species were studied. The method was successfully applied in the determination of nitrite in food and environmental samples.     

流动注射分光光度法测定亚硝酸根氮

使用北京吉天仪器有限公司水质分析仪样机建立了测定水中痕量亚硝酸根氮的流动注射光度方法,以先进的光纤光谱仪CCD作为检测器,亚硝酸盐与对氨基苯磺酰胺重氮化,再与盐酸N-（1-萘基）乙二胺偶合,形成玫瑰红色的偶氮染料,用分光光度法测定,其最大吸收峰在540nm处;最佳的显色管路长度1．5m;最佳的对氨基苯磺酰胺质量浓度为1.0g／L;最佳的N-（1-萘基）乙二胺质量浓度为60g／L,亚硝酸根氮的线性范围为0．002～1．0mg／L,检出限0．37μg／L,RSD0．2％,实际样品的加标回收率均在96.5％～101．2％之间,测定频率60样／h。     

荧光猝灭法测定痕量NO2-

在HCl介质中,NO2-与5-氨基-1,2,3,4-四氢-1,4酞嗪二酮(ATPD)发生亚硝化反应,使ATPD的荧光猝灭,且其荧光猝灭程度与NO2-量呈线性关系,从而建立了测定痕量NO2-的新方法。该法线性范围为0.067~1.172μg/mL,方法检出限为0.70μg/L。本法已用于雨水中痕量NO2-的测定。     

Spectrophotometric simultaneous determination of nitrite, nitrate and ammonium in soils by flow injection analysis

A new rapid flow injection procedure for the simultaneous determination of nitrate, nitrite and ammonium in single flow injection analysis system is proposed. The procedure combines on-line reduction of nitrate to nitrite and oxidation of ammonium to nitrite with spectrophotometric detection of nitrite by using the Griess-llosvay reaction. The formed azo dye was measured at 543 nm. The influence of reagent concentration and manifold parameters were studied. Nitrite, nitrate and ammonium can be determined within the range of 0.02–1.60 μg mL⁻¹, 0.02–1.60 μg mL⁻¹ and 0.05–1.40 μg mL⁻¹, respectively. R.S.D. values (n = 10) were 2.66; 1.41 and 3.58 for nitrate, nitrite and ammonium, respectively. This procedure allows the determination and speciation of inorganic nitrogen species in soils with a single injection in a simple way, and high sampling rate (18 h⁻¹). Detection limits of 0.013, 0.046 and 0.047 μg mL⁻¹were achieved for nitrate, nitrite and ammonium, respectively. In comparison with others methods, the proposed one is more simple, it uses as single chromogenic reagent less injection volume (250 mL in stead of 350 mL) and it has a higher sampling rate.     

离子交换柱后衍生流动注射分光光度在线连续测定水中NO2-和NO3-

建立了连续测定NO2-和NO3-的柱后在线衍生结合流动注射光度分析体系.阴离子交换柱(HPIC-AS3)分离水样中的NO2-和NO3-,洗脱液依次将NO2-和NO3-洗脱流经镀铜镉还原柱,NO3-在线还原为NO2-,与对氨基苯磺酸溶液和N-(1-萘基)-乙二胺溶液合并,在λmax=500 nm处对NO2-和NO3-产生的红色染料进行光度连续检测.NO2-和NO3-的线性范围分别为0.01～1.0mg/L和0.02～2.0 mg/L,检出限分别为0.004和0.008 ng/L.方法用于雨水、湖水和自来水中痕量NO2-和NO3-的同时连续测定.     

Spectrophotometric determination of nitrite in polluted waters using 3-nitroaniline

Nitrite reacts with 3-nitroaniline in the presence of hydrochloric acid to form a diazonium cation, which is subsequently coupled with N-(1-naphtyl)ethylenediammonium chloride to form a stable purple azo dye. The method is suitable for the determination of 0.01–0.80 μg ml^?1 nitrite. The reactions are very fast and require no control of temperature. The observed molar absorptivity and Sandell's sensitivity of the azo dye are 4.9 × 10⁴ l mol^?1 cm^?1 and 9.4 × 10^?4 μg cm^?2, respectively. The method is free from most interferences. The method has been applied successfully to polluted river water.     

吖啶红3B荧光熄灭法测定痕量亚硝酸根

在HCl介质中,吖啶红3B与痕量NO-2发生亚硝化反应,使得吖啶红3B在激发波长为527nm,发射波长为556nm条件下的荧光强度明显下降,其下降程度在一定范围内与NO-2的加入量呈线性关系,从而建立了荧光熄灭法测定痕量NO-2的新方法。方法的线性范围为(4～320)×10-9g/mL,检出限为1.98×10-9g/mL。方法已用于环境水样中痕量NO-2的测定,回收率在95%～105%。     

Flow analysis-vapor phase generation-Fourier transform infrared (FA-VPG-FTIR) spectrometric determination of nitrite

In this work, the coupling between flow analysis (FA)–vapor phase generation (VPG) and Fourier transform infrared spectrometry (FTIR) has been proposed as a novel and alternative strategy for the determination of nitrite. The analyte was transformed into the gaseous nitric oxide (NO) by on-line reaction with potassium iodide (KI) or ascorbic acid in acidic medium. The gaseous NO generated was transported by means of a N₂ gas carrier stream inside the IR gas cell and the corresponding FTIR spectrum was acquired in a continuous mode. The absorbance at 1876 cm⁻¹, corrected by a baseline established between 1879 and 1872 cm⁻¹ at a nominal resolution of 2 cm⁻¹, was selected as a measurement criterion. The effect of different spectroscopic and flow analysis experimental parameters, such as nominal resolution, number of scans, reducing agent and its concentration, acidic medium, reagents and sample flow rates, and the carrier gas flow rate on the analytical signal, and then in the figures of merit were initially evaluated by using a standard short path length (10 cm) IR gas cell. The optimization of the system was carried out by the univariate method. The main aims of this study were: (i) to investigate the on-line generation of gaseous nitric oxide in a continuous flow system, and (ii) the use of Fourier transform infrared spectrometry as an alternative and selective detector for the determination of nitrite. The proposed method was initially tested and applied for the determination of nitrite in samples with very high concentration of nitrite, such as frankfurters.     

流动注射催化光度法测定NO2-的研究

以流动注射分光光度法,基于NO-2在酸性条件中对溴酸钾氧化胭脂红酸有催化作用这一原理测定NO-2。对实验条件进行了优化。实验结果表明,室温下,当cKBrO3=0.14mol L,c胭脂红酸=3.5×10-4mol L,cH2SO4=1.2mol L时,方法的线性范围为0.005～0.3μg mL,检出限为0.002μg mL。利用该方法对几种河水水样进行了测定。     

流动注射光度法测定盐酸普鲁卡因

在盐酸介质中,利用盐酸普鲁卡因－亚硝酸钠－α萘胺的重氨化－偶合反应,建立了流动注射光度法测定盐酸普鲁卡因的新方法。利用控制加 权形心单纯形优化法选择最佳实验条件,测定的线性范围为0－30μg/mL,该法已用于药物中盐酸普鲁卡因含量的测定。     

HPLC荧光法快速检测食品中的NaNO2

建立了HPLC荧光检测法测定不同食品中的NaNO2。碱性条件下以乙酸锌作为蛋白质沉淀剂纯化提取NaNO2。以C8柱作为分析柱,反相C18柱作为预柱,流动相V(水)∶V(乙腈)=60∶40,荧光检测器在激发波长375 nm发射波长415 nm条件下检测,相关系数r=0.9999,方法检出限为0.01 mg/kg,回收率84.6%~103%,相对标准偏差1.0%~5.0%。方法可用于食品中NaNO2的检测。     

Flow injection analysis methods for determination of diffusion coefficients

Two flow injection analyses (FIA) methods for the determination of diffusion coefficients in a straight single tube FIA system were developed. Based on the analytical solution of the convection-diffusion equation, linear relationships of the logarithmic values of the dispersion coefficient (D) and the half-peak width (W_1/2) with the diffusion coefficient (D_m) were obtained. Experiments were designed to verify these methods. For example, for potassium hexacyanoferrate (III) a D_m value of 0.72 × 10⁵ cm² s⁻¹ was found versus a literature value of 0.76 × 10⁵ cm² s⁻¹ (error, 5%). For potassium hexacyanoferrate (II) a D_m value of 0.67 × 10⁵ cm² s⁻¹ was obtained versus a literature value of 0.63 × 10⁵ cm² s⁻¹ (error, 6%). The diffusion coefficients of some important biomedical compounds, such as dopamine, epinephrine, norepinephrine and ascorbic acid, were then determined. The values of 10⁵ D_m/cm² s⁻¹ are 0.60 ± 0.03, 0.44 ± 0.02, 0.60 ± 0.01 and 0.68 ± 0.06, respectively.     

A reversible chemosensor for nitrite based on the fluorescence quenching of a carbazole derivative

The carbazole derivative, with an amino group in 9-position (9-methylacryloylamino carbazole (MAC), has been utilized to prepare a fluorescent sensor and used for the determination of NO₂⁻ based on the reaction between nitrite (NO₂⁻) and excess I⁻ to form I₃⁻, which can quench the fluorescence of carbazole derivative. MAC, as a fluorescent carrier, has a terminal double bond and is covalently immobilized on a quartz glass plate surface by photo-polymerization to prevent the leakage of the dye. The sensor shows sufficient repeatability, selectivity, operational lifetime of 8 weeks, and a fast response of less then 30 s. NO₂⁻ can be determined in the range between 1.0×10⁻⁶ and 1.0×10⁻⁴ mol l⁻¹ with a detection limit of 8.0×10⁻⁷ mol l⁻¹ at pH of 2.0. The quenching mechanism is discussed. Most commonly coexisting ions do not interfer with the NO₂⁻ assay.     

流动注射双安培法测定橙皮甙

基于橙皮甙的不可逆氧化和氧化铂的不可逆还原体系构成了双安培法直接检测橙皮甙的新方法。在外加电压为0.2 V时,通过偶合橙皮甙在一支电极上的氧化和氧化铂在另一支电极上的还原两个不可逆电极过程,构成流动注射双安培检测体系。在pH 8.95的B-R缓冲溶液中,测得橙皮甙的氧化电流与其浓度在6.0×10-6~8.0×10-4mol/L范围内呈良好的线性关系(r=0.9997,n=11),检出限为1.0×10-6mol/L。连续30次测定6.0×10-4mol/L橙皮甙,其峰电流相对标准偏差(RSD)为3.2%,常用药物赋形剂和无机离子均不干扰橙皮甙的测定。方法已用于江中健胃消食片中橙皮甙含量的测定。     

Turbidimetric determination of sulphate in waters employing flow injection and lead sulphate formation

An analytical flow-injection procedure based on PbSO₄ colloidal formation is proposed as a turbidimetric determination of sulphate in natural waters. Ethanol-water was used as a medium in order to improve the sensibility of the method. Both chemical and flow variables as well as interfering species were studied. A detection limit of 0.3 μg SO²⁻₄ ml⁻¹ was found, and the analytical range (according to Beer's law) was 2–20 μg SO²⁻₄ ml⁻¹. The precision was better than 3% R.S.D. and the sample throughput was ca. 35 h⁻¹. The method, when compared with a standard methodology, gave good results when applied to water analysis.     

流动注射化学发光法测定己烯雌酚

基于己烯雌酚对鲁米诺与高碘酸钾在碱性介质中反应产生的化学发光信号有较强的增敏作用,建立了测定己烯雌酚的流动注射化学发光分析法。己烯雌酚质量浓度在13．4—1340μg／L范围内与化学发光强度呈良好的线性关系,检出限（3d）为4μg／L;对26．8μg／L己烯雌酚进行11次平行测定,相对标准偏差（RSD）为1．4％。该法已用于药物制剂中己烯雌酚的测定。     

Flow injection potentiometric determination of clobutinol hydrochloride

New clobutinol (Clob) ion-selective polyvinyl chloride (PVC) membrane electrodes, based on the ion-associates of Clob with phosphotungstic acid or phosphomolybdic acid were prepared using dibutyl phthalate as plasticizing solvent. The electrodes were characterized in terms of membrane composition, temperature and pH. The sensors showed a near-Nernstian response over the concentration ranges (6.31 × 10⁻⁶)-(1.00 × 10⁻²) and (5.01 × 10⁻⁵)-(1.00 × 10⁻²) M in the case of clobutinol-phosphotungstate ((Clob)₃-PT) applying batch and flow injection (FI) analysis, respectively, and (1.58 × 10⁻⁵)-(1.00 × 10⁻²) and (5.01 × 10⁻⁵)-(1.00 × 10⁻²) M in case of clobutinol-phosphomolybdate ((Clob)₃-PM) for batch and FI analysis systems, respectively. The electrodes were successfully applied for the potentiometric determination of ClobCl in pharmaceutical preparation and urine in steady state and flow injection conditions. The electrodes exhibit good selectivity for Clob with respect to a large number of inorganic cations, sugars and amino acids.     

Two rapid and sensitive automated methods for the determination of nitrite and nitrate in soil samples

Spectrophotometric flow injection methods were developed for the individual determination of nitrite or nitrate, and for the simultaneous determination of nitrite and nitrate, in soil samples. Nitrite was determined directly using a modified version of the Griess-Ilosvay diazo-coupling reaction, measuring at 543 nm the absorbance of the azo-dye complex formed. Simultaneous nitrite and nitrate determinations were based on on-line nitrate reduction in a micro column containing copperised cadmium. A single chromogenic reagent containing all the necessary reactants was used in both methods. For determinations, the chemical and instrumental variables were optimised by univariate analysis and simplex chemometric method. The optimised conditions gave a linear calibration range between 0.05 and 1.6 µg m L^− 1 for N-NO₂⁻ and between 0.05 and 7.0 µg m L^− 1 for N-NO₃⁻. The detection limits for nitrite and nitrate were 22 µg L^− 1 and 44 µg L^− 1 respectively. The proposed methods allowed up to 35-40 samples per hour to be analysed with good precision. The simultaneous method was successfully used for the determination of nitrite and nitrate in soil samples (the results obtained were validated against those obtained by reference methods). The proposed methods are simpler and faster than conventional methods and could be routinely used in environmental monitoring laboratories.