Simultaneous spectrophotometric determination of calcium and magnesium with chlorphosphonazo-III by flow injection analysis

In this flow-injection method, the total concentration of calcium and magnesium is determined by using triethanolamine/hydrochloric acid buffer (pH 7.0) and chlorphosphonazo-III (CPA-III) in the flow streams, and the concentration of calcium alone is determined by using 1.6×10^?3 M hydrochloric acid and CPA-III in the flow treams. At pH 7.0, medium, the linear calibration ranges were 0–2.00 mg l^?1 for both calcium and magnesium and the detection limits were each 0.02 mg l^?1; at pH 2.2, the linear calibration range for calcium and the detection limit were 0.20–2.00 mg l^?1 and 0.1 mg l^?1, respectively. Injection rates are 200 h. The method is suitable for analyzing natural waters.     

Potentiometric and conductometric determination of ammonium by gas-diffusion flow injection analysis

Summary Considerable enhancement of selectivity in the potentiometric and conductometric determination of ammonium is provided by gas-diffusion separation in flow injection analysis. Ammonium and potassium selective liquid membrane electrodes can be used for determinations in the concentration range 10^–7–10^–2 mol/l with high precision and fast sample throughput. No interferences are encountered in the presence of ionic species and molecules that likely adsorb when the sensors are in direct contact with the sample. The selectivity over volatile amines is enhanced due to kinetic discrimination. Conductometric detection is shown to be as sensitive as the potentiometric detection. A major advantage, however, is the linear rather than logarithmic relationship between concentration and conductivity.     

流动注射光度法直接测定海水中的微量苯胺

基于苯胺与亚硝酸盐的重氮化反应及反应产物与甲萘酚的显色,借助流动分析技术,实现了海水中苯胺含量的分析测定。体系以30.9g/L的NaCl做载液、人工海水配制标准样品,对各个影响因素进行了优化。苯胺浓度在0.01～1.0mg/L范围内与相对峰高呈线性关系,线性方程ΔH(mV)=200.53ρ+1.0728(n=8,ρ为苯胺浓度mg/L),相关系数R2=0.9982。方法的检出限(3σ)为0.005mg/L,相对标准偏差(RSD)为4.8%(n=11)。考察了共存离子、不同盐度样品对分析测定的影响。用于实际海水样品的分析,回收率为95.8%～106.6%。     

Simultaneous spectrophotometric determination of nitrite and nitrate by flow injection analysis

The flow injection principle is used in the photometric determination of nitrite and nitrate with sulfanilamide and N-(1-naphthyl)ethylenediamine as reagents. An on-line copper-coated cadmium reductor reduces nitrate to nitrite. The detection limit is 0.05 μM for nitrite and 0.1 mM for nitrate at a total sample volume of 200 μM. Up to 30 samples can be analyzed per hour with a relative precision of ca. 1%.     

Simultaneous spectrophotometric determination of nitrite and nitrate by flow injection analysis.

A new catalytic spectrophotometric method is reported for the simultaneous determination of nitrite and nitrate by flow injection analysis, based on the catalytic effect of nitrite on the redox reaction between pyrogallolsulfonephthalein and potassium bromate in acidic media. Nitrate can also be on-line reduced to nitrite with a modified copper-coated cadmium reduction column. The reaction was monitored spectrophotometrically by measuring the decrease in the absorbance of pyrogallolsulfonephthalein at 465 nm. Various analytical parameters such as effects of acidity, reagent concentrations, flow rates, sample sizes, lengths of the reaction coil and temperatures were studied and were optimized. Under the optimized conditions, the calibration graph was linear for 2.4 to 160 ng ml(-1) of nitrite and 4.0 to 100 ng ml(-1) of nitrate. The influences of potential interfering cations and anions for nitrite and nitrate determination were studied. The method is successfully applied for food and water samples. Up to ten samples can be analyzed per hour.     

Use of diode-array detectors for the simultaneous spectrophotometric determination of calcium and magnesium by flow injection

A method for the simultaneous flow injection spectrophotometric determination of calcium and magnesium with Arsenazo III based on the use of diode-array detector and merging zones is described. The method is applicable to the resolution of mixtures in which the chromogenic reagent has a high absorbance and its spectrum strongly overlaps those of its complexes. In resolving the mixtures, the excess reagent is considered as another component. Quantitation is based on the normal absorbance and first-derivative absorbance spectra. The method is applied to 0.2–1.5 μg ml^?1 Ca and 0.1–1.0 μg ml^?1 Mg. The analysis rate is 50 h^?1.     

Reversed flow injection spectrophotometric determination of chlorate

An interfacing has been developed to connect a spectrophotometer with a personal computer and used as a readout system for development of a simple, rapid and sensitive reversed flow injection (rFI) procedure for chlorate determination. The method is based on the oxidation of indigo carmine by chlorate ions in an acidic solution (dil. HCl) leading to the decrease in absorbance at 610 nm. The decrease in absorbance is directly related to the chlorate concentration present in the sample solutions. Optimum conditions for chlorate were examined. A linear calibration graph over the range of 0.1-0.5 mg L⁻¹ chlorate was established with the regression equation of Y = 104.5X + 1.0, r² = 0.9961 (n = 6). The detection limit (3σ) of 0.03 mg L⁻¹, the limit of quantitation (10σ) of 0.10 mg L⁻¹ and the RSD of 3.2% for 0.3 mg L⁻¹ chlorate (n = 11) together with a sample throughput of 92 h⁻¹ were obtained. The recovery of the added chlorate in spiked water samples was 98.5 ± 3.1%. Major interferences for chlorate determination were found to be BrO₃⁻, ClO₂⁻, ClO⁻ and IO₃⁻ which were overcome by using SO₃²⁻ (as Na₂SO₃) as masking agent. The method has been successfully applied for the determination of chlorate in spiked water samples with the minimum reagent consumption of 14.0 mL h⁻¹. Good agreement between the proposed rFIA and the reference methods was found verified by Student's t-test at 95% confidence level.     

Use of microemulsions in flow injection analysis: spectrophotometric determination of copper

The use of microemulsions as media for liquid/liquid extraction is considered, with particular reference to the copper(II)/2,9-dimethyl-1,10-phenanthroline complex. Aqueous copper(II) standards covering the range 2.5 × 10^?5–7.5 × 10^?3 M were determined by a batch extraction procedure and by three flow-injection extraction procedures, one based on a pre-made water in oil microemulsion, one on a water in oil microemulsion formed on-line and one on an oil in water microemulsion.     

The spectrophotometric determination of hydroperoxide and peroxide in a lipid pharmaceutical product by flow injection analysis

A sensitive, rapid and automatable flow injection analysis procedure is described for the determination of total hydroperoxides and peroxides in lipid products. All unsaturated lipids are susceptible to degradation by oxidation, and the quantification of these major oxidation products is an essential measure of lipid product stability. In this methodology a lipid emulsion is dispersed and injected into an acidic solution of propan-2-ol, which is then merged with iodide ion in situ in a two-stream manifold. The lipid hydroperoxide oxidises acidified iodide to iodine, which is detected spectrophotometrically at 350 nm. The closed conditions prevent interference from atmospheric oxygen and the short reaction time minimises interference from side reactions. Conditions were optimised, using experimental design, for a lipid product under development at GlaxoWellcome. A two-level half-fractional factorial design was applied to screen for the critical factors, followed by a multi-level central composite design to optimise these variables. The resulting method was fully validated and is linear down to 0.1 nmol ml-1. This approach should be applicable to other lipid formulations and offers significant advantages in terms of speed, automation and precision compared with existing manual procedures.     

Simultaneous spectrophotometric determination of uranium and thorium by flow injection analysis using selective masking.

A flow injection system for the simultaneous determination of uranium and thorium has been developed by using selective masking and a spectrophotometric detector with two flow cells aligned with the same optical path. The injected sample solution was first mixed with a reagent solution containing Chromazurol S (CAS) and cetyltrimethylammonium chloride (CTMAC), and the total absorbance of uranium- and thorium-CAS complexes was measured in the first flow cell at 620 nm. The sample stream was then mixed with an EDTA solution in order to convert the thorium-CAS complex to a thorium-EDTA complex, and the absorbance of the uranium-CAS complex was measured in the second flow cell. The detection limits were 10 microg dm(-3) for uranium and 7 microg dm(-3) for thorium. The calibration graphs were linear (r < 0.9998) at least over the ranges of 0.1 to 10 mg dm(-3) for uranium and 0.08 to 8 mg dm(-3) for thorium. The RSDs were less than 1.5% (n = 3) in the calibration range. Uranium and thorium of up to the 6-fold concentration to each other could be determined in admixtures with relative errors of less than 3.3%. The sample throughput was 24 per hour. The proposed system was successfully applied to the analysis of a uranium-thorium ore mock solution by coupling with anion-exchange in a magnesium nitrate medium to eliminate interference from coexisting elements.     

A sensitive spectrophotometric method for lead determination by flow injection analysis with on-line preconcentration

A new flow injection (FI) system for the determination of Pb(II) at trace level with a preconcentration step and spectrophotometric detection is proposed. It is based on preconcentration of lead ions on chitosan and dithizone-lead complex formation in aqueous medium (pH 9). The chemicals and FIA variables influencing the performance of the system were optimized and applied to the determination of lead in natural, well, and drinking water samples. It is a simple, highly sensitive, and low cost alternative methodology. The method provided a linear rage between 25 and 250 μg l⁻¹, a detection limit of 5.0 ng ml⁻¹ and a sample throughput of 15 h⁻¹. The obtained results of spiked samples are in good agreement between the proposed method and ICP-AES.     

A comparison of spectrophotometric and chemiluminescence methods for the determination of blood glucose by flow injection analysis

A flow-injection manifold for the determination of plasma glucose (0–25 mM), incorporating a dialysis unit and a wall-coated enzyme reactor, is described. Spectrophotometric and chemiluminescence methods of detection are compared in terms of precision, accuracy, sample throughput, cost and reliability, and the results obtained from both methods are compared with those obtained from an electrochemical star analyser.     

Potentiometric batch and flow injection analysis of betaine hydrochloride

Novel PVC membrane electrodes for the determination of betaine ion based on the formation of betaine-tetraphenylborate (Be-TPB) and betaine-phosphotungstate (Be-PT) ion-exchangers as electroactive materials are described. The sensors show a fast, stable, near Nernstian response for 6.92 x 10(-6) to 7.94 x 10(-3) M and 1.0 x 10(-4) to 1.0 x 10(-2) M betaine hydrochloride (Be.Cl) in case of Be-TPB electrode applying batch and flow injection analysis (FIA), respectively, and 2.95 x 10(-5) to 2.26 x 10(-3) M and 3.16 x 10(-5) to 1.0 x 10(-2) M in case of Be-PT electrode for batch and FIA electrodes, respectively, at 25 degrees C over the pH range of 3.5-10 with a cationic slope of 60.2 and 59.1 mV decade(-1) and a fast potential response of < or =15 s. The lower detection limits are 7.94 x 10(-6) and 3.18 x 10(-5) M Be.Cl for Be-TPB and Be-PT electrodes, respectively. Selectivity coefficient data for some common inorganic cations, sugars, amino acids and the components other than betaine, of the mixed drug investigated show negligible interference. The electrodes have been applied to the direct potentiometric determination of betaine hydrochloride in water and in a pharmaceutical preparation under batch and FIA conditions. Potentiometric titrations of Be.Cl with NaTPB and PTA as titrants were monitored with the developed betaine electrodes as an end point indicator electrode. The determination of Be.Cl shows an average recovery of 100.8% with mean relative standard deviation of 0.61%. The effect of temperature on the electrodes was also studied.     

Multisyringe flow injection spectrophotometric determination of uranium in water samples

A multisyringe flow injection analysis method for the determination of uranium in water samples was developed. The methodology was based on the complexation reaction of uranium with arsenazo (III) at pH 2.0. Uranium concentrations were spectrophotometrically detected at 649 nm using a light emitting diode. Under the optimized conditions, a linear dynamic range from 0.1 to 4.0 μg mL⁻¹, a 3σ detection limit of 0.04 μg mL⁻¹, and a 10σ quantification limit of 0.10 μg mL⁻¹ were obtained. The reproducibility (%) at 0.5, 2.5, and 4.0 μg mL⁻¹ was 2.5, 0.9, and 0.6%, respectively (n = 10). The interference effect of some ions was tested. The proposed method was successfully applied to the determination of uranium in water samples.     

Some observations on the automation by flow injection analysis of the spectrophotometric determination of amino acids and proteins witho-phthalaldehyde

Automation by flow injection analysis with Spectrophotometric detection of the determination of total amino acids and proteins witho-phthalaldehyde is not straightforward. The use of spectrophotometry, instead of spectrofluorimetry, and of N-acetyl-L-cysteine, instead of the conventional mercaptoethanol is advantageous because of the lower variability of absorptivities with respect to fluorescence yields, and the larger stability of the derivatives. Under adequate working conditions and with leucine as reference, the procedure can be used for the evaluation of total amino acids. A similar procedure is proposed for the analysis of proteins in a sample. Limits of detection are 1 × 10^–5 M for amino acids, and 1 × 10^–6 M for proteins, respectively.     

Rapid spectrophotometric determination of total phosphorus in industrial wastewaters by flow injection analysis including a capillary digestor

The method described is suitable for the rapid determination of total phosphorus in industrial wastewaters. A coiled teflon capillary digestor (10 m long, 1 mm i.d.), which contains a platinum wire as catlyst for oxidation with potassium peroxodisulfate at 160°C, is directly connected to the color-development system based on ion-pair formation between molybdophosphate and malachite green. A single determination of total phosphorus can be completed in 4 min. Calibration graphs are linear for ranges of 0–500 and 10–50 ng ml^-1 phosphorus. The determination limit is 2 ng ml^-1 phosphorus when the sample injection volume is optimized for a given analyte concentration. Applications to seawaters and industrial wastewaters mixed with seawater are discussed. Results are in good agreement with those obtained by the standard method.     

流动注射分光光度法同时测定Fe(Ⅱ)和Fe(Ⅲ)

将流动注射技术引入邻菲罗啉分光光度法测定Fe2+分析体系,采用单阀双带镀镉锌片还原柱带隔离的阀体流路,建立了同时测定微量Fe2+和Fe3+的分析方法。Fe2+的测定范围为0~10 mg/L,检出限为1.2×10-6mg/L;Fe3+的测定范围为0~12 mg/L,检出限为1.8×10-6mg/L。方法用于水中Fe2+和Fe3+的同时测定。     

Potentiometric and spectrophotometric determination of the protonation constant of hexamethylenetetramine

The protonation constant of hexamethylenetetramine (urotropine) was determined by a potentiometric and a spectrophotometric method. The calculations gave log K_HL (concentration constants): 4·89 at μ = 0·1 and 5·05 at μ = 0·5. The temperature was 25° and potassium chloride was used to adjust the ionic strength.