Simultaneous determination of lithium, sodium and potassium in blood serum by flame photometric flow-injection analysis

A simultaneous flow-injection analysis (FIA) manifold that could analyse three ions from a single injection was designed, constructed, calibrated and used successfully to analyse Li(+), Na(+) and K(+). This FIA method was 10 times faster than the batch technique. The sample volume required was a fraction of about 1/110 to 1/75 that of the batch technique. The outputs were quite reproducible and calibration curves were linear. Results obtained for artificial sera compared favourably with the actual known concentrations of ions and results obtained in the analysis of eight natural human blood sera compared well with those obtained by the traditional batch technique.     

Simultaneous determination of iron and zinc by pH gradient construction in a flow-injection system

A flow-injection method for the simultaneous determination of iron and zinc in the human hair with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) using a pH gradient technique has been developed. The linear range for the determination of iron is 0.1 approximately 1.8 mug ml(-1) and for zinc is 0.2 approximately 5.0 mug ml(-1). About 20 approximately 30 samples can be determined in 1 h. The proposed method is simple, rapid and accurate. It has been applied to the simultaneous determination of trace amounts of iron and zinc in the human hair with satisfactory results.     

Cyclic flow-injection photometric determination of mercaptans in hydrocarbon gases

A procedure for the automated photometric determination of mercaptans in hydrocarbon gases was developed using sodium nitroprusside as a photometric reagent. The analytical range was from 10 to 150 mg/m³ at a sample volume of 0.4 L and preconcentration time of 2 min.     

Multicomponent analysis with a computerized flow injection system using LED photometric detection

An original computer-controlled solid-state photometer has been developed and its potential for simultaneous multicomponent flow-injection analysis of binary and ternary mixtures is demonstrated. The device is simple in construction. Its principle of operation is based on rapid sequential measurements of the absorbance of the complexes formed by the analytes with chromogenic reagents at the wavelengths corresponding to the emission maxima of three light emitting diodes (563, 580 and 638 nm).     

Phosphorescence detection in flowing systems: selective determination of aluminium by flow-injection liquid room-temperature phosphorimetry

The concept of the micelle stabilized liquid room-temperature phosphorescence (MS-LRTP) was applied to the determination of a metal (aluminium) in a flowing system. A three-line flow-injection manifold was developed and various parameters were optimized. A linear calibration graph was obtained for 0–4 μg ml^?1 aluminium. The limit of detection was 50 ng ml^?1 and the relative standard deviations for 0.1 and 1.0 μg ml^?1 aluminium were 2.7 and 1.3% respectively. The proposed procedure is fairly selective. More than 20 common ions studied did not interfere with the determination of aluminium or could be masked by appropriate reagents. The flow-injection method proposed was applied without any preliminary separation to the determination of aluminium in simulated synthetic samples in water and in clinical samples of particular importance in the control of aluminium toxicity in renal failure patients.     

Simultaneous determination of beryllium and aluminium in mixtures using derivative spectrophotometry

The spectrophotometric determination of beryllium and aluminium with 5,8-dihydroxy-1,4-naphthoquinone in the presence of a non-ionic surfactant is reported. Absorption maxima, molar absorptivity and Sandell's Sensitivity of 1:2 (M:L) beryllium and aluminium complexes are, 585 nm and 598 nm, 1.63 x 10(4) l.mole(-1).cm(-1) and 2.04 x 10(4) l.mole(-1).cm(-1), and 0.55 ng/cm(2) and 1.32 ng/cm(2) respectively. Beer's law is obeyed between 7.20-3.96 x 10(2) ng/ml beryllium and 1.08 x 10(1)-1.08 x 10(3) ng/ml aluminium. A method for simultaneous determination of beryllium and aluminium in their mixture using derivative spectra is described. The range 3.6 x 10(1)-3.6 x 10(2) ng/ml beryllium could be determined in the presence of 1.08 x 10(2)-1.08 x 10(3) ng/ml aluminium, and vice versa.     

Simultaneous chemiluminescent determination of carbaryl and 1-naphthol in soils using a flow-injection system

A flow-injection method coupled with the luminol chemiluminescence (CL) detection was developed for the simultaneous determination of carbaryl and 1-naphthol in soils. The method is based on the inhibition of luminol oxidation by the presence of 1-naphthol with the consequent reduction in the CL intensity. The conversion of carbaryl into 1-naphthol was made by the alkaline hydrolysis with NaOH. Under the optimised conditions, the method permits the determination of carbaryl and 1-naphthol over the range 25–400 ng mL^?1 with high determination coefficient using both peak area and height, and high sample throughput (40 h^?1). The detection limits applying the International Unión of Pure and Applied Chemistry (IUPAC) criteria were 65 ng g^?1 and 123.5 ng g^?1 for peak height and area, respectively. A simple extraction procedure employing chloroform as the solvent and sonication was effective for the complete extraction of the analytes present in soils. The method was validated by the analysis of spiked samples, with recoveries between 88.7 and 103.1%. The Flow Injection-Chemiluminescence (FI-CL) method has proven to be simple, fast and accurate for the quantification of carbaryl and its main degradation product in soils.     

Extractive photometric determination of zinc traces in water

Summary Traces of zinc in water are determined by extracting diethyldithiocarbamates into chloroform at about p_H 9, and stripping lead, zinc and cadmium with 0.16M hydrochloric acid. The cadmium is masked with iodide and the zinc determined spectrophotometrically with Zincon at 620 nm. Iron is masked with citrate before the extraction.

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Zusammenfassung Zinkspuren in Wasser werden als Diäthyldithiocarbamat mit Chloroform bei p_H 9 extrahiert. Blei, Zink und Cadmium werden dann mit 0,16-n Salzsäure der Chloroformphase entzogen. Cd wird mit Jodid maskiert und Zink spektrophotometrisch mit Zineon bei 620 nm bestimmt. Eisen wird vor der Extraktion mit Zitrat maskiert.

     

Simultaneous flow-injection determination of chlorpromazine and promethazine by photochemical reaction

Chlorpromazine and promethazine were simultaneously determined by irradiating flow-injection manifolds with ultraviolet light. The simultaneous determination was based on the difference in pH of the media where the photochemical conversion of each phenothiazine into a fluorescent product took place. The choice of the best flow-injection configuration and mathematical treatment for solving the mixtures are discussed. Chlorpromazine and promethazine can be simultaneously determined at the mug/ml level with r.s.d. values between 2 and 4% and sampling frequencies in the range 30-40/hr.     

Simultaneous catalytic-fluorimetric determination of copper and mercury by flow-injection analysis

Summary A catalytic-fluorimetric method is presented for the simultaneous determination of copper(II) and mercury(II) based on their catalytic effects on the oxidation of dipyridyldiketone phenylhydrazone and 2,2-dipyridylketone hydrazone, respectively, using the FIA/ stopped-flow mode. The errors in the determination of these cations are less than 10%, with a sampling rate of 45 samples per hour and the r.s.d. is 0.91% and 1.6% for Cu(II) and for Hg(II), respectively.

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Simultane katalytisch-fluorimetrische Bestimmung von Kupfer und Quecksilber durch Flow-Injection-Analyse

Zusammenfassung Mit Hilfe der FIA/stopped-flow-Technik wurde eine Simultanbestimmung von Cu(II) und Hg(II) durchgeführt, die auf der katalytischen Wirkung dieser Elemente auf die Oxidation von Dipyridyldiketon-phenylhydrazon bzw. 2,2-Dipyridylketon-hydrazon beruht. Die Fehler sind geringer als 10% mit einem Probendurchsatz von 45 Proben je Stunde. Die relative Standardabweichung beträgt 0,91% für Cu und 1,6% für Hg.

     

Simultaneous determination of formaldehyde and methanol by flow-injection catalytic spectrophotometry

A flow-injection method is proposed for the simultaneous catalytic determination of formaldehyde and methanol on the basis of the catalytic action of formaldehyde upon the redox reaction between crystal violet and potassium bromate in a phosphoric acid medium and on-line oxidization of methanol into formaldehyde using a lead dioxide solid-phase reactor. The indicator reaction is monitored spectrophotometrically by measuring the decrease in the absorbance of crystal violet at the maximum absorption wavelength of 610 nm. A technique based on three sampling loops with a single injection valve is developed. The flow-injection system produces a signal of main peak with two shoulders of the same height. The height of the shoulders corresponds to the formaldehyde concentration, and the height difference between the shoulders and the main peak corresponds to the methanol concentration. The detection limit is 0.1 μg/mL for formaldehyde and 1.0 μg/mL for methanol with the sampling rate of 10 samples per hour. The relative standard deviations for 11 replicate determinations of formaldehyde (1.0 μg/mL) and methanol (10 μg/mL) are 1.1 and 2.1%, respectively. The method has been successfully applied to the simultaneous determination of formaldehyde and methanol in some gas samples. The text was submitted by the authors in English.     

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

An automatic direct spectrophotometric method for the simultaneous determination of nitrite and nitrate by flow-injection analysis has been developed. Nitrite reacts with 3-nitroaniline in the presence of hydrochloric acid (0.96-1.8 M HCl or pH 0.5-0.7) to form a diazonium cation, which is subsequently coupled with N-(1-naphthyl)-ethylenediamine dihydrochloride to form a stable purple azo dye, the absorbance of which is measured at 535 nm. Nitrate is reduced on-line to nitrite in a copper-coated cadmium column which 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. A copper column incorporated into the reaction manifold before the copperised cadmium column not only improves the long-term accuracy, but also extends the life time of the copperised cadmium column. Various analytical parameters, such as effect of acidity (pH), flow rate, sample size, dispersion coefficient, time, temperature, reagent concentration and interfering species, were studied. The calibration graphs were rectilinear for 0.1-3.5 mug ml(-1) of NO(3) and 10 ng ml(-1)-2.2mug ml(-1) of NO(2). The method is successfully applied to some food samples (meat, flour and cheese), environmental waters (inland and surface), beer and soil samples. Up to 30 samples can be analysed per hour with a relative precision of approximately 0.1-2%.     

Rapid continuous determination of aluminium in copper-base alloys by flow-injection spectrophotometry

Summary A flow-injection spectrophotometric method has been developed for the rapid, continuous determination of aluminium in copper-base alloys. The system consists of the masking of copper, zinc, iron, etc. with a combined use of thiourea, ascorbic acid and EDTA and the measurement of light absorption of aluminium-Xylenol Orange complex at 506 nm. With appropriate standardization satisfactory results are obtained in spite of sluggish reaction of aluminium and Xylenol Orange. The system allows the analysis of solutions of copper-base alloys for aluminium to be conducted at a rate of 50 determinations per hour without any carryover. The results obtained for standard brasses and aluminium bronze (Al 1.43–10.2%) agreed well with the certified values. The precision (rsd) ranges are 0.2–0.3%.

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Kontinuierliches Schnellverfahren zur Bestimmung von Aluminium in Kupferlegierungen mit Hilfe der Flow-Injection-Spektralphotometrie

Zusammenfassung Bei dem empfohlenen Verfahren werden Cu, Zn, Fe und andere Störelemente mit Hilfe von Thioharnstoff, Ascorbinsäure und EDTA maskiert und der Al-Xylenolorange-Komplex bei 506 nm gemessen. Mit Hilfe eines geeigneten Eichverfahrens werden trotz der trägen Reaktion von Al mit Xylenolorange zufriedenstellende Werte erhalten. 50 Bestimmungen können innerhalb von 1 h ohne jedes Verschleppen durchgeführt werden. Bei der Analyse von Messing und Al-Bronze (1,43–10,2% Al) wurde gute Übereinstimmung mit zertifizierten Werten erzielt. Die Standardabweichungen lagen im Bereich von 0,2–0,3%.

     

Enhanced surfactant determination by ion-pair formation using flow-injection analysis and dynamic surface tension detection

Chemical analysis of surface active species (surfactants) is of interest for many applications, such as in process monitoring, biomedical applications, environmental monitoring and surface science investigations. Recently, we reported a dynamic surface tension detector (DSTD) based upon optically probing the size of a repeating drop resulting from constant flow of an aqueous solvent out of the end of a capillary. Presence of a surfactant in a growing drop reduces the surface tension at the air-solvent interface, causing the drop to detach at a smaller volume, which is detected. The DSTD has a kinetic dependence, and with increasing flow rate the sensitivity decreases due to diffusional and adsorption effects. We report that for the sodium salt of dodecylsulfate (DS), the DSTD performs significantly better with a stainless steel (S.S.) capillary dropper than with a fused silica dropper because the S.S. dropper exhibits a smaller adsorption effect as a function of time. Flow-injection analysis with the DSTD of DS was found to enhance sensitivity 50-fold by in-situ reaction with the ion-pair reagent tetrabutylammonium hydroxide (TBA) in water, even though the TBA alone was not very surface active. The TBA-DS system serves as a model for a selective detection method in which surface activity is exploited and enhanced. The detection limit for DS, as TBA-DS, was 400 ppb. Additionally, weakly surface active species such as TBA could be analyzed "indirectly" by ion-pair formation with DS. The enhanced sensitivity is due to increased packing of the ion-pairs at the air-aqueous solvent interface. The flow rate dependence on the sensitivity of detecting the TBA-DS ion-pair was examined. Two limiting conditions were observed as a function of ion-pair concentration: sensitivity decreases linearly with inverse flow rate at high flow rates and approaches a steady state at slower flow rates.     

On-line determination of residual aluminium in potable and treated waters by flow-injection analysis

A portable, automated, flow-injection-based solid-state spectrophotometric field monitor for the determination of residual dissolved aluminium in potable and treated waters is described. Aluminium is determined by complexation with pyrocatechol violet to form a colloidal lake with a maximum absorbance at 580 nm. Interference from iron(III) is masked by reduction to iron(II) and complexation with 1,10-phenanthroline. The monitor operates on a 30-min analytical cycle, i.e., with 48 results per day, and each cycle includes an autocalibration step. Over the course of a 3-month field trial the reliability was greater than 90%. The performance conforms to industry specifications for both overall accuracy (bias < ± 10%) and repeatability (relative standard deviation < ± 10%), the linear range is 0–1000 μg l^?1 and the practical limit of detection is 45 μg l^?1.     

Simultaneous determination of manganese and zinc in mixtures using first- and second-derivative spectrophotometry

A new direct spectrophotometric determination of manganese with 5,8-dihydroxy-1,4-naphthoquinone (naphthazarin,NAZA) is reported. Absorption maximum, molar absorptivity and Sandell's sensitivity of 1:2 (M:L) complex are 695 nm, 1.88x10(4) l mol(-1) cm(-1) and 2.92 ng cm(-2), respectively. A linear calibration graph is obtained up to a concentration of 7.2 mug ml(-1) of manganese. The optimum range for determination (Ringbom) is between 0.20 and 6.8 mug ml(-1). A rapid method for simultaneous determination of manganese and zinc in their mixture using derivative spectra is described. The range 0.28-5.6 mug ml(-1) manganese could be determined in the presence of 0.33-6.8 mug ml(-1) zinc and vice versa. The developed method was applied to the simultaneous spectrophotometric determination of manganese and zinc in some synthetic mixtures and was found to give satisfactory results.     

Simultaneous determination of multiple components in flow-injection systems by square-wave amperometry

Two or more components can be determined in a single sample by using a flow-injection system with an electrochmical detector, a microprocessor-based potentiostat, and a microcomputer. The computer generates a repeating staircase potential program with a superimposed square wave. Square-wave amperometric measurements at each potential step are used to construct the current/time response at the potential. By appropriate selection of step potentials, the reconstructed response from each step corresponds to the flow-injection response of a particular component. The approach is evaluated by applying it to the simultaneous determination of copper, lead, cadmium and zinc. Limits of detection range from 8 to 18 μg 1^?1. Sample throughput is 80 h^?1.     

Rapid determination of microorganisms using a flow-injection system

An automated method for the rapid determination of microorganisms using a flow-injection system is presented. Electrochemical measurement of a mediator reduced by microbial metabolism allowed the determination of fungi and bacteria in a few minutes. The lowest detection limit was 5 × 10⁶ colony-forming units (cfu) ml^?1 for Escherichia coli. Correlation between the flow-injection method and standard microbiological methods was excellent (r = 0.997, n = 4 for Beauveria bassiana; r = 0.997, n = 7 for E. coli). The flow-injection system was applied to the on-line control of an E. coli cultivation.     

Simultaneous spectrophotometric determination of copper(II) and zinc(II) based on their kinetic separation in flow-injection systems

Flow-injection methods are developed for the spectrophotometric analysis of binary copper(II) and zinc(II) mixtures. They are based on measurements of a differential kinetic signal caused by ligand-exchange reactions that occur in the flow between the complexes of these metals with the same chromogenic reagent (4-(2-pyridylazo)-resorcinol or zincon) and aminopolycarboxylic acids. Two different approaches are used for the kinetic separation (or masking) of these metals followed by the on-line processing of the recorded signal by regression analysis. One of them is monitoring an indicator reaction in the stopped-flow mode, and the other is recording the separated peaks in the flow-injection system with two reaction zones reaching the detector over certain periods. The optimum detection conditions were found (c _min = 0.03 μg/mL), which allow the detection of the studied metal ions in mixtures in a ratio of no more than 1: 5 with a relative error of no more than 5%, good precision (RSD < 10%, n = 6, P = 0.95), and high throughput (90 h^?1). The developed procedures were tested in the analysis of model mixtures and pharmaceutical preparations.