Flow injection analysis : Part II. Ultrafast determination of phosphorus in plant material by continuous flow spectrophotometry

The effect of sample volume, tube length, tube diameter, peak height and sampling rate on the determination of phosphorus in acidic plant digests was investigated, and optimal conditions for the flow injection method are described. Sampling rates of 420 samples per hour were achieved without incurring problems from carryover of samples, and evidence was obtained that rates as high as 700 samples per hour are possible. The flow injection method was proved to be suitable for routine analyses and has obvious advantages over other automated or manual methods in sampling rate, simplicity of design and cost.     

The Determination of Trace Amounts of Phosphate in Natural Water by Flow Injection Fluorimetry

Abstract

A new method is suggested for the determination of trace amounts of phosphate by flow injection fluorimetry, based on the principle that molybdophosphate could quench the fluorescence of Rhodamine 6G. The fluorescence is excited at 350 nm and measured at 550 nm. The calibration graph is linear up to 100 ng/ml phosphorus concentration and the detection Unit is 1.9 ng/ml. The present method has been applied to the determination of soluble phosphorus in natural water samples, the recoveries were in the range of 92 – 102 %. The sampling rate is 120 samples per hour.     

Flow injection analysis : Part VI. The determination of phosphate and chloride in blood serum by dialysis and sample dilution

The rapid determination of chloride and inorganic phosphate in blood serum based on continuous flow spectrophotometry was adapted to Flow Injection Analysis by applying dialysis as well as differential dilution of the injected samples. In addition to the manual injection procedure, an automated microsampling unit was developed and used. By continuous dialysis, chloride could be determined reproducibly at a sampling rate of 125 samples per hour at sample volumes of 60 μl or less. A similar sampling rate and high precision were obtained for the determination of inorganic phosphate by using differential dilution.     

流动注射在线离子交换预富集-氢化物发生原子荧光光谱法测定痕量碲的研究

研究了流动注射在线离子交换预富集及在线氢化物发生法与原子荧光光谱法的联用技术。设计了双柱交替正向富集和反向洗脱的在线离子交换流路系统。在采样频率为３０次／ｈ下，灵敏度较常规流动注射氢化物发生原子荧光光谱法提高１１倍。应用于环境水样中痕量碲的分析，获得了满意的结果。     

Flow injection analysis: Part VIII. Determination of glucose in blood serum with glucose dehydrogenase

The flow injection principle is used for enzymatic determination of glucose in blood serum with glucose dehydrogenase. Methods based on single-point determination on deproteinized serum samples, single-point determination comprising continuous flow dialysis, and two-point kinetic assay, are described and discussed. Special consideration is given to optimizing the flow parameters in order to minimize reagent consumption, yet to maintain a high sampling rate. Thus, for the single-point determination, a sampling rate of 120 samples per h was achieved at an expenditure of 3.12 g-units of glucose dehydrogenase per sample.     

Flow injection of lithium ion using chromogenic 14-crown-4 derivatives as extraction-spectrophotometric reagents

A system for flow injection of Li+ has been designed, with use of proton-dissociable chromogenic 14-crown-4 derivatives as the extraction-spectrophotometric reagents, and the analytical conditions have been optimised. This flow injection system showed high selectivity for Li+ reflecting the cation-complexing property of the chromogenic crown ethers. The determination of Li+ in the clinical range in blood under a high Na+ background of 130-160 mM was feasible, with a small sample size (50 microliters) and high sampling rate (more than 100 injections per hour), with this method. The proposed extraction-spectrophotometric flow injection system was, therefore, found to be promising for the efficient determination of Li+ in biological samples, such as blood sera, with a high Na+ background.     

Determination of hydrogen peroxide in reactor moderator solutions by flow injection analysis

A flow injection analysis (FIA) method for the determination of hydrogen peroxide in reactor moderator water has been developed and installed at the Savannah River Site (SRS) Water Quality Laboratory. The mode of detection is amperometric and the technique has an analytical range of 0.10-2.50 mug/ml with a sampling rate of 40 samples/hour. The calibration curve is linear with a correlation coefficient of 0.999 and the relative standard deviation is at the 0.50% level for both 0.10- and 2.50-mug/ml standards. When the FIA procedure is compared to the manual method previously used at the SRS Water Quality Laboratory for hydrogen peroxide analysis, it demonstrates a minimum twenty minute reduction in analysis time per sample and the total liquid waste generated per sample analyzed is reduced by 95%.     

Sequential determination of iron and titanium by flow-injection analysis

A flow-injection method has been developed for the sequential spectrophotometric determination of iron and titanium using 3,4 dihydroxybenzoic acid as chromogenic reagent. The system involves the sequential measurement of the absorbances of the complexes at 380 and 570 nm. The system is designed using a simultaneous injection of sample and reagent into separate carrier streams. The proposed method is characterized by a precision of about 2%, a sampling rate of about 50 samples per hour, and a reagent consumption of 200 mul (0.50% solution) per sample. It is relatively free of interferences and was used for the sequential determination of titanium and iron in rocks.     

Flow Injection Catalytic Determination of Vanadium using the Indicator Reaction between Victoria Blue B and Bromate and A Citric Acid Activator

ABSTRACT

A flow injection catalytic method is proposed for determination of trace vanadium based on its catalytic action on a new indicator reaction between Victoria blue B (VBB) and potassium bromate in the presence of citric acid as an activator and in dilute sulfuric acid medium. The reaction is monitored spectrophotometrically by measuring the decrease in absorbance of VBB injected at the maximum absorption wavelength of 618 nm. The detection limit is 0.5 ng ml^?1 and is independent of the initial valence state of vanadium. The relative standard deviation is 1.5% obtained from 11 standard solutions each containing 40 ng ml^?1 of vanadium. The sampling rate is about 15 samples per hour. This method is very simple and has been applied to the determination of trace vanadium in some natural waters with recoveries of 93-103%.     

Ion exchange in flow injection analysis: Determination of Ammonium Ions at the μg 1-1 level in Natural Waters with Pulsed Nessler Reagent

Ion exchange is incorporated in flow injection analysis by using a resin column in the sample loop of an electronically operated proportional injector. Effects of sample aspiration rate, sampling time, eluting agent concentration, pumping rate of the sample carrier stream, resin column size and sample acidity, were investigated to develop a preconcentration procedure for ammonium ion determination in natural waters at the μg 1^-1 level with pulsed Nessler reagent. The possibility of sample buffering before the adsorption step was studied. The proposed method is characterized by a precision of about 2%, a sampling rate of about 40 samples per hour. and a reagent consumption of 40 μl per sample, and is almost free of interferences. Recoveries from 95 to 105% were achieved in analysing rain-water samples with ammonium contents of less than 200 μg 1^-1. Alternative flow diagrams and the injector command unit are discussed.     

Rapid determination of some 1,4-benzodiazepines by flow injection analysis

The rapid determination of three 1,4-benzodiazepines (lorazepam, bromazepam, and chlordiazepoxide) by spectrophotometry has been adapted to flow injection analysis. The effects of flow rate and manifold design on the determination are studied. At sampling rates of 120 samples per hour high reproducibility of measurements (relative standard deviations below 1.5% are obtained with 200-μ1 injection volumes) and low reagent consumtions were achieved. The system was applied to determination of these 1,4-benzodiazepines in pharmaceutical formulations and human urine.     

Automated simultaneous determination of nitrate and nitrite by pre-valve reduction of nitrate in a flow-injection system

Nitrate is reduced to nitrite by using the pre-valve in-valve reduction technique prior to the sampling system. One loop of a two-position sampling valve is replaced by a copperised cadmium column. Nitrite from the samples as well as nitrite formed in the reduction procedure is sampled by a second valve and introduced into the flow system. The two sampling valves are synchronised in such a way that two peaks are obtained, one corresponding to the nitrate plus nitrite and the other to the nitrite only. The method is suitable for the simultaneous determination of nitrate and nitrite at a sampling rate of up to 72 determinations per hour with coefficients of variation better than 1.96% for nitrate and 0.83% for nitrite.     

Indirect Spectrophotometric Determination of Fluoride In Water With Zirconium-Spadns By Flow Injection Analysis

Abstract

The zirconium-SPADNS method for the determination of fluoride based on the effect of fluoride ion on the color system (Zr-SPADNS), has been adapted to the continuous flow spectrophotometry. A manifold consisting of two lines was used. the decrease in the absorbance of Zr-SPADNS reagent at 590 nm is linear with fluoride concentration in the range 0.00-3.5 ppm. the method has a detection limit of 0.02 ppm fluoride. At a sampling rate of 50 determinations per hour, the precision was about 1% relative standard deviation. the method is applied to the determination of fluoride in natural water samples. the good agreement between the results obtained by this method and those obtained by a potentiometric method using a fluoride ion-selective electrode, show that the new method is potentially suitable for routine analysis. the effects of reaction conditions, flow parameters, and interferences on the FIA-spectrophotometric signals are reported. amount of interfering ion is present in quantity great enough to produce an error of 0.1 ppm or more, the sample must be distilled¹⁷     

流动注射比浊法测定人体血清总蛋白

基于磺基水杨酸 硫酸钠混合试剂与蛋白质发生浊度反应,设计了具有一个汇合点的FIA单道流路,运用正交实验优化了影响比浊反应的主要因素,并探讨了流动注射分析条件,从而提出了流动注射比浊法测定人血清中总蛋白的新方法。本法实验结果与双缩脲法一致,每小时进样60次,线性范围为0.14～1.40mg mL。     

Isothermal distillation in flow injection analysis: Determination of total nitrogen in plant material

An isothermal distillation unit is incorporated in flow injection systems. The influence of surfactant, flow rates, alkalinity, ionic strength, collector stream pH, reagent concentration and sample volume in ammonia distillation are discussed. A method for the determination of total nitgrogen in plant digests employing Nessler reagent is proposed. This method, based on merging zones approach, is characterized by a sampling rate of 100 samples per hour, a precision better than 3%, a reagent consumption of only 100 μl per sample and virtually no base-line drift. The results agree with those obtained with the indophenol blue colorimetric method. The incorporation of isothermal distillation in flow systems with potentiometric measurement is also described.     

A simple simultaneous flow injection method based on phosphomolybdenum chemistry for nitrate and nitrite determinations in water and fish samples

A direct spectrophotometric flow injection method for the simultaneous determination of nitrite and nitrate has been developed. The method is based on the oxidation of a phosphomolybdenum blue complex by the addition of nitrite and the decrease in absorbance of the blue complex is monitored at 820 nm. The injected sample is split into two segments. One of the streams was directly reacted with the above reagent and detected as nitrite. The other stream was passed through a copperised cadmium reductor column where reduction of nitrate to nitrite occurs, and the sample was then mixed with the reagent and passed through the cell of the spectrophotometer to be detected as nitrite plus nitrate. The conditions for the flow injection manifold parameters were optimised by experimental design and the concentration of nitrite and nitrate was determined in the linear range from 0.05 to 1.15 mug ml(-1) nitrite and 0.06 to 1.6 mug ml(-1) nitrate with a detection limit of 0.01 mug ml(-1) for nitrite and 0.025 mug ml(-1) for nitrate. The method is suitable for the simultaneous determination of nitrite and nitrate in fish and water samples with a sampling rate of 25+/-2 sample per hour.     

Automatic Multipumping Flow System for Handling Viscous Solutions: Application to the Spectrophotometric Determination of Trimipramine

Abstract

The present work describes the implementation, by using MultiPumping Flow Analysis System (MPFS), of a spectrophotometric method for the determination of trimipramine in commercially available pharmaceutical formulations, based on the reaction with ammonium monovanadate in acidic medium yielding a colored compound with a maximum of absorbance at 620 nm. The improved flow mixing conditions during sample and reagents insertion and transport, as a result of the chaotic movement of the solutions originated by the MPFS pulsed flow, assured a fast reaction zone homogenization in a reduced residence time, which was particularly advantageous for carrying out analytical determinations that involved highly viscous solutions, as is the case of the sulfuric acid solution used in the determination of trimipramine, without impairing the sampling rate.

A linear working range for trimipramine concentrations of up to 50 mg L^?1 (r = 0.9998; n = 6) was obtained, and the determined detection limit was about 1.15 mg L^?1. The sampling rate was approximately 50 determinations per hour. The obtained results were in agreement with those furnished by the reference procedure, with relative deviations lower than 4.7%. With the developed MPFS, the consumption of the reagents ammonium monovanadate and sulfuric acid was reduced by approximately 41.02% and 54.29%, respectively, compared with a previously proposed multicommutated flow analysis system.     

Determination of gaseous carbonyl compounds by their pentafluorophenyl hydrazones with gas chromatography/mass spectrometry

A sensitive and reliable method has been developed for the simultaneous determination of 20 airborne carbonyl compounds in the C₁-C₁₀ range. The carbonyls were collected onto solid sorbent coated with pentafluorophenyl hydrazine (PFPH), followed by solvent extraction and gas chromatographic (GC)/mass spectrometric (MS) analysis of the PFPH derivatives. The sorbent is packed into two separate sections in a glass sampling tube. The two-section design allows convenient checking of collection efficiency and breakthrough. The sampling tube, with a coating amount of 971 nmol PFPH per 100 mg Tenax TA and operated at a sampling flow rate of 80 mL min⁻¹, collects the 20 carbonyls with efficiencies above 95%. Hexane extracts the collected carbonyls in their PFPH derivatives in the sampling tube with better than 95% extraction efficiency. It is necessary to let the sampling tube sit at ambient temperature for 3 days before solvent extraction to ensure complete derivatization of the carbonyls. The limits of detection (LODs) of the tested carbonyls are in the range of 3.7-11.6 ng per sample. The method has been field-tested both in ambient environment and in an indoor environment from burning mosquito-repellent incense. Eighteen carbonyls were detected in the ambient air samples with the exception of o-tolualdehyde and m-tolualdehyde, while all the 20 target carbonyls were found in the incense smoke. Compare field test with classical DNPH-HPLC/UV method, good agreement exited between the two methods for lower molecular carbonyls but PFPH method is found to be a better analytical method for determination of high molecular weight carbonyls.     

A versatile set up for implementing different flow analysis approaches: Spectrophotometric determination of nickel in steel alloys

An arrangement capable of implementing the four principal types of flow analysis processes, monosegmented flow analysis (MSFA), flow injection analysis with multicommutation and binary sampling (FIA-MBS), flow injection analysis with sandwich sampling (FIA-SS) and sequential injection analysis (SIA) is described. The core of the flow manifold is a six-way solenoid valve that is assembled together with three three-way solenoid valves in order to provide a versatile flow network. Software was written in VisualBasic 3.0 to give a friendly working structure allowing the user to easily choose the flow variables and the kind of flow system. The reliability of the flow set up for implementation of the four flow analysis systems was evaluated by means of the spectrophotometric determination of nickel in steel alloys, based on the formation of a colored complex with dimethylglyoxime (DMG). The performances of the four different flow methodologies were compared. The reagent consumptions per determination were 4.0 mg of triethanolamine, 6.0 mg of potassium persulfate and 0.6 mg of DMG. When the flow set up was instructed through the software to implement MSFA, FIA-MBS, and FIA-SS approaches, a sampling frequency of 40 samples/h was obtained, while 30 samples could be processed per hour in the SIA mode. The precisions, evaluated as the relative standard deviation of ten determinations were 0.7%, 1.6%, 1.8% and 3.1% for the MFSA, FIA-MBS, FIA-SS and SIA systems, respectively. The results for determination of nickel in steel alloys presented good agreement with the reference method (ICP OES), showing no significant difference at a confidence level of 95%.     

Determination of trace sodium in the water-steam system of power plants using an FIA/ISE method with an automatic penetration and alkalization apparatus.

A new method for the rapid determination of trace-level sodium ion based on flow-injection analysis (FIA) and an ion selective electrode (ISE) is proposed. Various effects on the sensitivity of the method such as the flow rate and alkalinity of the carrier, sampling volume, temperature, length of reaction coil, length and thickness of alkalization tube, concentration of the alkalizing reagent etc. were investigated. The optimum conditions were ascertained. The method showed good linearity in the concentration ranges of 0.5 - 10 microg L(-1) and 10 - 100 microg L(-1), and could deal with 40 - 50 samples per hour. The consumption of the sample is only 0.80 mL per time. The relative standard deviation was 0.55%, and the recovery range was 98 - 103%. By designing a hermetically sealed single-line FIA-ISE manifold, a problem removing the interference of sodium ion from air could be solved, and automatic alkalization of the sample was realized. This method has been used for successfully determining the trace-level sodium ions in the water-steam system at fossil power plants.