流动注射分析中试样分散的对流-扩散理论

用两种方法求解适合于单一平直管道且无化学反应的流动注射分析(FIA)体系的对流-扩散方程,得到了描述塞状进样在管道中分散后的浓度分布公式,从而得到F曲线。讨论了反应管和采样管的内径和长度、流速和扩散系数对峰形和分散度的影响;采用数值法解出半峰宽与扩散系数的关系,提出了两种测定扩散系数的方法,为FIA体系的设计和指示物质、操作条件的选择提供了理论依据。     

Segmental flow-injection analysis: device and applications

A segmental flow-injection system which possesses features of both flow-injection analysis (FIA) and continuous-flow analysis (CFA) has been built. The whole sample zone is segmented by only two air bubbles. A valve has been designed to inject the sample and the bubbles into the carrier stream in a quantitative way. The position of the segmentation can be accurately controlled and the amount of the air introduced is minimized (only 5% of the bubbles in CFA) so that the stability of flow-rate can be improved. In this system, longer residence times (10 min or more) and higher reaction temperatures (up to 95 °C) can be obtained without loss of peak height or loss of sampling frequency in comparison with FIA. Owing to the good reproducibility the determination can still be performed when the equilibrium stare is is not obtained. The determination of total amino acids in tea with ninhydrin reagent, ammonia in natural water with phenol-sodium hypochlorite reagent and trace amounts of Cu(II) and V(V) by means of catalytic spectrophotometry are given as examples.     

Spectrophotometric determination of silicon in silicates by flow-injection analysis

A flow-injection spectrophotometric method has been developed for the accurate, continuous determination of silicon in silicate rocks. A rock sample solution is prepared by fusion with a 1:1 mixture of lithium carbonate and boric acid and subsequent dissolution of the cake in 1 M hydrochloric acid. The preparation technique is the same as that used for the determination of total iron, aluminium, calcium, titanium, and phosphorus in silicate rocks by flow-injection spectrophotometry. Because of the marked polymerization of silicic acid in acid solution, silicic acid is depolymerized in alkaline medium after a simple cation-exchange column filtration of the rock sample solution and then determined by a static or an FIA spectrophotometric method. The FIA system consists of two channels which carry the carrier solution and molybdate reagent, and allows the colour reaction to proceed under controlled conditions. The FIA system permits high throughput of 70 samples per hour. The procedure has been applied to a variety of standard silicate rocks of the U.S. Geological Survey and the Geological Survey of Japan, and gave satisfactory agreement with the recommended values.     

Acridinium ester chemiluminescence: pH dependent hydrolysis of reagents and flow injection analysis of hydrogen peroxide and glutamate

An automated analysis system is described for the measurement of hydrogen peroxide based on a chemiluminescence reaction with phenyl 10-methylacridinium-9-carboxylate (PMAC). A reversed FIA experimental arrangement is used to establish the operating conditions for the measurement of submicromolar levels of hydrogen peroxide. The carrier stream consists of hydrogen peroxide standards prepared in a pH 9.0, boric acid buffer and the flow rate for this carrier/sample stream is 4 ml/min. Twenty microliters of a 10 mM PMAC solution, prepared in a pH 3 phosphate buffer, are injected into the carrier/sample stream. Hydrogen peroxide mixes with the PMAC reagent in an incubation coil that is constructed by wrapping 107 cm of polyethylene tubing around a 1 cm o.d. plastic rod. The chemiluminescence reaction is then initiated by adding base just before the sample passes in front of a photomultiplier tube (PMT) detector. The calculated limit of detection (S/N = 3) for hydrogen peroxide is 0.25 M. In addition, the pH dependent hydrolysis of the PMAC reagent is characterized by an HPLC method which has been specifically developed for the separation and detection of the hydrolysis products of PMAC. Results indicate that a pH of 3.0 is required for long term stability of the PMAC reagent. Finally, this system has been successfully extended to the measurement of glutamate by coupling a bioreactor column of glutamate oxidase with the hydrogen peroxide detection scheme. A detection limit (S/N = 3) of 0.5 M has been established for glutamate with a throughput of 200 samples per hour.     

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.     

Spectrophotometric determination of iron with ferrozine by flow-injection analysis

Two methods for the determination of iron by normal FIA and reversed FIA were developed using sodium 3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine-4',4'-disulphonate (ferrozine). The reagent formed a chelate with Fe(II) in hexamethylentetramine buffered medium at pH 5.5. In one previous reaction coil Fe(III) was reduced to Fe(II) by ascorbic acid and in the other reaction coil the complexation reaction was developed. The linear range of the determination was 0.5-6 and 0.1-5 mug ml(-1) of iron for normal FIA and reversed FIA respectively. The proposed method was sensitive (detection limit 0.012 and 0.010 mug ml(-1)), rapid and reproducible (RSD 0.3 and 0.28%). The method was satisfactorily applied to the determination of iron in waste water, toadstool tissue, potato leaves, human hair and bauxites at a sampling rate of 90 and 50 samples h(-1) for normal FIA and reversed FIA respectively.     

Chemiluminescence Flow-Injection System for Rapid Detection of Red Tide Phytoplankton

Abstract

A chemiluminescent flow-injection analysis (FIA) system for the detection of the red tide phytoplankton Chattonella antiqua has been developed based on a Cypridina luciferin analog, 2-methyl-6-(p-methoxyphenyl)-3,7-dihydroimidazo[1, 2-α]-pyrazin-3-one (MCLA), which strongly emits light at 465 nm in the presence of superoxide. The system consisted of a two reagent feeding stream, a sample injector, a joint for mixing MCLA and sample, a chemiluminescence (CL) reaction cell, a CL detector and a recorder unit. The response time is approximately 1 min for one measurement cycle. The FIA system has an optimum pH of 10.7. The calibration curves for C. antiqua displayed linearity from 2 × 10³ to 2 × 10⁴ cells ml^?1. When applied to the measurement of C. antiqua, the sensitivity obtained using the FIA system is approximately 10 times higher than that of the cytochrome c method. The FIA system is a rapid practical method for the detection of C. antiqua.     

Adaptation of a commercial ion selective fluoride electrode to a tubular configuration for analysis by flow methodologies

The determination of fluoride ions in water samples is accomplished by using a tubular flow through detector constructed by drilling a channel through a commercially available LaF(3) crystal electrode in such a way that the original contacts of the non-modified unit are maintained. Its performance when incorporated in both FIA and SIA systems was evaluated and the results show that the tubular unit retains the characteristics of the non-modified electrode. In SIA conditions an extended linear range of response and lower detection limit were achieved when compared with the electrode performance in FIA conditions. These aspects together with the additional advantage of low sample and reagent consumptions in SIA when compared to FIA, makes the incorporation of the proposed tubular ISE in a SIA system the preferred approach for on line determination and monitoring of fluoride content in natural water samples.     

Flow injection determination of anisidine value in palm oil samples using a triiodide potentiometric detector

A flow injection analysis (FIA) procedure for the determination of anisidine value (AV) in palm olein using a triiodide detector is described. Undiluted oil sample and chloramine-T reagent were added to a reaction chamber, and reaction was accelerated by applying a short vortex action (typically for 30 s). After allowing the emulsified oil phase to be separated from the aqueous phase (bottom layer), an aliquot of the aqueous phase (containing unreacted chloramine-T) was aspirated into a carrier stream that contained I⁻ where the chloramine-T oxidized the I⁻ to form I₃⁻ which was finally detected by a flow-through triiodide potentiometric detector. Variables that affect the FIA signals such as size of the reaction chamber, oil and reagent flow rates, chloramine-T concentration, vortex time, time for phase separation, carrier stream pH and injected volume were studied. The optimized FIA procedure is linear over 1.0-23.0 AV. The method exhibits good repeatabililty (R.S.D. of ±3.16% (n = 4) for the determination of 5.0 AV) and a sampling rate of 40 samples per hour was achieved. Good correlation (r² = 0.996 (n = 4)) between the proposed method and the manual American Oil Chemists’ Society procedure was found when applied to the determination of twenty different types of palm olein samples.     

Critical Comparison of Four Simple Adaptors for Flow Amperometric and Stripping Voltammetry with Mercury Drop Electrodes in Batch Cells

Electrochemical batch cells with mercury drop electrodes, MDEs, are readily available from a number of producers and widely used in electroanalysis for polarography, voltammetry and stripping voltammetry. To increase sample throughput and reduce reagent and sample consumption, the tendency is to couple the MDE with flow analysis systems (e.g., FIA, SIA or BIA). Many special flow cells for MDEs are described in the literature, but it is easier to convert existing commercial batch cells to flow operation. To assess the performance of such flow adaptors, four models were chosen because they are directly fitted to the glass capillary of any MDE, light enough not to impair the mechanical drop knocker and can be effortlessly built in the laboratory. They were all found adequate for flow amperometry and stripping voltammetry, with differences in sensitivity, flow rate dependence, response time, drop stability, tolerance to bubbles, uncompensated resistance and recontamination of disposed analyte from the electrolytic bath. Two of them, a simple L‐shaped PTFE tube and an upstream nozzle holder made from a disposable pipette tip, gather a larger set of desirable features.     

水样中氯离子的全自动连续流动注射测定

为将氯离子的流动注射分析法（ＦＩＡ）用于无人值守的全自动分析仪器中，使用了合并带技术来减少试剂的耗量，及使用区域取样技术来自动稀释样品，并使每一个样品在不同浓度区域自动测定一次，以避免高浓度样品的测定数据被遗漏。     

FIA-Fluorimetric assembly for the determination of noradrenaline hydrochloride by a solid-phase reactor with immobilized hexacyanoferrate(III)

An FIA assembly provided with immobilized hexacyanoferrate(III) is proposed for the fluorimetric determination of noradrenaline hydrochloride. The oxidative reagent is immobilized by means of a strong anion-exchange resin. The FIA manifold is very simple and the calibration graph is linear over the range 0.5–75mgl^–1 noradrenaline hydrochloride with an r.s.d of 0.88% (17 replicates) and a sample throughput of 84h^–1. Foreign compounds such as NaCl, sucrose, lactose and sodium sulfate caused no significant errors. The procedure is applied to the determination of noradrenaline in a medicinal formulation.     

Flow injection determination of peroxide value in edible oils using triiodide detector

A flow injection analysis (FIA) method for the determination of peroxide value (PV) in edible oils is described. Oil sample (undiluted) and KI reagent were aspirated into a homemade reaction chamber where the redox reaction between iodide in the aqueous phase and hydroperoxides in the oil was effected by applying a short (typically 30 s) vortex action. After allowing for the emulsified oil phase to be separated from the aqueous phase (bottom layer), an aliquot of the aqueous phase containing triiodide was next aspirated to the surface of a triiodide-selective membrane for detection. The optimized FIA procedure is linear over 0.35-28.0 PV (mequiv. O₂/kg) with a detection limit of 0.32 PV. Exhibiting good reproducibility (R.S.D. of 2.7% (n = 8) for the determination of 1.1 PV) and sampling rate of 80 samples h⁻¹, the proposed method, unlike previous FIA procedures, completely eliminated the use of organic solvents (except the use of 2-propanol for cleaning of reaction chamber). Excellent correlation (R² = 0.9949) between the proposed method and the manual official AOCS method was found when applied to the determination of PV in diverse type of edible oils (n = 20).     

海水中硝酸盐的无阀连续流动分析

建立了一种无阀连续流动分析方法和装置,仅用一台多通道蠕动泵传送试剂和样品,无需依靠注入阀、电磁阀和定量环进行试剂或样品的选择和定量输入.样品通过铜-镉还原柱,将硝酸盐还原为亚硝酸盐,然后用重氮-偶氮光度法进行测定.研究结果表明,硝酸盐的线性范围为5 ～ 180 μmol/L,方法检出限为0.27.μmol/L,对10和80 μmol/L硝酸盐溶液连续测定11次,相对标准偏差分别为1.4％和1.3％,不同盐度的实际水样加标回收率在99.4％ ～ 106.1％之间.测定结果与流动注射分析法相比,无显著性差异.与流动注射分析相比,无阀设计装置大大降低了成本,操作更加简便,有利于在普通实验室或现场连续监测中推广使用.本方法成功应用于厦门西港海水样品中硝酸盐的测定以及九龙江河口区的硝酸盐走航式监测.     

Flow injection analysis: A useful alternative for solving analytical problems

Summary In addition to its well-known advantages (e.g. ease of automation, high sample throughout and versatility, low sample and reagent consumption and analytical costs), flow injection analysis (FIA) offers the possibility of solving a number of specific analytical problems where poor sensitivity or selectivity, time-consuming preliminary steps, the use of HPLC in routine control for the analysis of a large number of samples, the determination of various analytes (multidetermination) or process monitoring in near-real time is involved.     

Multicomponent flow injection based analysis with diode array detection and partial least squares multivariate calibration evaluation. Rapid determination of Ca(II) and Mg(II) in waters and dialysis liquids

Flow injection analysis (FIA) with multiwavelength scanning of the FIA peaks using a diode array detector (DAD) has been combined with a multivariate calibration approach applying the partial least squares (PLS) method for the data evaluation. In this way, various side effects like dilution of the reagent, high blank, absorbance changes due to the pH gradient throughout the peak and/or the other interferences can be accounted for. Thus, even with a simple FIA manifold instrumentation the satisfactory results of multicomponent analysis are obtained. The method described has been checked on analysis of binary (Ca and Mg) and ternary (Ca, Mg and Cu) mixtures with pyridylazo resorcinol (PAR) as reagent and applied for rapid determination of calcium and magnesium in dialysis liquids and waters.     

On-line sample preparation and determination of phenols with a Flow-Analysis method

Summary A Flow-Analysis system has been developed to automate the phenol determination according to the German standard method DIN 38409-H16-2. The automation leads to a significant acceleration of the procedure. One analysis only lasts 3 min while the complete manual determination requires 3 h. Also the sample, solvent and reagent volumes are reduced to a tenth of the volumes demanded by the standard method. The described phenol determination is based on the integration of an airsegmented (Airsegmented-Flow-Analysis SFA) part in a Flow-Injection-Analysis (FIA) system. The main steps of the analytical procedure are: Reproducible inserting of the sample in a carrierstream, sample pretreatment and sample measuring. In the first step the sample is injected into the carrierstream. It transports the sample in the reactioncoil and than through the distillation unit. The steam distillation represents the sample preparation step; therefore an airsegmented stream is necessary. Afterwards the different phases (liquid and gas) were singled again and the distilled solution is fed into the FIA manifold. The determination itself takes place inside the FIA system. The limit of determination amounts to 0.01 mg l^–1 with a standard deviation of 1.5%. Different waste, surface and drinking water samples have been analyzed without any problems. The results correspond very well to those obtained by manual procedure.     

Flow injection determination of ethanol in whole blood using immobilized enzymes

Enzymatic methods for the determination of ethanol in whole blood are proposed. They use different types of detection and flow injection analysis (FIA) modes: fluorometric detection (use of normal FIA and stopped-flow/FIA); amperometric detection by monitoring of NADH (use of normal amperometric and pulse mode) and with the aid of a coupled enzymatic reaction (2,6-dichlorophenolindophenol/diaphorase). Determination ranges between 0.1 and 30.0 μg/ml are obtained (which in all cases comprise the legal range of ethanol in blood), with good precision and sampling frequency. The sensitivity of the methods can be manipulated by changing the injected sample volume or the pH.     

On-line collection/concentration of trace amounts of formaldehyde in air with chromatomembrane cell and its sensitive determination by flow injection technique coupled with spectrophotometric and fluorometric detection

A simple, rapid and highly sensitive method for the determination of trace amounts of formaldehyde in air by using flow injection analysis (FIA) system coupled with a three-hole chromatomembrane cell (CMC) was investigated by using a spectrophotometer and a fluorometer. The CMC was applied to on-line collection/concentration of trace amounts of formaldehyde in air into water as an absorbing solution; formaldehyde in the air was found to be quantitatively transferred into the absorbing solution in CMC. The solution, containing absorbed formaldehyde, was introduced into the carrier stream of the FIA system. The amount of formaldehyde in an absorbing solution was measured spectrophotometrically and fluorometrically after the reaction with a mixed reagent of acetylacetone and ammonium acetate at pH 5.6–5.8. The amount of formaldehyde in the absorbing solution, measured by the proposed system, could be converted to the concentration of formaldehyde in the air sample. A calibration graph prepared by a series of standard formaldehyde aqueous solutions was adopted. The formaldehyde in indoor air, determined as exampled by the proposed spectrophotometric FIA, was found to be 5.14 ± 0.08 ppbv for 20 ml of the air sample at the air flow rate of 6 ml min⁻¹, and the relative standard deviation (R.S.D.) was 1.56%. The limit of detections (LODs) of HCHO in an absorbing solution was 2 × 10⁻⁸ M (0.6 ppb) and 8 × 10⁻⁹ M (0.2 ppb), respectively, by the spectrophotometric and the fluorometric FIA, and the LODs of HCHO in air sample of 40 ml were 0.05 and 0.03 ppbv, respectively. The interferences from foreign species were examined; tolerable concentrations of other aldehydes were more than 50-fold of formaldehyde (1 × 10⁻⁶ M).     

A microfluidic flow injection system for DNA assay with fluids driven by an on-chip integrated pump based on capillary and evaporation effects

A miniaturized flow injection analysis (FIA) system integrating a micropump on a microfluidic chip based on capillary and evaporation effects was developed. The pump was made by fixing a filter paper plug with a vent tube at the channel end, it requires no peripheral equipment and provides steady flow in the mul min(-1) range for FIA operation. Valve-free sample injection was achieved at nanolitre level using an array of slotted vials. The practical applicability of the system was demonstrated by DNA assay with laser-induced fluorescence (LIF) detection. A precision of 1.6% RSD (10.0 ng mul(-1), n = 15) was achieved with a sampling throughput of 76 h(-1) and sample consumption of 95 nl.