Flow injection system using

Aschematic diagram of the flow injection system used by Anderson [126] is shown in Fig. 2.4. An Ismatec model MP13 peristaltic pump was used. Different flow rates were obtained by changing the pump tube diameter, as indicated in the legend to Fig. 2.4. The injection port was a rotary valve [131,170]. The sample volume could be varied between 10 and 1000 pi simply by changing the length of the sample loop. 

Lariviere, D., Cumming, T. A., Kiser, S., Li, C., and Cornett, R. J., Automated flow injection system using extraction chromatography for the determination of plutonium in urine by inductively couple plasma mass spectrometry, J. Anal. At. Spectrom., 23, 354-360, 2008. 

GFAAS and FAAS are the techniques (Methods 202.1 and 202.2) recommended by EPA for measuring low levels of aluminum in water and waste water (Kopp and McKee 1978). Detection limits of 100 g of aluminum/L of sample and 3 g of aluminum/L of sample were obtained using the FAAS and GFAAS techniques, respectively (Kopp and McKee 1978). Spectrophotometry and GC/ECD have also been employed to measure low-ppb ( g/L) levels of aluminum in water (Dean 1989 Ermolenko and Dedkov 1988 Gosink 1975). Flow-injection systems using absorbance (Benson et al. 1990) and fluorescence detection (Carrillo et al. 1992) have been used to monitor aqueous aluminum levels in the field and in the laboratory setting, with detection limits as low as 0.3 g/L. 

Determination of starch in a flow injection system using immobilized enzymes and a modifled electrode Anal. Chim. Acta 180 3-8... 

B. Olsson, A Flow-Injection System Using Immobilized Peroxidase and Chromogenic Reagents for Possible Determination of Hydrogen Peroxide. Mikrochim. Acta, II (1985) 211. 

J. Emn6us, R. Appelqvist, G. Marko-Varga, L. Gorton, and G. Johansson, Determination of Starch in a Flow Injection System Using Immobilized Enzymes and a Modified Electrode. Anal. Chim. Acta, 180 (1986) 3. 

Figure 21-2. Arrangement of the flow injection system used for the determination of phosphorous pesticides and carbamates [26].

The flow injection system used was a Control Equipment Corp. model MCA-103. The potentiostat used in conjunction with the flow injection work was either a PARC model 174 or an IBM 225. HPLC was performed on Waters Chromatography equipment consisting of model 510 pumps, model 680 gradient controller, model 460 electrocheptiical detector and U6K injector. 

Figure 5 Flow injection systems used to determine benzophe-none-3 (2-hydroxy-4-methoxybenzophenone or oxybenzone) in sunscreen creams (A) flow injection analysis (FIA) (B) sequential injection analysis (SIA). Reagents (1), (2), (12), (14) peristaltic pump (3) merging point (4) injection valve (5) reaction coil (6) flow cell (7) ethanol (8) autoburette with syringe (9) holding coil (10) eight-channel selector valve (11) sample or standard solutions (13). (Reproduced from Chisvert A, Salvador A, Pascual-Martf MC, and March JG (2001) Fresenius Journal of Analytical Chemistry 369 684-689.)...

Schematic representation of solid-phase extraction performed in flow injection systems using a SPE column fitted in the injection loop of a six-port injection valve. In the loading position, sample is loaded into the SPE column, where riboflavin is retained. By switching to the injection position, eluent is sent through the SPE column, originating analyte desorption which is then collected in a vial placed on one of the ports. SPEC solid-phase extraction column.

Another procedure for the determination of TOC and its fractions in industrial effluent samples has been recently introduced [129]. A flow injection system using a gas-liquid transfer microreactor is developed, and adapted to a turbidimetric spectrophotometer. Samples are decomposed into glass vials in a microwave oven and a fraction of the CO2 is injected into a carrier gas and pumped to a glass microreactor. With minor modifications, the system allows the determination of different carbon fractions. The advantages of the proposed procedure are simplicity, low volume of samples and reagents, high frequency of determinations, and low cost. The dynamic range is 20-800 mg C/L, and the calculated LOD is 17 mg C/L. 

FAAS A flow injection system using dual... 

Trojanowicz, M., J. Szpunar-Lobriska, and Z. Michalski. 1991. Multicomponent analysis with a computerized flow injection system using FED photometric detection. Mikrochim. Acta 1 159-169. 

FIGURE 9.2 (a) Flow injection system used for the generation of a double-pH gradient BRH, acid Britton-Robinson solution IV, injection valve R, reactor DAD, diode array detector W, waste q, 0.56 mL/min PP, peristaltic pump, (b) Scheme of the pH gradient profile. 

FIGURE 11.2 Schematic diagram of the flow injection system used for the determination of gaseous species. GD gas diffusion D detector the carrier stream was deionized water and the flow rate for acetic acid determination was 1.0 mL/min. (Adapted from Araujo, C. S. T. et al. 2005. Food Chem. 92 765-770.)... 

Enzyme immunosensors are used in flow injection systems and Hquid chromatography to provide automated on-line analyses (71—73). These systems are capable of continuously executing the steps involved in the immunoassays, including the binding reactions, washing, and the enzyme reaction, in about 10 minutes. 

A flow-injection system with electrochemical hydride generation and atomic absorption detection for the determination of arsenic is described. This technique has been developed in order to avoid the use sodium tetrahydroborate, which is capable of introducing contamination. The sodium tetrahydroborate (NaBH ) - acid reduction technique has been widely used for hydride generation (HG) in atomic spectrometric analyses. However, this technique has certain disadvantages. The NaBH is capable of introducing contamination, is expensive and the aqueous solution is unstable and has to be prepared freshly each working day. In addition, the process is sensitive to interferences from coexisting ions. 

C.A. Scolari and S.D. Brown, Multicomponent determination in flow-injection systems with square-wave voltammetric detection using the Kalman filter. Anal. Chim. Acta, 178 (1985) 239-246. 

Membrane separation coupled on-line to a flow-injection system was employed for the monitoring of propazine and terbutryn in natural water. A microporous hydro-phobic membrane was utilized in which the analytes were extracted from the aqueous medium into an organic solvent that was carried to the flow cell of a photodiode-array spectrophotometer. The LCDs were 4-5 qg so the technique could potentially be used for screening purposes. Samples with positive detection would require further analysis. 

Couto et al. [11] developed a flow injection system with potentiometric detection for determination of TC, OTC, and CTC in pharmaceutical products. A homogeneous crystalline CuS/Ag2S double membrane tubular electrode was used to monitor the Cu(II) decrease due to its complexation with OTC. The system allows OTC determination within a 49.1 1.9 x 103 ppm and a precision better than 0.4%. A flow injection method for the assay of OTC, TC, and CTC in pharmaceutical formulations was also developed by Wangfuengkanagul et al. [12] using electrochemical detection at anodized boron-doped diamond thin-film electrode. The detection limit was found to be 10 nM (signal-to-noise ratio = 3). 

S. Sawada, H. Torii, T. Osakai, and T. Kimoto, Pulse amperometric detection of lithium in artificial serum using a flow injection system with a liquid/liquid-type ion-selective electrode. Anal. Chem. 70, 4286-4290 (1998). 

Olsen et al. [660] used a simple flow injection system, the FIAstar unit, to inject samples of seawater into a flame atomic absorption instrument, allowing the determination of cadmium, lead, copper, and zinc at the parts per million level at a rate of 180-250 samples per hour. Further, online flow injection analysis preconcentration methods were developed using a microcolumn of Chelex 100 resin, allowing the determination of lead at concentrations as low as 10 pg/1, and of cadmium and zinc at 1 pg/1. The sampling rate was between 30 and 60 samples per hour, and the readout was available within 60-100 seconds after sample injection. The sampling frequency depended on the preconcentration required. 

Fang et al. [661] have described a flow injection system with online ion exchange preconcentration on dual columns for the determination of trace amounts of heavy metal at pg/1 and sub-pg/1 levels by flame atomic absorption spectrometry (Fig. 5.17). The degree of preconcentration ranges from a factor of 50 to 105 for different elements, at a sampling frequency of 60 samples per hour. The detection limits for copper, zinc, lead, and cadmium are 0.07, 0.03, 0.5, and 0.05 pg/1, respectively. Relative standard deviations are 1.2-3.2% at pg/1 levels. The behaviour of the various chelating exchangers used was studied with respect to their preconcentration characteristics, with special emphasis on interferences encountered in the analysis of seawater. 

Several authors observed CL emission based on reduction reactions. Lu et al. [59] developed a method by applying a Jones reductor for producing unstable reductants. A column (100 X 3 mm i.d.) filled with Zn-Hg particles was inserted into the flow stream of a flow injection system. CL was measured using a homemade CL analyzer. Although the Jones reductor was more effective for the species studied in 0.5-5 mol/L H2S04 solution, the authors found that a lower acid concentration improved the CL emission. Hie optimal pH was 6.5 for V(II), 2.5 for Mo(III), 3.5 for U(III), 3.0 for W(III), 3.0 for Cr(II), 2.5 for Ti(III), and 2.5 for Fe(II). The methods allowed determination of the above-mentioned species at pg/mL to ng/mL levels. It was assumed that the CL reactions were related to the production of superoxide radicals by dissolved oxygen in the solutions. The proposed methods could be successfully applied to the determination of V [60], Mo [61], and U [62] in water or steel samples. 

Finally, Yamada and Suzuki made a comparative study of the use of DDAB, HTAB, STAC, and CEDAB to improve the sensitivity and selectivity of the determination of ultratraces of Cu(II) by means of the CL reaction of 1,10-phenanthroline with hydrogen peroxide and sodium hydroxide, used as detection in a flow injection system [46]. Of the four cited surfactants it was found that CEDAB causes the greatest enhancement of the chemiluminescent signal (Fig. 12) (an enhancement factor of 140 with respect to the absence of surfactant). 

The instrumentation used for FIA with CL detection is usually simple and is composed of the components depicted in Figure 2. These components are readily assembled to form the analytical manifold, although there are also commercially available flow injection systems with CL detection. Spectrophotometric or fluo-rimetric flow injection systems can often be used for CL measurements after some modifications. 

A sensor array where different haptens are immobilized at well-defined areas on a plain glass surface has been developed [66], Using an automated flow injection system it was possible to incubate all areas on the chip with analytes, specific antibodies, secondary HRP-labeled antibodies, and CL substrate. Measurement of the light output via imaging performed with a CCD device allowed determination of the analytes present in the sample on the basis of the spatial localization of the CL signal. 

In some cases, so called direct plasma injection techniques may be used23 83 104 108 instead of protein precipitation for loading plasma samples onto an HPLC/MS/MS system. Some direct plasma injection systems use a column switching technique in which the plasma is loaded onto an extraction column that retains the small molecules. The other plasma components are sent to waste and the flow is switched so that the small molecules are eluted onto an analytical column that connects to the MS/MS.23 83 108 One variation of the column switching method is turbulent flow chromatography commercialized by Cohesive Technologies (now part of Thermo, San Jose, CA).23... 

Chovan et al.30 described a system that integrates different components of bioanalysis including automatic in vitro incubation, automatic method development (mainly SRM transitions for LC/MS/ MS analysis), and a generic LC method for sample analysis to minimize human intervention and streamline information flow. Automaton software (Applied Biosystems) was used for automatic MS method development. Flow injection was used instead of a HPLC column to decrease run time to 0.8 min per injection. Two injections were performed. The first was performed to locate the precursor ion and optimal declustering potential (DP). The second injection was performed to locate the product ion and optimal collision energy (CE). 

In the method for extractable phosphorus [62, 64-66] the phosphorus is extracted from the soil at 20 1°C with sodium bicarbonate solution at pH8.5. After filtration and release of carbon dioxide the extracts are introduced into a flow-injection system for the determination of phosphate. Phosphate is determined by reaction with vanadomolybdate and the yellow colour evaluated at 410nm. Between 20 and lOOOmg kg-1 phosphorus in soil has been determined using this method. 

L. Arce, A. Rios and M. Valcarcel, Determination of anti-carcinogenic polyphenols present in green tea using capillary electrophoresis coupled to a flow injection system. J. Chromatogr.A 823 (1998) 113-120. 

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