Modified FIAS-400 flow injection analysis

Vinas et al. [47] determined penicillamine routinely by using batch procedures and FIA. A capsule was dissolved in water, diluted to 250 mL, and a suitable portion of the solution treated with 1 mM Co(II) solution (2.5 mL) and 2 M ammonium acetate (2.5 mL). The mixture was diluted to 25 mL and the absorbance of the yellow complex was determined at 360 nm. Calibration graphs were linear for 0.02-0.3 mM of penicillamine. The method was modified for flow injection analysis using peak-height or peak-width methods, but in both cases the flow rates were maintained at 3.3 mL/min. For the peak-height technique, calibration graphs were linear for 0.1-2 mM, and the sampling frequency was 150 samples per hour. For the peak-width method, the response was linear for 50 pM to 0.1 M, and this method was particularly useful for routine determinations. 

All potentials vs. screen-printed pseudo Ag/AgCl reference, except values marked with double-dagger (J), which are vs. screen-printed Ag/Pd, and 02 those marked with asterisk ( ), which are vs. Ag/3M AgCl double-junction reference electrode. Abbreviations LDH lactate dehydrogenase, LOD lactate oxidase, PVA-SbQ styrlpyridinium-modified poly(vinyl alcohol), FIA flow injection analysis. aLinear ranges using a dialysis system. 

Flow injection analysis (FIA) ESI-MS and APCI-MS spectra for an EO/PO polyether modified silicone surfactant (PEMS) used as a personal care product have been obtained in positive and negative ionisation modes with the positive ionisation mode yielding the best results [41]. The spectra obtained in both modes were highly complicated, and thus no assignment was given. Significant differences in the ionisation results were obtained from the two interfaces, with those ions observed in the ESI-MS spectrum appearing in the lower... 

The need for an automated and reliable system for formaldehyde determination is now clearly recognized. In response to this need, an automated and microprocessor-controlled flow injection analysis (FIA) system was developed in our laboratory. This system is based on the use of the modified pararosaniline colorimetric method (j6). The simplicity, versatility, good precision, high sampling rate, complete automation and relatively low cost of the system make it attractive for the analysis of large numbers of formaldehyde samples. In this chapter, sufficient background in the principle of FIA will be presented to allow the readers to evaluate the technique and its potential application to the routine analysis of formaldehyde will be explored. 

Fig. 39. Flow injection analysis (FIA) system for the determination of glucose involving a GDH reactor and a chemically modified electrode for NADH measurement. (Redrawn from Appelqvist et al 1985).

Thus, for glucose measurement excellent parameters such as a coefficient of variation (relative standard deviation, CV) of 0.2-0.6%, have been achieved by using a flow injection analysis (FIA) device combined with a GDH reactor and an electrode modified for NADH indication (Fig. 39) (Appelqvist et al., 1985). 

ADP AFP ab as ALAT AP ASAT ATP BQ BSA CEH CK CME COD con A CV d D E E EC ECME EDTA EIA /e FAD FET FIA G GOD G6P-DH HBg HCG adenosine diphosphate a-fetoprotein antibody antigen alanine aminotranferase alkaline phosphatase aspartate aminotransferase adenosine triphosphate benzoquinone bovine serum albumin cholesterol ester hydrolase creatine kinase chemically modified electrode cholesterol oxidase concanavalin A coefficient of variation (relative standard deviation) layer thickness diffusion coefficient enzyme potential Enzyme Classification enzyme-chemically modified electrode ethylene diamine tetraacetic acid enzyme immunoassay enzyme loading factor flavin adenine dinucleotide field effect transistor flow injection analysis amplification factor glucose oxidase glucose-6-phosphate dehydrogenase hepatitis B surface antigen human chorionic gonadotropin... 

Analysis in flowing solutions, as performed in particular with high performance liquid chromatography (HPLC) and flow injection analysis, (FIA) has developed rapidly over the last decade and now plays an important function in most analytical laboratories throughout the world. There is little doubt, however, that even HPLC lacks the resolving power required to solve analytical problems in complex matrices with minimal sample preparation. Often, the resolving power of the detection method is called upon to assist in the solution of these problems. This is particularly true with electrochemical detection (ED) systems which offer a certain degree of selectivity based on differences in oxidation or reduction potentials of the species to be determined. In recent years, the advent of chemically modified electrodes (CMEs) has provided a stimulus to further improve both the sensitivity and selectivity of ED systems used in HPLC and FIA. 

Gas-diffusion membranes Hydrophobic porous polymer membranes with air filling the membrane pores have been used successfully in the online separation of volatile and semivolatile analytes between two miscible liquid streams in flow injection analysis (FIA) systems. The corresponding technique is frequently referred to as gas-diffusion EIA. The mass transfer of an analyte across a gas-diffusion membrane is controlled by the membrane pore size and the solubility of the analyte in the feed and receiver solutions. The latter can be manipulated by appropriately modifying the chemical composition of the two solutions. In this way it is possible to enhance both the evaporation of the analyte from the feed solution into the membrane pores and its subsequent absorption into the receiver solution. 

The second part describes the application of this automated potentiostat as an electrochemical detector for various electro-inactive anionic species nitrate (NOg ), nitrite (NOg"), sulfate (SO "), chloride (CD, etc. (1,2). The electrochemical detection involves the use of a conducting poly(3-methylthiophene) (P3MT) polymer modified platinum electrode in a flow injection analysis (FIA) mode. 

Flow Injection Analysis (FIA) with Poly(3-methylthiophene) Modified Electrodes... 

In 1998, Mizutani et al. developed a flow injection analysis (FIA) system with a GIOD enzyme/polyion complex bilayer membrane-based electrode as a detector to determine L-glutamic acid [16]. The authors remark that the bilayer membrane is better than the others, because the analyte permeates freely to the layer and undergoes the enzymatic reaction, whereas the permeation of the interferents is strongly restricted. To form the bilayer membrane for L-glutamic acid determination, the authors used a gold electrode with a suitable treatment to modify it. The most important steps are ... 

Porphyrin-modified electrodes were widely utilized for quantification of low concentrations of metals, pharmaceutical products, and species of environmental and industrial importance in association with flow techniques. This strategy enhances the amperometric response and sensitivity (the capacitive current is virtually reset), while reducing significantly the time necessary for analyses. Flow injection analysis (FIA) has been extensively explored for this purpose and a revision on the application of porphyrins and derivatives was published some years ago [203]. Alternatively, batch injection analysis (BIA) can be an interesting way for fast analyses utilizing a similar mass transport process to the electrode surface [204]. For example, citric acid was electrochemically determined by BIA using cobalt phthalocyanine modified carbon paste electrodes [205]. 

One of the first reported uses of a conducting polymer moditied electrode for the detection of anions by flow ipjection analysis (FIA) utilized poly(pyrrole) 13). Low detection limits were achieved. However, poly(pyrrole) is irreversibly oxidized in the presence of oxygen at potentials of around +1.0 volts. Poly(3-methylthiophene) does not exhibit this behavior. Therefore, poly(3-methylthiophene appeared to be a good candidate as an electrochemical detector for anionic species by FIA with electrochemical detection at an poly(3-methylthiophene) modified electrode. Also P3MT does not need to be undoped (cyded between the negative and positive detection potentials) between successive injections as many other polymer systems must. 

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