Flow injection analysis. principles,applications and trends

The basic principles of Flow Injection Analysis are outlined. The parameters governing the dispersion of the injected sample zone in the system are discussed, and it is demonstrated how these parameters can be manipulated in order to suit the requirements of an individual analytical procedure. A number of examples illustrating the practical application of f.i.a. are described, comprising the use of automated, stopped-flow, merging-zones, extraction techniques as well as f.i.a. scanning and methods based on intermittent pumping. Updated lists on f.i.a. procedures published and species that can be determined by f.i.a. are included.     

Film formation from pure and mixed latices; transient fluorescence study

A fast transient fluorescence technique was used to study latex film formation induced by organic solvent vapor. Mixtures of pyrene (P)- and naphthalene (N)-labeled and/or pure naphthalene-labeled latex films were prepared separately from poly(methyl methacrylate) (PMMA) particles. Then these pure and mixed latex films were exposed to vapor of various chloroform-heptane mixtures in seven different experiments. In both films, fluorescence lifetimes from N were monitored during vapor-induced film formation. It was observed that N lifetimes decreased as the vapor exposure time is increased. A Stern-Volmer kinetic analysis was used for low quenching efficiencies to interpret the decrease in N lifetimes. A Prager-Tirrell model was employed to obtain back-and-forth frequencies, nu, of reptating PMMA chains during latex film formation induced by solvent vapor. In both pure and mixed latex films, nu values were found to be correlated with the chloroform content in the vapor mixture. It was observed that polymer interdiffusion obeyed a t1/2 law during film formation.     

Comparison of the Temperature Effect on the π∗←n and π∗←π Electronic Transition Bands of NO<Subscript>3</Subscript><Superscript>−</Superscript>(aq)

The effect of temperature on the π∗←π transition band in the UV absorption spectrum of NO₃⁻(aq) centered at ≈200 nm was studied in the temperature range 10–70 ^∘C. The observed temperature independence of this band was in contrast to the significant influence of temperature on the nitrate π∗←n transition reported recently by us. However, taking into account the electronic states involved in both the transitions, it was concluded that this finding was in accordance with our previous assumption that interconversion between spectrally distinct (with respect to π∗←n band) nitrate species included the rupture/formation of hydrogen bond(s) in the hydration shell of the nitrate ion.     

Conductivity Studies of Dilute Aqueous Solutions of Oxalic Acid and Neutral Oxalates of Sodium, Potassium, Cesium, and Ammonium from 5 to 35°C

Conductivity measurements of oxalic acid and neutral oxalates (disodium oxalate, dipotassium oxalate, dicesium, and diammonium oxalate) were performed on dilute aqueous solutions, c < 3 × 10^–3 mol-dm^–3, from 5 to 35°C. These data and those available from the literature were analyzed in terms of dissociation steps of oxalic acid, the Onsager conductivity equation for neutral oxalates, the Quint–Viallard conductivity equation for the acid, and the Debye–Hückel equation for activity coefficients, to give the limiting equivalent conductances of bioxalate anion ;(HC₂O₄ ^–) and oxalate anion (1/2C₂O₄ ^2–) and the corresponding dissociation constants K ₁ and K ₂.     

Pulse plating effect on microstructure and corrosion properties of Zn–Ni alloy coatings

The influence of pulse plating parameters on the surface morphology, grain size, lattice imperfection and corrosion properties of Zn–Ni alloy has been studied. The coatings were electrodeposited in an alkaline cyanide-free solution. AFM was applied for surface morphology examination, XRD measurements were carried out for phase composition and texture analysis, electron probe microanalysis was used for alloy chemical composition studies, while electrochemical techniques were applied for corrosion performance evaluation. The pulse plated Zn–Ni coatings appeared to consist of the γ-Zn₂₁Ni₅ phase and the composition of the alloy depended on the plating parameters. The grain size, lattice imperfection and homogeneity of grain distribution were established to be the main factors determining corrosion behaviour of the coating. Presented at the 4th Baltic Conference on Electrochemistry, Greifswald, March 13–16, 2005     

Some new ring-D seco steroids

The Beckmann fragmentation product, 3-methoxy-17-oxo-16,17-secoestra-1,3,5(10)-trien-16-nitrile (2) has been reduced by LAH giving the expected 3-methoxy-17-hydroxy-16,17-secoestra-1,3,5(10-trien-16-amine hydrochloride (3) and 3-methoxy-17-oxa-D-homoestra-1,3,5(10)-trien-16-ol (4), by a presumed neighbouring group participation of 17-OH group in the intermediary formed 16-imino derivative (A). The structure of 4 has been proved by an alternative synthetic route by reducing 3-methoxy-17-oxa-D-homoestra-1,3,5(10)-trien-16-one (7) with di-iso-butylaluminium hydride.     

The first decade of flow injection analysis: from serial assay to diagnostic tool

Some 804 papers on flow injection analysis published to the end of May 1985 are summarized. Past trends are discussed and new developments are briefly outlined.The paper entitled “Flow Injection Analysis. Part 1. A New Concept of Fast Continuous Flow Analysis” [1], which appeared in August 1975, was the first of some 804 papers [1/2-804] published on flow injection analysis (f.i.a.) during the past ten years. In the present contribution, all these papers are collected to record the status quo of the general method and to reveal the present trends in applications of f.i.a. and in the geographical distribution of the research activities. Important concepts and technological innovations are reviewed and the future development of f.i.a. is briefly outlined.     

Study of the Retention Behavior of Newly Synthesized s-Triazine Derivatives in RP TLC Systems,and the Lipophilicity of the Compounds

JPC – Journal of Planar Chromatography – Modern TLC - The chromatographic behavior of nine newly synthesized s-tri-azines has been studied by thin-layer chromatography on C18/UV254...     

Development and prevalidation of a method for phenol determination by solid-phase spectrophotometry

A simple, sensitive and rapid solid-phase spectrophotometric procedure was developed for the determination of traces of phenol with 4-aminoantipyrine as a reagent (AAP-SPS), and the optimal experimental conditions were established. This method was performed by sorption and direct absorbance measurements of the product phenol-AAP sorbed on the anion-exchanger Dowex 1-X4 (0.2 g) at 495 nm (absorption maximum) and 700 nm (non-absorption wavelength). The sensitivity offered by the AAP-SPS procedure was higher by a factor of 40 compared with the respective conventional spectrophotometric method. Metrological characteristics were established using a prevalidation strategy. The AAP-SPS procedure is characterized by a linear calibration function in the working range of 0.05–0.50 μmol, low standard deviation of procedure (±0.012), low limit of determination (0.021 μmol), and favorable random (±0.85 to ±11.27%) and systematic deviations (−4.55 to +11.50%). Moreover, the accuracy of the system investigated by the recovery test is acceptable (99–102%). Favorable working and performance characteristics make the new SPS method ideal for phenol monitoring in pharmaceutical preparations as well as other matrices.     

Isotachophoretic analysis of the dihydrofolate reductase reaction in the presence of methotrexate and ascorbic acid

The antifolate methotrexate (MTX) is widely used in cancer chemotherapy. In this study, we show that MTX (MTX-Glu1) and MTX-polyglutamates (MTX-Glu2-5) strongly inhibited the growth of the leukemic cell line MOLT-4. This effect, however, was mitigated by ascorbic acid. We investigated whether ascorbic acid is able to reduce dihydrofolic acid (DHF) to tetrahydrofolic acid (THF) directly or by circumventing the MTX inhibition of dihydrofolate reductase (DHFR). The inhibition of this NADPH-dependent reduction of DHF by MTX-Glun in the absence or presence of ascorbate, was determined by analytical isotachophoresis. Using 0.01 M HCl/histidine, pH 6.0, as a leading electrolyte (L) and 0.005 M 2-(N-morpholino)ethanesulfonic acid (MES)/histidine, pH 6.0, as a terminating electrolyte (T), MTX-Glun derivatives including MTX-Glu1 could be easily separated, whereas the quantitative estimation of THF was not possible. A quantitative characterization of the DHFR reaction by measuring NADPH, NADP+ and ascorbate was achieved with another system (L: 0.01 M HCI/beta-alanine, pH 3.73; T: 0.01 M caproic acid, pH 3.27). Nanomolar concentrations of MTX-Glu1-5 inhibited consumption of NADPH and production of NADP+. Ascorbic acid was not able to reduce DHF, neither directly nor after inhibition of DHFR by MTX. However, ascorbic acid seemed to diminish the oxidation of THF and this may account for its capacity to reduce the inhibitory effect of MTX on MOLT-4 cells.