Relevant insights and concepts overlooked throughout the development of flow analysis. A tutorial.

The conceptual expansion, fast development, and general acceptance of flow analysis are consequence of its adherence to the principles of green and white analytical chemistry, and chemical derivatization plays an essential role in this context. Through the flow analysis development, however, some of its potentialities and limitations have been overlooked. This is more evident when the involved modifications in flow rates, timing and/or manifold architecture deteriorate the analytical signals.

Flow-based determination of lead exploiting in-syringe dispersive liquid-liquid micro-extraction in xylene and integrated spectrophotometric detection.

A lab-in-syringe flow system exploiting dispersive liquid-liquid micro-extraction in a solvent lighter than water is proposed for the spectrophotometric determination of lead in industrial residual waters. The steps inherent to both liquid-liquid extraction and monitoring of the formed compound are in-syringe carried out. The classical carbon tetrachloride is not used as the extracting solvent, as it does not present the friendly characteristics inherent to the Green Analytical Chemistry.

Chemical Derivatization in Flow Analysis.

Chemical derivatization for improving selectivity and/or sensitivity is a common practice in analytical chemistry. It is particularly attractive in flow analysis in view of its highly reproducible reagent addition(s) and controlled timing. Then, measurements without attaining the steady state, kinetic discrimination, exploitation of unstable reagents and/or products, as well as strategies compliant with Green Analytical Chemistry, have been efficiently exploited.

Large-scale flow analysis: From repetitive assays to expert analyzers.

Flow analysis is usually associated with repetitive assays, as all samples of a batch are generally handled in the same way. By exploiting computer-controlled devices (e.g.

An automatic titration setup for the chemiluminometric determination of the copper complexation capacity in opaque solutions.

An automatic titration setup exploiting flow analysis was proposed for the evaluation of the copper complexation capacity of highly opaque substances (milk and humic substances). The binary search approach was implemented in a flow-batch analyzer, in order to add the in-line selected titrant (e.g.

The multiple facets of flow analysis. A tutorial.

The amazing development of flow analysis has led to a loss of conceptual uniformity and to the proposals of a number of modalities, each assigned to an acronym, and this aspect may hinder further developments in the field. As any sample handling step of a flow-based analytical procedure can be accomplished in different ways, there are multiple facets associated to it. This tutorial is focused on the critical evaluation of these facets and the proposal of a novel way to present the flow analyzers, disregarding or even avoiding the need for specifying flow modalities and acronyms.

Flow analysis during the 60 years of Talanta.

A parallel within the development of flow analysis and the consolidation of Talanta as one of the main journals in analytical chemistry is drawn. Influence of scientific divulgation, meeting organizations, thematic issues devoted to scientific events and Talanta awards in the recent development of flow analysis is emphasized. For didactic purposes, the discussion is focused on three 20-year periods.

Solid-phase extractions in flow analysis.

Coupling solid-phase extraction (SPE) to flow systems has promoted a synergistic development. Whereas SPE mechanization leads to improved precision and higher sample throughput, as well as diminishes systematic errors and contamination risks, analyte concentration and separation from the sample matrix provides a remarkable impact on detectability and selectivity in flow analysis. Historical aspects, main cornerstones, tips for system design, and recent applications are critically reviewed, in the context of analyte(s) separation/concentration, sample clean-up, and release of sorbed chemical species involving both packed (e.

Fluidized particles in flow analysis: potentialities, limitations and applications.

In flow analysis, solid particles (sorbents, reagents or catalysts) have been used for e.g. analyte separation/concentration, sample clean-up, speciation analysis, enzymatic assays, analysis relying on slight soluble reagents, and kinetics studies related to adsorption/release of species.

Exploiting multivariate calibration for compensation of iron interference in the spectrophotometric flow-based catalytic determination of molybdenum.

Multivariate calibration involving partial least squares was exploited in the flow-based spectrophotometric determination of molybdenum in river waters relying on the Mo(VI)-catalyzed iodide oxidation by HO under acidic conditions. Two sample aliquots were simultaneously inserted into the carrier stream, and differential pumping was accountable for in-line addition of sulfuric acid to one of them. Pronounced gradients (acidity and reagent concentrations) were established along the complex sample zone formed, and the absorbance-time function was characterized by local maximum and minimum values.

Dual thermostating in flow analysis.

An advanced strategy involving concentric tubes is proposed for fast and controlled heating (or cooling) of the reaction medium in flow analysis. Different temperatures are set by sequentially circulating two thermostated water streams through the outer larged bore (2.0mm i.

Sulphate radical generation through interaction of peroxymonosulphate with Co(II) for in-line sample preparation aiming at spectrophotometric flow-based determination of phosphate and phosphite in fertilizers.

An advanced oxidative process relying on the interaction of peroxymonosulphate and cobalt(II) was implemented for generating the sulphate radicals in flow analysis, in order to accomplish in-line sample preparation thus improving the spectrophotometric determination of phosphate and phosphite in liquid foliar fertilizers. To this end, a flow-batch system with a heated chamber was designed. The sample was handled twice, with and without the step of phosphite oxidation to phosphate, and the formed orthophosphate was quantified after interaction with the vanadate-molybdate reagent.

A novel flow-based procedure for automation of respirometric assays in soils.

A flow-based strategy involving a gas-diffusion sampling probe was proposed for evaluating the respiration rate in soils. The amount of CO2 collected after a pre-defined time interval was proportional to the free CO2 released by the soil ecosystem. The 500-mL incubation flasks typically used for soil respirometric assays were adapted and a special cover was designed for connecting a tubular gas diffusion membrane, a fan, and a septum for adding the CO2(g) standards required for calibration.

Rapid estimation of readily leachable triazine residues in soils using automatic kinetic bioaccessibility assays followed by on-line sorptive clean-up as a front-end to liquid chromatography.

An automatic batchwise bioaccessibility test was proposed for on-line monitoring of readily mobile pools of ametryn and atrazine residues in agricultural soils with different physicochemical properties. A 0.01molL(-1) CaCl2 solution mimicking rainwater percolation through the soil profiles was used for the herbicide extractions.

Tracer-monitored flow titrations.

The feasibility of implementing tracer-monitored titrations in a flow system is demonstrated. A dye tracer is used to estimate the instant sample and titrant volumetric fractions without the need for volume, mass or peak width measurements. The approach was applied to spectrophotometric flow titrations involving variations of sample and titrant flow-rates (i.

A critical comparison of constant and pulsed flow systems exploiting gas diffusion.

Considering the beneficial aspects arising from the implementation of pulsed flows in flow analysis, and the relevance of in-line gas diffusion as an analyte separation/concentration step, influence of flow pattern in flow systems with in-line gas diffusion was critically investigated. To this end, constant or pulsed flows delivered by syringe or solenoid pumps were exploited. For each flow pattern, two variants involving different interaction times of the donor with the acceptor streams were studied.

Pulsed flows in flow analysis: Potentialities, limitations and applications.

In flow analysis, use of a steady and pulseless flow was considered essential for ensuring a reproducible handling of the flowing sample. To this end, peristaltic and syringe pumps have been the propelling device in the vast majority of the flow analysers. Recently, the number of applications involving pulsed flow has been increasing.

Exploiting zone trapping to avoid liberation of air bubbles in flow-based analytical procedures requiring heating.

In flow-based analytical procedures requiring heating, liberation of air bubbles is avoided by trapping a sample selected portion into a heated hermetic environment. The flow-through cuvette is maintained into a temperature-controlled aluminium block, thus acting as the trapping element and allowing real-time monitoring. The feasibility of the innovation was demonstrated in the spectrophotometric catalytic determination of vanadium in mineral waters.

Flow analysis in Brazil: contributions over the last four decades.

The main contributions of Brazilian researchers to the field of flow analysis are reviewed, with an emphasis on historical developments, conceptual aspects, system design, and analytical applications. Contributions after the advent of flow injection analysis are highlighted. Novel approaches (e.

A multi-purpose flow manifold for the spectrophotometric determination of sulphide, sulphite and ethanol involving gas diffusion: application to wine and molasses analysis.

A simple and rugged flow set up was designed for spectrophotometric determination of sulphide, sulphite and ethanol aiming at quality assessment of wines, control of industrial fermentation, and selection of yeast strain. The different assays involved gas diffusion through a Teflon planar membrane and were carried out after minor modifications in the manifold, namely reagent composition and total flow rate. Main figures of merit: linear analytical curves=0.

Banana peel as an adsorbent for removing atrazine and ametryne from waters.

The feasibility of using banana peel for removal of the pesticides atrazine and ametryne from river and treated waters has been demonstrated, allowing the design of an efficient, fast, and low-cost strategy for remediation of polluted waters. The conditions for removal of these pesticides in a laboratory scale were optimized as sample volume = 50 mL, banana mass = 3.0 g, stirring time = 40 min, and no pH adjustment necessary.

A flow system with zone merging and zone trapping in the main reactor applied to spectrophotometric catalytic determination of cobalt in grasses.

A flow system with zone merging and zone trapping in the main reactor was proposed. The sample and reagent inserted aliquots merge together and the resulting zone is directed towards a displaceable reactor inside which its most concentrated portion is trapped. After the pre-set TRAP period, the handled sample is released towards detection.

Spectrophotometric flow injection monitoring of sulfide during sugar fermentation.

A spectrophotometric flow injection procedure involving N,N-dimethyl-p-phenylenediamine (DMPD) is applied to the sulfide monitoring of a sugar fermentation by Saccharomyces cerevisiae under laboratory conditions. The gaseous chemical species evolving from the fermentative process, mainly CO(2), are trapped allowing a cleaned sample aliquot to be collected and introduced into the flow injection analyzer. Measurement rate, signal repeatability, detection limit and reagent consumption per measurement were estimated as 150 h(-1), 0.

Cadmium telluride nanocrystals as luminescent sensitizers in flow analysis.

A fully automated multipumping flow system (MPFS) using water-soluble CdTe quantum dots (QD) as sensitizers is proposed for the chemiluminometric determination of the anti-diabetic drugs gliclazide and glipizide in pharmaceutical formulations. The nanocrystals acted as enhancers of the weak CL emission produced upon oxidation of sulphite by Ce(IV) in acidic medium, thus improving sensitivity and expanding the dynamical analytical concentration range. By interacting with the QD, the two analytes prevented their sensitizing effect yielding a chemiluminescence quenching of the Ce(IV)-SO(3)(2-)CdTe QD system.

Exploitation of a single interface flow system for on-line aqueous biphasic extraction.

The exploitation of aqueous biphasic extraction is proposed for the first time in flow analysis. This extraction strategy stands out for being environmentally attractive since it is based in the utilization of two immiscible phases that are intrinsically aqueous. The organic solvents of the traditional liquid-liquid extractions are no longer used, being replaced by non-toxic, non-flammable and non-volatile ones.