Flow analysis changed significantly the way of performing chemical analysis by (i) mechanization of analytical procedures in a continuous flowing stream with minimal sample intercontamination; (ii) analytical measurements without attaining chemical equilibria, thus increasing the applicability of kinetic methods and allowing the exploitation of non-quantitative processes; (iii) exploitation of concentration gradients and (iv) use of unstable reagents or measurement of unstable products. Flow-based procedures are generally characterized by high sample throughput, improved precision, minimized waste generation, and often better selectivity. The performance of detection systems is usually improved because of the in-line sample conditioning and measurements under reproductive dynamic conditions and timing. However, after achieving several innovations, perspectives for further developments have been questioned mainly because of the recent decrease in the number of publications on flow analysis. The aim of this review is then to discuss the impact of flow-based methods on chemical analysis, emphasizing recent applications and developments, including miniaturization, bioanalysis, microextractions, green analytical chemistry and synergic hyphenation with other techniques and processes. The author's personal view about research perspectives in the field is also presented.

A sequential injection analysis (SIA) methodology was developed for fluorimetric determination of quinine in soft drinks. Minimum dispersion and efficient mixing were achieved by aspirating 200 mL of sample between two 100 mL reagent zones (0.10 mol L-1 H2SO4) at flow rate of 250 mL s-1 and using a reaction coil length of 50 cm (0.8 mm internal diameter). Linear response for quinine concentrations (C) between 0.050 and 100.0 mg L-1 was described by: I = (532 ± 40) + (2.36 ± 0.04) C, with r = 0.999, where I is the relative fluorescence intensity. The coefficient of variation and limits of detection and quantification were 1.9% (0.50 mg L-1 n = 10), 2.3 and 4.5 mg L-1, respectively. The sampling throughput was 60 analyses per hour, consuming 2.2 mL of concentrated H2SO4 and producing 4 mL of wastes per analysis. No statistically significant differences were observed between the results obtained by the proposed SIA methodology and the ones obtained by the batch procedure.

A sequential injection method with square wave anodic stripping voltammetry (SI-SWASV) using screen printed and crystalline gold electrode was developed for determination of As(III). The carrier solution used for electrode conditioning and stripping medium was composed of 0.050 mol L-1 HCl, whereas the supporting electrode for samples (deposition medium) was 0.50 mol L-1 HCl. The limits of detection and quantification were 20 and 70 nmol L-1 (1.5 and 5.2 µg L-1), respectively. This limit of quantification is almost two times lower than the maximum concentration of As(III) allowed in waters by World Health Organization (10 µg L-1). The sampling throughput was 20 analyses per hour using a sample volume of 1500 µL, pumped through the flow cell at the flow rate of 15 µL s-1. Screen printed gold electrodes were not suitable for work with 0.50 mol L-1 HCl because the results were strongly dependent on the lot of sensors. Crystalline gold electrodes provided reproducible results and the method was applied for determination of As(III) in river water samples. The accuracy was evaluated by recovery studies and analyses by Graphite Furnace Atomic Absorption Spectrometry, providing recoveries between 95 and 108%.

A new configuration for coupling a gas diffusion cell to a sequential injection system is presented. The matrix exchange is made without the need for additional rotary injection valves or peristaltic pumps, keeping the original mechanical components of the sequential injection apparatus: one syringe pump (or peristaltic pump) and one selection valve. The system was tested constructing analytical curves for sulfide exploring the formation of the methylene blue dye. The proposed method has a detection limit of 60 µg L-1 S2-, with a linear dynamic range between 0.10 and 4.0 mg L-1 S2- concentrations, with a sampling frequency of 20 h-1.

The year of 2010 marks the 20th anniversary of the development of Sequential Injection Analysis (SIA) by Ruzicka and Marshall. Considered the second generation of the flow injection methods, this article briefly describes the history, the basic principles of the technique and reviews all papers developed by Brazilian scientists aiming the divulgation of this automation technique in Analytical Chemistry.

A mechanized system for the determination of beta-blockers in pharmaceutical formulations is presented. Using the Sequential Injection Analysis (SIA) technique it was achieved a simple, economical and versatile methodology adaptable to any pharmaceutical control involving these substances. It does not require any pre-treatment for the samples, as they must only be dissolved in acid before analysis. Linear calibration plots were obtained for metoprolol (40.52 - 250 mg L-1), acebutolol (32.85 - 140 mg L-1) and propranolol (16.58 - 120 mg L-1). A R.S.D. lower than 5% was attained. The methodology was used in tablets, injections and prolonged-release capsules. Common excipients used in pharmaceuticals do not interfere. Statistical comparison of the results obtained with the proposed methodology and with the official methods showed good agreement (95% confidence level). SIA system produces only 2.50 mL of effluents per determination whereas the reference methodologies consume around 140 mL.

This work proposes a sequential injection analysis (SIA) system for the spectrophotometric determination of norfloxacin (NOR) and ciprofloxacin (CIP) in pharmaceutical formulations. The methodology was based on the reaction of these drugs with p-(dimethylamino)cinnamaldehyde in micellar medium, producing orange colored products (λmax = 495 nm). Beer´s law was obeyed in the concentration range from 2.75x10-5 to 3.44x10-4 mol L-1 and 3.26x10-5 to 3.54x10-4 mol L-1 for NOR and CIP, respectively and sampling rate was 25 h-1. Commercial samples were analyzed and results obtained through the proposed method were in good agreement with those obtained using the reference procedure for a 95% confidence level.

This work describes a photo-reactor to perform in line degradation of organic compounds by photo-Fenton reaction using Sequential Injection Analysis (SIA) system. A copper phthalocyanine-3,4',4<FONT FACE=Symbol><FONT FACE=Symbol>²</FONT></FONT>,4<FONT FACE=Symbol><FONT FACE=Symbol>²¢</FONT></FONT>-tetrasulfonic acid tetrasodium salt dye solution was used as a model compound for the phthalocyanine family, whose pigments have a large use in automotive coatings industry. Based on preliminary tests, 97% of color removal was obtained from a solution containing 20 µmol L-1 of this dye.