An environmental friendly procedure for photometric determination of hypochlorite in tap water employing a miniaturized multicommuted flow analysis setup.

A photometric procedure for the determination of ClO(-) in tap water employing a miniaturized multicommuted flow analysis setup and an LED-based photometer is described. The analytical procedure was implemented using leucocrystal violet (LCV; 4,4',4''-methylidynetris (N,N-dimethylaniline), C(25)H(31)N(3)) as a chromogenic reagent. Solenoid micropumps employed for solutions propelling were assembled together with the photometer in order to compose a compact unit of small dimensions. After control variables optimization, the system was applied for the determination of ClO(-) in samples of tap water, and aiming accuracy assessment samples were also analyzed using an independent method. Applying the paired t-test between results obtained using both methods, no significant difference at the 95% confidence level was observed. Other useful features include low reagent consumption, 2.4 µg of LCV per determination, a linear response ranging from 0.02 up to 2.0 mg L(-1) ClO(-), a relative standard deviation of 1.0% (n = 11) for samples containing 0.2 mg L(-1) ClO(-), a detection limit of 6.0 µg L(-1) ClO(-), a sampling throughput of 84 determinations per hour, and a waste generation of 432 µL per determination.

Downscaling a multicommuted flow injection analysis system for the photometric determination of iodate in table salt.

In this work a downscaled multicommuted flow injection analysis setup for photometric determination is described. The setup consists of a flow system module and a LED based photometer, with a total internal volume of about 170 microL. The system was tested by developing an analytical procedure for the photometric determination of iodate in table salt using N,N-diethyl-henylenediamine (DPD) as the chromogenic reagent. Accuracy was accessed by applying the paired t-test between results obtained using the proposed procedure and a reference method, and no significant difference at the 95% confidence level was observed. Other profitable features, such as a low reagent consumption of 7.3 microg DPD per determination; a linear response ranging from 0.1 up to 3.0 m IO(3)(-), a relative standard deviation of 0.9% (n=11) for samples containing 0.5 m IO(3)(-), a detection limit of 17 microg L(-1) IO(3)(-), a sampling throughput of 117 determination per hour, and a waste generation 600 microL per determination, were also achieved.

A full automatic device for sampling small solution volumes in photometric titration procedure based on multicommuted flow system.

In this work, an automatic device to deliver titrant solution into a titration chamber with the ability to determine the dispensed volume of solution, with good precision independent of both elapsed time and flow rate, is proposed. A glass tube maintained at the vertical position was employed as a container for the titrant solution. Electronic devices were coupled to the glass tube in order to control its filling with titrant solution, as well as the stepwise solution delivering into the titration chamber. The detection of the titration end point was performed employing a photometer designed using a green LED (lambda=545 nm) and a phototransistor. The titration flow system comprised three-way solenoid valves, which were assembled to allow that the steps comprising the solution container loading and the titration run were carried out automatically. The device for the solution volume determination was designed employing an infrared LED (lambda=930 nm) and a photodiode. When solution volume delivered from proposed device was within the range of 5 to 105 mul, a linear relationship (R = 0.999) between the delivered volumes and the generated potential difference was achieved. The usefulness of the proposed device was proved performing photometric titration of hydrochloric acid solution with a standardized sodium hydroxide solution and using phenolphthalein as an external indicator. The achieved results presented relative standard deviation of 1.5%.

An automatic flow injection analysis procedure for photometric determination of ethanol in red wine without using a chromogenic reagent.

An automatic reagentless photometric procedure for the determination of ethanol in red wine is described. The procedure was based on a falling drop system that was implemented by employing a flow injection analysis manifold. The detection system comprised an infrared LED and a phototransistor. The experimental arrangement was designed to ensure that the wine drop grew between these devices, thus causing a decrease in the intensity of the radiation beam coming from the LED. Since ethanol content affected the size of the wine drop this feature was exploited to develop an analytical procedure for the photometric determination of ethanol in red wine without using a chromogenic reagent. In an attempt to prove the usefulness of the proposed procedure, a set of red wines were analysed. No significant difference between our results and those obtained with a reference method was observed at the 95% confidence level. Other advantages of our method were a linear response ranging from 0.17 up to 5.14 mol L(-1) (1.0 up to 30.0%) ethanol (R = 0.999); a limit of detection of 0.05 mol L(-1) (0.3%) ethanol; a relative standard deviation of 2.5% (n = 10) using typical wine sample containing 2.14 mol L(-1) (12.5%) ethanol; and a sampling rate of 50 determinations per hour.

Reagent generation for chemical analysis assisted by ultrasonic irradiation.

Few methods, such as coulometrics, have been developed to produce reagents in situ for analytical purposes. In this work the concept related to the generation of ultrasound-assisted reagents was exploited to yield oxidizing species in batch and flow systems of analysis. To evaluate the efficiency of ultrasound-assisted reagent generation, the conversion of Fe(2+) to Fe(3+) associated with the 1,10-o-phenantroline spectrophotometric method was tested to compare the oxidizing power of the produced species from pure water and aqueous solutions saturated with CCl(4) or CHCl(3) irradiated ultrasonic waves. Irradiation processes were conducted with an ultrasonic bath (40 kHz and 140 W). The borosilicate reactor was used in the batch studies, while the PTFE tube reactor was used for setting up the flow system, with the temperature during irradiation being controlled using a thermostatic bath. The sonochemical production of oxidizing agents was demonstrated to be efficient for chemical analysis in batch and flow systems. This technique was exemplified by oxidation of iodide and ferrous ions. It was observed that after 120 min of sonication approximately 40 microg of Fe(2+) was quantitatively oxidized to Fe(3+). Similar result was obtained by the irradiation of iodine in aqueous-organic medium.