RESUMEN

This work aims to develop a more robust, easy-to-use, low-pressure, and cost-effective nonsuppressed open tubular capillary ion chromatography (NS-OTIC) approach with online dialysis for small ions determination in drinks. The fabricated device was applied for two selected columns, including poly(butadiene-maleic acid) on a 50-µm bore and AS18 Latex on 25-µm bore fused silica capillaries, for the separation of mixed cations (Na+, K+, Ca2+, Mg2+) and mixed anions (Cl-, Br-, NO2-, NO3-), respectively. High concentrations of ions (up to 100 mM) level can be directly introduced into the NS-OTIC system without an off-line (manual) dilution step. The linear relationship of the peak area and concentration of model ions can be obtained with a resolution > 1.1. The repeatability of the peak area for both OTIC columns was < 6% RSD. Juice and tea samples were successfully analyzed with % recoveries of 77-112 and 90-119 for cation and anion determinations, respectively.

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RESUMEN

A cost-effective long-path absorption liquid core waveguide (LCW) device was fabricated from a typical Teflon tube, and using a high refractive index (RI) medium of acid. It was incorporated in a flow injection-gas diffusion system for the sensitive determination of sulfide via methylene blue (MB) chemistry. The gas diffusion unit could prevent some interferences in samples. The limit of detection of 0.13 µmol L-1 was achieved without using a preconcentration procedure. The proposed device was successfully applied for sulfide determination in canal water samples with 88.7 - 103% recovery.

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RESUMEN

A cost-effective flow-batch analysis approach with colorimetric measurement has been developed for sulfide ion determination in turbid water samples without using a conventional pump and valve. Under an acidic condition, sulfide ion was converted to hydrogen sulfide gas and liberated out from other complicated matrices. The porous membrane-based diffusion scrubber was utilized as a gas trapping unit for hydrogen sulfide gas separation/preconcentration. From the correlation of sulfide ion concentration and disappearance of sodium nitroprusside reagent detection by using a homemade LED-photodiode based colorimetry, a linear relationship of sulfide ion concentration and absorbance can be obtained with relative standard deviation (%RSD) less than 5%. The limit of detection was 5.6 µmol L-1. The proposed system was applied for sulfide ion determination in wastewater samples with the recoveries of 91.0 - 105.2%. The proposed system is a robust setup and able to handle turbid water samples without a sample filtering step.

RESUMEN

In this work, a homemade direct current (DC) conductivity detector as an alternative cost-effective detection device has been fabricated and investigated to use in flow analysis system. Under the selected appropriate conditions of flow system, the electrolysis of a carrier stream at the conductivity detector was negligible and provides well-defined signal. The cost-effective DC conductivity detector was demonstrated to couple with gas diffusion flow injection system for determination of dissolved inorganic carbon (DIC) in water. The method is based on the conversion of DIC (dissolved CO2, HCO3- and CO32-) presented in the injected sample to carbon dioxide in an acidic donor stream and then CO2 gas diffuses through a hydrophobic porous membrane to an acceptor stream. As a result, the change of conductivity signal was observed corresponding to DIC concentration. A linear calibration range of DIC in 1.0-10mmolL-1, with limit of detection of 70µmolL-1, repeatability of <3% RSD and 15 injections h-1 sample throughput can be obtained. This method was applied for DIC determination in natural water.