Development of a tubular fluoride potentiometric detector for flow analysis

Spectrophotometric Fluoride Determination Using St. John's Wort Extract as a Green Chromogenic Complexant for Al(III)

In this study, we applied an innovative approach of green analytical chemistry to develop a novel and eco-friendly chromogenic agent for fluoride determination by making use of the nontoxic Al(III)-flavonoid complex in a natural extract from St. John's wort plant. The initial intensely yellow-colored Al(III)-flavonoid complex formed in the plant extract was converted to a colorless AlF₆ ^3- complex with increasing amounts of fluoride, and color bleaching of the Al-flavonoid chromophore (measured as absorbance decrement) was proportional to fluoride concentration. The developed method gave a linear response within the F^- concentration range of 0.11-1.32 mM with the LOD and LOQ values of 0.026 mM (0.5 mg L^-1) and 0.079 mM (1.5 mg L^-1), respectively. The LOD value for fluoride was below the WHO-permissible limit (1.5 mg L^-1) and the US-EPA-enforceable limit (4 mg L^-1) in water. The possible interference effects of common anions (Cl^-, Br^-, I^-, NO₃ ^-, HCO₃ ^-, SO₄ ^2-, and PO₄ ^3-) and cations (K⁺, NH₄ ⁺, Ag⁺, Ca²⁺, Mg²⁺, Mn²⁺, Fe²⁺, and Fe³⁺) were investigated; the observed interferences from Fe²⁺, Fe³⁺, and PO₄ ^3- were easily eliminated by masking iron with the necessary amount of Na₂EDTA without affecting the blank absorbance of the Al(III)-flavonoid complex, precipitating phosphate with Ag(I) salt, and partly neutralizing alkaline water samples to pH 4 with acetic acid. The developed method was applied to real water samples and also validated against a reference spectroscopic method at the 95% confidence level.

Ring Electrode Geometry for Microfluidic Electrochemistry

We developed a ring electrode sensor for down-stream electrochemical sensing of microfluidic ELISA assay. The sensor is designed to easily integrate into the flow environment. Noble metal inks on Low Temperature Co-fired Ceramic provide straight forward fabrication at the mesoscale yielding robust sensors with very low sensing volumes. Two different sensor geometries were modeled. The best design was fabricated and tested in both static and flowing solutions. The sensor exhibits both macroelectrode and microelectrode behavior depending on fluid flow rate. Sensors of this type may be ideal for applications where electrochemical detection is desired in a flowing solution since the ring electrode has low propensity for bubble trapping.

Open ISEmeter: An open hardware high-impedance interface for potentiometric detection

In this work, a new open hardware interface based on Arduino to read electromotive force (emf) from potentiometric detectors is presented. The interface has been fully designed with the open code philosophy and all documentation will be accessible on web. The paper describes a comprehensive project including the electronic design, the firmware loaded on Arduino, and the Java-coded graphical user interface to load data in a computer (PC or Mac) for processing. The prototype was tested by measuring the calibration curve of a detector. As detection element, an active poly(vinyl chloride)-based membrane was used, doped with cetyltrimethylammonium dodecylsulphate (CTA(+)-DS(-)). The experimental measures of emf indicate Nernstian behaviour with the CTA(+) content of test solutions, as it was described in the literature, proving the validity of the developed prototype. A comparative analysis of performance was made by using the same chemical detector but changing the measurement instrumentation.

Recent advances in flow injection analysis

A dynamic development of methodologies of analytical flow injection measurements during four decades since their invention has reinforced the solid position of flow analysis in the arsenal of techniques and instrumentation of contemporary chemical analysis.

Determination of fluoride in tap water in Morocco using a direct electrochemical method

This study aimed to analyze the fluoride concentration in tap drinking water in different cities of Morocco using an electrochemical ion-selective method. Three samples were collected from each thirteen selected cities in the period between March and May 2011. The median value of fluoride was 0.94 mg/L (0.21-2.97). High fluoride concentrations (>0.8 mg/L) were found in sixteen cities. Very high values were found in phosphate regions such as Khouribga which is known to be an endemic dental fluorosis area. This study has shown that the concentration of fluoride in drinking water exceeds the limit especially in phosphate regions.