An Improved Reflection Colorimeter Integrated with a Coaxial Optical-fiber Cable for Highly Sensitive Solid-phase Colorimetry Using a Membrane Filter.

Highly sensitive solid-phase colorimetry for nickel ion was demonstrated using an improved reflection colorimeter equipped with a coaxial optical-fiber cable. The nickel complex with α-furil dioxime was collected on a small-size membrane filter embedded in a disposable syringe filter unit. The leading edge of the optical-fiber cable was connected to the syringe filter unit via a Luer-lock fitting, and the color intensity of the sample on the filter was evaluated accurately.

Droplet-counting Microtitration System for Precise On-site Analysis.

A new microtitration system based on the counting of titrant droplets has been developed for precise on-site analysis. The dropping rate was controlled by inserting a capillary tube as a flow resistance in a laboratory-made micropipette. The error of titration was 3% in a simulated titration with 20 droplets.

On-site Determination of Trace Arsenic by Reflection-Absorption Colorimetry of Molybdenum Blue Collected on a Membrane Filter.

An on-site determination method for trace arsenic has been developed by collecting it as molybdenum blue (MB) in the presence of tetradecyldimethylbenzylammonium chloride on a mixed cellulose ester membrane filter and by measuring reflection absorbance (RA) of MB on the filter using a laboratory-made palm-top size reflection-absorbance colorimeter with a red light-emitting diode. The value of RA was proportional to the amount of arsenic up to 0.5 μg with a detection limit of 0.

Ion-responsive Intramolecular Charge-transfer Absorption Using a Pyridinium Benzocrown Ether Conjugate.

A pyridinium benzocrown ether conjugated compound, 1, and its analogue with a non-crown ether unit, 2, have been prepared. Both compounds showed similar absorption spectra with two absorption bands at around 260 and 330 nm in acetonitrile. The bands at the longer wavelength side are associated with intramolecular charge transfer (ICT) absorption, in which the dialkoxyphenyl unit in benzocrown ether and the pyridinium unit act as the donor and acceptor, respectively.

Kinetic Spectrophotometric Determination of Trace Cadmium in Environmental Fresh Water with 5,10,15,20-Tetraphenyl-21H,23H-porphinetetrasulfonic Acid.

Cadmium-catalyzed complexation of zinc with 5,10,15,20-tetraphenyl-21H,23H-porphinetetrasulfonic acid (TPPS) was monitored spectrophotometrically. A kinetic parameter for the determination was obtained under kinetic consideration. Absorbance of zinc-TPPS at a fixed reaction time was proportional to the concentration of cadmium at pH 8 and 25°C.

Determination of very volatile organic compounds in water samples by purge and trap analysis with a needle-type extraction device.

Very volatile organic compounds (VVOCs), such as methanol, acetaldehyde, ethanol, acetone, acetonitrile, and dichloromethane, were extracted from water samples using a needle-type extraction device based on purge and trap analysis. The extracted analytes could then be determined by gas chromatography-mass spectrometry. By introducing carbon molecular sieves as the extraction medium, aqueous VVOCs could be successfully extracted using the extraction needle.

On-site catalytic determination of trace manganese in fresh water using oxidation of malachite green with periodate.

An on-site determination method for trace manganese has been developed using the manganese-catalyzed oxidation of Malachite Green (MG) with potassium periodate. Absorbance measurement of MG was carried out using a laboratory-made palm-top size colorimeter with a red-green-blue light-emitting diode. The reciprocal value (1/τ) of the reaction time at a fixed absorbance value for red light was chosen as a kinetic parameter for simple on-site analyses.

An on-site colorimetric technique for routine determination of chromium, iron and copper in bath solutions for chromium(III) conversion coating.

An on-site colorimetric technique was developed for the routine determination of chromium, iron and copper in bath solutions for the chromium(III) conversion coating. A portable colorimeter with a red-green-blue light emitting diode was used for the absorbance measurements. Iron and copper were determined as Fe(III)-thiocyanate and Cu(I)-bathocuproindisulfonate, respectively.

Development of a simple and low-cost device for fluorometric determination of selenium in water samples.

A portable spectrofluorometer device comprising an ultraviolet LED (380 nm) as a light source, an LED driver, a microsyringe as a cell, an optical fiber cable, a CCD spectrometer and a personal computer was used on-site. The device works on a battery for 3 h without the need to re-charge. The consumptions of reagents and sample solution can be reduced by using the device.

Development of a discrete flow system using a microsyringe as a cell for the photometric determination of iron.

A simple discrete flow system for the photometric determination of iron using a glass syringe as a mixer of a solution and as a sample cell has been developed. The system was assembled from a coupler combining a light source (a light-emitting diode, LED), a glass syringe, a photodiode detector (PD) and two plastic core fiber optics. The reagent and sample solutions were sucked into a syringe, and were then mixed by a reciprocating motion of a plunger, or simply turning the syringe upside down several times, manually.

Host-guest complexation affected by pH and length of spacer for hydroxyazobenzene-modified cyclodextrins.

Three modified beta-cyclodextrins appended with a hydroxyazobenzene as a dye unit, 1, 2, and 3, each incorporating a different length spacer between the beta-CD and the dye unit with a bis(propyl(oxyethylene)), butylene, and amide bond spacer, respectively, were synthesized in order to investigate their spectroscopic changes induced by pH and host-guest complexation as well as to investigate their conformations and guest-binding properties by means of absorption and induced circular dichroism spectroscopies in aqueous solutions. All hosts accommodated the dye unit in their own CD cavities with an orientation parallel to the CD axis, forming intramolecular complexes. When the pH of the solution changed, the structure changed in response to pH without conformational changes.

Tristimulus colorimetry using a digital still camera and its application to determination of iron and residual chlorine in water samples.

Tristimulus colorimetry using a digital still camera (DSC) as a colorimeter has been developed. A photograph of a sample and standard solutions was taken simultaneously with the DSC, and it was transferred to a PC. On the PC, the colors of the sample and of the standard solutions were analyzed and L* (brightness), a* (red-green component), and b* (yellow-blue component) values were determined with laboratory-made software.

A simple and portable colorimeter using a red-green-blue light-emitting diode and its application to the on-site determination of nitrite and iron in river-water.

A portable colorimeter using a red-green-blue light-emitting diode as a light source has been developed. An embedded controller sequentially turns emitters on and off, and acquires the signals detected by two photo diodes synchronized with their blinking. The controller calculates the absorbance and displays it on a liquid-crystal display.

A miniaturized FIA system for the determination of residual chlorine in environmental water samples.

The present study was aimed at developing a portable miniaturized FIA system with a two-electrode based amperometric detector for on-site monitoring of residual chlorine in environmental samples. The electrode potential control and current data collection were conducted with a home-designed potentiostat with a size of 150 x 100 x 40 mm and the weight of 350 g. It was confirmed that the amperometric response increased in proportion to the chlorine concentration up to 5 microg/ml, and the detection limit for chlorine was 0.

A four-wavelength channel absorbance detector with a light emitting diode-fiber optics assembly for simplifying the flow-injection analysis system.

A four-channel absorbance detector was developed for simplifying the flow-injection analysis (FIA). This detector used four light-emitting-diodes (LEDs) as light sources; their wavelengths were 470, 495, 590 and 635 nm, respectively. Their amplitudes were modulated electronically with different frequencies.