Flow injection colorimetric method using acidic ceric nitrate as reagent for determination of ethanol

Ceric ammonium nitrate has been used for qualitative analysis of ethanol. It forms an intensely colored unstable complex with alcohol. In this work, a simple flow injection (FI) colorimetric method was developed for the determination of ethanol, based on the reaction of ethanol with ceric ion in acidic medium to produce a red colored product having maximum absorption at 415 nm. Absorbance of this complex could be precisely measured in the FI system. A standard or sample solution was injected into a deionized water donor stream and flowed to a gas diffusion unit, where the ethanol diffused through a gas permeable membrane made of plumbing PTFE tape into an acceptor stream to react with ceric ammonium nitrate in nitric acid. Color intensity of the reddish product was monitored by a laboratory made LED based colorimeter and the signal was recorded on a computer as a peak. Peak height obtained was linearly proportional to the concentration of ethanol originally presented in the injected solution in the range of 0.1-10.0% (v/v) (r² = 0.9993), with detection limit of 0.03% (v/v). With the use of gas diffusion membrane, most of the interferences could be eliminated. The proposed method was successfully applied for determination of ethanol in some alcoholic beverages, validating by gas chromatographic method.     

Ultrasound-enhanced flow injection chemiluminescence for determination of hydrogen peroxide

A novel ultrasonic flow injection chemiluminescence (FI-CL) manifold for determining hydrogen peroxide (H2O2) has been designed and evaluated. Chemiluminescence obtained from the luminol-H2O2-cobalt(II) reaction was enhanced by applying 120 W of ultrasound for a period of 4 s to the reaction coil in the FI-CL system and this enhancement was verified by comparison with an identical manifold without ultrasound. The system was developed for determining ultra-trace levels of H2O2 and a calibration curve was obtained with a linear portion over the range of 10-200 nmol L(-1) H2O2 (correlation coefficient 0.9945). The detection limit (3sigma) and the quantification limit (LOQ) were found to be 1 x 10(-9) and 3.3 x 10(-9) mol L(-1) respectively and the relative standard deviation was 1.37% for 2 x 10(-7) mol L(-1) H2O2 (n = 10). The method was applied to the determination of trace amounts of H2O2 in purified water and natural water samples without any special pre-treatments.     

Sequential injection-capillary immunoassay system for determination of sialoglycoconjugates

An automatic immunoassay system for an assay of sialoglycoconjugates was developed based on the sequential injection technique. A cost effective plain glass capillary tube was used as a solid surface for immobilization of biomolecules via a simple physical adsorption which is adequate to tolerate the force of solution flowing through the capillary during the multi-steps immunoassay process. Immunoassay could be performed with many improvements—rapidity per sample as compared to the conventional micro-plate format (40 min vs. 5-8 h); lower cost and simpler as compared to fused silica capillary with covalent immobilization; and without problem of back pressure as compared to flow injection-bead based immunoassay. Performance of the sequential injection-capillary immunoassay was demonstrated by assay of sialoglycoconjugates level in human serum to differentiate cancer patients from healthy people.     

A simple and green analytical method for determination of iron based on micro flow analysis

A simple, inexpensive and reagent-less colorimetric micro flow analysis (μFA) system was implemented in a polymethyl methacrylate (PMMA) micro fluidic manifold. A T-shaped micro channel on a PMMA chip was fabricated by laser ablation and topped with molded polydimethylsiloxane (PDMS). The fabricated μFA system was integrated with the optical components as detector and applied to the determination of iron in water samples. It is based on the measurement of Fe(III)-nitroso-R salt complex at 720 nm formed by the reaction between Fe(III) and nitroso-R salt in an acetate buffer solution pH 5. The proposed μFA consumed very small amount of reagent and sample, it released waste of less than 2.0 mL h⁻¹. The relative standard deviation (R.S.D.) was less than 2% (n = 11) with the recovery of 98.7 ± 0.12 (n = 5). The linear range for the determination of iron in water samples was over the range of 0.05-4.0 μg mL⁻¹ with a correlation coefficient (r²) of 0.9994. The limit of detection (3σ) and limit of quantitation (10σ) were 0.021 μg mL⁻¹ and 0.081 μg mL⁻¹, respectively with a sample throughput of 40 h⁻¹.