Microflow injection analysis based on modular 3D platforms and colorimetric detection for Fe(III) monitoring in a wide concentration range

A modular microflow injection analysis (microFIA) system for the determination of Fe(III) in a bioleaching reactor has been designed, developed and validated. The different modules of the analyzer (mixer, diluter, disperser and detector) were 3D-printed. Fe(III) quantification is due by measuring the color intensity of the chelate formed between Fe(III) and salicylic acid at 525 nm. The device has been designed to dilute, disperse and detect high Fe(III) concentrations in the form of an inexpensive multi-step photometric flow cell that uses an light-emitting diode (LED) as a light source and an light-dependent resistor (LDR) as a light intensity detector. This microFIA system has been shown to be suitable for automatic and continuous determination of Fe(III) in the operation of a bioreactor for the oxidation of Fe(II). The device has a good repeatability (less than 5% of coefficient of variation in the whole range of concentrations) and accuracy of around 100%. The analyzer features an exceptional wide linear range, between 25 and 6000 mg·L-1. The device was successfully applied to the determination of Fe(III) in real samples. The obtained results proved that the method is applicable for accurate, precise, rapid, and low-cost colorimetric analysis and didn't show significant differences with a conventional UV-Vis method.

Multi-reverse flow injection analysis integrated with multi-optical sensor for simultaneous determination of Mn(II), Fe(II), Cu(II) and Fe(III) in natural waters

Multi-reverse flow injection analysis (Mr-FIA) integrated with multi-optical sensor was developed and optimized for the simultaneous determination of multi ions; Mn(II), Fe(II), Cu(II) and Fe(III) in water samples. The sample/standard solutions were propelled making use of a four channels peristaltic pump whereas 4 colorimetric reagents specific for the metal ions were separately injected in sample streams using multi-syringe pump. The color zones that formed in the individual mixing coils were then streamed into multi-channels spectrometer, which comprised of four flows through cell and four pairs of light emitting diode and photodiode, whereby signals were measured concurrently. The linearity range (along with detection limit, µgL^-1) was 0.050-3.0(16), 0.30-2.0 (11), 0.050-1.0(12) and 0.10-1.0(50)mgL^-1, for Mn(II), Fe(II), Cu(II) and Fe(III), respectively. In the interim, the correlation coefficients were 0.9924-0.9942. The percentages relative standard deviation was less than 3. The proposed system was applied successfully to determine targeted metal ions simultaneously in natural water with high sample throughput and low reagent consumption, thus it satisfies the criteria of Green Analytical Chemistry (GAC) and its goals.

Miniaturization of spectrophotometry based on micro flow analysis using norfloxacin as less-toxic reagent for iron determination

A micro flow analysis (μFA) system has been designed and fabricated for determination of total iron. The system consists of a microchannels fabricated by etching the polymethyl methacrylate (PMMA) by using laser ablation techniques and a sealed polydimethylsiloxane (PDMS) as top plate. The PMMA micro-flow was topped with a home-made polydimethylsiloxane (PDMS) micro-flow through cell, which was integrated with light emitting diode (LED) as light source and a USB 2000 spectrometer as detector. The proposed μFA system was applied to determination of Fe(III) using norfloxacin as a less-toxic complexing agent in an acetate buffer solution pH 4.0, resulting in a yellow colored complex which gave the maximum absorption at 430nm. Under the optimum conditions, a linear calibration graph was obtained in the concentration range of 0.20-5.00mgL(-1). The limit of detection (LOD, defined as 3σ) and limit of quantification (LOQ, defined as 10σ) were 0.12 and 0.45mgL(-1), respectively. The relative standard deviation (R.S.D.) for repeatability and reproducibility were less than 1.50% and 1.24% (n=11) for 0.2mgL(-1) and 1.0mgL(-1) Fe(III), respectively. The proposed method was successfully applied to the determination of total iron in water samples, validated by the FAAS standard method after digestion by HNO3 and H2O2.