A simple flow injection system with bead injection for trace iron determination

A simple and low cost flow injection (FI) system with bead injection (BI) was developed for determination of low concentration (mumol l(-1)) of iron in water samples. Chelex-100 chelating resin beads, trapped in a jet ring cell, were employed. The intensity of red complex of 1,10-phenanthroline with Fe(2+) was monitored using colorimetric detector with a LED green light source. Amount of total Fe (Fe(2+) and Fe(3+)) and Fe(2+) can be evaluated by with and without reduction of Fe(3+) using ascorbic acid. Lowest detectable levels of Fe(2+) were 0.90 and 0.45 mumol l(-1) for sample loading time of 3 and 5 min, respectively. Working range was up to 3.90 mumol l(-1) using 0.3% w/v 1, 10-phenanthroline. Percent recoveries of spiked water samples (0.90-2.33 mumol l(-1) of Fe(2+)) were 100-110%.     

Online assay of bone specific alkaline phosphatase with a flow injection-bead injection system

Alkaline phosphatase (ALP) has been used as one of the biomarkers for bone resorption and liver diseases. Normally, total alkaline phosphatase is quantified along with other symptoms to determine the releasing source of the alkaline phosphatase. A semi-automated flow injection-bead injection system was proposed to conveniently and selectively assay bone alkaline phosphatase (BALP) based on its specific binding to wheat germ coated beads. Amount of BALP in serum was determined from the intensity of the yellow product produced from bound BALP on the retained beads and its substrate pNPP. The used beads were discarded and the fresh ones were introduced for the next analysis. The reaction cell was designed to be opened and closed using a computer controlled solenoid valve for a precise incubation time. The performance of the proposed system was evaluated by using it to assay BALP in human serum. The results were compared to those obtained by using a commercial ELISA kit. The system is proposed to be an easy and cost effective system for quantification of BALP as an alternative to batch wise wheat germ specific binding technique.     

Development of HPLC Method for Catechins and Related Compounds Determination and Standardization in Miang (Traditional Lanna Fermented Tea Leaf in Northern Thailand)

High performance liquid chromatography (HPLC) for catechins and related compounds in Miang (traditional Lanna fermented tea leaf) was developed to overcome the matrices during the fermentation process. We investigated a variety of columns and elution conditions to determine seven catechins, namely (+)-catechin, (−)-gallocatechin, (−)-epigallocatechin, (−)-epicatechin, (−)-epigallocatechin gallate, (−)-gallocatechin gallate, (−)-epicatechin gallate, as well as gallic acid and caffeine, resulting in the development of reproducible systems for analyses that overcome sample matrices. Among the three reversed-phase columns, column C (deactivated, with extra dense bonding, double endcapped monomeric C18, high-purity silica at 3.0 mm × 250 mm and a 5 µm particle size) significantly improved the separation between Miang catechins in the presence of acid in the mobile phase within a shorter analysis time. The validation method showed effective linearity, precision, accuracy, and limits of detection and quantitation. The validated system was adequate for the qualitative and quantitative measurement of seven active catechins, including gallic acid and caffeine in Miang, during the fermentation process and standardization of Miang extracts. The latter contain catechins and related compounds that are further developed into natural active pharmaceutical ingredients (natural APIs) for cosmeceutical and nutraceutical products.     

Sustainable Downscaled Catalytic Colorimetric Determination of Manganese in Freshwater Using Smartphone-Based Monitoring Oxidation of 3,3′,5,5′-Tetramethylbenzidine by Periodate

A sustainable downscaled procedure using smartphone-based colorimetric determination of manganese (Mn(II)) was developed. This novel Mn(II) determination procedure is proposed using a simple, available microwell-plate platform and a smartphone as a detector. This approach is based on the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) by periodate using Mn(II) as a catalyst. The catalytic kinetics of Mn(II) under different conditions was investigated to determine the optimum condition where the different catalytic activities of various concentrations of Mn(II) evince. Under the optimum condition, the bluish-green product of oxidized TMB, proportioned to the concentration of Mn(II), was monitored using a smartphone camera, and the color signals were processed using ImageJ Software. The developed procedure showed great selectivity and sensitivity as linearity ranged from 1.8 × 10⁻⁶ to 4.6 × 10⁻⁵ M (0.1 to 2.5 μg/mL). The limits of detection and quantitation were 3.6 × 10⁻⁶ and 1.1 × 10⁻⁵ M (0.2 and 0.6 μg/mL), respectively. The determination of Mn(II) in freshwater samples was demonstrated to assess environmental water quality as an initial model to more easily promote water management according to the United Nations Sustainable Development Goals (UN-SDGs). The intensity of the red could be successfully applied to evaluate Mn(II) in canals and river water with no significant differences compared with the reference method of Inductively Coupled Plasma Optical Emission Spectrometry at a confidence level of 95%.     

Sequential injection-bead injection-lab-on-valve coupled to high-performance liquid chromatography for online renewable micro-solid-phase extraction of carbamate residues in food and environmental samples

A sequential injection‐bead injection‐lab‐on‐valve system was hyphenated to HPLC for online renewable micro‐solid‐phase extraction of carbamate insecticides. The carbamates studied were isoprocarb, methomyl, carbaryl, carbofuran, methiocarb, promecarb, and propoxur. LiChroprep^® RP‐18 beads (25–40 μm) were employed as renewable sorbent packing in a microcolumn situated inside the LOV platform mounted above the multiposition valve of the sequential injection system. The analytes sorbed by the microcolumn were eluted using 80% acetonitrile in 0.1% acetic acid before online introduction to the HPLC system. Separation was performed on an Atlantis C‐18 column (4.6×150 mm, 5 μm) utilizing gradient elution with a flow rate of 1.0 mL/min and a detection wavelength at 270 nm. The sequential injection system offers the means of performing automated handling of sample preconcentration and matrix removal. The enrichment factors ranged between 20 and 125, leading to limits of detection (LODs) in the range of 1–20 μg/L. Good reproducibility was obtained with relative standard deviations of <0.7 and 5.4% for retention time and peak area, respectively. The developed method has been successfully applied to the determination of carbamate residues in fruit, vegetable, and water samples.     

Sequential injection Lab-at-valve (SI-LAV) segmented flow system for kinetic study of an enzyme

A sequential injection-Lab-at-valve (SI-LAV) segmented flow system for kinetic study of an enzyme was developed. Air segments were introduced for separation of enzyme and substrate zones and separation of the stacked zones from the carrier solution which ensure the measurement of the initial rate and minimize the dilution/dispersion effect. The open- ended mixing chamber makes it possible to use air segments in the flow system without the need for additional air segment discarding steps. The enzyme horseradish peroxidase (HRP) kinetic parameters based on initial rate was used as a model study. The operation of the system is virtually the same as that of the conventional batch-wise process. The kinetic parameters (i.e. K(m) and V(max)) of HRP obtained using the proposed system agree well with those obtained using the batch-wise process as well. The proposed system offers additional benefits of volume down scaling, improved rapidity and automatic features that does not require a skillful operator.     

Simple sequential injection analysis systems with a dynamic surface tension detector.

Simple sequential injection analysis systems with DSTD (SIA/DSTD) have been developed. One was employed for the study of the effects of the ion contents in solutions to the dynamic surface pressure of ionic surfactants. The results from the studies show the possibility for an alternative simple fast screening, but also a sensitive procedure for water quality determination. Another simple SIA/DSTD system has been demonstrated for the quantification of an anionic surfactant using a single standard calibration.     

Simple spectrophotometric flow injection system with an in-valve minicolumn for enhancement during the determination of chromium(III) using EDTA.

A simple spectrophotometric flow injection (FI) procedure for the determination of Cr(III) using ethylenediaminetetraacetic acid (EDTA) was developed. An FI system with a column packed with Amberlite IR-120(H) was employed for sample pretreatment. This leads to the possibility of a single standard calibration. A linear calibration in a range of 10-27 microg Cr(III) was obtained with a detection limit of 1 microg Cr(III) and RSD of 2% (18 microg Cr(III), n=12). The proposed procedure was applied for determination of Cr(III) in leachate and dietary supplement samples. The results agreed with those obtained by the standard methods.     

Webcam camera as a detector for a simple lab-on-chip time based approach

A modification of a webcam camera for use as a small and low cost detector was demonstrated with a simple lab-on-chip reactor. Real time continuous monitoring of the reaction zone could be done. Acid-base neutralization with phenolphthalein indicator was used as a model reaction. The fading of pink color of the indicator when the acidic solution diffused into the basic solution zone was recorded as the change of red, blue and green colors (%RBG.) The change was related to acid concentration. A low cost portable semi-automation analysis system was achieved.