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Towards direct analysis of solid and liquid samples exploiting a 3D printed dialysis unit and sequential injection: Application for automated derivatization and determination of gamma-aminobutyric acid in foodstuff and beverages
(2020-02-08)
Kasetsoontorn, Bhoonnarasa
;
Choengchan, Nathawut
In this work, a new design of a dialysis unit for direct analysis of solid and liquid samples is presented. The homemade unit was constructed using a 3D printer due to its simple and fast fabrication ability. The dialysis unit is composed of cylindrical-shaped donor and acceptor chambers. A stainless steel sieve is installed inside the donor chamber. SEM images clearly showed that the sieve prevented membrane blockage by suspension particles in the sample. Multiple dialysis units were connected to a sequential injection (SI) system for serial determination of gamma-aminobutyric acid (GABA) in solid and liquid samples. The dialysate from each dialysis unit was consecutively aspirated into the SI flow line for on-line derivatization of GABA with 2-hydroxy-1-naphthaldehyde (3.0% w/v). The derivative was detected spectrophotometrically at 425 nm. The linear calibration range extended to 1000 mg L−1 GABA (r2 > 0.99) with high precision (1.2 %RSD). The developed system was applied to analysis of dietary supplements, grains of germinated brown rice and milk. The samples were directly introduced into the donor chamber either as powder or liquids. The measured GABA content using the developed method was compared using high performance liquid chromatography, with good agreement using Pearson's correlation (r2 = 0.9999). The method has high accuracy based on recovery studies (99.8 ± 1.5%) and high sample throughput (64 samples h−1).
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Sequential injection for determination of gamma-aminobutyric acid based on its effect on second order light scattering of silver nanoparticles
(2016-08-01)
Jinnarak, Amornrassamee
;
Anantavichian, Pattarapon
;
Intanin, Apichai
;
Fungladda, Suchada
;
Choengchan, Nathawut
An automated sequential injection (SI) with second order light scattering (SOS) detection for determination of gamma-aminobutyric acid (GABA) was developed. Quantitation is based on electrostatic interaction between GABA and citrate-capped silver nanoparticles (AgNPs). In acetate buffer at pH 3.8, the positively charged GABA induces the nanoparticles to aggregate. This results in a change of light scattering monitored using a spectrofluorometer. In this work, working standard solutions of GABA were prepared in-line by the SI system pumping appropriate volumes of a stock solution of GABA and acetate buffer into a holding coil. Solution of AgNPs was subsequently drawn into the coil. The reaction zone was then transferred to the spectrofluorometer, set with excitation and detection wavelengths at 300 and 600 nm, respectively. Under optimised condition, the SOS intensity was proportional to the concentration of GABA. As a result, a linear curve was obtained in the range of 100–400 mg L−1 GABA, with a lower limit of detection of 39.6 mg L‐1. Good precision of analysis was achieved, with 0.6 and 3.3% relative standard deviation (RSD) for external calibration (n = 5) and standard addition (n = 3), respectively. The developed method was successfully applied for quantification of GABA in dietary supplements (2 samples) and samples of instant green tea (2 samples).
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Reagent-free analytical flow methods for the soft drink industry: Efforts for environmentally friendly chemical analysis
(2012-10-25)
Mantim, Thitirat
;
Saetear, Phoonthawee
;
Teerasong, Saowapak
;
Chan-Eam, Sumonmarn
;
Sereenonchai, Kamonthip
The evolution of an entirely green analytical system for industrial quality control of carbonated drinks is described. The developed flow system is capable of providing analytical data of the dissolved CO <inf>2</inf>, sucrose, and color of a sample consecutively in real-time. The system has been carefully designed on the basis of "reagent-free", meaning that no added chemicals are required for the analysis. The system first vaporizes CO <inf>2</inf> from the soft drink in a gas-liquid separation chamber, with a channel for a flow of pure water as the CO <inf>2</inf> acceptor. The dissolved CO <inf>2</inf> alters the conductivity of the water stream, which is directly related to the concentration of CO <inf>2</inf> in the soft drink. The sucrose content is measured based on the "schlieren effect", the sample plug flows out of the vaporization chamber into a colorimeter with a near-infrared/light-emitting diode (NIR/LED) as light source. The schlieren effect arises at the boundary of pure water and soft drink with refraction of light in proportion to the sugar concentration. The system also measures the absorbance of the sample using an RGB-LED. The related principles and preliminary experiments as proof of concept are described as well as the construction of the flow system for this completely reagent-free analyzer. A simple flow injection system using the schlieren effect was also developed for rapid quantitative analysis of sugar in noncarbonated soft drinks. © 2012 IUPAC.
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