Chips: How to build and implement fluidic devices in flow based systems

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

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).

3D-printed flow system for determination of lead in natural waters

The development of 3D printing in recent years opens up a vast array of possibilities in the field of flow analysis. In the present study, a new 3D-printed flow system has been developed for the selective spectrophotometric determination of lead in natural waters. This system was composed of three 3D-printed units (sample treatment, mixing coil and detection) that might have been assembled without any tubing to form a complete flow system. Lead was determined in a two-step procedure. A preconcentration of lead was first carried out on TrisKem Pb Resin located in a 3D-printed column reservoir closed by a tapped screw. This resin showed a high extraction selectivity for lead over many tested potential interfering metals. In a second step, lead was eluted by ammonium oxalate in presence of 4-(2-pyridylazo)-resorcinol (PAR), and spectrophotometrically detected at 520nm. The optimized flow system has exhibited a linear response from 3 to 120µgL^-1. Detection limit, coefficient of variation and sampling rate were evaluated at 2.7µgL^-1, 5.4% (n=6) and 4 sampleh^-1, respectively. This flow system stands out by its fully 3D design, portability and simplicity for low cost analysis of lead in natural waters.