Saowapak Teerasong

A reagent-free SIA module for monitoring of sugar, color and dissolved CO2 content in soft drinks.

This work presents a new sequential injection analysis (SIA) method and a module for simultaneous and real-time monitoring of three key parameters for the beverage industry, i.e., the sugar content (measured in Brix), color and dissolved CO(2). Detection of the light reflection at the liquid interface (the schlieren effect) of sucrose and water was utilized for sucrose content measurement. A near infrared LED (890+/-40 nm) was chosen as the light source to ensure that all the ingredients and dyes in soft drinks will not interfere by contributing light absorption. A linear calibration was obtained for sucrose over a wide concentration range (3.1-46.5 Brix). The same module can be used to monitor the color of the soft drink as well as the dissolved CO(2) during production. For measuring the color, the sample is segmented between air plugs to avoid dispersion. An RGB-LED was chosen as the light source in order to make this module applicable to a wide range of colored samples. The module also has a section where dissolved CO(2) is measured via vaporization of the gas from the liquid phase. Dissolved CO(2), in a flowing acceptor stream of water resulting in the change of the acceptor conductivity, is detected using an in-house capacitively coupled contactless conductivity detector (C(4)D). The module includes a vaporization unit that is also used to degas the carbonated drink, prior the measurements of sucrose and color within the same system. The method requires no chemicals and is therefore completely friendly to the environment.

Reagent-free analytical flow methods for the soft drink industry: Efforts for environmentally friendly chemical analysis

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 CO2, 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 CO2 from the soft drink in a gas–liquid separation chamber, with a channel for a flow of pure water as the CO2 acceptor. The dissolved CO2 alters the conductivity of the water stream, which is directly related to the concentration of CO2 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.

Zone fluidics for measurement of octanol-water partition coefficient of drugs.

A novel zone fluidics (ZF) system for the determination of the octanol-water partition coefficient (Pow) of drugs was developed. The ZF system consisted of a syringe pump with a selection valve, a holding column, a silica capillary flow-cell and an in-line spectrophotometer. Exact microliter volumes of solvents (octanol and phosphate buffer saline) and a solution of the drug, sandwiched between air segments, were sequentially loaded into the vertically aligned holding column. Distribution of the drug between the aqueous and octanol phases occurred by the oscillation movement of the syringe pump piston. Phase separation occurred due to the difference in densities. The liquid zones were then pushed into the detection flow cell. In this method, absorbance measurements in only one of the phase (octanol or aqueous) were employed, which together with the volumes of the solvents and pure drug sample, allowed the calculation of the Pow. The developed system was applied to the determination of the Pow of some common drugs. The log (Pow) values agreed well with a batch method (R(2)=0.999) and literature (R(2)=0.997). Standard deviations for intra- and inter-day analyses were both less than 0.1log unit. This ZF system provides a robust and automated method for screening of Pow values in the drug discovery process.

A Simple and Rapid Method Based on Anti-aggregation of Silver Nanoparticles for Detection of Poly(diallyldimethylammonium chloride) in Tap Water

A simple and rapid method was developed for the detection of poly(diallyldimethylammonium chloride) (PDADMAC) using citrate-capped silver nanoparticles (AgNPs). Detection was based on anti-aggregation of AgNPs in phosphate buffer caused by PDADMAC. Due to its positive charges, PDADMAC was adsorbed onto AgNPs via electrostatic interaction with citrate, which resulted in the charges at the particle surfaces to become positive and caused repulsion among particles. Furthermore, long-chain PDADMAC provided steric hindrance. These two effects promoted the dispersion of AgNPs in the phosphate buffer. A change in the state of dispersion influenced the surface plasmon resonance (SPR) of AgNPs. Therefore, in this work, the concentration of PDADMAC was determined by monitoring changes in absorbance (at 396 nm) caused by SPR of AgNPs. Under optimal conditions, the calibration was linear over the range of 1 to 100 mg L(-1) with a detection limit of 0.7 mg L(-1). Satisfactory precision was obtained (RSD = 2.8%). This method was successfully applied to the determination of PDADMAC in tap water samples. The recoveries ranged from 86.0 - 107.5%.

Photoregulation of Gold Nanoparticles Stabilized in a Diacetylenic Nanocapsule

The results of releasing a drug in a burst are unpredictable and one of the inherent drawbacks of using nanocarriers. Here, photoresponsive cationic gold nanoparticles to stabilize diacetylenic nanocapsules enabling photoregulated release of payloads are reported. The fabrication of these nanocapsules relied on an electrostatic interaction of a negatively charged diacetylenic core and a positively charged gold nanoparticle shell. Gold nanoparticles with photoresponsive ligands on their surfaces act as both hydrophobic core stabilizers and gatekeepers of the nanocapsules, while their polydiacetylene cores serve as hydrophobic drug carriers that can be tuned using UV irradiation. The morphology of nanocapsules was analyzed using TEM and dynamic light scattering. The resultant nanocapsules had a spherical shape with an average diameter of 152.9 ± 6.7 nm. Upon UV irradiation, the nanocapsules lost their integrity and an encapsulated model compound was released through diffusion. The release of a hydrophobic molecule was irradiation time dependent and thereby controllable. This light-triggered release provides an alternative strategy for controlled drug delivery.