Natchanon Amornthammarong

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.

Liquid-waveguide spectrophotometric measurement of low silicate in natural waters.

This paper describes a robust, sensitive method for measurement of low silicate in natural water. The method is based on the reaction of silicate with ammonium molybdate to form a yellow silicomolybdate complex, which is then reduced to silicomolybdenum blue by ascorbic acid. This method shows no refractive index effect and a small salinity effect that can be corrected for seawater samples. It was found that the use of poly-vinyl alcohol can prevent the precipitation formation in the ammonium molybdate solution and improve the stability of the silicomolybdenum blue complex. The sensitivity of this method is substantially enhanced by using a liquid-waveguide capillary cell. The detection limit is 0.1 microM, and working range is 0.1-10 microM for using 2-m liquid-waveguide capillary cell (LWCC). The method can be used for both freshwater and seawater samples and has been used to study the distribution of silicate in surface seawater of Gulf Stream in Florida straight.

Method development based on all injection analysis for the determination of phosphorus in soil and sediment extracts

In this work, we have modified the technique of all injection analysis (AIA) by changing the position of the detector. The detection is then located as a part of the circulatory loop. With this new detector position, we could monitor for many numbers of circulation. The sensitivity was improved by using the cumulative signal data obtained when the number of circulation rounds was increased. The dilution effect using this new detector location was also less than that with the previous system. We employed a four-channel peristaltic pump to aspirate four types of liquids into the system together at one time. The AIA method was then developed for determination of phosphorus in soils and sediment extracts. The method was optimized for the new harmonized scheme of extraction that has been developed by the European Commission.

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.

A simple, effective mixing chamber used in conjunction with a syringe pump for flow analysis.

A simple, effective mixing chamber used in conjunction with a syringe pump for flow analysis is described and evaluated. A mixing chamber was constructed using a conventional 5mL pipette tip and its performance compared with a widely used mixing coil. The results demonstrate that the mixing coil does not rapidly and completely mix solutions. Utilizing a configuration that reversed solution positions in the chamber with each mixing cycle, the proposed mixing chamber achieved complete mixing in a significantly shorter time than the mixing coil. The influence of injected sample volume on absorbance signals was evaluated by calculating an S(1/2) value for the system. As tested with a minimal rinse, the system has no discernable carryover. Testing this new approach in our previously described silicate measurement system resulted in a more than twofold improvement in sensitivity.

Low cost telemetry with PC sound card for chemical analysis applications.

This work describes the development of a telemetric system in conjunction with a computer sound card for recording of signals. For signal transmission, a transmission wireless microphone was utilized, making the telemeter compatible with the sound card normally equipped inside a personal computer. The developed telemeter is a low-cost apparatus capable of remote monitoring. With the sampling rate of 10Hz, 100% accuracy was obtained up to a distance of 30m. The precision was good (%RSD=0.03-0.09), with relatively low noise. The effective signal range was from 0 to 2V, with approximately 1100 working steps (greater than 10bit A/D). The telemetric system was shown to be suitable for wireless recording of outputs from spectrophotometer and pH meter. Potential applications in chemical analysis were demonstrated.