Liquid / Liquid Interface-Based Electrochemical Sensing of Ractopamine and Salbutamol

AbstractAn electrochemical sensor based on ion transfer across micro- and nano-liquid / liquid interfaces has been developed for the detection of protonated drugs, ractopamine (RacH+) and salbutamol (SalH+) via cyclic voltammetry (CV) and linear sweep stripping voltammetry (LSSV). These voltammetric methods enabled the detection and characterisation of the ionised drugs despite that they transferred at high applied potentials. The drugs’ thermodynamic and analytical parameters were determined. The limit of detection in the sub-μM range is suitable for applications to detection in real samples. Electrochemistry at the liquid / liquid interfaces was shown to be a viable technique for drug sensing

Finite element modelling for predicting the puncture responses in papayas

This study aims to develop a finite element (FE) model to determine the mechanical responses of Exotica papayas during puncture loads. The FE model of the puncture-test was developed using the ANSYS 19.1 software. The proposed framework combined the finite element method and statistical procedure to validate the simulation with the experimental results. Assuming the elastic-plastic behaviour of papaya, the mechanical properties were measured through tensile test and compression test for both skin and flesh. The geometrical models include a quarter solid of papaya that was subjected to a puncture test with a 2 mm diameter flat-end stainless-steel probe inserted into the fruit tissues at 0.5 mm/s, 1 mm/s, 1.5 mm/s, 2 mm/s, and 2.5 mm/s. The FE results showed good agreement with the experimental data, indicating that the proposed approach was reliable. The FE model was best predicted the bioyield force with the highest relative error of 14.46%. In conclusion, this study contributes to the usage of FE methods for predicting the puncture responses of any perishable fruit and agricultural products

Subminiature panel (SMA-P) coaxial sensor for the determination of moisture content of mango cv. Chok Anan

The research describes the development of a simple, cheap and efficient open-ended coaxial sensor for the determination of moisture content of Chok Anan mango during fruit ripening from week 5 to week 17. The sensor was a modification of a standard subminiature panel (SMA-P). The finite element method was used to calculate the numerical values of the reflection coefficient. The reflection coefficient of the sensor was measured using a Microwave Network Analyzer in the frequency range from 1 to 4 GHz. The actual moisture content was obtained using standard oven drying method. A calibration equation was obtained to predict moisture content from the measured reflection coefficient at 1 GHz with accuracy within 1.5%. The results indicate that the amount of m.c. in Chok Anan mango can be determined with excellent accuracy using a SMA-P coaxial sensor as an OEC sensor

Microwave technique for moisture content and pH determination during pre-harvest of mango cv. Chok Anan

The maturity of mango is usually assessed by the determination of its moisture content (m.c.), soluble solid content (SSC) and pH. However, these techniques are either time consuming, tedious or destructive. In this research, we extend the application of the open-ended coaxial probe technique to determine m.c. and pH of Chok Anan mango from its dielectric properties from week 5 to week 17 after anthesis. The effects of frequency and m.c. on the values of the dielectric constant and loss factor were also investigated. The critical frequency separating the different polarizations was found to be inversely proportional to m.c. Also, in this research we proposed a new classification of fruit ripeness related to the number of weeks after anthesis. The actual dielectric properties, m.c., SSC and pH of Chok Anan mango were measured using standard methods. Relationships were established between the dielectric constant, loss factor, critical frequency, pH and m.c. The accuracy for the determination of m.c. and pH using the coaxial probe was within 1.7% and 3.0%, respectively

The deacidification of pineapple juice using electrodialysis with monopolar ion exchange membranes

The objective of this research was to study the performance of the electrodialysis using monopolar ion exchange membranes for the deacidification of pineapple juice. Based on preliminary experimental data using citric acid solution, AFN monopolar anion exchange membrane was selected for the subsequent study of the deacidification of pineapple juice. Electrodialysis of pineapple juice resulted in the reduction of the conductivity and the total acidity in the diluted stream. The deacidification value was 27.53 %. Deacidification process unexpectedly decreased the pH value from 4.01 to 3.75. However the Brix values were essentially unchanged (from 10.50 to 10.17 % Brix). A slight fluctuation in sugar compositions during electrodialysis was observed after 80 minutes of the processing. The sugar analysis was carried out using High Performance Liquid Chromatography (HPLC). HPLC analysis also showed that citric acid and malic acid compositions were always higher in the concentrated stream as compared to the diluted stream. The elemental analysis of the pineapple juice indicated that the composition of magnesium, phosphorus and potassium were reduced in the diluted stream but increased in the concentrated stream. The results from sensory evaluation test showed a higher overall acceptance for the electrodialysed pineapple juice compared to the fresh juice. The values of the overall acceptance were 66.0 % and 56.0 %, respectively. The findings showed that electrodialysis offer a better processing route and produce a more acceptable product for the deacidification of pineapple juice

The preparation and electrochemical characterization of nanopore array membranes

This thesis aimed to examine the behaviour of nanoscale and microscale liquid interfaces for chemical detection. Nanoporous membranes were prepared by various methods and characterised by ion-transfer electrochemistry at the membrane-modified interfaces between two immiscible electrolyte solutions. The detection of model analytes and ionised drug substances indicate that these miniaturised interfaces provide viable platforms for the detection of ions of chemical and biochemical importance

Dielectric based measurement system for the determination of watermelon internal quality

A dielectric based measurement system was used in the determination of watermelon internal quality, focusing on maturity stage. This technique is based on microwave reflection measurement at watermelon surface using an open-ended coaxial probe with a microwave network analyzer operating in the frequency range from 1.0 to 8.5 GHz. The dielectric and physicochemical properties were measured during the fruit maturity stage from week 6 to 10. The effects of frequency and moisture content on the values of permittivity (dielectric constant, ɛ’ and dielectric loss, ɛ”) were investigated. Mass, volume and SSC values increased, while moisture content and density values decreased with maturity stage (time). Permittivity values decreased with maturity stage, in agreement with theory in which permittivity of moist materials is a function of moisture content, density and frequency. In addition, the dielectric constant at all maturity stages decreased with the increasing frequency suggesting watermelon ɛ’ followed the profile of water ɛ’. The dielectric loss decreased with frequency then increased slightly as frequency approached 8.5 GHz. The turning, known as critical frequency separates the bound and free water molecules. This technique showed potential to determine moisture content, then maturity stage from its dielectric properties

Study of machines performance in producing different sizes of grated sago

Sago starch is a product from sago palm. In order to extract the sago starch, certain process is needed to break the bonding of the pith either mechanically or manually by grating the pith into small sizes. Water is widely used as a solvent medium in the extraction process of sago starch. The more refined that grated sago, the more sago starch can be dissolved from the grated sago. Different machines were used to produce grated sago for machine capability test. The machines are handheld chainsaw, coconut husk decorticator, commercial coconut grater and in-house roller grating prototype. Sago palm trunk was cut into three parts with length of 50 cm long each. The outer layer of each sago palm trunks was peeled off and split into 8 pieces. All sago trunks were grated using four different machines as stated above. Each 100 gram of the grated sago trunk produced by each machine were sifted according to the grading size of 2.80 mm, 2.00 mm, 1.00 mm, 0.85 mm and 0.425 mm. The weights of sago starch from the sieving process were recorded according to their respected grading size. Based on results of the sieve experiments, the most finest grated sago trunk was produced from the handheld chainsaw with a weight percentage ratio of 13.028% (X < 0.3 mm), 10.682% (0.3 ≤ X < 0.425 mm), 28.361% (0.425 ≤ X <0.85 mm), 28.821% (0.85 ≤ X <1.0 mm), 4.728% (1.0 ≤ X <2.0 mm), 7.877% (2.0 ≤ X <2.8 mm), and 4.868% (X ≥2.8 mm) where X value refer to sieve mesh size