Detection of free fatty acid in crude palm oil

Palm oil quality and price is dependent on the free fatty acids (FFA) content in palm oil. High content of free fatty acids in palm oil affect the quality of palm oil and leads to various health and environmental issues. The maximum free fatty acids content set by the Palm Oil Refiners Association of Malaysia in crude palm oil is 5 % and < 0.1 % in refined bleached deodorized oil. Due to the high demand in palm oil industry market nowadays, various works has been done to improve the quality of palm oil including the determination and reduction of free fatty acids in palm oil. The traditional method for determination of free fatty acids in palm oil is through titration of the sample against potassium hydroxide in hot 2-propanol solutions by using phenolphthalein as indicator. Several other methods have also been reported on free fatty acids determination previously for example spectroscopic, chromatography and electrochemical technique. This paper reviews all methods reported for determination of free fatty acids in palm oil

Bio-based polycationic polyurethane as an ion-selective membrane for nitrate tapered optical fiber sensors

A novel bio-based polycationic polyurethane as an ion-selective membrane for nitrate sensing was successfully developed. In this work, the intermolecular interactions at active polymeric sites play a primary role in selective nitrate-ion detection. From the experiment, FTIR shows a significant shift from 1543 cm−1 to 1548 cm−1 in N-H bending, indicating that intermolecular interactions occur between the polycationic polyurethane and nitrate. AFM shows that the surface roughness of the polycationic polyurethane decreases from 95.7 nm to 12.2 nm after immersion in nitrate solution. Meanwhile, FESEM images show that the bright area, which represents the hard segment of polycationic polyurethane, decreases after immersion, indicating that the nitrate is interacting with the hard segment of the polycationic polyurethane via intermolecular interaction. Furthermore, EIS shows that the conductivity increases from 2.84 × 10−11 to 5.34 × 10−11 S cm−1 after ion exchange occurs between the iodide and nitrate on the polycationic polyurethane. To assess the sensing performance, the sensor probe is fabricated by coating the polycationic polyurethane thin film on the tapered region of an optical fiber. Rapid detection, good repeatability, and a sensitivity of 5.94 × 10−2µW/ppm are obtained for nitrate detection using the above bio-based-sensing material. The selectivity study also shows that the sensing material possesses high affinity toward the nitrate ion

Label-free detection of dissolved carbon dioxide utilizing multimode tapered optical fiber coated zinc oxide nanorice

A label-free detection for dissolved carbon dioxide (dCO 2 ) is developed using a tapered optical fiber sensor. The tapered region of the optical fiber is coated with the zinc oxide (ZnO) nanorice and used as a probe for dCO 2 sensing. The sensor probe was exposed to different concentrations of dCO 2 solution ranging from 10 to 100 ppm. ZnO nanorice can adsorb dCO 2 via strong hydrogen bonding due to the presence of plenty of oxygen atoms on its surface layer. The interaction between ZnO nanorice and dCO 2 changes the optical properties of the ZnO nanorice layer, resulting in the change in reflectance. From the experiment, the result shows that there is an improvement in the sensitivity of the sensor when higher concentration was used. A broad linear trend ranging from 0 to 60 ppm ( R2=0.972 ) is observed for the sensor probe that is coated with 1.0 M of ZnO nanorice compared with the 0.1 M and 0.5 M ZnO nanorice concentrations. The sensor sensitivity obtained is 0.008 mW/ppm. The sensor demonstrates a response and recovery time of 0.47 and 1.70 min, respectively. Good repeatability is obtained with the standard deviation in the range of 0.008–0.027. The average resolution calculated for this sensor is 4.595 ppm

Third-order nonlinearity with subradiance dark-state in ultra-strong excitons and surface plasmon coupling using self-antiaggregation organic dye

A strong coupling regime with dressed states is formed when a propagating surface plasmon (PSP) mode coherently exchanges energy with an ensemble of excitons at a rate faster than the system's losses. These states are superpositions of superradiance excitons and PSP modes, accompanied by remaining subradiance or 'dark' exciton states. Dark-states are ubiquitous, especially in disordered systems, and they rise in number as the number of excitons increases. Here, the ultra-strong coupling regime was experimentally observed with the coupling strength to bare energy as high as g/${E}_{exciton}\,$∼ 0.23 using a self-antiaggregation organic dye, BOBzBT2 in an Otto-SPR configuration. We show that the hybrid system of excitons in a nonlinear organic dye layer and a PSP mode can be described by employing dark-state in a theory of nonlinear third-order sum-frequency generation (TSFG). Close agreement between the theory and the experiment has been demonstrated. The study opens up a new perspective for establishing a relationship between the optical properties of a third-order nonlinear material and the extent of strong coupling

Essential oil from five alpinia species of Sarawak

Essential oils from five species of Alpinia were investigated for their chemical composition and biological activity against Artemia salina, Coptotermes sp and fungi species; Trametes Versicolor, Gloeophyllum Trabeum and Chaetomium. Essential oil was extracted by using hydrodistillation method and subsequently analyzed by using gas chromatography/flame ionization detector (GC/FID). The percentages of essential oil obtained from five Alpinia species ranged from 0.37% (v/w) to 2.56% (v/w). Generally, the highest value of 2.56% (v/w) was obtained from rhizome of A. latilabris, while the lowest yield obtained from stem of A. latilabris with the percentage of 0.37% (v/w). Leaves of A. amentaceae were rich in β-carene (87.33%) and ocimene (5.90%) while ethylpyrazine (50.67%) and nonane (35.10%) was the major compound in rhizome oil. The most abundant compound in A. aquatica (Campus) was β-bourbonene (16.83%) and hexanithiol (12.58%), from leaves oil and 2-dodecenal (38.26%) from rhizome oil. The major compound was found in the leaves of A. nieuenhuizii was β-pinene (36.35%) and 2-pentanol (22.02%) in rhizome oil. In the A. latilabris the major compound found in leaves oil was wine lactone (16.66%) and dimethyl pyrazine (16.43%), while in stem oil was ethylpyrazine (50.32%) and dimethyl pyrazine (26.22%) was found in rhizome oil. A. aquatica (Lawas) was found to be rich in 2-pentanol (58.99%) for leaves oil, furfuryl mercaptan (39.66%) for stem oil and 2-dodecenol (17.30%) for rhizome oil. The bioassay tests against A. salina for Alpinia sp. have not shown any biological activity. Termicidal test on Coptotermes sp showed that the leaves oil of A. aquatica (Lawas) gave significant value with the LC50 of 0.75%, while the rhizome oil of A. aquatica (Lawas) showed no significant value with the LC50 of 1.50%. The antifungal test on Alpinia sp. showed no biological activity

Sensitivity Enhancement of Pb(II) Ion Detection in Rivers Using SPR-Based Ag Metallic Layer Coated with Chitosan–Graphene Oxide Nanocomposite

The detection of Pb(II) ions in a river using the surface plasmon resonance (SPR)-based silver (Ag) thin film technique was successfully developed. Chitosan&ndash;graphene oxide (CS-GO) was coated on top of the Ag thin film surface and acted as the active sensing layer for Pb(II) ion detection. CS-GO was synthesized and characterized, and the physicochemical properties of this material were studied prior to integration with the SPR. In X-ray photoelectron spectroscopy (XPS), the appearance of the C=O, C&ndash;O, and O&ndash;H functional groups at 531.2 eV and 532.5 eV, respectively, confirms the success of CS-GO nanocomposite synthesis. A higher surface roughness of 31.04 nm was observed under atomic force microscopy (AFM) analysis for Ag/CS-GO thin film. The enhancement in thin film roughness indicates that more adsorption sites are available for Pb(II) ion binding. The SPR performance shows a good sensor sensitivity for Ag/CS-GO with 1.38&deg; ppm&minus;1 ranging from 0.01 to 5.00 ppm of standard Pb(II) solutions. At lower concentrations, a better detection accuracy was shown by SPR using Ag/CS-GO thin film compared to Ag/CS thin film. The SPR performance using Ag/CS-GO thin film was further evaluated with real water samples collected from rivers. The results are in agreement with those of standard Pb(II) ion solution, which were obtained at incidence angles of 80.00&deg; and 81.11&deg; for local and foreign rivers, respectively

Study on the spectrophotometric detection of free fatty acids in palm oil utilizing enzymatic reactions

In this paper, a comprehensive study has been made on the detection of free fatty acids (FFAs) in palm oil via an optical technique based on enzymatic aminolysis reactions. FFAs in crude palm oil (CPO) were converted into fatty hydroxamic acids (FHAs) in a biphasic lipid/aqueous medium in the presence of immobilized lipase. The colored compound formed after complexation between FHA and vanadium (V) ion solution was proportional to the FFA content in the CPO samples and was analyzed using a spectrophotometric method. In order to develop a rapid detection system, the parameters involved in the aminolysis process were studied. The utilization of immobilized lipase as catalyst during the aminolysis process offers simplicity in the product isolation and the possibility of conducting the process under extreme reaction conditions. A good agreement was found between the developed method using immobilized Thermomyces lanuginose lipase as catalyst for the aminolysis process and the Malaysian Palm Oil Board (MPOB) standard titration method (R2 = 0.9453)

Effect of Active Site Modification towards Performance Enhancement in Biopolymer κ-Carrageenan Derivatives

This research demonstrates a one-step modification process of biopolymer carrageenan active sites through functional group substitution in &kappa;-carrageenan structures. The modification process improves the electronegative properties of &kappa;-carrageenan derivatives, leading to enhancement of the material&rsquo;s performance. Synthesized succinyl &kappa;-carrageenan with a high degree of substitution provides more active sites for interaction with analytes. The FTIR analysis of succinyl &kappa;-carrageenan showed the presence of new peaks at 1068 cm&minus;1, 1218 cm&minus;1, and 1626 cm&minus;1 that corresponded to the vibrations of C&ndash;O and C=O from the carbonyl group. A new peak at 2.86 ppm in 1H NMR represented the methyl proton neighboring with C=O. The appearance of new peaks at 177.05 and 177.15 ppm in 13C NMR proves the substitution of the succinyl group in the &kappa;-carrageenan structure. The elemental analysis was carried out to calculate the degree of substitution with the highest value of 1.78 at 24 h of reaction. The XRD diffractogram of derivatives exhibited a higher degree of crystallinity compared to pristine &kappa;-carrageenan at 23.8% and 9.2%, respectively. Modification of &kappa;-carrageenan with a succinyl group improved its interaction with ions and the conductivity of the salt solution compared to its pristine form. This work has a high potential to be applied in various applications such as sensors, drug delivery, and polymer electrolytes

Gamma irradiated Py/PVA for GOx immobilization on tapered optical fiber for glucose biosensing

Tapered optical fiber coated with pyrrole/poly(vinyl alcohol)-glucose oxidase (Py/PVA-GOx) for glucose biosensing was successfully fabricated by radiation immobilization of GOx onto polymeric surfaces. Polymerization of pyrrole and PVA crosslinking was carried out by means of gamma irradiation. The nature of enzyme immobilization was studied by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy and atomic force microscopy. The observation of an absorption band at 1650 cm−1 and binding energy formed at 287.5 eV confirm the occurrence of GOx immobilization on the polymer matrix. An increase in film thickness is observed after irradiation, which confirms the entrapment of GOx into the Py/PVA polymer matrix. The peak to valley roughness for the irradiated Py/PVA-GOx reveals the intermolecular interaction between the polymers and enzyme. These characteristics are linked to the enzymatic reaction of the coated optical fiber towards the glucose concentration. The kinetic property of the GOx in the irradiated Py/PVA-GOx coated fiber was studied with a very low value obtained for the Michaelis-Menten constant, which contributes to improved adhesion and immobilization on the coated fiber. The response and sensitivity of the coated optical fiber were recorded as <0.31 μW and 8.7 × 10-3 μWmM-1, respectively. A selectivity study reveals that the irradiated fiber coated with Py/PVA-GOx is highly selective towards glucose