Riyanto

Hydroquinone is a hazardous and toxic chemical often added to cosmetics due to bleaching properties. It is commonly analyzed in cosmetics using expensive and time-consuming instruments, showing the need for a cheap, fast, and sensitive hydroquinone electrochemical sensor. The performance of electrochemical sensor to detect hydroquinone is determined by the working electrode. Therefore, this study aimed to explore the synthesis of Au-Pd-NPs working electrode and application as electrochemical sensor of hydroquinone in cosmetics. Synthesis process was carried out by preparing Au-NPs using banana peel extract (Musa acuminata Colla) as a bioreductor, followed by adding H2PdCl4 solution. Au-NPs nanoparticle was confirmed using Ultraviolet-Visible spectrophotometer, which showed maximum wavelength of 550 nm. The indication of Au-Pd-NPs was shown by the peak at the same wavelength. The FTIR spectrum showed pectin which acted as a bioreductant agent in synthesis of nanoparticles. The results of the TEM image showed that Au-NPs had a spherical shape in the dark field with a diameter of 38.5 ± 3.3 nm and a Pd shell layer around the Au core in the bright field with a diameter of 12.4 ± 2.6 nm. The solid Au-Pd-NPs materials were made into a composite electrode by adding PVC and tetrahydrofuran as solvents. Electrochemical response of Au-Pd-NPs electrode was tested by cyclic voltammetry in ferricyanide and PBS solutions at pH 7.0. Based on CV in the ferricyanide system, it shows that Au-Pd-NPs electrode produces peak oxidation and reduction currents ten times higher than Au-NPs. These data indicate that Au-Pd-NPs are more reactive and sensitive than Au-NPs electrodes. The Au-Pd-NPs electrode was used to analysis the concentration of hydroquinone in cosmetics samples. Electrochemical response showed a linearity (R2) of 0.9935 in concentration range of 0-60 mM, containing 1.12% hydroquinone.

Dyes waste treatment is carried out using the coagulation method with Chemical Oxygen Demand (COD) analysis parameters. This analysis aims to determine the opti Dyes waste treatment is carried out using the coagulation method with Chemical Oxygen Demand (COD) analysis parameters. This analysis aims to determine the opti

The direct use of essential oil has several drawbacks, including being uneconomical, less effective, and has high volatility. The synthesis of silver nanopartic The direct use of essential oil has several drawbacks, including being uneconomical, less effective, and has high volatility. The synthesis of silver nanopartic

Demand for nutmeg essential oil in Indonesia and the world is increasing. Nutmeg essential oil is obtained from young nutmeg seeds extracted by water steam distillation (WSD). The weakness of the extraction process with WSD is the long distillation time (24 hours), wasteful of fuel, wasteful of manpower, produces polluting gases which damage the environment and requires a lot of water as a coolant. The purpose of this study was to compare the WSD and SCFE methods for extracting nutmeg essential oil. The research was conducted by extracting nutmeg essential oil using two methods are WSD and SCFE. The results showed that the chemical composition of the nutmeg essential oil produced by the two methods was almost similar. Nutmeg essential oil produced by both methods shows the same characterization. The yield between the two methods is almost the same, in the range of 10-12% using extraction time 15-60 minutes. The SCFE method has advantages over WSD are a faster extraction time, does not require heating materials and CO2 gas can be reused. In conclusion, SCFE is an alternative method to increase the production of nutmeg oil.

Disinfection of coliform and E. Coli in water has been performed by electrolysis using carbon electrodes. Carbon electrodes were used as an anode and cathode with a purity of 98.31% based on SEM-EDS analysis. This study was conducted using electrolysis powered by electric field using carbon electrode as the anode and cathode. Electrolysis method was carried out using variations of time (30, 60, 90, 120 minutes at a voltage of 5 V) and voltage (5, 10, 15, 20 V for 30 minutes) to determine the effect of the disinfection of the bacteria. The results showed the number of coliform and E. coli in water before and after electrolysis was 190 and 22 MPN/100 mL, respectively. The standards quality of drinking water No. 492/Menkes/Per/IV/2010 requires the zero content of coliform and E. Coli. Electrolysis with the variation of time and potential can reduce the number of coliforms and E. Coli but was not in accordance with the standards. The effect of hydrogen peroxide (H₂O₂) to the electrochemical disinfection was determined using UV-Vis spectrophotometer. The levels of H₂O₂ formed increased as soon after the duration of electrolysis voltage but was not a significant influence to the mortality of coliform and E.coli.

The effect of treatment with activated carbon to the metal content in the reuse of lubricating oil waste has been done. Waste lubricating oil has treatment using 1-butanol and KOH as a solvent and coagulant. The research studies of the effect of activated carbon to the metals are Pb, Cr, Ca, Mg and Fe in lubrication oil waste after treatment. Waste lubricating oil treatment by the adsorption method using activated carbon with various weight are 0,5; 1,0; and 1,5 g. The metal concentrate was analysis after and before treatment using Atomic Adsorption Spectrophotometer (AAS). The analysis result shown the best weight of activated carbon for decreased of metals contains in lubricating oil waste is 1.5 g. Metal concentration of Pb, Cr, Ca, Mg and Fe in lubricating oil waste before treatment are 181.0002, 10.7198, 1019.0220, 325.8788 and 365.1329 mg/L (ppm), respectively. Metal concentration of Pb, Cr, Ca, Mg and Fe in lubricating oil waste after treatment are 47.5670, not detection, 2.6871, 44.3251 and 222.043 mg/L (ppm), respectively. Base on ASTM D5185 standard shown the Ca, Mg and Cr metals concentration according to the new lubricating oil quality standard. Pb and Fe metals concentration after process are still above the new lubricating oil quality standard. As a conclusion is activated carbon is a good material for treatment of waste lubricating oil, especially to reduce metal concentrations.

There is a significant number of unpublished research by university lecturers and students about Gorontalo's local medicinal plants that have contributed to the insufficiency of information to the society regarding the benefits of local medicinal plants. Moreover, the public lacks digital backup and documentation of the medicinal plants referred. This research aims to create a web database of Gorontalo's local medicinal plant, by comprising waterfall method of software engineering approach. The waterfall method involves four steps. The first step is system requirement analysis through preliminary study and observation based on field study and library research. The second is system design, by context diagram and system architecture designs, i.e., use case diagram, class diagram, activity diagram, and database design. The third is coding using PHP programming language by OOP (object oriented programming) concept and MVC (model view controller) architecture. The last step is system test using the black-box testing method. The result shows that the web application designed is able to operate properly.