JKPK (Jurnal Kimia dan Pendidikan Kimia)
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Comparative Analysis of Caffeine Content in Cold and Hot Brewed Robusta Coffee Using High-Performance Liquid Chromatography (HPLC)
Full text linkCoffee is one of the most popular beverages globally, cherished for its unique taste, aroma, and the stimulating effects of its caffeine content. The proliferation of creative coffee shops has introduced various new methods for enjoying coffee, including cold and hot brew techniques. These processing techniques can significantly influence the physicochemical characteristics of coffee, particularly its caffeine content. This study compares the caffeine content in Robusta coffee using cold and hot brewing techniques. The hot brew coffee was prepared using water at approximately 96°C with a French press for six minutes. In contrast, the cold brew method involved brewing with water at room temperature (20-25°C) using a French press, followed by storage for 12 hours in a refrigerator (2-8°C). Qualitative analysis involved examining the color reaction, while quantitative analysis was conducted using High-Performance Liquid Chromatography (HPLC). HPLC is a highly accurate method that is extensively used in the food and pharmaceutical industries. The results indicated that the caffeine content in cold-brewed Robusta coffee was significantly higher, with a concentration of 44.63 μg/mL ± 0.199% and a Relative Standard Deviation (RSD) of 0.4459%. Conversely, hot-brewed coffee showed a caffeine concentration of 23.96 μg/mL ± 0.278%, with an RSD of 1.1602%. The parametric Analysis of Variance (ANOVA) revealed a significance value of 0.000 (p < 0.05), indicating a significant difference in caffeine levels between hot-brewed and cold-brewed coffee. These findings suggest that the choice of Robusta coffee processing technique can be crucial for individuals with specific health conditions seeking to manage their caffeine intake
Synthesis of Polystyrene Fiber Membranes Prepared by Electrospinning: Effect of AgNO3 on the Microstructure
Full text linkPolystyrene (PS) is commonly employed in insulation, packaging, filters, and medical equipment, with recent studies exploring its potential in fiber membrane production. The electrospinning technique is discussed to synthesize PS fiber membranes with high porosity and controllable diameter. Additionally, incorporating silver nitrate into PS composite fibers is explored for enhanced functionalities such as catalytic activity, high electrical conductivity, and antibacterial activity. However, PS composite fiber membranes with silver nitrate (AgNO3) metal variations are rarely observed. This research aims to modify the microstructure of PS fiber membranes produced using electrospinning by adding silver nitrate (AgNO3) with varying concentrations. PS-Ag fiber membranes are produced using N,N-dimethylformamide (DMF) solvent, which serves as a solvent and a reducing agent for Ag. The results show that the effect of Ag affected the diameter of the PS-Ag fiber membrane, with an average diameter of around 3.67 - 6.93 micrometers. Degradation occurred in these samples at a strong broadening peak near ~1300 cm-1 until ~1600 cm-1 from the Raman results. The FTIR results show that the wavelength of ~3500 cm-1 indicated the presence of OH. The presence of OH indicates that the PS-Ag fiber membrane has the potential for water filtration applicatio
Non-Enzymatic Detection of Glucose and Ketones in Urine using Paper-Based Analytical Devices
Full text linkDiabetes, driven by unbalanced diets and unhealthy lifestyles, is highly prevalent. In Indonesia, its prevalence is projected to reach 28.6 million by 2045. Microfluidic paper-based analytical devices (μPADs) are paper-based analytical tools that use hydrophilic paper for measurement and hydrophobic barriers to control fluid flow. This research aims to develop a non-enzymatic method for detecting glucose and ketones in artificial urine using S2Z-μPADs. The fabrication of S2Z-μPADs involves printing the design on Whatman No. 1 paper using wax printing and applying silver nanoparticles for glucose detection and the Schiff base reaction for ketone detection. The results show that the optimum condition for glucose detection is achieved with an AgNO3 concentration of 500 mM. A NaOH concentration of 10 M. Acetoacetate detection is optimized with a glycine concentration of 1 M, sodium nitroprusside concentration of 15%, NaOH concentration of 1 M, a drying time of 8 minutes, and a reaction time of 10 minutes. Validation results demonstrate good linearity for glucose (R² = 0.9821) and ketones (R² = 0.995). High precision was achieved with relative standard deviation (RSD) values of 3.792% for glucose and 1.482% for ketones. The obtained limits of detection (LOD) and limits of quantification (LOQ) indicate that the developed S2Z-μPADs can differentiate between each category of diabetes. The accuracy of glucose and ketone detection ranges from 87.463% to 97.374%. The high accuracy of the μPADs highlights their potential for reliable diabetes management and effective disease monitoring
Green Synthesis of SnO2 Nanocrystals Using Garcinia Mangostana L Fruit Peels Extract as Natural Capping Agent
Full text linkThe hydrothermal synthesis of SnO2 nanocrystals at a relatively low-temperature range of 95-100 °C was successfully conducted utilising Garcinia Mangostana L fruit peel extract as a natural capping agent. Characterisation of the synthesised SnO2 nanocrystals was performed using an X-ray diffractometer (XRD) for phase analysis and determination of crystallite size and a Scanning Electron Microscope (SEM) for morphology analysis. XRD analysis revealed the formation of phase-pure SnO2 nanocrystals, with distinct peaks at angles (2θ) of 26.01°, 33.89°, and 51.70° corresponding to miller indices (110), (101), and (211) as per JSPDS standard data. The absence of impurity peaks in the XRD pattern indicated the high purity of the synthesised SnO2 nanocrystals. SEM images exhibited differences in the size and morphology of the synthesised SnO2 nanocrystals with and without the extract. Specifically, the presence of the fruit peel extract led to a reduction in aggregate formation and inhibited crystal growth, resulting in smaller aggregates. These findings highlight the significant impact of Garcinia Mangostana L fruit peel extract on the hydrothermal synthesis of SnO2 nanocrystals with varied sizes and morphologies
The Project-Based Learning’s Key Characteristic: How STEAM Sparks Creativity and Curiosity in Cultivating Daphnia sp. Acid-Based Chemistry
Full text linkThis study explores the integration of STEAM (Science, Technology, Engineering, Arts, Mathematics) with Project-Based Learning (PBL) to enhance creativity and curiosity in high school students within the context of chemistry education. The research involved 11th-grade students designing a Daphnia sp. cultivation pond, a project aimed at applying interdisciplinary knowledge and fostering essential 21st-century skills. Using a qualitative case study approach, data were collected through questionnaires, interviews, and student worksheets. The study focuses on an in-depth analysis of six key characteristics of STEM-PBL including driving questions, learning goals, scientific practice, collaboration, using a technological tool, and creating an artifact—creativity and curiosity as key outcomes. The results indicate a significant positive correlation between creativity and students' cognitive performance, highlighting the effectiveness of the STEAM-PBL approach in promoting innovative thinking and problem-solving skills. However, the study found no significant relationship between curiosity and cognitive scores, suggesting that curiosity may develop independently of direct academic outcomes within this framework. Despite these positive findings, the study also identified challenges such as limited resources, insufficient teacher training, and resistance to traditional educational methods. The study recommends further exploration into the long-term impacts of STEAM-PBL and its applicability across different educational contexts
Utilization of Xylanase Enzymes Derived from Cassava in the Eco-Friendly Biobleaching of Pulp
Full text linkThe demand for paper has been increasing over time, leading to the pulp and paper industry becoming one of the largest contributors to global carbon emissions due to the chlorine-based bleaching process, particularly in Indonesia. An alternative to minimize chlorine usage involves using xylanase enzymes as part of the bleaching sequence. Xylanase can be produced from agricultural waste, including cassava residue, which contains a significant concentration of xylanase, approximately 21.3%. However, it still needs to be utilized in Indonesia. Therefore, this study aims to explore the production of xylanase enzymes from cassava residue and assess its effectiveness in the biobleaching process of pulp. The research methodology includes the production phase of xylanase enzymes by Aspergillus niger, chelating, bleaching sequence, bleaching, kappa number, and chemical saving assay. In the production of xylanase, the study determined that xylanase exhibits optimal activity under specific conditions, notably at a pH of 6 and a temperature of 60°C. Under these parameters, the enzymatic activity reached a level of 0.4986 U/mg protein. During the bleaching sequence, xylanase was used with doses of 0.3, 0.5, 0.7, 0.8, and 1 L/T pulp at 40, 45, 50, 55, 60, 65, and 70°C for 60 minutes. Following this process, bleaching was conducted at 65°C for 70 minutes, extraction at 80°C for 90 minutes, and a second bleaching phase. Subsequently, a kappa number test was performed, revealing the best kappa value at 60°C with a xylanase dose of 0.5 L/T pulp, reducing from an initial kappa number of 9 to 4.04. Additionally, under these conditions and dosage, xylanase enzymes could save approximately 23.67% in chlorine usag
Development of a Problem-Based Learning-Oriented Interactive E-worksheet on Chemical Equilibrium to Enhance Students' Scientific Literacy Skills
Full text linkIndonesian students' scientific literacy scores decreased by 13 points from PISA 2018, indicating that the scientific literacy skills of participants in Indonesia are low. One area of concern is students' understanding of chemical equilibrium, which is essential because it is a prerequisite for grasping subsequent materials. This study aims to assess the feasibility of interactive e-worksheets as a learning medium for chemical equilibrium material in terms of validity, practicality, and effectiveness. According to Thiagarajan, the research employs the 4-D research and development model, which includes Defining, Designing, Developing, and Disseminating but is limited to the development stage. A limited trial was conducted using a one-group pretest-posttest research design. Validation results show that the interactive e-worksheet is valid with a mode value of 4 in content, presentation, language, and design. The validity test results yielded a mode value 4 for both content and construct validity. The practicality test results indicated a high percentage of practicality with very practical criteria. The effectiveness test, analysed using n-gain, showed an n-gain value of 0.78 with high criteria, and the paired sample t-test results indicated a P-value of 0.000, confirming that the post-test scores were significantly higher than the pretest scores. Thus, the PBL-oriented Interactive e-worksheet can improve students' scientific literacy skills
Synthesis of Poly Acrylic Acid (PAA) Modified Silver Nanoparticles, Using Trisodium Citrate for Heavy Metal Detection
Full text linkTherefore, this project was to prepare and characterize silver nanoparticles (AgNPs) and study their application for colorimetric detection of heavy metal ions. AgNPs are synthesized by a bottom-up method in which AgNO3 serves as the precursor, which is then reduced using trisodium citrate and stabilized by 1 vol.% polyacrylic acid (PAA). Trisodium citrate facilitates the reduction of Ag+ ions due to its negatively charged carboxylic groups, whereas PAA enhances stability and selectivity. Under the best reaction parameters condition, AgNPs produced brown-yellow colloids with a Surface Plasmon Resonance (SPR) peak of 403 nm. A particle size analysis showed an average particle diameter of 29.9 nm, with a standard deviation σ of 0.482. Fourier Transform Infrared Spectroscopy (FTIR) analysis confirmed that hydroxyl groups -OH and carbonyl groups C=O play a role in reducing Ag+ ions. Because they are highly active, AgNPs can respond to Hg2+ in tests, marking the color change from brown-yellow to transparent white within about one minute. Methods testing for validation of linearity revealed an R2 = 0.9985, and a LOD and LOQ are ca. 0.074 ppm and 0.224 ppm, respectively. At 700 ppm Hg2+, the selectivity was good. These results demonstrate that AgNPs are sensitive and efficient sensors of Hg2+ ions and indicate how to find promising new ways to detect heavy metals in environmental monitoring
MES surfactant-based liquid soaps added with eco-enzyme and pandan wangi leaf extract (Pandanus amaryllifolius Roxb) on physical-chemistry properties, and antibacterial activity,"
Full text linkThe growing demand for liquid soap has spurred innovations in soap formulations, particularly using methyl ester sulfonate (MES) as a surfactant base combined with natural ingredients like eco-enzyme and fragrant pandan leaf extract. This study aimed to determine the optimal liquid soap formulation by evaluating physicochemical properties and antibacterial activity against Staphylococcus aureus. The research was conducted in two stages. First, liquid soap was produced at different temperatures (20°C, 50°C, and 100°C) to identify the optimal temperature based on maximum lipase activity. In the second stage, various formulations were prepared, incorporating eco-enzyme and fragrant pandan leaf extract at the identified optimal temperature. The six formulations tested were: F1 (MES-based soap), F2 (20% eco-enzyme), F3 (15% eco-enzyme and 5% fragrant pandan leaf extract), F4 (10% eco-enzyme and 10% fragrant pandan leaf extract), F5 (5% eco-enzyme and 15% fragrant pandan leaf extract), and F6 (20% fragrant pandan leaf extract). The formulations were assessed for lipase activity, pH, density, and viscosity. The most effective formulation was further tested for antibacterial activity using the disc diffusion method with six treatments, including MES-based soap and controls. Statistical analysis using One-Way ANOVA revealed that adding eco-enzyme and fragrant pandan leaf extract significantly affected the soap's properties. The optimal formulation, containing 5% eco-enzyme and 15% fragrant pandan leaf extract, exhibited a lipase activity of 15,778 U/mL, a pH of 5.02, a density of 1.06 g/mL, a viscosity of 3.59 cP, and an antibacterial zone of 37.22 mm, making it the best candidate for further developmen
Impacts of The POGIL Learning Model Combined With a SETS Approach on Chemical Literacy and Science Process Skills in The Context of Buffer Solutions
Full text linkThis study evaluates the impact of the Process Oriented Guided Inquiry Learning (POGIL) model combined with a Science-Technology-Society-Environment (SETS) approach on chemical literacy and science process skills within buffer solutions. Employing a quasi-experimental design with a nonequivalent control group, the research involved 71 students divided into experimental and control groups. Cluster random sampling was utilized for participant selection, and Multivariate Analysis of Variance (MANOVA) was applied to test the hypotheses. The findings reveal a significant effect of the POGIL learning model integrated with a SETS approach on simultaneously enhancing students' chemical literacy and science process skills. This outcome is substantiated by the MANOVA results, which indicate a significance level of 0.000, falling below the threshold of 0.05, thereby leading to the rejection of the null hypothesis (H0). Notably, the experimental group demonstrated significant improvements compared to the control group. Chemical literacy in the experimental group reached 79.90%, significantly higher than the 62.53% observed in the control group. Additionally, the N-gain scores for the experimental and control groups were 0.70 and 0.32, respectively, categorized as high and medium. Furthermore, the percentages of science process skills were 91.61% in the experimental group and 82.37% in the control group, both in the very good category. These results underscore the effectiveness of combining POGIL with a SETS approach in elevating chemical literacy and science process skills, suggesting this method is a potent educational tool in chemical education