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This research has been carried out to compare complexometric titration methods and atomic absorption spectrophotometry in determining water hardness. The complexometric titration method has become the standard method of determining water hardness levels used in various references in several countries. The level of water hardness in several studies is known to be determined by atomic absorption spectrometry method. Both methods have good precision (%RSD ≤ 2%). Accuracy is calculated by repeatability system with the results of %recovery 92.57% for the titrimetric method and 106.99% for the spectrometric method. The results of the t-test for both methods stated that the t-count value (56.89) > t-table value (2.78). This shows that the two methods have significant differences. [ABSTRACT FROM AUTHOR]

The Covid-19 pandemic has shifted the format of the implementation of the teaching and learning process and has greatly impacted the fulfillment of competencies inherent in courses. This impact is very influential on practice courses, especially in the fulfillment of laboratory chemistry skills. Therefore, a simulator instrument was developed as a virtual laboratory in the implementation of online practice courses. The simulators developed are UV-Vis Spectrophotometer and Atomic Absorption Spectrophotometry (AAS). In the blended practice course format where 85% of the meetings are held online and 15% of the meetings are held offline, the simulator is used in the online practice course. The purpose of using the simulator is to improve students' skills in operating the instrument. The results of the survey of student perceptions of the use of the simulator stated that the majority of respondents strongly agreed or agreed with the ease of downloading the simulator, the ease of operating the simulator, the use of the simulator was very helpful in operating the instrument in the laboratory and the time spent completing the simulator was comparable to a traditional laboratory. The survey results also state that in the teaching and learning process, the majority of respondents also strongly agree or agree that experiments strengthen theory, experiments help in understanding concepts, the material provided helps in competency testing and online practice course help in understanding concepts such as traditional practice course. [ABSTRACT FROM AUTHOR]

Validation of the method of determining ascorbic acid by UV-Vis spectrophotometry in packaged drinks has been carried out with variations in the calibration curve range. The calibration curve was made into three variations, low range (between 0-3 ppm), medium range (between 0-20 ppm), and high range (between 0-25 ppm). The validation parameters analyzed were linearity, Limit of detection (LoD), Limit of Quantification (LoQ), precision, accuracy, and measurement uncertainty. The selection of the calibration curve range may affect the test results. The lowest linearity value is obtained in the low calibration curve range because some concentration points are lower than LOD. The value of precision and accuracy in the low range is also the lowest, while measurement uncertainty is the highest. This is because the sample concentration is outside the capacity of the calibration curve. Therefore, it is necessary to conduct a study related to the effect of the calibration curve on the method validation parameters before being used in testing, especially in laboratories that have received ISO 17025 accreditation. [ABSTRACT FROM AUTHOR]

Research has been conducted which were intended to study the feasibility of the method and the quality of Mentaya River water based on chemical oxygen demand (COD) and total solid suspended (TSS) parameters. The method used in this research was based on SNI 6989.73-2009 with the titrimetric for COD analysis and SNI 06-6989.3-2004 using the gravimetric for TSS analysis. The results of verification analysis for precision tests determine COD and TSS by 3.3% and 1.2%, respectively. Approval values for determining COD and TSS were 102% and 97.4%, respectively. Estimated values for COD and TSS from certified reference material (CRM) were 49.33 ± 0.1356 mg/L and 73.6 ± 0.3916 mg/L respectively. The COD results of the Mentaya River at Samuda, Ketapang and Kuayan sections were 34 mg/L, 123.2 mg/L and 8 mg/L respectively. Meanwhile, the TSS results at Samuda, Ketapang, and Kuayan locations were 98 mg/L, 10 mg/L and 32 mg/L respectively. The results of the verification method can be concluded that the method for determining COD and TSS meets the requirements so it can be used regularly in the laboratory. From the COD analysis, the quality of the Mentaya River at the Kuayan section below the quality standard of Indonesian Government Rules No 82 of 2001, while the Samuda and Ketapang sections exceeded the quality standard. The analysis result for TSS of the Mentaya river at Kuayan and Ketapang sections was below the quality standard and the Samuda section exceeded the quality standard of Indonesian Government Rules No 82 of 2001. [ABSTRACT FROM AUTHOR]

Determination of performance and uncertainty parameters from P2O5 analysis in inorganic fertilizer conducted by spectrophotometric UV-Visible has been done. This method was conducted in three stages those were preparation, testing and data processing. In the preparation stage, standard solution and reagent solution was made and for the testing stage, phosphorus standard and P2O5 samples were taken from inorganic fertilizer with linearity, precision (repeatability), accuracy (% recovery), limit of detection and limit of quantitation as variable analysis. The stage of data processing, the obtained results were processed statistically and compared with the acceptance requirements set by standard method. The coefficient determination (R²), precision, and accuracy respectively were 0.9999, 0.174%, and 100.58%, meanwhile LOD and LOQ were 1.653 mg/L and 5.508 mg/L. Based on the results can be concluded that the method analysis of P2O5 using spectrophotometry UV-Visible expressed good validity and can be applied as routine method at laboratory. [ABSTRACT FROM AUTHOR]

Comparison methods of C-organic determining in organic fertilizers by gravimetry (ash content) and UV-Vis spectrophotometry (Walkley & Black) had been performed. The difference between the two methods was seen from the validation parameters of each method. This research used precision, homogeneity, stability test, control chart and measurement uncertainty as parameter of validation method. The result of method validation indicates that both methods are not precision, but have homogeneous results. The stability test showed that C-organic analysis by gravimetry had stable results while in the UV-Vis spectrophotometry method, the results were unstable. Control chart analysis showed the results of C-organic analysis in a organic fertilizer with gravimetry method statistically controlled, while the Corganic analysis of glucose solution as standard by UV-Vis spectrophotometry method was uncontrolled. The measured uncertainty value of the gravimetry method of 0.0041% is much smaller than the UV-Vis spectrophotometry method of 2.1529%. The average percentage of C-organic content obtained from the gravimetry method was 18.654%, while the average percentage of C-organic content produced using UV-Vis spectrophotometry method was 8.674%. These results indicated that both methods are significantly different. [ABSTRACT FROM AUTHOR]

Hydrotalcite materials was synthesized by using Cetyltrimethyl Ammonium Bromide (CTAB) and Mg/Al layered double hydroxide with ratio molar 3:1. Synthesis of CTAB-Mg/Al hydrotalcite was carried out using ex situ coprecipitation method at pH 10±0.5. Removal of phenol was optimum at medium pH 6 and it had optimum contact time in 300 min. It followed pseudo second order with adsorption rate constant was 1.15∙10-4 mM-1·min-1. The maximum adsorption capacities obtained from the Langmuir model was 35.71 mg·g-1 at room temperature. [ABSTRACT FROM AUTHOR]

Borax has been found in food products i.e. on the Indonesian Tofu that is often consumed by people. Generally, the identification of borax in food products hard to do by the public. Indicators of natural materials will allow the public to identify the presence of borax in food easier. Qualitative test for borax on Indonesian Tofu showed purple cabbage and sappanwood are the effective natural indicators. The result of determining borax on Indonesian Tofu indicated natural indicator from purple cabbage had the smallest correction factor (with conventional indicators PP) about 4.8%. The results of the validation method for purple cabbage indicator in acid-base titration showed that the purple cabbage indicator is homogenous but unstable. The natural indicators of purple cabbage could not be used again after three days of extraction time based on the results of control chart. [ABSTRACT FROM AUTHOR]

This research concerns with the development of natural material i.e. natural zeolite. Natural zeolite were modified by surfactant treatment. Material modification has been done using cetyltrimethyllammonium bromide as cationic surfactant for mesopore template. The physicochemical characters of natural material modified and unmodified was investigated by using XRD, FTIR, nitrogen physisorption, and SEM-EDX. The XRD was used to show crystallinity structure of natural material modified and unmodified. Surfactant treatment caused decreasing crystallinity of natural zeolite. The FTIR spectra showed characteristic peaks for natural zeolite modified and unmodified, the bands around 3400-3500 cm-1 and 1635-1641 cm-1 correspond to adsorbed water and bands around finger print area were characteristic for silica and alumina. Meanwhile physisorption nitrogen profiles gave information that the pore modification by surfactant. The morphologies of natural material modified and unmodified as well as chemical composition of the particles were shown by SEM-EDX. The usage of modified material decrease acidity number into 19.47% than unmodified material, which is 7,62%. The GC analysis showed that percentage of patchouli alcohol increases and new peaks were not identified indicated there was not any reaction appeared. [ABSTRACT FROM AUTHOR]

Synthesis, characterization, and application of phenylamine modified montmorillonite have been studied. Preparation of phenylamine modified montmorillonite was conducted by intercalation process using simple amine compound. The changes in physical and chemical properties were observed through the crystal structure, functional groups and acidity as well as the application as an adsorbent for phenolic compound. The diffractogram showed characteristic basal spacing of montmorillonite at 2θ = 7.0710° and 19.8856°, also peaks with sharp intense around 20- 30° were 2θ = 28.6181° and 35.0112°. The reflection pattern of phenylamine modified montmorillonite exhibited the shifting of d001 basal spacing at 2θ = 7.0710° into 7.1624° that implied the phenylamine was attached to the surface of montmorillonite. The spectra of FTIR gave the difference of wave number for –OH stretching, -OH bending also Mg-OAl vibration that distinguished between natural montmorillonite and prepared material. The prepared material has lower acidity value and different surface characters which confirmed by gravimetric and infrared spectrum. The phenolic adsorption using prepared material gave maximum pH at 5 and optimum contact time around 2 hours with adsorption capacity was 24.48%. [ABSTRACT FROM AUTHOR]