Judul: Penentuan simultan natrium benzoat dan kalium sorbat menggunakan spektrofotometri UV dengan pendekatan kalibrasi multivariat
Abstrak: Bahan pengawet seperti natrium benzoat dan kalium sorbat telah banyak digunakan pada makanan dan minuman. Pengukuran kadar natrium benzoat dan . kalium sorbat dapat menggunakan metode spektrofotometri, kromatografi gas, dan kromatografi cair kinerja tinggi (KCKT). Metode kombinasi antara spektrofotometri UV dengan kalibrasi multivariat dilakukan dengan pengukuran analat secara simultan menggunakan spektrofotometri ultraviolet (UV) dan data yang diperoleh akan diolah melalui pendekatan kalibrasi multivariat. Teknik analisis yang digunakan principle component regression (PCR) dan partial least square (PLS). Hasil yang diperoleh pada PCR dan PLS, menunjukkan penggunaan PLS lebih baik dibanding dengan PCR, karena nilai r' pada natrium benzoat sebesar 99.90% untuk PLS dan 99.50% untuk PCR. Selain itu, PLS memiliki nilai galat lebih kecil dibandingkan dengan PCR. Pada analisis sampel sintetik menunjukkan kedekatan antara pengukuran menggunakan spektrofotometer UV pendekatan kalibrasi multivariat dengan pengukuran mengunakan KCKT. Analisis sampel minuman menunjukkan hasil yang berbeda antara spektrofotometer UV dengan KCKT, sehingga pengukuran dengan spektrofotometer UV pendekatan kalibrasi multivariat belum dapat menentukan secara simultan kadar natrium benzoat dan kalium sorbat pada sampel minuman. Hal ini disebabkan adanya matriks-matriks lain yang dapat mengganggu pengukuran dan multikolinearitasnya tinggi yang tidak dapat diabaikan.
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Judul: Metode Penambahan Standar Titik-H untuk Penentuan Simultan Natrium Benzoat dan Kalium Sorbat
Abstrak: H-point standard addition method (HPSAM) can be used as a method of choice for the development of simultaneous determination of sodium benzoate and potassium sorbate concentrations because of its precision, accuracy, selectivity, and rapidity, in addition to its simplicity. HPSAM is based on twowavelength spectrophotometry and the standard addition method. Analyte concentrations to be determined were measured simultaneously using ultravioletvisible spectrophotometry at wavelength pairs selected; the standard calibration curve of interference is needed to calculate the concentration of interference. The data obtained were processed using a mathematical calculation. Potassium sorbate was selected as the analyte and sodium benzoate was chosen as interference because it showed better accuracy. Simultaneous determination of the concentration of sodium benzoate and potassium sorbate with HPSAM produced selected wavelength pairs at 212.2 and 233.4 nm. Sodium benzoate and potassium sorbate in some synthetic mixtures were determined simultaneously in the range of 4 and 1-1.5 mg/L, respectively, with good precision and accuracy.
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Judul: Posisi Filogenetik Kura-Kura Carettochelys Insculpta  (Reptillia: Testudinata)
Abstrak: Carettochelys insculpta is an endemic freshwater turtle of southern Papua and northern Australia. Phylogenetic position of this turtle is remain unresolved until now. Most of the research conducted show close relationships of C. insculpta and members of Trionychidae family. However, some of the research show distance between C. insculpta and members of Trionychidae family. This research is conducted to analyze phylogenetic relationship between C. insculpta and other members of Testudinata using 12S rRNA, 16S rRNA, and both gene as markers. DNA samples were obtained from three different organisms of C. insculpta. Two species used as outgroups were Alligator mississippiensis and Iguana iguana. Phylogenetic analysis was carried out using Neighbor-Joining method with Felsenstein 1981 (F81) modeltest. A polytomy tree of Testudinata was produced by using 12S rRNA gene. However, analysis using 16S rRNA and both genes as markers confirmed that C. insculpta was located between the Chelonidae and the Trionychidae family.
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