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: Lejeuneaceae Subfamily Ptychanthoideae (Hepaticae) in  West Java
Abstrak: Subfamily Ptychanthoideae of the family Lejeuneaceae (Hepaticae) in West Java is still poorly known. Publications on this subfamily are out of dated and written in the 19th or early of 20th century. The last taxonomic treatment of Ptychanthoideae of West Java was in 1933, many species names have changed since then. Studies on Ptychanthoideae of West Java are urgently needed. Studies on the Ptychanthoideae were based on the specimens collected from West Java. A total number of 361 of specimens deposited in the Herbarium Bogoriense (BO), Herbarium Biotrop (BIOT), Gottingen Herbarium (GOET) and Bangi Herbarium (UKMB) were examined, those are old and several recent specimens collected in West Java. Recent collections were made from Telaga Warna, Ciater, Gunung Halimun Salak National Park, Cibodas Botanical Garden, Bodogol Education Center and Conservation (Gunung Gede Pangrango National Park), University of Indonesia Campus Depok, including several collections from Banten Province. Twenty four species of Lejeuneaceae subfamily Ptychanthoideae are known from West Java, belonging to 8 genera namely Acrolejeunea (Spruce) Schiffn. (2 species), Archilejeunea (Spruce) Schiffn. (1 species), Lopholejeunea (Spruce) Schiffn. (10 species), Mastigolejeunea (Spruce) Schiffn. (3 species), Ptychanthus Nees (1 species), Schiffneriolejeunea Verd. (1 species), Spruceanthus Verd. (2 species) and Thysananthus Lindenb. (4 species). Two new records of Ptychanthoideae: Mastigolejeunea indica Steph. and Thysananthus minor Verdoorn are reported for Java. A determination key to the species is presented including their descriptions and illustrations.
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