Desain dan Pengembangan Spektrofotometer Cahaya Tampak untuk Menentukan Absorbansi Maksimum dari Pewarna Makanan dan klorofil a Daun Bayam
DOI:
https://doi.org/10.21009/03.SNF2022.01.FA.08Abstract
Abstrak
Sebuah spektrofotometer cahaya tampak telah didesain dan dikembangkan dengan menggunakan LDR sebagai detektor cahaya. LED putih digunakan sebagai sumber cahaya. Sumber cahaya difilter terlebih dahulu dengan menggunakan kertas filter monokromatis dengan variasi warna ungu, merah, biru, hijau dan jingga. Sampel yang diujikan pada spektrometer berupa pewarna makanan (merah, jingga, hijau dan biru) serta klorofil a daun bayam. Persamaan Lambert Beer digunakan untuk mengukur nilai absorbansi dari sampel, dengan menghubungkannya ke tegangan keluaran rangkaian LDR. Tegangan keluaran yang digunakan pada perhitungan berupa tegangan keluaran sampel saat dikenai cahaya yang difilter, tegangan keluaran pelarut (air) dan tegangan keluaran pada keadaan tanpa cahaya. Setiap sampel memiliki nilai absorbansi yang bervariasi ketika disinari cahaya yang terfilter. Hasil penelitian mengindikasikan bahwa nilai absorbansi maksimum pada masing-masing pewarna makanan memberikan nilai akurasi yang sangat baik dimana sejalan dengan teori. Nilai absorbansi maksimum masing-masing pewarna makanan adalah : pewarna merah menyerap maksimum pada panjang gelombang warna hijau, pewarna biru pada warna jingga, pewarna jingga pada warna biru, pewarna hijau pada warna merah, dan klorofil a menyerap maksimum pada panjang gelombang warna ungu dan jingga.
Kata-kata kunci: Spektrofotometer, LED putih, LDR, Persamaan Lambert Beer
Abstract
A simple visible light spectrophotometer has been developed and designed using LDR as photodetetector. White LED was used as light source. The light source was filtered using monocrhomatic (violet, red, blue, green, yellow, and orange) filter paper. The spectrometer was tested in several sampels, such as food s (red, orange, green and blue) and chlorophyll a of spinach. The result of measurement were output voltage and the Absorbance of sample (A). And by using Lambert Beer equation, the absorbance which corresponds to the voltage output of samples was calculated. Not only samples voltage output but any other parameters such as the voltage of solvent (water) and zero condition (with no light) were also measured. They were needed to be put in the equation for finding the absorbance of samples. The result of research indicated that the maximum absorbance value of each sample agreed with the theory, so it can be concluded that the results had good accuration. The maximum absorbance that was obtain of each sample i.e : food colourings (red, blue, orange and green) each one of them absorbed green, orange, blue and red. And chloropyll absorbed violet and orange.
Keywords: spectrophotometer, white LED, LDR, Lambert Beer equation
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