Judul: Pengembangan Membran Elektrode Optik Selulosa Triasetat untuk Deteksi Besi.
Abstrak: Besi merupakan logam berat yang dapat membahayakan kesehatan manusia. Penelitian ini bertujuan membuat membran elektrode optik (optode) dari selulosa triasetat yang mengandung reagen selektif terhadap ion Fe(III). Optode dipreparasi dengan melarutkan selulosa triasetat (CTA) dalam kloroform dan ditambahkan campuran asetofenon-asam oleat, alikuot 336, dan ion tiosianat. Kinerja optode dievaluasi berdasarkan rentang kerja, limit deteksi dan limit kuantitasi, presisi, akurasi, selektivitas, dan stabilitas. Kinerja terbaik optode terjadi pada rentang kerja 0.1-5 mg/L dengan koefisien determinasi 0.9951, limit deteksi 0.09 mg/L, dan limit kuantitasi 0.29 mg/L. Nilai akurasi rata-rata 99.80%, optode selektif untuk ion Fe(III) dari ion pengganggu Pb(II) dan Cr(VI), dan kompleks warna yang terbentuk stabil selama 11 hari. Dengan demikian, membran optode CTA dapat digunakan untuk deteksi besi dan hasilnya dapat diterima.
Keyword: besi, optode, selulosa triasetat, tiosianat

Judul: Evaluasi Kinerja Metode Deteksi Besi dalam Air Menggunakan Membran Optode Berbasis Selulosa Triasetat
Abstrak: Besi merupakan logam berat yang mencemari lingkungan perairan dan dapat membahayakan kesehatan manusia. Oleh karena itu, diperlukan metode untuk mendeteksi kadar logam besi (Fe) di perairan dengan cepat dan mudah. Besi dideteksi menggunakan sensor optik (optode). Penelitian ini bertujuan memfabrikasi membran optode berbasis selulosa triasetat dengan menambahkan reagen selektif terhadap Fe(III). Optode dibuat dengan mencampurkan polimer selulosa triasetat (CTA) dengan tambahan pemlastis (asam oleat dan asetofenon), alikuot 336, dan ion tiosianat. Kinerja optode dievaluasi berdasarkan linearitas, batas deteksi dan kuantitasi, presisi, akurasi, dan selektivitas. Linearitas terbaik optode didapatkan koefisien determinasi (R2) 0,9972 pada konsentrasi 0,1–4,0 ppm. Batas deteksi dan kuantitasi diperoleh berturut-turut 9,88×10-7 M dan 0,1676 ppm, dengan presisi 3,01% dan akurasi 101,62±0,04%. Optode memiliki selektivitas yang baik terhadap ion penganggu Pb(II) dan Cr(VI). Aplikasi dalam sampel air menggunakan membran optode menunjukkan rerata konsentrasi 0,0578 ppm dan hasil pengujian tidak berbeda nyata dengan hasil deteksi menggunakan metode standar spektrofotometer UV-Vis, yaitu 0,0584 ppm., Iron is a heavy metal that pollutes the aquatic environment and threatens human health. Therefore, a quick and easy method is needed to detect iron (Fe) metal content in the aquatic environment. Iron detection can use an optical sensor (optode). This research aims to fabricate optode membranes based on cellulose triacetate with selective reagents for Fe(III). The optode was fabricated by mixing cellulose triacetate (CTA) polymer with plasticizer (oleic acid and acetophenone), aliquot 336, and thiocyanate ion. The performance was evaluated based on linearity, limit of detection and quantitation, precision, accuracy, and selectivity. The best optode linearity was obtained by a coefficient of determination (R2) of 0,9972 at a concentration of 0.1–4.0 ppm. The LOD and LOQ were 9,88×10-7 M and 0,1676 ppm, respectively, with a precision of 3.01% and an accuracy of 101.62±0,04%. The optode gave good selectivity for Pb(II) and Cr(VI) ions interfering. Application in water samples using the optode membrane showed an average concentration of 0.0578 ppm, and the results indicated no significant difference with the detection result using a standard UV- Vis spectrophotometer method, which was 0.0584 ppm.
Keyword: besi, evaluasi kinerja, optode, selulosa triasetat, tiosianat

Judul: The Effects of Variance of Interest rate to Variance of Annuity Future Values
Abstrak: Time value of money is a concept that refers to the difference of the value of money due to time difference. The value of money for present time would not be the same as the value of money in the future. The value of money for present time is called as Present Value (PV) of the money and the value of money for future time is called Future Value (FV) of the money. Determination the value of money, for present and future time, depends on the time and rate of return. The value of money is determined by several factors such as inflation, fluctuation of interest rates, and government policy in securities and taxation. Due to fluctuation of the value of money we need a FV formulation, it is useful for knowing whether an investment can be profitable or not, and this information is useful also in budget analysis. Annuity is defined as a series of payments made for a specific period. The payment, fixed or varied, can be made at the beginning or at the end of the period. Annuity paid at the beginning of the period is called annuity-due and annuity paid at the end of the period is called immediate annuity-certain. The accumulated value of the annuity after few years later is called as a final value or a future value. Burnecki et al. (2003) have discussed about the FV of a fixed-rate annuity in which payments are made according to the arithmetic or geometric series. They have also examined FV for annuities in which payments are made according to arithmetic or geometric series with random rates of interest. This paper examines FV for annuity-due in which payments are made according to arithmetic or geometric series with interest rates as a random variable, which is normal distribution ,  . Future value formula is expressed in recursive form. FV for annuity-due which payments are made according to the arithmetic or geometric series with random rates of interest is calculated by theoretical way and simulation way. The random rates of interest is denoted as k k i  i  , where k i an independent random variable; i is a constant and k  is a random variable which has normal distribution ,  . By using the determined parameters, a sequence of random rates of interest are generated for theoretical calculation. Meanwhile for the simulation, the random rates of interest is generated 1000 times for the simulation. The generated data give mean value, variance, and standard deviation. Moreover, error of mean value, variance, and standard deviation from the theoretical and simulation results are calculated. Error calculation uses Symmetric Mean Absolute Percentage Error (SMAPE). The smaller the value of SMAPE is the more accurate the simulation. The interest rate variances are varied from 0.000036 to 0.0001 to study the relationship between variance of rates of interest and variance of future value. The theoretical and simulation results show that when the variance of random rates of interest increases, then the variance of FV increases linearly. FV of the annuity-due in
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