Judul: Desorpsi Timbal pada Kerang Darah (Anadara granosa) Menggunakan Ekstrak Air Kulit Jeruk Siam dan Pektinnya
Abstrak: Blood cockles (Anadara granosa) from some sources were reported to contain lead above the threshold as defined by the Standar Nasional Indonesia (SNI). In this experiment, orange peel extract and its pectin were used to reduce the lead content on blood cockles. Aqueous extract orange peels were obtained by crushing the peels and mixed with in proportion of 1:3. Pectin was extracted from the peels using HCl 0.1 N at pH 1.5, and temperature 95 °C for 40 minutes. The pectin yield was 10.18%, equivalent weight 1180.45 g/eq, methoxyl content 6.52% (w/w), galacturonic acid 57.65% (w/w), and degree of estherification 64.24% (w/w). Samples of blood cockles purchased from Pasar Anyar Bogor. The result showed that lead content was below SNI threshold. The samples of blood cockle meat were soaked in lead solution and desorption of lead could be measured. Desorption process were performed by soaking the samples in the extract solution and in 0.2% pectin solution for 60 minutes. The aqueous extract of orange peel reduced lead content by 46%, whereas pectin solution was able to reduced for 48%.
Keyword: Anadara granosa, desorption, lead, pectin, siam orange peel

Judul: Desorpsi Logam Pb dari Kerang Darah (Anadara granosa) Menggunakan Ekstrak Air dan Pektin Kulit Pisang Kepok (Musa paradisiaca)
Abstrak: Lead pollutant on foodstuffs such as in meat blood cockle must be solved because lead is carcinogenic. Efforts for foodstuff safety from various pollutants must be supported. The objectives of this research were utilizing water extract and pectin solution from waste of kepok peels (Musa paradisiaca) as the medium for desorption lead from blood cockle (Anadara granosa). Water extract was obtained by destructing kepok peels with water (1:3). Pectin was obtained by extracting kepok peels using water at pH 2, temperature 90 °C for 1 hour, and precipitated the dissolved pectin by adding 96% ethanol. The pectin yield was 3% (b/b) with loss on drying 13.9%, ash content 4.2%, equivalent weight 1755 g/eq, methoxyl 1.40%, galacturonic acid 18%, and degree of esterification 44%. The ability of 0.20% pectin solution for desorption lead from sample was 51%, which was lower than that by using water extract of 58%.
Keyword: pectin, kepok peels, desorption of Pb, blood cockle

Judul: igenvalues and Eigenvectors of Tridiagonal Matrix with Non Constant and Recurrent Diagonal Entries.
Abstrak: Matriks tridiagonal adalah suatu matriks yang mempunyai entri-entri bernilai nol kecuali pada diagonal utama, di bawah diagonal utama (subdiagonal) dan di atas diagonal utama (superdiagonal). Entri pada diagonal utama tidak konstan dan berulang. Setiap entri pada matriks tridiagonal ini adalah bilangan kompleks. Dalam karya ilmiah ini, akan dibuktikan 3 teorema untuk menentukan nilai eigen dengan 2 kasus dan 1 teorema untuk menentukan vektor eigen. Teorema pertama menentukan polinomial karakteristik dari matriks tridiagonal. Polinomial karakteristik dari matriks tridiagonal tersebut digunakan untuk menentukan nilai eigen pada teorema kedua dan ketiga serta menentukan vektor eigen pada teorema keempat
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