PEMBENTUKAN ESTER BORAT TERKATALISIS ASAM UNTUK ANALISIS BORON SECARA SPEKTROFOTOMETRI
Abstract
Pembentukan ester borat menggunakan katalis asam pada penentuan boron secara spektrofotometri telah diteliti untuk meningkatkan sensitivitas metode analisis boron melaui optimasi jenis dan konsentrasi katalis asam. Boron dipisahkan dari matriks melalui reaksi esterifikasi dengan alkohol dan dehidrasi ester borat ke dalam kurkumin yang dilanjutkan dengan penentuan secara spektrofotometri pada ? 555 nm. Pengaruh jenis dan konsentrasi katalis asam terhadap laju esterifikasi asam borat diamati dengan menggunakan asam asetat, asam format, asam fosfat, asam sulfat dan asam klorida dengan konsentrasi 2,5; 4,5; 6,5; 8,5 dan 10,5 %. Kondisi optimum metode divalidasi untuk digunakan dalam analisis boron dan senyawa turunannya yang terdapat dalam sampel krupuk. Serapan kompleks boron-kurkumin maksimum pada penggunaan katalis H2SO4 dengan konsentrasi 2,5%. Analisis boron menggunakan spektrofotometri UV-Vis melalui distilasi ester borat memberikan persen perolehan kembali yang baik pada rentang 99,98-104,62% dengan nilai LOD dan LOQ secara berturut-turut sebesar 0,316 dan 1,056 mg L-1. Metode ini memiliki sensitivitas yang tinggi dengan nilai absorptivitas molar sebesar 4,7x105 Lmol-1cm-1 dan keterulangan yang dapat diterima yaitu ? 2%. Konsentrasi boron dalam sampel krupuk berada pada rentang 2,936-4,12 mgkg-1.
Kata kunci: boron, distilasi, ester borat, katalis asam, spektrofotometri.
ABSTRACT
The formation of borate ester catalyzed by acid for spectrophotometric analysis of boron was investigated. It was conducted to improve the sensitivity of the boron analysis method by optimizing the type and concentration of acid catalyst that can increase the quantity of esterified boric acid. Boron was separated from the sample matrices by dissolving the boric acid in alcohols, then dehydrated into curcumin followed by spectrophotometric determination at ? 555 nm. The influence of the type and concentration of acid catalyst against the esterification rate was observed by using acetic acid, formic acid, phosphoric acid, sulfuric acid, and hydrochloric acid with a concentration of 2.5; 4.5; 6.5; 8.5, and 10.5%. Method validation was carried out under the optimal conditions and used to measure boron and its derivatives in the crackers sample. Maximum absorbance of the boron-curcumin complex was obtained by using an H2SO4 catalyst at the concentration of 2.5%. Spectrophotometric analysis of boron through borate ester distillation gave a good recovery in the range of 99.98-104.62% and acceptable repeatability of ? 2%. The limit of detection and limit of quantification was found to be 0.316 and 1.056 mg L-1, respectively. This method has a high sensitivity level with a molar absorptivity value of 4.7x105 Lmol-1cm-1. Boron content in the cracker sample ranged from 2.936 to 4.912 mgkg-1.
Keywords: acid catalyst, boron, borate ester, distillation, spectrophotometry.
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