The new molecularly imprinted polymer (MIP) membrane based on cassava starch—Fe3O4—was developed to detect acetaminophen and caffeine simultaneously with the differential pulse voltammetry (DPV) method. Cassava starch was reacted with sodium tripolyphosphate (STPP) as a crosslinking agent, while acetaminophen and caffeine were added as templates. The Fe3O4 nanoparticles in the composite were added to increase the sensor’s sensitivity. The experimental results show that the ratio between cassava starch:STPP:acetaminophen/caffeine in the mixture for MIP membranes influences the sensitivity of the sensor obtained. MIP membranes with the best sensitivity is produced at a mixture ratio of 2:2:1. The sensor performance is also affected by the pH of the solution and the type of buffer solution used. The sensor works very well at pH 2 in PB solution. Sensors produced from GCE modified with MIP membrane from cassava starch—Fe3O4 with acetaminophen and caffeine as templates have linear range concentrations, respectively, at 50–2000 µM and 50–900 µM. Sensor sensitivity was 0.5306 A/M against acetaminophen and 0.4314 A/M against caffeine with Limit of Detection (LoD), respectively, 16 and 23 µM. Sensor selectivity and sensitivity are better than those without MIP and can be applied for the determination of the content of acetaminophen in headache medicine, with an accuracy of 96–99% and with Relative Standard Deviation (RSD) 0.9–2.56%.
A conductimetric enzyme biosensor for uric acid detection has been developed. The uricase, as enzyme, is isolated from Candida utilis and immobilized on a nata de coco membrane-Pt electrode. The biosensor demonstrates a linear response to urate over the concentration range 1–6 ppm and has good selectivity properties. The response is affected by the membrane thickness and pH change in the range 7.5–9.5. The response time is three minutes in aqueous solutions and in human serum samples. Application of the biosensor to the determination of uric acid in human serum gave results that compared favourably with those obtained by medical laboratory. The operational stability of the biosensor was not less than three days and the relative error is smaller than 10%.
Modification of electrodes on a screen printed carbon electrode (SPCE) using polypyrrole (Ppy)-SiO 2 has been successfully conducted for phenol determination. Modification has been undertaken with electropolymerization-wise using cyclic voltammetry. Electrode resulted are used to determine phenol using cyclic voltammetry and differential pulse voltammetry. A cyclic voltammetry analysis using potential range of -1 to 1 V versus Ag/AgCl at scan rate of 100 mV/sec. Meanwhile, analysis using differential pulse voltammetry method applied potential range of 0 to 1 V versus Ag/AgCl, scan rate of 50 mV/sec, pulse rate of 0.2 V, and pulse width of 50 ms. The results provide the increase of pH and decrease of Epa potential peak. It may increase in the current of phenol. Modified SPCE Ppy-SiO 2 can be applied for phenol determination at a concentration of 10 3 -10 -5 mM with sensitivity of 7.93 μA/mM.
Potentiometric urea biosensor development is based on urea hydrolysis by urease resulted CO2. The biosensor is used chitosan membrane and the H3O+ electrode as a transducer. The research was studied of effecting pH and membrane thickness to the biosensor performance. The best biosensor performance resulted at pH = 7.3 and 0.2 mm of membrane thickness. The biosensor has a Nerntian factor 28.47 mV/decade; the concentration range is 0.1 up to 6.00 ppm; and the limit of detection is 0.073 ppm. The response time of this biosensor is 280 seconds, efficiency 32 samples and accuracy 94% up to 99%. Keywords: biosensor, potentiometry, urea, chitosan membrane
The existence of lead (Pb) compounds in waters can be caused of waste pollution from industrial activities such as dye and battery industries. Lead is toxic and able to cause some deseases. The aim of this study is to create solid phase from natural material as an alternative method for determination of lead in water samples. The solid phase is silica prepared from rice husks ash (RHA), was prepared and modified using chitosan. To achieve that aim, the optimization of silica : chitosan composition was performed. The influence of Pb 2+ concentration and citric acid concentration was studied to obtain optimum recovery of Pb 2+ . Interaction between Pb 2+ ion and solid phase silica -chitosan could be estimated based on the result. This showed the optimum composition of silica : chitosan was 65% silica : 35% chitosan with Cation Exchange Capacity (CEC) 0.00455 mek/g. Mass adsorbed Pb 2+ for 1 g silica : chitosan 65% was 9.715 mg/g. Optimum recovery of Pb 2+ on solid phase extraction was reached at concentration of Pb 2+ 10 ppm and citric acid concentration 0.05 M (88.25 % and 81.18 %). This result indicated that solid phase extraction prepared from silica -chitosan can be applied as an alternative method for Pb 2+ determination in water.
AbstrakSilika dari abu sekam padi yang dimodifikasi dengan kitosan menghasilkan suatu adsorben yang dapat meningkatkan daya adsorpsi terhadap ion logam. Adsorben kitisansilika dari abu sekam padi dibuat dengan komposisi 100, 95, 85, 75 dan 65 % silika dalam kitosan. Hasil penelitian menunjukkan bahwa peningkatan jumlah kitosan dapat meningkatkan nilai kapasitas tukar kation (KTK) adsorben. Adsorben terbaik dihasilkan pada % silika 65% dengan KTK 0,45 mekiv H + /g adsorben. Adsorbent tersebut mempunyai daya adsorpsi terhadap Pb 2+ sebesar 11,8 mg/g adsorben dan 0,3 mg/g adsorben terhadap Cu 2+ . AbstractModification of silica from rice husk ash with chitosan resulted a high capacity adsorbant. The composition of silica from rice husk ash in adsorbent are 100, 95, 85, 75, and 65% in chitosan. The result of researsh show that the chitosan increasing cation exchange capasity (CEC) of adsorbent. The best adsorbent is 65% silica with CEC 0,45 mekiv H + /g adsorbent. The adsorbent has ability to adsorb Pb 2+ is 11,8 mg/g adsorben and 0,3 mg/g adsorben to Cu 2+ .
Development and validation of analytical methods has been performed for determination of heavy metals cadmium (Cd) and lead (Pb) in two types of chocolate, prior to use of domestic microwave-assisted acid digestion method without modification. Heavy metals were analyzed by flame atomic absorption spectrometry. The analysis showed that the microwave digestion has complied to the terms of validation, linearity >0.99, mean recoveries from 92.6 to 103.2%, repeatability of the method (inter-day) and intra-day gave relative standard deviation (RSD) from 1.6 to 4.8%. Limit of detection (LOD) of Cd and Pb of 0.006 and 0.02 mg/kg respectively and quantification (LOQ) 0.025 mg/kg for Cd and 0.042 mg/kg for Pb. Robustness of the method gave relative standard deviation from 2.6 to 4.8%. The procedure of microwave digestion of developed is very practical, easy, fast, accurate, precise, reliable and useful for routine laboratory analyses of a large number of samples. Keywords: AAS, microwave digestion, heavy metal, validation methodPengembangan dan validasi metode analisis telah dilakukan untuk penentuan logam berat cadmium (Cd) dan timbal (Pb) dalam dua jenis cokelat. Sampel ditambahkan asam dan didestruksi dengan gelombang mikro rumah tangga tanpa modifikasi. Pengukuran logam berat menggunakan spektroskopi serapan atom (SSA). Hasil analisis menunjukkan bahwa destruksi gelombang mikro telah memenuhi persyaratan validasi seperti linieritas >0,99 dan rata-rata perolehan kembali 92,6-103,2%. Parameter ketelitian yang dilakukan pada hari yang sama maupun berbeda memperoleh standar deviasi relatif (RSD) <5%, batas deteksi metode (LOD) Cd dan Pb masing-masing 0,006 dan 0,02 mg/kg, sedangkan batas kuantitasi (LOQ) 0,025 mg/kg untuk Cd dan 0,042 mg/kg untuk Pb. Kekuatan metode menghasilkan standar deviasi relatif 2,6-4,7%. Prosedur destruksi gelombang mikro yang dikembangkan sangat praktis, dan dikategorikan sebagai metode preparasi yang mudah, cepat, akurat, teliti, dapat diandalkan dan dapat dijadikan sebagai metode analisis rutin di dalam laboratorium dengan beberapa jenis sampel dalam jumlah yang banyak.Kata Kunci: destruksi gelombang mikro, SSA, logam berat, validasi metode *Penulis korespodensi:
Keberadaan timbal di lingkungan yang disebabkan oleh polusi dapat masuk dalam darah. Menurut Center for Disease Control and Prevention (CDC) batas ambang timbal dalam darah yaitu 4.8×10-7 M. Apabila melebihi batas tersebut maka dapat menyebabkan keracunan bahkan kematian. Dengan demikian diperlukan kontrol darah secara berkala dengan metode relatif mudah. Pada penelitian ini dikembangkan sensor timbal dalam darah berbasis elektroda selektif ion timbal yang dimodifikasi dengan membran kitosan dan garam timbal sulfida (PbS) sebagai bahan aktif. Penelitian ini bertujuan menentukan kondisi optimum dalam pengembangan sensor ion timbal. Konsentrasi bahan aktif (PbS) yang ditambahkan dalam larutan kitosan yaitu 0,5% sampai 2,5% (b/v). Ketebalan membran yang digunakan yaitu 15 µm; 25 µm; 40 µm; 75 µm. Elektroda diuji pada pH larutan 2; 3; 4 dan 5 dengan konsentrasi larutan standar Pb(NO3)2 10-8 M hingga 10-1 M. Kinerja optimum elektroda diperoleh pada konsentrasi PbS 1,5% dengan ketebalan membran 15 µm dan pH larutan 4. Bilangan Nernst yang diperoleh yaitu 24,35 mV/dekade dengan kisaran konsentrasi 0,032 ppm hingga 0,322 ppm dan konsentrasi larutan terkecil yang digunakan yaitu 0,032 ppm.
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