• Journal of Electrochemical Science and Technology
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• 제7권1호
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• pp.68-75
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• 2016

In this study a new, simple, precise, accurate and economic electrochemical method was developed and validated for the voltammetric determination of zolpidem (ZP) using disposable pencil graphite (PG) electrode. The anodic oxidation of ZP on the surface of the PG electrode was examined in a britton robinson (BR) buffer. Square wave and cyclic voltammetry were used as electrochemical techniques in the potential range of 0-1.2 V in the pH 8 BR buffer. In cyclic voltammetry studies, the diffusion coefficient of ZP oxidation was found to be 3.6×10^-6 cm² s^-1. On the other hand, the ZP has shown a well-defined irreversible anodic peak at 0.98 V in the square wave voltammetry mode. The PG electrode, primarily being graphite which has a large active surface area gives rise to increasing peak current with respect to ZP electrooxidation. PG electrode showed an electrocatalytic effect in anodic oxidation of ZP. A linear relationship between catalytic current response and ZP concentration was obtained over a concentration range of 10-30 μM with R.S.D. values ranging from 0.29-3.89. Limits of detection and quantitation were found to be 1 and 3 μM, respectively. Finally, the PG electrode was successfully used to determine ZP in standard and tablet dosage forms with a mean recovery of 100.69 %.

• 분석과학
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• 제12권3호
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• pp.218-223
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• 1999

스크린 프린팅 기술을 이용하여 일회용 에탄올 센서를 개발하고 전기화학적 방법으로 그 성능을 조사하였다. 일회용 에탄올 센서는 폴리에스테르 기질 위에 탄소와 은 반죽 그리고 절연체 잉크로 작업 및 기준전극의 감응부위와 전기적 접촉부위의 형상을 차례로 인쇄한 후 알코올탈수소효소(ADH) 또는 알코올산화효소(AOD)를 알려진 전자전달 매개체(mediator)와 함께 작업전극에 고정시켜 제작하였다. 일회용 센서의 제작 과정에서 감응도와 재현성을 높이기 위하여 프린팅한 탄소 작업전극을 전처리 하는 몇 가지 방법들을 적용하고 그 결과들을 비교하였다. 제작된 일회용 센서는 소량의 혈액시료로 음주측정을 하는데, 그리고 발효공정 제어 등에 유용하게 사용될 수 있다.

• Bulletin of the Korean Chemical Society
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• 제29권5호
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• pp.928-932
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• 2008

A glassy carbon electrode (GCE) modified with poly(p-aminobenzene sulfonic acid) [Poly(p-ABSA)] film is fabricated by voltammetric technique in phosphate buffer solution (pH 8.0) containing $5.0\;{\times}\;10^{-3}\;mol\;L^{-1}$p- ABSA. Electrochemical behaviors of tryptophan at the Poly(p-ABSA) film electrode are investigated with voltammetry. The results indicate that the electrochemical response of tryptophan is improved significantly in the presence of poly(p-ABSA) film. Compared with the bare glassy carbon electrode, the Poly(p-ABSA) film electrode remarkably enhances the irreversible oxidation peak current of tryptophan. Some parameters such as voltammetric sweeping segments for the electrochemical polymerization, pH, accumulation potential and accumulation time are optimized. Under the optimal conditions, the oxidation peak current is proportional to tryptophan concentration in the range of $1.0\;{\times}\;10^{-7}$ to $1.0\;{\times}\;10^{-6}\;mol\;L^{-1}$, and $2.0\;{\times}\;10^{-6}$ to $1.0\;{\times}\;10^{-5}\;mol\;L^{-1}$ with a detection limit of $7.0\;{\times}\;10^{-8}\;mol\;L^{-1}$. The proposed procedure is successfully applied to the determination of tryptophan in a commercial amino acid oral solution.

• 전기화학회지
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• 제17권4호
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• pp.216-221
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• 2014

전기 화학적으로 활성화된 glassy carbon 전극을 사용하여 Clenbuterol 의 정량측정을 위해 신속하고 민감한 전압-전류 법을 개발하였다. 시차 펄스 전압-전류 법(Differential pulse voltammetry)을 이용하여, Clenbuterol에 대해 $1{\times}10^{-7}M$에서 $2{\times}10^{-5}M$의 범위에서 선형적인 반응을 보였으며 검출한계는 $6{\times}10^{-9}M$ (S/N = 3)이었다. Clenbuterol 의 농도가 $1{\times}10^{-6}M$에서의 상대표준편차는 4.3%이었다. 다양한 양의Clenbuterol이 포함된 소변 샘플로부터 96%의 회수율을 나타냈다. (N = 3, $5{\times}10^{-7}M$에서 $1{\times}10^{-6}M$의 Clenbuterol)

• Journal of Electrochemical Science and Technology
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• 제15권3호
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• pp.405-413
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• 2024

Several techniques for determining the reverse peak current from a cyclic voltammogram (CV) for a reversible system are described in the literature: CV itself as a baseline with long switching potential (E_λ) that serves as a baseline for other CVs, Nicholson equation that uses CV parameters to calculation reverse peak current and linear extrapolation of the current obtained at the switching potential. All methods either present experimental difficulties or large errors in the peak current determination. The paper demonstrates, both theoretically and experimentally, that trapezoidal cyclic voltammetry (TCV) can be used as a baseline to determine anodic peak current (i_ap) with high accuracy and with a switching potential shorter than that used by CV, as long as E_λ is at least 130 mV away from the cathodic peak. Beyond this value of switching potential the electroactive specie is completely depleted from the electrode surface. Using TCV with E_λ = 0.34 V and a switching time (t_λ) of 240 s as a baseline, the determination of the reverse peak current presents a deviation from the expected value of less than 1% for most of the CVs studied (except cases when E_λ is close to the direct potential peak). This result presents better accuracy than the Nicholson equation and the linear extrapolation of the current measured at the switching potential, in addition to presenting a smaller error than that obtained in the acquisition of the experimental current. Furthermore, determining the reverse peak current by extrapolating the linear fit of i_ap vs. ${\sqrt[1/]{t_{\lambda}}}$ to infinite time gave a reasonable approximation to the expected value. Experiments with aqueous potassium hexacyanoferrate (II) and ferrocene in acetonitrile confirmed the theoretical predictions.

• Journal of Electrochemical Science and Technology
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• 제11권3호
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• pp.310-317
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• 2020

A development of disposable strip-type galactose sensor for point-of-care testing (POCT) was studied, which was constructed using screen-printed carbon electrodes. Galactose levels were determined by the redox reaction of galactose oxidase in the presence of potassium ferricyanide as an electron transfer mediator in a small sample volume (i.e., less than 1 µL). The optimal performance of biosensor was systematically designated by varying applied potential, operating pH, mediator concentration, and amount of enzyme on the electrode. The sensor system was identified as a highly active for the galactose measurement in terms of the sensitivity (slope = 4.76 ± 0.05 nA/µM) with high sensor-to-sensor reproducibility, the linearity (R² = 0.9915 in galactose concentration range from 0 to 400 µM), and response time (t_95% = <17 s). A lower applied potential (i.e., 0.25 V vs. Ag/AgCl) allowed to minimize interference from readily oxidizable metabolites such as ascorbic acid, acetaminophen, uric acid, and acetoacetic acid. The proposed galactose sensor represents a promising system with advantage for use in POCT.

• KSBB Journal
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• 제13권1호
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• pp.52-57
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• 1998

The present work proposes a simple electrochemical method applicable to any immobilization processes of oxidase using a Clark type oxygen electrode as a base transducer. The present work suggests an optimal immobilization technique among three different methods of glucose oxidase(GOD) onto one side of $37[\mu}$mthick blend membranes, composed o 80% of cellulose triacetate and 20% of polycaprolactone, on the basis of the maximum Michaelis-Menten parameter(Vm) determined by either steady state or transient analyses. The electrode system was made of disk type gold cathode(4mm diameter) and Ag/AgCl anode. One side of the blend membrane was in contact with the cathode surface while the other side was immobilized with GOD either in covalent-bond or cross-linked forms, the latter being covered by $25{\mu}$m thick dialysis membrane of cellulose acetate. The resultant current density was on-line monitored by a potentiostat while glucose level was varied from 1 to 20 mM. The present study shows that direct cross-linking of GOD with glutaraldehyde was mostly preferred for fabrication of glucose sensor, on the basis of resultant kinetic parameters from either steady state or transient analyses.

• 한국생산제조학회지
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• 제21권5호
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• pp.720-725
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• 2012

Sodium hypochlorite is used worldwide as a water disinfectant and in bleaching agent. Sodium hypochlorite applied to water initially undergoes hydrolysis to form free chlorine consisting of hypochlorous acid(HOCl) and hypochlorite ion($OCl^-$). For free chlorine determination, an electrochemical method is simple due to the electroactivity of free chlorine; it measures current and is free of most reagents. Amperometric free chlorine sensor has been developed with gold (Au)-based electrode. The 3-electrode free chlorine sensor whose working and counter electrodes were Pt exhibited excellent response to HClO at +400mV vs. Ag/AgCl/sat. KCl. In addition, the use of a pH error correction algorithm provided a reliable measurement of residual free chlorine in water sample without any pretreatment in the normal pH range(pH 6~8) of municipal water supply. The free chlorine sensor installed in on-line monitoring system could be used to continually monitor the level of residual free chlorine in real samples.

• 공업화학
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• 제28권3호
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• pp.369-374
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• 2017

바이오센서를 상업적으로 양산하고자 할 때 제작비의 경제성이 고려되어야 한다. 과산화수소를 정량하기 위한 효소전극 제작 시 필수적으로 사용되는, 서양고추냉이로부터 추출된 과산화효소는 대단히 고가이므로 탄소반죽법에 의한 전극제작의 제한 요인이 된다. 이 문제를 우회하고자 본 실험실에서는 생활주변에서 쉽게 얻을 수 있는 재료로 대체하기 위하여 아카시아 잎을 효소원으로 사용하여 과산화수소 센서를 제작하고 그것의 전기화학적 특성을 살펴보았다. 일정전압전류법으로 얻어진 10개 이상의 전기화학적 파라미터와 실험적 결과들은 효소전극이 정량적으로 그 기능을 발휘하고 있음을 보여주었다. 이런 사실들은 시판 과산화효소가 아카시아 잎으로 대체될 수 있음을 보여주는 것이다.

• 한국물환경학회지
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• 제30권3호
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• pp.304-310
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• 2014

The conventional methods for total residual chlorine such as iodometry and DPD colorimetric can cause secondary pollution due to additional agents, also have a wide error range. As for alternative, electrochemical method can measure TRC(Total residual chlorine), and is not required as additional agents, also very suitable for using the fields of ballast water because test time is relatively fast. Therefore, this study was investigated for changing charge by agitation, salt concentration, and temperature change. Charge showed differences based on changes of reduction peak with or without agitation. In contrast, TRC and charge were well correlated in constant agitation speed. As TRC and charge were analyzed with high correlations in constant salinity and temperature of ocean, thereby conductivity was firstly measured, and charge had high correlation for TRC in spite of changing salinity and temperature Pt electrode revealed high reliability ($r^2=0.960$) because it was rarely effected by TRC, On the other hand, Au electrode appeared inadequate ($r^2=0.767$) to use sensor in less than 1.0 ppm of TRC. For high accuracy and detection of TRC, Pt and Au electrodes for test time were, respectively, 14 and 22 seconds. As a result, Pt electrode was more valuable than Au electrode in terms of response time.