Anaclet Nsabimana

Stainless Steel Electrode for Sensitive Luminol Electrochemiluminescent Detection of H2O2, Glucose, and Glucose Oxidase Activity

Electrogenerated chemiluminescence (ECL) application of stainless steel, a robust and cost-effective material, has been developed for the first time. Type 304 stainless steel electrode shows appealing ECL performance in the luminol-H2O2 system. It enables the detection of H2O2 with a linear range from 1 to 1000 nM and a limit of detection of 0.456 nM [signal-to-noise ratio (S/N) = 3]. The ECL method based on type 304 stainless steel electrode is more sensitive, more cost-effective, and much simpler than other ECL methods reported before. Because the stainless steel electrode has excellent performance for H2O2 detection and H2O2 participates in many important enzymatic reactions, applications of stainless steel electrode-based ECL for detection of enzyme activities and enzyme substrates were further investigated by use of glucose oxidase (GODx) and glucose as representative enzyme and substrate. The concentrations of glucose and the activity of GODx were directly proportional to ECL intensities over a range of 0.1-1000 μM and 0.001-0.7 units/mL with limits of detection of 0.076 μM and 0.00087 unit/mL (S/N = 3), respectively. This method was successfully used for determining glucose in honey. Because of their remarkable performance and user-friendly features, stainless steel electrodes hold great promise in various electroanalytical applications, such as biosensing, disposable sensors, and wearable sensors.

Development of luminol-N-hydroxyphthalimide chemiluminescence system for highly selective and sensitive detection of superoxide dismutase, uric acid and Co2+

N-hydroxyphthalimide (NHPI), a well known reagent in organic synthesis and biochemical applications, has been developed as a stable and efficient chemiluminescence coreactant for the first time. It reacts with luminol much faster than N-hydroxysuccinimide, eliminating the need of a prereaction coil used in N-hydroxysuccinimide system. Without using prereaction coil, the chemiluminescence peak intensities of luminol-NHPI system are about 102 and 26 times greater than that of luminol-N-hydroxysuccinimide system and classical luminol-hydrogen peroxide system, respectively. The luminol-NHPI system achieves the highly sensitive detection of luminol (LOD = 70pM) and NHPI (LOD = 910nM). Based on their excellent quenching efficiencies, superoxide dismutase and uric acid are sensitively detected with LODs of 3ng/mL and 10pM, respectively. Co2+ is also detected a LOD of 30pM by its remarkable enhancing effect. Noteworthily, our method is at least 4 orders of magnitude more sensitive than previously reported uric acid detection methods, and can detect uric acid in human urine and Co2+ in tap and lake water real samples with excellent recoveries in the range of 96.35-102.70%. This luminol-NHPI system can be an important candidate for biochemical, clinical and environmental analysis.

Sensitive and selective electrochemical detection of artemisinin based on its reaction with p-aminophenylboronic acid.

The electrochemical detection of artemisinin generally requires high oxidation potential or the use of complex electrode modification. We find that artemisinin can react with p-aminophenylboronic acid to produce easily electrochemically detectable aminophenol for the first time. By making use of the new reaction, we report an alternative method to detect artemisinin through the determination of p-aminophenol. The calibration curve for the determination of artemisinin is linear in the range of 2xa0μmolxa0L(-1) to 200xa0μmolxa0L(-1) with the detection limit of 0.8xa0μmolxa0L(-1), which is more sensitive than other reported electrochemical methods. The relative standard deviation is 4.83% for the determination of 10xa0μM artemisinin. Because the oxidation potential of p-aminophenol is around 0xa0V, the present method is high selective. When 40xa0μM, 90xa0μM and 140xa0μM of artemisinin were spiked to compound naphthoquine phosphate tablet samples, the recoveries are 107.6%, 105.4% and 101.7%, respectively. This detection strategy is attractive for the detection of artemisinin and its derivatives. The finding that artemisinin can react with aromatic boronic acid has the potential to be exploited for the development of other sensors, such as fluorescence artemisinin sensors.

Stainless steel electrode for simultaneous stripping analysis of Cd(II), Pb(II), Cu(II) and Hg(II)

Traditional electrodes for stripping analysis generally have narrow electrochemical window, require the modification of electrode or the addition of additional ions. To solve these problems, stainless steel has been used as the electrode for electrochemical stripping analysis for the first time. Square wave anodic stripping voltammetry (SWASV) has been used for the detection of Cd2+, Pb2+, Cu2+, and Hg2+. Type 304 stainless steel electrode gives well-defined, sharp, and separated stripping peaks for these metal ions. The electrode, best operated at +u202f0.3u202fV (Hg2+), -u202f0.05u202fV (Cu2+), -u202f0.41u202fV (Pb2+), and -u202f0.7u202fV (Cd2+) and after a 300u202fs deposition at -u202f1.0u202fV, has linear responses in the concentration ranges of 0.075-5u202fμM for Pb2+ and Cu2+, 0.5-5u202fμM for Cd2+, and 0.1-5u202fμM for Hg2+. The limits of detection (at S/Nu202f=u202f3) are 0.033u202fµM for Pb2+, 0.0073u202fµM for Cu2+, 0.23u202fµM for Cd2+, and 0.028u202fµM for Hg2+. The reproducibility, expressed as relative standard deviation, is 3.2% for Pb2+, 2.6% for Cu2+, 5.1% for Cd2+, and 2.5% for Hg2+ (each 1u202fμM levels; for nu202f=u202f6). The electrode was successfully applied to the determination of the ions in spiked groundwater samples. This study shows that stainless steel is a better alternative to mercury electrode for stripping analysis because of its well-defined and sharp stripping peaks, high sensitivity, low background, low toxicity, good reproducibility, and much wider electrochemical window.

Sensitive electrochemical detection of sodium azide based on the electrocatalytic activity of the pasting liquid of a carbon paste electrode

AbstractSodium azide (NaN3) is highly toxic and widely used in, for example, automobile airbags and biochemical laboratories. The electrochemical detection of sodium azide on commonly used electrodes is challenging due to sluggish electron transfer, but it has been achieved using a boron-doped diamond thin-film electrode and a highly oriented pyrolytic graphite electrode. Utilizing the electrocatalytic activity of the pasting liquid of a carbon paste electrode, we developed an effective method for the electrochemical detection of sodium azide in which silicone oil was employed as the pasting liquid of the carbon paste electrode. This simple and cheap silicone-oil-based carbon paste electrode exhibited comparable sensitivity to the boron-doped diamond thin-film electrode and highly oriented pyrolytic graphite electrode. The limit of detection for sodium azide at the silicone-oil-based carbon paste electrode was found to be 0.1xa0μM. Recoveries from diluted human serum samples were between 97.2 and 101.3%.n Graphical abstractᅟ

Tris(2,2′-bipyridyl)ruthenium(II) electrochemiluminescent determination of ethyl formate

AbstractEthyl formate is extensively used as food flavor, fungicide, and larvicide. It naturally exists in coffee, fruits, honey, brandy, and rum as well as dust clouds in an interstellar space of the Milky Way galaxy. Herein, its electrochemiluminescence (ECL) property has been firstly investigated. It shows intense ECL in reaction with Ru(bpy)32+ as luminophore, and thus a rapid and sensitive detection method for ethyl formate is proposed. Effects of pH, working potential, scan rate, and concentration of Ru(bpy)32+ were studied. ECL spectrum analysis was used to reveal the reaction mechanism. At the optimized experimental conditions, a linear relationship between ECL intensities and concentrations of ethyl formate is observed from 3.0xa0μM to 1.0xa0mM (R2u2009=u20090.997). The limit of detection for ethyl formate is 0.7xa0μM (S/Nu2009=u20093). The relative standard deviation with 1.0xa0mM concentration of ethyl formate for nine analyses is 2.7%. A 101.20–102.10% recovery was obtained in a real samples analysis.n Graphical Abstractᅟ

Determination of Concentrated Hydrogen Peroxide Free from Oxygen Interference at Stainless Steel Electrode

H2O2 is frequently used at high concentrations in various applications. It is very challenging to detect high concentrations of H2O2 and to eliminate oxygen interference for H2O2 detection through electrochemical reduction. In the present investigation, the electrochemistry of H2O2 at stainless steel electrode has been carried out for the first time. A cathodic peak for H2O2 reduction was observed at about -0.40 V, and no cathodic peak for dissolved oxygen reduction was observed on type 304 stainless steel electrode. Amperometric determination of H2O2 on type 304 stainless steel electrode displayed a linear range from 0.05 up to 733 mM with a detection limit of 0.02 mM (S/N = 3) and a sensitivity of 16.7 μA mM-1 cm-2. The type 304 stainless steel electrode not only shows much higher upper limit than other reported electrodes for the detection of concentrated H2O2 but also is free from oxygen interference, which is of great importance for practical applications. This method could detect H2O2 in wound wash and lake water with excellent recoveries. Moreover, we successfully applied the stainless steel electrode to determine glucose using glucose oxidase to catalyze the oxidation of glucose to generate hydrogen peroxide. The linear range for glucose is between 0.5 and 25 mM, which covers clinically important blood glucose concentrations well.