A chemiluminescence reagent free method for the determination of captopril in medicine and urine samples by using trivalent silver

Multiple fluorescence quenching effects mediated fluorescent sensing of captopril Based on amino Acids-Derivative carbon nanodots

Carbon nanodots (CNDs) were facilely synthesized through a pyrolysis procedure with histamine, an amino acid rich in element carbon and nitrogen, being the precursor. Taking advantage of the favorable fluorescence performance of CNDs, a multiple fluorescence quenching effects mediated fluorescent sensor was established for captopril (CAP) detection. MnO₂ NPs were firstly combined with CNDs via electrostatic attraction and subsequently quenched the fluorescence. The quenching mechanisms were concluded to be the combined effects of fluorescence resonance energy transfer (FRET) and inner filtration effect (IFE). Subsequently CAP triggered a unique redox reaction and decomposed the quencher so that renewed the fluorescence. Hence, the sensitive and selective detection of CAP was achieved through the indication of fluorescence recovery efficiency. A proportional range of 0.4 ∼ 60 μmol L^-1 with the LOD of 0.31 μmol L^-1 was obtained. The sensor was further applied to the real sample detection and the satisfactory results revealed the practical value of CNDs. The facile synthesis of CNDs and brand-new sensing mechanism made it a novel fluorescent method and could improve the analysis of CAP.

Highly sensitive voltammetric determination of captopril on renewable amalgam film electrode

New highly sensitive voltammetric method for captopril (CPT) determination was developed. The main novelty of the work was the application of a renewable amalgam film electrode (Hg(Ag)FE) for this purpose. During the research instrumental parameters of the developed method were optimized and were as follows: t_w = t_s = 5 ms, E_s = 5 mV, ΔE = 100 mV. Preconcentration potential and time were equal to 100 mV and 20 s, respectively. All measurements were conducted in electrolyte consisted of 0.1 M HClO₄. Limit of detection was calculated and was equal to 1.9 nM (0.39 ng mL^-1) for 20 s preconcentration time and Hg(Ag)FE surface area approximately 11.2 mm². Linearity was achieved in the concentration range 0.05-1 μM. Repeatability of the method expressed as variation coefficient was estimated at 3.5% (0.15 μM CPT, n = 10). Applicability of the method was confirmed by analysis of tablets containing CPT and urine. Recoveries were in the range from 95 to 109% suggesting that the method might be assumed as accurate. Obtained results were also in good agreement with the producer declaration.

Introducing hierarchical hollow MnO2 microspheres as nanozymes for colorimetric determination of captopril

A simple sensor was developed for the colorimetric determination of captopril (CPT). Herein, hierarchical hollow MnO₂ microspheres (HH-MnO₂) were applied as nanozymes with peroxidase-mimetic activity. Free cation radicals with a strong absorption signal (λ_max at 653 nm) were generated via a redox reaction between 3, 3', 5, 5'-tetramethylbenzidine (TMB) and HH-MnO₂. Captopril could successfully prevent the generation of blue-colored free cation radicals. The influence of CPT concentration on the absorption of the generated radicals was monitored by UV-Vis spectroscopy. The corresponding linear concentration range was from 1.0 to 30.0 μg mL^-1 (4.6-138.1 μmol L^-1), and the detection limit was found to be 0.26 μg mL^-1 (1.2 μmol L^-1). As a practical usage, the developed sensor was effectively utilized to measure the content of CPT in pharmaceutical formulations.

Cataluminescence sensor for highly sensitive and selective detection of iso-butanol

In this paper, a gaseous sensor was described for detection of iso-butanol on the basis of its strong cataluminescence (CTL) emission on nano-MgO surface. The sensor showed high sensitivity and specificity to iso-butanol with response time less than 1 s and recovery time less than 18 s. A good linearly relationship between CTL intensity and the concentration of iso-butanol was observed in the range of 7.6-3350 mg/m³ (r = 0.9992), the limit of detection was 2.5 mg/m³. The proposed CTL sensor exhibits good specificity to iso-butanol against other compounds including common alcohols. The possible reaction paths of iso-butanol on the MgO surface were investigated in detail. Results shows that the hydrogen atom abstraction of iso-butanol to form β-R_iso following consumption via Waddington mechanism possible is a major reaction channel for CTL emission. The sensor was applied to analyze iso-butanol in spiked samples, satisfactory recoveries were obtained in the range of 96.6-112.8% and the RSDs were 5.0-10.1%, indicating that the proposed sensor is a promising candidate for rapid analysis of iso-butanol.