Development and Validation of an Automated Zone Fluidics-Based Sensor for In Vitro Dissolution Studies of Captopril Using Total Error Concept

In the present research, a zone fluidics-based automated sensor for the analysis of captopril in in vitro dissolution samples is reported. Captopril is reacted under flow conditions with Ni(II) (10 mmol L⁻¹) in alkaline medium (0.15% v/v NH₃) to form a stable derivate, which is monitored spectrophotometrically at 340 nm. The chemical and instrumental parameters were carefully investigated and optimized. The validation of the developed method was performed in the range of 5 to 120% of the expected maximum concentration using the accuracy profiles as a graphical decision-making tool. The β-expectation tolerance intervals did not exceed the acceptance criteria of ±10%, which means that 95% of future results will be encompassed in the defined bias limits. The variation of the relative bias ranged between −2.3% and 3.5% and the RSD values for repeatability and intermediate precision were lower than 2.3% in all cases. The limit of detection (LOD), and the lower and the upper limit of quantification (LLOQ, ULOQ) were satisfactory and found to be 1%, 5% and 120% (corresponding to 0.6, 2.78 and 66.67 μg mL⁻¹ in dissolution medium). The developed method was successfully applied for the analysis of captopril in dissolution tests of two commercially available batches.     

未衍生化卡托普利的毛细管电泳法测定

采用毛细管电泳高频电导法测定了未衍生化的卡托普利。考察了分离检测条件的影响。实验选择10．00mmoL／L Tris-5．0mmol／LH3BO3-20．0％CH3OH为电泳介质,在优化条件下,卡托普利的线性范围为1．00μg/mL-200μg／mL,检出限为0．3μg／mL。成功地检测了血清和尿液中的卡托普利。     

基于含氟表面活性剂修饰的金纳米粒子测定卡托普利

在较高离子强度和一定温度下,卡托普利能引起非离子表面活性剂FSN-100修饰的14nm金纳米粒子胶体溶液快速聚集,引起金纳米粒子在519nm处的吸光度降低,而在640nm处的相对吸光度成线性增加.据此,建立了一种光度测定卡托普利的新方法.卡托普利药片制剂中常见赋形剂,如淀粉、糊精、葡萄糖、果糖、麦芽糖、蔗糖、明胶、山梨醇、乳糖等对本实验没有干扰.本方法具有快速、简便、选择性高等优点,线性范围为2.0～12.5μg/mL,卡托普利检出限(S/N=3)为1.25μg/mL.该方法成功用于药片制剂中卡托普利的测定,回收率在99%到103%之间.     

修饰石墨电极表面电化学发光反应微环境的研究及其分析应用

用电化学方法对石墨电极表面进行预阳极化修饰后,该修饰电极不但能选择性地使卡托普利富集于修饰电极表面,而且还创造了一个适合于卡托普利显著增敏钌(Ⅱ)联吡啶体系的电化学发光信号的微环境。在优化的实验条件下,该方法的线性范围为2.0×10-8-8.0×10-6g/L,检出限达5.0×10-9g/L。该方法成功应用于尿样的检测。     

Captopril and its dimer captopril disulfide: comparative structural and conformational studies

The crystal structures of captopril {systematic name: (2S)‐1‐[(2S)‐2‐methyl‐3‐sulfanylpropanoyl]pyrrolidine‐2‐carboxylic acid}, C₉H₁₅NO₃S, (1), and its dimer disulfide metabolite, 1,1′‐{disulfanediylbis[(2S)‐2‐methyl‐1‐oxopropane‐3,1‐diyl]}bis‐L‐proline, C₁₈H₂₈N₂O₆S₂, (2), were determined by single‐crystal X‐ray diffraction analysis. Compound (1) crystallizes in the orthorhombic space group P2₁2₁2₁, while compound (2) crystallizes in the monoclinic space group P2₁, both with one molecule per asymmetric unit. The molecular geometries of (1) and (2) are quite similar, but certain differences appear in the conformations of the five‐membered proline rings and the side chains containing the sulfhydryl group. The proline ring adopts an envelope conformation in (1), while in (2) it exists in envelope and slightly deformed half‐chair conformations. The conformation adopted by the side chain is extended in (1) and folded in (2). A minimum‐energy conformational search using Monte Carlo methods in the aqueous phase reveals that the optimized conformations of the title compounds differ from those determined crystallographically, which depend on their immediate environment. Intermolecular O—H...O and relatively weak C—H...O interactions seem to be effective in both structures and, together with S—H...O and C—H...S contacts, they create three‐dimensional networks.     

Gold Nanoparticles/Biphenol–biphenoquinone for Ultra-trace Voltammetric Determination of Captopril

This study aims to synthesize gold nanoparticles/biphenol–biphenoquinone (AuNPs−BOH−BQ) and to study its application as a novel heterogeneous electron transfer mediator to modify carbon paste electrode (CPE/Au NPs−BOH−BQ) for ultra-trace determination of captopril (CP). Characterization results show well dispersed Au NPs with sizes in the range of 8.0–10.5 nm. Under optimized conditions, the calibration plot was linear from 1 to 5×10⁴ nM (two segments, 1–150 nM and 0.15–50.0 μM) and the detection limit was calculated to be 0.4 nM (S/N=3). Finally, the suggested sensor showed stable and reliable responses to CP in CP pharmaceutical tablet and urine samples.     

Characterisation of captopril photolysis and photocatalysis by-products in water by direct infusion,electrospray ionisation,high-resolution mass spectrometry and the assessment of their toxicities

Pharmaceuticals of different therapeutic classes are found in the environment. Captopril is used worldwide as an antihypertensive drug, and it has been found in the influent, effluent and secondary sludge of wastewater treatment plants. Advanced oxidation processes, such as direct photolysis (UV-C) and heterogeneous photocatalysis (TiO₂/UV-C), are alternatives to enhance mineralisation of pharmaceuticals and their removal during water treatment. In this article, it was evaluated the degradation of captopril in aqueous solution induced by UV-C and TiO₂/UV-C systems. The process focused on the identification and monitoring of the by-products formed under these conditions by applying direct-infusion electrospray ionisation high-resolution mass spectrometry in the negative ion mode (ESI(-)-HRMS) and high-performance liquid chromatography coupled to high-resolution mass spectrometry (HPLC/HRMS). To evaluate the by-products toxicity, acute ecotoxicity tests were performed with the crustacean Artemia salina, and the cytotoxicity was evaluated with (4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay using HepG2 cells. It was observed by ESI(-)-HRMS that after 120 min of light exposure, there was almost complete removal of captopril, with 93.5% removal efficiency during photolysis and 99.9% during photocatalysis. At these conditions, the rate of mineralisation, by total organic carbon (TOC), was only 2.92% for photolysis and 9.09% for photocatalysis, evidencing the formation of degradation by-products. Nine by-products of captopril photodegradation were identified, and their respective chemical structure elucidations were proposed. The treated samples were nontoxic to A. salina and HepG2 cells, indicating that both oxidative treatments (photocatalytic or photolytic processes) can be conveniently employed to remove captopril from aqueous media.     

Voltammetric Detection of Captopril Using Copper(II) and an Unmodified Glassy Carbon Electrode

We report a simple, sensitive, and rapid detection of captopril using copper(II) and a bare glassy carbon electrode with cyclic voltammetry. The captopril is detected by the formation of a copper(II)‐captopril complex that is observed to have a characteristic oxidation potential at+0.24 V vs. Ag/AgCl. It is found that the peak current varies linearly with the concentration of captopril. The linear dynamic range is obtained for a captopril concentration of 1 µM to 10 µM, and the sensitivity is found to be 0.10±0.003 μA μM^?1. Importantly, the low limit of detection (n=3) of 0.10 μM and the precision of 3.2 %, are achieved using a simple, unmodified electrode. This is attributable to in situ adsorption of a copper(II)‐captopril complex on the electrode surface.     

Compatibility studies between captopril and pharmaceutical excipients used in tablets formulations

Captopril (CAP) was the first commercially available angiotensine-converting enzyme (ACE) inhibitor. In the anti-hypertensive therapy is considered the selected drug has to be therapeutically effective together with reduced toxicity. CAP is an antihypertensive drug currently being administered in tablet form. In order to investigate the possible interactions between CAP and excipients in tablets formulations, differential scanning calorimetry (DSC) and thermogravimetric (TG) analysis completed by X-ray powder diffraction (XRPD) and Fourier transform infrared spectroscopy (FTIR) were used for compatibility studies. A possible drug-excipient interaction was observed with magnesium stearate by DSC technique.     

Binding Interaction of Captopril with Metal Ions: A Fluorescence Quenching Study

The binding interaction of captopril (CPL) with biologically active metal ions Mg²⁺, Ca²⁺, Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺ and Zn²⁺ was investigated in an aqueous acidic medium by fluorescence spectroscopy. The experimental results showed that the metal ions quenched the intrinsic fluorescence of CPL by forming CPL‐metal complexes. It was found that static quenching was the main reason for the fluorescence quenching. The quenching constant in the case of Cu²⁺ was highest among all quenchers, perhaps due to its high nuclear charge and small size. Quenching of CPL by metal ions follows the order Cu²⁺>Ni²⁺>Co²⁺>Ca²⁺>Zn²⁺>Mn²⁺>Mg²⁺. The quenching constant K_sv, bimolecular quenching constant K_q, binding constant K and the binding sites "n" were determined together with their thermodynamic parameters at 27 and 37°C. The positive entropy change indicated the gain in configurational entropy as a result of chelation. The process of interaction was spontaneous and mainly ΔS‐driven.