Sensitive determination of erdosteine in human plasma by use of automated 96-well solid-phase extraction and LC–MS/MS

Multiple green spectroscopic methods for erdosteine determination in bulk and dosage form with extensive greenness evaluation

Four simple, sensitive, economical, and eco-friendly spectrophotometric and spectrofluorimetric methods for the assay of erdosteine (ERD) in bulk and dosage form have been developed and validated as per the current ICH guidelines. Method I involved the addition of the powerful oxidizing agent, potassium permanganate to ERD and measuring the oxidation product at 600 nm. Another oxidizing agent; ceric ammonium sulfate was used in Method II where ERD is oxidized resulting in a decline in the absorbance intensity of cerium (IV) ions, measured at 320 nm. Similarly, Method III employed the use of ceric ammonium sulfate, However, the fluorescence intensity of the resulting cerium (III) ions was recorded at λex/λem 255/355 nm, respectively. Whereas in Method IV, ERD was added to acriflavine leading to a proportional decrease in its native fluorescence. Various reaction conditions affecting the intensity of measurement were attentively investigated, optimized, and validated. All the suggested methods did not require any tedious extraction procedures nor organic solvents. The implementation of the proposed methods in ERD assay resulted in linear relationships between the measured signals and the corresponding concentrations of ERD in the range of 1-6, 0.1-1.0, 0.01-0.1, and 10-100 μg/mL with LOD values 0.179, 0.024, 0.0027 and, 3.2 μg/mL for methods I, II, III and IV respectively. The suggested methods were successfully applied to ERD analysis in pure form and in commercial capsules. Furthermore, the eco-friendliness of the proposed methods was thoroughly checked using various greenness testing tools. Lastly, this work, not only presents highly sensitive, green, mix-and-read methods for ERD determination, but also, describes the determination of ERD spectrofluorimetrically for the first time in the literature.

A rapid and sensitive UPLC–MS/MS method for quantification of erdosteine as bulk drug and in capsules as dosage forms

A rapid, sensitive, specific ultra-performance liquid chromatography-tandem mass spectrometric (UPLC-MS-MS) method was developed for the determination of erdosteine (ERD) in pharmaceutical preparations. The chromatographic separation was achieved with 0.1% formic acid in combination with acetonitrile (25:75 v/v) using C18 UPLC column, 95Å, 2.1 x 50 mm, 1.8 µm. The flow rate was 0.15 mL/min and the total run time was 2.0 min. The column temperature was kept constant at 40 °C and the injection volume was 5 μL. Ibuprofen was used as internal standard (IS). The mass transitions of ERD and IS were m/z 249.9 → 231.8 and 205.1 → 161.0. Also, another product ion of ERD (m/z 249.80 → 231.80) was monitored as predictive ion during the analysis. The standard calibration curve shows determination coefficient (R2) greater than 0.996 with a range of 1-5000 ng/mL using the linear regression model. Within-run precision and between-run repeatability were expressed as relative standard deviation and were lower than 5%. The developed method was successfully applied in the analysis of ERD-containing capsule formulation indicating that the method could be used for routine quality control analyses. Keywords: erdosteine, UPLC-MS/MS, multiple reaction monitoring, pharmaceutical analysis, method validation

Determination, Isolation, and Identification, of Related Impurities in Erdosteine Bulk Drug

BACKGROUND

Erdosteine is a mucolytic drug and has antioxidant activity.

OBJECTIVE

To develop a HPLC method for determination of erdosteine and its impurities in erdosteine bulk drug and identify the main impurities to help improve the quality of erdosteine bulk drug.

METHOD

The chromatographic separations were performed on a CAPCELL PAK C18 column (4.6 mm × 250 mm i.d., 5 μm). Acetonitrile-0.01 mol/L citric acid solution (13:87, v/v) pumped at a flow rate of 1.0 mL/min was used as the mobile phase. Detection wavelength was 254 nm. Two main impurities in erdosteine bulk drug were enriched by ODS column chromatography and oxidative degradation, respectively, and then both were purified by semi-preparative HPLC. At last, their structures were identified by a variety of spectral data (MS, 1H NMR and 13C NMR).

RESULTS

Good separations for erdosteine and its related impurities were observed. A new impurity was confirmed as ethyl ({2-oxo-2-[(2-oxotetrahydro-3-thiophenyl) amino] ethyl} sulfanyl) acetate, which was erdosteine ethyl ester, and produced in the refining process of erdosteine bulk drug when using ethanol as refining solvent. Another impurity was confirmed as ({2-Oxo-2-[(2-oxotetrahydro-3-thiophenyl) amino] ethyl} sulfinyl) acetic acid, which was an erdosteine oxide.

CONCLUSIONS

A HPLC method for determination of erdosteine and its related impurities is developed and validated. Two main impurities in erdosteine bulk drug were isolated and identified. Avoiding ethanol as refining solvent can improve the purity of erdosteine bulk drug.

HIGHLIGHTS

A new process related impurity and an oxidative degradation impurity in erdosteine bulk drug were isolated and identified.

Simultaneous determination of cefixime and erdosteine in combined dosage form using validated spectrophotometric methods

Four accurate and precise spectrophotometric methods were developed and validated for the simultaneous determination of a binary mixture of cefixime (CEF) and erdosteine (ERD) without previous separation. Method A was first derivative ratio spectrophotometric method (¹DD) where the amplitudes at 310 and 315 nm and the amplitude at 248 nm were chosen to simultaneously estimate CEF and ERD, respectively. Method B depends on ratio difference spectrophotometry (RDSM), in which the difference in amplitudes at 325 and 326 nm on the ratio spectrum of the mixture was directly proportional to the concentration of CEF; independent of the interfering component. Similarly, the amplitude difference between 236 and 249 nm on the ratio spectrum was used for the determination of ERD. Method C was based on simultaneous determination of CEF and ERD using classical least squares (CLS) and partial least squares (PLS) chemometric techniques. Method D was the mean centering of ratio spectra (MCR) at 313 and 237 nm for the determination of CEF and ERD respectively. The developed methods were successfully employed to the determination of CEF and ERD in laboratory prepared mixtures and dosage form showing satisfactory recoveries. Methods validation was performed according to the International Conference on Harmonization (ICH) guidelines. The obtained results were statistically compared to those of the reference method, revealing no significant difference with respect to precision and accuracy. Precision and cost effectiveness of the developed methods permit their application in quality control laboratories for the determination of the binary mixture.

Ultrafast liquid chromatographic analysis of erdosteine in human plasma based on fluorimetric detection and precolumn derivatization with 4-bromomethyl-7-methoxycoumarin: Application to pharmacokinetic studies

In this study, a new analytical method for erdosteine (ERD) in plasma based on high-performance liquid chromatography and a fluorimetric detector, is presented. Precolumn derivatization of ERD with 4-bromomethyl-7-methoxy coumarin (BrMmC) and dibenzo-18-crown-6-ether as a reaction catalyst led to the production of a fluorescent compound. ERD was monitored by fluorescence with an excitation wavelength λ_ext. = 325 nm and emission wavelength λ_em. = 390 nm. Optimum reaction conditions were carefully studied and optimized. A chromatographic procedure was performed using a C18 column of 150 × 4.6 mm and 3 μm particle size and a mobile phase consisting of methanol:acetonitrile:water (30:30:40, v/v/v) under a flow rate of 0.5 ml min^-1 . A calibration plot was established covering analyte concentration range 0.2-3.0 μg ml^-1 ; the detection limit was 0.015 μg ml^-1 and quantification limit was 0.05 μg ml^-1 . Mean recovery was 87.33% and relative standard deviation was calculated to be less than 4.4%. The developed method was successfully used to determine pharmacokinetic preparations of ERD subsequent to administration of a 900 mg dose capsule to a healthy 40-year-old woman volunteer.

Recent developments in extraction procedures relevant to analytical toxicology

Sample preparation is an important step in the development of an analytical method but is often regarded as time-consuming, laborious work. Optimum sample preparation leads to enhanced selectivity and sensitivity, however, and reduces amounts of interfering matrix compounds, resulting in less signal suppression or enhancement. Recent developments in extraction techniques that could be of interest in clinical and forensic toxicology, for example liquid-liquid, solid-phase, and headspace extraction, are summarized in this review. The advantages and disadvantages of several extraction techniques are discussed, to enable the reader to choose an appropriate method of extraction for his or her application. Attention is paid to current trends in analytical toxicology, for example miniaturization, high throughput, and automation.