Solid-phase extraction followed by gas chromatography-mass spectrometry for the quantitative analysis of small molecule N-nitrosamine impurities in antitussive syrups.

A quantitative testing method was developed for the analysis of low molecular weight (small molecules) nitrosamine impurities in cough syrups using solid phase extraction (SPE) on strong cation-exchange functionalized polymeric sorbent cartridges followed by gas chromatography-mass spectrometry. The matrix spike recoveries of the nitrosamine impurities from the cough syrup samples was observed to be within the range of 90 %-120 %. Limit of detection (LOD) achieved for NNitrosodimethylamine (NDMA) and NNitroso morpholine (NMOR) was about 0.1 ng/mL while the LOD for NNitrosodiethylamine (NDEA), NNitrosodiisopropylamine (NDIPA) and NNitrosoisopropylethylamine (NIPEA) impurities was about 0.02 ng/mL. The method was evaluated and found to meet the acceptable criteria as per the ICH Q2 guidelines for a working concentration range of 0.02 ng/mL to 1.2 ng/mL for the analyzed impurities. The selectivity of the nitrosamine impurities against the presence of drug product was established using multiple reaction monitoring (MRM) transitions during analysis.

A validated stability­indicating reversed­phase­UPLC method for simultaneous estimation of promethazine hydrochloride, methylparaben, propylparaben and sodium benzoate assay of cough suppressant and antihistamine liquid oral dosage forms.

A quick, simple, sensitive, efficient and stability-indicating reverse-phase ultraperformance liquid chromatographic method for the estimation of propylparaben, methylparaben and sodium benzoate in a pharmaceutical liquid oral formulation was developed. A Waters Acquity UPLC BEH C18, 50 × 2.1 mm, 1.7 µm i.d. column was used to perform chromatographic separation with a 0.1% perchloric acid mobile phase used as solvent A and a mixture of 0.1 % perchloric acid and methanol in the ratio 20:80 (v/v), respectively, as solvent B. The experiments were carried out at a flow rate of 0.4 ml/min and the detection wavelength was 240 nm. The compartment temperature of the column was set at 40°C and the injection volume was set at 2 µl. The main aim of the research was to develop a single UPLC assay method for promethazine (active ingredient) and preservatives in the oral solution of promethazine HCl and dextromethorphan HBr that contains promethazine (active ingredient) and methylparaben, propylparaben and sodium benzoate (preservatives). An assay of dextromethorphan HBr was developed and validated by another HPLC method. The drug and preservatives were eluted at retention times of 19.3 min for promethazine HCl, 9.3 min for methylparaben, 18.9 min for propylparaben and 8.9 min for sodium benzoate. Validation of the developed method was carried out as stated by the International Conference on Harmonization guidelines ICH Q2B and under USP<1225>. The analytical parameters verified specificity/selectivity, linearity, accuracy, ruggedness and robustness. The linearity ranges of promethazine HCL, methylparaben, propylparaben and sodium benzoate were 10-100, 10-80, 1.0-8.0 and 10-80 µg/ml, respectively, with a correlation coefficient of active ingredients and preservatives of 1.00. Percentage recoveries of promethazine, propylparaben, methylparaben, and sodium benzoate were 100.0-100.2, 99.0-100.3, 99.5-98.0 and 99.0-100.0%. The validated analytical method proves that the method is specific, precise, linear, accurate, sensitive, rugged and stable, indicating the quantification of the active ingredient and all preservatives in liquid oral formulations.

An autopsy case of a young man with a single overdose of dextromethorphan.

Dextromethorphan (DXM) is an over-the-counter antitussive that is commonly used worldwide. Recently, DXM has become popular among young individuals because of its euphoric, hallucinogenic, and dissociative properties. Despite an increasing number of patients with DXM addiction, fatal cases of DXM poisoning are rare, and patients with fatalities often ingest DXM along with other drugs. Here, we report an autopsy case in which DXM was detected without multidrug ingestion. A man in his early twenties was found dead at home; no external injuries or obvious internal lesions were found during the autopsy. The toxicological analyses revealed extremely high concentrations of DXM, and no drugs other than DXM were detected. To the best of our knowledge, this is the first case report to describe a death caused by a single overdose of DXM in Japan. Public awareness regarding the risks associated with a massive ingestion of DXM should be increased.

A novel electrochemical sensor based on a Cu-coordinated molecularly imprinted polymer and MoS2 modified chitin-derived carbon for selective detection of dextromethorphan.

Dextromethorphan (DXM) is a widely utilized central antitussive agent, which is frequently abused by individuals seeking its recreational effect. But DXM overdose can cause some adverse effects, including brain damage, loss of consciousness, and cardiac arrhythmias, and hence its detection is significant. Herein, an electrochemical sensor based on a Cu-coordinated molecularly imprinted polymer (Cu-MIP) was fabricated for its detection. For constructing the sensor, nitrogen-doped carbon nanosheets (CCNs) were prepared through calcining chitin under an argon atmosphere, and molybdenum disulfide (MoS2) was allowed to grow on their surface. Subsequently, the obtained MoS2/CCNs composite was employed to modify a glassy carbon electrode (GCE), and the Cu-MIP was electrodeposited on the electrode in a Cu-1,10-phenanthroline (Cu-Phen) solution containing DXM, where Cu2+ played a role in facilitating electron transfer and binding DXM. Due to the large specific surface area, good electrocatalytic properties and recognition of the resulting composite, the resulting Cu-MIP/MoS2/CCNs/GCE showed high selectivity and sensitivity. Under optimized experimental conditions, the peak current of DXM and its concentration exhibited a good linear relationship over the concentration range of 0.1-100 µM, and the limit of detection (S/N = 3) was 0.02 µM. Furthermore, the electrochemical sensor presented good stability, and it was successfully used for the determination of DXM in pharmaceutical, human serum and urine samples.

Chemical profiling of Zhi-Ke-Bao pills and its potential mechanism against cough by ultra-high performance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry and network pharmacology.

Zhi-Ke-Bao pills (ZKB), a traditional Chinese medicine preparation composed of 13 herbs, is generally used to treat cough caused by external wind cold, phlegm, etc in clinical applications, and it plays a core role in relieving cough caused by COVID-19 and influenza in China. Till now, the understanding of its chemical constituents was dramatically limited due to its chemical complexity, restricting its clinical application or development. In this work, a developed ultra-high performance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry (UPLC-Q/TOF MS) method, a targeted and non-targeted strategy and network pharmacology were used to comprehensively characterize the chemical compositions in ZKB and predict its mechanism against cough. A total of 164 compounds (148 targeted compounds and 16 non-targeted ones) were identified or tentatively characterized in ZKB, including 65 flavonoids, 25 alkaloids, 19 organic acids, 41 saponins, 9 coumarins, 2 phenylpropanoids, 2 anthraquinones, and 1 other types. Among them, 37 compounds were unambiguously identified by comparison to reference standards. Meanwhile, the fragmentation behaviors of five main chemical structure types were also summarized. 309 targets and two core signaling pathways of ZKB against cough were predicted by network pharmacology, including MAPK and PI3K-Akt signaling pathways. It was the first time to characterize the chemical compounds of ZKB and reveal its potential mechanism against cough, providing the material basis for further quality control or pharmacodynamic evaluation of ZKB.

Novel HPTLC method for simultaneous estimation from ternary mixture of chlorpheniramine maleate, dextromethorphan hydrobromide and phenylephrine hydrochloride in syrup formulations.

OBJECTIVES: A synergic antihistamine, cough suppressant, and decongestant combination of chlorpheniramine, dextromethorphan, and phenylephrine is used to treat acute respiratory infections caused by seasonal viruses. The effective qualitative and quantitative methods require the simultaneous measurement of a ternary combination in the pharmaceutical syrup dosage form. Therefore, a new, simple, fast and robust high performance thin layer chromatographic (HPTLC) method has been developed and validated for chlorpheniramine maleate (CPM), dextromethorphan hydrobromide (DEXO) and phenylephrine hydrochloride (PE). MATERIAL AND METHODS: The chromatographic separation was carried out on precoated aluminium plates with silica gel 60 F254 as the stationary phase. Mobile phase used was chloroform: methanol: ammonia (2.5:7.5:0.3, v/v/v) for proper separation. The detection was carried out at 270nm wavelength in absorbance mode. Developed method was validated as per International Council for Harmonization (ICH) Q2 (R1) guideline. RESULTS: The linearity range is 400 to 1400ng/band for CPM, 3000 to 11500ng/band for DEXO and 1000 to 3500ng/band for PE with correlation coefficient ≥ 0.995. The consistent lower values of relative standard deviation (RSD, %) for precision and robustness study indicate the method reliability. The percent recovery ranged from 97.82 to 102.03% indicates the good accuracy of the method. CONCLUSION: The proposed method was complying for the analytical method validation parameters suggested by the ICH Q2 (R1) guideline. The method was found to be simple, rapid and reliable for the simultaneous estimation of CPM, DEXO and PE from its pharmaceutical syrup dosage form. The method was successfully applied to quantify these analytes from the several pharmaceutical syrup dosage form.

Analysis of inter-individual variability of antitussive effect of Farfarae Flos and its fecal metabolites based on gut microbiota.

In this study, the inter-individual variability of antitussive effect of Farfarae Flos was observed, and then the Farfarae Flos treated mice were divided into the mice with good or poor antitussive effect. Then a UHPLC-Q TOF-MS method was developed and validated to quantify 13 fecal metabolites of Farfarae Flos, and the results showed concentrated differences between the two subgroups. The results of 16 S rRNA gene sequencing analysis showed that mice with good or poor antitussive effects were also different at the structure of gut microbiota in phylum and genus, as well as the related 6 pathways. In addition, the differential fecal metabolites of Farfarae Flos between the two subgroups were probably related with 5 bacterial that participating in the CQAs and flavonoids metabolism. This study explained the inter-individual variability of the antitussive effect of Farfarae Flos from the perspective of gut microbiota. However, the specific bacterial that participate in the metabolism of Farfarae Flos as well as the antitussive effects of Farfarae Flos need to be further validated.

Utilization of N-bromosuccinimide for the sensitive spectrophotometric determination of pipazethate HCl as antitussive drug in pure and dosage forms.

OBJECTIVES: Three simple, sensitive, precise, reproducible and validated spectrophotometric methods have been developed for the quantification of pipazethate HCl as antitussive drug in pure and dosage forms. METHODS: The methods are based on utilization of N-bromosuccinimide as an oxidant and three dyes, amaranth, methylene blue, and indigo carmine, as auxiliary reagents. The proposed methods are based on oxidation reaction of pipazethate HCl with a known excess of N-bromosuccinimide in acid medium, followed by determination of unreacted N-bromosuccinimide by the reaction with a fixed amount of dyes, amaranth, methylene blue, and indigo carmine followed by the measurement of the absorbance at 520, 663 and 610nm, respectively. The optimization of the reaction conditions was investigated. RESULTS: Under the optimum conditions, linear relationships with good correlation coefficients (0.9998-0.9999) were found over the concentration ranges of 0.3-9.0, 0.5-12 and 0.5-10µgmL-1 with a limit of detection (LOD) of 0.1, 0.15 and 0.15µgmL-1 using amaranth, methylene blue, and indigo carmine methods, respectively. Intra-day and inter-day accuracy and precision of the methods have been evaluated. No interference was observed from the common tablet excipients. CONCLUSION: The developed methods were validated in accordance with ICH guidelines and successfully applied to the analysis of pipazethate HCl in dosage forms with good accuracy and precision. The reliability of the methods was further ascertained by performing recovery studies via the standard addition method. Statistical comparison of the results obtained by applying the proposed methods with those of the reported method by applying Student's t-test and variance ratio F-test at the 95% confidence level revealed good agreement and indicates no significant difference in accuracy and precision.

Characteristics, Properties and Analytical Methods for Determination of Dropropizine and Levodropropizine: A Review.

Dropropizine is a peripheral antitussive drug that acts by inhibiting cough reflex through its action on the peripheral receptors and their afferent conductors. It is marketed in a racemic form or its pure enantiomer called levodropropizine and both are available worldwide in various drug dosage formulations such as tablets, sirup and oral solution. Due to the widespread use of antitussives in the clinic it is necessary to develop efficient analytical methodologies for quality control and also for pharmacokinetic, bioavailability and bioequivalence studies. This review presents a survey of the characteristics, properties and analytical methods used for drug determination, being carried out through scientific articles as well as in official compendia. From the analyzed studies, the majority reports the use of HPLC/UV techniques for drug determination, but also spectrophotometric UV/Vis methods as well as gas chromatography, and voltammetric, potentiometric and conductometric titration methods. In addition, the methodologies addressed the determination of dropropizine or levodropropizine in different types of matrices such as raw material, pharmaceutical formulations, plasma and urine. Despite the extensive clinical use of dropropizine, data from this review evidenced a still limited number of studies dealing with analytical methods for its determination in different matrices, which may be of concern since the applicability of these methods is important for quality assurance, efficacy and safety of the medicine.

Green HPTLC and stability-indicating RP-HPLC for the assay of dextromethorphan hydrobromide and menthol in their lozenges.

Two chromatographic methods were developed for the assay of the FDA approved lozenges containing dextromethorphan hydrobromide (DXT) and menthol (MNT). The first was a green HPTLC method which uses a mobile phase of methanol-ammonia (10:0.1, v/v). The densitometric measurements of the spots which were retained at 0.28±0.01 for DXT and 0.76±0.02 for MNT was done at 210nm. The other method was RP-HPLC method with stability indicating merits at which a mixture of 20mM phosphate buffer pH 3 and acetonitrile as mobile phase in isocratic mode was used. The cited drugs were resolved in RP-HPLC method using isocratic elution using 20mM phosphate buffer: acetonitrile (65:35 v/v) with retention times of 2.21 and 3.47min for MNT and DXT, respectively and quantified using 215nm. Both methods were entirely validated and both methods were successfully able to analyze both drugs in presence of lozenges inactive ingredients. HPLC method had the advantage of being stability indicating at which resolution of the drugs from their forced degradation products was successfully attained. For HPTLC method, both drugs showed reasonable RF values when compared to rapidly eluted MNT in RP-HPLC; also it was more environmentally friendly than RP-HPLC as it used solvents which are less toxic and greener.

The chemical profile of active fraction of Kalimeris indica and its quantitative analysis.

Kalimeris indica (L) Sch-Bip is a medicinal plant used by the Miao ethnic group in the Guizhou province of China. It is widely used as a fresh vegetable to treat colds, diarrhea and gastric ulcers. However, few studies have been conducted on the mechanism of its effect on colds, and its quality control. The anticomplement and antitussive activities of different polar extracts of K. indica were evaluated. Fifty-nine compounds, mainly including phenols and flavonoids, were identified in K. indica extract by ultra-high-performance liquid chromatography quadrupole time-of-flight tandem mass spectrometry. A method was established through ultra-high-performance liquid chromatography with a photodiode array to simultaneously determine the anticomplement and antitussive activity of five compounds in K. indica combining chemical identification with chemometrics for discrimination and quality assessment. Also, 3,5-dicaffeoylquinic acid and 4,5-dicaffeoylquinic acid exhibited significantly higher anticomplementary activity than the other three compounds. The quantitative data were further analyzed by principal component analysis and orthogonal partial least-squares discriminant analysis. Heatmap visualization was conducted to clarify the distribution of the major compounds in different geographical origins. Screening pharmacological activities by a combination of chemometrics and chemical identification might be an effective method for the quality control of K. indica.

Identification of quality control markers in Suhuang antitussive capsule based on HPLC-PDA fingerprint and anti-inflammatory screening.

Suhuang antitussive capsule (SH), one of traditional Chinese patent medicines, has been widely used for treating cough variant asthma and postinfectious cough in clinic. The objective of this work is to identify the characteristic and active ingredients as the quality control markers for SH based on high performance liquid chromatography with photodiode array detector (HPLC-PDA) fingerprint and screening of anti-inflammatory components. Similarity analysis (SA), hierarchical clustering analysis (HCA) and principal component analysis (PCA) were used to evaluate 16 different batches of SH. 13 compounds accounting for 36% of the total components in the fingerprint were identified and semi-quantitatively analyzed, which anti-inflammatory activity was tested with the in vitro assay. The results showed that the established chemical fingerprint could clearly distinguish different batches of SH by SA, HCA, and PCA analysis. Furthermore, four known compounds (chlorogenic acid, schisandrin, angeloylgomisin H and praeruptorin A) were screened out to be the most discriminant variables, which could be applied to quality control of SH by quantitative analysis. The semi-quantitative results showed that six compounds were major components, i.e. arctiin (10.28 ±â€¯3.18 mg/g), ephedrine (9.26 ±â€¯1.58 mg/g), schisandrin (3.09 ±â€¯0.83 mg/g), pseudoephedrine (2.34 ±â€¯1.04 mg/g), schisandrin B (1.48 ±â€¯0.16 mg/g), and 1-caffeoylquinic acid (1.36 ±â€¯0.42 mg/g). The anti-inflammatory results showed that SH extract, praeruptorin A, schisandrin, arctigenin and pseudoephedrine could significantly inhibit inflammatory mediator NO production in LPS-stimulated RAW264.7 macrophages. These findings indicated that praeruptorin A, schisandrin, arctiin and pseudoephedrine could be proposed as the quality control markers for SH.

FT-IR Spectroscopy for the Detection of Diethylene Glycol (DEG) Contaminant in Glycerin-Based Pharmaceutical Products and Food Supplements.

Identification and determination of diethylene glycol (DEG) in glycerin-based products was successfully achieved using FT-IR spectroscopy. Studied samples included 0.5% to 20% by mass DEGspiked into cough syrup, two paracetamol syrup formulations, and two food supplements. The characteristic DEGwavenumbers at 881 cm-1 and 1083 cm-1 were used for its quantitative determination in the studied samples. A very good accuracy in determining the DEG fraction was achieved with a mean error% of ±2.02% to ±7.69% upon using the corrected absorbance at 881 cm-1. The corrected absorbance at 1083 cm-1 band was used in the case of paracetamol formulations and resulted in a mean error% ranging from ±2.50% to ±10.28%. The values of limit of detection of the current method ranged from 0.051% to 0.068% DEG for all studied samples.

Extraction-free spectrophotometric assay of the antitussive drug pentoxyverine citrate using sulfonephthalein dyes.

Pentoxyverine citrate (PEN-citrate) is an antitussive (cough suppressant) drug used for cough associated with illnesses like common cold. In this work, PEN-citrate is quantified by applying a simple, direct and accurate spectrophotometric method in pure form, pharmaceutical formulation (Cabella®, 2.13 mg/mL) and human serum samples. The formation of a stable yellow ion-pair with sulfonephthalein dyes; bromocresol green (BCG), bromophenol blue (BPB), bromothymol blue (BTB), bromocresol purple (BCP), bromochlorophenol blue (BChPB) and bromoxylenol blue (BXB), in three nonpolar solvents (chloroform, dichloromethane, acetonitrile) is used as the basis for this method. This is the first assay method reported for the quantification of PEN-citrate using the sulfonephthaleins as coloring agents. Diverse parameters were investigated in order to optimize the calibration curve conditions. The strategy was validated with respect to linearity range, precision, accuracy, specificity, robustness and limits of detection (LOD) and quantification (LOQ). In addition, solvents of different polarities were utilized to investigate the color reaction, light absorption and to allow for increasing the method sensitivity. Beer's law is obeyed over a wide concentration range (up to 42.05 µg/mL in case of BTB method). LOD and LOQ values reached 0.22 and 0.72 µg/mL, respectively, upon using BChPB. The relative standard deviation (%RSD) was ≤1.91% while correlation coefficient values (r) were ≥ 0.9974. High molar absorptivity values and low values of Sandell's sensitivity were obtained indicating that the proposed methods are highly sensitive. The validated methods were applied to the analysis of PEN-citrate in the dosage form and human serum samples where the drug was successfully resolved from the pharmaceutical additives and serum components with recoveries ≥98.98%.

Simultaneous Quantification of Chlorpheniramine, Phenylephrine, Guaifenesin in Presence of Preservatives with Detection of Related Substance Guaiacol in their Cough Syrup by RP-HPLC and TLC-Densitometric Methods.

Two sensitive chromatographic methods have been developed, and validated for chlorpheniramine maleate (CM), phenylephrine (PE) and guaifenesin (GF) determination in their mixture and in presence of GF related substance guaiacol (GL) and preservative namely; sodium benzoate (NaB). The first method was based on thin layer chromatographic separation (TLC) followed by densitometric determination of the separated spots. The separation was achieved using silica gel 60 F254 TLC plates and ethyl acetate: methanol: toluene: ammonia (7:1.5:1:0.5, by volume) as a developing system. Densitometric quantification of the three drugs was carried by the reflectance mode at 270 nm. The second method was based on the use of high-performance liquid chromatography with diode array detection, by which the proposed components were separated on a reversed phase C18 analytical column using phosphate buffer pH 2.9 (containing 0.1 g Heptane-1-sulphonic acid sodium salt) and acetonitrile (85:15, v/v) at 0.8 mL/min for 4 minutes then 1 mL/min till end of the run using flow rate online switching technique. Both methods were validated according to the ICH guidelines and successfully applied for the determination of CM, PE, and GF in pure powder and in combined cough syrup without interference from the excipients.

Phytochemical standardization of Vasicinein cough syrup by high performance liquid chromatography-densitometry.

The highly oriented modern detection techniques provide a precise and definite tool for investigation in natural medicines. Current study directed the standardization of eminent biomarker Vasicine in a natural cough syrup. A highly accurate and precise method of High-performance thin layer chromatography (HPTLC) has been developed to certify the quantity of vasicine inside the syrup. Ethyl acetate, chloroform, ethanol and ammonia (6:3:1: 1 v/v) were mobile phase for the study. The TLC plate silica gel G60F254 was used with CAMAG Scanner III and CAMAG Linomate 5. The detected Rf value was 0.51 in both sample and reference standard at 254 nm. International conference of Harmonization (ICH) guidelines were followed for the validation of the developed method. Linearity was achieved in the range of 200µg to 1600µg with co-efficient correlation r2=0.9995. Accuracy was found in between 98.9 to 101.4% however precision was good at both inter and intra-day. As per the standardization of ICH, the developed method was found to be reproducible and showed sharp similar peak with high resolution.

Anti-allergy and anti-tussive activity of Clitoria ternatea L. in experimental animals.

ETHNOPHARMACOLOGICAL RELEVANCE: Clitoria ternatea flower is traditionally used in the treatment of respiratory disorders including bronchitis and is one of the ingredients in different Ayurvedic preparations that are used in respiratory disorders. However, till date there is no scientific report on the anti-asthmatic activity of this flower. AIM OF THE STUDY: Ethanolic extract of Clitoria ternatea flowers (ECT) was evaluated for its anti-allergy and anti-tussive potential in experimental animals. Additionally, the anti-inflammatory potential of ECT was carried out to draw a plausible mechanism of action of the drug. MATERIALS AND METHODS: In-vitro anti-asthmatic activity of ECT was evaluated in goat tracheal chain and isolated guinea pig ileum preparations. Acute and chronic anti-asthmatic activity of ECT (100, 200 and 400 mg/kg; p.o.) was estimated in histamine aerosol exposed guinea pigs and in OVA sensitized and challenged mice respectively. Anti-tussive activity of ECT (100, 200 and 400 mg/kg; p.o.) was evaluated against sulfur dioxide- and citric acid-induced cough in experimental animals. Moreover, the anti-inflammatory activity of ECT (100, 200 and 400 mg/kg; p.o.) was evaluated against carrageenan- and acetic acid-induced inflammation in rats. RESULTS: ECT attenuated histamine-induced contraction in both goat tracheal chain and isolated guinea pig ileum preparations. ECT (400 mg/kg) attenuated histamine-induced dyspnoea and OVA-induced changes in differential cell count in broncheoalveolar fluid, levels of interleukins (IL-1beta and IL-6) and immunoglobulin (OVA-sensitive IgG1) in animals. ECT (400 mg/kg) further ameliorated sulfur dioxide- and citric acid-induced cough in experimental animals. Additionally, ECT (400 mg/kg) attenuated inflammation in carrageenan and acetic acid challenged rodents. CONCLUSIONS: Standardized ECT could be considered as a potential therapeutic alternative in the management of allergy-induced asthma.

Novel Approach for the Simultaneous Determination of Carbinoxamine Maleate, Pholcodine, and Ephedrine Hydrochloride Without Interference from Coloring Matter in an Antitussive Preparation Using Smart Spectrophotometric Methods.

The presence of coloring matters in syrups usually interferes with the spectrophotometric determination of active pharmaceutical ingredients. A novel approach was introduced to eliminate the interference of sunset yellow (coloring matter) in Cyrinol syrup. Smart, simple, accurate, and selective spectrophotometric methods were developed and validated for the simultaneous determination of a ternary mixture of carbinoxamine maleate, pholcodine, and ephedrine hydrochloride in syrup. Four of the applied methods used ratio spectra: successive derivative subtraction coupled with constant multiplication, successive derivative of ratio spectra, ratio subtraction coupled with ratio difference, and ratio spectra continuous wavelet transforms zero-crossing. In addition, a method that was based on the presence of an isosbestic point, the amplitude summation method, was also established. A major advantage of the proposed methods is the simultaneous determination of the mentioned drugs without prior separation steps. These methods were successfully applied for the determination of laboratory-prepared mixtures and a commercial pharmaceutical preparation without interference from additives, thus proving the selectivity of the methods. No significant difference regarding both accuracy and precision was observed upon statistical comparison of the results obtained by the proposed methods with each other and with those of official or reported ones.

Multi-energy calibration applied to atomic spectrometry.

Multi-energy calibration (MEC) is a novel strategy that explores the capacity of several analytes of generating analytical signals at many different wavelengths (transition energies). Contrasting with traditional methods, which employ a fixed transition energy and different analyte concentrations to build a calibration plot, MEC uses a fixed analyte concentration and multiple transition energies for calibration. Only two calibration solutions are required in combination with the MEC method. Solution 1 is composed of 50% v v-1 sample and 50% v v-1 of a standard solution containing the analytes. Solution 2 has 50% v v-1 sample and 50% v v-1 blank. Calibration is performed by running each solution separately and monitoring the instrument response at several wavelengths for each analyte. Analytical signals from solutions 1 and 2 are plotted on the x-axis and y-axis, respectively, and the analyte concentration in the sample is calculated from the slope of the resulting calibration curve. The method has been applied to three different atomic spectrometric techniques (ICP OES, MIP OES and HR-CS FAAS). Six analytes were determined in complex samples (e.g. green tea, cola soft drink, cough medicine, soy sauce, and red wine), and the results were comparable with, and in several cases more accurate than, values obtained using the traditional external calibration, internal standardization, and standard additions methods. MEC is a simple, fast and efficient matrix-matching calibration method. It may be applied to any technique capable of simultaneous or fast sequential monitoring of multiple analytical signals.

Development and validation of a generic high-performance liquid chromatography for the simultaneous separation and determination of six cough ingredients: Robustness study on core-shell particles.

A generally applicable high-performance liquid chromatographic method for the qualitative and quantitative determination of pharmaceutical preparations containing phenylephrine hydrochloride, paracetamol, ephedrine hydrochloride, guaifenesin, doxylamine succinate, and dextromethorphan hydrobromide is developed. Optimization of chromatographic conditions was performed for the gradient elution using different buffer pH values, flow rates and two C18 stationary phases. The method was developed using a Kinetex® C18 column as a core-shell stationary phase with a gradient profile using buffer pH 5.0 and acetonitrile at 2.0 mL/min flow rate. Detection was carried out at 220 nm and linear calibrations were obtained for all components within the studied ranges. The method was fully validated in agreement with ICH guidelines. The proposed method is specific, accurate and precise (RSD% < 3%). Limits of detection are lower than 2.0 µg/mL. Qualitative and quantitative responses were evaluated using experimental design to assist the method robustness. The method was proved to be highly robust against 10% change in buffer pH and flow rate (RSD% < 10%), however, the flow rate may significantly influence the quantitative responses of phenylephrine, paracetamol, and doxylamine (RSD% > 10%). Satisfactory results were obtained for commercial combinations analyses. Statistical comparison between the proposed chromatographic and official methods revealed no significant difference.