Simultaneous determination of caffeine, paracetamol, and ibuprofen in pharmaceutical formulations by high-performance liquid chromatography with UV detection and by capillary electrophoresis with conductivity detection

High performance liquid chromatographic method optimized by Box-Behnken design model to determine caffeine in pharmaceutical preparations and urine samples

A UV-HPLC method optimized by Box-Behnken design model was developed to determine caffeine in pharmaceutical preparations and urine samples. The chromatographic conditions followed were mobile phase: methanol/water/ citrate buffer (pH 4.6) (40:25:35, v/v/v),AcclaimTMDionex C18 column (ODS 100A˚, 5 µm; 4.6 × 250 mm),flow rate (0.9 mL min-1), column temperature (30 °C) and UV-detection wavelength (204 nm). The chromatographic variables: pH (A), % methanol fraction (B), flow rate(C) and column temperature (D) were optimized at 50 μg mL-1caffeine using BBD model. The chromatogram resulted in the asymmetry factor (1.23), theoretical plate 13,786 and retention time (5.79 min). The proposed HPLC method's greenness point was assessed byAnalytical Eco-scale and found to be 78 (as per guidelines, ranked as excellent). The linearity was ranged from2.0 to 70 µg mL-1 with coefficient of correlation (r = 0.999) and detection limit of 0.19 µg mL-1. The proposedmethod was developed successfully and applied for the assay of active caffeine in pharmaceutical preparations and urine samples. The % recovery obtained by both (proposed and reference) methods ranged from 99.98 to 100.05 % followed the compliance (100 ± 2 %) with Canadian Health Protection regulatory guidelines. The performance of the proposed method was compared with published papers and found to be acceptable and superior. The proposed method was quite effective as the reference method, and hence can be used as an alternative method for the assay of active caffeine in pharmaceutical preparations and urine samples.

Smart green spectrophotometric assay of the ternary mixture of drotaverine, caffeine and paracetamol in their pharmaceutical dosage form

Three green and facile spectrophotometric methods were developed for the assay of Petro® components; drotaverine HCl (DRT), caffeine (CAFF), and paracetamol (PAR). The three methods depend on measuring the absorbance of the studied drugs through their ethanolic solution. The first derivative spectrophotometry (FDS) at (Δλ = 10) were good parameters for DRT and CAFF resolution; DRT and CAFF could be well calibrated using FDS at 320 and 285 nm, respectively. PAR could be estimated at 308 nm utilizing the second derivative spectrophotometry (SDS). Method II relies on the double divisor ratio derivative spectroscopy (DDRDS). The first derivative was applied on each drug where they would be assayed at 309, 288, and 255 nm for DRT, CAFF, and PAR, respectively. Method III depends on the mean centering (MCR) technique. DRT, CAFF, and PAR could be determined at 309, 214, and 248 nm, respectively. The concentrations were rectilinear in the ranges of 2-20 µg/mL for DRT, 1.5-15 µg/mL for CAFF, and 2-40 µg/mL for PAR in double devisor and mean centering but PAR from 5 to 40 µg/mL in derivative method. Method validation was performed according to ICH guidelines assured by the agreement with the comparison method. In addition, greenness assessment of the proposed methods was investigated. The application of the proposed method was extended to analyse tablet dosage form and performing invitro dissolution testing.

A Simple Stability-Indicating UPLC Method for the Concurrent Assessment of Paracetamol and Caffeine in Pharmaceutical Formulations

A fixed-dose combination of paracetamol (PCM) and caffeine (CAF) tablets/capsules is the most frequently used over-the-counter medicine for fever and headache. In this paper, a simple, reliable, sensitive, rapid, and stability-indicating ultra-performance liquid chromatography (UPLC) analytical method was proposed for simultaneously assessing PCM and CAF in pharmaceutical formulations. The UPLC method was developed on an Acquity UPLC® CSHTM C18 column, and the column oven temperature was maintained at 35 ± 5 °C with isocratic elution by using a solution of methanol and water (30:70, v/v). The maximum absorbance of PCM and CAF was observed at 272.5 nm. The flow rate was 0.2 mL/min, and the injection volume was 1 µL, with the total run time of 2 min for the separation of PCM and CAF. The proposed UPLC method was validated according to the ICH guidelines, and it demonstrated excellent linearity, with correlation coefficients of 0.9995 and 0.9999 over the concentration ranges of 40–400 and 7–70 ng/mL for PCM and CAF, respectively. The mean retention times of 0.82 ± 0.0 and 1.16 ± 0.02 were observed for PCM and CAF, respectively. The limits of detection and quantification were 16.62 and 3.86 for PCM, respectively, and 50.37 and 11.70 for CAF, respectively. PCM and CAF were subjected to acidic, alkali, oxidative, phytochemical, dry-heat, and wet-heat degradation. The method was found to well separate the analytes’ peaks from degradation peaks, with no alterations in retention times. The proposed method is linear, precise, accurate, specific, and robust, and it can indicate stability and be used for the quantitative assessment of pharmaceutical formulations comprising PCM and CAF within a short period of time.

Simultaneous Voltammetric Determination of Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) Using a Modified Carbon Paste Electrode and Chemometrics

This work presents the simultaneous quantification of four non-steroidal anti-inflammatory drugs (NSAIDs), paracetamol, diclofenac, naproxen, and aspirin, in mixture solutions, by a laboratory-made working electrode based on carbon paste modified with multi-wall carbon nanotubes (MWCNT-CPE) and Differential Pulse Voltammetry (DPV). Preliminary electrochemical analysis was performed using cyclic voltammetry, and the sensor morphology was studied by scanning electronic microscopy and electrochemical impedance spectroscopy. The sample set ranging from 0.5 to 80 µmol L^-1 was prepared using a complete factorial design (3⁴) and considering some interferent species such as ascorbic acid, glucose, and sodium dodecyl sulfate to build the response model and an external randomly subset of samples within the experimental domain. A data compression strategy based on discrete wavelet transform was applied to handle voltammograms' complexity and high dimensionality. Afterward, Partial Least Square Regression (PLS) and Artificial Neural Networks (ANN) predicted the drug concentrations in the mixtures. PLS-adjusted models (n = 12) successfully predicted the concentration of paracetamol and diclofenac, achieving correlation values of R ≥ 0.9 (testing set). Meanwhile, the ANN model (four layers) obtained good prediction results, exhibiting R ≥ 0.968 for the four analyzed drugs (testing stage). Thus, an MWCNT-CPE electrode can be successfully used as a potential sensor for voltammetric determination and NSAID analysis.

Rapid determination of NSAIDs by capillary and microchip electrophoresis with capacitively coupled contactless conductivity detection in wastewater

A simple, rapid method using CE and microchip electrophoresis with C⁴ D has been developed for the separation of four nonsteroidal anti-inflammatory drugs (NSAIDs) in the environmental sample. The investigated compounds were ibuprofen (IB), ketoprofen (KET), acetylsalicylic acid (ASA), and diclofenac sodium (DIC). In the present study, we applied for the first time microchip electrophoresis with C⁴ D detection to the separation and detection of ASA, IB, DIC, and KET in the wastewater matrix. Under optimum conditions, the four NSAIDs compounds could be well separated in less than 1 min in a BGE composed of 20 mM His/15 mM Tris, pH 8.6, 2 mM hydroxypropyl-beta-cyclodextrin, and 10% methanol (v/v) at a separation voltage of 1000-1200 V. The proposed method showed excellent repeatability, good sensitivity (LODs ranging between 0.156 and 0.6 mg/L), low cost, high sample throughputs, portable instrumentation for mobile deployment, and extremely lower reagent and sample consumption. The developed method was applied to the analysis of pharmaceuticals in wastewater samples with satisfactory recoveries ranging from 62.5% to 118%.

Research on Detection of Sterol Doping in Sports by Electrochemical Sensors: A Review

The use of doping by athletes to improve performance is prohibited. Therefore, doping testing is an important step to ensure fairness in sports. Doping is gradually metabolized in the body and is therefore difficult to detect immediately by a common method. At the same time, the emergence of new doping agents poses a challenge for highly sensitive detection. Electrochemical sensors are a fast, highly sensitive, and inexpensive analytical detection technology. It provides qualitative and quantitative determination of analytes by altering the electrochemical signal of the analyte or probe at the electrode. In this min-review, we summarized the different electrochemical sensing strategies for sterol doping detection. Some of the representative papers were interpreted in detail. In addition, we compare different sensing strategies.

Enhanced Sample Throughput Capillary Zone Electrophoresis with UV Detection in Hydrodynamically Closed System for Determination of Ibuprofen

A simple analytical approach based on capillary zone electrophoresis with ultraviolet detection and repeated sample injection strategy (applied in a hydrodynamically closed separation system for the first time) was developed for the determination of ibuprofen (IBU) in commercially available pharmaceutical preparations. The proposed method was characterized by significantly increased sample throughput and favorable validation parameters, highly demanded in routine quality control laboratories. The limit of detection was predicted at the concentration level of 0.31 µg/mL. Intra-day precision expressed as the relative standard deviation of IBU concentration ranged from 1.9 to 5.6%, and corresponding intra-day accuracy expressed as the relative error was in the interval of 87.1–106.5%. Inter-day precision was in the range of 2.6–15.0%, and inter-day accuracy was 94.9–102.7%. The developed method was able to quantify IBU in complex pharmaceutical matrices represented by commercially available tablets and oral suspension. The determined contents of IBU in the tested dosage forms were in good agreement with the manufacturer’s declaration. The analytical performance of the developed method was evaluated according to the innovative RGB Additive Color Model strategy. It was demonstrated that the proposed method is characterized by very good analytical performance parameters, safety and eco-friendliness, and practical effectiveness.

Simultaneous Determination of Paracetamol, Ibuprofen, and Caffeine in Tablets by Molecular Absorption Spectroscopy Combined with Classical Least Square Method

In this paper, the classical least-squares (CLS) method with molecular absorption spectrophotometric measurement was used to determine simultaneously paracetamol (PAR), ibuprofen (IBU), and caffeine (CAF) in tablets. The absorbance spectra of the standard solutions and samples were measured over a wavelength from 220 to 300 nm with a 0.5 nm step. The concentration of PAR, IBU, and CAF in the sample solutions was calculated by using Visual Basic for Applications (VBA) and a program called CLS-Excel written in Microsoft Excel 2016. The method and the CLS-Excel program were tested on mixed standard laboratory samples with different PAR, IBU, and CAF concentration ratios, and they showed only small errors and a satisfying repeatability. An analytical procedure for tablets containing PAR, IBU, and CAF was developed. The reliability of the procedure was proved via the recovery and repeatability of the analysis results with an actual tablet sample and by comparing the mean contents of active substances in the tablets obtained from the analytical procedure with the HPLC method. The procedure is simple with a reduced cost compared with the HPLC standard method.

In-situ fabrication of polypyrrole composite with MoO3: An effective interfacial charge transfers and electrode materials for degradation and determination of acetaminophen

Pharmaceutical wastes, acetaminophen (AP) widely used in medical fields, is often discharged into water, causing harm to human health. Hence, there is an urgent need to effectively remove AP from wastewater systems. In this paper, polypyrrole (PPy) composite with MoO₃ has been synthesized via an in-situ polymerization method. The as-prepared materials were thoroughly characterized by XRD, FT-IR, UV-DRS, SEM, TEM and mapping techniques. The as-prepared MoO₃@PPy composite was utilized to removal of AP via photocatalytic degradation and electrochemical determination. Under optimized composite, MoO₃@PPy (2) showed an excellent photocatalytic degradation and electrochemical determination of AP compared to pure MoO₃ and all other composites. The higher catalytic activity was ascribed to the effective interfacial charges transfer, reduce the recombination and enhance the active surface area of electrode via a synergistic effect. The photocatalytic degradation mechanism, rate and kinetic of the reaction were investigated and discussed. The major active degradation species and an effective charge transfer properties were confirmed by trapping experiments and photocurrent spectra. In addition, the MoO₃@PPy (2) modified GCE exhibit the AP determination activity by DPV with a linear range of 0.05-546 μM. The limit of detection and sensitivity of electrode were 0.0007 μM and 0.242 μM^-1 cm^-2 respectively. Moreover, the proposed electrode showed good selectivity, stability and reproducibility. This method was useful for the determination of AP in real samples.

Simultaneous Determination of Caffeine and Paracetamol in Commercial Formulations Using Greener Normal-Phase and Reversed-Phase HPTLC Methods: A Contrast of Validation Parameters

There has been no assessment of the greenness of the described analytical techniques for the simultaneous determination (SMD) of caffeine and paracetamol. As a result, in comparison to the greener normal-phase high-performance thin-layer chromatography (HPTLC) technique, this research was conducted to develop a rapid, sensitive, and greener reversed-phase HPTLC approach for the SMD of caffeine and paracetamol in commercial formulations. The greenness of both techniques was calculated using the AGREE method. For the SMD of caffeine and paracetamol, the greener normal-phase and reversed-phase HPTLC methods were linear in the 50–500 ng/band and 25–800 ng/band ranges, respectively. For the SMD of caffeine and paracetamol, the greener reversed-phase HPTLC approach was more sensitive, accurate, precise, and robust than the greener normal-phase HPTLC technique. For the SMD of caffeine paracetamol in commercial PANEXT and SAFEXT tablets, the greener reversed-phase HPTLC technique was superior to the greener normal-phase HPTLC approach. The AGREE scores for the greener normal-phase and reversed-phase HPTLC approaches were estimated as 0.81 and 0.83, respectively, indicated excellent greenness profiles for both analytical approaches. The greener reversed-phase HPTLC approach is judged superior to the greener normal-phase HPTLC approach based on numerous validation parameters and pharmaceutical assays.

Fast determination of paracetamol and its hydrolytic degradation product p-aminophenol by capillary and microchip electrophoresis with contactless conductivity detection

Paracetamol (PAC) is one of the most extensively used analgesics and antipyretic drugs to treat mild and moderate pain. P-aminophenol (PAP), the main hydrolytic degradation product of PAC, can be found in environmental water. Recently, capillary electrophoresis (CE) has been developed for the detection of a wide variety of chemical substances. The purpose of this study is to develop a simple and fast method for the detection and separation of PAC and its main hydrolysis product PAP, using CE and microchip electrophoresis (ME) with capacitively coupled contactless conductivity detection (C⁴ D). The determination of these compounds using ME with C⁴ D is being reported for the first time. The separation was run for all analytes using a background electrolyte (BGE) (20 Mm β-alanine, pH 11) containing 14% (v/v) methanol. The RSDs obtained for migration time were less than 0.05%, and RSDs obtained for peak area were less than 3%. The detection limits (S/N = 3) that were achieved ranged from 0.3 to 0.6 mg/L without sample preconcentration. The presented method showed rapid analysis time (less than 1 min), high efficiency and precision, low cost, and a significant decrease in the consumption of reagents. The microchip system has proved to be an excellent analytical technique for fast and reliable environmental applications. This article is protected by copyright. All rights reserved.

Electrochemical determination of acetaminophen at a carbon electrode modified in the presence of β-cyclodextrin: role of the activated glassy carbon and the electropolymerised β-cyclodextrin

Acetaminophen is a well-known drug commonly used to provide pain relief, but it can also lead to acute liver failure at high concentrations. Therefore, there is considerable interest in monitoring its concentrations. Sensitive and selective acetaminophen electrochemical sensors were designed by cycling a glassy carbon electrode (GCE) to high potentials in the presence of β-CD in a phosphate electrolyte, or by simply activating the GCE electrode in the phosphate solution. Using cyclic voltammetry, adsorption-like voltammograms were recorded. The acetaminophen oxidation product, N-acetyl benzoquinone imine, was protected from hydrolysis, and this was attributed to the adsorption of acetaminophen at the modified GCE. The rate constants for the oxidation of acetaminophen were estimated as 4.3 × 10–3 cm2 s–1 and 3.4 × 10–3 cm2 s–1 for the β-CD-modified and -activated electrodes, respectively. Using differential pulse voltammetry, the limit of detection was calculated as 9.7 × 10–8 M with a linear concentration range extending from 0.1 to 80 μM. Furthermore, good selectivity was achieved in the presence of caffeine, ascorbic acid and aspirin, enabling the determination of acetaminophen in a commercial tablet. Similar electrochemical data were obtained for both the β-CD-modified and activated GCE surfaces, suggesting that the enhanced detection of acetaminophen is connected mainly to the activation and oxidation of the GCE. Using SEM, EDX and FTIR, no evidence was obtained to indicate that the β-CD was electropolymerised at the GCE.

Application of Chemometrics-assisted HPLC-DAD Strategies for Simultaneous Determination of Paracetamol, Pseudoephedrine HCl, Dextromethorphan HBr, Doxylamine Succinate and Saccharin in Syrup Formulation

Introduction:

This study introduces an effective strategy, which combines high performance liquid chromatography coupled with diode array detection (HPLC-DAD) with multivariate calibration methods for the simultaneous determination of paracetamol (PAR), pseudoephedrine HCl (PSE), dextromethorphan HBr (DEX) and doxylamine succinate (DOX) along with sweetener saccharin (SAC) in syrup formulation.

Methods:

PLS-2 and PCR calibration algorithms were selected for data processing. Based on the strategy, all target analytes were rapidly quantified within 5.3 min under the simple isocratic elution (water: methanol, 20/80, v/v) without a complete separation. The performances of the proposed methods were confirmed by analyzing a series of synthetic solutions including different concentrations of analytes.

Results:

The average recovery values were in the range of 100.33 to 103.70%, and the REP (relative error of prediction) values ranged from 1.96 to 4.36% showed that these methods could provide satisfactory predictions.

Conclusion:

Novel HPLC methods coupled with PLS and PCR algorithm enable a simple, fast and low-cost analysis of similar pharmaceutical products for simultaneous determination of the target compounds.

Development and Validation of an RP-HPLC-PDA Method for Determination of Paracetamol, Caffeine and Tramadol Hydrochloride in Pharmaceutical Formulations

Paracetamol (acetaminophen) (PAR), caffeine (CAF) and tramadol hydrochloride (TRA) are important drugs widely used for many clinical purposes. Determination of their contents is of the paramount interest. In this respect, a quick, simple and sensitive isocratic RP-HPLC method with photodiode array detection was developed for the determination of paracetamol, caffeine and tramadol in pharmaceutical formulations. An improved sensitive procedure was also evolved for tramadol using a fluorescence detector system. A C₁₈ column and a mobile phase constituted by methanol/phosphate were used. LODs were found to be 0.2 μg/mL, 0.1 μg/mL and 0.3 μg/mL for paracetamol, caffeine and tramadol hydrochloride, respectively, using photodiode-array detection. Alternatively, LOD for tramadol decreased to 0.1 μg/mL with the fluorescence detector. Other notable analytical figures of merit include the linear concentration ranges, 0.8–270 μg/mL, 0.4–250 μg/mL and 1.0–300 (0.2–40) μg/mL, for the same ordered analytes (including the fluorescence detector). The proposed method was successfully applied for the quantitative determination of the three drugs in tablet dosage forms.

Ultra-rapid capillary zone electrophoresis method for simultaneous determination of arginine and ibuprofen

The combination of arginine and ibuprofen is widely used for pain relief with a faster onset of action than conventional ibuprofen. Therefore, the determination of both compounds in a single run is highly desirable for rapid quality control applications. This paper reports an ultra-fast method (100 injections/h) for simultaneous determination of arginine and ibuprofen using capillary electrophoresis with capacitively coupled contactless conductivity detection. The separation of arginine as cation and ibuprofen as anion was achieved using a background electrolyte composed by an equimolar mixture of 10 mmol/L of 2-(cyclohexylamino) ethanesulfonic acid and boric acid with pH adjusted to 8.4 using potassium hydroxide. The limits of detections were 5.3 and 10.0 μmol/L for arginine and ibuprofen, respectively. The proposed method is simple, fast (one analysis every 35 s), environmentally friendly (minimal waste generation) and accurate (recovery values between 95 and 98%).

Box-Behnken Design-Desirability Function Approach in Optimization of HPLC Method for Simultaneous Determination of Ibuprofen Along with Additives in Syrup Formulation

BACKGROUND

The advantages of simultaneous analyses are a decrease in analysis time and a more economical use of solvents and reagents. It is desirable that HPLC analyses possess both short term and good resolution.

OBJECTIVE

The aim of the current study is to develop an HPLC method for the simultaneous determination of ibuprofen, sodium benzoate, methyl paraben and propyl paraben as preservatives, and sunset yellow as a colorant, in syrup formulation.

METHOD

To optimize chromatographic separation conditions, multi-response optimization using the Derringer's desirability function was employed for the development of a rapid and efficient HPLC method. The ranges of independent variables used for the optimization process were 50-60% (v/v) for acetonitrile, 5.0-7.0 for pH, and 1.0-2.0 mL/min for flow rate of the mobile phase. The effects of these variables on the output responses, such as critical resolution between sunset yellow and sodium benzoate and retention time of the last peak indicating analysis time of the method, were evaluated by statistical experimental design.

RESULTS

Optimum conditions fixed for the simultaneous analyses were acetonitrile:phosphate buffer (60:40, v/v), pH 5.0, and a flow rate of 1.8 mL/min. The eluate was monitored using a photo diode detector set at 220 nm. Total chromatographic analysis time was approximately 3 min.

CONCLUSIONS

The developed method validated as per International Conference on Harmonization guidelines was successfully applied for the determination of five compounds in their pharmaceutical formulation.

HIGHLIGHTS

This efficient method has isocratic elution system and can be used for routine analyses of these compounds in similar pharmaceutical products.

A new gas chromatographic method development and validation for the simultaneous determination of ibuprofen and caffeine in bulk and pharmaceutical dosage form

Background

Ibuprofen is a nonsteroidal anti-inflammatory drug (NSAID) that has analgesic, anti-inflammatory, and antipyretic properties. Caffeine is one of the most common adjuvant analgesic drugs which is combined with ibuprofen in commercially available formulations. Combining analgesics offers the possibility of increasing effectiveness without increasing dose and therefore risk. Prescribing ibuprofen and caffeine together is common in clinical practice. This is the first work reporting a new and validated gas chromatographic method for the simultaneous determination of ibuprofen and caffeine in bulk and pharmaceutical dosage form. The separation was performed on a TRB-17 column (30.00 m in length, 0.25-mm ID, and 0.25-μm df). Detection was carried out using a flame ionization detector (FID). Methyl paraben was used as an internal standard. The injection volume was 1 μL with 1:50 split ratio using nitrogen as a carrier gas at a flow rate of 1 mL/min. The oven temperature was programmed at 150 °C for 0.5 min, with a rise of 10 °C/min up to 250 °C. The injector temperature was 280 °C, and the detector temperature was 300 °C. The validation of the method including linearity, range, detection limit (DL), quantitation limit (QL), accuracy, precision, specificity, system suitability, and robustness was carried out utilizing International Conference on Harmonization (ICH) guidelines.

Results

The retention times of methyl paraben, ibuprofen, and caffeine were 1.687, 2.594, and 4.031 min, respectively. The method was linear in the range of 1000–7000 μg/mL for ibuprofen and 162.5–1137.5 μg/mL for caffeine with a correlation coefficient of 0.9999 for both drugs. The DL was found to be 131.68 μg/mL and 15.74 μg/mL for ibuprofen and caffeine, respectively, whereas QL was found to be 399.02 μg/mL for ibuprofen and 47.68 μg/mL for caffeine. The accuracy of the method was validated by mean percentage recovery, which was found to be in the acceptable range. The precision study results of the new method were less than the maximum allowable limit percentage of relative standard deviation %RSD ≤ 2.0.

The specificity was evaluated by the standard edition method, and the results of the recovery data showed that excipients do not affect the accuracy of the proposed method. The results of system suitability and robustness tests were also within the acceptable limits.

Conclusion

The first reported method for simultaneous determination of ibuprofen and caffeine by gas chromatography in bulk and combined dosage form was carried out in this work. The developed method gave a good separation of the drugs and internal standard. The analytical performance of the method was statistically validated as per ICH guidelines, and satisfactory results were obtained. The proposed method can be easily adopted for the routine analysis of ibuprofen and caffeine.

Capillary electrophoretic methods for quality control analyses of pharmaceuticals: A review

Capillary electrophoresis represents a promising technique in the field of pharmaceutical analysis. The presented review provides a summary of capillary electrophoretic methods suitable for routine quality control analyses of small molecule drugs published since 2015. In total, more than 80 discussed methods are sorted into three main sections according to the applied electroseparation modes (capillary zone electrophoresis, electrokinetic chromatography, and micellar, microemulsion, and liposome-electrokinetic chromatography) and further subsections according to the applied detection techniques (UV, capacitively coupled contactless conductivity detection, and mass spectrometry). Key parameters of the procedures are summarized in four concise tables. The presented applications cover analyses of active pharmaceutical ingredients and their related substances such as degradation products or enantiomeric impurities. The contribution of reported results to the current knowledge of separation science and general aspects of the practical applications of capillary electrophoretic methods are also discussed.

Spectrum subtraction method for simultaneous determination of acetaminophen and caffeine in panadol extra dosage forms

A simple, specific, accurate and precise spectrophotometric method was established for simultaneous determination of acetaminophen and caffeine in pure form and in their pharmaceutical formulation commercially known as Panadol Extra®. Spectrum subtraction has been used in simultaneous determination of both drugs without prior separation. Spectrum subtraction method parameters were validated according to ICH guidelines in which accuracy, precision, repeatability and robustness were found in accepted limits (98-102%). The linearity range was 7.5-45 µg/mL for caffeine and 4-22 µg/mL for acetaminophen with correlation coefficients ≥0.9990 for both drugs. Advantages and disadvantages of spectrum subtraction were discussed and statistical comparison between the proposed method and the reference one was performed.

Different techniques for overlapped UV spectra resolution of some co-administered drugs with paracetamol in their combined pharmaceutical dosage forms

Six simple, specific, accurate and precise spectrophotometric methods were developed for the first time analysis of some co-administered drugs with paracetamol in their mixture form without prior separation. Paracetamol & orphenadrine citrate were determined by using dual wavelength, bivariate, ratio difference, ratio derivative and mean centering of ratio spectra methods. Paracetamol & caffeine were determined by using ratio difference, ratio derivative and mean centering of ratio spectra methods. Paracetamol & diclofenac sodium were determined by using advanced absorption subtraction, ratio difference, ratio derivative and mean centering of ratio spectra methods. All of these methods were validated according to ICH guidelines where accuracy, precision, repeatability and robustness were found to be within the accepted limits. Advantages and limitations of each method are demonstrated and statistical comparison between the proposed methods was performed.

Facile Fabrication of Graphene-Supported Pt Electrochemical Sensor for Determination of Caffeine

Because elevated levels of caffeine intake can cause many health complications, it is necessary to develop an accurate, simple, rapid, and cost-effective methodology to quantify caffeine in commonly consumed products. This article discusses electrochemical methods to synthesize platinum-graphene hybrid nanosheets (Pt-GR), and how these methods can be utilized to create a new modified electrode, the platinum-graphene nanohybrid glass carbon electrode (Pt-GR/GCE). The electrochemical behavior of caffeine on Pt-GR/GCE was studied by differential pulse voltammetry (DPV). The results showed that a sensitive oxidation peak was observed at 1.336 V in 0.01 mol L^-1 H₂SO₄ buffer solution, indicating that the Pt-GR/GCE exhibited a good electrooxidation activity towards caffeine. The detection limit is 1.129 × 10^-7 mol L^-1. The modified electrode was applied to the determination of caffeine in real samples with satisfactory electrocatalytic results.

Determination of Ibuprofen and Phenylephrine in Tablets by High-Performance Thin Layer Chromatography and in Plasma by High-Performance Liquid Chromatography with Diode Array Detection

Two chromatographic methods (high performance thin layer chromatography (HPTLC) and high performance liquid chromatography-diode array detector (HPLC-DAD)), were addressed for the analysis of a mixture consisted of phenylephrine hydrochloride and ibuprofen in two forms bulk and their combined dosage form. This binary mixture is considered to be a challenging one as the two drugs differ greatly in their chemical and physical properties. Not only this affects their simultaneous analysis, but also hinders their simultaneous extraction from biological fluids as plasma. That is the reason the literature lacks any report for the simultaneous extraction and analysis of these drugs from biological fluids. The concentration ranges of both drugs were 0.1-2.5 μg/spot and 0.1-100 μg/mL by HPTLC and HPLC, respectively. Not only was the HPLC-DAD method applied to the investigated drugs determination in pharmaceutical preparations, but also in spiked human plasma. Extensive study was conducted to optimize their simultaneous extraction from plasma as it was a crucial step for the in vivo analysis. The results obtained by proposed methods and a reference one were statistically comparable by analysis of variance test. No significant difference was recorded between the mean percent levels determined by the proposed methods and the reference one.

Simultaneous Determination of Over-the-Counter Pain Relievers in Commercial Pharmaceutical Products Utilizing Multivariate Curve Resolution-Alternating Least Squares (MCR-ALS) Multivariate Calibration Model

The quality of over-the-counter (OTC) pain relievers is important to ensure the safety of the marketed products in order to maintain the overall health care of patients. In this study, the multivariate curve resolution-alternating least squares (MCR-ALS) chemometric method was developed and validated for the resolution and quantification of the most commonly consumed OTC pain relievers (acetaminophen, acetylsalicylic acid, ibuprofen, naproxen, and caffeine) in commercial drug formulations. The analytical performance of the developed chemometric methods such as root mean square error of prediction, bias, standard error of prediction, relative error of prediction, and coefficients of determination was calculated for the developed model. The obtained results are linear with concentration in the range of 0.5-7 μg/mL for acetaminophen and 0.5-3.5 and 0.5-3 μg/mL for naproxen and caffeine, respectively, while the linearity ranges for acetyl salicylic acid and ibuprofen were 1-15 μg/mL. High values of coefficients of determination ≥0.9995 reflected high predictive ability of the developed model. Good recoveries ranging from 98.0% to 99.7% were obtained for all analytes with relative standard deviations (RSDs) not higher than 1.62%. The optimized method was successfully applied for the analysis of the studied drugs either in their single or coformulated pharmaceutical products without any separation step. The optimized method was also compared with a reported HPLC method using paired t-test and F-ratio at 95% confidence level, and the results showed no significant difference regarding accuracy and precision. The developed method is eco-friendly, simple, fast, and amenable for routine analysis. It could be used as a cost-effective alternative to chromatographic techniques for the analysis of the studied drugs in commercial formulations.

Ultrafast capillary electrophoresis method for the simultaneous determination of ammonium and diphenhydramine in pharmaceutical samples

Ammonium and diphenhydramine are active ingredients commonly found in the same pharmaceutical preparations. We report, for the first time, a sub-minute method for the simultaneous determination of ammonium and diphenhydramine. The method is based on capillary electrophoresis with capacitively coupled contactless conductivity detection. Both analytes can be quantified in a single run (∼80 injections/h) using 30 mmol/L 2-(N-morpholino)ethanesulfonic acid and 15 mmol/L lithium hydroxide (pH 6.0) as background electrolyte. The separation by capillary electrophoresis was achieved on a fused-silica capillary (50 cm total length, 10 cm effective length, and 50 μm inside diameter). The limits of detection were 0.04 and 0.02 mmol/L for ammonium and diphenhydramine, respectively. The proposed method also provided adequate recovery values for spiked samples (100-106 and 97-104% for ammonium and diphenhydramine, respectively). The results obtained with the new capillary electrophoresis method were compared with those of the high-performance liquid chromatography method for diphenhydramine and the Kjeldahl method for ammonium and no statistically significant differences were found (95% confidence level).

Design of Optical Sensor Membrane Based on Polymer Poly(methyl methacrylate) for Paracetamol Detection in Traditional Herbal Medicine

Generally, regulation states that herbal medicines are remedies containing plants or preparation of plants as active ingredients only. Paracetamol is one of the drugs that is frequently added in herbal medicine to enhance the effect as an analgesic. The government regulation disallows chemical drugs contained in herbal medicine due to the toxic effect of uncontrolled consumption. On this study, the optical sensor membrane from polymer poly(methyl methacrylate) (PMMA) was synthesized by phase inversion method and was used to detect paracetamol in herbal medicine. PMMA was made in three different concentrations 5%, 7.5%, and 10% and was mixed with ferric chloride (FeCl3), Folin-Ciocalteu, and Nessler reagent as specific colorimetric reagents for paracetamol detection, with a ratio of solvent:reagent was 6:4; 7:3; and 8:2. The result of the experiment shows that PMMA-FeCl3 7.5% (7:3), PMMA-Folin 5% (6:4), and PMMA-Nessler 5% (6:4) give the best performance for paracetamol detection. Real herbal medicine samples were analyzed to confirm the practical application of this sensor, and the result shows good agreement with UV-Vis data. The results show that optical sensor membrane which has been developed can be used as new detection method of paracetamol for community application.

Concurrent determination and separation of inorganic cations and anions in microchip electrophoresis with precisely controlled high-voltage

An improved method for the concurrent determination and separation of cations and anions by microchip electrophoresis with capacitively coupled contactless conductivity detection (ME-C4 D) is described. Two kinds of microchip structures were designed. The first microchip has a long bent separation channel. And for the defects of the first microchip, the second microchip with a Y-type separation channel has been proposed. The background electrolyte (BGE) composed of 20 mm His/MES and 0.01 mm CTAB was optimized for inhibiting the electroosmotic flow (EOF). Due to the low electroosmotic flow, the cations and anions migrate in opposite directions and can be separated from each other. With the precisely controlled high-voltage, cations and anions can be migrated in microchannels according to our requirements and sequentially detected by a C4 D detector built in-house. Samples containing K+ , Na+ , Li+ , Cl- , F- and PO43- were analyzed simultaneously in a single run (within 140 s) by both methods. The reproducibility obtained by both methods remained below 5% for migration time and within 3.5-9.1% for peak areas. The proposed concurrent determination methods are inexpensive, simple, fast, ease of operation, high degree of integration.

Evaluation of sample injection precision in respect to sensitivity in capillary electrophoresis using various injection modes

A comparative study was conducted to assess the injection precision in capillary electrophoresis for cationic analytes (arecoline, codeine, papaverine). The precision was measured in respect to methods sensitivity in various injection modes in capillary electrophoresis: standard hydrodynamic injection (3.45 kPa for 6 s), large volume sample stacking (3.45 kPa for 40 s), and field-amplified sample injection (10 kV for 65 s). All measurements were conducted for aqueous solutions of standards to minimize the errors linked to the sample preparation step. The methods were submitted to precision assessment at three concentration levels: at the limit of quantification, three-fold and ten-fold of limit of quantification. The results were compared to those from high-performance liquid chromatography as a reference technique. The field-amplified sample injection method was shown to provide greatest sensitivity (quantification limits down to 4 ng/mL for all three tested compounds) but the lowest precision. High-performance liquid chromatography was established as the most reliable technique (coefficient of variation in all intraday experiments was below 1%). It was also shown that with a use of large volume sample injection technique, similar sensitivity as in high-performance liquid chromatography can be easily reached.

Frequency-tuned contactless conductivity detector for the electrophoretic separation of clinical samples in capillaries with very small internal dimensions

An axial design of a capacitively coupled contactless conductivity detector was tested in combination with fused-silica capillaries with internal diameters of 10, 15, and 25 μm, which are used for high-efficiency electrophoretic separation. The transmission of the signal in the detection probe dependent on the specific conductivity of the solution in the capillary in the range 0-278 mS.m^-1 has a complex character and a minimum appears on the curve at very low conductivities. The position of the minimum of the calibration dependence gradually shifts with decreasing frequency of the exciting signal from 1.0 to 0.25 MHz toward lower specific conductivity values. The presence of a minimum on the calibration curves is a natural property of the axial design of contactless conductivity detector, demonstrated by solution of the equivalent electrical circuit of the detection probe, and is specifically caused by the use of shielding foil. The behavior of contactless conductivity detector in the vicinity of the minimum was documented for practical separations of amino acids in solutions of 3.2 M acetic acid with addition of 0-50% v/v methanol.