Determination Of Paracetamol In Pharmaceuticals Research Articles

Targeted modification of the carbon paste electrode by natural zeolite and graphene oxide for the enhanced analysis of paracetamol

In this work, the targeted modification of carbon paste (CP) by admixing of conductive graphene oxide (GO) and mesoporous natural zeolite with the introduced Ni2+ cations (NiZ), providing electrocatalytic properties, is presented. The performed univariate optimization indicated that 5 % (w/w) of NiZ and GO in the CP is sufficient to ensure a threefold increase in peak current and lower the overpotential of paracetamol (PAR) oxidation, while retaining a low background current and high signal-to-noise ratio. The fabricated CPE/NiZ/GO sensor ensured a linear response in the PAR concentration range from 0.004 to 0.12 mg L−1, advantageously low limit of detection equal to 0.0012 mg L−1 (0.0078 µM), and high stability of recorded signals (RSD = 3 %). Moreover, the proposed analytical method is characterized by good selectivity and robustness to the presence of interference. The usefulness of the CPE/NiZ/GO was verified by the determination of PAR in pharmaceuticals, human urine and serum, delivering acceptable results.

Reliable calibration by nonlinear standard addition method in the presence of additive interference effects

The possibility of adapting the Standard Addition Method (SAM) to calibration in very difficult analytical conditions, namely when there is a need to determine an analyte with the use of nonlinear calibration graph and in the presence of matrix components causing additive interference effect, is investigated. To this aim the SAM in the common version and the Chemical H-point Standard Addition Method (C-HPSAM) realized by the flow injection technique were applied. Specifically, a flow manifold was used for construction of a set of nonlinear calibration graphs in different chemical conditions. As the graphs were intersected indicating both the additive interference effect and the analytical result free of this effect, the analyte concentration in the sample was able to be obtained with improved accuracy. The applicability of this approach was verified on the example of spectrophotometric determination of paracetamol in pharmaceuticals and of total acidity in wines. The C-HPSAM method enabled complete compensation of the additive effect and obtaining analytical results at a relative error not exceeding 6.0%.Graphical abstract

Modification of electrodes using conductive porous layers to confer selectivity for the voltammetric detection of paracetamol in the presence of ascorbic acid, dopamine and uric acid

A glassy carbon electrode (GCE) has been modified with multiwalled carbon nanotubes (MWCNTs) for the selective detection of paracetamol (PAR) in the presence of ascorbic acid (AA), dopamine (DA) and uric acid (UA). The oxidation of PAR shows a quasi-reversible response on a naked GCE at which an appreciable overpotential is required to drive the two electron oxidation. However, the peak-to-peak separation is seen to reduce and the electrochemical signal appears more reversible as the GCE is modified with an increasingly thick layer of MWCNTs. The results indicate that both anodic and cathodic peaks occur at lower overpotential with increasing layer thickness on the electrode surface, and that the overall peak-to-peak separation decreases as a result. The data are consistent with a transition from planar diffusion to a thin layer character as the potential required for the oxidation of PAR shifts to lower potentials. The experimental results show that the use of conducting porous layers on the surface of electrodes can be utilised to modify the mass transport regime from planar diffusion to a thin layer character that this alteration can also favourably facilitate the electrochemical discrimination between species which oxidise or reduce at similar potentials under planar diffusion conditions. The modified electrode was used for the determination of PAR using square wave voltammetry in 0.1M phosphate buffer solution (PBS) at pH 7. The results showed that the peak currents were proportional to the concentrations of PAR with a linear dynamic range of 2.0×10−10M to 1.5×10−5M and a detection limit of 9.0×10−11M was obtained. The method has successfully been applied for the determination of PAR in pharmaceuticals.

Fluorimetric SIA optosensing in pharmaceutical analysis: Determination of paracetamol

The coupling of sequential injection analysis (SIA) and fluorimetric solid phase transduction is here applied to the determination of paracetamol in pharmaceuticals. The reaction product between the analyte and sodium nitrite in acidic medium is inserted, after alkalinization, in the system. This product is transitorily retained on the active solid sensing phase (the anionic solid support QAE A-25) developing its native fluorescence signal, which is measured at 325/430 nm for the excitation and emission wavelengths respectively. The described system is linear within the range 6.6–80 μg ml −1, with a 2 μg ml −1 detection limit and a 2.5% R.S.D ( n = 10). The proposed fluorimetric SIA optosensor has been applied to the determination of paracetamol in several pharmaceutical preparations, obtaining satisfactory results.

Determination of paracetamol in pure and pharmaceutical dosage forms by pulse perturbation technique

A new procedure for kinetic determination of paracetamol in pharmaceuticals is proposed. The method is based on potentiometric monitoring of the concentration perturbations of the matrix reaction system being in a stable non-equilibrium stationary state close to the bifurcation point. In the case considered as the matrix system, the Bray–Liebhafsky oscillatory reaction is used. The response of the matrix system to the perturbations by different concentrations of paracetamol is followed by a Pt-electrode. Proposed method relies on the linear relationship between maximal potential shift, Δ E m, and the logarithm of added paracetamol amounts. It is obtained in optimized experimental conditions for variable amounts of paracetamol in the range 0.0085 and 1.5 μmol. The sensitivity and precision of proposed method were quite good (0.0027 μmol as the limit of detection and 2.4% as R.S.D.). Some aspects of possible chemical interactions between paracetamol and matrix are discussed. Applicability of the proposed method to the direct determination of paracetamol in pharmaceutical formulations was demonstrated.

Continuous flow spectrophotometric determination of paracetamol in pharmaceuticals following continuous microwave assisted alkaline hydrolysis

This paper reports a continuous flow-based spectrophotometric method for the determination of paracetamol in pharmaceuticals. Dilute samples containing paracetamol are continuously hydrolysed in an alkaline medium, using a household microwave oven, to p-aminophenol, which reacts with o-cresol in 3.5 M NaOH. The blue derivative thus formed exhibits an absorbance maximum at 620 nm. The detection limit of the method is 0.2 μg ml −1 and the system obeys Beer's law from 0.6 to 20 μg ml −1. Repeatability was checked by calculating the R.S.D. for 11 standard solutions containing a paracetamol concentration of 4 μg ml −1 each and found to be 1.8%. The proposed method was validated by determining paracetamol in various pharmaceutical preparations with average R.S.D. of 2.4%.

Fast determination of paracetamol by using a very simple photometric flow-through sensing device

A simple flow-through UV optosensing device was developed for the determination of paracetamol based on its transient retention and concentration on a suitable active solid support (Sephadex QAE A-25 anion-exchange resin) packed in the flow cell and the continuous monitoring of its native absorbance on the solid phase at 264 nm. The sample was injected into a 0.08-M NaCl carrier stream at pH 11.0 by using a simple monochannel FIA manifold. After developing the analytical signal, paracetamol was desorbed from the solid support by the carrier solution itself. A very good linear response was found in the concentration range 0.5–8.0 μg ml −1 with a RSD (%) of 1.24, a detection limit of 0.022 μg ml −1 and a sampling rate of 40 h −1. A strong increase in sensitivity as well as a very much higher selectivity were achieved as compared with the conventional flow injection method as a consequence of the separation of the analyte from the sample plug and its retention on the active solid support placed in the detection area. Applicability of the proposed sensor to direct determination of paracetamol in pharmaceuticals (to solve the sample being the only treatment) was successfully demonstrated.

Determination of paracetamol in dosage forms by non-suppressed ion chromatography

An ion-chromatography procedure for the simultaneous determination of paracetamol and salicylic acid without suppression using UV detection is proposed. The method is applied to the determination of paracetamol in pharmaceuticals and also permits the quantitation of the total acetylsalicylic acid as salicylic acid.

Flow injection spectrophotometric determination of paracetamol in pharmaceuticals by means of on-line microwave-assisted hydrolysis and reaction with 8-hydroxyquinoline (8-quinolinol)

A new procedure is proposed for the spectrophotometric determination of paracetamol in pharmaceuticals. The method is based on the on-line alkaline hydrolysis of paracetamol to p-aminophenol (PAP) and the reaction with 8-hydroxyquinoline (8-quinolinol) in the presence of potassium periodate as oxidant to form a blue indophenol dye which absorbs at 608 nm. The method has a 30-limit of detection of 0.2 μg ml −1 and provides a sampling frequency of 70 h −1. Previous batch studies using closed PTFE reactors demonstrate that paracetamol can be hydrolysed quantitatively to PAP in only 2 min using an irradiation power of 990 W and 5 M NaOH or in 3 min using 1100 W and 3 M HCl. The on-line alkaline hydrolysis, carried out in a 6 m reaction coil located inside the cavity of a Microdigest 301 system provides an hydrolysis yield of 54.1% for a reaction time of 94 s and allows the complete automation of the analytical procedure. The method developed has been applied to the analysis of real pharmaceutical formulations using alkaline solutions of paracetamol as standards. In the flow conditions, the recovery percentage values obtained for added paracetamol concentrations, from 1.06 to 3.17 × 10 −5 M, range from 96.3%, in syrup samples, to 98–100% in tablets and capsules, and 102% in suppositories. The relative standard deviation found, for three independent analyses of each sample, varies from 0.8 to 4% as a function of the paracetamol concentration and the type of sample, the less precise values being obtained or syrup analysis.

Flow injection–Fourier transform infrared spectrometric determination of paracetamol in pharmaceuticals

A procedure for the direct FTIR spectrometric determination of paracetamol in pharmaceuticals is described. The method is based on the solubilization of paracetamol in a 10% v/v ethanol in CH2Cl2 solution and direct absorbance measurement at 1515 cm–1, using the baseline established at 1900 cm–1 for measurement correction. The procedure can be carried out in both the stopped-flow and flow injection (FI) modes. In both instances the sensitivity is approximately 0.09 A ml mg–1, the limit of detection being 8 µg ml–1 in the stopped-flow mode and 33 µg ml–1 in the FI mode. Caffeine, acetylsalicylic acid, propyphenazone and ascorbic acid do not interfere with the FTIR determination of paracetamol, and the interference of citric acid can be eliminated by using measurements between 1518 and 1509 cm–1 in the first-derivative mode. The FI-FTIR methodology provides a fast and appropriate technique for the routine analysis of pharmaceuticals with a throughput of 45 samples h–1.

Spectrofluorimetric determination of paracetamol in pharmaceuticals and biological fluids

A spectrofluorimetric method for the determination of paracetamol is presented, based on the oxidation of the analyte to give the fluorophore 2,2′-dihydroxy-5,5′-diacetyldiaminebiphenyl. Sodium hypochlorite was used as an oxidizing reagent and the optimum pH was found to be 10.0 (sodium carbonate-boric acid buffer solution). The linear concentration range of application was 0.1–100.0 μg ml −1 of paracetamol, the detection limit 0.01 μg ml −1 and the relative standard deviation 1.2%. The method has been satisfactorily applied to the determination of paracetamol in pharmaceutical formulations and biological fluids.