Sequential spectrophotometric determination of paracetamol and p-aminophenol with 2,2′-(1,4-phenylenedivinylene) bis-8-hydroxyquinoline as a novel coupling reagent after microwave assisted hydrolysis

Enhanced chemiluminescence determination of paracetamol

Due to the severe consequences of potential overdoses of paracetamol (PCM) on the human body, the measurement of PCM in pharmaceutical and biological samples is essential.

Validated specific HPLC-DAD method for simultaneous estimation of paracetamol and chlorzoxazone in the presence of five of their degradation products and toxic impurities

This work demonstrates a specific and reliable HPLC with diode array detection (DAD) method for the simultaneous estimation of paracetamol (PAR) and chlorzoxazone (CZ) in the presence of five of their degradation products and toxic impurities; namely; 4-aminophenol (AP), 4-nitrophenol (NP), acetanilide (AT), 4-chloroacetanilide (CA) and 2-amino-4-chlorophenol (ACP). Successful chromatographic separation was accomplished using Waters Symmetry C8 column (3.9 × 150 mm, 5 μm) with gradient elution of the mobile phase consisting of 0.05 M phosphate buffer pH 7.5 and methanol. The gradient elution started with 5% (by volume) methanol ramped up linearly to 50% in 10 min, and then maintained at this percentage afterward till the end of the run. The mobile phase was pumped at a flow rate of 1.0 mL/min. The multiple wavelength detector was adjusted at 244 and 285 nm to quantify PAR and CZ, respectively. Additionally, the wavelength 270 nm was found suitable for monitoring the separation of the entire mixture of PAR, CZ, and their impurities. Seven peaks eluted with excellent resolution at retention times 3.4, 5.7, 8.0, 10.1, 10.8, 13.5, and 14.4 min for AP, PAR, NP, AT, ACP, CZ, and CA, respectively. Performance of the proposed method was validated with respect to linearity, range, precision, accuracy, specificity, robustness, detection, and quantitation limits. Calibration curves were linear in the ranges of 10-75 and 10-100 µg/mL for PAR and CZ, respectively with correlation coefficients not less than 0.9998. The proposed method proved to be specific and stability indicating by the resolution of both drugs from their degradation products and toxic impurities. Validated HPLC method was successfully applied to the analysis of PAR and CZ in their combined capsules dosage form, and assay results were favorably compared with a published reference HPLC method. DAD served as an efficient tool for peak identity and purity verification.

Artificial neural network assisted kinetic spectrophotometric technique for simultaneous determination of paracetamol and p-aminophenol in pharmaceutical samples using localized surface plasmon resonance band of silver nanoparticles

Spectrophotometric analysis method based on the combination of the principal component analysis (PCA) with the feed-forward neural network (FFNN) and the radial basis function network (RBFN) was proposed for the simultaneous determination of paracetamol (PAC) and p-aminophenol (PAP). This technique relies on the difference between the kinetic rates of the reactions between analytes and silver nitrate as the oxidizing agent in the presence of polyvinylpyrrolidone (PVP) which is the stabilizer. The reactions are monitored at the analytical wavelength of 420nm of the localized surface plasmon resonance (LSPR) band of the formed silver nanoparticles (Ag-NPs). Under the optimized conditions, the linear calibration graphs were obtained in the concentration range of 0.122-2.425μgmL(-1) for PAC and 0.021-5.245μgmL(-1) for PAP. The limit of detection in terms of standard approach (LODSA) and upper limit approach (LODULA) were calculated to be 0.027 and 0.032μgmL(-1) for PAC and 0.006 and 0.009μgmL(-1) for PAP. The important parameters were optimized for the artificial neural network (ANN) models. Statistical parameters indicated that the ability of the both methods is comparable. The proposed method was successfully applied to the simultaneous determination of PAC and PAP in pharmaceutical preparations.

Selective determination of catechin among phenolic antioxidants with the use of a novel optical fiber reflectance sensor based on indophenol dye formation on nano-sized TiO₂

The optical sensor for "tea catechins" was built by immobilizing 2,2'-(1,4-phenylenedivinylene)bis-8-hydroxyquinoline (PBHQ) on TiO₂ nanoparticles (NPs). The sensor worked by "indophenol blue" dye formation on PBHQ-immobilized TiO₂ NPs as a result of p-aminophenol (PAP) autoxidation with dissolved O₂ at pH 10. Among quercetin, rutin, naringenin, naringin, gallic acid, caffeic acid, ferulic acid, p-coumaric acid, catechin, epicatechin, epicatechin gallate, epigallocatechin, epigallocatechin gallate, and trolox, only catechin group antioxidants delayed the color formation on NPs, as measured by the reflectance signal at 710 nm. For quantitative analysis, reflectance signal versus time was recorded, and the difference between the areas under curve (ΔAUC) in the presence and absence of catechin was correlated (r = 0.98) to catechin concentration. The selectivity of the sensor for catechins was shown in tea infusions compared to other plant extracts and was ascribed to the nonplanar structure of catechin interfering with the formation of perfectly conjugated indophenol blue on TiO₂ surface.

Rapid determination of acetaminophen and p-aminophenol in pharmaceutical formulations using miniaturized capillary electrophoresis with amperometric detection

Capability of fast analysis of a novel miniaturized capillary electrophoresis with carbon disk electrode amperometric detection (mini-CE-AD) system was demonstrated by determining acetaminophen and p-aminophenol in dosage forms. Factors influencing the separation and detection processes were examined and optimized. Under the optimum conditions, the end-capillary 300 microm carbon disc electrode amperometric detector offered favorable signal-to-noise characteristics at a relatively low potential (+600 mV versus Ag/AgCl) for detecting acetaminophen and p-aminophenol. Two analytes can been separated within 150 s in a 8.5 cm length capillary at a separation voltage of 2000V using a Na2B4O7-KH2PO4 running buffer (pH 7.2). Acetaminophen and p-aminophenol could be detected down to the 1.4 x 10(-6)-5.9 x 10(-7) molL(-1) level with linearity up to the 1.0 x 10(-3) molL(-1) level examined. The inter-day repeatability for analytes in peak current (R.S.D.< or =2.3%) and migration times (R.S.D.< or =1.3%) were excellent. The proposed mini-CE-AD system should find a wide range of analytical applications in pharmaceutical formulations as an alternative to conventional CE and mu-CE.

Determination of paracetamol: historical evolution

Paracetamol is a common analgesic and antipyretic drug that is used for the relief of fever, headaches and other minor aches and pains. Their determination in pharmaceuticals is of paramount importance, since an overdose of paracetamol can cause fulminating hepatic necrosis and other toxic effects. Many analytical methodologies have been proposed for the determination of paracetamol. The aim of the present study is to evaluate the utility of different techniques for quantification of paracetamol content in pharmaceutical formulations and biological samples.

Spectrophotometric Determination of Paracetamol in Urine with Tetrahydroxycalix[4]arene as a Coupling Reagent and Preconcentration with Triton X-114 Using Cloud Point Extraction

In the present paper, conventional spectrophotometry in conjunction with cloud point extraction-preconcentration were investigated as alternative methods for paracetamol (PCT) assay in urine samples. Cloud point extraction (CPE) was employed for the preconcentration of p-aminophenol (PAP) prior to spectrophotometric determination using the non-ionic surfactant Triton X-114 (TX-114) as an extractant. The developed methods were based on acidic hydrolysis of PCT to PAP, which reacted at room temperature with 25,26,27,28-tetrahydroxycalix[4]arene (CAL4) in the presence of an oxidant (KIO(4)) to form an blue colored product. The PAP-CAL4 blue dye formed was subsequently entrapped in the surfactant micelles of Triton X-114. Cloud point phase separation with the aid of Triton X-114 induced by addition of Na(2)SO(4) solution was performed at room temperature as an advantage over other CPE assays requiring elevated temperatures. The 580 nm-absorbance maximum of the formed product was shifted bathochromically to 590 nm with CPE. The working range of 1.5-12 microg ml(-1) achieved by conventional spectrophotometry was reduced down to 0.14-1.5 microg ml(-1) with cloud point extraction, which was lower than those of most literature flow-through assays that also suffer from nonspecific absorption in the UV region. By preconcentrating 10 ml sample solution, a detection limit as low as 40.0 ng ml(-1) was obtained after a single-step extraction, achieving a preconcentration factor of 10. The stoichiometric composition of the dye was found to be 1 : 4 (PAP : CAL4). The impact of a number of parameters such as concentrations of CAL4, KIO(4), Triton X-100 (TX-100), and TX-114, extraction temperature, time periods for incubation and centrifugation, and sample volume were investigated in detail. The determination of PAP in the presence of paracetamol in micellar systems under these conditions is limited. The established procedures were successfully adopted for the determination of PCT in urine samples. Since the drug is rapidly absorbed and excreted largely in urine and its high doses have been associated with lethal hepatic necrosis and renal failure, development of a rapid, sensitive and selective assay of PCT is of vital importance for fast urinary screening and antidote administration before applying more sophisticated, but costly and laborious hyphenated instrumental techniques of HPLC-SPE-NMR-MS.