Multivariate calibration applied to the time-resolved chemilumnescence for the simultaneous determination of morphine and its antagonist naloxone

Innovative design of a methodology for the simultaneous determination of compounds by kinetic-spectroscopy three-dimensional chemiluminescence

This report presents a novel methodology based in the quickly acquisition of full UV-vis range spectra combined with the joint determination of kinetic parameters and chemiluminescence signals. Then this technique allows obtaining three-dimensional chemiluminescence spectra profiles containing kinetic and spectroscopic information. That is especially useful for resolving mixtures of luminophors because of more analytical information for each analyte is available increasing the selectivity relative to conventional chemiluminescence methods. To accomplish this, a conventional Back-Thinned CCD detector is used and the three-dimensional chemiluminescence spectra is subsequently processed so that two-dimensional spectra with different trajectories can be obtained by dedicated software CLTotal. The potential of the proposed analytical methodology was assessed for the simultaneous determination of two polycyclic aromatic hydrocarbons. The chemiluminescent reaction between DNPO and hydrogen peroxide induced by their presence was used to record 3D spectra and the software CLTotal to subsequently construct linear variable-angle trajectories in the spectra, in order to obtain more selective 2D spectra facilitating the simultaneous determination of the analytes. The results of the statistical analysis testify to the usefulness of the proposed method for the intended purpose.

Preconcentration of codeine in pharmaceutical and human urine samples by multi-walled carbon nanotubes and its spectrophotometric determination

A rapid and efficient solid phase extraction method was established for the preconcentration of codeine prior to its simple determination by spectrophotometry. The extraction process is based on the multi-walled carbon nanotubes (CNTs) containing –COOH functional groups. These CNTs showed a great affinity for the low quantities of codeine in certain condition. Various extraction factors including buffer type, concentration and its pH, ionic buffer, incubation time, and eluent were optimized to achieve high sensitivity. The calibration graph was linear in the codeine concentration range of 0.001–4 mg·L−1, with a detection limit (3s) of 0.4 μg·L−1. The relative standard deviation (RSD %) for the repetitive determination of 0.01, 0.5, and 2 mg·L−1 codeine (n = 5) were 1.56%, 2.01%, and 1.63%, respectively. Furthermore, comparison with other reported methods showed that the presented method has suitable characteristics. Finally the method was successfully used to accurately determine codeine in pharmaceutical and human urine samples.

Molecularly imprinted polymers on multi-walled carbon nanotubes as an efficient absorbent for preconcentration of morphine and its chemiluminometric determination

A simple and selective method was described for the determination of morphine based on its preconcentration by molecularly imprinted polymers on multi-walled carbon nanotubes prior to its chemiluminometric recognition.

A high throughput gold nanoparticles chemiluminescence detection of opioid receptor antagonist naloxone hydrochloride

Background

The opioid antagonist agent naloxone hydrochloride (NLX) is a drug that has high affinity for opiate receptors but do not activate these receptors. Owing to the role of this drug to block the effects of exogenous administered opioids and endogenous released endorphians we can deduce the importance of developing sensitive analytical methods for detection of such drug. In the present study gold nanoparticles (AuNPs) was employed for enhancing the chemiluminescence (CL) signals arising from luminol-ferricyanide reaction in the presence of naloxone hydrochloride using sequential injection chemiluminescence analysis (SIA).

Method

In the present study gold nanoparticles (AuNPs) was employed for enhancing the chemiluminescence (CL) signals arising from luminol-ferricyanide reaction in the presence of naloxone hydrochloride using sequential injection chemiluminescence analysis (SIA).

Results

The developed method was examined under optimum experimental conditions and the obtained results revealed a linear relationship between the relative CL intensity and the investigated drug at a concentration range of 1.0×10⁻⁹-1.0×10⁻² mol L⁻¹, (r = 0.9993, n=9) with detection and quantification limits of 1.6×10⁻¹¹ and 1.0×10⁻⁹ mol L⁻¹, respectively. The relative standard deviation was 0.9%.

Conclusion

The proposed method was employed for the determination of the investigated drug in bulk powder, its pharmaceutical dosage forms and biological fluids. The interference of some metals and amino acids on the CL intensity was investigated. Also the interference of some related pharmacological action drugs was tested. The obtained results of the developed method were statistically treated and compared with those obtained from other reported methods.

Graphical Abstract

Simultaneous chemiluminescence determination of citric acid and oxalic acid using multi-way partial least squares regression

A novel kinetic chemiluminescent method proposed for the simultaneous determination of oxalic acid and citric acid in their mixtures.

Application of time-resolved fluorescence to the determination of metabolites

A simple fluorescent methodology for the simultaneous determination of two major metabolites of acetylsalicylic acid--salicylic and gentisic acids--in pharmaceutical preparations and human urine is proposed. Due to the overlapping between the fluorescence spectra of both analytes, the use of the more selective fluorescence decay curves is proposed. Values of dependent instrumental variables affecting the signal-to-noise ratio were fixed with a simplex optimization procedure. A calibration matrix of thirteen standards plus two blank samples was processed using a partial least-squares (PLS) analysis. To assess the goodness of the proposed method, a prediction set of nine synthetic samples was analyzed, obtaining recovery percentages between 95% and 106%. Limits of detection, calculated by means of a new criterion, were 3.49 μg L(-1) and 1.66 μg L(-1) for salicylic and gentisic acids, respectively. The method was also tested in three pharmaceutical preparations containing salicylic acid, obtaining recovery percentages close to 100%. Finally, the simultaneous determination of both analytes in human urine samples was successfully carried out by the PLS-analysis of a matrix of thirteen standards plus five analyte blanks. Although spectra of analytes and urine overlap strongly, no extraction method neither prior separation of the analytes were needed.

Simultaneous determination of doxycycline and chlortetracycline in real samples by europium-sensitized luminescence

A simple luminescent methodology for the simultaneous determination of doxycycline and chlortetracycline in pharmaceutical preparations and human urine is proposed. Since the native fluorescence of both analytes is negligible, this method takes advantage of the lanthanide-sensitized luminescence, which provides increased sensitivity. Due to the strong overlapping between the luminescence spectra of both europium complexes, the use of luminescence decay curves to resolve mixtures of the analytes is proposed, particularly as these curves are more selective. A factorial design, with three levels per factor, coupled to a central composite design was selected to obtain a calibration matrix of 13 standards plus one blank sample, which were processed with a partial least-squares analysis. In order to assess the effectiveness of the proposed method, a prediction set of 10 synthetic samples was analyzed, and recovery percentages between 95 and 104% were obtained. Limits of detection, calculated by means of a new criterion, were 3.27 and 1.06 μg L(-1) for doxycycline and chlortetracycline, respectively. The method was tested in three different pharmaceutical preparations containing the analytes, with average recovery percentages of 99.4 ± 1.8 for doxycycline and 100.5 ± 2.1 for chlortetracycline. Moreover, a central composite design was also developed to obtain a calibration matrix that made feasible the simultaneous determination of both tetracyclines in human urine samples. In this case, average recovery percentages were 98.0 ± 4.4 and 97.8 ± 4.6 for doxycycline and chlortetracycline, respectively. No extraction method or prior separation of the analytes was needed.

Direct determination of danofloxacin and flumequine in milk by use of fluorescence spectrometry in combination with partial least-squares calibration

A new method for the simultaneous determination of danofloxacin and flumequine in milk samples was developed by using the nonlinear variable-angle synchronous fluorescence technique to acquire data and a partial least-squares chemometric algorithm to process them. A calibration set of standard samples was designed by combination of a factorial design with two levels per factor and a central star design. Whey was used as the third component of the calibration matrix. In order to assess the goodness of the proposed method, a prediction set of 11 synthetic samples was analyzed, obtaining recovery percentages between 96.1% and 104.0%. Limits of detection, calculated by means of a new criterion, were 0.90 and 12.4 ng mL(-1) for danofloxacin and flumequine, respectively. Finally, the simultaneous determination of both fluoroquinoles in milk samples containing the analytes was successfully carried out, obtaining an average recovery percentage of 99.3 ± 4.4 for danofloxacin and 100.7 ± 4.4.

Kinetic-spectrometric three-dimensional chemiluminescence as an effective analytical tool. Application to the determination of benzo(a)pyrene

Kinetic and spectroscopic methods were used in combination in this work to develop a new analytical tool for use in chemiluminescence detection processes. Specifically, time-resolved chemiluminescence was used jointly with a stopped-flow assembly in order to monitor the chemiluminescence produced in the oxidation of bis(2,4-dinitrophenyl)oxalate (DNPO) by hydrogen peroxide in the presence of a polycyclic aromatic hydrocarbon. Recording of successive two-dimensional spectra during the emission process and treating the acquired spectral data with dedicated software allows the obtainment of three-dimensional chemiluminescence spectra, a result of the joint use of two analytical techniques. Thus, using a flow cell specifically designed for direct coupling to the charge-coupled device (CCD) detector increases the emission intensity without the need for fibre optics. Also, using dedicated software to process the acquired two-dimensional spectra affords a comprehensive kinetic and spectroscopic characterization of the chemiluminescence signal via the three-dimensional spectrum previously obtained. The analytical potential of this new tool was assessed by application to the chemiluminescent reaction between a peroxyoxalate and an oxidant (hydrogen peroxide); the reaction is induced by benzo(a)pyrene, which was used to determine this polycyclic aromatic hydrocarbon in an organic solvent. A linear calibration graph was obtained between 0.5 and 20 mg L(-1). The limit of detection found to be 3.97 μg L(-1) and a relative standard error of 0.64% and a relative standard deviation of 1.87% were obtained. The results reached testify to the usefulness of the proposed analytical tool for simple determinations and its potential for the resolution of complex mixtures or determinations in complex matrices.

Simultaneous determination of captopril and hydrochlorothiazide by time-resolved chemiluminescence with artificial neural network calibration

The combined use of chemometrics and chemiluminescence (CL) measurements, with the aid of the stopped-flow mixing technique, developed a simple time-resolved CL method for the simultaneous determination of captopril (CPL) and hydrochlorothiazide (HCT). The stopped-flow technique in a continuous-flow system was employed in this work in order to emphasize the kinetic differences between the two analytes in cerium (IV)-rhodamine 6G CL system. After the flow was stopped, an initial rise of CL signal was observed for HCT standards, while a direct decay of CL signal was obtained for CPL standards. The mixed CL signal was monitored and recorded on the whole process of continuousflow/stopped-flow, and the obtained data were processed by the chemometric approach of artificial neural network. The relative prediction error (RPE) of CPL and HCT was 5.9% and 8.7%, respectively. The recoveries of CPL and HCT in tablets were found to fall in the range between 95% and 106%. The proposed method was successfully applied to the simultaneous determination of CPL and HCT in a compound pharmaceutical formulation.

Simultaneous chemiluminescence determination of thebaine and noscapine using support vector machine regression

In this work, a batch chemiluminescence (CL) method has been proposed for the simultaneous determination of two structurally similar alkaloids, noscapine and thebaine. The method is based on the kinetic distinction of the CL reactions of noscapine and thebaine with Ru(bipy)(3)(2+) and Ce(IV) system in a sulfuric acid medium. The least squared support vector machine (LS-SVM) regression was applied for relating the concentrations of both compounds to their CL profiles. The parameters of the model consisting of sigma(2) and gamma were optimized by constructing LS-SVM models with all possible combinations of these two parameters to select the model with the minimum root mean squared error of cross validation (RMSECV) as the best. The parameters of this model were then selected as optimized values. Under the optimized experimental conditions for both compounds, the detection limits obtained using the LS-SVM regression were 0.08 and 0.1 micromo lL(-1) for noscapine and thebaine, respectively. The proposed method was utilized for the simultaneous determination of the compounds in pharmaceutical formulations and plasma samples with satisfactory results.