Kinetic fluorimetric determination of the antineoplastic methotrexate (MTX) in human serum

On-line coupling of derivatization with pre-concentration to determine trace levels of methotrexate

A new simple, sensitive and precise green analytical procedure using an automated packed-reactor derivatization technique coupled with on-line solid-phase enrichment (SPEn) has been developed and evaluated to determine trace levels of methotrexate (MTX). The method was based on injection of MTX into a flowing stream of phosphate buffer (0.04 M, pH 3.4), carried through the packed oxidant reactor of Cerium (IV) trihydroxyhydroperoxide for oxidative cleavage of the drug into highly fluorescent product, 2,4-diaminopteridine-6-carboxylic acid, followed by SPEn on a head of short ODS column (10 mm×4.6 mm i.d., 5 μm particle size). The flow rate was 0.25 mL/min and packed reactor temperature was 40 °C. The trapped product was back-flush eluted from the ODS column to the detector by column-switching with an environmentally friendly mobile phase consisting of ethanol and phosphate buffer (0.04 M, pH 3.4) in the ratio of 5:95 (v/v). The eluent was monitored at emission and excitation wavelengths of 460 and 360 nm, respectively. The calibration curve was linear over the concentration range of 1.25–50 ng/mL with a detection limit of 0.08 ng/mL. The method was successfully applied to determine MTX in pharmaceutical formulations with mean percentage recovery ranging from 99.48 to 99.60.

Molecularly imprinted solid-phase extraction combined with electrochemical oxidation fluorimetry for the determination of methotrexate in human serum and urine

The method of synthesis and evaluation of molecularly imprinted polymers was reported. As a selective solid-phase extraction sorbent, the polymers were coupled with electrochemical fluorimetry detection for the efficient determination of methotrexate in serum and urine. Methotrexate was preconcentrated in the molecularly imprinted solid-phase extraction microcolumn packed with molecularly imprinted polymers, and then eluted. The eluate was detected by fluorescence spectrophotometer after electrochemical oxidation. The conditions of preconcentration, elution, electrochemical oxidation and determination were carefully studied. Under the selected experimental conditions, the calibration graph of the fluorescence intensity versus methotrexate concentration was linear from 4x10(-9) g mL(-1) to 5x10(-7) g mL(-1), and the detection limit was 8.2x10(-10) g mL(-1) (3sigma). The relative standard deviation was 3.92% (n=7) for 1x10(-7) g mL(-1) methotrexate. The experiments showed that the selectivity and sensitivity of fluorimetry could be greatly improved by the proposed method. This method has been successfully applied to the determination of methotrexate. At the same time, the binding characteristics of the polymers to the methotrexate were evaluated by batch and dynamic methods.

Flow-injection–electrochemical oxidation fluorimetry for determination of methotrexate

A novel fluorimetric model of on-line electrochemical oxidation for the determination of methotrexate (MTX) is described in this paper. The method was based on the oxidation of MTX to a highly fluorescent product, 2,4-diaminopteridine-6-carboxylic acid, by constant potential in the electrochemical oxidation flow cell. Stopped-flow techniques were employed. Under optimal conditions, the fluorescence intensity of 2,4-diaminopteridine-6-carboxylic acid was measured at excitation and emission wavelengths of 380 and 465 nm, respectively. The calibration graph was linear over concentrations of methotrexate in the range 2.0 x 10(-7)-1.0 x 10(-5) g/mL, with a detection limit of 5.2 x 10(-8) g/mL (3sigma). The method has been successfully applied to the determination of methotrexate in human urine samples and showed a percentage recovery in the range 94.3-102.5%.

Four-way calibration applied to the simultaneous determination of folic acid and methotrexate in urine samples

First-, second- and third-order calibration methods were investigated for the simultaneous determination of folic acid and methotrexate. The interest in the determination of these compounds is related to the fact that methotrexate inhibits the body's absorption of folic acid and prolonged treatment with methotrexate may lead to folic acid deficiency, and to the use of folic acid to cope with toxic side effects of methotrexate. Both analytes were converted into highly fluorescent compounds by oxidation with potassium permanganate, and the kinetics of the reaction was continuously monitored by recording the kinetics curves of fluorescence emission, the evolution with time of the emission spectra and the excitation-emission matrices (EEMs) of the samples at different reaction times. Direct determination of mixtures of both drugs in urine was accomplished on the basis of the evolution of the kinetics of EEMs by fluorescence measurements and four-way parallel-factor analysis (PARAFAC) or multiway partial least squares (N-PLS) chemometric calibration. The core consistency diagnostic (CORCONDIA) was employed to determine the correct number of factors in PARAFAC and the procedure converged to a choice of three factors, attributed to folic acid, methotrexate and to the sum of fluorescent species present in the urine.

Determination of methotrexate, several pteridines, and creatinine in human urine, previous oxidation with potassium permanganate, using HPLC with photometric and fluorimetric serial detection

A novel HPLC method, using UV and fluorimetric serial detection, for the simultaneous determination of methotrexate (MTX), five disease marker pteridines, and the reference metabolic subproduct creatinine (CREA) in human urine was established. A previous oxidation process using 10(-3) M KMnO4 (pH 5.0) and 35min of oxidation time was necessary to transform the analytes in the highly fluorescent pteridinic rings. CREA was not affected by the oxidative medium. Using Tris-HCl/NaCl buffer solution (pH 6.6) as mobile phase, MTX and the assayed pteridines were monitored by fluorescence at lambda(em) = 444 nm and lambda(ex) = 280 nm and creatinine was monitored by absorption measurements at lambda(abs) = 230 nm. All components were well resolved in approximately 7 min. Detection limits, according the criteria of Clayton and co-workers, were 10 ng ml(-1) for MTX, less than 1 ng ml(-1) for all of the pteridines, and 4 microg ml(-1) for CREA.

Determination of methotrexate in pharmaceutical formulations by flow injection analysis exploiting the reaction with potassium permanganate

A highly sensitive, precise and accurate flow injection procedure for the determination of methotrexate (MTX) was described. The method was based on oxidation of MTX into highly fluorescence product (2,4-diaminopteridine-6-carboxylic acid) by acidic potassium permanganate. A three-line manifold was used with potassium permanganate as an oxidant (3 mmol l(-1)) and sulfuric acid (6 mmol l(-1)) as carrier streams. The oxidation process was conducted at 65 degrees C through a reaction coil of 3 m (0.5 mm, i.d.). It was essential to eliminate the excess of potassium permanganate before passing to the detector using 8 mmol l(-1) sodium sulfite as a decolorizing stream. The fluorescence intensity was measured at excitation and emission wavelengths of 369 and 465 nm, respectively. The calibration graph was linear over the range 40-400 ng ml(-1) MTX. The developed method was successfully applied to the determination of MTX in pharmaceutical formulations, at a sampling rate of 90 sample h(-1) and showed a % recovery ranging from 99.96 to 100.07 and SD% ranging from 0.51 to 0.65%.

Second-Order Advantage Achieved with Four-Way Fluorescence Excitation−Emission−Kinetic Data Processed by Parallel Factor Analysis and Trilinear Least-Squares. Determination of Methotrexate and Leucovorin in Human Urine

Four-way fluorescence data recorded by following the kinetic evolution of excitation-emission fluorescence matrices (EEMs) have been analyzed by parallel factor analysis and trilinear least-squares algorithms. These methodologies exploit the second-order advantage of the studied data, allowing analyte concentrations to be estimated even in the presence of an uncalibrated fluorescent background. They were applied to the simultaneous determination of the components of the anticancer combination of methotrexate and leucovorin in human urine samples. Both analytes were converted into highly fluorescent compounds by oxidation with potassium permanganate, and the kinetics of the reaction was continuously monitored by recording full EEM of the samples at different reaction times. A commercial fast scanning spectrofluorometer has been used for the first time to measure the four-way EEM kinetic data. The rapid scanning instrument allows the acquisition of a complete EEM in 12 s at a wavelength scanning speed of 24 000 nm/min. The emission spectra were recorded from 335 to 490 nm at 5-nm intervals, exciting from 255 to 315 nm at 6-nm intervals. Ten successive EEMs were measured at 72-s intervals, to follow the fluorescence kinetic evolution of the mixture components. Good recoveries were obtained in synthetic binary samples and also in spiked urine samples. The excitation, emission, and kinetic time profiles recovered by both chemometric techniques are in good agreement with experimental observations.

Simultaneous determination of l- and d-methotrexate using a sequential injection analysis/amperometric biosensors system

A sequential injection analysis (SIA) is proposed for the simultaneous determination of L- and D-methotrexate (Mtx) using amperometric biosensors as detectors. A SIA system is proposed due to the highest precision and accuracy and lower consumption of sample and buffer. The amperometric biosensors used as detectors in SIA system were based on L-amino acid oxidase (L-AAOD) or/and L-glutamate oxidase (L-Glox) and horseradish peroxidase (HRP) for the assay of L-Mtx and D-amino acid oxidase (D-AAOD) and HRP for the assay of D-Mtx were selected. The linear concentration ranges are of pmol/l to nmol/l magnitude order, with very low limits of detection. The SIA/biosensors system can be used reliably on-line in synthesis process control, for the simultaneous assay of L- and D-Mtx with a frequency of 34 samples per hour.