Determination of methotrexate and indomethacin in urine using SPE-LC-DAD after derivatization

DEVELOPMENT AND VALIDATION OF A HPLC-UV BASED METHOD FOR THE EXTRACTION AND QUANTIFICATION OF METHOTREXATE IN THE SKIN

An innovative and sensitive HPLC-UV method for the extraction and quantification of methotrexate (MTX) in skin layers was developed and validated. Due to the physico-chemical characteristics of the drug and the nature of the tissue, it was necessary to use folic acid (FA) as internal standard for MTX quantification in the dermis. MTX (and FA) analysis was performed on a Phenomenex Jupiter C18 column, using 50 mM sodium acetate buffer (pH 3.6) and methanol mixture (87:13, v/v) as mobile phase, pumped at 1 ml/min. The absorbance was monitored at 290 nm. The method resulted to be selective, linear in the range 0.11-8.49 μg/ml for extraction solvent and 0.05-8.94 μg/ml for pH 7.4 PBS, precise and accurate, with a LLOQ of 0.11 μg/ml (extraction solvent) and 0.05 μg/ml (pH 7.4 PBS). The method developed resulted to be suitable for the quantification of MTX in the skin layers at the end of in vitro permeation experiments; the overall mass balance was 96.5 ± 1.4 %, in line with the requirement of the OECD guideline for the testing of the chemicals (Skin absorption: in vitro method) (OECD, 2004).

Analytical methodologies for determination of methotrexate and its metabolites in pharmaceutical, biological and environmental samples

Methotrexate (MTX) is a folate antagonist drug used for several diseases, such as cancers, various malignancies, rheumatoid arthritis (RA) and inflammatory bowel disease. Due to its structural features, including the presence of two carboxylic acid groups and its low native fluorescence, there are some challenges to develop analytical methods for its determination. MTX is metabolized to 7-hydroxymethotrexate (7-OH-MTX), 2,4-diamino-N10-methylpteroic acid (DAMPA), and the active MTX polyglutamates (MTXPGs) in the liver, intestine, and red blood cells (RBCs), respectively. Additionally, the drug has a narrow therapeutic range; hence, its therapeutic drug monitoring (TDM) is necessary to regulate the pharmacokinetics of the drug and to decrease the risk of toxicity. Due to environmental toxicity of MTX; its sensitive, fast and low cost determination in workplace environments is of great interest. A large number of methodologies including high performance liquid chromatography equipped with UV-visible, fluorescence, or electrochemical detection, liquid chromatography-mass spectroscopy, capillary electrophoresis, UV-visible spectrophotometry, and electrochemical methods have been developed for the quantitation of MTX and its metabolites in pharmaceutical, biological, and environmental samples. This paper will attempt to review several published methodologies and the instrumental conditions, which have been applied to measure MTX and its metabolites within the last decade.

UPLC-MS/MS Analysis of Methotrexate in Human Plasma and Comparison with the Fluorescence Polarization Immunoassay

Methotrexate (MTX) plasma concentration is routinely monitored to guide the dosage regimen of rescue drugs. This study aims to develop and validate an ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method for plasma MTX analysis, and to establish its agreement with the fluorescence polarization immunoassay (FPIA) in patients with high-dose MTX therapy. Separation was achieved by gradient elution with methanol and water (0.05% formic acid) at 40°C with a run time of 3 min. The intra- and inter-day inaccuracy and imprecision of the UPLC-MS/MS method were -4.25 to 3.1 and less than 7.63%, respectively. The IS-normalized recovery and matrix effect were 87.05 to 92.81 and 124.43 to 134.57%. The correlation coefficients between UPLC-MS/MS and FPIA were greater than 0.98. The UPLC-MS/MS method was in agreement with the FPIA at high levels of MTX (1.0 - 100 μmol/L), but not at low levels (0.01 - 1.0 μmol/L). Further studies are warranted to confirm these results.

Identification of impurities in methotrexate drug substances using high-performance liquid chromatography coupled with a photodiode array detector and Fourier transform ion cyclotron resonance mass spectrometry

RATIONALE

Methotrexate (MTX) is an antineoplastic therapeutic medicine that acts as an antimetabolite of folic acid. In this study we identified the impurities in MTX drug substances produced by different manufacturers and in different batches using high-performance liquid chromatography coupled with a photodiode array detector and Fourier transform ion cyclotron resonance mass spectrometry (HPLC-PDA/FTICR-MS).

METHODS

MTX and its impurities were separated on a Restek Pinnacle II C18 column (250 × 4.6 mm, 5 µm) with a gradient elution system composed of 0.2% formic acid and acetonitrile at a flow rate of 1.0 mL/min. Ultraviolet (UV) detection was set at 305 nm. Mass detection was carried out using FTICR-MS with full-scan mass analysis at a resolving power of 100 000 coupled with multiple-stage mass analysis using a parent list of compounds.

RESULTS

Fifteen impurities were detected in MTX drug substances, and their structures were predicted from using HPLC-PDA/FTICR-MS data, including their UV spectra, high-resolution mass spectrometry (HRMS), fragmentation patterns, and MS(n) spectra. Ten of the impurities detected in the MTX drug substances are reported for the first time. There was a high abundance of esterified impurities in some batches of MTX drug substances, over the identification threshold of International Conference on Harmonization (ICH) guidelines, which requires particular attention.

CONCLUSIONS

This paper describes a HPLC-PDA/FTICR-MS method to profile and identify impurities in MTX drug substances. The results suggest that HPLC-PDA/FTICR-MS is a valuable analytical technique for the rapid identification of impurities.

A liquid chromatography method with single quadrupole mass spectrometry for quantitative determination of indomethacin in maternal plasma and urine of pregnant patients

A liquid chromatography with single quadrupole mass spectrometry method was developed for the quantitative determination of indomethacin in the maternal plasma and urine of pregnant patients under treatment. A deuterium-labeled isotope of indomethacin (d4-indomethacin) was used as an internal standard. The maternal plasma and urine samples were acidified with 1.0M HCl then extracted with chloroform to achieve the extraction recovery range of 94-104% with variation less than 11%. Chromatographic separation was achieved by a Waters Symmetry C₁₈ column with isocratic elution of 0.05% (v/v) formic acid aqueous solution and acetonitrile (47:53, v/v). An in-source fragmentation was applied on the single quadrupole mass spectrometer equipped with an electrospray ionization source at positive mode. The LC-ESI-MS quantification was performed in the selected ion monitoring mode targeting ions at m/z 139 for indomethacin and m/z 143 for its internal standard. The calibration curves were linear in the concentration ranges between 14.8 and 2.97 × 10(3) ng/mL for plasma samples and between 10.5 and 4.21 × 10(3) ng/mL for urine samples. The relative standard deviation of this method was less than 8% for intra- and inter-day assays, and the accuracy ranged between 90% and 108%.

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.

Development and validation of a liquid chromatography method for simultaneous determination of three process-related impurities: yeastolates, triton X-100 and methotrexate

Yeastolates, triton X-100 (TX-100) and methotrexate (MTX) are common process-related impurities (PRI) in cell-based bioproduction of many active biopharmaceuticals. In this study, a reverse phase high performance liquid chromatography (RP-HPLC) method coupled with ultraviolet (UV) detection was developed for simultaneous determination and quantitation of these impurities. The chromatographic separation was achieved using a Jupiter C4 column and analyses of yeastolates, TX-100 and MTX were monitored at 257, 280 and 302 nm, respectively. The method was further validated with respect to selectivity, linearity, limit of detection (LOD), limit of quantitation (LOQ), precision and accuracy. The limits of quantitation for yeastolates, TX-100 and MTX were determined to be 27 ppm, 10 ppm and 41 ppb, respectively. Finally, the suitability of the method for analyses of recombinant human hyaluronidase (rHuPH20) in-process (viral inactivation, QFF, PS, APB and CHT filtered, final viral filtrate) and final manufacturing materials was demonstrated, and trace levels of yeastolates, TX-100 and MTX were reliably measured except for three matrices early in the purification process in which TX-100 was not accurately determined due to interfering effects.