Fast quantitative determination of methylphenidate levels in rat plasma and brain ex vivo by MALDI‐MS/MS

Abstract

This study presents a simple and sensitive high-throughput matrix-assisted laser desorption/ionization time-of-flight tandem mass spectrometry (MALDI-MS/MS) method for ex vivo quantification of methylphenidate (MPH) in rat plasma and brain. The common MALDI matrix alpha-cyano-4-hydroxycinnamic acid was used to obtain an optimal dried droplet preparation. For method validation, standards diluted in plasma and brain homogenate prepared from untreated (control) rats were used. MPH was quantified within a concentration range of 0.1-40 ng/ml in plasma and 0.4-40 ng/ml in brain homogenate with an excellent linearity (R ≥ 0.9997) and good precision. The intra-day and inter-day accuracies fulfilled the FDA's ±15/20 critera. The recovery of MPH ranged from 93.8 to 98.5% and 87.2 to 99.8% in plasma and homogenate, respectively. We show that MPH is successfully quantified in plasma and brain homogenate of rats pre-treated with this drug using the internal standard calibration method. By means of this method, a linear correlation between plasma and brain concentration of MPH in rodents pre-treated with MPH was detected. The simple sample preparation based on liquid-liquid extraction and MALDI-MS/MS measurement requires approximately 10 s per sample, and this significantly reduces analysis time compared with other analytical methods. To the best of our knowledge, this is the first MALDI-MS/MS method for quantification of MPH in rat plasma and brain. Copyright © 2015 John Wiley & Sons, Ltd.

MALDI Matrices for the Analysis of Low Molecular Weight Compounds: Rational Design, Challenges and Perspectives

“…[33] Besides, hardware advances regarding the sensitivity, laser frequency and MS/MS capabilities brought many advantages such as high detection sensitivity, resolution accuracy, low sample consumption and rapid detection, which all significantly improve LMW compound analytics. [16,17,[34][35][36] Utilizing the matrix suppression effect (MSE) can provide high quality MALDI mass spectra (strong analyte signals with weak or none background interferences) and was first introduced by McCombie and Knochenmuss. [37] The authors demonstrated that MSE can be achieved by adjusting factors such as laser intensity and the molar ratio between matrix and analyte in the sample.…”

“…For example, polyethyleneoxide (PEO)‐type surfactants, which can suppress the ionization of analytes due to their high ionization efficiency, can be removed by carefully washing with a methanol solution [33] . Besides, hardware advances regarding the sensitivity, laser frequency and MS/MS capabilities brought many advantages such as high detection sensitivity, resolution accuracy, low sample consumption and rapid detection, which all significantly improve LMW compound analytics [16,17,34–36] …”

“…While MALDI MS is a much relied‐on standard tool for HMW analytics, LMW compounds (with m/z < 1000) – which cover a wide range of metabolite classes, e. g., amino acids, hormones, saccharides etc., are usually investigated with other MS methods [13–15] . But especially with the advance of MS imaging (MSI) techniques, there is now a significant interest to make LMW compounds analytics accessible with MALDI MS. MALDI‐MSI is a simple, rapid and sensitive method to visualize the spatial distribution of interesting molecules, e. g., small pharmaceutical drugs, on tissue sections [16,17] and to trace metabolic pathways [4] . Yet traditional MALDI matrices – small molecules with conjugated systems and acidic or basic functional groups ‐ usually do not support the analysis of LMW compounds [18] as they desorb and ionize themselves, generating large amount of ion peaks in the LMW region [19] .…”

Plausible diagnostic value of urinary isomeric dimethylarginine ratio for diabetic nephropathy

“…We previously reported a matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) absolute quantification method and demonstrated it for the estimation of ADMA and SDMA concentrations from urine 31 . For this study, an optimized and validated MALDI MS/MS method 32 has been employed to selectively measure ASR using the signature product ion ratio of ADMA and SDMA. The method was thoroughly tested for precision, accuracy, performance, and cross-platform validation (please see Supplemental Fig.…”