Qualitative and Quantitative Analysis of Pharmaceutical Compounds by MALDI-TOF Mass Spectrometry

Abstract

In this report, we discuss key issues for the successful application of MALDI-TOF mass spectrometry to quantify drugs. These include choice and preparation of matrix, nature of cationization agent, automation, and data analysis procedures. The high molecular weight matrix meso-tetrakis(pentafluorophenyl)porphyrin eliminates chemical noise in the low-mass range, a "brushing" spotting technique in combination with prestructured target plates enables fast preparation of homogeneous matrix crystals, and addition of Li+ leads to intense cationized drug species. Complex biological samples were cleaned up using a 96-well solid-phase extraction plate, and the purified samples were automatically spotted by a pipetting robot. To obtain a suitable data analysis procedure for the quantitative analysis of drugs by MALDI-TOF mass spectrometry, various data processing parameters were evaluated on our two model drugs lopinavir and ritonavir. Finally, and most importantly, it is shown that the above-described procedure can be successfully applied to quantify clinically relevant concentrations of lopinavir, an HIV protease inhibitor, in extracts of small numbers of peripheral blood mononuclear cells (1 x 10(6)).

Biomedical application of MALDI mass spectrometry for small‐molecule analysis

“…Dwell time of the ions does not contribute significantly to the analysis time, although the detection time of ions can take second(s) per scan in Fourier-transform ion cyclotron resonance (FTICR) MS and Orbitrap MS. With a high repetition rate laser that fires at 1,000-2,000 Hz, an averaged mass spectrum of high quality can be obtained in a few seconds with MALDI-time-of-flight (TOF) MS or MALDI-triple quadrupole MS (Hatsis et al, 2003;McLean, Russell, & Russell, 2003;Moskovets et al, 2006;Rathore et al, 2008). For quantitative analysis of, for instance, HIV protease inhibitors, analysis times for a single spot on the target plate have been reported of $3 min for MALDI-FTICR MS (20 Hz laser), $30 sec for MALDI-TOF MS (50 Hz laser), and $5 sec for MALDI-triple quadrupole MS (1,000 Hz laser; van Kampen et al, 2006Kampen et al, , 2008aKampen et al, ,b, 2009b. Recently, an analysis time of 1.75 min for an entire 384-well target plate was reported for an assay to screen for small-molecule inhibitors of enzymes with MALDI-triple quadrupole MS (Rathore et al, 2008).…”

“…Srinivasan et al (1999) reported that some porphyrins could act as auto-matrices, and various porphyrins have been tested as matrix in MALDI-MS (Jones, Lamb, & Lim, 1995;Chen & Ling, 2002). In particular, meso-tetrakis(pentafluorophenyl)porphyrin (F20TPP; MW 974) appears to be a useful matrix for the analysis of small molecules with MALDI-TOF MS (Ayorinde et al, 1999;Ayorinde, Garvin, & Saeed, 2000;Hlongwane et al, 2001;Ayorinde, Bezabeh, & Delves, 2003;van Kampen et al, 2006van Kampen et al, , 2007Yu et al, 2006;Kosanam et al, 2007). Ayorinde et al (1999) compared the use of a-cyano-hydroxycinnamic acid (CHCA) and F20TPP for the analysis of alkylphenol ethoxylates and found that F20TPP generated spectra with significantly less matrix interference in the low mass range (see Fig.…”

“…Further studies showed that F20TPP is a suitable matrix for the determination and quantification of fatty acids (Ayorinde, Garvin, & Saeed, 2000;Hlongwane et al, 2001;Yu et al, 2006), and to determine the constituents of non-alcoholic beverages such as sugars, ascorbic acid, and citric acid (Ayorinde, Bezabeh, & Delves, 2003). F20TPP is also a useful matrix for MALDI-TOF analysis of several pharmaceutical compounds such as HIV protease inhibitors, reverse transcriptase inhibitors, and antibiotics (van Kampen et al, 2006). In addition, the matrix can be used for the quantitative analysis of lopinavir and ritonavir in cell lysates (van Kampen et al, 2006(van Kampen et al, , 2007.…”

Quantitative matrix-assisted laser desorption/ionization mass spectrometry

“…van Kampen and colleagues [33] examined such issues as the matrix (i.e. nature and preparation), the inclusion of Li þ to facilitate formation of cationized drug species, automation and data analysis procedures.…”

Determination of the antiretroviral drug tenofovir in plasma from HIV‐infected adults by ultrafast isotope dilution MALDI‐triple quadrupole tandem mass spectrometry

“…plasma, serum, urine and cerebrospinal fluid). [10] Since the introduction of a mass spectrometry platform which consists of MALDI source with a high repletion solid-state UV laser (1 kHz, 349 nm) in combination with a triple quadrupole mass spectrometer (MALDI-QqQ-MS) few articles have been reported demonstrating that this new technology can be applied for high accurate and precise determinations of concentrations of small molecules [11] with CVs <15/20%, according to the most recent FDA guidelines. [12] Therefore, we decided to use this new technology and to study its feasibility for high-throughput and ultrafast measurement of plasma concentrations of the antiretroviral drug TNV in plasma from HIV adults using an isotope dilution method.…”