An atmospheric pressure ionization source using a high voltage target compared to electrospray ionization for the LC/MS analysis of pharmaceutical compounds

Quantification of three antineoplastic agents in urine using the UniSpray ionisation source

BACKGROUND

Many guidelines and safety measures led to a decrease in exposure to antineoplastic agents. Since healthcare workers are often exposed to lower concentrations than patients, a sensitive method is needed to quantify occupational exposure.

OBJECTIVE

The aim of this study was to develop and validate a sensitive method for simultaneous detection and quantification of cyclophosphamide, ifosfamide and paclitaxel in urine by use of UPLC-MS/MS with a UniSpray ionisation source.

METHODS

Compounds were extracted from urine using Novum simplified liquid extraction cartridges, separated on a C18 column, ionised by a UniSpray ionisation source and detected with MS/MS. In the second part of the study, a field study was performed to assess occupational exposure to antineoplastic agents.

RESULTS

Eighty-three samples from healthcare workers were analysed and resulted in seventeen samples containing quantifiable concentrations of at least one compound. In conclusion, a sensitive method for simultaneous detection and quantification of cyclophosphamide (LLOQ 0.05 ng/mL), ifosfamide (LLOQ 0.3 ng/mL) and paclitaxel (LLOQ 0.7 ng/mL) was developed and validated.

Development and validation of a quantitative method for 15 antiviral drugs in poultry muscle using liquid chromatography coupled to tandem mass spectrometry

The objective of this work was to develop a quantitative multi-residue method for analysing antiviral drug residues and their metabolites in poultry meat samples. Antiviral drugs are not licensed for the treatment of influenza in food producing animals. However, there have been some reports indicating their illegal use in poultry. In this study, a method was developed for the analysis of 15 antiviral drug residues in poultry muscle (chicken, duck, quail and turkey) using liquid chromatography coupled to tandem mass spectrometry. This included 13 drugs against influenza and associated metabolites, but also two drugs employed for the treatment of herpes (acyclovir and ganciclovir). The method required the development of a novel chromatographic separation using a hydrophilic interaction chromatographic (HILIC) BEH amide column, which was necessary to retain the highly polar compounds. The analytes were detected using a triple quadrupole mass spectrometer operating in positive electrospray ionization mode. A range of different sample preparation protocols suitable for polar compounds were evaluated. The most effective procedure was based on a simple acetonitrile-based protein precipitation step followed by a further dilution in a methanol/water solution. The confirmatory method was validated according to the EU 2021/808 guidelines on different species including chicken, duck, turkey and quail. The validation was performed using various calibration curves ranging from 0.1 µg kg^-1to 200 µg kg^-1, according to the analyte. Depending on the analyte sensitivity, decision limits achieved ranged from 0.12 µg kg^-1 for arbidol to 34.7 µg kg^-1 for ribavirin. Overall, the reproducibility precision values ranged from 2.8% to 22.7% and the recoveries from 84% to 127%. The method was applied to 120 commercial poultry samples from the Irish market, which were all found to be residue-free.

A comparative study of UniSpray and electrospray sources for the ionization of neuropeptides in liquid chromatography tandem mass spectrometry

Despite the extensive use of electrospray ionization (ESI) for the quantification of neuropeptides by liquid chromatography-tandem mass spectrometry (LC-MS/MS), poor ionization and transmission efficiency are described for this ionization interface. A new atmospheric pressure ionization source, named UniSpray, was recently developed and commercialized. In this study, the LC-MS performance of this new ionization interface is evaluated and compared with ESI for the quantification of seven neuropeptides. Besides comparison of signal intensities and charge state distributions, also signal-to-noise (S/N) ratios and accuracy and precision were assessed. Additionally, matrix effects of human precipitated plasma and rat microdialysate were evaluated as well as the effect of three supercharging agents on the ionization of the seven neuropeptides. UniSpray ionization resulted in signal intensities four to eight times higher at the optimal capillary/impactor voltage for all seven neuropeptides. S/N values at the other hand only increased by not more than a twofold when the UniSpray source was used. Moreover, UniSpray ionization resulted in a shift towards lower charge states for some neuropeptides. Evaluation of the matrix effects by a post-column infusion set-up resulted in different infusion profiles between ESI and UniSpray. The charge state distributions of the neuropeptides obtained with UniSpray are highly comparable with ESI. Finally, the effect of the supercharging agents on the ionization of the neuropeptides tends to be peptide-dependent with both ionization sources.

Current developments in LC-MS for pharmaceutical analysis

Liquid chromatography (LC) based techniques in combination with mass spectrometry (MS) detection have had a large impact on the development of new pharmaceuticals in the past decades.

Study of temporal variability of salivary cortisol and cortisone by LC-MS/MS using a new atmospheric pressure ionization source

There is a growing interest concerning the relevance of salivary cortisone levels in stress-related research. However, studies investigating morning patterns and day-to-day variability of cortisone versus cortisol levels are lacking. Cortisol and cortisone analysis by liquid chromatography-tandem mass spectroscopy (LC-MS/MS) has been widely used for routine laboratory measurements in the last years. The aim of this study was to develop an ultra-performance LC-MS/MS method for the simultaneous quantification of salivary cortisol and cortisone levels for assessing the temporal variability of these hormones. Saliva samples were collected from 18 healthy volunteers at 0, 15, and 30 min after awakening on each day for 1 week and analysed with the newly developed method. We used a novel atmospheric pressure ionization source, which resulted in high sensitivity and specificity for both cortisol and cortisone as well as higher peak values and signal-to-noise ratio as compared with the electrospray ionization source. Cortisone showed similar morning patterns as cortisol: a 25% and 49% increase in levels at 15 and 30 min after awakening, respectively. Most cortisone indices showed somewhat lower day-to-day variability and were less affected by state-related covariates. We recommend further exploration of the potential of salivary cortisone as a biomarker in stress-related research.

Comparison of electrospray and UniSpray, a novel atmospheric pressure ionization interface, for LC-MS/MS analysis of 81 pesticide residues in food and water matrices

In mass spectrometry, the type and design of ionization source play a key role on the performance of a given instrument. Therefore, it is of paramount importance to evaluate newly developed sources for their suitability to analyze food contaminants like pesticide residues. Here, we carried out a head-to-head comparison of key extraction and analytical performance parameters of an electrospray ionization (ESI) source with a new atmospheric pressure ionization source, UniSpray (US). The two interfaces were evaluated in three matrices of different properties (coffee, apple, and water) to determine if multiresidue analysis of 81 pesticides by QuEChERS extraction and LC-MS/MS analysis could be improved. Depending on the matrix and irrespective of the chemical class, US provided a tremendous gain in signal intensity (22- to 32-fold in peak area, 6- to 7-fold in peak height), a threefold to fourfold increase in signal-to-noise ratio, a mild gain in the range of compounds that can be quantified, and up to twofold improvement of recovery. UniSpray offered comparable linearity and precision of the analyses with ESI, and did not affect the ion ratio. A gain in sensitivity of many compounds was observed with US, but in general, the two ionization interfaces did not show significant difference in LOD and LOQ. UniSpray suffered less signal suppression; the matrix effect was in average 3 to 4 times more pronounced, but showed better values than ESI. With no effect on recovery efficiency, US improved the overall process efficiency 3 to 4 times more than ESI. Graphical abstract.

Development of a mass spectrometry based detection method for the mitochondrion-derived peptide MOTS-c in plasma samples for doping control purposes

RATIONALE

The mitochondrial open reading frame of 12S rRNA type-c (MOTS-c) peptide was recently discovered and described to control metabolic homeostasis through AMPK activation along with AICAR accumulation. Consequently, it appears advisable to monitor the potential use of synthetic MOTS-c in sports, and a detection method suitable for sports drug testing purposes is necessary.

METHODS

For the detection of MOTS-c in doping control plasma samples, a test method employing liquid chromatography and mass spectrometry (LC/MS) was developed. Following optimization, the assay was comprehensively validated and additional parameters such as the (long-term) stability and in vitro metabolism of the peptide were evaluated. In order to determine endogenous MOTS-c reference limits, the results generated by LC/MS-based detection were compared with those obtained with a commercially available enzyme-linked immunosorbent assay (ELISA).

RESULTS

The LC/MS-based test method was fully validated for quantitative results interpretation according to the World Anti-Doping Agency's International Standard for Laboratories (WADA's ISL). It was found to be specific and sensitive, enabling a lower limit of detection (LLOD) for hMOTS-c in plasma at 100 pg/mL. Following optimization, animal MOTS-c analogues and four metabolites as well as two oxidation products were implemented. However, endogenous levels of a reference population of 20 healthy subjects studied by ELISA experiments (45.9-218.5 ng/mL) could not be confirmed by LC/MS.

CONCLUSIONS

A mass spectrometric detection assay for MOTS-c in human plasma samples was developed and successfully validated according to WADA's ISL, providing an additional tool for future doping control purposes. Besides MOTS-c, the assay also includes four in vitro derived metabolites and two oxidation products, which might further improve the traceability of the drug. The analytical approach was compared with a commercially available ELISA, and considerable differences in measured MOTS-c levels were observed.

Seeking universal detectors for analytical characterizations

It is highly desirable to have a universal detector that can detect all types of compounds and give a uniform response regardless of the physiochemical properties of the compounds. With such a universal detector, all components in a sample can be accurately quantified without the need for individual standards. This is especially needed for the characterization of unknowns and for non-targeted analysis, or for samples that have no isolated standards available for each component. Over the years, much effort has been put into seeking a universal detection technology. In this review, we discuss the commonly used detectors for analytical characterization, including UV, RI, ELSD, CAD, CLND, FID, VUV, MS, NMR, and hyphenated detection, with the focuses on the "universal" features of these detectors regarding the types of molecules they can detect and the uniformity of responses.