Effect of organic mobile phase composition on signal responses for selected polyalkene additive compounds by liquid chromatography–mass spectrometry

Application of hydrophilic interaction liquid chromatography coupled with tandem mass spectrometry for the retention and sensitivity studies of antisense oligonucleotides

The aim of the present investigation was application of hydrophilic interaction liquid chromatography as an alternative chromatographic approach for the study of antisense oligonucleotides. The influence of several mobile phases, differing with the salt type, their concentration and pH value on the retention and the separation of antisense oligonucleotides has been examined for this purpose. Four different stationary phases were also applied including unmodified silica, silica modified with the use of sulfobetaine groups, polyhydroxy and aminopropyl groups. Such wide range of tested conditions has been useful in better understanding of the retention mechanism of tested compounds. The results obtained during this investigation indicated that greater retention, greater peaks symmetry, as well as more effective separation of oligonucleotides, were obtained for the zwitterionic stationary phase. Moreover, the optimization of tandem mass spectrometry parameters with the use of Central Composite Design was performed and different mobile phases were tested to choose that one, which provided the greatest antisense oligonucleotides peak areas in Multiple Reaction Monitoring mode and consequently, the greatest possible sensitivity. Hydrophilic interaction liquid chromatography was compared with the ion pair chromatography, commonly used in the analysis of oligonucleotides. Both techniques were compared in terms of selectivity of separation as well as the sensitivity of their determination. Obtained results proved that ion pair chromatography provided better results in terms of separation efficiency and peak areas in Multiple Reaction Monitoring for tested conditions. However, these results do not preclude application of hydrophilic interaction liquid chromatography as an alternative chromatographic approach for the oligonucleotides analysis especially when a mobile phase without ion pair reagents is required.

Anti-inflammatory effects of cinnamon extract and identification of active compounds influencing the TLR2 and TLR4 signaling pathways

Cinnamon extract and its active compounds attenuate TLR2-/TLR4-mediated inflammatory processes.

Recent developments in atmospheric pressure photoionization-mass spectrometry

Recent developments in atmospheric pressure photoionization (APPI), which is one of the three most important ionization techniques in liquid chromatography-mass spectrometry, are reviewed. The emphasis is on the practical aspects of APPI analysis, its combination with different separation techniques, novel instrumental developments - especially in gas chromatography and ambient mass spectrometry - and the applications that have appeared in 2009-2014. © 2015 Wiley Periodicals, Inc. Mass Spec Rev 36:423-449, 2017.

Acetonitrile Ion Suppression in Atmospheric Pressure Ionization Mass Spectrometry

Efforts to analyze trace levels of cyclic peroxides by liquid chromatography/mass spectrometry gave evidence that acetonitrile suppressed ion formation. Further investigations extended this discovery to ketones, linear peroxides, esters, and possibly many other types of compounds, including triazole and menadione. Direct ionization suppression caused by acetonitrile was observed for multiple adduct types in both electrospray ionization and atmospheric pressure chemical ionization. The addition of only 2% acetonitrile significantly decreased the sensitivity of analyte response. Efforts to identify the mechanism were made using various nitriles. The ion suppression was reduced by substitution of an acetonitrile hydrogen with an electron-withdrawing group, but was exacerbated by electron-donating or steric groups adjacent to the nitrile. Although current theory does not explain this phenomenon, we propose that polar interactions between the various functionalities and the nitrile may be forming neutral aggregates that manifest as ionization suppression. Graphical Abstract ᅟ.

Analysis of potential migrants from plastic materials in milk by liquid chromatography-mass spectrometry with liquid-liquid extraction and low-temperature purification

A simple and fast analytical method was developed for the determination of six UV stabilizers (Cyasorb UV-1164, Tinuvin P, Tinuvin 234, Tinuvin 326, Tinuvin 327, and Tinuvin 1577) and five antioxidants (Irgafos 168, Irganox 1010, Irganox 3114, Irganox 3790, and Irganox 565) in milk. For sample preparation liquid-liquid extraction with low-temperature purification combined with centrifugation was used to remove fats, proteins, and sugars. After the cleanup step, the sample was analyzed with high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS). External standard and matrix calibrations were tested. External calibration proved to be acceptable for Tinuvin P, Tinuvin 234, Tinuvin 326, Tinuvin 327, Irganox 3114, and Irganox 3790. The method was successfully validated with matrix calibration for all compounds. Method detection limits were between 0.25 and 10 μg/kg. Accuracies ranged from 93 to 109%, and intraday precisions were <13%.

High-throughput quantification of stabilizers in polymeric materials by flow injection tandem mass spectrometry

RATIONALE

High-throughput methods for identification and quantification of stabilizers in plastic materials are of significant importance in order to evaluate the suitability of materials of unknown origin for specific application areas, to clarify reasons for failure of materials, or for comparison of materials from different sources.

METHODS

In the present study, a highly sensitive and rapid flow injection method coupled to selected reaction monitoring mass spectrometry (MS) for comprehensive analysis of 21 polymer stabilizers in polyolefins is demonstrated. A critical factor for this approach is the choice of ionization mode, as no separation was performed prior to MS detection. Differences between several ionization techniques regarding matrix effects are reported.

RESULTS

Atmospheric pressure chemical ionization was found to be the most suitable ionization technique, with no significant matrix effects observed. The developed method has a linear dynamic range over two to three orders of magnitude with correlation coefficients better than 0.99 for all studied analytes. Following a multistep sample preparation protocol, the method allowed quantification down to minimum values of between 0.0001 and 0.04 wt% depending on the type of stabilizer. Results were compared to an established chromatographic approach and showed very good correlation (bias below 7.5%).

CONCLUSIONS

The applicability of the optimized method could be demonstrated for both the qualitative and quantitative determination of polymer stabilizers in polyolefins. Furthermore, the described approach yields a complete analysis in a much shorter time than can be achieved with commonly applied chromatographic methods.

Quantitative analysis of five tobacco-specific N-nitrosamines in urine by liquid chromatography-atmospheric pressure ionization tandem mass spectrometry

A liquid chromatography tandem mass spectrometry (LC/MS/MS) method was developed and validated for the determination of five total tobacco-specific N-nitrosamines (TSNA), including free and conjugated forms in urine. The limits of detection for 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol, N'-nitrosonornicotine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone, N'-nitrosoanatabine and N'-nitrosoanabasine were 0.6, 0.6, 10.0, 0.4 and 0.4 pg/mL, respectively, with a linear calibration range of up to 20,000 pg/mL. Intra- and inter-day precision for TSNA measurements ranged from 0.82 to 3.67% and from 2.04 to 7.73% respectively. For total TSNAs, the β-glucuronidase amount was optimized for hydrolysis time and yield. Different liquid chromatography columns and mobile phases with different pH conditions were evaluated. The validated method was then applied to 50 smoker and 30 nonsmoker urine samples. Our results suggest that this sensitive and relatively simple analytical method is suitable for application to epidemiological investigations of health risks associated with the exposure to tobacco smoke or secondhand smoke in both smokers and nonsmokers.

Systematic evaluation of acetone and acetonitrile for use in hydrophilic interaction liquid chromatography coupled with electrospray ionization mass spectrometry of basic small molecules

Sub-2-µm particle size hydrophilic interaction liquid chromatography [HILIC] combined with mass spectrometry has been increasing in popularity as a complementary technique to reversed-phase LC for the analysis of polar analytes. The organic-rich mobile phase associated with HILIC techniques provides increases in compound ionization, due to increased desolvation efficiency during electrospray ionisation mass spectrometric (ESI-MS) analysis. Although recent publications illustrated selectivity and response comparisons between reversed-phase LC/MS and HILIC LC/MS, there are limited discussions evaluating the optimisation of the mass spectrometry parameters regarding analytes and alternative mobile phases. The use of acetone as an alternative organic modifier in HILIC has been investigated with respect to signal-to-noise in ESI-MS for a variety of polar analytes. Analyte reponses were measured based on a variety of cone and capillary voltages at low and high pH in both acetone and acetonitrile. In order to visualise compound behaviour in the ESI source, surface plots were constructed to assist in interpreting the observed results. The use of acetone in ESI is complicated at low m/z due to the formation of condensation products. Favourable responses were observed for certain analytes and we envisage offering an insight into the use of acetone as an alternative to acetonitrile under certain analytical conditions for particular compound classifications for small molecule analysis. We also highlight the importance of optimising source voltages in order to obtain the maximum signal stability and sensitivity, which are invariably, highly solvent composition dependent parameters.

Application of liquid chromatography in polymer non-ionic antistatic additives analysis

This article investigates the applicability of HPLC-UV, ultra performance LC-evaporative light-scattering detection (UPLC-ELSD), HPLC-ESI(+)-MS and HPLC-hybrid linear ion trap (LTQ) Orbitrap MS for the analysis of different non-ionic antistatic additives, Span 20, Span 60, Span 65, Span 80, Span 85 (sorbitan fatty acid esters), Atmer 129 (glycerol fatty acid ester) and Atmer 163 (ethoxylated alkylamine). Several alkyl chain length or different degrees of esterification of polyol derivatives can be present in commercial mixtures of these polymer additives. Therefore, their identification and quantification is complicated. Qualitative composition of the studied compounds was analysed by MS. HPLC-UV, UPLC-ELSD and HPLC-LTQ Orbitrap MS methods were applied to the quantitative determination of the different Spans, Atmer 129 and Atmer 163, respectively. Quality parameters of these methods were established and no derivatization was necessary.