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Lack of knowledge on the expected concentration range or insufficient linear dynamic range of the analytical method applied are common challenges for the analytical scientist. Samples that are above the upper limit of quantification are typically diluted and reanalyzed. The analysis of undiluted highly concentrated samples can cause contamination of the system, while the dilution step is time consuming and as the case for any sample preparation step, also potentially leads to precipitation, adsorption or degradation of the analytes. ispartof: Journal of Chromatography A vol:1524 pages:101-107 ispartof: location:Netherlands status: published

Aim: To evaluate alternative analytical strategies to extend the dynamic range in quantitative LC–MS/MS. Methods & results: Two approaches based on prior or no prior knowledge of expected exposure levels were evaluated. These approaches make use of two analytical strategies, which include the use of more than one injection volume or dilution of sample extract with solvents or solvent mixtures. A total of 16 compounds with varying logP values were classified into polar and nonpolar groups and used in this evaluation. From the two analytical strategies, three workflows were derived. Conclusion: All three workflows were successfully evaluated and resulted in good accuracy (80–120%) for all the compound groups.

Eicosanoids, including prostaglandins and thromboxanes are lipid mediators synthetized from polyunsaturated fatty acids. They play an important role in cell signaling and are often reported as inflammatory markers. LC-MS/MS is the technique of choice for the analysis of these compounds, often in combination with advanced sample preparation techniques. Here we report a head to head comparison between an electrospray ionization source (ESI) and a new atmospheric pressure ionization source (UniSpray). The performance of both interfaces was evaluated in various matrices such as human plasma, pig colon and mouse colon. The UniSpray source shows an increase in method sensitivity up to a factor 5. Equivalent to better linearity and repeatability on various matrices as well as an increase in signal intensity were observed in comparison to ESI. publisher: Elsevier articletitle: Enhanced performance for the analysis of prostaglandins and thromboxanes by liquid chromatography-tandem mass spectrometry using a new atmospheric pressure ionization source journaltitle: Journal of Chromatography A articlelink: http://dx.doi.org/10.1016/j.chroma.2016.02.055 content_type: article copyright: Copyright © 2016 Elsevier B.V. All rights reserved. ispartof: Journal of Chromatography A vol:1440 pages:260-5 ispartof: location:Netherlands status: published