Development of polyanion-metal ion solution systems to overcome phospholipids-related matrix effects in LC-MS/MS-based bioanalysis

Phospholipids-related matrix effects are a major source impacting the reproducibility of analyte quantification in LC-MS/MS-based bioanalysis. This study intended to evaluate different combinations of polyanion-metal ion based solution system for phospholipids removal and elimination of matrix effects in human plasma. Blank plasma samples or plasma samples spiked with model analytes were proceeded with different combinations of polyanions (dextran sulfate sodium (DSS) and alkalized colloidal silica (Ludox)) and metal ions (MnCl₂, LaCl₃, and ZrOCl₂) followed with acetonitrile-based protein precipitation. The representative classes of phospholipids and model analytes (acid, neutral, and base) were detected using multiple reaction monitoring mode. The polyanion-metal ion systems were explored for providing balanced analyte recovery and phospholipids removal by optimizing reagent concentrations or adding formic acid and citric acid as the shielding modifiers. The optimized polyanion-metal ion systems were further evaluated for eliminating matrix effects of non-polar and polar compounds. Any combinations of polyanions (DSS and Ludox) and metal ions (LaCl₃ and ZrOCl₂) could completely remove phospholipids at best-case scenario, while the analyte recovery is low for compounds with special chelation groups. Addition of formic acid or citric acid can improve analyte recovery but significantly decrease the removal efficiency of phospholipids. Optimized ZrOCl₂-Ludox/DSS systems provided efficient phospholipids removal (>85%) and adequate analyte recovery, and the systems also correctly eliminated ion suppression or enhancement of the non-polar and polar drugs. The developed ZrOCl₂-Ludox/DSS systems are cost-effective and versatile for balanced phospholipids removal and analyte recovery and provide adequate elimination of matrix effects.

Fast and Specific Screening of EPA/DHA-Enriched Phospholipids in Fish Oil Extracted from Different Species by HILIC-MS

Eicosapentaenoic acid- and docosahexaenoic acid-enriched phospholipids (PL_EPA/DHA) have versatile health-beneficial functions and can be well absorbed in the intestine. Herein, a precursor ion scan-driven hydrophilic interaction chromatography mass spectrometry (PreIS-HILIC-MS) method with the fatty acyl moieties of m/z 301.6 and 327.6 locked was established to specifically and selectively screen PL_EPA/DHA in different fish oil samples, including saury, grass carp, hairtail, and yellow croaker. Taking saury oil as an example, a total of 24 PL_EPA/DHA were successfully identified and quantified, including 20 PC_EPA/DHA and 4 PE_EPA/DHA. Finally, this method was validated in terms of sensitivity (limit of detection ≤ 4.15 μg·mL^-1), linearity (≥0.9979), precision (RSD_intraday ≤ 4.65%), and recovery (≥78.6%). The performance of the PreIS-HILIC-MS method was also compared with that of the traditional full-scan mode, and the former demonstrated its unique superiority in targeted screening of PL_EPA/DHA in fish oils.

The Effects of Sampling and Storage Conditions on the Metabolite Profile of the Marine Sponge Geodia barretti

Geodia barretti is a deep-sea marine sponge common in the north Atlantic and waters outside of Norway and Sweden. The sampling and subsequent treatment as well as storage of sponges for metabolomics analyses can be performed in different ways, the most commonly used being freezing (directly upon collection or later) or by storage in solvent, commonly ethanol, followed by freeze-drying. In this study we therefore investigated different sampling protocols and their effects on the detected metabolite profiles in liquid chromatography-mass spectrometry (LC-MS) using an untargeted metabolomics approach. Sponges (G. barretti) were collected outside the Swedish west coast and pieces from three sponge specimens were either flash frozen in liquid nitrogen, frozen later after the collection cruise, stored in ethanol or stored in methanol. The storage solvents as well as the actual sponge pieces were analyzed, all samples were analyzed with hydrophilic interaction liquid chromatography as well as reversed phase liquid chromatography with high resolution mass spectrometry using full-scan in positive and negative ionization mode. The data were evaluated using multivariate data analysis. The highest metabolite intensities were found in the frozen samples (flash frozen and frozen after sampling cruise) as well as in the storage solvents (methanol and ethanol). Metabolites extracted from the sponge pieces that had been stored in solvent were found in very low intensity, since the majority of metabolites were extracted to the solvents to a high degree. The exception being larger peptides and some lipids. The lowest variation between replicates were found in the flash frozen samples. In conclusion, the preferred method for sampling of sponges for metabolomics was found to be immediate freezing in liquid nitrogen. However, freezing the sponge samples after some time proved to be a reliable method as well, albeit with higher variation between the replicates. The study highlights the importance of saving ethanol extracts after preservation of specimens for biology studies; these valuable extracts could be further used in studies of natural products, chemosystematics or metabolomics.

Development and validation of an HILIC-MS/MS method by one-step precipitation for chloroquine in miniature pig plasma

Background:

Quantification of polar compounds such as chloroquine by revered-phase LC is a challenge because of poor retention and silanol interactions with stationary phase. Strong ion-pairing reagents added to mobile phases to improve reversed-phase retention and improve peak shape can be harmful for MS.

Results:

This new approach provides a rapid and sensitive method for the detection of chloroquine using hydrophilic interaction LC coupled to MS/MS (HILIC–MS/MS). Ammonium formate and formic acid were added to mobile phase to attain good peak shapes and the salified chloroquine as well retained in an HILIC column. Linearity, intra- and inter-day precision, accuracy, recovery, matrix effect and stability were evaluated during the validation process.

Conclusion:

The validated method has been successfully used in a PK study in miniature pigs, and paves way for future development.

Recent advances in the application of hydrophilic interaction chromatography for the analysis of biological matrices

Hydrophilic interaction chromatography (HILIC) is being increasingly used for the analysis of hydrophilic compounds in biological matrices. The complexity of biological samples demands adequate sample preparation procedures, specifically adjusted for HILIC analyses. Currently, most bioanalytical assays are performed on bare silica and ZIC-HILIC columns. Trends in HILIC for bioanalysis include smaller particle sizes and miniaturization of the analytical column. For complex biological samples, multidimensional techniques can separate and identify more compounds than 1D separations. The high volatility of the mobile phase, the added separation power and high sensitivity make MS the detection method of choice for bioanalysis using HILIC, although other detectors such as evaporative light scattering detection, charged aerosol detection and nuclear magnetic resonance have been reported.

Choosing the appropriate matrix to perform a scientifically meaningful lipemic plasma test in bioanalytical method validation

Laurence Mayrand-Provencher has obtained a Master of Science in Chemistry from Université de Montréal. With over 3 years of experience as a scientist in the bioanalysis industry, he is now a scientist in method development at Algorithme Pharma. His experiences have led him to conduct robust and effective method development of bioanalytical assays, specifically in the LC–MS/MS field.

Many regulatory agencies include in their guidelines the need to investigate the effect of lipemic plasma on the reliability of the data as part of a bioanalytical assay validation. Lipids can cause matrix effect, specificity and recovery issues, which can potentially lead to inaccurate data if left unaccounted for. However, finding the appropriate matrix type to be used to perform a lipemic plasma test is a major challenge, as the differences between those commercially available are not well known. The work reported herein describes the differences in lipid content between normal plasma, synthetic lipemic plasma mixes, and two types of natural lipemic plasma. The results obtained show that natural plasma with high triglycerides content should be used to perform a scientifically meaningful lipemic plasma test.

HILIC UHPLC-MS/MS for fast and sensitive bioanalysis: accounting for matrix effects in method development

BACKGROUND

Matrix effects are considered to be a main obstacle of quantitative bioanalytical LC-MS/MS methods. Therefore it is often required to minimize them in order to increase method reliability. HILIC has been referenced as one of possible approaches. However, there is a lack of experimental evidence in scientific literature so far.

METHODOLOGY

Matrix effects were evaluated using spiked serum samples after SPE and protein precipitation prior to UHPLC-ESI-MS/MS. Chromatography was performed in both HILIC and reversed-phase mode. The influence of the matrix effects on the signal response was assessed using a set of 34 compounds of pharmaceutical interest and post-extraction addition approach.

RESULTS

The advantages and drawbacks of the HILIC and reversed-phase chromatographic modes were compared and discussed in detail.

CONCLUSION

HILIC demonstrated the potential to reduce the occurrence of matrix effects when a more thorough sample pretreatment procedure such as SPE was applied.

Tracing and separating plasma components causing matrix effects in hydrophilic interaction chromatography-electrospray ionization mass spectrometry

Matrix effects on electrospray ionization were investigated for plasma samples analysed by hydrophilic interaction chromatography (HILIC) in gradient elution mode, and HILIC columns of different chemistries were tested for separation of plasma components and model analytes. By combining mass spectral data with post-column infusion traces, the following components of protein-precipitated plasma were identified and found to have significant effect on ionization: urea, creatinine, phosphocholine, lysophosphocholine, sphingomyelin, sodium ion, chloride ion, choline and proline betaine. The observed effect on ionization was both matrix-component and analyte dependent. The separation of identified plasma components and model analytes on eight columns was compared, using pair-wise linear correlation analysis and principal component analysis (PCA). Large changes in selectivity could be obtained by change of column, while smaller changes were seen when the mobile phase buffer was changed from ammonium formate pH 3.0 to ammonium acetate pH 4.5. While results from PCA and linear correlation analysis were largely in accord, linear correlation analysis was judged to be more straight-forward in terms of conduction and interpretation.

Salting-out assisted liquid–liquid extraction for bioanalysis

Salting-out assisted liquid–liquid extraction (SALLE) applies the salting-out effect to separate water-miscible organic solvent such as acetonitrile from plasma or other aqueous biofluids, and can extract a wide range of drug and metabolites, including many hydrophilic compounds. In most cases, the separated organic phase can be directly injected for bioanalysis, or with a simple dilution. SALLE provides similar simplicity to protein precipitation, but cleaner extracts due to a true phase separation. SALLE is also faster, more environmentally friendly and more cost-efficient than conventional liquid–liquid extraction and SPE. Through 96-well automation, SALLE can be easily integrated into the overall high-throughput LC–MS/MS bioanalysis strategy to increase productivity. This article provides a critical overview of the literatures on SALLE and perspectives of the future bioanalytical application of this often overlooked extraction technique. Important parameters impacting SALLE-LC–MS/MS assays are also discussed.