Highlights

• Development of HPLC methods resolved ambiguities in MS-based detection of oxysterols.
• Design space modeling was applied to optimize HPLC separation of native oxysterols.
• The best performance was obtained using cyanopropyl and pentafluorophenyl columns.
• Insights on in-source fragmentation dynamics could differentiate isomeric oxysterols.

Highlights

• Dominant retention mechanisms of oligonucleotides identified on amide column.
• Solvophobic effects and H-bonding dominate oligonucleotide retention.
• Hydrophilic partitioning shown to be negligible under practical conditions.
• Descriptor-based model predicts retention from solvent and sequence properties.
• Protic co-solvents may improve selectivity for oligonucleotide separations.

Highlights

• Pressure, viscous friction, gradient delay and hardware design can drive key differences between UHPLC instruments.
• Using a systematic Design Space modeling framework facilitates a more seamless method transfer process.
• Alternative compensation strategies beyond traditional dwell volume correction are demonstrated.
• Elevated backpressure and low temperatures can further exacerbate method transfer challenges.

Abstract 

Lentisk (L) and apricot kernel (AKO) oils were characterized according to their phenolic, non-polar and antioxidant profiles. A quality by design (QbD) principles approach optimized phenolic analysis of samples through liquid chroma tography coupled to diode array and mass spectrometry (LC-DAD-MS) analyses, firstly reporting catechol in L and vanil lin and p-hydroxybenzoic acid in AKO oils. Non-polar fractions of L and AKO was featured by LC-DAD-MS analysis, determining 20 and 14 acylglycerols, respectively, most of them di- and tri-unsaturated acylglycerols. Moreover, analysis of fatty acids, tocopherols and phytosterols by GC-MS research unveiled high contents of unsaturated fatty acids (67% and 89% total content in L and AKO, respectively), mainly oleic, and relevant amounts of tocopherols (384 vs. 471 mg/ kg) and physterols (1852 vs. 3511 mg/kg) in L and AKO samples, respectively. Spectrophotometric assays determined low carotenoid (2.18 vs. 0.18 mg luteolin/kg) and chlorophyll (1.51 vs. 0.08 mg pheophytine/kg) contents in L and AKO samples, but demonstrated their high antioxidant/antiradical capacity values. High quality nutritional value of lentisk and apricot kernel oils together to their relevant antioxidant/antiradical properties may favor their use as source of natural bioactive compounds by food and pharmaceutical industries, favoring circular economy through the reuse of agricultural by-products.

Highlights

• Practical challenges of pH selection under reversed-phase conditions.   
• Using Design Space modeling to capture dynamic separation behavior of volatile and non-volatile buffer systems.
• Applying Design Space Comparison for in-depth buffer interchangeability studies.  
• Research outlook: Selectivity differences observed with NH₄⁺, K⁺, Na⁺, and Li⁺ buffer cations, highlighting varying salting-out effects.

Highlights

• A dual gradient approach is proposed to enhance the separation of oligonucleotides.
• Running a weak to strong ion pair gradient significantly expands the elution window.
• Combination of dual gradient with concave gradient program shows further benefits.
• The degree of freedom can be significantly improved to extend the design space.