Highlights:

• Innovative QbD-based approach for robustness testing of a compendial HPLC method.
• A Design Space was constructed to study the robustness in silico.
• Required peak resolution of 2.0 could not be reached in all experiments.
• After adjusting the gradient time the requirements were fulfilled.
• A separate “Eluent Design Space” study was performed.

This study describes the development of liquid chromatographic methods for the simultaneous separation of some of the most popular local anesthetics in pharmaceutical preparations and medical praxis (benzocaine, bupivacaine, chloroprocaine lidocaine, oxybuprocaine, prilocaine, procaine, propipocaine and tetracaine) based on a systematic approach using experimental design methodology in which one or more factors are changed at the same time. The strategy employs a chromatography modeling software for the simultaneous optimization of critical chromatographic parameters, which are gradient time tG, temperature T and the ternary composition of the organic eluent B.

DryLab is one of the most established software for chromatography modeling, which allows for modeling of chromatographic separations based on input data from two or more experimental runs. The use of DryLab for HPLC modeling to facilitate methods development was well documented in the last 27 years. In this time a continuous development occurred to the software which enabled it to cope more with the ongoing technological progress. On the other hand, a number of published studies exist that deal with the use of DryLab in different chromatographic modes and wide application ranges. DryLab is applied to solve different analytical problems in pharmaceutical analysis, which deal mostly with the separation of active pharmaceutical ingredients (APIs) in the presence of their impurities and/or their degradation products. In the field of phytochemical analysis many applications on complex plant extracts are also available. Moreover, DryLab has been successfully applied to optimize the separation of different groups of environmental pollutants, peptides and proteins and metabolites.

Highlights:

• Implementation of organic solvent gradients in micellar liquid chromatography, MLC.
• Screening of β-blockers in urine samples with direct injection in gradient MLC.
• 1-Propanol gradients allows the elution of β-blockers of diverse polarity.
• Gradient elution starting with pure micellar solution benefits direct injection.
• Optimisation of organic solvent gradients in MLC can be performed with DryLab®.

Quality by design (QbD) is an approach to product development where a comprehensive understanding of the effect of various inputs (e.g. process parameters, materials) on the final product (active pharmaceutical ingredient or drug product), leads to a process or product design that ensures reliable manufacture of a high-quality product. Analogous to QbD for product, QbD may also be applied to analytical methods, by defining the required analytical performance and systematically relating how the technique and method parameters relate to analytical performance. Achieving the appropriate level of method understanding typically involves a multifactorial approach. The factors to be studied are identified via a systematic risk analysis, which allows truly impactful parameters to be further investigated in studies applying statistical design of experiments (DOE) or mechanistic models to develop a multidimensional region of experimental space in which the effects of key factors are understood and documented. An operating region can then be defined where there is high confidence that the method will operate reliably. Data generated during use of the method can be monitored over time to ensure continued adequate performance of the analysis. 

Highlights:

• Test parameters of Tanaka and of Snyder showed surprisingly a high correlation.
• USP test is related to Tanaka and Snyder only in terms of hydrophobic characters.
• Some differences in the correlation are shown between aromatic and alkyl phases.
• The hydrophobic-subtraction model is extended to describe calixarene-bonded phases.

This paper presents new reversed phase liquid chro-matographic methods (HPLC-FLD and LC-MS/MS) for the quantification of sulfonamides in spiked and incurred honey samples. The sample preparation was optimized using Oasis HLB (hydrophilic–lipophilic balance) solid-phase extraction (SPE) cartridge. Elution of sulfonamides was carried out under acidic, neutral, and basic conditions using methanol. The sample clean-up was also tested using Strata-XL cartridges. The HPLC-FLD separation was performed using a Varian C18 column and a ternary (methanol-acetonitrile-phosphate buffer, pH 5) mobile phase resulting good selectivity for the determination. The robustness of the ternary gradient method was evaluated by computer simulation with DryLab4. LC-MS/MS separation was carried out on a Kinetex XB core-shell type HPLC column that enabled a low limit of detection (0.01–0.5 µg/kg) and faster separation (6 min). The developed methods were validated in accordance with the European Union Commission Decision 2002/657/EC and were applied successfully for more than four hundred honey samples under a national monitoring program.