54 TESTING
Figure 5: Gas chromatography equipment
Chromatography allows separation of all components present and ensures that any peak quantification that is carried out is specific only to the material(s) of interest. Once separation of the material of interest has been achieved, how its concentration is quantified again critically depends upon its inherent properties. Thermal conductivity detectors (TCD) or flame ionisation detectors (FID) are most commonly used with gas chromatography systems, while ultraviolet (UV), fluorescence, or refractive index (RI) detectors are popular detectors used with liquid chromatography systems. Mass spectrometry-based detectors provide the highest level of sensitivity and can be used with both gas and liquid chromatography systems. For our product development challenge,
we were looking to quantify the extent of permeation of both actives across the skin- mimic membrane. One of the compounds was well known and previously well-characterised so a robust analytical method for quantifying its presence in the receiving fluid had already been established and published in the pharmacopoeias (USP, EP, BP). The other compound however was more
novel and analytical methodology for its quantification needed to be developed. This can be a technically difficult challenge and there are a number of aspects to consider including, as discussed above, the choice of chromatographic technique and associated parameters, the detector type, whether the method is to be fully quantitative or just semi-quantitative, whether it needs to be validated, whether the method is to be used for development work or to support a regulatory submission, and so on. The standardised guidelines published by
the International Council for Harmonisation (ICH) provide best practice approaches in many areas related to drug product development. ICH Q2 sets out the steps internationally recognised as being necessary for the development and validation of analytical procedures.3
PERSONAL CARE November 2023
TABLE 1: ICH RECOMMENDED STORAGE CONDITIONS FOR DIFFERENT CLIMATE ZONES, RH = RELATIVE HUMIDITY
Climatic Zone I
II III
IVa IVb
Type of climate Temperate
Mediterranean/subtropical Hot,dry
Hot humid/tropical Hot/higher humidity
Formulation stability assessment Another important aspect to consider while developing novel personal care formulations is to what extent will they be impacted by local environmental conditions. Often, laboratories environments where prototype formulations are developed and tested have tightly controlled temperatures and humidities that do not accurately reflect typical transportation and storage conditions or the environment in the markets where the product is most likely to be sold. To provide confidence that the newly
developed formulations were going to be robust enough to withstand varying ranges of environmental conditions, accelerated stability of the lead prototype formulations was carried out by stress-testing them at 50°C. Following this harsh environmental
exposure, the same suite of product characterisation methods was repeated (i.e. rheology, pH, organoleptic assessment) and the impact of the product properties evaluated and compared with the product performance under standard conditions. Those formulations that maintained acceptable physicochemical characteristics following these stress tests were then recommended for further development and optimisation. As part of longer-term product development
programmes, the stability of new formulations is assessed under standard environmental conditions that reflect the different global climate zones. Guidelines for this assessment are again set out by the ICH (ICH Q1A).4
Long-term stability conditions 21C/45% RH 25C/60% RH 30C/35% RH 30C/65% RH 30C/75% RH
Conclusion In summary, a combination of theoretical formulation design, prototype preparation and appropriate critical quality attribute testing was used to develop different product prototypes incorporating a novel active ingredient combination. By establishing suitable key formulations
to develop successful product formats, Lucideon was able to provide our partner with working formulations that they could take directly into more advanced consumer product testing trials and full manufacturing feasibility assessment.
References 1. Hansen Solubility Partners, https://hansen-
solubility.com/
2. Sanchez-Lengeling B et al. A Bayesian Approach to Predict Solubility Parameters. Theoretical and Computational Chemistry. 30 April 2018, Version 1.
https://chemrxiv.org/ engage/chemrxiv/article-details/60c73e549 abda2ad40f8b857
3. European Medicines Agency. ICH Q2(R2) Validation of analytical procedures - Scientific guideline.
https://www.ema.europa. eu/en/ich-q2r2-validation-analytical- procedures-scientific-guideline
4. European Medicines Agency. ICH Q1A (R2) Stability testing of new drug substances and drug products - Scientific guideline.
https://www.ema.europa.eu/en/ich-q1a- r2-stability-testing-new-drug-substances- drug-products-scientific-guideline
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