Meta-Analysis and Analytical Methods in Cosmetics Formulation: Comparison
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The ever-evolving cosmetic industry requires advanced analytical techniques to explore, understand, and optimize product performance at nano, micro, and macroscopic levels. Nowadays, these insights are crucial for translating microstructure behavior into macroscopic properties. This knowledge is essential to formulate products with a lower carbon footprint and a higher sustainability profile, incorporating, at the same time, natural or biobased raw materials.

  • cosmetics
  • formulation
  • chromatography
  • olfactometry
  • stability
  • rheology

1. Introduction

The Perfume, Cosmetic, and Toiletry (PCT) industry dates back to the use of cosmetics by ancient civilizations, with the Egyptians, Greeks, and Romans being one of the first societies to extensively employ cosmetics for both aesthetic and functional purposes [1,2,3][1][2][3]. Neanderthal men utilized natural pigments for face painting, while the Romans employed oil-based perfumes. The Egyptians, around 4000 BC, were known for their extensive use of cosmetics for both aesthetic and functional purposes, with examples such as the lead-based kohl which was later used by Cleopatra. Then, significant milestones were attained in France during the Renaissance period, where perfumeries began crafting intricate formulations, and evolved with the 19th century seeing a transition to chemical ingredients [4]. The 20th century marked a period of rapid growth and technological innovations with the birth of iconic companies like Estée Lauder, L’Oréal, and Shiseido, who became pioneers in cosmetics R&D and marketing. Noteworthy is the industry’s adaptability and growth, even amidst global challenges such as the COVID-19 pandemic [5].

1.1. Industry Overview

In 2023, the global beauty market was valued at ca. USD 625.7 billion, with a projected CAGR (compound annual growth rate) of 3.3% from 2023 to 2028 [6]. When referring to the cosmetic industry, the latter is often misinterpreted as solely comprising the color cosmetic or makeup segments, while, in reality, these account for just over 18% of the entire personal care market. The industry itself is diverse, with various segments including skincare, haircare, fragrances, and more. The U.S. remains a significant market, but a noticeable shift towards developing regions like South America, Eastern Europe, and Asia has been observed and is projected to reach a value of USD 126.52 billion by 2025, growing at a CAGR of 9.3% from 2020 to 2025 [6]. Moreover, sustainability trends in 2023 have emphasized the use of biobased raw materials, eco-friendly packaging, and ingredient transparency, reflecting the industry’s response to consumer demands for sustainability [7,8][7][8]. The Cosmetic, Toiletry, and Fragrance Association (CTFA) and Cosmetic Ingredient Review (CIR) are among the organizations ensuring the scientific, legal, and regulatory adherence of cosmetic firms, promoting a culture of safety and transparency. As of 2022, the top 10 cosmetic companies held a market share of 62.8% of the global cosmetics market, reflecting a high concentration level within the industry [6]. Evolving consumer preferences, growing awareness related to the sustainability megatrend, and the rise of e-commerce are among the factors driving the growth of the PCT industry [7]. These industry leaders have maintained growth by employing strategies like product innovation, core brand re-marketing, and geographical expansion, particularly in high-growth regions like Asia, Latin America, and Eastern Europe.

1.2. The Importance of Instrumental Techniques in Cosmetics R&D

The development of instrumental methods marked a transformational shift in the cosmetics domain. Techniques such as high-performance liquid chromatography (HPLC) and gas chromatography–mass spectrometry (GC-MS) emerged as crucial tools for both quality control and gaining valuable insights into formulations. They enabled a thorough exploration of molecular composition, which allows for an understanding of interactions at a microscopic level, elucidating macroscopic properties such as viscosity, rheology, and solubility, which are pivotal to product performance [2,9,10][2][9][10].
Macroscopic properties constitute a spectrum of characteristics crucial for the practical application and performance of cosmetic products. These properties are significantly influenced by molecular and microscopic interactions, formulation strategies, and material choices [11]. These properties allow to gain insights into the texture, hydration potential, Sun Protection Factor (SPF), and longevity of cosmetics, to name a few [12].
The 20th century has witnessed remarkable advancements in the cosmetics industry. State-of-the-art analytical methods, the incorporation of novel active ingredients, and complex formulation strategies have all contributed to the rise of high-performance cosmetics [5,10][5][10]. Purity assessment assumed a central role with the inclusion of active molecules aimed at enhancing organoleptic properties like the fragrance and texture of cosmetics [9,13][9][13]. A significant paradigm shift observed in recent times is the transition from petrochemical-derived ingredients to biobased and naturally sourced alternatives. This transition is related to the sustainability megatrend and the demand for cleaner, safer, and better-performing formulations [11,14][11][14].
One case study highlighting the importance of analytical techniques in cosmetics is demonstrated by the detailed analysis of parabens, a common preservative in over 22,000 products, initially claimed as having low toxicity and general non-mutagenicity [15]. Advanced analytical methods enabled the understanding biological interactions of parabens, particularly their reproductive and estrogenic effects, leading to a trend in which parabens are being substituted by other less harmful compounds.

1.3. Meta-Analysis of Cosmetics

Several papers and reviews highlight the evolution and application of analytical techniques in cosmetics, correlating microstructure to macroscopic properties. The topics of these works range from the formulation development of emulsions [16] to modern techniques for sample preparation in cosmetics analysis [17], surface science in cosmetic formulations and its impact on product performance [11]. Moreover, new ingredients are being explored, and their microscopic properties and translation into macroscopic performance are being studied [18,19][18][19]. Nevertheless, there is a gap in the literature related to the application of a comprehensive analytical framework in cosmetics characterization, a so-called meta-analysis. A meta-analysis of cosmetics refers to a comprehensive and integrative approach that synthesizes findings from diverse analytical methodologies to provide a holistic understanding of cosmetic products. The meta-analysis of cosmetics involves the steps summarized in Table 1.
Table 1.
Stages in the meta-analysis of cosmetics formulation.
Stage Description
Limitations Comparison with Other Techniques Recent Developments
Systematic Review Begins with a thorough literature review to identify relevant studies using various analytical methods, aiming to cover a broad spectrum of research related to cosmetic analysis.
Comprehensive Data Collection Involves gathering data from different analytical techniques specific to a cosmetic product, such as chromatography for chemical composition, rheology for texture and consistency, electronic nose for fragrance, and stability testing for shelf-life.
LC-MS/MS High specificity, sensitive in complex matrices High cost, expertise needed More sensitive than HPLC Advancements in detection limits and sample preparation techniques
HPLC Versatile, widely available Less sensitive than LC-MS/MS More accessible than LC-MS/MS Improvements in column technology for better separation
Data Integration and Synthesis Integrates the collected data, which can be challenging due to their diversity. This step often includes standardizing different data forms for a comparative analysis.
GC-MS Excellent for volatile compounds Not suitable for high molecular weight compounds Statistical Analysis and Modeling Utilizes advanced statistical techniques and models to analyze the combined data set. This may include meta-regression analyses to understand variable relationships and their impact on a cosmetic product’s overall performance and quality.
Holistic Interpretation Aims to provide a comprehensive understanding of a cosmetic product by interpreting the integrated data in terms of chemical composition, physical properties, sensory attributes, stability, and how these collectively define the product’s characteristics.
Application in Product Development and Quality Control Applies the insights from the meta-analysis to guide product formulation, development, and quality control, ensuring informed decisions which consider various factors affecting the product’s efficacy, safety, and consumer acceptance.

2. Analytical Methods in Cosmetics

In the field of cosmetic analysis, several analytical techniques play a crucial role, each tailored to meet specific requirements to understand the molecular nature of cosmetic products and the complexity of their formulations. Herein, the primary emphasis is on specific techniques for conducting meta-analyses of cosmetic matrices. These techniques can be broadly classified into five main categories: chromatographic methods, spectroscopic methods, interfacial methods, rheology, and other specialized techniques. Chromatographic methods, such as LC-MS/MS (liquid chromatography–mass spectrometry/mass spectrometry) and GC-MS (gas chromatography–mass spectrometry), offer the remarkable capability to separate and identify complex mixtures within cosmetic formulations. Additionally, electronic nose technology has gained prominence in scent analysis, allowing for the characterization of fragrance components. Interfacial techniques encompass critical measurements such as surface and interfacial tension. Furthermore, the determination of emulsion stability, which can be assessed through analytical ultracentrifugation, provides valuable insights into the lifetime of emulsions. Rheology, the study of flow and deformation properties, also plays a crucial role in understanding the structural behavior of cosmetic products. Spectroscopic methods, including colorimetry, offer rapid and non-invasive means of analysis, primarily employed for color measurement within cosmetic formulations. These techniques collectively provide a comprehensive toolkit for meta-analysis in cosmetics. They facilitate a profound understanding of the molecular composition and microstructure of cosmetic products and help elucidate their impact on macroscopic properties. This holistic approach to cosmetic analysis is essential for ensuring product quality and performance. In Table 2, a comprehensive comparison of the advantages, limitations, and recent developments of chromatographic and spectroscopic methods is presented. The advancements in cosmetic measurement techniques are not only technical but also align with the broader objectives of efficiency, environmental sustainability, and adaptability.
Table 2.
Advantages, limitations, and comparison between techniques and recent developments in analytical methods for cosmetics.
Type of Technique Advantages
Superior for volatiles compared to HPLC and LC-MS/MS
Enhanced sensitivity and faster analysis times
Electronic Nose Rapid, suitable for complex aromas Limited by sensor types, less specific Faster, more holistic for aroma analysis Improved sensor technology for better specificity
Colorimetry Simple, quick for color analysis Limited to surface color, can be subjective Objective analysis of color compared to other techniques Integration with digital imaging for enhanced accuracy
Rheology Crucial for texture and viscosity assessment Can be complex and equipment-dependent Provides more detailed analysis than simple viscosity measurements Advances in automation and precision of measurements
Surface Tension Important for understanding foamability and surfactant micellization performance Limited to specific types of analysis More detailed than simple foam stability tests Innovations in measurement techniques for faster and more accurate results
To provide a comparative understanding of these techniques, the researchers introduce a radar chart with a scale from 1 to 5 in Figure 1, including aspects such as cost, specificity, ease of use, precision, environmental impact, and equipment requirements. Each technique is assigned a qualitative score for each category, reflecting its strengths and limitations. For example, LC-MS/MS may score highly in specificity and sensitivity but lower in cost and ease of use. In contrast, HPLC might score higher in ease of use and accessibility. This enables the emphasis on the practical implications and applicability of each technique in diverse scenarios.
Cosmetics 11 00001 g003
Figure 1. Radar charts of advantages (left), and limitations (right) of analytical techniques in cosmetics. A scale from 1 to 5 in aspects such as cost, specificity, ease of use, precision, environmental impact, and equipment requirements is used. The analysis was performed alongside the analysis of 257 publications and involved assigning a semi-empirical value to each category.

References

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