Antonio Bettero

Stability of vitamin C derivatives in solution and topical formulations.

The stability of ascorbic acid, ascorbyl palmitate and magnesium ascorbyl phosphate (VC-PMG) in both standard solutions and topical formulations was investigated by direct RP-HPLC analysis after sample dilution with a suitable aqueous-organic solvent mixture. The results showed that, whereas the two vitamin C derivatives were more stable than ascorbic acid, the ascorbyl esters showed significant differences. Esterification with palmitic acid in 6 position did not prevent hydrolysis of the molecule, either in solution or in emulsion; only the special preparation of products with high viscoelastic properties was able to reduce the typical behaviour of this compound. Conversely, the introduction of the phosphoric group in 2 position protected the molecule from break-up of the enediol system, confirming VC-PMG as a very stable derivative of vitamin C that may be easily used in various types of cosmetic products.

High-performance liquid chromatographic determination of ionic compounds in cosmetic emulsions: application to magnesium ascorbyl phosphate

Abstract A rapid, reliable method based on reversed-phase high performance liquid chromatography for the qualitative and quantitative determination of magnesium ascorbyl phosphate (VC-PMG) in both standard solutions and cosmetic products is reported. The procedure, based on an aminic stationary phase and acetonitrile-0.3 M phosphate buffer (pH 4) (40:60) as the mobile phase, allows the determination of VC-PMG in cosmetic samples after dilution with a tetrahydrofuran-0.3 M phosphate buffer (pH 4) (3:7) solvent mixture.

Reversed-phase high-performance liquid chromatography applied to the direct analsis of untreated heterophasic systems

Abstract A simple and rapid approach for the direct analysis of multi-component heterophasic matrices is reported. The procedure is based on sample dilution with tetrahydrofuran—water (9:1) followed by direct reversed-phase high-performance liquid chromatography. The method is suitable for quality control and stability studies of drugs, food and cosmetic products.

Dehydroacetic acid sodium salt stability in cosmetic preservative mixtures

Dehydroacetic acid sodium salt Prevan (DHANa) stability in presence of other cosmetic preservatives as Bronopol, Germall 115 and Kathon CG was investigated through a HPLC method that permits simultaneous determination of binary and ternary mixtures of the above preservatives.

Stability of vitamin A palmitate in cosmetic emulsions: influence of physical parameters

The aim of this work was to verify if a close relationship exists between the physical stability of an emulsion and the chemical stability of vitamin A palmitate included in it. Oil‐in‐water cosmetic emulsions with high viscoelastic properties were prepared, and their rheological behaviour was investigated in oscillatory conditions. The stability of each sample was verified in high‐temperature stress conditions: periodical checks of physical parameters and chromatographic analysis of vitamin A were performed during storage. Results show that the chemical stability of vitamin A palmitate strictly depends on the physical stability of the formulation and in particular on the presence of a coherent gel‐like structure in the external phase of the emulsion.

A combined chemico-mineralogical and tensiometric approach for evaluation of Euganean Thermal Mud (ETM) quality

The tensiometric vs. skin approach (TVS modelling®) is a non-invasive method based on the permutability principle of tensiometry. TVS modelling® is a technologic model that can evaluate the reproducibility of the matrix of thermal mud, its degree of maturation and consequently its skin affinity, in a non-destructive way. This is an essential pre-condition for defining the objective scientific protocols. The surface energy profile of the matrixes is created by a Tenskinmeter®, a tensiometer modified by us for tensiometric measurements on skin. The development of a chemico-mineralogical index (I chmi) based on X-ray fluorescence analysis allows the typical chemico-mineralogical constituents of thermal muds to be determined. The combined TVS-I chmi approach developed here demonstrates the interconnections between the typical chemico-mineralogical components of a Euganean Thermal Mud (ETM) and its energy surface properties. The combined approach also demonstrates the interconnections at the interface between I chmi and the skin affinity of the mud matrix, revealing their typical functional and therapeutic effects.

Active packaging for topical cosmetic/drug products: a hot-melt extruded preservative delivery device.

A delivery device intended for the prolonged release of antimicrobial agents, able to enhance the stability profile of liquid/semi-solid cosmetic/pharmaceutical products for topical application, was proposed in the present study. With the aid of a simulation program based on compartment models, the relevant kinetic and formulation parameters were defined using dehydroacetic acid sodium salt (DHA.Na, Prevan) as the model preservative. Indeed, the overall DHA.Na degradation rate is increased in the presence of formaldehyde releasers that are often employed as co-preservatives. Inert matrices (3 g weight and 18 mm diameter) based on high-density polyethylene (HDPE), possibly consistent with the design of an active packaging meant for preservative delivery, were prepared by hot-melt extrusion. Units with satisfactory physical-technological properties could be obtained up to 50%w/w loads of antimicrobial agent. In an attempt to modify the relevant Fickian release profiles by varying the area exposed to the medium, matrix systems coated with an impermeable film except for one base (CMs) or for the inner surface of a central drilled hole (PCMs) were investigated. On the basis of the n exponent of power equation and the outcome of linear fitting, PCMs were proven able to yield the zero-order release behaviour needed to ensure constant DHA.Na levels over a predetermined time period, as indicated by the simulation process.

Chemico-physical and functional properties of inorganic sunscreens in cosmetic products

This paper reports preliminary results of a study carried out on liquid crystal emulsions added to three different inorganic sunscreens: ultrafine zinc oxide, ultrafine titanium dioxide (inorganic‐treated) and ultrafine titanium dioxide (organic‐treated hydrophobically).

A rapid HPLC technique for determining levels of histamine in tears from normal and inflamed human eyes

Because of the important role of histamine in the inflammatory process, the measurement of histamine levels in tears has been considered as a possible index of eye irritancy. Histamine levels have been measured using an HPLC procedure involving fluorimetric detection after fluorescamine derivatization. Analyses, at picomole levels, were carried out in less than 5 minutes using 10 microliter of tear samples collected from either normal or inflamed human eyes.

Rheological and spectroscopic behaviour of cosmetic products

ZusammenfassungEine aussichtsreiche Methode zur Auswertung des rheologischen und spektroskopischen Verhaltens von kosmetischen Produkten wird beschrieben. Das Verfahren beinhaltet einen automatischen viskosimetrischen Test durch Fließkurven und nachfolgende spektroskopische Analyse ohne Vorbehandlung der Probe. Als Beispiel wird die Schwefelbestimmung bei 0,5 ppm mit Hilfe der ICP-Methode im unteren UV-Bereich beschrieben.SummaryA promising approach for evaluating the rheological and spectroscopic behaviour of cosmetic products is described. The method involves an automatic viscometric test by flow curves detection and subsequent spectroscopic analysis without pretreatment steps of the cosmetic sample under investigation. Determination of sulphur content at 0.5 ppm using the ICP (Inductively Coupled Plasma) technique in a low UV region is reported as an example.