Developing highperformance antiperspirant actives

 There are two widely used antiperspirant actives; one contains only aluminum basic salts, such as aluminum chlorohydrate (ACH), activated ACH (AACH), aluminum sesqui chlorohydrate (ASCH) and aluminum dichlorohydrate (ADCH); and the other one consists of basic aluminum-zirconium salts with or without glycine. AP actives containing zirconium are not allowed for aerosol and pump spray applications. Certain zirconium compounds can only be used with aluminum compounds. Depending on the form of AP actives, the salts can be formulated into aerosol, roll-on, gel, stick and so forth.

The chemistry of antiperspirant actives occurs under highly concentrated aqueous solution conditions. There are many potential arrangements for a given molecular weight of AP salt and the exact nature of the most effective AP active is not known. Size exclusion chromatography (SEC) which is operated by high performance liquid chromatograph (HPLC) is widely used in the AP industry for the analysis of molecular size distribution. 27Al NMR is employed to characterise the structure of aluminum polymers. Separation and characterisation of Al species is well developed.

Identification of Zr species is less well developed due to the fact that Zr species interact and are absorbed on most of the SEC columns; lower Molecular Weight (MW) Zr species and higher MW Al species co-elute under most conditions; and Al has much greater sensitivity with IR detection than Zr. Zirconium, however has greater sensitivity with Ion-Coupled Plasma (ICP). SEC-HPLC-ICP technology has been developed to study the zirconium chemistry and create the high performance Al-Zr AP actives.