Ethanol concentrations of 60% to 95% (v/v) are deemed safe and effective for disinfection by the United States Food and Drug Administration (US FDA), CDC and the WHO (Boyce et al., 2009, CDC, 2019a, FDA, U.S., 2020, FDA, U.S., 1994), including for use against SARS-CoV-2. Interestingly, Edmonds et al. suggested that the antimicrobial activity of the ABHRs is highly dependent on the choice of formulation (i.e., excipient) rather than on the concentration of alcohol. They also suggested that the liquid, gel and foam-based products can all be equally effective if the ethanol content used was within the 60–95% standard range (Edmonds et al., 2012). However, increasing ethanolic concentrations of hand rubs from 80% to 85% (v/v) can reduce the contact time necessary to achieve an efficient bactericidal activity (Suchomel et al., 2012; Eggerstedt, 2013; Wilkinson et al., 2017). Despite this, the WHO, US FDA and CDC still maintain their recommendations of 60–95% ethanol content in ABHRs. …It is worth highlighting that ethanol, unlike water, has a density < 1 g/cm3, which means that percentages of ethanol in water by weight (w/w) and by volume (v/v) can be significantly different and must be specified on the label. A useful comparison between percentages by weight and by volume of ethanol in ABHRs is reported in a recently published document (BDC, 2020). Although this concept might seem trivial, there are cases of published works, where the concentration expression (either w/w or v/v) was not specified, as indicated by Kampf (Kampf, 2018), ultimately presenting ambiguous information. In research work, compounding and manufacturing, it is recommended to clearly specify the concentration units of alcohol used in ABHRs.
https://www.bode-science-center.com/center/hand-hygiene/hand-disinfection/detail-hand-disinfection/article/ethanol-concentration-table-what-is-the-percentage-by-volume-or-weight.html
According to the US FDA's Tentative Final Monograph (TFM) for health care antiseptics, isopropanol should be used as an antiseptic alcohol at concentrations between 70 and 91.3% (v/v) (FDA, 1994). This range of concentration has also been re-endorsed by the US FDA for the preparation of ABHR during the CoViD-19 health emergency (FDA, 2020).
