High alkalinity Na2CO3 treated filter paper as a substrate for viral inactivation in Face Masks.

N.A. Bouchard, H. Lovenstein

Abstract:

The range of protections offered by varied face and mouth coverings is inconsistent and heavily tied to the type and use of covering by the wearer (2, 3, 4, 5, 6). Such protective measures in terms of public health are therefore regarded ineffective in containing the current COVID-19 pandemic (7).

Charging a filter paper with an alkaline salt (Na2CO3) solution, air drying the treated filter paper, thus becoming virucidal upon aerosol absorption by the filter paper has therefore been proposed to create a potential active layer to existing face coverings. This principle can also be implemented as surface coatings for application in but not limited to face coverings.

Store bought Na2CO3 was prepared in solutions ranging from 3.75g/l - 15g/l, with the objective to identify the lowest possible concentration of solution yielding a pH>12, as is known to inactivate SARS-CoV (1). These preliminary tests established that a low concentration of washing soda (>12.5g/l) treated filter paper, a pH change from control (pH 6-7) to >12 is obtainable in microdroplets and aerosols post-exposure to treated filter paper. It is therefore inferred that the virucidal effect of Na2CO3 treated filter paper should be further studied in more controlled environments in conjunction with SARS-CoV-2.

Introduction:

With the current SARS-CoV-2 pandemic, there is a fundamental and growing concern with the protections offered by mouth coverings. Where use of mouth coverings is well known to substantially decrease transmission rates (12), the safety and efficacy of masks is known to be tied to material choices (2, 4, 5, 6). Electromagnetically charged masks (N95, N99), synthetic materials such as in surgical coverings, and over all maintenance of cloth or other DIY coverings and post exposure treatments are the known variables to mask efficacy (2, 3, 5, 6, 7, 8). However, there has yet to be an inclusion of an activated ingredient which is known to inactivate viral particles on contact with out causing harm to the wearer.

Here, we explore the use of high alkalinity conditions as a simple to use and low cost vehicle for surface inactivation of aerosolized viruses, as it is well established that a pH>12 inactivates the SARS-CoV virus (1, 12, 13).

Utilizing store bought materials, we explore the potential gradients at which Na2CO3 treated coffee filter paper can provide the known conditions for SARS-CoV inactivation (1), with the hopes that these conditions carry over to SARS-CoV-2/COVID-19 as well.

Materials and Methods:

Coffee filter no. 4 squares were cut out (approx. 3cm x 3cm) and treated with solutions of Na2CO3 at given concentrations of 3.75g/l, 5g/l, 7.5g/l, 10g/l,12.5g/l, and 15g/l.

Solutions were made by adding pre-weighed amounts of Na2CO3 (Tricel Washing Soda) to 200ml of boiling tap water, then heated continuously for approximately 5 minutes on high heat until salts had dissolved into a solution. Solutions were then decanted into clean glassware, tested for pH, and used for filter paper prep.

Coffee filter paper was then completely submerged for 2 minutes, before hanging on a drying rack for 1 hour. For each solution, 4 squares were treated, for a total of 28 treated filter papers including positive controls.

Each experiment was designed to simulate respiratory aerosols in given volumes that could be detectable with colometric litmus paper to visually detect a change in pH on contact with the treated filter paper in contrast with a positive and negative control (filter paper treated at ~500g/l Na2CO3 and non treated filter paper, respectively). The first experiment involved suspending filter paper above a large pan of boiling water for 2 minutes and 30 seconds, suspended by press paper clips from a wooden skewer, with the lid on top of the pot. Filter papers were then removed and transferred to a glass surface, where pH paper was administered and pressed firmly with the back of a large knife. Each test tested a given concentration, as well as a positive and negative control. Water boiled was tested at pH 6-7.

In the second tests, the methods of the previous experiment of using a fine mist from a water 'spritzer' bottle was applied. Held by a press paper clip, each tested filter paper was spritzed 2 times with paper tested a pH 6-7, quickly transferred to a glass surface, and litmus paper was pressed firmly to the affected surface.

After each pressing of each test, images were taken of the filter paper, associated litmus test, as well as the colometric pH indication guide on the litmus paper. Images of the experiments are to be found in the appendices

Results:

Observed pH changes on contact with treated filter paper: