ISO 18061: 2014. Fine ceramics (advanced ceramics, advanced technical ceramics) - Determination of antiviral activity of semiconducting photocatalytic materials-Test method using bacteriophague Q-beta.

Test accredited by ENAC (Spanish National Accreditation Entity).

The ISO 18061: 2014 standard establishes a test method to determine the antiviral activity of products with integrated photocatalytic materials or that contain surface photocatalytic films, by quantifying the reduction in the infectivity of the bacteriophage Q-beta after irradiation with ultraviolet light. This test is intended for the analysis of semiconductor photocatalytic materials used in construction materials, in the form of a flat sheet, board, or plate, excluding analysis of porous, granular, or porous photocatalytic materials, and fabrics or textiles.

In the test described by ISO 18061, the bacteriophage Q-beta is used as the surrogate virus for Influenza viruses. The test sample with the photocatalytic material is inoculated with a suspension of bacteriophage Q-beta of known titer and exposed to ultraviolet radiation of known intensity (0.001 mW / cm2 - 0.25 mW / cm2) for a specific period of time (2 to 8 hours). After irradiation, the existing bacteriophage titer in the pieces is determined by counting plaque forming units (UFP). For this, the bacteriophage is recovered by washing the pieces and the resulting washing solutions are mixed with suspensions of Escherichia coli bacteria sensitive to bacteriophage Q-beta. The mixtures of the test solutions and the receptor bacteria are plated on agar plates and incubated to obtain the counts of the plaque forming units. The bacteriophage (UFP) titer obtained from the irradiated photocatalytic antiviral material parts is compared with that obtained from control samples (not treated with photocatalytic material), and with samples treated and untreated with photocatalytic material maintained in darkness over the same period of time, and the value of the photocatalytic antiviral activity with UV irradiation (ΔV) is calculated. The ISO 18061: 2014 standard does not establish any reduction criteria to affirm that a product does or does not have photocatalytic antiviral activity, but only allows assigning a value of antiviral activity or reduction when comparing the bacteriophage titers in the samples with the photocatalytic material test after irradiation, with those of the untreated irradiated samples and the non-irradiated samples, both treated and untreated. In case the test sample includes non-photocatalytic antiviral materials, the value of non-photocatalytic antiviral activity (VD) can also be calculated.

Square pieces of the test product 50 ± 2 mm x 50 ± 2 mm, and the thickness of which should not exceed 10 mm, are used for this test. Both, pieces treated with the photocatalytic material and control pieces with the same characteristics but without the photocatalytic treatment, are used. The number of test pieces is 15 per test (9 pieces untreated and 6 pieces treated with the photocatalytic material). The pieces are destined in the following groups: 3 units without photocatalytic material to quantify the titer as the inoculum control; 3 units with photocatalytic material and another 3 units without photocatalytic material to keep in the same test chamber without exposure to ultraviolet light; and 3 units with photocatalytic material and another 3 units without photocatalytic material to keep in the same test chamber with ultraviolet light irradiation. However, it is always recommended to send twice the number of pieces needed (30 pieces: 18 without photocatalytic treatment and 12 with photocatalytic treatment).

The customer must specify the circumstances under which the test product is intended to be used, in order to irradiate the photocatalytic material with one intensity or another of ultraviolet radiation. For example, an intensity of 0.25 mW/cm2 is suitable for irradiation of a product located by the window during the day; a UV intensity of 0.10 mW/cm2 simulates the UV irradiation of a material located inside the room (about 1.5 m away from the window) during the day, or next to the window in the early morning or before sunset; an intensity of 0.01 mW/cm2 is appropriate for materials located in a room about 3 meters from the window during the day; and an intensity of 0.001 mW/cm2 simulates the UV irradiation of a material used in a room without a window or in a room at night (only with interior light). The customer must also indicate the required UV irradiation time. The time of exposure to ultraviolet light recommended by the standard is 4 hours, but it is allowed to adapt the test time between 2 and 8 hours to adapt the test to the real use of the product to be analyzed.