4.1 Natural and manufactured textiles fibers can be treated with chemicals to provide enhanced antimicrobial (fungi, bacteria, viruses) properties. In some cases, silver nanomaterials may be used to treat textile fibers (1).6 Silver nanomaterials are used to treat a wide array of consumer textile products, including but not limited to various clothing; primary garments (shirts, pants), outer wear (gloves, jackets), inner wear (socks and underwear), children's clothing (sleepwear); children's plush toys; bath towels and bedding (sheets, pillows); and medical devices (wound dressings) (2).

4.2 There are many different chemical and physical forms of silver that are used to treat textiles and an overview of this topic is provided in Appendix X1.

4.3 Several applicable techniques for detection and characterization of silver are listed and described in Appendix X2 so that users of this guide may understand the suitability of a particular technique for their specific textile and silver measurement need.

4.4 There are many different reasons to assay for silver nanomaterials in a textile at any point in a product's life cycle. For example, a producer may want to verify that a textile meets their internal quality control specifications or a regulator may want to understand the properties of silver nanomaterials used to make a consumer textile product under their jurisdiction or what quantity of silver nanomaterial is potentially available for release from the treated textile during a washing process. Regardless of the specific reason, a structured approach to detect and characterize silver nanomaterials present in a textile will facilitate measurements and data comparison.

4.5 The approach presented in this guide (see Fig. 1) consists of three sequential tiers: obtain a textile sample (Section 7), detection of a silver nanomaterial (Section 8), and characterization of a silver nanomaterial (Section 9). If no forms of silver are detected in a textile sample using appropriate (fit for purpose) analytical techniques then testing can be terminated. If silver is detected but present in a non-nanoscale form, the textile can be treated as a bulk material; however, there still may be potential for release of silver ions that transform into nanoscale silver-containing particles. If silver is detected in nanoscale form it can be concluded that it is a silver nanomaterial in the textile sample and subsequent measurements can be made to characterize its chemical and physical properties.

4.6 Numerous techniques are available for the detection and characterization of silver nanomaterials in textiles which can cause confusion for those interested in developing an analytical strategy and selecting appropriate techniques. Some techniques are applicable only to certain chemical forms of silver and all have limited ranges of applicability with respect to a measurand. No single technique is suitable to both detect and fully characterize silver nanomaterials in textiles. As such, this guide is an attempt to describe and define a tiered approach that uses commercially available measurement techniques so that manufacturers, producers, analysts, policymakers, regulators, and others may make informed and appropriate choices in assaying silver nanomaterials in textiles within a standardized framework. The user is cautioned that this guide does not purport to address all conceivable textile analysis scenarios and may not be appropriate for all situations. In these instances, professional judgment is necessary.

4.7 This guide is intended to provide a tiered approach to be used to determine an efficacious and efficient procedure for detecting and characterizing silver in textiles to make a determination as to whether any silver nanomaterial is present. This tiered approach may also be used to determine whether a reported measurand for silver nanomaterials in a textile was obtained in an appropriate and meaningful way.

4.8 Measurement of many material properties is method dependent. As such, caution is required when comparing data for the same measurand from instruments that operate on different physical or chemical principles or with different measurement ranges.

4.9 The amount of silver in a textile has a tendency to decrease over time as silver metal and silver compounds can react with oxygen and other oxidation-reduction (redox) active agents present in the environment to form soluble ionic species. These ions are released by contact with moisture (for example, from ambient humidity, washing, body sweat, rain, or other sources). As described in Appendix X1, release of ionic silver species may occur at varying rates that depend on many characteristics, including chemical nature, surface area, crystallinity, and shape of the silver source as well as where the silver is applied to the textile (on the fiber surface, in the volume of the fiber, and so forth) and in what form the silver is applied to the textile (discrete particles, with carriers, and so forth). Hence, if silver is detected in a textile and its properties characterized, the result may only be indicative of that moment in the article's life cycle and great care is necessary in drawing temporal inferences from the results.

4.10 Textile acquisition, storage, handling, and preparation can also affect reported results.