Why analytical swab selection matters — and how Texwipe’s TX718 is designed for HPLC-based applications

Low-Interference Swabbing for Solvent-Based Cleaning Validation

Why analytical swab selection matters — and how Texwipe’s TX718 is designed for HPLC-based applications

Cleaning validation is a critical element of pharmaceutical manufacturing. Before a new product or production batch is introduced, manufacturing equipment must be demonstrably clean so that residues from a previous process cannot contaminate the next batch. The source document explains that this requirement is embedded in current Good Manufacturing Practice expectations, including FDA requirements and comparable international guidance. Cleaning procedures therefore have to be developed, documented, verified and validated, with acceptance limits that are measurable, achievable and scientifically defensible.

From Cleaning Validation to Analytical Sampling

Proving that equipment is clean requires representative sampling as well as a suitable analytical method. Two principal sampling approaches are described: rinse sampling and direct surface sampling, or swabbing. Rinse sampling can cover large surfaces and areas that are difficult to access, but it may be less suitable for insoluble residues or localized problem areas. Swabbing, by contrast, allows targeted sampling of the areas considered most likely to retain contamination, including pits, holes and surfaces where residues may become baked on.

For direct surface sampling, the swab itself becomes part of the analytical system. Any material released from the swab can potentially appear in the analytical result and can therefore interfere with the determination of contaminants. Earlier swabs could contain adhesives used to attach the head to the handle. Texwipe states that its cleaning-validation swabs use thermal bonding instead, attaching the fabric directly to the polypropylene handle without adhesives.

Why HPLC Swab Background Matters

This article focuses on High Performance Liquid Chromatography (HPLC) as the analytical technique and on swabbing as the sample-collection method. Analytical procedures for cleaning validation need to demonstrate characteristics such as accuracy, precision, specificity, detection and quantitation limits, and linearity. According to the document, the swab can particularly influence detection limits, quantitation limits and linearity.

The effect on linearity can be illustrated by a simple example. If a swab contributes a fixed analytical interference, that contribution becomes increasingly significant as the concentration of the substance being measured decreases. A calibration response that should increase proportionally can therefore be distorted by a constant background signal. Reducing extractable substances from the swab is consequently important when analytical sensitivity is critical.

Designing TX718 Around Interference Reduction

The development of Texwipe’s Alpha® Polyester Knit TX718 began with a detailed examination of potential interference sources. The fabric, handle and manufacturing inputs were analyzed, including polyester polymer material, yarn and lubricants, cleaning-process ingredients, polypropylene and the handle colorant package. Some components showed measurable interference when analyzed in concentrated form.

The resulting design takes a deliberately minimalist approach. The knit pattern was changed to improve rinsing, and the yarn was changed to a low-titanium-dioxide version. The scouring process was optimized for the application. The handle colorant package, including titanium dioxide, was removed, giving the handle a more translucent appearance. The familiar notch remains so that the handle can be broken to a defined length for placement in a vial.

TX718: Performance, Application and Practical Considerations

Comparative Extractables Testing

The Texwipe TechNote No.6 from 2026 reports a comparative study of the TX715 and TX718 polyester swabs using methanol extraction followed by UV spectral analysis.

The reported spectra showed a lower overall absorption level for TX718 than for TX715. The lower background observed for TX718 is presented as an advantage for applications requiring higher analytical sensitivity, including pharmaceutical quality-control work and solvent-containing liquid chromatography testing.

Lower Titanium Dioxide Background

Titanium dioxide is another consideration addressed by the TX718 design. Both the fabric and handle were developed without intentionally added titanium dioxide. This can be advantageous for analytical applications in which titanium dioxide itself is a substance of interest or a potential source of background. The source emphasizes that TX718 is not intended to replace TX715 universally: where an existing TX715 method performs satisfactorily, continued use of TX715 is appropriate. TX718 is particularly positioned for new method development or situations in which interference from the existing swab presents a challenge.

Managing Extractables Before Analysis

The TechNote also stresses an important practical limitation: TX718 is not contamination-free. Extractable substances can remain in the materials, and diffusion can cause contaminants to migrate back toward the surface after processing. The document therefore describes solvent pre-processing as one possible way to further reduce extractable background before use.

What the TX718 Offers

TX718 was developed specifically for solvent-based surface sampling in cleaning-validation applications where low analytical background is important. Its low-titanium-dioxide polyester knit head, optimized processing, adhesive-free thermal bond and translucent, colorant-free polypropylene handle are intended to minimize potential sources of interference.  

For laboratories developing or troubleshooting HPLC methods, swab selection should therefore be considered part of the analytical method rather than merely a sampling accessory. A swab that contributes fewer extractables can help protect analytical sensitivity and improve confidence in low-level residue measurements. At the same time, the document makes clear that performance must be evaluated in the context of the specific method and contaminants of concern.

Conclusion

Effective cleaning validation depends on more than a validated cleaning procedure. The sampling strategy and analytical method must work together, and the sampling device must not introduce a background that compromises the measurement. The TX718 represents Texwipe’s approach to this challenge for solvent-based HPLC applications: identify potential interference sources throughout the swab, remove or reduce them through material and process changes, and verify the resulting background analytically. Where an existing TX715 method is already working well, the source recommends continuing to use it; where a new method is being developed or interference is limiting performance, TX718 is presented as an alternative designed for lower background and greater analytical sensitivity.

Source: Texwipe TECHNOTES No. 06, July 2026, TX718 — “Texwipe’s New Cleaning and Cleaning Validation Swab for Solvent-Based Analytical Systems.”