Smartphone TLC Detects Tizanidine Residue

When medicines accidentally mix with traces of other drugs during manufacturing, it can seriously endanger patients, which makes treatments less effective, causing side effects, or even leading to addiction. Some drugs are especially risky in this regard, such as tizanidine (TZN), because even small amounts matter a lot and it has potential for misuse. If tiny leftover traces of it end up in other medications, it could cause harmful reactions, withdrawal symptoms, or unintentional dependency in patients. Manufacturers already take steps to clean their equipment thoroughly to prevent this, but there is still a need for fast, dependable ways to regularly check that everything is truly clean.

To tackle this problem, researchers at Pharos University and Cairo University in Egypt built a portable testing kit that can be used right on-site to check for tizanidine, along with three other common drugs — aceclofenac (ACF), ibuprofen (IBF), and paracetamol (PRC). The method works by wiping down surfaces with a swab (the same approach recommended by the FDA), then using thin layer chromatography (TLC, basically a way of separating out different substances) combined with a smartphone camera and some photo-analysis apps to read the results. A paper based on their work was published in the journal Scientific Reports.¹

What is Cross-Contamination in Pharmaceutical Manufacturing, and Why Is It Dangerous?

Cross-contamination refers to the accidental transfer of residues from one product to the subsequent batches of another during the manufacturing process.² This kind of mix-up is a real risk in factories that make several different medicines using shared equipment, and it can seriously endanger patients. Even tiny leftover traces of one drug getting into another can make treatments less effective. It can also cause unwanted side effects or even toxic reactions, especially with drugs where the difference between a safe dose and a harmful one is very small. Also, if the leftover traces come from drugs that carry a risk of misuse, patients could end up unintentionally becoming dependent on them.³TZN is a commonly used muscle relaxant, but if traces of it accidentally end up in other medications, it can cause harmful effects. In addition, TZN carries some risk of misuse.⁴

Why Use a Smartphone Combined with TLC for Cleaning Validation?

Testing methods that use a regular smartphone are quickly becoming a popular alternative to traditional laboratory equipment. They work just as well, but they are also portable, easy to use, affordable, and better for the environment, which fits perfectly with where modern testing methods are heading.⁵ Despite this, smartphone-based testing has not been used often for cleaning validation, which is why combining smartphones with TLC looks like such a promising idea, as it may lead to a dependable, portable tool that works right on-site. TLC works a bit like taking a fingerprint of each substance, making it especially useful for analyzing products with multiple ingredients, since it quickly shows what's present in each one.⁶With asmartphone-based approach, the phone's camera is used to snap a photo of the TLC plate after it has been treated so the results become visible, either under UV light or with a staining solution. Then, special software analyzes that photo using different color models, turning the colors in the image into precise numerical values. ^7,8

What Did the Researchers Achieve with Their New Tool, and How Good Is It?

The research teams state that their new tool offers a quick, easy, and environmentally friendly way to check on-site whether equipment has been properly cleaned. It can both measure exact amounts of drug residue and give a fast visual check using color charts, which is something no previous method has managed to do together. The researchers fine-tuned the mix of chemicals used to separate the drugs (a blend of toluene, acetone, and ethanol) as well as the settings for the smartphone-based analysis. When tested against standard international guidelines, the method proved accurate and sensitive enough to detect even very small amounts of the drugs, well below the levels considered safe. The team also confirmed that the method is genuinely eco-friendly and sustainable using several established scoring tools, making it a promising new option for reliably checking that manufacturing equipment is free of harmful drug residue.¹

^“Overall,” write the authors of the paper,¹ “the developed portable at-line analyzer represents a highly practical tool for routine cleaning validation of high-risk drugs.”

References

1. Abd El-Aziz, M. O.; Nadim, A. H.; Monir, H. H. et al. Sustainable Miniaturized Smartphone-Coupled TLC Platform for Innovative Cleaning Validation: Application to Tizanidine Combinations Under Challenging Concentration Ratios. Sci Rep. 2026, 16 (1), 22559. DOI: 10.1038/s41598-026-62219-6
2. Slivová, Z.; Opatlilová, R. Determination of Anthracycline Drug Residual in Cleaning Validation Swabs of Stainless-Steel Equipment After Production of Cytostatic Injections Using HPLC Analytical Method. J. Spectrosc. 2015 (4), 847349. DOI: 10.1155/2015/847349
3. Uriguen, A. F.; Telleria, I. B.; Arrechea, S. M. et al. Determination of the Cross-Contamination and Validation of the Cleaning Process for an Automated Personalised Dosing System. Eur. J. Hosp. Pharm. 2022, 29 (3), 7. DOI: 10.1136/ejhpharm-2020-002301
4. Kitta, A.; Wippel, A.; Richwein, P. et al. Using Clonidine in the Treatment of Tizanidine Abuse and Withdrawal: A Case Report of a Patient with Somatoform Pain Disorder. J. Subst. Use 2020, 25 (5), 3. DOI: 10.1080/14659891.2020.1738574
5. Abd-ElSalam, H-A.; Elzanfaly, E.; Bassuoni, Y. F. Smartphones as Optical Detectors in Pharmaceutical Analysis: A Review. Microchem. J. 2025, 212, DOI: 10.1016/j.microc.2025.113316
6. Jain, B.; Jain, R.; Jaiswal, P. K. et al. A Non-Instrumental Green Analytical Method Based on Surfactant-Assisted Dispersive Liquid-Liquid Microextraction-Thin-Layer Chromatography-Smartphone-Based Digital Image Colorimetry (SA-DLLME-TLC-SDIC) for Determining Favipiravir in Biological Samples. Molecules 2023, 28 (2), 529. DOI: 10.3390/molecules28020529
7. Yu, H.; Le, H. M.; Kaale, E. A. et al. Characterization of Drug Authenticity Using Thin-Layer Chromatography Imaging with a Mobile Phone. J. Pharm. Biomed. Anal. 2016, 125, 9. DOI: 10.1016/j.jpba.2016.03.018 (2016).
8. Moaaz, E.; Abdel-Moety, E. M.; Rezk, M. R. et al. Smartphone Based TLC Approach versus Conventional Densitometric Measurement for the Simultaneous Determination of Donepezil and Memantine, Content Uniformity Testing Along with Greenness and Whiteness Assessment. Sustain. Chem. Pharm. 2024, 42, 10. DOI: 10.1016/j.scp.2024.101789 (2024).