An Investigation into the Stability and Sterility of Citric Acid Solutions Used for Cough Reflex Testing
- 716 Downloads
Citric acid is used in cough reflex testing in clinical and research settings to assess reflexive cough in patients at risk of swallowing disorders. To address a lack of knowledge in this area, this study investigated the stability and sterility of citric acid solutions. Triplicate solutions of citric acid (0.8 M) in isotonic saline were stored at 4 ± 2 °C for up to 28 days and analysed by high-performance liquid chromatography. Microbiological sterility of freshly prepared samples and bulk samples previously used for 2 weeks within the hospital was determined using a pour plate technique. Microbial survival in citric acid was determined by inoculating Staphylococcus aureus, Escherichia coli, or Candida albicans into citric acid solution and monitoring the number of colony-forming units/mL over 40 min. Citric acid solutions remained stable at 4 °C for 28 days (98.4 ± 1.8 % remained). The freshly prepared and clinical samples tested were sterile. However, viability studies revealed that citric acid solution allows for the survival of C. albicans but not for S. aureus or E. coli. The microbial survival study showed that citric acid kills S. aureus and E. coli but has no marked effect on C. albicans after 40 min. Citric acid samples at 0.8 M remained stable over the 4-week testing period, with viable microbial cells absent from samples tested. However, C. albicans has the ability to survive in citric acid solution if inadvertently introduced in practice. For this reason, in clinical and research practice it is suggested to use single-use aliquots prepared aseptically which can be stored for up to 28 days at 4 °C.
KeywordsCitric acid Cough reflex testing Stability Sterility Tussigenic challenge Deglutition Deglutition disorders
Conflict of interest
The authors have no conflicts of interest to declare.
- 12.Wong AW, Datla A. Assay and stability testing. Separ Sci Technol. 2005;6:335–58.Google Scholar
- 13.Pharmaceutical Society of New Zealand. Pharmacy Practice Handbook. Wellington. Wellington: The Pharmaceutical Society of New Zealand; 2003.Google Scholar
- 15.Woods DJ. Extemporaneous formulations of oral liquids: a guide.dunedin. Dunedin: Healthcare Otago; 2012.Google Scholar
- 17.Food and Drug Administration. Guidance for Industry: Nasal Spray and Inhalation Solution, Suspension, and Spray Drug Products, Chemistry, Manufacturing, and Controls (CMC) Documentation. Available at http://www.fda.gov/cder/guidance/index.htm.
- 20.Violeta N, Trandafir I, Ionica M. HPLC organic acid analysis in different citrus juices under reversed phase conditions. Not Bot Hort Agrobot Cluj Napoca. 2010;38(1):44–8.Google Scholar
- 21.Sánchez-Machado DI, López-Cervantes J, Martínez-Cruz O. Quantification of organic acids in fermented shrimp waste by HPLC. Food Technol Biotechnol. 2008;46(4):456–60.Google Scholar
- 25.Guideline ICH. Validation of Analytical Procedures: Text and Methodology Q2 (R1), 2005. Available at http://www.ich.org/cache/compo/363-272-1.html 2010.
- 27.General Purpose Media (GPM). Tryptone Soya Broth (Casein soya bean digest medium) EP/USP/JP/BP by Thermo Scientific (Oxoid Microbiology Products), 2013. Available at http://www.oxoid.com/UK/blue/prod_detail/prod_detail.asp?pr=CM0129.
- 33.Nack Z. Microbiocidal activity of selected weak organic acids, PhD thesis. NOVA: The University of Newcastle’s Digital Repository, 2012. Available at http://hdl.handle.net/1959.13/936167.
- 34.Drug Future, Chemical Index Database, Citric Acid. 2013; Available at http://www.drugfuture.com/chemdata/citric-acid.html (accessed April 28, 2014).
- 41.Gargiulo DA, Sheridan J, Webster CS, Swift S, Torrie J, Weller J, Henderson K, Hannam J, Merry AF. Anaesthetic drug administration as a potential contributor to healthcare-associated infections: a prospective simulation-based evaluation of aseptic techniques in the administration of anaesthetic drugs. BMJ Qual Saf. 2012;21:826–34.PubMedCrossRefGoogle Scholar