In healthcare, outdoor emergency response, and everyday cleaning scenarios, saline packets (premixed saline packets) are highly relied upon for their portability and standardized concentration. However, when readily available, many consider making their own saline packets using regular table salt. Is this a viable option?
The Core Difference Between Regular and Medicinal Salt: Purity and Composition
Regular table salt (such as refined salt) is primarily composed of sodium chloride (NaCl), but to meet food processing requirements, anti-caking agents (such as potassium ferrocyanide) and iodide are often added. While harmless to humans, these additives can cause problems in certain situations:
- Anti-caking agent residue: Long-term exposure can clog the micropores of medical devices (such as nebulizers and nasal irrigators), affecting their effectiveness.
- Iodide Interference: In laboratory or industrial salt spray tests, iodide can alter the solution's conductivity and corrosiveness, leading to distorted experimental data. For example, the salt spray test requires sodium chloride to be ≥99.5% pure and free of impurities such as copper and nickel. Ordinary salt cannot meet this standard.
Scenarios for Making Salt Water with Ordinary Salt
Despite differences in composition, ordinary salt can be used as an alternative in the following scenarios:
Low-risk cleaning applications:
When used to wipe surfaces or clean simple wounds, a solution containing ordinary salt can remove some dirt and bacteria. However, the following conditions must be met:
Use purified water that has been boiled and then cooled to avoid microbial contamination.
The concentration must be strictly controlled to 0.9% (isotonic solution). Higher concentrations can damage cell tissue, while lower concentrations can affect the antibacterial effect.
After preparation, filter out visible impurities using filter paper or sterile gauze.
Short-term emergency use:
When specialized products are unavailable, ordinary salt can be used to make a temporary solution to relieve nasal congestion or rinse the eyes (with closed eyes and eye movement). However, it is important to note:
Avoid using iodized salt or flavored salts (such as lemon salt or vanilla salt).
For single use only; do not reconstitute or store. Educational Uses:
When demonstrating the principles of osmotic pressure or the solubility of salt, common salt can be used as a low-cost teaching aid to help students understand the concepts of isotonic, hypertonic, and hypotonic solutions.
Limitations of Common Salt: Contraindications in High-Risk Scenarios
In the following scenarios, the risks of using common salt as an alternative significantly outweigh the benefits:
Intravenous injection or internal irrigation:
Medical saline solutions must undergo aseptic production processes and undergo endotoxin testing. Even filtered solutions of common salt do not meet injectable standards and may cause sepsis or thrombosis.
Cleaning Precision Instruments:
Device cleaning, such as endoscopes and artificial joints, requires saline solutions prepared with purified water. The calcium and magnesium ions in common salt can form scale, shortening the life of the equipment or affecting test results.
Long-Term Wound Care:
Chronic wounds (such as diabetic foot and pressure ulcers) require specialized saline solutions containing silver ions or antibiotics. Common salt solutions cannot inhibit the growth of drug-resistant bacteria and may delay treatment.
Laboratory or Industrial Use:
Salt spray testing, cell culture, and other applications require strict salt purity and impurity content. Ordinary salt can cause skewed experimental data or equipment corrosion.
Key Steps in Scientifically Preparing Salt Water
If you need to use ordinary salt to prepare a temporary salt water solution, strictly follow the following process:
- Salt Selection: Prefer non-iodized refined salt. Avoid sea salt (which contains more impurities) or low-sodium salt (which contains insufficient sodium chloride).
- Weighing: Use a precision electronic scale to weigh the salt, maintaining an accuracy within ±0.1g. For example, 4.5g of salt is required to prepare 500ml of 0.9% salt water.
- Dissolution and Filtration: Add the salt to boiling purified water, stir until completely dissolved, and filter through a 0.22μm filter membrane (if specialized filter membranes are unavailable, use multiple layers of sterile gauze).
- Sterilization: Aliquot the solution into sterile containers and sterilize by autoclaving (121°C for 15 minutes) or irradiating with ultraviolet light for 30 minutes.
- Storage: Store sealed and protected from light. Once opened, use within 24 hours to avoid microbial contamination.
Whether ordinary salt can be used in place of medical salt in saline packs depends on the risk level of the specific application. In low-risk scenarios, strict formulation can be used as a temporary emergency measure; however, when using internal organs, delicate equipment, or for long-term care, specialized products are essential. Understanding the core role of salt purity, concentration, and sterility is crucial to avoiding health risks stemming from "saving money" or "convenience."
