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Sample Swab≠Cotton Bud, What causes some to turn yellow

Although the sample swab resembles a cotton swab, it is not one.

Difference between a sampling swab and a cotton bud?

Nylon fiber, polyurethane sponge, or rayon are common materials similar to toothbrushes.

Electrostatic interaction is used to uniformly and vertically cover the end of the swab handle with millions of microscopic fibers.

Elution is simpler and has a higher release rate since the sample obtained by the flocking swab remains on top of the fiber bundle and does not disperse or trap in the fiber. It does not impair the follow-up testing and has no adverse effects on pathogens, contact cells, or tissues.

“Sterile” and “Non-Sterile”?

China medical device evaluation experts said

Sterile: refers to the condition of having no living microorganisms, the medical device bearing the classification “sterile” has completed disinfection, and the theoretical likelihood of any surviving microbes should not be more than ten to the minus 6th power. Usually registered as Class Ⅱ Medical Device in China.

Should  “non-sterilized” swabs be disinfected before use?

It is not recommended to use a disinfectant to sanitize the swab head because this could degrade the sample and compromise the validity of the test results.

If accuracy requirements for sampling and detection exist, sterile swabs are highly recommended.

Why do some sample swabs yellowish and what causes them?

Swabs are individually wrapped, loaded, and delivered to other communities, where they are unpacked, disinfection, and distributed.

The disinfection route is the prime suspect among the other components since it has the potential to oxidize the swab and result in discoloration.

Verified by 11 different disinfectants, the results are as follows:

“+“: Slight discoloration, “++”: Serious discoloration, “-“: Normal appearance

NO.Common DisinfectantResult
1Sodium trichloroisocyanurate *1 Tablet: 500ml Water++
2Alkyl diethyl benzyl ammoniun chloride: Bisdecylhydrogen bromide = 1:10
3Hypochlorous acid
4Benzalkonium bronide 3g/L
5Hydrogen peroxide 3%
6Sodium hypochlorite 0.5g/L++
775% Alcohol
8Chloroxylenol:Water = 1:30
9Potassium permanganate tablets*1 Tablet: 50ml Water++
11Chlorine dioxide effervescent*1 Tablet: 100ml Water++

The sample swab contains some easily oxidized components, such as polyols, isocyanates, and urethanes.

Due to the properties of its substance, it can oxidize under bright light and high temperatures, or it can turn yellow due to gas fumigation when exposed to nitrogen oxides (NOx) in the air.

Nylon fiber generally has a stronger antioxidant capacity than polyurethane sponge swabs.

Swabs unavoidably encounter this phenomenon, hence it is advised to store at 20 to 30 °C avoid light to prevent yellowing.

“HCY, Health care for you” is our forever mission. We dedicate to offering safe & reliable products and medical services with our global creditable partners. HCY has already supplied to WHO, MAYO clinic, MGI, DDC, Yale University, Qorvo, Quanterix, Thomas Scientific, SD biosensor, Cardinal Health, Cleveland Clinic, Mars Petcare & LumiraDx, etc. in the past years.

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