T E C H N O L O G YCLEANROOM

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June 2013

THE INTERNATIONAL JOURNAL OF CONTAMINATION CONTROL

WIPES & DISINFECTANTS ARE NOT ALWAYS THE IDEAL MATCH● EU Biocide regulations about to bite● Best practice on storing reference cultures● What to consider with floor coverings

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18 CLEANROOM TECHNOLOGY June 2013 www.cleanroom-technology.co.uk

Different wipe substrates and disinfectants caninteract in ways that can interfere with disinfectionefficacy. Karen Rossington looks at past studiesinto incompatibility and what it means in practice

Due to the numerous benefits ofpresaturated wipes – including easeof use, lowering of VOCs, increased

convenience and reduction of hazardouswaste – the use of such wipes within thepharmaceutical industry and especially thehealthcare industry has proliferated in thepast few years. The majority of the originalpresaturated wipes were alcohol-based anddisinfectant presaturated wipes were lesswidely used. There are now numerous non-sterile disinfectant wipes available,predominantly for infection control use inhealthcare environments. There are fewertypes of sterile disinfectant wipes availablebut they are becoming more routinely usedin pharmaceutical and biotech industries.

However, do all these wipes perform aswell as expected and are the results the sameas for the ready-to-use fluids? The addition ofa disinfectant to a wipe substrate is not aseasy as may first be expected. There are someknown problems arising from adding certaindisinfectant actives to particular wipe ormop substrates.

Incompatibility between the disinfectantand the substrate: Two disinfectants knownto be problematic with wipe and mopmaterials are chlorine-based disinfectants(such as hypochlorites) and quaternaryammonium compounds. Organic materialsconsume available chlorine, therebyreducing the disinfectant capacity ofchlorine-based disinfectants. This is not aproblem when using a fluid straight onto asurface, as providing the surface is cleaned oforganic matter prior to disinfection,chlorine-based disinfectants are both fast-acting and effective.

A cost-effective and commonly usedpresaturated wipe substrate is cellulose orcellulose blends, mainly because cellulose isa relatively cheap material and the wipesprovide good absorbency. However, it is anatural organic material and, therefore,theoretically it will use up all the free chlorineif used as the base for a hypochloritedisinfectant wipe.

This was borne out by work carried out in2007,1 when cotton wipes and cellulosebased wipes were placed in an open bucketsystem for up to 72 hours (hrs). As bleach canbe unstable over time, the testing period waslimited to 72 hrs. The study found that after24 hrs, the amount of chlorine ion releasedfrom the cellulose-based wipe was 28% lowerthan the original bleach solution and thechlorine ion release from the cotton wipeswas 11% lower than the original solution.

In comparison, a nonwoven wipe that wastested after 72 hrs had only 3% lowerchlorine release, showing that the choice ofwipe substrate was key in ensuring howmuch free chlorine remained and hence theefficacy of the disinfectant solution was notcompromised by the wipe substrate. This

effect can be even more significant when thewipes are irradiated.

There is a similar issue observed withwipes and mops presaturated withquaternary ammonium compounds (quats)but for a differing reason. R Bloss et al2

conducted a study to look at the absorptionof the active ingredients of different surfacedisinfectants onto different types of fabric.

They compared two different solutions ofbenzalkonium chloride (quat), gluter-aldehyde and propan-1-ol on four differentfabrics (polyester/cellulose pulp, viscoserayon, polyester and a mix of viscose,cellulose and polyester). The fabrics wereimmersed in each solution for up to 24 hrsand then the wipes squeezed in astandardised way to remove the eluate. Theeluate was then tested to determine whatlevel of active ingredient was left. Resultsshowed that the quat was strongly absorbedonto both the cellulose-based wipes up to61% after only 30 mins and the viscose rayonwipes up to 70% after 30 mins. Even themixed wipes with a smaller amount ofcellulose and rayon absorbed 54% after 7 hrs.

Because of its structure the polyester fibreabsorbed the smallest amounts of quat: just17% in 15 mins. It was only with the polyesterfibre that the quat solution remained withinits working range. The gluteraldehyde andpropan-1-ol were not adsorbed by any of thefabrics to any great degree and bothsolutions remained within their workinglimits. The paper concluded that an effectivesurface disinfection regime has to includethe selection of an appropriate fabric.

Other research has come to the sameconclusion: MacDougall and Morris3

showed that a nonwoven wipe released anaverage of 90% of the original concentrationof quaternary ammonium solution after

8 hrs but a cellulose-based wipe releasedonly 21% of the original concentration. In awhite paper4, Ecolab surmised this bindingof a quaternary ammonium compound tocertain fabrics was due to quats beingcationic or positively charged surfactantsand being attracted to fabric surfaces that areanionic or negatively charged. This results inthe binding of a portion of the quat to thefabric and becoming unavailable to disinfectthe surface.

The studies went on to discuss variousways in which this problem could beovercome: by careful selection of thesubstrate; by allowing for the loss andstarting with a higher concentration of quatin solution so that the amount released is stillabove the required kill level; by submersingthe wipes for a very short period of time, i.e.dip and wipe method; or by using a very largevolume of solution to a small amount of wipematerial (not entirely practical).

All of the published work looked at whathappened over relatively short time periodsfor mops and wipes saturated for immediateuse. Even over these short time periods adrop in active ingredient was observed thatcould significantly affect the overall effective-ness of a biodecontamination regime. Ifthere were compatibility issues, these couldbe severely aggravated by a presaturatedwipe, where the fluid is in contact with thewipe for an extended period.

European disinfectant wipe testing: InEurope there is no specific efficacy testing forpresaturated wipes. There is a phase 2, step 2test that incorporates a back and forthwiping procedure across four test areas,simulating in use conditions. However, thetest is currently still under development. Inthe US, both the AOAC and ASTM havestandards with published methods for

Wipe anddisinfectantcompatibility

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testing presaturated wipes for microbialactivity that are similar in their basic design.However, at the most basic level it would bepossible to utilise the existing standard ENsuspension and surface tests on eluateextracted from the wipe at the end of shelflife to show that the wipe being in contactwith the fluid had not had any adverse effecton the efficacy of the disinfectant.

When evaluating presaturated wipes it iscrucial to ensure that efficacy testing hasbeen carried out on fluid extracted from thewipe, otherwise (as the studies have shown)the fabric could have had an unknowndetrimental effect on the disinfectant thatworked perfectly well as a ready-to-use fluid.

Presaturated disinfectant wipe testing:Work was carried out on a range of sterileand non-sterile presaturated wipes currentlyon the market to see if there had been anypotential negative effect from the wipe onthe efficacy of the disinfectant. Wipes atvarious points within their shelf life weresqueezed to a standardised method toremove as much fluid as possible from thewipe and then the eluate was tested againstthe standard EN disinfectant tests, EN 1276for bacterial efficacy,5 EN1650 for fungalefficacy6 and EN 13704 for sporicidalefficacy.7 Table 1 shows the results obtainedand where the wipe eluate did not reach therequired level of efficacy as claimed for theequivalent fluid product.

The contact time to prove sporicidalefficacy against EN 13704 is 60 mins.However, as this does not tend to be practicalin use, many companies test at a shortercontact time of between 3 and 15 mins. Thetest work was carried out at 15 mins, which isa longer contact time than claimed for any ofthe products tested.

As can be seen from these results, many ofthe wipes tested did not meet the claimsmade for the equivalent RTU fluid. The testswere performed twice to eliminate anypossible error in the testing (all tests did passvalidation). In common with the previousstudies, alcohol (both IPA and denaturedethanol) worked well in conjunction with avariety of wipe substrates, showing efficacycomparable to claims for the fluid product.The quaternary ammonium-based productsshowed failures against the fungal test. Thiswould support previous studies that if thefluid used to saturate the wipes has the sameactive concentration as the RTU fluid, thefact that the quaternary ammonium

compound is binding to the wipes couldleave insufficient active in the depositedfluid to get the required kill. In all cases therewas enough active quat for a bacterial kill butnot enough to kill the more resistant fungi.

A similar result was observed for theamphoteric surfactant disinfectants; theseare also attracted towards negatively chargedfabrics and remain bound to the wipe itself.This can be visibly seen on some of the wipesas the wipe changes colour where the fluid isabsorbed. A quick check of pH and colour forthe failed products showed that either pHand/or colour had fallen out of the ready-to-use specification.

Hydrogen peroxide is an equilibrium �

Table 1: Presaturated disinfectant wipe testing

Wipe info Efficacy – wipe extract

Active ingredient Wipe substrate Shelf life at time EN1276 EN1650 EN13704of testing

Amphoteric surfactant Polyester / Cellulose 15 months Fail Fail N/A

Amphoterics / Biguanide Polyester / Cellulose 18 months Fail Fail N/A

Quat / Biguanide Polyester / Cellulose 8 months Pass Fail N/A

Quat / Biguanide Polyester / Cellulose 3 months Pass Fail N/A

Quat / Chlorine dioxide Polyester / Cellulose 10 months Pass Pass Fail 15 min

Hydrogen peroxide Polyester / Cellulose 8 months Pass Fail Fail

Hydrogen peroxide Polyester 20 months Pass Fail Fail

Hydrogen peroxide Rayon blend ? 3 months Pass Pass N/A

Hypochlorite Polyester 7 months Pass Pass Pass

Hypochlorite Rayon blend ? 9 months Pass Pass Fail 15 min

IPA Polyester / Cellulose 14 months Pass Pass N/A

IPA Polypropylene 4 months Pass Pass N/A

Denatured ethanol Polyester / Cellulose 11 months Pass Pass N/A

Denatured ethanol Polypropylene 13 months Pass Pass N/A

cleaning systems

The effect of presaturated wipe substrates on the long-term effectiveness ofdisinfectant actives requires consideration

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CONTACT

Karen Rossington is a marketing consultant forContec Inc● info@contecinc.com ● www.contecinc.com

References1. V Williamson, Infection Control Today, Vol 11 No 8 (Aug2007)2. R Bloss, S Meyer, G Kampf. Journal of Hospital InfectionVol 75 Nov 20103. D MacDougall and C Morris, Infection Control Today, Vol10 (June 2006)4. Ecolab white paper http://www.ndhealth.gov/disease/hai/Docs/QuatAbsorptionEcoLab.pdf5. BS EN 1276:1997 Chemical Disinfectants and Antiseptics -Quantitative suspension test for the evaluation of bactericidalactivity of chemical disinfectants and antiseptics used in food,industrial, domestic and institutional areas6. BS EN 1650:1998 Chemical Disinfectants and Antiseptics- Quantitative suspension test for the evaluation of fungicidalactivity of chemical disinfectants and antiseptics used in food,industrial, domestic and institutional areas7. BS EN 13704:2002 Chemical Disinfectants and Antiseptics- Quantitative suspension test for the evaluation of sporicidalactivity of chemical disinfectants used in food, industrial,domestic and institutional areas8. IEST-RP-CC004: Evaluating Wiping Materials Used inCleanrooms and Other Controlled Environments Aug 2004Institute of Environmental Sciences and Technology9. Contec Technical Note TN0515 Comparison ofpresaturated wipes against EN standard efficacy tests

product where contact with certain materialsis likely to start the decomposition process,known as “gassing off”. Hydrogen peroxidebreaks down to water and oxygen, and thisdecomposition process can leave a wipe withlittle to no activity and a pouch overfilledwith air (oxygen) as shown in Figure 1. Thiscould be the cause of the lack of activityobserved for the hydrogen peroxide wipes.

A quick check of the percentage ofhydrogen peroxide in the products that hadfailed showed that the level of hydrogenperoxide had dropped out of specification,down as low as 4.42% instead of aspecification of 5.5%–6.5%. Interestingly, forhypochlorite-based products, where asignificant interaction is well known, one ofthe wipes behaved well because thesubstrate chosen was polyester so there wasno organic material to cause an adverseeffect on the efficacy, and the other failedagainst spores.

Previous studies used HPLC and gaschromatography to assess whether there wasa lower percentage of active ingredient in theeluate removed from the wipe. A more basicassessment was carried out in this instance,merely comparing the residue onevaporation (EP method) for the originalfluid with the fluid removed from the wipes.With the exception of the alcohols and thehydrogen peroxide, the active ingredients inthe disinfectants will leave a residue on thesurface. What these results show (Table 2) isthat in all cases the residue on evaporationfor the fluid from the wipe was significantlylower than the residue on evaporation fromthe ready-to-use fluid – showing that asignificant portion of the active material hadbeen retained on the wipe.

Effect on the wipe substrate itself: Whilethe wipe can have an effect on the fluid, thefluid can also have an effect on the wipe.Some of the more aggressive surfacedisinfectants have the ability to break downthe wipe substrate, allowing it to generatemore fibres and particles. Careful choice of

over sprays and dry wipes for the applicationof disinfectants but a customer must be surethat one and one does equal two when adisinfectant is added to a wipe or mop. CT

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20 CLEANROOM TECHNOLOGY June 2013 www.cleanroom-technology.co.uk

The author would like to acknowledge the input and workcarried out by Neil Simpson, R&D, Contec and to thank NickTodd from Microtechnica for the loan of the particle counter.

substrate can significantly reduce oreliminate this problem. To see if the wipesthat had poor efficacy results had beenbroken down, a test was carried out using abiaxial shaker to remove particles from thewipes and then the fluid was analysed using aliquid particle counter. The particles wereextracted from the wipe in accordance withthe procedures in IEST-RP-CC004.38 using aGilson Sieve Shaker. The number of particlesin the fluid were then analysed using aHiac/Royco 3000A/8000A liquid syringe sampler.

In one particular case there was visibledegradation of the wipe: the number ofparticles in the extract fluid were so great thatthey were visible in the fluid itself, showingthat there had been a significant breakdownof the wipe material. The cloudiness that canbe seen in Figure 2 is caused by particlessuspended in the fluid. The beaker on the leftcontains liquid extracted from one of thesporicidal wipes on a polyester/cellulosesubstrate; the beaker on the right containsalcohol solution as a comparison.

Results from the particle counter showedthat polyester/cellulose wipes presaturatedwith a range of disinfectants released moreparticles than when the wipes were dry, andsome fluids affected the wipe material morethan others. Polypropylene wipes that werepresaturated with alcohol did not releasesignificantly more particles than the dryequivalent wipe.9

In conclusion, as can be seen from theresults of this and previous studies, carefulconsideration should be given bymanufacturers to the effect of presaturatedwipe substrates on the long-termeffectiveness of the active ingredients. Simpletesting of the fluid extracted from the wipe atthe end of shelf life would show whether anydecomposition or binding of the active wasoccurring. Efficacy testing carried out on theextract fluid at end of shelf life would confirmthat there has been no detrimental effect onthe efficacy of the disinfectant over time.Presaturated wipes have significant benefits

Table 2: Summary wiper comparison data

Product Residue on Product Residue on evaporation/ppm evaporation/ppm

Quat / Biguanide wipe 4643 Quat / Biguanide liquid 6106

Quat / Chlorine dioxide wipe 8310 Quat / Chlorine dioxide liquid 20595

Hydrogen peroxide wipe 2269 Hydrogen peroxide liquid 547

Amphoteric surfactant wipe 999 Amphoteric surfactant liquid 62213

Quat / Biguanide wipe 4841 Quat / Biguanide liquid 5256

Amphoterics / Biguanide wipe 538 Amphoterics / Biguanide liquid 5948

IPA wipe 197 IPA liquid 1

Denatured ethanol wipe 94 Denatured ethanol liquid 25

IPA wipe 50 IPA liquid 0

Denatured ethanol wipe 53 Denatured ethanol liquid 2

IPA wipe 296 IPA liquid 6

Figure 1

Figure 2

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