Re: Swipe Testing

[John Elliott <jcell@ibm.net>]

At 10:17 AM 9/30/97 -0500, you wrote:
>What swipe test media are commonly used when the analytical method is liquid 
>scintillation counting?  I am currently using "Whatman" Number 1 filter papers 
>(42.5mm).
>
>Any of you who are conducting wipe tests care to share what you use and do you 
>prep. them in any way (wet vs. dry)?
>
>William A. Lorenzen
>Children's Hospital
>Boston, MA 02115
>
>Phone:	617-355-7516
>Fax:	617-738-4526
>E-mail:	lorenzen_w@a1.tch.harvard.edu
>
>
>William A. Lorenzen
>Children's Hospital
>Boston, MA 02115
>
>Phone:	617-355-7516
>Fax:	617-738-4526
>E-mail:	lorenzen_w@a1.tch.harvard.edu

Since we typically had several thousand wipes to perform each quarter, I developed a 2 stage SOP for wipe testing that would cut time and materials.

For the first stage was a rough survey involving maybe 5-10 wipes per lab. A 1cm Whatman #1 or #41 filter was numbered with a pencil to match a numbered room diagram(ink adds luminesence or quenching), sprayed with isopropyl alcohol, and used to wipe a large section of the survey area (example, 1 wipe for an entire bench top).  The wipe was placed in a microcentrifuge tube with 1.5 ml of ultima Gold (Packard) cocktail and counted after dark adaptation. Packard microcentrifuge adapters were needed for the LSC. 

If a positive result was obtained, the area in question was   re-wiped in 100 cm2 sections with 2.54cm GF/A Whatman glass fiber filters (example - if the bench top wipe described above were hot, perhaps 6-12 GF/A wipes would be taken on the bench top to identify the area).  The GF/A wipes were counted in 20 ml polyethylene vials with 15 ml of Ultima Gold cocktail.

This system allowed us to do initial surveys very rapidly with minimal materials or waste cost.  Since only 1-5% of wipes in any batch were positive, we quickly identified areas which needed "proper" 100cm2 wipe testing procedures

See also Health Physics 64(1):86-90; 1993 Liquid Scintillation Analysis in Microcentrifuge Tubes

Good luck

John Elliott
jcell@ibm.net