Picaridin

[Gulliver3]

has anyone come across a source for Picaridin spray in Aus? Apparently needs to be at least 20 percent to be effective. Found an online site for Sawyer brand here but expensive.
phil

[GPSGuided]

'Off!' Available in your local Coles supermarket.

[Gulliver3]

Yes I saw that but couldn't find what percentage of Picaridin it contained.
phil

[Strider]

191g/L = 19.1%

[Gulliver3]

Thanks fellas, should work fine for Kokoda at half the price plus postage. Your maths is better than mine Strider!
phil

[GPSGuided]

Strider the chemist!

[Strider]

My maths is appalling but that's pretty easy to work out.

If 1mL = 1g.

Then 191g/1000mL*100 = 19.1%

[Gulliver3]

well here is a challenge beyond me. if it contains 19.1 ml per litre, how much Picaridin would be in 175ml?
phil

[Eremophila]

175ml x 19.1% = 33.425ml.
191ml per litre, not 19.1ml.

[GPSGuided]

Wait, was that how you guys did the calculation? Thought you'll need to know the molecular weight of picaridin to calculate.

229.3g/mol

[icefest]

Wait, was that how you guys did the calculation? Thought you'll need to know the molecular weight of picaridin to calculate.

229.3g/mol

I think you just need the density.
If it's given in g/l and you want to convert to %vol/vol

[GPSGuided]

Your right. It's been a while since I had to do one of these calcs. Given the nature of it, it'll have a density greater than water, therefore...

[Nuts]

Maybe the '20%' refers to ml/l?

[icefest]

The msds that I found has this:

[eman]

Thought I would add to this as I wasted time in the shop as the Off! product doesn't print the percentage on the label

The density of Picaridin is 1.07g/ml (at 20°C) according to http://www.drugfuture.com/chemdata/picaridin.html

Off! Tropical Strength at 191g/L has a percentage of 20.4% (191 x 1.07 = 204.37ml/L).

Off! Familycare version at 92.8g/L has a percentage of only 9.9% (92.8 * 1.07 = 99.296ml/L)

[GPSGuided]

Anyone know if Picaridin is stable over time? I leave mine in the car through all seasons and wondered if it'll go off after a while?

[slparker]

You're looking at simple concentration expressed as a percentage of weight per volume.

Pharmaceutical solutions are expressed as weight per volume i.e. a 0.1% adrenaline solution is 1mg/ml (or 1g/L). You don't need the molecular weight for this calculation - it is an expression of weight of solute to solvent in grams/L.

The OFF! Tropical strength at 191g/L is a 19.1% solution. A 20% solution ought to be 200g/L. If you buy the Off tropical strength you will not achieve the 20% the OP is after but it is pretty close. That wouldn't worry me at all. I would just wear long sleeves, soak my clothes in permethrin and spray my exposed skin with the 19.1% solution.

Once it is prepared in the factory the molecular weight, temperature, latitude or angle of your tongue does not effect the concentration of the solution. I am not sure of the stability of the picaridin compound though - so long as you use it before the use by date it should be fine.