Chromatography Forum

I trying to figure out how to obtain the concentration my result in mg/ml in a typical swab cleaning analysis.

Let's say

Area sample peak = 100
Area standard peak = 25
Weight of standard = 25 mg
Dilution vol of standard = 100 ml
Dilution vol of swab = 15 ml

Therefore

Conc. = (100/25) x (25mg/100ml) x (15ml/1 swab) = 15 mg/swab

Is this correct? I want to obtain conc. in mg/ml not mg/swab

Just eliminate that last factor.

Just eliminate that last factor.

I need to account for diluting the swab somehow. Is it okay to use a dilution factor of 15 rather than including the ml/swab?

I want to ask: what really is your intended sample?

1. The liquid squeezed out from the swab?

2. The swab plus its portion of stick?

3. Or are you just concerned about the concentration in the 15ml that the swab was extracted with?

I want to ask: what really is your intended sample?

1. The liquid squeezed out from the swab?

2. The swab plus its portion of stick?

3. Or are you just concerned about the concentration in the 15ml that the swab was extracted with?

Number 3.

I will be testing alcohols swabs that the label indicates are 70% alcohol and I want to confirm this number.

I want to ask: what really is your intended sample?

1. The liquid squeezed out from the swab?

2. The swab plus its portion of stick?

3. Or are you just concerned about the concentration in the 15ml that the swab was extracted with?

Number 3.

I will be testing alcohols swabs that the label indicates are 70% alcohol and I want to confirm this number.

I think you want #1. The swab is just the carrier/applicator, the liquid is what gets on the skin and must be 70% alcohol. So my sample would be the liquid squeezed from the swab.

I want to ask: what really is your intended sample?

1. The liquid squeezed out from the swab?

2. The swab plus its portion of stick?

3. Or are you just concerned about the concentration in the 15ml that the swab was extracted with?

Number 3.

I will be testing alcohols swabs that the label indicates are 70% alcohol and I want to confirm this number.

I think you want #1. The swab is just the carrier/applicator, the liquid is what gets on the skin and must be 70% alcohol. So my sample would be the liquid squeezed from the swab.

Yes #1 is what I am trying to get at. Unfortunately I am unable to squeeze enough liquid from the swab. The only way would be to extract it with some solvent or record the weight a wetted swab, then try it and record the weight of the dry swab to determine the amount of the liquid. With the liquid extraction method, I can't figure out a way or know if it's even possible to get a result in v/v% or w/w%

With the method all you can determine is the concentration of alcohol in the 15ml the swab was extracted into or the weight of alcohol in the swab.

Without knowing the weight or volume of solution wetting the swab you can't know the concentration of that solution. If there is 1g of solution on the swab and you measure 0.7g alcohol you will have 70%, but if you measure 0.7g alcohol and the swab had 2g solution then the concentration was 35%. The volume or weight of the solution is a necessary factor needed to calculate the concentration of the solution.