Hello Arputharaj:

Your question is not very clear without giving us the details when you say "Each research article has a different way of calculating EF". I will try to help you, as much as I can, with the numbers you have given us.

The basic definition of the enrichment factor as you indicated is:

EF = Final concentration/ initial concentration.

The initial metal concentration of Cu = 100 ng/mL

Initial Sample volume = 4 mL.

The final concentration of Cu (after elution) = 70 ng/mL

if we go by the concentration during your process:

EF = (70 ng/mL)/(100 ng/mL) = 0.7 (it is a factor and has no units). If you express it in "percent", it would be 70%.

However, you also mention that

The initial volume = 4 mL and the final volume is 2 mL.

Then, the absolute amount of Cu that was present in your sample

= 100 mg/mL x 4 mL = 400 ng.

If you did not lose any of Cu during the process, the final concentration "should" be:

= 400 ng / 2 mL = 200 ng/mL

Then, the "expected" EF = (200 ng/mL) / (100 ng/mL) = 2

However, your measured concentration is only 70 ng/mL (not 200 as expected), which indicates that you have not recovered all the Cu during elution. Then, you can calculate the "Recovery".

Recovery = Observed amount/expected amount

= measured concentration in the final solution/ expected concentration.

= 70/200 = 0.35, or 35%.

Please note that EF can have any value from < 100% to > 100%.

Please feel free to give us more details, if the above explanation is not clear.

Regards,

EF = (C_sample - C_blank) / C_initialWhere:C_sample is the concentration of the metal in the sample after SPE.C_blank is the concentration of the metal in the blank sample (usually the initial concentration of the metal in the SPE cartridge).C_initial is the initial concentration of the metal in the sample before SPE.

Thank you for the response Nimal De Silva and Hagar Sabry.

In response to Nimal De Silva . "Each research article has a different way of calculating EF". The different formula in article which i have mentioned in my raised question is given below.

Enrichment factor (EF) = cd/cs = ((nd ×Vs)/(ns ×Vd))

Whereas, cdand cs represents the analyte concentration in used desorbed solution and sample solution; nd and ns are number of analyte moles, and Vd and Vs denotes the used desorption solvent and sample volume, respectively.

Hello Arputharaj:

The main reason for confusion is we tend to mix the two:

Enrichment factor and Recovery.

According to the article you have referred to

"Enrichment factor (EF) = cd/cs = ((nd ×Vs)/(ns ×Vd)) "

EF = cd/cs (we are talking about the enrichment the analyte with respect to the "concentration".

If there was no loss during the process, nd = ns, and the recovery is 100%.

Then, EF would be Vs/Vd, which is fixed. However, if nd < ns, recover is

Nimal De Silva thank you for your immediate response and clear explanation, which was really helpful for me.!