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Meaning of "sigma total (s)"
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Author:  PASegura [ Wed Jan 29, 2014 2:52 pm ]
Post subject:  Meaning of "sigma total (s)"


I was wondering what is the meaning of "sigma total (s)" in the "Compounds section"? I guess it is related to peak width but I didn't obtain the same value with my calculations.

Author:  pgboswell [ Wed Feb 05, 2014 5:15 pm ]
Post subject:  Re: Meaning of "sigma total (s)"

Hi Pedro,

Sorry it took me so long to get back to you. Good question. I need to add that to the help files. For isocratic elution, sigma is calculated from:

double dSigma = Math.sqrt(Math.pow(dRetentionTime / Math.sqrt(m_dTheoreticalPlates), 2) + Math.pow(m_dTimeConstant, 2) + (1.0/12.0) * Math.pow((m_dInjectionVolume / 1000.0) / (m_dFlowRate / 60.0), 2) + dTubingTimeBroadening);

or in non-Java language:

sigma^2 = (RetentionTime/SQRT(N))^2 + TimeConst^2 + (1/12)(InjectVol/F)^2 + (Broadening from post-column tubing)

For gradient elution, peak broadening is calculated based on the k of the solute right as it elutes and injection volume doesn't affect peak width (we assume the gradient is steep enough and the solute retained enough for this to hold true). Therefore,

double dSigma = Math.sqrt(Math.pow((m_dVoidTime * (1 + kprime)) / Math.sqrt(m_dTheoreticalPlates), 2) + Math.pow(m_dTimeConstant, 2) + dTubingTimeBroadening)

or in non-Java language:

sigma^2 = ((t0(1 + kf))/SQRT(N))^2 + TimeConst^2 + (Broadening from post-column tubing)

where t0 is the dead time, kf is the retention factor at elution, and N is the number of theoretical plates.

I hope that answers your question. I'll answer more quickly next time.


Author:  PASegura [ Thu Feb 06, 2014 10:29 pm ]
Post subject:  Re: Meaning of "sigma total (s)"

Thank you for your reply Paul. I'll let you know about other bugs or issues. I'd like to congratulate you and all the team that developed HPLC simulator, it is a great educational tool! If I can contribute let me know!

Author:  fifacoins07 [ Tue Jul 29, 2014 10:10 pm ]
Post subject:  Re: Meaning of "sigma total (s)"

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