Class Notes (838,272)
Canada (510,817)
Chemistry (266)
ENCH 213 (25)


4 Pages
Unlock Document

ENCH 213
Diane Beauchemin

Internal standardisation And multivariate optimization Principle of internal standardisation • add internal standard to all samples and standards • ratio of analyte signal over that of the internal standard is used for quantitation • if the internal standard behaves like the analyte, their signal ratio will be independent of variations in instrument response or in the quantity of sample analyzed Requirements (in chromatography) • internal standard peak is completely resolved from adjacent peaks • internal standard is not originally present in the sample • internal standard does not have an interference effect on the analyte • internal standard elutes close to the analyte i.e. it behaves like the analyte Internal standardisation in chromatography • highest precision attained • compensation for variation in operating conditions and sample injection Internal standardization is useful in chromatography when: • part of the sample does not elute completely • part of the analyte may be lost during sample pretreatment ◦ add internal standard BEFORE sample pretreatment • the amount of sample injected varies from injection to injection Correction for the detector’s response factor • if an equimolar amount of the internal standard and analyte do not induce the same change in signal: ◦ take into account the response factor, F, of the detector ◦ an empirical response factor must be determined for each compound vs a "standard" compound ◦ concentration soluteoncentration standardF (area solutereastandard Example of how to find the response factor -8 - -8 • 8.0x10 M I, 6.4x10 M p-dichlorobenzene (int. std.) give a relative detector response area/Irea int. Std 0.71 • F= • F= 1.76 ◦ the detector is 1.8 times more sensitive to p-dichlorobenzene than to I- when both are present at the same concentration Example of how to apply the response factor • area int. std.centration int.std • (area solutencentration solute • if same concentration of internal standard in an unknown solution of I : - ◦ measured area soluteea int.std.21 ◦ ◦ • a calibration curve should be made to verify that the detector’s response is linear up to this concentration Internal standardisation in ICP spectroscopy • the inductively coupled plasma is a powerful atomizer • all elements of the Periodic Table can be atomized and excited Sources of signal variation in ICP spectroscopy • Nebulizer ◦ aerosol formation • Spray chamber ◦ aerosol p
More Less

Related notes for ENCH 213

Log In


Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.