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

13internalstandard.pdf

4 Pages
86 Views
Unlock Document

Department
Chemistry
Course
ENCH 213
Professor
Diane Beauchemin
Semester
Fall

Description
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


OR

Join OneClass

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

Sign up

Join to view


OR

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.


Submit