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Detection of Impurities by LC/MS

Christine MillerAgilent Technologies Introduction
The analysis of raw materials and finished prod- The analysis was performed using an Agilent 1100 ucts for minor impurities presents a challenge in Series LC/MSD SL. A decomposed stock solution many industries. Liquid chromatography/mass of salbutamol sulfate (10 mg/ml) was diluted in spectrometry (LC/MS) is often the technique of water to 100 pg/µl and injected directly into the choice because of its broad sample applicability, LC/MSD. The sample was analyzed in positive separating power, and ability to provide structural electrospray ionization (ESI) mode. Data analysis information. However, without advanced software was performed using the LC/MSD ChemStation tools, it is difficult to locate minor impurities in the presence of chemical noise and high-levelcomponents. This application brief demonstratesthe use of the Agilent 1100 Series LC/MSD SLquadrupole mass spectrometer with ChemStationsoftware for the analysis of minor components ina partially decomposed sample of the broncho-dilator salbutamol.
This Manual: Using Software Tools to Improve the Detection of Impurities Results and Discussion
Figure 1A shows the total ion chromatogram (TIC) Chromatographic Conditions
for the analysis of the decomposed salbutamol sample. While there were hints of several peaks in the 6.9 to 9.5 minute range, the impurities were largely obscured in the chromatographic baseline.
A two-step ChemStation data analysis procedure was used to extract meaningful information from this chromatogram. The first step involved the background subtract (BSB) routine, which sub- tracts the selected background spectrum from each point in the entire MS data set and saves the results as a separate file so that the original data MS Conditions
is always preserved. For this sample, an averaged spectrum from near the apex of the salbutamol peak was background subtracted resulting in greatly enhanced visualization of the impurities Second, the “Overlay base peak chromatogram” (BPC) feature was used to further improve the detection of impurities. The BPC is constructed from the base peak abundance of each scan in theanalysis, where the base peak in a spectrum is theion with the maximum abundance. Creating theBPC of the background-subtracted data for thesalbutamol analysis revealed that there were eightor more impurities previously hidden in thechromatographic baseline (Figure 1C).
This Manual: Using Software Tools to Improve the Detection of Impurities A. Display TIC
Possible impurities
B. Subtract salbutamol spectrum from TIC
C. Create base peak chromatogram
from background-subtracted TIC
Figure 1. Sequence of steps to extract impurity peaks from total
This Manual: Using Software Tools to Improve the Detection of Impurities Figure 2 shows the pseudomolecular ion for each have been obtained by increasing the LC/MSD chromatographic peak as well as spectra for some fragmentor voltage to generate collision induced of the impurities. While this analysis was suffi- dissociation or by using the MS/MS capabilities of cient to satisfy the immediate need, further an Agilent 1100 Series LC/MSD Trap ion trap structural information for the impurities could m/z 224
m/z 461
m/z 238
m/z 240
m/z 210.1
m/z 282
m/z 134
m/z 226
m/z 431
m/z 238
Figure 2. Mass spectral information for salbutamol impurities
This Manual: Using Software Tools to Improve the Detection of Impurities Conclusions
This work demonstrates that the LC/MSD Chem- Christine Miller is an applications chemist at
Station software is a powerful system for analysis Agilent Technologies in Palo Alto, California of sample impurities. The ChemStation software provides useful tools for locating minor compo-nents previously hidden in the chromatographicbaseline.
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All rights reserved. Reproduction, adaptation or translation without prior written permission is prohibited, except as allowed under thecopyright laws.
Printed in the U.S.A. August 16, 20025988-7611EN This Manual:


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