APPLICATION OF LC-MS

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Determination of vitamin D3in poultry feed supplements using MS
Vitamin D is an essential constituent in human and animal nutrition. Livestock diets deficient in vitamin D can cause growth abnormalities.

Traditional GC/MS analysis methods for vitamin D in feed extracts require extensive and time-consuming sample preparation and derivatization prior to analysis. Atmospheric pressure chemical ionization with ion trap detection provides a sensitive analytical method without the need for extensive sample preparation and derivatization. Further, the multiple-stage MS capability of the ion trap eliminates the need for chromatographic separation, greatly speeding analyses.

Flow injection analysis of a poultry feed extract yields a peak at m/z 385 suggesting the presence of vitamin D

Isolation and fragmentation of the precursor ion at m/z 385 is inconclusive. The full scan product ion spectrum shows a prominent peak at m/z 367 representing the loss of a single water mole- cule but little other fragmentation (Figure)

Isolation and fragmentation of the ion at m/z 367 yields a full scan MSspectrum (Figure A) rich in structurally specific product ions. This spectrum is an excellent. match with a similar analysis of a pure standard (Figure B) and conclusively confirms the presence of vitamin D3

Environmental Applications

Detection of phenylurea herbicides
Many of the phenylurea herbicides are very similar and difficult to distinguish with a UV detector (Figure ). Monuron and diuron have one benzene ring and differ by a single chlorine. Chloroxuron has two chlorines and a second benzene ring attached to the first by an oxygen. The UV-Vis spectra are similar for diuron and monuron, but different for chloroxuron. When analyzed using electrospray ionization on an LC/MS system, each compound has a uniquely identifiable mass spectrum.

Detection of low levels of carbaryl in food
Pesticides in foods and beverages can be a significant route to human exposure. Analysis of the carbamate pesticide carbaryl in extracts of whole food by ion trap LC/MS/MS proved more specific than previous analyses by HPLC fluorescence and single-quadrupole mass spectrometry. The protonated carbaryl molecule (m/z 202) was detected in full scan mode using positive ion electrospray. A product ionat m/z 145 (Figure ) generated by collision- induced dissociation provided confirmation of carbaryl and was used for subsequent quanti- tative analysis. Ion trap analysis was more sensitive than previous analysis using a single-quadrupole mass spectrometer operating in scanning mode and more sensitive than fluorescence detection.

Ion trap LC/MS/MS also con- firmed false positives in the HPLC fluorescence analysis caused by a co eluting compound. Based on the MS/MS spectrum of the co eluting compound, a possible structure was assigned as shown in Figure .

[agilent.com& Michael Linscheid. Westmorel, D.G]

BIBLIOGRAPHY:

  • Basics of LC/MS by Agilent technology available at URL agilent.com accessed on 15/7/2011. Pg.no:4-6; 20-32.
  • Lee, M.S. Kerns, E.H. LC/MS application in drug development. New Jersey: Milestone Development Services Pennington. Pg.no:235-242
  • Michael Linscheid.  Westmorel, D.G. International  union of pure and applied chemistry. vol-66. No: 9. Printed in Great Britain.
  • Snyder, L.R. Dolan, J.W. High performance gradient elution the practical application of the linear-solvent-strength model.  A john Wiley & sons publication. Pg.no:326-328
  • Watson, D.G. Pharmaceutical analysis a text book for pharmacy student and pharmaceutical chemist. Published  by Churchill Livingstone. Pg.no:186-188.

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