This document describes the analysis challenges of D-penicillamine enkephalin (DPDPE) and the rapid sensitive analysis of DPDPE in cerebrospinal fluid using an Agilent 1100 Series LC/MSD mass spectrometer. DPDPE is a synthetic enkephalin used for pain control, which has proven difficult to analyze in the past. The document also provides detailed information on the experimental method and sample preparation process.
This document presents an application note detailing a method for the rapid quantification of D-penicillamine enkephalin (DPDPE), a synthetic analgesic, in cerebrospinal fluid (CSF). The study, conducted by researchers at the University of California, San Diego in collaboration with Agilent Technologies, addresses the difficulty of analyzing DPDPE due to its disulfide bridge, which makes immunoassays unpredictable.
The note outlines an experimental procedure involving sample extraction using Millipore ZipTip pipette tips followed by analysis via selected ion monitoring (SIM) mode on the Agilent 1100 Series LC/MSD quadrupole mass spectrometer. The document provides specific instrument conditions, including LC and MS parameters, and reports on the method's performance, demonstrating excellent linearity, accuracy within 10.2%, and precision within 9.33% across a concentration range of 1 to 1000 ng/ml.
| Flow rate | 0.4 ml/min |
|---|---|
| Mobile phase | isocratic 75:25 methanol:10 mmol ammonium formate (pH 3) |
| Ionization mode | positive ESI |
| Nebulizer | 20 psig |
| SIM ions | 646.2 DPDPE, 570.7 IS |
| Limit of quantitation (LOQ) | 1.00 ng/ml |
| Extraction efficiencies | between 97% and 102% |
The limit of quantitation (LOQ) was 1.00 ng/ml.
The accuracy was within 10.2% and the precision was within 9.33%.
Extracted samples were stable for 48 hours with a relative standard deviation of +/- 7.4%.