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Day 2: TP26
Comparative Analysis of the API 4000 to the API 3000 LC/MS/MS System for Quantitative Analysis of Prostaglandins in Dog Urine: A Look at Sensitivity, Dynamic Range, and Signal to Noise

Jerry Muhammad¹, Hideji Fujiwara¹, Mary Triefenbach¹, Gary Impey², Clevys Monasterios² and Kevin Duffin^1
1Pharmacia, Analytical Sciences Center, 700 Chesterfield Parkway, St. Louis, MO 63198
²Applied Biosystems MDS Sciex, Product Application Laboratory, 71 Four Valley Drive Concord, Ontario, Canada L4K 4V8

Prostaglandins are potent signaling molecules that are present in biological tissues and fluids in picomolar to low nanomolar levels. They comprise a class of eicosanoids that also includes thromboxanes and leukotrienes. All the eicosanoids are derived from arachidonic acid, and have similar structures and molecular weights. Quantification of prostaglandins in a complex biological matrix such as urine is challenging. The quantitation method must be sensitive and selective for each of the many different eicosanoids. Liquid chromatography coupled with triple quadrupole mass spectrometry has been used in past studies for selective quantitation of numerous members of the eicosanoid class. Here, we compared two triple quadrupole mass spectrometers, the PE-Sciex API-3000 and PE-Sciex API-4000 for their ability to quantify two isomeric prostaglandins, PGE2 and PGD2, and 11-dehydro thromboxane B2 in dog urine. Overall sensitivity based on signal/noise, dynamic range, and linearity of signal were compared on identical samples in the study. In order to evaluate these parameters both instruments were optimized in the negative ion mode. Deuterated prostaglandins E2, D2, and 11-dehydro thromboxane B2 were spiked into dog urine over a range of 0.002-1000 ng/ml for the study. A reversed-phased solid phase extraction was used for sample purification. Both instruments provided linear response over the concentration range used in this study. The API 4000 showed reduced noise levels compared to the API 3000, which resulted in limits of quantitation that were at least 4x better than those obtained with the API 3000. The overall LOQ obtained using the API 4000 was 0.062 ng/mL when the eicosanoids were separated on a 1.0 mm column with a flow of 75 microliters/minute. The overall sensitivity of the two mass spectrometers was also compared using larger bore HPLC columns with increased flow rates and data showing the differences in signal and noise levels will be presented.

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