A clinical assay for the measurement of milrinone in plasma by HPLC mass spectrometry.

Milrinone is a bipyridine phosphodiesterase inhibitor with positive inotropic and vasodilatory effects. As interest in longer term use of intravenous therapy increases, it becomes essential to monitor its plasma concentration owing to a narrow therapeutic range, an increased half-life in renal failure and toxicity associated with high levels. A high-performance liquid chromatography (HPLC) method with mass (MS) detection using a triple quadrupole mass spectrometer is presented. The method was compared with the UV/HPLC method and validated according to current international guidelines. Coefficients of variation of less than 7.5% were obtained across the therapeutic range and 18.3% at 2.4 ng/mL, the lower limit of quantitation. Plasma from 13 cardiac surgery patients receiving standard intravenous doses of milrinone were measured. Eight patients achieved therapeutic milrinone levels within 3-4 h post start of infusion, one was borderline sub-therapeutic and four patients achieved levels that were above the upper limit of the therapeutic range and potentially toxic. This method offers high sensitivity, is rapid, easy to use and requires minimal amount of sample. We believe this method could become the reference procedure for clinical monitoring of milrinone and help to improve the safety of the use of this drug in patients with cardiac failure.

Accurate mass liquid chromatography/mass spectrometry on quadrupole orthogonal acceleration time-of-flight mass analyzers using switching between separate sample and reference sprays. 2. Applications using the dual-electrospray ion source.

A new electrospray dual sprayer, LockSpray, was developed for accurate mass measurements on a quadrupole orthogonal acceleration time-of-flight mass spectrometer (oa-Q-ToF). With the dual-sprayer ion source, both sprays are orthogonal to each other. A mechanism similar to the one employed on the multiplexed electrospray source (MUX) allows switching between reference and sample sprayer. The reference sprayer is optimized for low flow rates, whereas the sample sprayer is a conventional Z-spray type sprayer. Earlier work using a modified MUX ion source on an orthogonal acceleration time-of-flight instrument showed promising results. In this paper, examples obtained with the LockSpray, specifically designed for accurate mass measurements on an oa-Q-ToF, are presented. The examples include results obtained for the identification of impurities in drug substances such as cimetidine and rosiglitazone, using accurate mass tandem mass spectrometry in both positive and negative ion electrospray modes. Good mass accuracies, i.e., within 2 mDa of the theoretical value, were obtained in MS and MS/MS operation.

High-performance liquid chromatography linked to inductively coupled plasma mass spectrometry and orthogonal acceleration time-of-flight mass spectrometry for the simultaneous detection and identification of metabolites of 2-bromo-4-trifluoromethyl.

The use of HPLC coupled to inductively coupled plasma mass spectrometry (ICPMS) and orthogonal acceleration time-of-flight (oa-TOF) for the profiling, identification, and quantification of metabolites in rat urine following the administration of 2-bromo-4-trifluoromethylacetanilide is described. The metabolites present in the sample were separated by reversed-phase gradient chromatography with UV-diode array detection. The bulk of the eluent (90%) from the UV detector was directed to an ICPMS where bromine-containing metabolites were detected and quantified using ICPMS. The minor portion of the eluent (10%) was taken for oa-TOFMS for identification. By these means, the metabolites were identified as sulfate and glucuronide conjugates of a ring hydroxy-substituted metabolite, a N-sulfate, a N-hydroxylamine glucuronide, and N- and N-hydroxyglucuronides.

Directly coupled liquid chromatography with inductively coupled plasma mass spectrometry and orthogonal acceleration time-of-flight mass spectrometry for the identification of drug metabolites in urine: application to diclofenac using chlorine and sulfur detection.

We report the application of high-performance liquid chromatography (HPLC) linked to inductively coupled plasma mass spectrometry (ICPMS) and orthogonal acceleration time-of-flight mass spectrometry (oa-TOFMS) for the identification of phase I and II urinary metabolites of diclofenac. The metabolites were separated by reversed-phase HPLC monitored with a UV diode array detector (UV-DAD) after which 90% of the eluent was directed to an ICPMS source, with the remainder going to an oa-TOF mass spectrometer. Compounds containing (35)Cl, (37)Cl and (32)S were detected specifically using ICPMS and identified by oa-TOFMS. The metabolites detected and identified in this way included glucuronic acid and sulfate conjugates, mono- and dihydroxylated and free diclofenac. In addition a previously unreported in vivo metabolite, an N-acetylcysteinyl conjugate of diclofenac, was also characterised. This is the first application of the combination of HPLC/UV-DAD/ICPMS/oa-TOFMS for the investigation of the metabolic fate of chlorinated xenobiotics by direct biofluid analysis.

Accurate mass liquid chromatography/mass spectrometry on orthogonal acceleration time-of-flight mass analyzers using switching between separate sample and reference sprays. 1. Proof of concept.

This paper describes the use of two separate electrosprays for introducing sample and reference for accurate mass liquid chromatography/mass spectrometry (LC/MS) on an orthogonal acceleration time-of-flight mass analyzer. This is carried out using an adaptation of the multiplexed electrospray ion source in which only two of the sprays are utilized. Results are shown for the positive ion detection of trace-level components in complex matrixes and good mass accuracies are obtained, even for very low level components. An example of accurate mass measurements obtained using negative ion LC/MS is also shown. To obtain additional structural information, an example of cone voltage fragmentation is included and shows that good mass accuracy can be obtained for both precursor and fragment ions.