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Biomedical subjects

Francis M Urry

Publications and source records attributed to Francis M Urry.

9 recordsLinked to original sources
PubMed2006

Drug monitoring and toxicology: a procedure for the monitoring of oxcarbazepine metabolite by HPLC-UV.

This article describes a rapid high-performance liquid chromatographic (HPLC) method for the measurement of the primary metabolite of oxcarbazepine. Following a simple precipitation step, 10,11,-dihydro-10-hydroxy-5H-dibenzo(b,f)azepine-5-carboxamide is quantitated (5-60 microg/mL) by analysis on an HPLC-UV system. The instrument time is less than 5 min per injection, an improvement over most published methods. The assay's limit of quantitation, linearity, imprecision, and accuracy adequately cover the therapeutic range for appropriate patient monitoring. In comparison to other published methods, this procedure would be of interest to clinical laboratories because it employs a precipitation step for sample preparation, instead of conventional yet time-consuming solid-phase extraction.

Anticonvulsants↗
PubMed2005

Assessing analytical specificity in quantitative analysis using tandem mass spectrometry.

OBJECTIVES: The necessity of confirmation of compound identity in quantitative analysis is well recognized for methods utilizing single mass spectrometry detection but is not commonly addressed for applications utilizing multiple-stage mass spectrometry (MSn). For MSn detection, no commonly accepted rules for assessment of analytical specificity in quantitative analyses have been established to date. METHODS: To assure compound identity, we evaluated approaches based on monitoring multiple mass transitions of a target compound followed by comparison of the branching ratios of the mass transitions. RESULTS: Monitoring multiple mass transitions along with evaluation of the ratio of their relative intensities allows the analyst to distinguish the target analyte from interferences in quantitative analysis. The strategy and the acceptance criteria are compound and method specific and should be established during the method development and validation. CONCLUSIONS: The certainty of analyte identity is very important in quantitative analysis using MSn detection; methods to verify analyte identity should be used in all critical applications.

Cortisone↗
PubMed2005

Simultaneous analysis of the Delta9-THC metabolites 11-nor-9-carboxy-Delta9-THC and 11-hydroxy-Delta9-THC in meconium by GC-MS.

Neonates that are exposed to cannabinoids in utero may have characteristic physical and mental developmental problems throughout their lives. The early identification of exposed neonates allows early intervention and anticipation of potential problems. Testing meconium detects maternal marijuana use over the last four months of gestation, providing a better drug exposure marker than urine. However, the distribution of metabolites in meconium is not identical to urine and analytical methods must be adapted. Both the major urine metabolite, 11-nor-9-carboxy-Delta9-tetrahydrocannabinol (9-carboxy-THC), and a minor urine metabolite, 11-hydroxy-Delta9-tetrahydrocannabinol (11-hydroxy-THC), are common in meconium. Currently published methods to extract these two metabolites for instrumental analysis are time-consuming and laborious, often involving the preparation of two fractions. This study describes a simple solid-phase extraction method and an optimized hydrolysis method that allow the preparation and analysis of both metabolites in a single extract. The limit of detection by this extraction method was 5 ng/g for both metabolites with an analytical measurement range from 10 to 500 ng/g. The recovery at 100 ng/g was greater than 62% for both analytes. The analysis of 246 cannabinoid screen positive specimens illustrated the importance of including the 11-hydroxy-THC in a meconium marijuana confirmation: 16 specimens confirmed positive for 11-hydroxy-THC only, resulting in a 6.5% increase in the positivity rate compared to 9-carboxy-THC alone.

Dronabinol↗
PubMed2005

Comparison of sample preservation methods for clinical trace element analysis by inductively coupled plasma mass spectrometry.

The effects of chemical additives and storage temperatures on measurement of 16 trace elements in urine by inductively coupled plasma mass spectrometry (ICP-MS) were evaluated. A 24-hour urine specimen was supplemented with concentrations of the elements. Aliquots containing 1 of 4 chemical additives were stored at 3 different temperatures in sealed polypropylene containers. Elemental concentrations were determined by ICP-MS for the resulting samples after 1, 2, 8, and 65 days of storage. Initial element concentrations measured within 8 hours of specimen preparation were consistent with expected concentrations (except for aluminum). For most elements, preservation and storage conditions yielded consistent measured concentrations throughout the experiment. Notable exceptions were for aluminum (general rise over time) and mercury (general decrease over time). Adding boric acid and potassium pyrosulfate resulted in sample contamination; elemental contamination was concentration-dependent for both. Although little microbial contamination was observed during the experiment, refrigeration of samples is recommended to curtail bacterial growth in nonsterile specimens. In light of these results, refrigerated urine storage without the use of chemical additives is an effective preservation method for ICP-MS analysis of many trace elements.

Humans↗
PubMed2002

Analysis of catecholamines in urine by positive-ion electrospray tandem mass spectrometry.

BACKGROUND: Determination of urinary catecholamines (CATs) is considered important for clinical diagnosis of pheochromocytoma, paraganglioma, and neuroblastoma. The major disadvantages of existing tests include relatively long instrumental analysis time and potential interference from drugs and drug metabolites that are structurally similar to CATs. METHODS: CATs were extracted from a 300-microL aliquot of urine by a two-step liquid-liquid extraction method specific for compounds containing a catechol group. Chromatographic separation did not require the use of ion-pairing reagents, which typically hinder MS detection but are frequently used in HPLC analysis of CATs. Instrumental analysis was performed by electrospray ionization tandem mass spectrometry (ESI-MS/MS) in the multiple-reaction monitoring mode. Stable-isotope-labeled CATs were used as internal standards. RESULTS: Epinephrine (E), norepinephrine (NE), and dopamine (D) were measured within 3.5 min instrumental run time. Quantification limits were 2.5 microg/L for E and D and 10 microg/L for NE. The total imprecision (CV) was < or =9.6%; extraction recoveries were 71% +/- 12%. CONCLUSIONS: HPLC with ESI-MS/MS in combination with sample preparation specific to catechol group-containing compounds allows rapid testing for disorders associated with increased CAT concentrations. The method is free of interferences from drugs and drug metabolites, which commonly interfere with HPLC methods.

Catecholamines↗
PubMedDate not supplied

A rapid procedure for the monitoring of amiodarone and N-desethylamiodarone by HPLC-UV detection.

This article describes a rapid isocratic high-performance liquid chromatographic (HPLC) method for the simultaneous measurement of the antiarrhythmic drug amiodarone and its potentially active metabolite N-desethylamiodarone (DEA). Following a simple liquid-liquid extraction, amiodarone and its metabolite are quantitated (0.3-6.0 mg/L) by analysis on an HPLC-UV system. The analytical time was reduced by 50%, without compromising the assay performance, when Rocket column technology was employed. The assay's limit of quantitation, linearity, imprecision, and accuracy adequately covered the therapeutic range for appropriate patient monitoring. Amiodarone and DEA can be simultaneously and accurately quantitated in serum or plasma by HPLC-UV detection with imprecision < 6% at therapeutic concentrations and a quantitation range from 0.3 to 6.0 mg/L. Monitoring of this drug can allow for effective use, while minimizing serious side effects.

Amiodarone↗
PubMedDate not supplied

Drug monitoring and toxicology: a procedure for the monitoring of levetiracetam and zonisamide by HPLC-UV.

This article describes a rapid isocratic high-performance liquid chromatographic (HPLC) method for the simultaneous measurement of the anticonvulsants levetiracetam and zonisamide. Monitoring these drugs is important for detecting potentially toxic concentrations, particularly in patients with renal impairment, but no commercial assays are currently available. Following a liquid-liquid extraction, levetiracetam (5-150 microg/mL) and zonisamide (5-80 microg/mL) are quantitated by HPLC-UV. The assay's limit of quantitation, linearity, imprecision, and accuracy adequately cover the therapeutic range of these drugs. The assay should be attractive to clinical laboratories because the run time for quantification of both drugs is approximately 5 min per sample, and no interferences are currently known.

Anticonvulsants↗