Quantitation using HRMS: A new tool for rapid, specific and sensitive determination of catecholamines and deconjugated methanephrines metanephrines in urine

Urinary catecholamines and their methylated metabolites are biochemical indicators of pheochromocytoma, paraganglioma and neuroblastoma. A rapid and precise analytical method based on solid-phase extraction (SPE) and liquid chromatography separation coupled to high-resolution mass spectrometry (LC-HRMS) was developed and validated to measure urinary catecholamines (epinephrine (E), norepinephrine (NorE), dopamine (D)) and total methylated metabolites (normetanephrine (NorMN), metanephrine(MN) and 3-methoxytyramine (3-MT)) in a clinical setting. Results of 51 urine specimens measured using this LC-HRMS method were compared with a liquid chromatography assay with electrochemical detection (LC-EC). Urine samples (200 μL) were spiked with an internal standard solution followed by SPE purification. In the case of total methylated metabolites, urine was hydrolyzed before SPE purification. Separation was achieved on an Acclaim Mixed Mode WCX column, with an 8.5 min runtime. All compounds were detected in electrospray positive ionization mode with a parallel reaction monitoring acquisition and quantified with a linear regression (r2 > 0.998) between 2 and 200 µg/L (10.9-1090; 11.8-1182 nmol/L) for E and NorE respectively and between 10 and 1000 µg/L for others (65.2-6520; 50.7-5070; 54.5-5450 ; 59.8-5980 nmol/L for D, M, NorMN and 3-MT, respectively). Overall imprecision and bias did not exceed 15%. No significant matrix effect was observed. Correlation between the two assays was good except for epinephrine. Epinephrine concentrations measured by LC-EC method were slightly higher than values obtained with LC-HRMS method but without impact on clinical decision. This LC-HRMS assay provides a new tool for simultaneous quantitative catecholamine determination and was successfully applied in routine for the screening or follow up of pheochromocytoma, paraganglioma and neuroblastoma. LC-HRMS method offers significant advantages compared to LC-EC with good sensitivity, an unambiguous analyte determination and high sample throughput.

Detection of spot urinary free metanephrines and 3-methoxytyramine with internal reference correction for the diagnosis of pheochromocytomas and paragangliomas

Detection of normetanephrine (NMN), metanephrine (MN) and 3-methoxytyramine (3-MT) could be used to diagnose pheochromocytomas and paragangliomas (PPGLs). The accuracy for the diagnosis of PPGLs is only 6% by virtue of the classic symptom triad. In addition, false-positive results were found using plasma free MNs as biomarkers. Spot urinary free metanephrines (MNs) presented high specificity for PPGLs diagnosis in our previous work by HPLC with the electrochemical detection. Whereas, MNs and creatinine (Cr) need to be detected separately. A simple and specific method was urgently needed for the diagnosis of PPGLs. Here, we established a new HPLC method for spot urinary free MNs and 3-MT by the fluorescence detection and Cr by the ultraviolet detection simultaneously. It was worth mentioning that Cr for the virtue of being fairly constant in a given subject was used as an internal reference correction to eliminate the effect of spot urine volume for the diagnosis of PPGLs. Thirty-seven patients with PPGLs and 164 control subjects were detected by the established method and the peak area ratios of MNs and 3-MT to Cr were used innovatively for the diagnosis of PPGLs. The results showed acceptable precisions and recoveries. The sensitivities of the method were 94.6%, 91.9% and 86.5% and the specificities were 96.3%, 93.9% and 82.3%, respectively by the peak area of NMN/Cr, MN/Cr and 3-MT/Cr for the diagnosis. The established method provides a promising way for simple, rapid and accurate diagnosis of PPGLs.

Comparison of Three Extraction Approaches for the Isolation of Neurotransmitters from Rat Brain Samples

The determination of neurotransmitters (NTs) as relevant potential biomarkers in the study of various central nervous system (CNS) pathologies has been demonstrated. Knowing that NTs-related diseases mostly occupy individual regions of the nervous system, as observed, for instance, in neurodegenerative diseases (Alzheimer’s and Parkinson’s Diseases), the analysis of brain slices is preferred to whole-brain analysis. In this report, we present sample preparation approaches, such as solid-phase extraction, solid-phase microextraction, and dispersive liquid–liquid microextraction, and discuss the pitfalls and advantages of each extraction method. The ionic liquid (1-ethyl-3-methylimidazolium tetrafluoroborate)-assisted solid-phase microextraction (IL-SPME) is found to be, in our research, the relevant step towards the simultaneous determination of six NTs, namely, dopamine (DA), adrenaline (A), noradrenaline (NA), serotonin (5-HT), l-tryptophan (l-Trp), l-tyrosine (l-Tyr) in rat brain samples. The development of a novel bioanalytical technique for the evaluation of biomarkers in the context of green chemistry might be accelerated just with the use of IL, and this approach can be considered an advantageous strategy.

Role of Mass Spectrometry in Clinical Endocrinology

The advent of mass spectrometry into the clinical laboratory has led to an improvement in clinical management of several endocrine diseases. Liquid chromatography tandem mass spectrometry found some of its first clinical applications in the diagnosis of inborn errors of metabolism, in quantitative steroid analysis, and in drug analysis laboratories. Mass spectrometry assays offer analytical sensitivity and specificity that is superior to immunoassays for many analytes. This article highlights several areas of clinical endocrinology that have witnessed the use of liquid chromatography tandem mass spectrometry to improve clinical outcomes.

Rapid determination of catecholamines in urine samples by nonaqueous microchip electrophoresis with LIF detection

A method was developed for the rapid separation of catecholamines by nonaqueous microchip electrophoresis (NAMCE) with LIF detection, A homemade pump-free negative pressure sampling device was used for rapid bias-free sampling in NAMCE, the injection time was 0.5 s and the electrophoresis separation conditions were optimized. Under the optimized conditions, the samples were separated completely in <1 min. The average migration times of the epinephrine (E), dopamine (DA), and norepinephrine (NE) were 34.26, 43.81, and 50.07 s, with an RSD of 1.05, 1.26, and 0.89% (n = 7), respectively. The linearity of the method ranged from 0.0125 to 2.0 mg/L for E and 0.025~4.0 mg/L for DA and NE, with correlation coefficients ranging between 0.9978 and 0.9986. The detection limits of E, DA, and NE were 2.5, 5.0, and 5.0 μg/L, respectively. The recoveries of E, DA, and NE in spiked urine samples were between 86 and 103%, with RSDs of 4.5~6.8% (n = 5). The proposed NAMCE with LIF detection combined with a pump-free negative pressure sampling device is a simple, inexpensive, energy efficient, miniaturized system that can be successfully applied for the determination of catecholamines in urine samples.

Simultaneous measurement of urinary metanephrines and catecholamines by liquid chromatography with tandem mass spectrometric detection

BACKGROUND

The measurement of catecholamines and metanephrines in urine is an important diagnostic test in biochemical screening for phaeochromocytoma. Tandem mass spectrometry (MSMS) has the potential to be used in a profiling method for simultaneous assay of these analytes.

METHODS

Optimal conditions were established for the MSMS detection of catecholamines (noradrenalin, adrenalin and dopamine) and metanephrines (normetanephrine and metanephrine), including commercially available isotopically labelled compounds for use as internal standards. Chromatographic separation of all five polar biogenic amines was achieved under solvent conditions that were compatible with MSMS and multiple reaction monitoring. Several types of solid-phase extraction cartridge were used to investigate clean-up conditions for urine, and acid-hydrolysates of urine, prior to LC-MSMS.

RESULTS

Total catecholamines and metanephrines from acid-hydrolysed urines, or free catecholamines and free metanephrines from native urines, were complexed with diphenyl-boronate and recovered in high yield from polymer cartridges after elution with formic acid. Direct injection of eluates into the LC-MSMS system allowed quantitation of catecholamines and metanephrines with a run time of 6 min per sample. Biogenic amine concentrations for patient urines and quality assurance programme samples, and assay imprecision, were similar to values obtained with high-performance liquid chromatography methods, which used electrochemical detection. In normal urines, the ratio of free to total catecholamines was around three-fold higher than the ratio of free to total metanephrines.

CONCLUSION

The assay of urinary catecholamines and metanephrines can be achieved simultaneously using one LC-MSMS method, which is rapid and reduces labour and consumable costs for routine application.

Chromatographic and mass spectrometric methods for quantitative determination of 3-nitrotyrosine in biological samples and their application to human samples

The permanent modification of soluble and protein-associated tyrosine by nitration results in the formation of 3-nitrotyrosine, which can be used as a marker of "nitro-oxidative" damage to proteins. Based on the analysis of patient materials, over 40 different diseases and/or conditions have been linked to increased nitration of tyrosine. They include many cardiovascular diseases, conditions associated with immunological reactions and neurological diseases. In this article we review the existing chromatographic and mass spectrometric methods for quantitative measurements of 3-nitrotyrosine in different human biological samples including plasma, either from the free amino acid pool or from hydrolyzed proteins from different matrices.

Pheochromocytoma: recommendations for clinical practice from the First International Symposium. October 2005

The First International Symposium on Pheochromocytoma, held in October 2005, included discussions about developments concerning these rare catecholamine-producing tumors. Recommendations were made during the symposium for biochemical diagnosis, localization, genetics, and treatment. Measurement of plasma or urinary fractionated metanephrines, the most accurate screening approach, was recommended as the first-line test for diagnosis; reference intervals should favor sensitivity over specificity. Localization studies should only follow reasonable clinical evidence of a tumor. Preoperative pharmacologic blockade of circulatory responses to catecholamines is mandatory. Because approximately a quarter of tumors develop secondary to germ-line mutations in any one of five genes, mutation testing should be considered; however, it is not currently cost effective to test every gene in every patient. Consideration of tumor location, presence of multiple tumors, presence of metastases, and type of catecholamine produced is useful in deciding which genes to test. Inadequate methods to distinguish malignant from benign tumors and a lack of effective treatments for malignancy are important problems requiring further resolution.

Review: derivatization in mass spectrometry-6. Formation of mixed derivatives of polyfunctional compounds

The review describes chemical transformations of multifunctional compounds (amino acids and peptides, amino alcohols, amino thiols, hydroxy acids, oxo acids, oxo alcohols, compounds containing simultaneously three or more different groups etc.) by using step-wise or one-step modification or protection of functional groups. Some chemical aspects of mixed derivatization performed for improving the physical-chemical properties and mass spectral characteristics are discussed. Application of mixed derivatization to qualitative and quantitative analysis of various multifunctional compounds mainly in biological fluids and other matrices by gas chromatography/mass spectrometry in electron ionization, chemical ionization, negative-ion chemical ionization and selected ion monitoring modes is considered.

Assessment of O-methylated catecholamine levels in plasma and urine for diagnosis of autonomic disorders

The term 'metanephrines' is used to indicate the two catechol 3-O-methylated metabolites of epinephrine (E) and norepinephrine (NE): metanephrine and normetanephrine (NMN). The corresponding 3-O-methylated metabolite of dopamine is usually referred to as 3-methoxytyramine rather than 3-methoxydopamine and is not generally considered a "metanephrine". O-Methylation occurs outside the sympathetic neuron and neuroeffector junction. Metanephrines are products of the enzyme catechol-O-methyltransferase (COMT). Subsequent conjugation with sulfate or deamination by monoamine oxidase (MAO) followed by reduction to vanilmandelic acid (VMA) facilitates urinary excretion. For the clinician, measurement of normetanephrine provides an index of norepinephrine released during sympathetic nervous system activity, whereas metanephrine concentration provides an indication of adrenal medullary metabolism of epinephrine prior to its discharge into the circulation. Plasma epinephrine concentration is the preferable index of adrenal medullary epinephrine discharge. Pheochromocytomas, with their protean clinical manifestations, may be diagnostic challenges, but assay of metanephrines, especially plasma metanephrine, can be particularly helpful in diagnosis. These COMT metabolites may also help in elucidation of still undiscovered genetic and acquired disorders of catecholamine metabolism.

Phaeochromocytoma with normal urinary catecholamines: the potential value of urinary free metadrenalines

BACKGROUND

Normal urine catecholamine values in patients with phaeochromocytoma is an occasional finding and may lead to a missed diagnosis. Additional urinary free metadrenaline analysis may be of value in this situation.

METHODS

In addition to vanillylmandelic acid, homovanillic acid and the catecholamines, urinary free normetadrenaline (fNMA) and free metadrenaline (fMA) were measured. This report describes six confirmed cases of phaeochromocytoma showing normal urinary catecholamine output and compares fMA results and tumour size with other confirmed cases where the urine catecholamines were increased.

RESULTS

Urine catecholamines in these patients with, on average, smaller tumours, were all normal. Urinary fNMA and fMA were available on five patients, and were increased in three. The data suggest that, unlike the catecholamines, urinary fNMA and fMA could be a useful predictor of tumour size.

CONCLUSION

The inclusion of fNMA and fMA in the test profile is likely to be of additional benefit in tumour detection, particularly when catecholamines or other metabolites are normal.