Gas chromatographic measurement of urinary catecholamines by an electron capture detection procedure

Analysis of 9-fluorenylmethyloxycarbonyl derivatives of catecholamines by high performance liquid chromatography, liquid chromatography/mass spectrometry and tandem mass spectrometry

9-Fluorenylmethyloxycarbonyl (FMOC) derivatives of catecholamines, including dopamine (DA; 3,4-dihydroxyphenethylamine), norepinephrine (NE; 2-amino-1-(3,4-dihydroxyphenyl)ethanol) and epinephrine (EPI; 1-phenyl-1-hydroxy-2-methylaminopropane) as well as 3, 4-dihydroxybenzylamine (DHBA) have been analyzed using high performance liquid chromatography coupled to fluorometric detection and atmospheric pressure chemical ionization mass spectrometry at low femtomole levels. Structures of the derivatives have also been characterized by liquid chromatography/atmospheric pressure chemical ionization mass spectrometry and electrospray/tandem mass spectrometry. Protonated molecules of FMOC-DA and FMOC-DHBA as well as [M + H - H(2)O](+) ions of FMOC-NE and FMOC-EPI appear in their conventional mass spectra, and abundant fragments characteristic of catecholamines dominated the spectra. Structurally diagnostic ions using several hundred femtomoles of the FMOC derivatives of catecholamine were observed. Collision-induced dissociation (CID) of electrospray-generated protonated molecules of FMOC-DA and FMOC-DHBA as well as [M + H - H(2)O](+) ions of FMOC-NE and FMOC-EPI produced diagnostic product ion spectra. Liquid chromatography/atmospheric pressure chemical ionization mass spectrometric analysis of the FMOC derivatives of catecholamines and DHBA should prove useful in the separation and characterization of these compounds from biological materials.

Metabolism of phenylethanolamines and 2-oxo-2-phenylethylamines in the rat

1. The metabolism of a series of phenylethanolamines and 2-oxo-2-phenylethylamines was examined in vivo in the rat. 2. The urinary excretion of the corresponding mandelic acids was, in general, considerably greater for 2-oxo-2-phenylethylamines than for the corresponding phenylethanolamines. Of the putative metabolites of the former class of compounds only phenylglyoxals yielded mandelic acids.

Metabolism of dopamine analogues in rat

1. The metabolism of dopamine analogues, differing in their ring substituents and length of side chain, has been examined in rat. 2. Both benzylamines and phenethylamines were converted to their analogous acids. Where sought, the corresponding alcohols were present only in minute traces, or were undetectable. 3. Benzylamines were largely excreted as such, possibly conjugated, and this output, together with acid metabolites, accounts for most of the dose. In contrast, only a minor part of the phenethylamine dose was excreted unchanged, and much of what was given remains unaccounted for. 4. With increasing chain length the proportion of the dose found as urinary metabolites decreases markedly; long-chain (hydrophobic) amines may be sequestered in fat depots rendering them largely unavailable for metabolism. 5. beta-Oxidation of long-chain aromatic acids is observed. 6. Catechols showed evidence of O-methylation, and some O-methyl compounds were demethylated. N-methylation and N-demethylation were, at best, very minor pathways. 7. No overall pattern emerged between the position of substituents and the extent of oxidation by monoamine oxidase. No pattern at all was apparent with the benzylamines. Phenethylamines showed a trend towards a lower rate of metabolism for secondary and tertiary amines. Phenethylamines and propylamines with ortho substituents exhibited a lower rate of metabolite excretion than did their analogues.

Biogenic amines and their metabolites in body fluids of normal, psychiatric and neurological subjects

The biogenic monoamines and their metabolites have been isolated, identified and quantified in human body fluids over the past forty years using a wide variety of chromatographic separation and detection techniques. This review summarizes the results of those studies on normal, psychiatric and neurological subjects. Tables of normal values and the methods used to obtain them should prove to be useful as a reference source for benchmark amine and metabolite concentrations and for successful analytical procedures for their chromatographic separation, detection and quantification. Summaries of the often contradictory results of the application of these methods to psychiatric and neurological problems are presented and may assist in the assessment of the validity of the results of experiments in this field. Finally, the individual, environmental and the methodological factors affecting the concentrations of the amines and their metabolites are discussed.

Plasma catecholamines: laboratory aspects

In this review the methods used for analysis of plasma catecholamines in clinical chemical laboratories are discussed. The physiology of catecholamines as well as their measuring indications are discussed, together with concise evaluation of the methods most commonly used, namely indirect radioenzymatic assays or direct determinations by high-performance liquid chromatography combined with either electrochemical or fluorometric detection. The main advantage of radioenzymatic assay is its sensitivity and thus the need for only a small sample. Liquid chromatographic methods in general are less tedious, relatively rapid, and cheap, and omit the use of radionuclides. Both of these methods, however, are subject to a number of analytical errors, which can only be avoided by proper development of methods and skilled use of these methods. Little routine work is done using either radioimmunoassay or gas-chromatography.

Preparation of dopamine 3-O-sulphate and dopamine 4-O-sulphate as reference substances and high-performance liquid chromatographic trace determination

Simple syntheses of the biologically important but hitherto difficult to obtain dopamine sulpho conjugates dopamine 3-O-sulphate (I) and dopamine 4-O-sulphate (II), as analytical reference substances, starting from dopamine hydrochloride are described. A method for the determination of I and II with reversed-phase high-performance liquid chromatographic separation and coulometric detection in human urine together with calibration and current-voltage curves are presented. Detection limits of approximately 100 pg of I or II and unequivocal substance identifications even in very complex substrates such as human urine are reported.

Routine determination of plasma catecholamines using reversed-phase, ion-pair high-performance liquid chromatography with electrochemical detection

A procedure is described for the determination of plasma catecholamines using reversed-phase, ion-pair high-performance liquid chromatography coupled with electrochemical detection. Optimisation of chromatographic conditions with respect to detector performance and adherence to procedures and precautions described, render the method applicable to both neurochemical research and routine clinical analysis. The limit of quantitative detection of the method was found to be approximately 30 pg per injection for individual catecholamines. A single chromatographic run, providing adequate resolution of each component, could be completed in approximately 12 min.

Sulphate conjugation of isoprenaline by lung, small intestine and other organs

Isoprenaline, a sympathomimetic drug used in the treatment of asthma, was found to be sulphated by the bronchial tissues of the monkey and dog. Enzyme preparations of the liver, small intestine and kidney of various animals are also able to catalyze this sulphate conjugation reaction from ATP and inorganic sulphate and from a commercial preparation of adenosine 3'-phosphate 5'-sulphatophosphate (PAP35S) or PAP35S generated from Na235SO4 in vitro. The Km values for isoprenaline for the sulphotransferase of mouse liver and monkey lung, are respectively, 51,3 microM and 138 microM . The significance of this detoxication reaction is discussed in relation to (a) the importance of lung as a potential biotransformation site of isoprenaline, (b) asthma deaths supposed to be associated with the use of isoprenaline in the form of pressurised aerosols and (c) the ability of the different tissues to synthesize PAPS in vitro.

A method for the analysis of catecholamines by selected ion monitoring and 14C isotope dilution in adrenal medullary cell culture

Extracts have been made from culture medium of rat medullar adrenal cells developed in tissue culture in this laboratory. After pentafluorobenzylimine-trimethylsilyl ether formation the catecholamine derivatives were characterized by gas-liquid chromatography chemical ionization mass spectrometry. In order to assess the catecholamine production capabilities of the cells in culture, a mass spectrometric method with isotope dilution has been devised. Chemical ionization selected ion monitoring allows specific detection at the nanogram level in a higher mass range (400-600 amu) than in the electron impact mode. The isotopic dilution method with 14C catecholamines gives rise to accurate measurements and linear response in the picomole range. The use of the [M-15]+ ion for monitoring m/z values minimizes errors in selected ion monitoring analysis. The results obtained are computerized and treated by the data system for fine background subtraction when high sensitivity and accuracy are required.

Use of 2,6-dinitro-4-trifluoromethylbenzenesulfonic acid as a novel derivatizing reagent for the analysis of catecholamines, histamines and related amines by gas chromatography with electron-capture detection

We have found that 2,6-dinitro-4-trifluoromethylbenzenesulfonic acid reacts rapidly and specifically with primary amines at room temperature. We have used this reagent for derivatizing phenylethylamines, including catecholamines, and histamine and 1-methylhistamine. After the reaction, hydroxyl groups were derivatized to form the corresponding trimethylsilyl ethers, and the final derivatives were analyzed by gas chromatography with electron-capture detection. These derivatives are stable, possess excellent gas chromatographic properties and are detected with high sensitivity. We have applied this method to the analysis of histamine and 1-methylhistamine in human urine.

Separation and quantification of urinary di- and polyamines by gas chromatography with electron capture detection

A sensitive and specific gas chromatographic assay procedure employing electron capture detection has been developed for the assay of free and total di- and polyamines in human urine. Urine samples, hydrolysed with hydrochloric acid where necessary for the measurement of total amine output, were evaporated to dryness and, after the residues had been taken up in water, purified successively on Porapak Q and Dowex 50 X2 columns. Following evaporation of eluate, pentafluoropropionyl derivatives were made and analysed gas chromatographically using temperature programming. Di- and polyamines can be measured accurately at the picomole level and normal urinary output values calculated using this method agree well with those noted by other workers.

Metabolism of 3, 4-dihydroxyphenylalanine, its metabolites and analogues in vivo in the rat: urinary excretion pattern

The metabolism and interrelationships of orally and intraperitoneally administered L-dopa, related amino acids and their metabolites have been studied 2. Amino acids were decarboxylated. N-Methyldopa formed dopamine but not epinine. D-Dopa was absorbed from the intestine and metabolized by a series of reactions which resulted in greater decarboxylation than was observed after L-dopa. Transamination was a minor pathway. 3. m-Hydroxylated phenylpyruvic acids were poorly reduced, but vanilpyruvic acid was reduced fairly readily. Lactic acids were largely unchanged. Lactic and pyruvic acids formed phenylethylamines and their metabolites. Small amounts of phenylpyruvic acids may be decarboxylated to phenylacetic acids. 4. Glycine conjugates were formed from phenylacetic acids, a partially reversible change 3,4-Dihydroxyphenylacetic acid was metabolized to homovanillic and m-hydroxyphenylacetic acids, especially when given orally. Little 3-hydroxy-4-methoxyphenylacetic acid was oxidized to 3,4-dihydroxyphenylacetic acid but some increase in m-hydroxyphenylacetic acid excretion was observed. 5. 2-Phenylethanol analogues were largely converted to the corresponding acids. 3,4-Dihydroxyphenylethanol was partially m-O-methylated before oxidation. 6. beta-Phenylethylamine analogues were oxidized mainly to phenylacetic acids. but a variable amount of analogous phenylethanol was also formed, especially from m-tyramine. Dopamine was O-methylated, a process not readily reversible. It was also p-dehydroxylated following oral and intraperitoneal administration but not after oral neomycin; biliary excretion of amines may be involved in this sequence of events. N-Methylated amines were oxidized less readily than the parent amine. 7. Differences in route of administration resulted in quantitative changes in degradation pathways, an effect deriving, to some extent, from p-dehydroxylation and O-methylation in the gut.

Measurement and kinetic study of the formation of adrenaline sulphate in vitro

The sulpho-conjugation of [14C]adrenaline form inorganic sulphate and ATP or preformed adenosine 3'-phosphate 5'-sulphatophosphate was demonstrated in the high-speed supernatant prepared from the liver and small intestine of various animals. Hydrolysis with sulphatase indicated the sulphate nature of the conjugate. The overall sulphation reaction has a pH optimum of 9.0. Maximal activity was obtained with a ratio of ATP/Mg2+ of 1 at 4--6mM. Above their optimal concentrations, ATP and Mg2+, separately or in combination, were inhibitory. Dithiothreitol at 3 mM stimulated the reaction by about 30%. The Km for adrenaline, determined by the sulphotransferase reaction and by the three-step (sulphate-activating and sulphotransferase) reactions was 125 micrometer. The rate of synthesis of [14C]-adrenaline sulphate, expressed in pmol/min per mg of protein for the livers of dog, monkey, rat, guinea pig and rabbit were, respectively, 144, 77, 47, 11 and 6. The corresponding values for the small intestines of dog and monkey were 60 and 62. Brain and heart tissues showed no measurable activity.

Motor effect of dopamine on human sigmoid colon. Evidence for specific receptors

The effect of dopamine on human sigmoid motility has been studied in 26 subjects. To record mechanical activity of the sigmoid colon, two small, air-filled balloons mounted on a probe introduced through a sigmoidoscope were used. The recordings were made at a distance of 25 and 15 cm from the anal edge. Dopamine was infused for 10 min after a 30-min control infusion of physiologic solution. Mean amplitude, mean duration, mean frequency, percentage of motor activity, and motility index of the pressure waves were determined. The motor response to dopamine was characterized by an increased baseline pressure with phasic waves superimposed. Dopamine produced a significant response at the dose of 5 microgram/kg/min. Alpha and beta antagonizing agents failed to oppose the effect of dopamine, while anticholinergic drugs enhanced its motor action. These studies suggest that dopamine may stimulate the motor function of human large bowel through specific receptors.

Rapid semiautomated method for the differential determination of urinary catecholamines

A semiautomated method is presented for the determination of adrenaline and noradrenaline by a combination of the trihydroxyindole procedure for total catecholamines and a new procedure for the specific direct determination of adrenaline without interference from noradrenaline at physiological levels. This new procedure involves the reaction of adrenaline with alkaline thiosemicarbazide to produce a fluorophor of acceptable stability for use in automated procedures. Its structure is as yet unknown. The within-batch standard deviation for the trihydroxyindole and alkaline thiosemicarbazide procedures respectively were 0.005 mumol/24h at a concentration of 0.368 mumol/24h and 0.012 mumol/24h at a concentration of 0.133 mumol/24h. The between-batch standard deviations of the two procedures were respectively 0.018 mumol/24h at a concentration of 0.388 mumol/24h and 0.015 mumol/24h at a concentration of 0.111 mumol/24h. Normal ranges for urine are presented for 24 healthy ambulant laboratory staff. The total catecholamine concentration (calculated as adrenaline) was 0.452 +/- 0.069 mumol/24/ (SD), range 0.349-0.616 mumol/24h. Using the alkaline thiosemicarbazide procedure, the normal range which was determined for adrenaline was 0.100 +/- 0.054 mumol/24h, range 0.022-0.207 mumol/24h. Noradrenaline calculated by difference was 0.355 +/- 0.081 mumol/24h, range 0.195-0.497 mumol/24h.

Selective GLC determination of epinephrine, isoproterenol, and phenylephrine in pharmaceutical dosage forms

A simple, specific GLC analytical procedure for the quantitation of epinephrine, isoproterenol, and phenylephrine in commercial tablets, powders, inhalation solutions, ophthalmic and nasal drops, and injectable preparations is presented. Samples are taken to dryness where required, the dried residue is reacted with an appropriate trimethylsilylating reagent, and the derivatives are eluted from a methyl silicone column using temperature programming. Quantitation of the flame-ionization detector signal is achieved relative to the dibenzyl succinate internal standard by an electric integrator. The results obtained by applying the method to the analysis of each of the three drugs in several simulated decomposed mixtures were in good agreement with theoretical values, even at impurity levels of up to 80% by weight. When applied to commercial formulations, the procedure was feasible for tablets, powders, and solutions at drug concentrations of 0.2% or greater. The commonly incorporated buffering and antioxidant excipients did not interfere.

In vivo assessment of decarboxylase inhibition or potentiation: urinary dopamine and L-dopa output after L-dopa administration

In the L-Dopa treated rat, a decreased urinary output of free and conjugated dopamine and an increase in free and conjugated L-Dopa excretion after administration of decarboxylase-inhibiting drugs provide a good in vivo index of Dopa decarboxylase inhibition. With the exception of free dopamine output, which showed an equivocal change, these measurements appear to provide a good yardstick of decarboxylase status in man also. Using this approach, it was not possible to find any evidence of facilitation of decarboxylase action, in L-Dopa-treated parkinsonians given pyridoxine supplements, to account for the ability of this compound to neutralize the beneficial effect of L-Dopa.

A method for the estimation of 2-phenylethylamine in human urine by gas chromatography

A gas chromatographic procedure with flame ionisation detection has been developed to measure 2-phenylethylamine in human urine as the trifluoroacetyl derivative. The amine is purified by an ether extraction procedure and derivatised with trifluoroacetic anhydride. Quantification is obtained by comparing the peak height with that for an internal standard added to the urine before extraction. The normal 24-h excretion value for 2-phenylethylamine in human urine is found to be 6.8 +/- 2.9 mug (mean +/- S.D.).

Monoamine metabolites and related compounds in human amniotic fluid: assay by gas chromatography and gas chromatography-mass spectrometry

Some catecholamine metabolites and related compounds have been identified in amniotic fluid obtained by transabdominal amniocentesis at various stages of pregnancy, including 4-hydroxy-3-methoxymandelic acid, 4-hydroxy-3-methoxyphenylglycol, 4-hydroxy-3-methoxyphenylcetic acid, p-hydroxypheny lacetic acid, p-hydroxphenyllactic acid and N-benzoylglycine (hippuric acid). Analysis was by gas chromatography with electron capture detection and by gas chromatography-mass spectrometry. Two of these compounds were determined quantitatively, free 4-hydroxy-3-methoxphenylglycol and p-hydroxyphenllactic acid: the concentration of the former increased with advancing pregnancy and that of the latter tended to decrease. Conjugated 4-hydoxy-3-methoxyphenylglycol could not be determined with accuracy as appreciable amounts of the unconjugated compound were found in the snail extract used for enzymatic hydrolysis. Assay of 4-hydroxy-3-methoxyphenylglycol in amniotic fluid is likely to be of diagnostic importance in the prenatal diagnosis of congenital neuroblastoma. Although 4-hydroxy-3-methoxyphenylethanol, 3, 4-dihydroxymandelic acid and 3, 4-dihydroxyphenylacetic acid were specifically looked for in amniotic fluid, they could not be detected.

Quantitative determination of epinephrine and norepinephrine in the picogram range by flame ionization gas-liquid chromatography

A gas-liquid chromatographic method has been developed using the hydrogen flame detector to determine epinephrine (E) and norepinephrine (NE) in blood plasma, red blood cells, serum, and urine. The chromatographic method presents several advantages over other existing techniques. The derivatives enable separation of E and NE and are stable at room temperature with no signs of decomposition. The detection limit for the catecholamines with the hydrogen detector was approximately 0.1 pg. The catecholamines can be determined simultaneously from the same gas-liquid chromatogram. Purification of the catecholamines using the conventional procedure of chromatographing on alumina has been eliminated. With this gas chromatographic method, no by-products are formed that interfere with E and NE determinations. Dopamine, which constitutes the major source of interference in the commonly used fluorometric methods, does not interfere with the E and NE determinations. Norepinephrine and epinephrine values for several physiological fluids are given with the analysis expanded to include red blood cells, the contents of which have not been previously reported.