G. V. Melzi d'Eril

Determination of illicit drugs and related substances by high-performance liquid chromatography with an electrochemical coulometric-array detector

A general method for the simultaneous determination of fifteen common drugs (6-acetylmorphine, 3,4-methylenedioxymetamphetamine, buprenorphin, cocaine, codeine, dihydrocodeine, ethylmorphine, heroin, hydrocodone, lidocaine, methadone, morphine, naloxone, procaine and thebaine) was developed using reversed-phase HPLC and electrochemical detection. The separation of the drugs was achieved by using as the mobile phase 20 mM monobasic sodium phosphate-acetonitrile (90:10) with a gradient to 50% of the organic modifier, on a silica based C18 column (150 x 4.6 mm I.D.) of 3 microns particle size and by the selectivity supplied by an array of eight coulometric electrodes at increasing potential. It was possible to identify and to determine fifteen different drugs in the same chromatographic run in 50 min. The method was tentatively applied to the determination of drugs in extracts of human hair.

Reference values of neuroactive amino acids in the cerebrospinal fluid by high-performance liquid chromatography with electrochemical and fluorescence detection.

Sampling and HPLC analysis procedures for CSF amino acid determinations were evaluated. In order to increase sensitivity, a precolumn derivatization of amino acids by o-phthalaldehyde-mercaptoethanol reagent was used. By using fluorimetric and electrochemical detection in series, positive peak identification can be obtained in a single chromatographic run. It is recommended to analyze freshly collected CSF. Amino acids are stable for short periods over a wide range of temperature, but storage at -80 degrees C is recommended. The CSF samples for the calculation of the reference values were taken from 40 healthy subjects, hospitalized for lumbar disk herniation, placed on the same diet and kept drug-free for at least 1 week. The mean values (mumol/l) and the ranges (in parentheses) were: 0.27 (0.09-0.63), 0.62 (0.18-1.15), 5.32 (3.05-11.50), 6.16 (2.90-13.30), 0.16 (0.03-0.22) for aspartic acid, glutamic acid, glycine, taurine and gamma-aminobutyric acid respectively.

The influence of gender in the evaluation of platelet and plasma catecholamines

The platelet and plasma levels of catecholamines (CA) were simultaneously studied in a group of normal subjects in order to find possible sex-related changes in the distribution of CA in these two compartments. No significant differences between males and females were observed, but a marked platelet noradrenaline increase was found in the luteal phase as compared to the follicular phase. Furthermore, the platelet and plasma CA levels were strongly correlated in the male group but not in the female group. These results, while confirming the existence of a menstrual-related variability in noradrenergic activity, suggest a sex-related difference in the dynamic balance between platelet and plasma CA levels. The simultaneous assay of platelet and plasma CA enabled this phenomenon to be revealed, whereas the separate evaluation of platelet or plasma CA levels would not have done so.

Determination of free DOPA and 3-O-methyl-DOPA in human plasma by high-performance liquid chromatography with electrochemical detection

A procedure was devised for the determination of the unconjugated non-protein-bound fraction of 3,4-dihydroxyphenylalanine (DOPA) and 3-O-methyl-DOPA (3-OMD) in plasma using a reversed-phase liquid chromatographic system coupled with electrochemical detection. Sample preparation involves rapid isolation of the unbound drugs from the drug-protein complex by ultrafiltration through a membrane with a molecular weight cut-off of 10,000 dalton. One chromatographic run requires less than 10 min. The relative standard deviation is less than 3% for the within-assay imprecision and less than 4% for the between-assay imprecision. The detection limits for DOPA and 3-OMD are 0.2 and 1.3 ng/ml, respectively.

Improved HPLC methodology in occupational exposure studies on formaldehyde

SummaryThis work describes an HPLC method for the determination of formaldehyde concentration in air. Traps containing 20–40 mesh silica gel coated with 2,4-dinitrophenylhydrazine (DNPH) are used. After aspiration of air the traps are eluted with methanol. The hydrazone formed is then separated on a C18 column using a mobile phase of methanolwater (50–50 v/v). The effluent is monitored with a UV detector at 365 nm.To calibrate and to compare this method with that of Niosh 2502 (traps coated with 2 benzylamino ethanol on Chromosorb 102), a mixing chamber that generated atmospheres of known concentration of formaldehyde was used.

Effects of malnutrition on the acute phase response of plasma proteins in patients undergoing total gastrectomy

The serum level of six acute phase proteins (APP) has been evaluated preoperatively and for a few days in the postoperative period. Thirty patients undergoing total gastrectomy for gastric cancer have been studied in two subgroups according to their nutritional status. Those with gastric cancer had significantly higher baseline serum levels of alpha 1 acid glycoprotein (alpha1AGP) and C-reactive protein (CRP) than a control group. Malnourished patients also had reduced acute phase response for alpha1AGP and alpha 1 antitrypsin (alpha1AT) a higher increase of CRP and fibrinogen, and a lower decrease for transferrin and retinol binding protein (RBP).

Evaluation of a modified Marcali technique with high performance liquid chromatography—ultraviolet detection for the determination of 2,4-toluene diisocyanate in air

Abstract This work describes an method for the determination of 2,4-toluene diisocyanate concentration in air. Traps containing 20–40 mesh silica gel coated with phosphoric acid are used. After the aspiration of air, sodium hydroxide is added to the silica gel, which is subsequently eluted with methanol. The amine formed is then separated on a C 18 column using a mobile phase of phosphate buffer— methanol (60:40, v/v). This can be performed in less than 4 min. The effluent is monitored with a UV detector at 235 nm. The detection limit based on a 20-1 air sample is 0.2 μg/m 3 . Complete analysis requires about 30 min.

Isoelectric focusing herpes simplex virus-gB overlay study in brainstem encephalitis

Abstract We report a case of herpetic brainstem encephalitis (HBE) retrospectively diagnosed in an adult patient. Conventional immunovirological studies failed to disclose the etiology of this patients affection. An isoelectric focusing‐antigen overlay (IEF‐O) technique showed that the target of one of the four cerebrospinal fluid oligoclonal bands was herpes simplex virus (HSV)‐1 glycoprotein B, indicating a specific anti‐HSV immunoresponse restricted to the CNS. IEF‐O may represent a useful support for in vivo diagnosis of HBE.

Simultaneous assay of platelet and plasma catecholamines by HPLC with coulometric detection

SummaryPlatelets and monoaminergic neurons share many morphological, biochemical, and pharmacological properties. In addition to its similarities to serotonergic nerve endings, the platelet has also been considered a good model for the study of the noradrenergic function, since it can selectively take up, store, and release norepinephrine (NE).In this study platelet and plasma levels of free catecholamines (CA) in 20 healthy subjects have been determined by HPLC with a reversed phase (C18) ionpairing system equipped with a coulometric detector. Direct correlation was observed between platelet and plasma levels of NE. A positive correlation was also found between the age of the sujects and both platelet and plasma NE levels.While showing that the peripheral noradrenergic hyperactivity of the elderly is also reflected in platelet NE content, this study also demonstrates that simultaneous assay of platelet and plasma CAs can be a useful tool for an integrated and more complete evaluation of sympathetic nervous system activity.

Haemodynamic and neurohormonal responsiveness to different stress tests in mitral valve prolapse

In this study the blood pressure, heart rate, plasma noradrenaline and plasma adrenaline responses to various forms of sympatho—neural stress were evaluated in patients with mitral valve prolapse (MVP). Sympathetic reactivity in different subgroups of MVP were related to the degree of ventricular arrhythmia. Thirty—eight patients with mitral valve prolapse and 17 healthy controls were studied. All underwent 24-h ECG recording, 2-D echocardiography, head-up tilt to 60°, pressor tests (sustained handgrip, mental arithmetic, cold pressor) and psychological assessment. The blood pressure, noradrenaline and adrenaline response to stress in patients without premature ventricular contraction were similar to those of the controls. In patients with unifocal premature ventricular contraction (PVC) less than 300/h, responses were similar to normal but were associated with higher plasma noradrenaline levels in the basal state and a diminished response to isometric stress. In patients with more than 300/h unifocal premature ventricular contraction, pairs of premature ventricular contraction, or runs of ventricular tachycardia there were lower blood pressure values in the basal state with reduced blood pressure, heart rate and plasma noradrenaline and adrenaline responses to head-up tilt and sustained handgrip, but marked increases in blood pressure, heart rate and plasma noradrenaline levels during the cold pressor test. Our data suggest different degrees of autonomic involvement in mitral valve prolapse which may be related to the various degrees of arrhythmia which seem to contribute to their symptoms.