Mathematical functions for the representation of chromatographic peaks.

About ninety empirical functions for the representation of chromatographic peaks have been collected and tabulated. The table, based on almost 200 references, reports for every function: (1) the most used name; (2) the most convenient equation, with the existence intervals for the adjustable parameters and for the independent variable; (3) the applications; (4) the mathematical properties, in relation to the possible applications. The list includes also equations originally proposed to represent peaks obtained in other analytical techniques (e.g. in spectroscopy), which in many instances have proved useful in representing chromatographic peaks as well; the built-in functions employed in some commercial peak-fitting software packages were included, too. Some of the most important chromatographic functions, i.e. the Exponentially Modified Gaussian, the Poisson, the Log-normal, the Edgeworth/Cramér series and the Gram/Charlier series, have been reviewed and commented in more detail.

New possible chelating agents of clinical interest for iron(III): 2-hydroxynicotinic acid and 3-hydroxypicolinic acid. A thermodynamic study.

The formation of complexes between iron(III) and two ligands of possible relevance to chelation therapy, 2-hydroxynicotinic acid and 3-hydroxypicolinic acid, in aqueous 0.6 m (Na)Cl at 25 degrees C, has been investigated by means of potentiometric titrations and UV measurements. In both cases several mononuclear complexes and their deprotonation products are formed.

Direct determination of t,t-muconic acid in human urine by two-dimensional liquid chromatography.

The accurate determination of E,E-2,4-hexadiendioic acid (t,t-muconic acid), an important urinary biomarker of benzene exposure, is directly performed in human urine by a new two-dimensional liquid chromatographic method. After a first partial separation of urine components by a reversed-phase mechanism and the focalisation of the anionic analytes on a small anion-chromatographic column, a conventional ion-chromatographic analysis with UV detection is carried out. The analytical procedure is fully controlled by the HPLC instrumentation software using an eight-port switch valve. If compared with conventional one-dimensional procedures, the new method produces chromatograms containing a limited number of well resolved peaks and consequently allows better analytical performances: no interfering peaks, absence of bias, repeatability better than 5% in the concentration range 0.09-5 mg dm-3 and a detection limit of 4.0 micrograms dm-3 (alpha = beta = 0.05) for the analysis of real samples.

Potentiometric characterization of weak acids by multiple sample addition II. The effect of chemical interferences and the practical performance of linearization methods.

Potentiometric multiple addition of a sample containing a pure weak acid to a solution of supporting electrolyte has been previously shown [C. Maccà and A. Merkoci, Talanta, 41 (1994) 2033] to be formally suitable for the determination of the dissociation constant and concentration of the sample acid. Linear equations have been developed for the treatment of experimental data to yield, simultaneously or separately, the chemical parameters of the acid solution. These equations are now tested on real samples together with analogous equations for titrations, and the results are compared with those obtained with rigorous statistical methods. For the determination of the acidity constant with samples of known concentration, multiple samples addition is comparable with titration. When the sample concentration is unknown and must be determined simultaneously to the acidity constant, the results obtained by linearized multiple sample addition can be seriously affected by impurities present, even at low level, either in the sample or in the supporting solution. Linear equations accounting for the effects of basic or acidic impurities in the sample or in the supporting solution are developed. Sample addition is confirmed to be a useful complement to pH-metric titration for the determination of acidity constants of moderately weak acids by non-linear regression; linearization of data is a convenient technique for screening purposes and a powerful means of detecting and correcting some common pitfalls, interferences and contaminations, whose effects are enhanced in linearized sample addition.

Experimental aluminum pathology in rabbits: effects of hydrophilic and lipophilic compounds.

Aluminum lactate [Al(lact)3] (hydrophilic, hydrolytically unstable) and aluminum acetylacetonate [Al(acae)3] (lipophilic, hydrolytically stable) were tested as potential toxicants to rabbits upon IV administration both as aqueous solutions and as liposome suspensions. Both chemicals behaved as cardiotoxic agents when administered as aqueous solutions, but Al(acae)3 was at least two orders of magnitude more active than Al(lact)3. Al(acae)3, but not Al(lact)3, caused myocardial infarcts resembling those in humans (with contraction bands) at doses as low as 0.24 mg/kg body weight, as well as a prominent acanthocytosis. Al(lact)3, when administered as a liposome suspension, was about 300 times more toxic than in aqueous solution, although cardiac damage was not infarctual in character. Both chemical and physical speciation of aluminum(III) thus play an essential role in determining the toxicity of the metal.

Cardiotoxicity of the lipophilic compound aluminum acetylacetonate in rabbits.

Aluminum acetylacetonate was administered to New Zealand white rabbits as liposome preparations and was found to distribute approximately 1:1 between water and phosphatidylcholine dipalmitoyl vesicles. Biochemical monitoring proved that after 2 weeks of daily injection of 40 micrograms of Al(III) in the above form, the animals developed significant signs of cardiac suffering, evidenced by variations in lactic dehydrogenase and creatinine phospokinase. Histopathologic investigation revealed that aluminum acetylacetonate caused unambiguous myocardial infarcts, characterized by myocardial contraction bands. In contrast, injection of Al(III) as a simple salt (lactate, 20 mg/day for 3 weeks) gave a less severe myocardiopathy, certainly not infarctual. Aluminum acetylacetonate given to rabbits appears to be, to our knowledge, the only chemical tool able to mimic spontaneous infarction situations in humans.

Alzheimer dementia and the aluminum hypothesis.

The possible involvement of environmental aluminum in the etiology of Alzheimer disease and of senile dementia of the Alzheimer type is supported by both direct and indirect relationships between some encephalopathies and the abnormal presence of aluminum(III) in human and animal brain tissues. Proposals for further biochemical, toxicological and analytical work are illustrated.

A neutral lipophilic compound of aluminum(III) as a cause of myocardial infarct in the rabbit.

Intravenous administration of aluminum(III) in the form of the hydrolytically stable and moderately lipophilic complex acetylacetonate in the rabbit a severe pathological picture, the most significant feature of which is the occurrence of a myocardial infarct.

Rubber manufacture: sampling and identification of volatile pollutants.

Volatile pollutants produced from several rubber goods manufacturing processes were sampled and analyzed. Samples were collected in the vulcanization areas of a shoe-sole factory, a tire retreading operation, and also in the extrusion areas of the retreading operation and an insulated cable manufacturer. Volatile organics from the vulcanization and extrusion operations were collected on activated charcoal, desorbed with trichlorofluoromethane and analyzed by GC/MS. Approximately 100 different compounds were identified and quantitated; their cumulative concentrations ranged from 25 to 27000 micrograms/cubic meter.

Purge and Trap analysis of toluene in blood: comparison with the Head Space method.

A procedure for the determination of toluene in blood by the Purge and Trap method is described. The method, which had not been previously employed for the determination of volatile organic substances in biological fluids, has a linear range which extends up to at least 1500 micrograms/L, and gives results in excellent agreement with the conventional Head Space method; the detection limit was not exactly determined, but is estimated to be less than 7.5 micrograms/L, much better than for the Head Space method. Using the Purge and Trap method, we have observed the accumulation of toluene in the blood of experimental subjects as a result of a weekly exposure to toluene.