Arnaldo Liberti

Graphitized carbon black in polyethylene as an electrochemical sensor

Abstract The electrochemical behaviour of a material obtained by moulding graphitized carbon black and polyethylene at 100–150°C is described. The material can be used as a pellet electrode in voltammetric procedures. As a tubular anode held in a teflon body, the material is valuable as a sensor for high-performance liquid chromatography. Its properties are comparable with those of glassy carbon with better signal-to-noise ratios. It is applied for the determination of several phenols, chlorophenols and hydroquinone in the low mg l−1 range or less.

Rapid determination of chlorinated pesticides using CN-bonded cartridges followed by GC-ECD

SummaryGas chromatography of chlorinated pesticides in water is carried out after adsorption of a 50 mL sample using a cartridge containing 100 mg CN-bonded porous silica and extraction with 500 μL pentane. The average recovery for eight organochloride pesticides at 1 ppb was >95%. The procedure described is simple, selective and reproducible.

Determination of indican and tryptophan in normal and uraemic patients by high-performance liquid chromatography with a new electrochemical detector

A simple analytical procedure has been developed for the determination of indican and tryptophan in biological fluids by reversed-phase liquid chromatography using a new electrochemical detector consisting of a tubular anode obtained by moulding graphitized carbon black and polyethylene. The hydrodynamic voltammetry of these compounds has been carried out and it has been found that, by operating in isocratic conditions with phosphate buffer (pH 4.0)-methanol (93:7), the reported compounds can be determined directly. The procedure can be applied for the determination of the free compounds on ultrafiltered serum as well as of their total content on serum deproteinized with methanol. Levels of both compounds in normal and uraemic patients have been measured and the relative ratios between free and total content yield a useful marker for patients with renal disease. The limits of quantitation of indican and tryptophan in serum were 5 and 10 ng/ml, respectively. The within-day assay coefficient of variation for total indican and tryptophan ranged from 3.0 to 3.6% and from 3.8 to 4.1%, respectively. The day-to-day assay coefficient of variation for total indican and tryptophan ranged from 3.4 to 3.7% and from 4.6 to 5.0%, respectively.

Routine determination of polycyclic aromatic hydrocarbons in carbon black by chromatographic techniques

A method is proposed for the determination of polycyclic aromatic hydrocarbons (PAHs) in carbon blacks. The PAHs are extracted from the carbon black with benzene in a Soxhlet apparatus, purified by silica gel thin-layer chromatography, weighed and analysed by gas and/or high-performance liquid chromatography. The total PAH and benzo[a]pyrene (BaP) concentrations in different types of carbon blacks and in different batches of the same carbon black were determined. It is shown that the distribution of the PAH fraction in different types of carbon blacks is almost the same but there are considerable differences in the total amount of the PAH fraction and the BaP concentration.

Development of porous-layer capillary columns

Abstract Procedures for preparing porous-layer capillary columns have been improved and their preparation with kaolin and graphitized carbon black coated with a variety of stationary phases is described. It is shown that an almost theoretical coverage can be achieved and that short columns with high efficiency can be realized. A number of separations (terpenes, essential oils, anilines, chlorocarbons, amines, alkylbenzenes isomers) are reported.

Chromatographic evaluation of perfusion on charcoal in uraemia

Chromatography on Bio-Gel P-2 and high-performance liquid chromatography on RP-18 columns monitored with UV, fluorescence and electrochemical detectors have been used to evaluate the efficiency of granular, uncoated, active charcoal to remove from the ultrafiltrates of uraemic patients those organic substances accumulated in the blood that are not easily removed by dialysis. Chromatography on Bio-Gel P-2 and high-performance liquid chromatography on RP-18 columns carried out isocratically and monitored with an electrochemical detector seem very useful for clinical investigation as they increase the information obtained from routine haematochemical analyses such as blood urea nitrogen, creatinine, uric acid and electrolytes (calcium, phosphorus, sodium and potassium).