Biomedical subjects

Luigi Nardi

Publications and source records attributed to Luigi Nardi.

5 recordsLinked to original sources

PubMed2003

Symmetrical (double-speed) static coating for high-resolution gas chromatography column preparation.

"Breakthrough" during static coating could be avoided using a new coating strategy: while filling the capillary support with coating solution, a short mercury plug was placed at the middle of the support length. Mercury was frozen by a cold source and vacuum was applied to both open ends. In this way static coating became symmetric and so evaporation rate was doubled, on a time base, and more than doubled on a coated length base. Coating time at room temperature varied from approximately 20 min for 3-m columns to approximately 3 h for 15-m columns.

Chromatography, Gas↗

PubMed2003

Determination of siloxane-water partition coefficients by capillary extraction-high-resolution gas chromatography study of aromatic solvents.

Partition coefficients of benzene, toluene, ethylbenzene and xylenes (BTEX), between crosslinked polydimethylsiloxane and water, were determined at room temperature by capillary extraction (a form of in-tube solid-phase microextraction, SPME) coupled to open tubular gas chromatography (in-tube SPME-high-resolution GC). A series of 7-9 repetitive extractions, performed on a 1-ml volume of diluted aqueous BTEX sample by the double-syringe squeeze method, gave exponential regression curves which fit very well with those predicted by partition theory. From the equations of the curves of relative FID response vs. extraction number, experimental Kd were easily calculated and the results compared with literature values. The whole measurement requires about 1 h from the start of the experiment to the final calculation of all BTEX partition coefficients. In-tube SPME resulted in a fast, clean, efficient, and cheaper alternative than the classic 1-cm, externally coated, SPME fiber-holder technique.

Chromatography, Gas↗

PubMed2003

Capillary extractors for "negligible depletion" sampling of benzene, toluene, ethylbenzene and xylenes by in-tube solid-phase microextraction.

The suitability of "capillary extractors" is demonstrated for the "negligible depletion" extraction of benzene, toluene, ethylbenzene and xylenes in a clean-water matrix. Extraction set-up and major extractor parameters (length, internal diameter, and film thickness) are chosen to allow rugged analysis by GC with flame ionization detection. With the selected negligible extraction conditions, the efficiency for every consecutive extraction is about 2-3% of the dissolved amount.

Benzene↗

PubMed2003

New high-performance cryofocalizer injector for in-tube solid-phase microextraction and headspace capillary gas chromatographic applications.

The construction of a high-efficiency but cheap injector for volatile and very volatile compounds is shown. The device focuses the compounds in a fused-silica (FS) transfer capillary with the aid of liquid nitrogen. A 6.2 mm O.D. glass tube liner (ca. 25 cm x 1.5 mm I.D.) is inserted in the heated (-200 degrees C) injector of the gas chromatograph in place of the standard glass liner, and extends further externally through a liquid nitrogen container made with styrofoam-like material. Inside this glass tube, the FS transfer line passing through the oven door is connected like a pre-column to the analytical high-resolution GC column. It can move fast between the heated and the cooled zone (<-->, deltaL = 13 cm), and when this movement starts, crvofocused analytes are injected "at once" resulting in symmetrical and sharp injection bands with "zero" carryover. The performance of this device is demonstrated by its application to in-tube solid-phase microextraction and to spice volatiles analysis.

Chromatography, Gas↗

PubMed2003

In-tube solid-phase microextraction sampler for long-term storage.

Capillary extractors are proposed as samplers-preconcentrators to overcome losses of volatile organic compounds found using "classical" solid-phase microextraction fiber-holder samplers. A set of equal-size extractors was used to extract in-tube an aqueous solution of benzene, toluene, ethylbenzene and xylenes (BTEX) at 146 ppb. After storage for 6-30 days at 0-4 degrees C (or -15 degrees C) GC analyses were carried out to study BTEX recovery. Results demonstrated that sample preservation was very good: recovery was higher than 98% after 6 days, and more than 95% after 30 days. Capillary extractors, due to their high performance in preserving sample integrity, represent a real breakthrough for on-site sampling of volatile compounds by solid-phase pre-concentration techniques.

Chromatography, Gas↗