Biomedical subjects

Chetan Shende

Publications and source records attributed to Chetan Shende.

2 recordsLinked to original sources

PubMed2003

Sol-gel poly(ethylene glycol) stationary phase for high-resolution capillary gas chromatography.

A sol-gel chemistry-based method was developed for the preparation of highly stable capillary gas chromatography (GC) columns with surface-bonded poly(ethylene glycol) (PEG) stationary phase. Through a single-step procedure, it concurrently provided column deactivation, stationary-phase coating, and chemical immobilization of the coated film. Sol-gel reactions were carried out within fused-silica capillaries that were filled with properly designed sol solutions containing two sol-gel precursors, two different triethoxysilyl-derivatized poly(ethylene glycol)s, two sol-gel catalysts, and a deactivation reagent. Hydrolytic polycondensation reactions led to the formation of a sol-gel coating chemically bonded to the inner walls of the capillary. A number of sol-gel coated fused-silica capillary columns were prepared using sol-gel-active PEG derivatives. These columns demonstrated many inherent advantages, the main being the strong anchoring of the coating to the capillary wall resulting from chemical bonding with the silanol groups on the fused-silica capillary inner surface. This chemical bonding yielded strongly immobilized PEG coatings with outstanding thermal stability (up to 320 degrees C). To our knowledge, such a high thermal stability has not been achieved so far on conventionally prepared PEG GC columns. Sol-gel PEG columns provided excellent chromatographic performances: high number of theoretical plates, excellent run-to-run and column-to-column reproducibility, and pronounced selectivity for a wide range of test solutes. Using n-octadecane as a test solute (k = 7.14), an efficiency value of 3200 theoretical plates/m was obtained on a 10 m x 0.25 mm i.d. fused-silica capillary column. Five sol-gel PEG columns provided RSD values of 1.09% for column efficiency (solute, n-octadecane), 1.37% for retention factor (solute, n-octadecane), and 0.9% for separation factor (for solute pair o- and p-xylene). In five replicate measurements using the same column, RSD values of less than 0.50% for the retention time and 1.36% for retention factor (k) were obtained.

Journal Article↗

PubMed2002

Sol-gel capillary microextraction.

Sol-gel capillary microextraction (sol-gel CME) is introduced as a viable solventless extraction technique for the preconcentration of trace analytes. To our knowledge, this is the first report on the use of sol-gel-coated capillaries in analytical microextraction. Sol-gel-coated capillaries were employed for the extraction and preconcentration of a wide variety of polar and nonpolar analytes. Two different types of sol-gel coatings were used for extraction: sol-gel poly(dimethylsiloxane) (PDMS) and sol-gel poly(ethylene glycol) (PEG). An in-house-assembled gravity-fed sample dispensing unit was used to perform the extraction. The analysis of the extracted analytes was performed by gas chromatography (GC). The extracted analytes were transferred to the GC column via thermal desorption. For this, the capillary with the extracted analytes was connected to the inlet end of the GC column using a two-way press-fit fused-silica connector housed inside the GC injection port. Desorption of the analytes from the extraction capillary was performed by rapid temperature programming (at 100 degrees C/min) of the GC injection port. The desorbed analytes were transported down the system by the helium flow and further focused at the inlet end of the GC column maintained at 30 degrees C. Sol-gel PDMS capillaries were used for the extraction of nonpolar and moderately polar compounds (polycyclic aromatic hydrocarbons, aldehydes, ketones), while sol-gel PEG capillaries were used for the extraction of polar compounds (alcohols, phenols, amines). The technique is characterized by excellent reproducibility. For both polar and nonpolar analytes, the run-to-run and capillary-to-capillary RSD values for GC peak areas remained under 6% and 4%, respectively. The technique also demonstrated excellent extraction sensitivity. Parts per quadrillion level detection limits were achieved by coupling sol-gel CME with GC-FID. The use of thicker sol-gel coatings and longer capillary segments of larger diameter (or capillaries with sol-gel monolithic beds) should lead to further enhancement of the extraction sensitivity.

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