Entrapment of horseradish peroxidase in sugar-modified silica monoliths: toward the development of a biocatalytic sensor.

A miniaturized HRP-entrapped bioreactor was prepared by a one-step enzyme immobilization method using a biocompatible sol-gel processing method employing either diglycerylsilane (DGS) or sodium silicate (SS) as precursors and a covalently tethered sugar, N-(3-triethoxysilylpropyl)gluconamide (GLS) as a silica modifier. Factors such as leaching, catalytic efficiency and long-term stability were examined to assess the role of the precursor and modifier in influencing enzyme performance. The results showed that sodium silicate derived materials modified with covalently bound sugars at a level of 10 mol% were optically transparent and provided the highest catalytic turnover rate for entrapped HRP. The stability and reusability of the entrapped HRP was found to be satisfactory for at least 1 month in the GLS-doped SS materials, and the entrapped HRP was able to respond linearly to the presence of peroxide over the concentration range of 0-750 microM with a detection limit of 6 microM, demonstrating the potential of this material for the development of a reusable optical biosensor.

Determination of volatile organic compounds in workplace air by multisorbent adsorption/thermal desorption-GC/MS.

Investigation of volatile organic compounds (VOCs) was first conducted in the air of class-100 cleanrooms at liquid crystal display (LCD) fabrication facilities. Air samples were collected on multisorbent tubes (including Carbopack B, Carbopack C, and Carbosieve S-III) and analyzed using adsorption/thermal desorption coupled with gas chromatography-mass spectrometry (GC-MS). Optimal conditions lead to average recoveries in the range of 96.2-98.2%, and method detection limits between 0.38 and 0.78 ppb, under the condition of 1-l sampling volume and 80% relative humidity. The method appears to be accurate, sensitive, simple and well-suited for determining VOC distributions from various stages of LCD manufacturing process and temporal variations of the analyte concentrations. About 15 VOCs were identified in workplace air. The major pollutants such as propylene glycol methyl ether acetate (PGMEA), butyl acetate, and acetone that are commonly used in the opto-electronics industry were detected and accurately quantified with the established method.