A computer-based trigger system for a laser induced plasma spectrometer

A computer-based trigger system making use of the IBM PC/AT printer port is devised for a laser induced plasma spectrometer. This system synchronizes the generation of photon pulses from an excimer laser and the data capture of emission spectra by a spectrometer. The LIP spectrometer thus devised has been applied successfully to detect weak emission signals from the iodine atom of selected chemicals.     

Preparation of water-soluble chitosan from shrimp shell and its antibacterial activity

Crude chitosan was prepared from shrimp shell by HCl, NaOH and ethanol solution successively. Hydrogen peroxide was used to degrade the crude chitosan into water-soluble chitosan. A mathematical model between degradation conditions (H₂O₂ level, time and temperature) and the recovery of water-soluble chitosan was constructed using response surface methodology. Each factor showed a significant effect on the recovery. The model was confirmed to have a good fitness by analysis of variance. The optimal conditions to obtain the highest recovery of water-soluble chitosan were 5.5% of H₂O₂ level, 3.5 h of time and 42.8 °C of temperature. The predicted recovery was 93.5%. Through testing the number of colony, both crude and water-soluble chitosan showed good inhibition activities against B. subtilis. By determination of inhibition zone diameter, water-soluble chitosan showed significantly (P < 0.05) higher inhibition capabilities against E. coli, B. subtilis and S. aureus than crude chitosan.Industrial relevanceChitin is the second abundant polymer next to cellulose over the world. Its deacetylated product, chitosan, is an important ingredient in medicine and food. However, the low solubility in water limits the application of chitosan. In this work, the chitosan was degraded by H₂O₂ to produce water-soluble chitosan. Response surface methodology was taken to construct a model between degradation conditions and the recovery of water-soluble chitosan. By determination of the antibacterial activity, water-soluble chitosan showed better antibacterial activity than crude chitosan without degradation treatment. The results indicated the high potential of water-soluble chitosan as an antibacterial agent. This work was helpful for applying this product in industry.