Objective To understand the characteristics of indoor PM2.5 pollution in residential houses in Guangzhou. Methods Indoor PM2.5 samples were collected in nine residential sites using mini-volume sampler in Guangzhou in summer (June to July, 2003). Mass concentration of PM2.5 and the organic carbon (OC) and elemental carbon (EC) levels in PM2.5 were measured. Results The average concentration of PM2.5 was (47.4?17.7) mg /m3, a relatively high concentration compared to the previous studies in other cities. The OC and EC concentrations in PM2.5 were (12.5?8.7) and (4.4?2.3) mg /m3 respectively. OC and EC counted for 24.6%?5.6% and 9.9%?4.8% in indoor PM2.5. However, it was estimated that OC mainly came from indoor sources and EC related well with outdoor sources, which conformed to the source investigation. Conclusion Cooking, smoking and outdoor sources are the prominent contributors to the indoor PM2.5 pollution. Housing conditions such as decoration and ventilation may affect the indoor PM2.5 level.

A novel method for simultaneous determination of 3 rat poisons ( tetramine, bromadiolone, brodifacoum) and 5 toxic alkaloids ( hyoscyamine, scopolamine, gelsemine, strychnine, brucine ) in toxic samples by dispersive liquid-liquid micro-extraction ( DLLME ) coupled with gas chromatography-mass spectrometry was established. A mixture extractant containing 100 μL trichloromethane and 600 μL methanol was injected into the prepared sample to form an emulsion and the extraction process was accomplished. After centrifuged at 8000 r/min for 5 min, the settled drop of trichloromethane solvent was transferred to a conical insert within a GC autosampler vessel, and analyzed by GC-MS. Factors affecting extraction efficiency such as the type and volume of extractant, dispersive agent, extraction time, pH value and salt concentration of extraction system were studied. The limits of detection(LODs) were from 0. 003 to 1 μg/L in water sample, urine sample and rice wine sample. LODs were from 0. 002 to 0. 2 μg/kg in rice sample. The recoveries of toxic samples were in the range of 81. 0%-110%. The relative standard deviations( RSDs) were lower than 7%. The proposed method was sensitive, effective, and suitable for the simultaneous determination of toxic alkaloids and rat poisons in food poisoning sample.