روزنامه با شماره پیاپی سال 2002

8

201

208

The heat flow signal from a differential scanning calorimeter (DSC) includes significant artifacts related to the instrumentation. They may be categorized as those due to imbalances in the instrument or those resulting from instrument heat capacity effects, commonly known as “smearing”. Imbalances cause instrument baseline defects that include offset, slope and curvature. Instrument heat capacity effects reduce the resolution of transitions and increase uncertainty when performing partial integrations of transitions. A new DSC heat flow measuring technique was developed that greatly reduces instrument baseline defects resulting from imbalances. It improves resolution and dynamic response by accounting for the instrument heat capacity effects. There are three components to the new heat flow measurement technique: (1) a new heat flow sensor assembly that has independent sample and reference calorimeters and incorporates two differential temperature measurements; (2) a more comprehensive heat flow measurement equation that includes calorimeter imbalances and differences in heating rates within the instrument and (3) a calorimetric calibration technique that characterizes the imbalances and enables the more comprehensive heat flow equation to be used. A DSC incorporating the new measurement displays a greatly improved instrument baseline and substantially improved resolution.

Food Microbiology

2002

Food Microbiology