Heat capacity by multi-frequencies sawtooth modulation

In this paper a simple method is proposed to carry out temperature-modulate d calorimetry with multiple frequencies. The method is based on modulation with a complex sawtooth. The harmonics of the Fourier series of the measure d heat-how rate and temperature are used to extract data pertaining to the frequencies of the 1st, 3rd, 5th, 7th and 9th harmonic. The complex sawtoot h produces similar modulation amplitudes of the temperature of the first fo ur harmonics. In temperature-modulated differential scanning calorimetry wi th a period of less than about 150 s, corrections by extrapolation to zero frequency are commonly needed. With the proposed method, these extrapolatio ns can be done in a single experiment. Difficulties of baseline subtraction and other possible instrumentation and software problems are discussed. (C ) 2000 Elsevier Science B.V. All rights reserved.