A calorimetric system based on the LKB 10700-1 flow microcalorimeter

Abstract

An electrically calibrated and computer-controlled apparatus based on the LKB 10700-1 flow microcalorimeter was set up and tested by determining the enthalpies of dilution of aqueous solutions of sucrose and HCl at 298.15 K. The obtained results are in good agreement with the corresponding reference values recommended in the literature. The quality of the calorimetric signal in terms of noise, linearity and baseline drift, and the instrument time constant were analyzed. Also investigated were the influences of the flow rate and of the viscosity of the calorimetric liquid on the position of the baseline. The new calibration system enables powers ∼25 times smaller than those possible with the original one to be released inside the calorimetric cells. Electrical calibrations carried out with water as the sole calorimetric liquid indicated that the precision of the calibration constant, ε, quickly improved from ∼9% to ∼0.4% with the increase of the input power, P, from ∼2 µW to ∼50 µW, and stabilized at ∼0.1% for P ⩾ 100 µW. The calibration constant was also found to linearly increase with the flow rate of the calorimetric liquid and to vary by less than 1% over a period of eight months under similar experimental conditions. Finally a new experimental procedure for heat of dilution measurements, which combines calibration and experiment in a single run, was evaluated. This method allows a significant economy in experiment time with apparently no accuracy loss relative to the conventional procedure recommended in the literature.

Energetics of Aqueous Solutions of the Ionic Liquid 1-Ethyl-3-methylimidazolium Ethylsulfate

“…The electrically calibrated flow microcalorimeter used to obtain the enthalpies of dilution of aqueous [C 2 mim][EtSO 4 ] solutions and the selected experimental procedure (previously dubbed method 2) have been described elsewhere. 42 All experiments were carried out with the air thermostat and the prethermostat bath set to 298.15 and 280 K, respectively. Water and the ionic liquid solutions were driven into the calorimeter at flows in the range of 0.53-7.4 mg • s -1 , using an Ismatec MS-4/12 multichannel peristaltic pump.…”

The metabolic profile of lag and exponential phases ofSaccharomyces cerevisiaegrowth changes continuously

“…Calorimetric experiments were carried out with a previously described [14] LKB 10700-1 flow calorimeter operated in the flow-through mode. The original apparatus was, however, expanded with ancillary equipment for cell growth.…”

“…The nominal volume flow rate in the peristaltic pump was adjusted so that an actual flow rate q V = 1.0 mLmin -1 was achieved in all experiments. This adjustment was regularly checked as flow rate variations affect various calorimetric parameters, such as the calibration constant [14], the effective or thermal volume of the calorimetric vessel [14] or the signal sensitivity [15].…”

“…Electrical calibrations of the calorimetric system under the same conditions used in the main experiments (e.g. the pump flow rate, temperature) were performed as previously described [14]. No significant differences in the calibration constant, , were observed when millipore water, SC media or a culture of Sc in stationary growth phase were flown through the calorimetric cell.…”

Thermochemistry of aqueous pyridine-3-carboxylic acid (nicotinic acid)

“…The measurements were performed on a modified LKB 10700-1 flow microcalorimeter [18], with the air thermostat and the pre-thermostat baths set to T = 298.15 K and T = 280 K, respectively. The procedure essentially followed the previously denoted method 1 [18] which, in this case, involved the recording of a sequence of two measuring curves corresponding to the process under study and the electrical calibration, respectively. A general scheme of the two feeding configurations used at the different stages of the experiment is given in figure 2.…”