The Hermle refrigerated centrifuge line, manufactured by Progen Scientific Ltd., is one of the most useful currently available. It occupies less space and generates very little sound during use than other similar models. The centrifuge is provided with two rotors, one that can hold twenty four 1.5 ml tubes (maximum speed of 15,000 rpm) and the other that can hold six 30 ml tubes (maximum speed of 12,000 rpm). The speed can be changed in increments of 250 rpm. The high speeds are useful for routine molecular biology work, including DNA and protein preparations. In addition, the machine has a good acceleration rate, taking less than 20 sec to reach 15,000 rpm.
The centrifuge has a temperature range of –10 to 40 C that can be changed in 1 degree increments. The refrigeration is extremely fast, taking less than 10 min for a decrease in temperature from 30 to 4 C. The timer on the machine can be set for a maximum of 59 min or alternately, the machine can be left “on hold” for as long as required.
Mechanically, the machine has several useful features that add on to its longevity. A characteristic worth mentioning is the automatic shutdown of refrigeration when the centrifuge lid is open. Also, the cooling fan is switched off when the machine remains idle for over 5 min. The minimum spin speed for either rotor is 250 rpm and we generally exploit this feature for cooling prior to running samples. Additionally, this feature can be useful while centrifuging cells with thin membranes that need to be handled delicately. We occasionally find this feature handy for separating cell aggregates.
Another good feature is that, unlike several other competitors, the timer starts only when the set speed is attained. Perhaps the most advantageous characteristic of this machine is that all parameters, especially speed, time and temperature, can be changed at any time during a given run, even when the run is in progress. An emergency lid opening system is also provided in the instrument, useful in the event of any unanticipated problems, such as a power failure. The features mentioned make the machine stable, as well as, highly desirable over most competitors for molecular and cell biology research. It is available only in one color (white) much to the disappointment of several people. We hope that a wide range of color choices will be made available eventually.
The only drawback with this instrument is the humming sound made by the cooling fan when the machine is in operation. Compared to several other centrifuges, however, it would be appropriate to say that this machine is rather quiet.
Vikas Jain
Research Scholar
Indian Institute of Science
India