This application note provides information on specific application methods and the use of Hettich products. (more…) read more...
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The hematocrit value indicates the volumetric proportion of red blood cells in the blood. Centrifugation is the reference method for the determination of this value. It is used to separate the cellular components of the blood from the fluid ones and to package them tightly together. The reference method is described in DIN 58933-11). According to it, glass capillaries are centrifuged until the product of the minimum relative centrifugal force (RCF > 5000) acting on the erythrocytes and the numerical value for the centrifuging time in minutes is at least 100 000.
1. Hematocrit determination with standard capillaries
(a) Filling – When filling the capillary, take care not to wet the opposite end. For hematocrit determination, the capillaries are filled to approx. 75%.
(b) Sealing – Close the dry end of the capillary with sealing putty. To do this, push the capillary vertically into the sealing putty until its rim touches the sealing putty’s plate. Tilt it slightly and pull the capillary out of the putty.
(c) Centrifuging -Place the capillary with its closed end pointing outwards (towards the rim of the rotor) horizontally into the hematocrit rotor. Put the lid on the rotor.
(d) Determining the hematocrit value – Determine the hematocrit value with the evaluation disk, which is also the lid of the rotor.
The centrifuging time is calculated as follows: 100,000/RCF = time [min]
At an RCF of 20,000 the centrifuging time is: 100,000/20,000 = 5 min
2. Hematocrit determination with self-sealing capillaries
(a) Filling – Fill the capillary at its free end and let the blood column drop towards the stopper. The blood must make contact with the stopper!
(b) Sealing – Tap the capillary’s sealed end three times on the laboratory bench! This intensifies the contact between the blood and the stopper and furthers the sealing process. It is to make sure that the stoppers seal tightly!
(c) and (d) see section 1
3. Information on the different capillaries
Three kinds of capillaries are available. They differ in volume and diameter. For details, please see the table below.
|total volume without stopper (μl)||49.9||73.9|
|total length (mm)||75||75|
|contents when 75% filled (μl)||37.4||55.4|
4. Cleaning and disinfecting the hematocrit rotor
Not only when capillaries break (see section 5), but also when they leak, rotor and lid must be cleaned. Please proceed as follows:
5. Cleaning and disinfecting the hematocrit rotor after glass breakage
Because of the risk of injury, act with caution! To minimize the risk, we recommend wearing two pairs of gloves. Because of spraying glass splinters, also wear a face mask and goggles!
Do not reuse affected holding trays and sealing rings! It is almost impossible to remove glass splinters completely from these objects, and remaining splinters will bring about further glass breakage.
Hematocrit rotor, lid, holding trays and sealing rings cannot be autoclaved!
Hettich products are designed to help you achieve optimal results for your application and are built to perform to the specifications outlined in the operators manual. For application-specific information and settings, please refer to your organization’s standard operating procedure. As always, our Hettich representatives are here to help determine which Hettich products and accessories best fit your laboratory requirements.
Hettich manufactures centrifuges for any standard laboratory application.