The Blender is used to prepare homogenates or suspensions of semi-solid materials. The high-speed blades reduce samples to small particles by both a cutting and crushing action. Preparation of a homogenate is often the most practical way to handle samples that can not be ground in a Cyclone Sample Mill or other means to bring about homogeneity. The suspension of finely divided sample permits a much smaller weight of sample to be used without loss of accuracy due to the non-uniformity of the original sample.
The clear glass container used with the blender base permits observation of the sample during reduction. Excess blending time can, therefore, be eliminated. If the homogenate being prepared tends to separate out, this also can be observed so that precautions can be used.
Refer to the original Blender manufacturer's instructions for general operational information and safety reminders.
Always securely tighten the lid onto the container to prevent loss of solution or sample. Spillage prior to complete blending could alter the ratio of sample to solution enough to affect results.
Preparation of larger volumes of homogenate permits use of more sample to minimize sampling errors but lengthens the time required to achieve adequate sample reduction.
UDY procedures generally give recommendation for specific samples with practical sample sizes. When a homogenate is prepared, the amount of sample and liquid must be accurately measured. Typically, a one to nine ratio (10 fold dilution) is used when preparing homogenates. Only a move of the decimal point is then needed to change from composition of the homogenate to that of the original sample. The best way to measure out the sample and solution will vary with individual situations and the equipment available. When a certain sample size and volume of liquid are specified in a procedure, they may be varied if the same ratio is maintained or if a correction is applied. When solution is added by weight, it is convenient to measure out slightly less than the desired amount and then add the remaining portion from a dropper bottle. The container must be cleaned and dried between uses unless samples are very similar and the homogenate is not allowed to concentrate in the container.
Homogenates Commonly Prepared
not required if samples dissolve and mix easily.
The Syringe-Pipet is used to transfer preset volumes of fluid samples, homogenates of semi-solid samples and reconstituted or dissolved solid samples. When the sample density is constant, such as for fluid milk, the Syringe-Pipet is commonly used to eliminate sample weighing when maximum accuracy is not needed. When the sample density varies appreciable, such as for homogenates, the Syringe-Pipet constant volume delivery does not eliminate sample weighing, but provides a convenient sample handling and transfer tool. Vigorous pumping of the Syringe-Pipet expels air bubbles, helps to mix solutions and prevents settling and separation of the homogenate components.
Follow manufacturer's instructions.
Calibrate the Syringe-Pipet using water. the correct weight of water is calculated by multiplying the desired volume setting by the density of the water (0.997 @25oC or 0.998 @ 20oC). For example, if the setting desired is 2.00 ml, the syringe should dispense 2.00 x 0.997 g or 1.994 g H2) at 25oC. In many cases, the weight may vary 0.005 to 0.010 g without significant loss of accuracy. NOTE: 1 cc = approximately 1 ml.
When changing material being handled, a portion of the sample should be drawn into the Syringe-Pipet then discarded. This serves to rinse the Syringe-Pipet and to prevent sample dilution or alteration. Remove air bubbles by rapid by rapid short strokes (less than 1 ml). Watch for air bubbles, and be sure to eliminate them. Wipe cannula off before dispensing sample, but be careful not to draw liquid from inside the needed by capillary action.
Use a significant rate of expelling samples The volume of liquid expelled will vary significantly with the expulsion rate. Repeatable, consistent weight dispensed indicates that good technique is being used.
Whenever the Syringe-Pipet is not going to be used for awhile, rinse it with water and leave it filled with water.