Why dilute samples

Vacuum or positive pressure for processing samples: what's best? This means that the bigger particulates are being filtered out of the sample, which leads to a cleaner sample and a cleaner LC column. For urine samples, if hydrolysis is necessary, you add your sample, enzyme, hydrolysis buffer, and internal standard and incubate the sample incubation time varies depending on the enzyme that you use.

Urine hydrolysis: how to choose which enzyme to use? Just remember, when you dilute your sample with water, your area counts for your analytes of interest will be lower.

However, the samples are cleaner than they would have been without the dilution or in a dilute-and-shoot method. Do you want to know more about sample preparation techniques? There is no need to centrifuge the sample to get rid of any particulates, nor is there a sample transfer step.

Topics: Extraction method optimization , Sample preparation , Method development. The accuracy ratio is an average of the concentration of the diluted column compared to the previous column—a perfect serial dilution has an accuracy ratio of The accuracy ratio of the plate improved with more mix cycles, improving from While the precision and accuracy with 20 mix cycles is close to a perfect serial dilution, the length of time required might be considered impractical.

The mix cycle protocol required 20 minutes per plate, while a three-mix cycle protocol required less than six minutes. Efforts were then focused on the factors that could improve the three-mix cycle protocol to produce accuracy and precision results consistent with the mix cycle protocol. The mix tip height was modified in order to determine the effect of distributing the liquid at different locations in the well.

As the mix tip height was raised, the average precision improved. At a height of 3 mm from the bottom of the well, the average precision was 3. Accuracy tracked with precision, and the higher mix height also improved the accuracy ratio to 1. This trend is possible because the higher dispense height ensures that more of the sample was circulated by the mix cycle. In a mix roughly in the middle of the well volume, the dispensed liquid is forced toward the well bottom while dispensing, and aspirated liquid is pulled from the center of the well.

If the mix occurs close to the bottom of the plate, the dispensed liquid is pulled back into the tip during the aspiration. Mixing in the center allows the dispensed liquid to be more evenly distributed in the sample, thus increasing the likelihood of efficient mixing. The VWorks software controlling the Bravo platform allows the creation of liquid classes, which allows the operator to modify the velocity and acceleration for aspirating, dispensing, and mixing tasks.

Precision and accuracy improved as the mix velocity increased. The cause of this is likely due to the creation of more turbulent mixing, which in turn distributed the fluorescein dye more quickly throughout the solution. Finally, the effect of dynamic tip retraction and extension was explored. This function moved the tips deeper into the well during each aspirate step, and retracted them during each dispensing step. This allowed a larger volume of the well to be affected by the mix step by adding the movement of the tip into the mix task.

There was a marginal improvement less than 0. Additionally, no effect was observed by utilizing another mix standard, which involved aspirating close to the bottom of the well and dispensing near the top of the solution. This mixing method caused no improvement once the other parameters described above had been optimized. These experiments mixed homogenous solutions; there may be an improvement with this technique if the solutions are expected to have different viscosities.

This is where dilution saves the day. Not just dilution, but serial dilution… meaning dilution over and over again. Why do we dilute? To have fewer colonies to count and to obtain a more accurate count. Why do we do it repeatedly?