The concentration of microparticles, including whole cells, bacteria, protozoa, fungi, molds, parasites, pollens, viruses, free DNA, and proteins is typically performed by either centrifugation or filtration, or combination. Both approaches have limitations on how large the starting sample volume can be and how small the final concentrate volume can be achieved.
For optimum detection of dilute organisms, a large sample volume paired with the smallest concentrate volume possible achieves the highest liquid to liquid concentration factor (LCF).
Efficiency, the percentage of target microparticles that are concentrated and recovered, is important too, but the combination of high efficiency plus a high LCF is what delivers the most target particles to the analytical device, kit, strip, etc. for optimum sensitivity.
1. Calculate the liquid-to-liquid concentration factor (LCF) i.e. starting sample volume (mL) divided by final concentrate volume (mL).
2. Multiply that figure by the percent recovery efficiency (%RE).
3. The result is the concentration factor (CF).
InnovaPrep’s FluidPrep™ Systems offer exponential concentration factors. They work by capturing dilute microparticles from large volumes of liquid using robust filtration on high surface-area filters, followed by instant recovery into a small final volume using our patented wet foam elution process.
The CP Select™ Concentrating Pipette can be used with sample volumes as large as 5 liters (depending on the pore size of the filtered pipette tip used), and delivers a final concentrate of about 250 microliters (µL).
The EasyElute™ Large Volume Concentration Kit can be used with sample volumes from 1 liter to 100+ liters. It delivers a final concentrate of about 70 milliliters (mL).
The following table shows potential concentration factors (CF) using the CP Select, the EasyElute LVC Kit, and a combination of both (for two-stage concentration). Examples are based on various sample input volumes and two example recovery efficiencies*.
* Efficiency is affected by a range of physical factors of both the matrix and the organisms. Efficiencies higher than 70% are common. For tips on optimizing recovery see the app note - Approaches for Improved Concentration of Microbes from Environmental Waters Using the Concentrating Pipette
· The CP Select is a superior method for concentration from volumes up to 10 L because of the smaller elution volume that is achievable.
· Sample volumes up to 10 liters can be split and concentrated on the CP Select using more than one pipette tip and then eluants combined.
· The EasyElute is the method of choice for concentration from volumes of 5-10 liters and up.
Matrix effects can influence all concentration processes, thereby limiting the volume of any sample that can be processed, meaning that while the example volumes demonstrated here may not be achievable in all instances, they can occasionally be exceeded.
