Two of the most common loading methods are a liquid sample loading and dry sample loading. Herein we briefly describe methods for both liquid and dry loading and how to choose.
Liquid Loading
Liquid loading is usually the preferred method of loading as it requires less work. You can use this method of loading if your compound is:
- Highly soluble in a wide range of solvents
- If it is already a liquid or oil that can be diluted
- Your loading is typically 1% or less
While it may be preferred in most cases, it is not necessarily the best option. One other option is to dry load your compound onto a chromatography column.
Dry or solid loading
Dry loading is the process of taking a sample dissolved in a solvent and to adsorb it to a stationary phase.
Dry loading is an excellent approach when:
- Solubility of your compound is low
- The starting conditions of the mobile phase gradient are less polar than the sample dissolution solvent.
- High loading scenarios (typically greater than 1%)
- If you have observed low resolution or peak tailing with liquid loading, especially for samples with low solubility in your elution method.
One of the easiest ways to know if dry loading is a better option, is when you observe poor separation with liquid loading. While some of this can be attributed to sample dilution, it is not the only reason. Some chemists prefer to use the same stationary phase the main column is packed with for dry loading to maintain the same chemistry of the column.
If those interactions are unimportant or unnecessary, diatomaceous earth or Celite can be used instead. Celite provides for minimal sample adsorption and is typically much less expensive than silica or other stationary phases. With Celite the sample moves through rapidly, concentrates, and forms a much narrower band at the top of the column. Alumina and Florisiltm are also alternative matrices that can be utilized.
The most common method of dry loading a sample is to determine what quantity of sample you want to load, and dissolve your sample in a solvent it is readily solubilized in. Decant the new solution into a round bottom flask and add the appropriate amount of stationary phase (2-3 times the mass of the dry compound) to the flask.
Swirl or stir the flask gently to ensure all the silica is fully suspended within the solution.
Using a rotary evaporator, gently evaporate the solvent until the silica is dry and free flowing. .
The sample matrix is then either loaded into an empty flash column or loaded into the top of a partially packed flash column.
Although liquid loading a sample is less labor intensive, dry loading can improve your chromatography dramatically, dependent of course on your sample’s characteristics.
Use our Sorbtech EZ Flash Empty Columns for Dry Loading your Sample
- Suitable for use as a solid load injection column
- Capable of assembling multiple cartridges in series
- Components: screw cap with disbursing unit, frits, O-ring and end tips
- Replacement frits and O-rings are available
- Available in 10 sizes from 4 gm to 330 gm packing volume
Our Sepabean Semi-Automated Flash System is a semi-automated instrument that allows for use of either liquid or dry sample loading and can be designated within the method directly.
This capabilities of the Sepabean go far beyond this important characteristic, find many of the other advantages demonstrated below.
- Wireless Operation Through Mobile Devices
The flexible wireless control method is especially suitable for separation experiments that need to be protected from light or placed in an isolator. - Power Failure Recovery
The built-in power-off recovery function in the software minimizes the loss caused by unexpected power failures. - Separation Method Recommendation
The software has a built-in separation method database that automatically recommends the most appropriate separation method based on the key information entered by the user, thereby improving work efficiency. - Fraction Collector
Tube racks with LCD display enable users to easily track the tubes containing collected fractions. - Local Network Data Sharing
Multiple instruments can form a local area network to facilitate internal data sharing and resource optimization in the laboratory. - 21-CFR Part 11 Compliance
The control software complies with FDA requirements for system safety (21-CFR Part 11), making the instrument more suitable for pharmaceutical R&D companies and laboratories. - Smart purification system makes the purification easier
This smart flash chromatography system has a built-in feature of separation method recommendations. This feature empowers a new user to immediately utilize the instrument with results much like an expert chromatographer - Smart purification with “Touch & GO” simplicity
We have simplified the UI (user interface) to be simple, direct, and understandable with minimal training so all users, regardless of experience, can complete routine to the most complex separations easily and immediately.