A full line of advanced sample preparation and handling tools available.
Chromatography and particularly LC-MS requires “clean” samples and solvent prior to processing. We provide a range of tools for effective samples and solvent preparation.
a. Which Sample Preparation Techniques should I use?
1. Dilute and Inject
The sample is diluted with an appropriate solvent and directly injected into LC-MS. It is a fast and low cost strategy and useful only for very light contaminated samples e.g. Surface Water Analytics. MS supplier argue that moving to HRMS or uHRMS combined D & I is the convenient way to chose. Problems can often be solved with simpler MS in combination with sample enrichment. We don’t recommend this strategy because it ignores sample clean up. Matrix contamination can turn out to become very expensive and cumbersome. Solvent volatilisation is like matrix contamination also cumbersome.
2. Precipitate & Inject
The sample is treated with a solvent or a reagent that causes physical precipitation of the unwanted contamination. It is a fast and low cost technique often used for plasma samples . For protein precipitation you may just add Acids e.g. TCA 10%(w/v) and HClO4 6%(w/v) or just add a three fold excess of Acetonitrile. Sometimes you may have to add some additional small quantity of Zinc Sulfate to assist precipitation. The mixture is centrifuged and the supernatant injected.
3. Flash Chromatography click
There is a broad range of “automated” or manual Flash chromatography systems in the market. Most utilized dry packed cartridges or traditional glass columns packed with irregular silica or reverse phase materials. Some pack their own columns / cartridges, some procure dry packing equipment and some procure sealed cartridges. Flash Chromatography is mainly used in organic synthesis and medicinal chemistry. In biotechnology sometimes cartridges are used packed with polymeric ion-exchanger and RP material. Discuss this technology with us we offer 20 years experience.
4. Syringe Filters (Sterile / non sterile) click
For removal of micro and some nano particles from aqueous or solvent based media. The most popular pore size is 0.45 μm and 0.22 μm diameter. Wide range of filter diameters and packed with hydrophilic and hydrophobic membrane filters. Sometimes also used for separating polar apolar solvents from each other.
5. Extraction with Solvents
Very old and traditional method used since many years to extract compounds from plants, plasticiser from polymers, impurities from compounds etc. The material to be extracted is brought in contact with the extracting solvent either by Percolation or reflux in e.g a Soxhlet or under pressure in a Super Critical Fluid Extractor (SFE). Most solvents extract unwanted materials that have to be removed downstream. There is a practical book for extraction methods for specific Phytochemical groups.(Laboratory Handbook for the Fractionation of Natural Extracts, Peter J. Houghton, Chapman & Hall, ISBN 0 412 74910 6)
6. Liquid / Liquid extraction (LLE)
Liquid Liquid Extraction is also a old well know method but gained popularity due to better understanding of solvent properties. Any solvent could be used but most extract too many different compounds that have to be removed before further processing. Popular is MTBE (methyl - tert - butyl ether) because it is insoluble in water. Extraction is enhanced by manipulating the pH so that the analye is neutral and thus soluble in organic solvents. This way it will partition into the organic solvent. The general thought is to move about 2 pH units above or below the pKa. The following rules apply: Bases pH < pKa = R-NH3+ ionised, pH > pKa = R-NH2 unionised. Acids: pH < pKa = R-COOH unionised, pH > pKa = R-COO-ionised. Dont hesitate to contact us for help.
7. Supported Liquid Extraction (SLE)
Solid-supported liquid-liquid extraction sometimes also referred to as solid – liquid extraction or SLE, Comprises of a chemically inert, high - surface-area, highly purified, graded diatomaceous earth that serves as a stationary vehicle for the aqueous phase. Water easily adsorbs onto the surface of the diatomaceous earth particles. diatomaceous earth is packed into cartridges Aqueous samples such as serum, whole blood and urine, or environmental, food, or consumer products are diluted and pored over the diatomaceous earth. After 10 to 15 minutes distribution and wetting time an immiscible solvent is added to perform the extraction, resulting in a clean extract. SLE offers advantages over standard liquid-liquid extraction methods, including support for automation for high throughput, and better recoveries and precision by removing issues with emulsions that are often formed when performing liquid-liquid extraction. Because the aqueous sample has been widely dispersed throughout the solid support, the organic solvent has intimate contact with the thin film of aqueous phase and rapid extraction (equilibration) occur. A phase-separation filter is incorporated into the outlet frit of the of the cartridge to ensure that organic effluents remain uncontaminated by aqueous matrix. The experiments are more reproducible than in LLE. The entire SLE process is easier to automate than traditional LLE. The 96-well plate SLE format is especially amenable to automation using xyz robotics systems. Pre-packed SLE products are available in all automation formats. In addition, bulk sorbent can be purchased for those who wish to make their own customized SLE device.
8. Solid Phase Extraction (SPE ) click
SPE is a sample preparation process by which compounds that are dissolved or suspended in a liquid mixture are separated from other compounds in the mixture according to their physical and chemical properties. SPE is fundamentally chromatography using materials that show lower levels of Solid phase extraction can be used to isolate analytes of interest from a wide variety of matrices, sample including urine, blood, water, beverages, soil, and animal tissue. The technique is used for concentrating and purifying samples for analysis. The technique is also used in production of biologics e.g. the extract interesting ingredients from plants that are sold “Herbal Supplements” In the later case the term of “Adsorption LC is used. (See RPC, SPE, Adsorption LC ) SPE uses the affinity of solutes dissolved or suspended in a liquid(called liquid phase) for a solid (called solid phase) through which the sample is passed to separate a mixture into desired and undesired components. The result is that either the desired analytes of interest or undesired impurities in the sample are retained on the stationary phase. The portion that passes through the stationary phase is collected or discarded, depending on whether it contains the desired analytes or undesired impurities. If the portion retained on the stationary phase includes the desired analytes, they can then be removed from the stationary phase for collection in an additional step, in which the stationary phase is rinsed with an appropriate eluent.
For convenient sake SPE is sold mostly in professionally packed disposable Cartridges / Kits / Syringes. For production scale application solid phase materials are procured in bulk and packed in large columns to enable back-flushing and reconditioning of columns for long-term use. We offer the most comprehensive product range of polymer, inorganic or silica base stationary phases packed in cartridges, columns or as bulk. We also guide you with relevant know how to assure your success. Don’t hesitate to contact us for advice.
9. QuEChERS click
Stands for (Quick Easy Cheap Effective Rugged Safe) is a streamlined technique that has been used primarily in pesticide analysis but is now used also in bioanalytics Some modifications to the original QuEChERS method had to be introduced to ensure efficient extraction of pH dependent compounds, to minimize degradation of susceptible compounds (e.g. base and acid labile pesticides) and to expand the spectrum of matrices covered.
The analyst homogenizes the sample in a blender and puts it in a centrifuge tube with a reagent and agitates for one minute. The reagents used depend on the type of sample to be analysed. Following this the sample is put through a clean-up column prior to analysis by Chromatography. We supply QuEChERS and assist you to succeed
Many column manufacturers recommend use of packed guard columns that can be attached to the column so as to filter “contaminations” before they enter the column. Most manufacturer sell columns packed with relevant materials that can be screwed into the inlet of a column. We assist you to find the appropriate packed guard columns
b. Mechanically assisted Systems
1. Direct Injection with on-line sample preparation system
The sample is applied directly to the LC-MS system which incorporates a sample clean-up / enrichment pre-column / trapping Column and switching valves. First time offered by Spark Holland
c. Sample Storage Facilities
1. High Quality Autosampler vials click
Wide range of Autosampler vials and caps to fit all types of Autosamplers
2. RSA (Reduced Surface Active) Glass Autosampler or Storage Vials click
Vials for sensitive samples
d. Future Trends
Samples will become more complex. The future of Sample Preparation is to simplify, minimise and automate sample preparation while at the same time demand for more data and information is expanding
High Throughput Bioanalytical Sample Preparation, Methods and Automation Strategies, By David Wells, January 2003, Elsevier, ISBN: 978-0-444-51029-7