Why do we offer different cross-linked resins in our columns?
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Benson Polymeric offers several types of polymeric based columns for the analysis of carbohydrates, organic acids, and alcohols. The optimum choice of column is typically a combination of peak resolution, analysis time and value. Our columns are packed with sulfonated (strong cation) polystyrene-divinylbenzene co-polymers. These PS-DVB based columns are chemically stable and extremely reliable. In order to maximize the separation of the different types of samples common to the industries we serve, Benson Polymeric utilizes three variations of the PS-DVB co-polymer (4%, 6%, and 8% cross-linked).
A cross-link is a bond that links one polymer chain to another. They can be covalent bonds or ionic bonds. “Polymer chains” can refer to synthetic polymers or natural polymers (such as proteins). When the term “cross-linking” is used in the synthetic polymer science field, it usually refers to the use of cross-links to promote a difference in the polymers’ physical properties.
Source: Wikipedia
Our three standard polymers are functionalized into different ionic forms to further enhance the separation of specific samples. But we are not limited to just these three basic cross-link resins.
Benson Polymeric can produce resins from 0.5 % to 80 % cross-linked in a variety of bead sizes. Contact us if you are in need of something “special.”
8% Cross-Linked
The majority of columns on the market for the analysis of carbohydrates, organic acids, and alcohols utilize an 8% cross-link poly(styrene/divinyl benzene) (PS-DVB). The 8% polymer offers excellent separation of many common samples.
Advantages:
8% polymers combine durability and good resolution. Due to higher cross-linking than 4% and 6% cross-linked polymers, columns packed with 8% polymer can be used at higher flow rates therefore decreasing analysis times.
Disadvantages:
8% polymers are limited in separating carbohydrates larger than trisaccharides due to lower MW exclusion limits. Compared to the 6% cross-linked polymer, for some types of carbohydrate and organic acid mixtures, the 8% shows less resolution due to selectivity differences.
Benson Polymeric utilizes an 8% cross-link bead in our BP-800, BP-OA, and BP-RA Column series.
Molecular Weight Exclusion Limit: 1000
Minimum Wet Capacity meq/ml: 1.7 – 1.9
Flow Rate Recommendation: 0.4 – 1.2 ml/min
6% Cross-Linked
Advantages:
Due to a higher MW exclusion limit than 8% polymers, columns packed with 6% polymer can separate larger carbohydrate molecules (up to DP6). 6% cross-link polymer gives superior selectivity for some mixtures of carbohydrate and organic acids compared to the 8% polymer.
Disadvantages:
Due to the lower cross-link compared to 8% polymer, the 6% polymer is more pressure sensitive and therefore has a lower flow rate threshold. For some samples with comparable resolution between the 6% and 8% columns, it makes sense to use the more durable 8% polymer for faster analysis times.
Benson Polymeric employs 6% cross-link beads in our BP-100 Column Series.
Molecular Weight Exclusion Limit: 1200
Minimum Wet Capacity meq/ml: 1.5 – 1.7
Flow Rate Recommendation: 0.4 – 0.8 ml/min
4% Cross-Linked
Advantages:
Due to a higher MW exclusion limit than 6% and 8% polymers, columns packed with the 4% polymer can separate larger carbohydrate molecules (up to DP11).
Disadvantages:
Due to the lower cross-linkage compared to the 6% and 8% polymers, the 4% polymer is more pressure sensitive and therefore has a lower flow rate threshold. Due to the pressure sensitivity of the 4% polymer, the bead size of the polymer is larger to keep pressure to a minimum. The larger bead size lowers the efficiency of the column and therefore 4% polymeric columns are limited to samples containing larger chain carbohydrates (e.g. corn syrup).
Our BP-200 Column Series uses a 4% cross-link polymer.
Molecular Weight Exclusion Limit: 1400
Minimum Wet Capacity meq/ml: 1.2 – 1.4
Flow Rate Recommendation: 0.3 – 0.6 ml/min