Browse through our FAQs to find out more.
PSS is the trusted source of reference polymers, specialty polymers, and customer-designed polymers. A great selection of polymer types in a wide range of molar masses is produced regularly. In addition, PSS cooperates with national and international institutes to certify high-quality reference materials.
FAQ - Frequently Asked Questions
- Finding the Best Product
- Quality and Traceability
What standards does PSS offer?
PSS offers polymeric reference materials which are available as single standards with different molar masses and particle standards. In addition PSS offers copolymers and specialty polymers with varying chemical composition, end groups etc.
To enable the fast and precise creation of GPC/SEC calibration curves specific kits are available which cover a dedicated molar mass range. The single standards selected for the kits ensure that the molar masses are covering the complete range without gaps so that the data fitting process is more precise. ReadyCal Kits are convenient calibration kits which consist already of a mixture of different molar masses in the right concentration premixed in autosampler vials. It is only required to add the GPC/SEC mobile phase, to wait a little bit and to inject directly from this vial.
What standards should I use for calibrating a GPC/SEC system?
Your calibration standards must be soluble in the mobile phase you plan to use. As for GPC/SEC stationary phase materials standards are either classified as aqueous standards for water-based GPC/SEC or as organic standards for GPC/SEC in organic solvents. There are a few standards that can be used for both applications.
To receive accurate molar masses it is best to use standards that are chemically alike to the own samples.
Check Standards Sorted by Type to find the list of available PSS standards for aqueous and organic GPC/SEC or filter in our shop with respect to Type 'Organic' or 'Aqueous'.
The most commonly used reference standards in GPC/SEC are Polystyrene (PS) or Polymethyl methacrylate (PMMA) for nearly all organic GPC/SEC separations including High temperature GPC (PS). Polyethylene oxide (PEO), Polyethylene glycol (PEG), Pullulan or Dextran are used for aqueous GPC/SEC. This is why PSS developed and designed convenient ReadyCal Calibration Kits for these standards.
What standard can be used in aqueous phase if I only have a UV/DAD/PDA detector?
Polystyrene Sulfonate Sodium Salt may be used with ultraviolet detector in aqueous environment (prefered wavelength 254 nm). You can use them in our MCX columns without organic modifiers or with SUPREMA columns using Methanol as an organic modifier. Also able to absorb in UV/Vis are the quaternated Poly(2-vinyl pyridine) and the Proteins.
How do I store of molecular weight standards?
PSS places emphasis to the following:
- Store standards in the PSS original packaging in a cool, dry and dark environment such as a refrigerator (4oC). Make sure the bottles are tightly recapped.
- Do NOT expose the standards to UV radiation. Never store standards under direct sunlight (windowsill or shelf near windows) to prevent sample degradation over time. This warning is critical to polyisoprene, polybutadiene and other temperature and/or light sensitive polymers.
- Do NOT store organic or aqueous standards after they are in solution as they are susceptible to degradation upon solubilization. Never freeze standards in solution; freezing can break chains down resulting in lower molecular weights.
If in doubt contact us.
What is the shelf life of the molecular weight standards?
Shelf life will vary depending on the chemistry and the handling conditions and procedures. Solid standards, especially synthetic standards, are chemically very stable when handled according to the instructions and procedures described in the Users Manual delivered with every shipment. The shelf life of each PSS batch is strictly and continously monitored based on the requirements of each individual chemistry. Products are regularly quality-checked and re-certified.
How do I prepare my molecular weight standards or samples for GPC/SEC analysis?
The easiest and fastest way is to use PSS ReadyCal calibration kits. They consist already of a mixture of different molar masses in the right concentration premixed in autosampler vials. It is only required to add the GPC/SEC mobile phase, to wait a little bit and to inject directly from this vial (recommended waiting time: 30 minutes).
If you prepare your own solutions use the lowest possible concentration and injection volume. A general rule is to decrease the concentration with increasing molar mass. A too high concentration/injected mass will result in distorted peaks, especially for higher molar mass. Good starting conditions for standards with a narrow molar mass distribution (PDI < 1.3) are
- 1 g/L (0.1%) below 1 Million Dalton Molar Mass
- 0.5 g/L (0.05%) above 1 Million Dalton Molar Mass
- broad standards can be measured at 3-5 g/L (0.3-0.5%).
For recommended injection volumes refer to the Column's User Manual. If there is a detection issue due to a too low injected mass it is recommended
- for high molar masses: to increase the injection volume while keeping concentrations low
- for low molar masses: to increase the concentration while keeping the injection volume low
Prevent undue stress including, but not limited to, shaking, high-pressure filtration, ultrasound and or microwaves, during sample dissolution and/or actual testing.
Allow sufficient time to fully dissolve the standards, especially for higher molar masses (> 3 hours for molar masses < 500 kDa, 24 hours > 500 kDa).
How are PSS standards characterized?
All PSS reference materials are synthesized and characterized in the most strict quality environment. Methods are detailed in our ISO 9001:2015 certified quality system. Each polymer standard is assigned a unique batch number and supplied with a Certificate of Analysis (CoA) comprising details of the exact characterization techniques used. The characterization techniques applied always include GPC/SEC to provide the requested Mp information for GPC/SEC calibration. The additional methods used depend on the molar mass of the reference material and the analysis goal. Techniques included are light scattering, viscometry, NMR or related techniques. The batches are contiously monitored and re-certified based on the requirements of the material's chemistry.
PSS offers also a selection of European Reference Materials and a Certified Poly(lactide) reference material. Those standards have been extensively tested in round-robin tests.
Is there an Expiration Date given?
PSS provides an expiration date for every delivered product. PSS batches are continiously monitored and these results as well as our longstanding experience enbable us to provide an expiration date taking into account both, the product stability and the human and environmental influence on handling the product. A prerequisite is of course that the PSS storage recommendations are followed.
What are the delivery times?
Many standards and kits are on stock with a delivery time of 1-3 days. Some specialty products have delivery times of 7-10 days due to enhanced quality checks.
What are the payment options?
Depending on the country of destination PSS offers the following payment options:
- Credit card (MasterCard or Visa card).
How are my standards delivered?
Depending on the country of destination, the goods will be delivered either via UPS, Federal Express or forwarder. Please contact us if you prefer another carrier.