PSS - Polmer Standards Service

GPC/SEC measurements require a certain amount of time. Depending on the number of analytical columns the time requirement per sample/injection is in the range of 12 minutes to 60 minutes. To handle an ever increasing number of samples in shorter time several strategies have been implemented. However, many of these solutions have the disadvantage that information is lost (e.g. Flow Injection Polymer Analysis, FIPA - no distribution information, only averages) or that resolution is lost (shorter or less columns). There are only a few options that are information rich and fast:

1. Instrument cloning
2. Multiplexing: parallel analysis on a single shared instrument
3. Overlaid injection
4. Small particle technology
5. Column dimension modifications
        HighSpeed GPC/SEC with specially designed columns

PSS offers complete turn-key systems for instrument cloning as well as dedicated GPC/SEC systems with HighSpeed columns for interaction-free aqueous and organic GPC. 

The turn-key system is based on the modular SECcurity GPC System with WinGPC Unity GPC/SEC software. The WinGPC Unity overlaid injection feature allows to save 30-50% time and solvent with any injection, due to the unique WinGPC data structure with the integrated sample database. Overlaid injection works for GPC/SEC and HighSpeed GPC/SEC alike.

PSS has identified HighSpeed columns with optimized column dimensions as the best solution for fast GPC/SEC. HighSpeed columns allow efficient separation within 2 minutes analysis time per column and sample. They are operated at higher flow rates. Their column dimensions (inner diameter and length) are especially designed for these conditions.

The SECcurity GPC System is ideally equipped for the PSS HighSpeed columns and allows high flow rates with highest flow precision. The autosampler provides fast injection cycles to allow injections every minute. WinGPC Unity offers convenient automation routines incuding automatic calibration/recalibration and reporting. The WinGPC ReportDesigner can set automatic QC flags (e.g. passed/fail) and can be programmed to automatically caculate additional results.

PSS offers also products for clients, that only want to reduce the analysis time and sample preparation time while keeping their analytical columns. PSS ReadyCals are polymer cocktails preweighted into autosampler vials. Each of the three vials has three or four polymers of the same type with different molar masses. So a 12 (9)-point calibration curve can be constructed from only three injections. The cocktail is composed that all samples are baseline separated even when only one (linear or mixed-bed) column is used, giving also access to universal calibration curves.  

The reproducibility can be best shown with an example:

A commercial Poly(carbonate) has been analyzed in THF on PSS HighSpeed GPC columns SDV 5µ 1 000 Å and 100 000 Å. The sample has been injected 60 times, the overall analysis time was 2.5 hours. The figure shows the overlay of 10 repeat injections.

Results Poly(carbonate):
                        Mw = 29 610 ± 150 g/mol,

                        with an RSD of 0.5 %

Nominal Mw producer: 30 000 g/mol.

Back pressure:

Due to the large inner diameter and the optimized column materials HighSpeed columns (6.25 ml/min) produce lower back pressure than analytical columns (1 ml/min). Therefore they minimize shear degradation and are ideal for stress free sample testing, especially for high molecular weight compounds.

Every GPC/SEC column has a defined interstitial volume, where only solvent can elute while the sample is still moving through the column. Analytical columns from PSS with a length of 30 cm and a diameter of 0.8 cm have an interstitial volume of approximately 5 ml per column. For separations at a flow rate of 1 ml/min this means that during the first 5 minutes per column sample can not be eluted. Due to this fact it is not necessary to wait for complete elution of one sample before injecting the next sample.

The figure shows 2 different injects in WinGPC, each inject indicated by an injection mark (blue triangle at the bottom) and the sample name at the top right. Before the system peaks and the internal standard (light green triangle) of “PS 280 br” are eluted, the next sample “PS 1124 a” is already injected at 8.5 ml. The analysis and data evaluation

of sample “PS 280 br” is not affected by that; baseline and

integration limits can be set as required by national and

international GPC standards, e.g. ISO 13885.