Analytical techniques

Analytical Services Testing Laboratory Techniques

Conventional GPC, SEC, GFC

Conventional GPC/SEC is an excellent method for sample comparison and the determination of molecular weight of a sample. Conventional GPC/SEC analysis yields the complete molar mass distribution (MMD) and is more informative than a method that only yields an average value (Mw or intrinsic viscosity). PSS offers testing in aqueous and organic mobile phases. Customer requests are usually honored. As a manufacturer of a great variety of polymer standards and of GPC/SEC/GFC columns, PSS is able to use the optimum conditions to characterize your samples. Before each measurement series, the analytical system is validated and calibrated. An internal standard/flow marker is used to monitor the constant flow of the pump and for flow-correction as needed. Afterwards the molecular weight distribution is obtained from the elugram using the corresponding calibration curve.

Calculation of the percentage of a given molar mass (eg. < 500 g/mol) from the molecular weight distribution is usually requested for product approval in the USA and Canada. Additives and stabilizers can be separated from the polymer and a quantitative determination of these compounds is possible. The analysis report lists all relevant parameters of the measurement and documents the sample preparation.

Results provided to the client:

simple comparison of polymer samples
molecular weight distribution
molecular weight averages: Mw, Mn, Mz
polydispersity index PDI/D
percentage of mass, eg. < 500 g/mol
chemical composition

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High Temperature GPC

Some polymers are insoluble at room temperature. E.g. polyolefins (PE, PP) and their co-polymers are only soluble at temperatures over 130° C. PSS offers testing of polymers soluble in 1,2,4-trichlorobenzene at 155° C, using High Temperature GPC systems equipped with refractive index detection, viscosity detection, FTIR-coupling interface and column-switching systems that permits the use of 4 different POLEFIN columns. This gives us the possibility to run polyolefins in a range from hundreds to more than 20.000.000 g/mol. PSS offers standard calibration with polystyrene or polyethylene or a universal calibration using differential capillary viscosity detector.

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2 Dimensional Chromatography

This method is useful for analysis of complex polymer systems like polymer blends, copolymers, functionalized, and branched polymers. These samples are usually heterogeneous in terms of chemical composition, functionality and structure. Since GPC/SEC separates only according to size, GPC/SEC is not sufficient to describe such a system. Therefore, the combination of two chromatographic methods to separate the mixture into more homogeneous fractions (i.e. functional groups) followed by separation by molar masses constitutes a better approach. WinGPC software allows the automatic transition from one dimension to the other. PSS offers the development of 2D applications and performs the analysis for you, with our special software for data acquisition, quantitative interpretation and data plotting, the WinGPC 2D Chromatography module.

Results provided to the customer:

complete deformulation
composition
molecular weight distribution
molecular weight averages, Mw, Mn, Mz
copolymer composition

For more information about the principles and use of 2D chromatography see:

"Facing the Challenge of Analyzing Complex Polymers: A Primer in 2-Dimensional Liquid Chromatography"

All orders for 2 Dimensional chromatography are custom quoted in accordance with the customer needs. Request a quote for more information.

related products:

WinGPC UniChrom with 2D Chromatography module

GPC/SEC with online ESI-MS

Classical detectors used for the determination of molecular weight distributions by GPC/SEC yield accurate information about the polymer concentration. Mass spectrometry has the potential to yield exact molecular weights of individual molecules.

Deriving accurate molecular weight information on polymers by coupling of GPC/SEC with ESI-MS and refractive index (RI) detection is the goal of this analysis. Use is made of the high accuracy of individual molecular weights obtained by mass spectrometry and the possibility of using ESI-MS to depict the concentration profiles of oligomers eluting from the chromatographic column. Absolute concentration information is gained from the concentration sensitive (RI) detector.

This technique is also useful for the determination of polymer statuts for REACH.

Results provided to the client:

molecular weight distribution
absolute molecular weights
quantification
substance identification

For more information about the principles see our PSS Streamliner Mass Matters.

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Customers from USA and Canada can use the online store and pay with credit card:

Print and fill out the sample testing evaluation form, to be sent with the samples
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related products:

WinGPC UniChrom with mass spectrometry module

Conventional GPC, SEC, GFC with on-line Light Scattering

The light scattering detector provides absolute molar masses without requiring the appropriate polymer calibration standards. The GPC/SEC separates the sample by size and the on-line light scattering detector determines the molar mass directly. Clients get the absolute weight average (Mw) and molecular weight distribution of the polymer. The method is limited by the molecular weight of the sample (depending on the type of polymer), the minimum molar mass normally has to be above 5000 g/mol. PSS uses a multi angle light scattering detector (MALLS) during routine operation. The MALLS detector provides additional information about the radius of gyration, which is derived from the angular dependency of the scattered light. From the combination of absolute molecular masses and corresponding radius of gyration, it is possible to obtain important structure information and branching.

Results provided to the client:

molecular weight distribution
absolute molecular weight averages
batch molecular weight average Mw
radius of gyration averages
branching / structure information

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Customers from USA and Canada can use the online store and pay with credit card:

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related products:

PSS light scattering detector SLD7000

PSS dn/dc instruments

WinGPC Unity with Light scattering modules

Conventional GPC, SEC, GFC with on-line Viscometry

The capability to get accurate molar masses without having the proper polymer standards is offered by on-line viscosity detection. This method uses the concept of universal calibration and provides the correct masses, the molecular weight distribution, Mark-Houwink coefficients, and information about the structure of the polymer. With viscosity detection also small molecules (e.g. oligomers) can be analyzed, a big advantage over on-line light scattering measurements.

The GPC - viscosity coupling allows to determine the important relationship between intrinsic viscosity and molar mass of a polymer within one measurement. From this data, the Mark-Houwink parameters of the investigated 'polymer - solvent' system and structural information can be opbtained.

Results provided to the client:

intrinsic viscosity
Mark-Houwink parameters
molecular weight distribution
molecular weight averages, Mw, Mn, Mz
branching / structural information

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Customers from USA and Canada can use the online store and pay with credit card:

Print and fill out the sample testing evaluation form, to be sent with the samples
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related products:

PSS viscometer eta2010

WinGPC Unity with Viscometry module

Conventional GPC, SEC, GFC or HPLC coupling with FTIR-Interface

FTIR is used to identify chemical substances. The coupling of liquid chromatography (LC) with Fourier-Transform-Infrared (FTIR) spectroscopy allows the identification of unknown fractions with the help of a spectra database. When used in combination with a chromatographic system (GPC/SEC or HPLC), the substrate is collected on a rotating Germanium disk. FTIR-spectra can be gained for each point of the chromatogram. PSS uses a special interface to remove the solvent on-line after the chromatographic separation is done. This method allows for identification of the substance as well as for the evaluation of chemical heterogeneity.

Results provided to the client:

chemical structure - chemical purity
information about additives
chemical composition

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related products:

PSS FTIR Interface LC600r

Static Light Scattering - Batch measurements

Static light scattering is an established method for the absolute determination of the weight average molar mass (Mw) of a polymer. The measurement is carried out without separation of the polymer solution in a light scattering detector cell. The measured quantity is the intensity of the scattered light (Excess-Rayleigh scattering), which is proportional to the average molecular size of the dissolved substance. A series of measurements is performed with different concentrations (c) at various scattering angles (theta). The molecular weight average Mw is determined with by plotting the data and extrapolation of c and theta to zero (Zimm-plot). Other parameters derived from the Zimm-plot are the z-average of the radius of gyration and the second virial coefficient A2. One requirement is the knowledge of the refractive index increment (dn/dc) of the polymer in the solvent used.

Results provided to the client:

absolute molecular weight average Mw
radius of gyration z-average
second virial coefficient A2

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Customers from USA and Canada can use the online store and pay with credit card:

Print and fill out the sample testing evaluation form, to be sent with the samples
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related products:

PSS light scattering detector SLD7000

PSS dn/dc instruments

dn/dc - Batch measurement

The refractive index increment, dn/dc, is an important material specific parameter of a polymer solution and is required for evaluating light scattering data. If this parameter is unknown for a given 'polymer-solvent' system, it has to be measured, because the light scattering formula includes dn/dc to the power of two in the calculation of molar mass. PSS can determine the refractive index increment at 620, 535, or 470 nm with excellent precision.

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Viscosity - Batch measurements

Viscosity measurements have a special significance in the quality control of polymers. These measurements, performed under standardized conditions (DIN, ASTM etc.), provide important parameters e.g. for polymer processing. The batch method averages over the whole sample, producing integral values as a result. PSS is able to determine various kinds of viscosities, e.g. relative viscosity, inherent viscosity, intrinsic viscosity etc., even in uncommon solvents like HFIP, meta-Cresol, ortho- Dichlorobenzene and formic acid at temperatures up to 302°F (= 150°C).

Results provided to the client:

absolute, relative, inherent and intrinsic viscosities
Huggins / Krämer constants

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Vapour Pressure Osmometry

The molar mass determination by osmometry is one of the most important methods for evaluating the number average molecular weight Mn. This is an important parameter for the interpretation of kinetic data in polymerization and copolymerization reactions. The method is also of interest for prepolymers with lower molar masses. PSS provides sample testing service using vapour pressure osmometry measurements of polymers with masses Mn < 10000 g/mol in toluene and ultra pure water. A test includes the determination of the device scaling factor and the measurement at four different sample concentrations. The number average molecular weight Mn and the second virial coefficient A2 is evaluated graphically.

Results provided to the client:

number average molecular weight Mn

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Customers from USA and Canada can use the online store and pay with credit card:

Print and fill out the sample testing evaluation form, to be sent with the samples
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