CONICET | Buscador de Institutos y Recursos Humanos

Current research in size exclusion chromatography (SEC) aims at developing robust and automatic correction procedures that do not require the analyst intervention. Band broadening (BB) can strongly distort the molar mass distribution (MMD) of narrow polymers when estimated by SEC. Even though several BB-correction methods have been proposed [1], they are mostly impractical, since they typically require a deconvolution procedure and the a priori estimation of the BB function (BBF) [2, 3]. For SEC with a differential refractometer (DR) and a light scattering detector (LS), this work presents a method for calculating the unbiased MMD of narrow polymers, without explicit knowledge of the BBF. The numerical procedure aims at finding the MMD that satisfies theoretical relationships among the DR and LS signals, and the molar mass calibration. Simulated examples are presented that verify the ability of the algorithm for retrieving unbiased MMDs. Also, the analysis of 10 narrow polystyrene standards (of known average molar masses) with a fast but low-resolution linear column is presented. First, 8 standards were employed to determine the molar mass calibration. Then, the unbiased MMDs of the other 2 standards were acceptably estimated. The robustness of the method was investigated by inserting intentional biases into: i) the interdetector volume, ii) the DR and/or LS detector constants, and iii) the molar mass calibration. When an accurate molar mass calibration is available (e.g., obtained from narrow standards of the analyzed polymer), then the proposed procedure proved insensitive to errors in the detector constants. Due to the low sensitivity of LS sensors towards the low molar masses, this technique is inapplicable to low molar mass polymers (e.g.: < 10,000 g/mol).