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Capillary viscometer for fully automated measurement of the concentration and shear dependence of the viscosity of macromolecular solutions.

ABSTRACT: The construction and operation of a novel viscometer/rheometer are described. The instrument is designed to measure the viscosity of a macromolecular solution while automatically varying both solute concentration and shear rate. Viscosity is calculated directly from Poiseuille's law, given the measured difference in pressure between two ends of a capillary tube through which the solution is flowing at a known rate. The instrument requires as little as 0.75 mL of a solution to provide a full profile of viscosity as a function of concentration and shear rate, and it can measure viscosities as high as 500 cP and as low as 1 cP, at shear rates between 10 and 2 × 10(3) s(-1). The results of control experiments are presented to document the accuracy and precision of measurement at both low and high concentration of synthetic polymers and proteins.

SUBMITTER: Grupi A

PROVIDER: S-EPMC4166550 | biostudies-literature | 2012 Dec

REPOSITORIES: biostudies-literature

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Capillary viscometer for fully automated measurement of the concentration and shear dependence of the viscosity of macromolecular solutions.

Grupi Asaf A Minton Allen P AP

Analytical chemistry 20121126 24

The construction and operation of a novel viscometer/rheometer are described. The instrument is designed to measure the viscosity of a macromolecular solution while automatically varying both solute concentration and shear rate. Viscosity is calculated directly from Poiseuille's law, given the measured difference in pressure between two ends of a capillary tube through which the solution is flowing at a known rate. The instrument requires as little as 0.75 mL of a solution to provide a full prof ...[more]

PMID: 23130673

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Project description:ObjectiveThe goal of this work is to provide temperature and concentration calibration of water diffusivity in polyvinylpyrrolidone (PVP) solutions used in phantoms to assess system bias and linearity in apparent diffusion coefficient (ADC) measurements.MethodADC measurements were performed for 40 kDa (K40) PVP of six concentrations (0%, 10%, 20%, 30%, 40%, and 50% by weight) at three temperatures (19.5°C, 22.5°C, and 26.4°C), with internal phantom temperature monitored by optical thermometer (±0.2°C). To achieve ADC measurement and fit accuracy of better than 0.5%, three orthogonal diffusion gradients were calibrated using known water diffusivity at 0°C and system gradient nonlinearity maps. Noise-floor fit bias was also controlled by limiting the maximum b-value used for ADC calculation of each sample. The ADC temperature dependence was modeled by Arrhenius functions of each PVP concentration. The concentration dependence was modeled by quadratic function for ADC normalized by the theoretical water diffusion values. Calibration coefficients were obtained from linear regression model fits.ResultsMeasured phantom ADC values increased with temperature and decreasing PVP concentration, [PVP]. The derived Arrhenius model parameters for [PVP] between 0% and 50%, are reported and can be used for K40 ADC temperature calibration with absolute ADC error within ±0.016 μm2 /ms. Arrhenius model fit parameters normalized to water value scaled with [PVP] between 10% and 40%, and proportional change in activation energy increased faster than collision frequency. ADC normalization by water diffusivity, DW , from the Speedy-Angell relation accounted for the bulk of temperature dependence (±0.035 μm2 /ms) and yielded quadratic calibration for ADCPVP /DW = (12.5 ± 0.7) ·10-5 ·[PVP]2 - (23.2 ± 0.3)·10-3 ·[PVP]+1, nearly independent of PVP molecular weight and temperature.ConclusionThe study provides ground-truth ADC values for K40 PVP solutions commonly used in diffusion phantoms for scanning at ambient room temperature. The described procedures and the reported calibration can be used for quality control and standardization of measured ADC values of PVP at different concentrations and temperatures.

Dataset Information

Capillary viscometer for fully automated measurement of the concentration and shear dependence of the viscosity of macromolecular solutions.

Publications

Capillary viscometer for fully automated measurement of the concentration and shear dependence of the viscosity of macromolecular solutions.

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