SU1728724A1 - Viscosity determination method - Google Patents

Abstract

Use: determination of physicochemical parameters of viscous media. Summary of the Invention: a luminescent substance (luminescent label) is dissolved in the test liquid, irradiated with monochromatic light, and the fluorescence spectrum of the label is recorded at the excitation wavelength. Fluid viscosity is determined from the half width of the fluorescence spectrum using a calibration curve.

Description

The invention relates to the determination of the physicochemical parameters of viscous media, in particular, to a method for determining viscosity.

In organic chemistry, methods are known for determining viscosity in which fluid flow through a capillary under constant pressure is used.

These methods cannot quickly and accurately measure the viscosity of small volumes (1-2 ml) of highly viscous liquids. . Closest to the present invention is a method for measuring intermolecular interaction parameters in a liquid based on irradiating the liquid with monochromatic light radiation and recording the Raman spectra.

The disadvantages of this method are that the Raman spectra are a less sensitive method than the luminescence spectra. Second and higher overtones in the Raman spectra

have extremely low intensity and for their registration (for example, in order to measure the half width), an increase in the power of laser radiation is required, which can affect the physicochemical properties of the liquid itself.

The aim of the invention is to simplify and improve the accuracy of determining the viscosity of small volumes of highly viscous liquids.

The goal is achieved by the fact that in the proposed method for determining viscosity, including irradiating a liquid with monochromatic light and recording the emission spectrum of a liquid, the luminescent substance (fluorescent label) is dissolved in the liquid under test, the fluorescence spectrum of the label is determined at the excitation wavelength, the fluorescence spectrum is determined and a calibration curve plotted for a given label using liquids with known viscosity (/

with

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the viscosity of the test liquid is determined.

To determine the viscosity of small volumes of highly viscous liquids, a luminescent substance is dissolved in them and its fluorescence spectrum is recorded. Polycyclic aromatic hydrocarbons (anthracene, perylene, pyrene, etc.) with a high quantum yield are used as a luminescent label. The fluorescence spectrum of the label dissolved in a liquid is recorded at the excitation wavelength, the half-width of the spectral dependence is determined, and the result is plotted on a calibration curve (the dependence of the half-width of the label's fluorescence spectrum on the viscosity of the liquid), while constructing the curve, liquids with known viscosity are used . Determining the viscosity in this way allows the use of small volumes of liquids (1-2 ml), and also allows working with any liquids and does not change the physicochemical properties of the liquid during its investigation.

Example The test liquid (menthol oil) is taken in an amount of 2 ml, 0.4 ml of a solution of pyrene in n-hexane (C m / l) are introduced and placed in a quartz cell 10x10 mm in size. Next, record the spectrum-fluorescence when recording at the excitation wavelength in the range of 350-400 nm, determine the half-width (width at half-height) of the fluorescence spectrum, put it on the calibration curve of the dependence of the half-width on viscosity

liquids Dg (/), which determine viscosity: menthol oil 86 cP, For by: building a calibration curve, a solution of pyrene in n-hexane with a concentration of m / l is placed in a 10x10 mm quartz cell, recording the fluorescence spectrum during registration on excitation wavelength, half width determined. Next, vaseline oil (5, 10%) is added to the solution, after each addition, the fluorescence spectrum is recorded and the half-width is determined. Build the dependence D (/) for pyrene. The viscosity of menthol oil obtained using an Ostwald viscometer is 86 cP (at T = 20 ° C).

Using the proposed method of viscosity determination will simplify and improve the accuracy of viscosity determination of highly viscous liquids, reducing the volume of the test liquid.

Claims (1)

Claims. A method for determining the viscosity of a fluid, including irradiating the fluid with monochromatic light and recording the emission spectrum of a fluid, characterized in that, to simplify and improve the accuracy of viscosity determination, the fluorescent label is measured in the fluid, the fluorescence spectrum of the label is measured at the wavelength of the exciting light, measured the half-width of the spectrum and using the calibration curve for this label determine the viscosity of the liquid,