SU759867A1 - Method of quantitative analysis of metalloporphyrins in petroleum and bitumen - Google Patents

Description

one

The invention Refers to the field of optical methods for analyzing a substance, and more specifically to the field of spectral methods for studying the state of oils and bitumens.

The known method of quantitative analysis of metalloporphyrins (MP) in oils and bitumens from absorption spectra, based on the determination of the in-, θ intensity of the corresponding characteristic bands.

The disadvantage of this method is the large error in determining the intensity of the bands associated with.

the imposition of a strong background of the absorption of resins extracted from the sample together with MP.

The closest technical solution is the method of quantitative analysis of metalloporphyrins in oils and bitumens from the absorption spectra in this method is almost completely eliminated, the error associated with the presence of tar by chromatographic purification of the isolated MPs. Improving the accuracy of determining the intensity of MP bands as a result of the removal of resinous impurities makes it possible to analyze not only the total

2

main content of MP, but also content. individual structural species of van Dilporphyrin or nickelporphyrin.

The disadvantage of this method is its considerable duration associated with the process of chromatographic purification of MP from resins.

The aim of the invention is to reduce the time of analysis.

This goal is achieved by taking photographs of the absorption spectrum in the region of the characteristic bands of metalloporphyrins and in the shortwave and longwave regions of the purely background resin absorption adjacent to it, and the background absorption component of the resins in the region of the MP bands is determined by the absorption intensities purely background spectral region according to the equation

3

(one)

3

759867

four

where, T> d ° - background optical

density in the wavelength region A; and hell

K. and L - constant (for this sample) izdelich us. .

The described method allows to determine the background component of the absorption of the resins in the region of the MP band, and accordingly the intensity of the MP band itself, with an error of no more than 2–4%.

As a result, it is possible to expressly determine the structural varieties of MPs (the total duration of the shooting of the spectrum in the background region and the determination of the absorption components of the resins in the region of the MP bands does not exceed 10–15 minutes).

FIG. 1 shows the spectrum of the MP extract containing vanadyl porphyrins with an admixture of nickel porphyrins (curve 1), calculated values of the background absorption of the resins (curve 2) and base lines 3, in FIG. 2 shows the calculated MT spectrum (curve 1), obtained by graphical subtraction of the background curve in FIG. 1 from the total, and the spectrum of MP, isolated from the analyzed extract chromatographically Shaving 2). For convenience, a comparison, both spectra are normalized by the most intense band of vanadylporphyrins.

Example. The content of vanadylporphyrins of ethio- and deoxofilloerythroethyl-type in the MP mixture isolated from oil (alcohol extraction) is investigated. The sample to be analyzed is dissolved in benzene. The optimal amount of benzene (per MP from 1 g of oil) is 10 ml. The spectrum is filmed in cuvettes with a thickness of 1 cm. Under these conditions and the concentrations of MPs characteristic of oil, the spectrum curve bends due to the presence of MP bands are absent at A £ 510 nm and A 7/620 nm. Accordingly, the spectrum is surveyed in the region of 525–590 nm (the region of the characteristic bands of vanadyl porphyrins) and in the region of 490–510 and 630650 nm. Spectrum points corresponding to wavelengths of 490, 510 and 650 nm are taken as analytical ones.

.At abnormally high concentrations

MP, when in the region of 490-510 nm the curve is bent, the first two analytical points are taken in a shorter wavelength region. The magnitude of the interval between these points of the order of 20 nm provides the required accuracy of determination. The use of substantially large intervals is usually impossible due to a sharp increase in the background intensity with decreasing wavelength.

For the specified values of A, the solution of the system of equations of the form (1) for three analytical points gives the following expression for the quantities k and F:

"Backdrop, background 'background background of ι ι _{k =} ¹⁶⁰ ^ ί> 4ο ₀ / p ₅ ιο - of ₄₉₀ ^g eyR / p; _AO ' ^2}

(650 - 490) (650 - 510) (510-490)

_ 2 ⁰ ¾ ¹ 1% 90 / ^ 650 ~ 1ЬР Р490 / £ ° o (650-490) (650-510) (510-490)

Claims (1)

Claim The method of quantitative analysis of metalloporphyrins in oils and bitumens by absorption spectra, characterized in that in order to reduce analysis time, the absorption spectrum is taken in the region of the characteristic bands of metalloporphyrins, and in the short-wave and long-wave regions adjacent to it, of pure background resins, the background absorption component of resins in the region of metalloporphyrin bands is determined from the absorption intensities at three analytical points of the background spectral region in accordance with equation performance Background ^ background ~ ^to ~ 0 ⁺ * (.% ~ 'DD * background _fon where Ό. , TC. - background optical density ¹ in the region The wavelengths А _g , V) and Kiel are constant (for a given sample) values. 0.7 0.6 0.5 l <3 5 0.4 § ί ε <§ 0,5 02 0.7. 759867 I — 4-1-1_ □ _ — I_1_I_ι I. I I ι 'ι ι 500 550 600 650 Wavelength nor Phage2