RU2359257C1 - Method of quantitative analysis of substances resting on nmr (nuclear magnetic resonance), namely oil and water in test sample of oilseeds conversion product - mill cake or oil cake - Google Patents

Abstract

FIELD: instrument engineering.

SUBSTANCE: use: for simultaneous definition of oil and water quantity in test sample of oilseeds conversion product - mill cake or oil cake. Essence of invention: the mass of analysed test sample (P_sample) is defined with inaccuracy of 0.01 g. Then it is put into special test tube and placed into sensor of NMR analyser signals. NMR signal, proportional to oil and water total number in test sample ("Асис"), and signal proportional to oil amount in test sample ("Аом"), is registered. The value of signal proportional to water amount in test sample (A₁w) is calculated. And according to specified algorithm of received signals processing the oil amount (P_O) and water amount (P_w) in test sample is defined from the following empiric equations: P_O=a1×A"ом"+ B1; P_w=a2× A₁w + B2, where a1, B1, a2, B2 - coefficients received at analyser calibration. Note that in algorithm of received signals processing is additionally included process of signal (A₁w) value correction for each test sample depending upon oil amount according to formula.

EFFECT: task is to decrease inaccuracy of mill cake and oil cake test samples moisture measuring at definition of quality factors of oily raw material by pulse NMR analysers.

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Description

The invention relates to the field of practical application of pulsed NMR spectrometers for the rapid determination of the oil and water content in oilcake and meal, which are products of the processing of oilseeds.

A known method for the quantitative analysis of substances based on the NMR phenomenon (AS No. 1173279 G01 No. 24/08, BI No. 30, 1985, prototype). The method is as follows: the analyzed sample is placed in a test tube, which is then installed in the NMR signal sensor located in the gap of the magnetic system. A sample is exposed to a series of Kara-Parsell-Maybum-Gill radio frequency pulses of 130 ms duration (90 ° pulse duration is 20 μs), and NMR signals are obtained. In the intervals between series of radio frequency pulses, the temperature of the analyzed sample is measured. Accumulate the results of measurements of NMR signals and the temperature of the analyzed sample during its analysis. The average values of the NMR signals and the sample temperature for the analysis time are calculated. The average value of the measured NMR signal and the average temperature of the analyzed sample calculate the corrected value of the NMR signal. The value of this signal and the equation of dependence of the amplitude of the NMR signal on the amount of substance in the sample, which was obtained by calibrating the analyzer, determine the amount of substance in the analyzed sample. The method of quantitative analysis of substances based on the NMR phenomenon, described in the prototype and used to determine the quality indicators of oilseeds, provides the values of oil content and humidity of SEEDS of oilseeds with accuracy acceptable for practical purposes.

The disadvantage of the prototype is a large error in determining the moisture content of the products of seed processing - MUZHIKOV, SHROTOV. This is due to the fact that, in oilcake and meal, the parameters of the NMR signals from water noticeably differ from similar characteristics in seeds. In cake and meal, most of the cellular structures of seeds are destroyed, and newly formed surfaces of plant tissues, having a large force field, reduce the mobility of water molecules. A change in the mobility of water molecules leads to variations in the parameters of the NMR signals, which directly affects the measurement errors of the quality indicators of meal and meal.

The difficulty lies in the fact that the change in the mobility of water molecules in oilcake and meal is not constant for all their varieties, but depends on the characteristics of each individual sample and, first of all, on the oil content in it. This is explained by the fact that oilcakes and meal, having different oil content, differ from each other in their ability to adsorb water, which leads to variability in the degree of bonding of water molecules to the solid part of the samples, i.e. to variations in the mobility of these molecules, and when measuring NMR signals from water, this will manifest itself in the difference in their values at the same humidity of the samples.

The mechanism of the influence of the mobility of water molecules on the parameters of NMR signals is as follows: in accordance with the well-known practice of pulsed NMR spectroscopy 1, 2, 3, the measurement of the NMR signal after the 90 ° pulse is carried out some time after its completion. This time is called “dead”, its value can range from units to tens of microseconds (in NMR analyzers, such as AMB, “dead” time is 60 μs). This time is necessary in order for the oscillations of the radio frequency system to be established, caused by the action of a powerful probe pulse.

However, during this same time, a partial dephasing of the spin system of the aqueous component also occurs, i.e. loss of information on the amount of water in the sample (misphasing of the spin system is manifested in a decrease in the magnitude of the NMR signal). The dephasing rate of the spin system of matter is determined by the mobility of its molecules. The lower the mobility of the molecules of a substance, the faster the dephasing of its spin system occurs. Since in cake and meal the mobility of water molecules to some extent depends on the amount of oil content, then with the same water content in the analyzed samples of cake or meal, the signal value (Av) will change in accordance with the amount of oil in them (Fig. 1).

Table 1 (figure 2) shows the results of determining the moisture content of cake samples using the method described in the prototype. Oil content and humidity were determined on a commercially available NMR analyzer of oil content and moisture content of oilseeds and their processed products AMV-1006M (TU 4215-101-004959-6401). According to the technical documentation on AMV-1006M, the error in determining the moisture content of seeds, oilcakes and meal should not exceed 0.5% abs.

From the data of the table it follows that when determining the moisture content of the cake samples on the analyzer AMV-1006M using the prototype method for 50% of the analyzed samples, the error in determining humidity is outside the acceptable range.

Table 1 The results of determining the moisture content of samples of cake of various oil content using the method described in the prototype Rpr, g M,% GOST 13979.2-68 In,% GOST 13979.1-68 Rv, g AT, % ΔV,% 14.29 9.64 4.28 0.538 3.77 -0.51 14.20 9.64 7.07 0.890 6.27 -0.80 14.10 9.64 8.91 1,137 8.06 -0.85 13.62 9.64 11.88 1,402 10.29 -1.59 13.91 12.76 4.17 0.585 4.20 -0.30 14.29 12.76 6.99 0.935 6.54 -0.49 14.12 12.76 8.95 1,217 8.62 -0.51 13.37 12.76 12.09 1,423 10.64 -1.58 12.16 19.61 4,50 0.585 4.20 -0.30 12.51 19.61 7.03 0.935 6.54 -0.49 12.58 19.61 9.13 1,217 8.62 -0.51 12.45 19.61 12.22 1,423 10.64 -1.58 11.75 21.92 2.81 0.434 3.70 0.89 12.06 21.92 7.61 0.959 7.95 0.34 12.00 21.92 10.05 1,260 10.50 0.45 11.62 21.92 12.15 1,402 12.07 -0.08

In the samples of meal, the dependence of the signal value (Av) on the oil content in them is also observed. Table 2 (figure 3 and 4) shows the results of determining the moisture content of samples of meal using the method of the prototype.

Analysis of the data in table 2 showed that the error in determining the moisture content of almost half of the analyzed samples of meal is outside the acceptable values.

The present invention solves the problem of reducing the error in measuring the moisture content of samples of meal and meal with the help of pulse NMR analyzers of oil content and moisture of meal and meal.

table 2 The results of determining the moisture content of samples of meal of various oil content using the method described in the prototype Rpr, g M,% GOST 13979.2-68 In,% GOST 13979.1-68 Rv, g AT, % Δ V,% 13.00 1.01 4.70 0.591 4,55 -0.15 13.51 1.01 5.44 0.675 5.00 -0.44 13.40 1.01 8.58 1,083 8.09 -0.51 12.69 1.01 11.87 1,323 10.43 -1.44 12.10 1.13 5.11 0.638 5.27 0.16 12.10 1.13 5.79 0.687 5.68 -0.11 12.80 1.13 8.93 1,082 8.45 -0.48 12.54 1.13 11.97 1,323 10.55 -1.42 11.47 5.56 4.97 0.619 5.40 0.43 12.10 5.56 9.47 1,157 9.56 0.09 12.00 5.56 11.97 1,322 11.02 0.95 13,20 0.70 8.43 1,041 7.89 -0.54 14.00 1.01 8.60 1,082 7.73 -0.87 12.50 1.13 8.92 1,056 8.45 -0.47 12.90 3.73 10.69 1,285 9.96 -0.73 11.90 5.56 9.42 1,140 9.58 0.16

The purpose of the invention is to take into account the effect of oil content of each individual sample of cake or meal on the error in determining its moisture content by pulse NMR analyzers.

The technical result is achieved by the fact that in the known method for the quantitative analysis of substances based on the NMR phenomenon, according to which the analyzed sample is placed in a test tube and introduced into the NMR analyzer of the analyzer, nuclear magnetic resonance signals proportional to the number of detected substances in the sample are recorded, they accumulate during n measurement cycles, calculate the average values of the NMR signals and calculate the number of analytes in the analyzed sample from the average value of the NMR signal and the equations of dependence and the amplitude of the NMR signal of the amount of the substance to be determined, which were obtained by calibrating the analyzer according to the invention, when this method is used to simultaneously determine the amount of oil and water in samples of oilseed processing products - oilcake and meal, NMR signals proportional to the amount of oil are recorded (Am ) and the amount of water (Av), find the amount of oil (Pm) and water (Pv) according to a certain algorithm for processing the obtained NMR signals according to the following imperial equations:

Pm = a ₁ × Am + in ₁ ; Pb = a ₂ × Av + in ₂ , where a ₁ , in ₁ , a ₂ , in ₂ are the coefficients obtained when calibrating the analyzer, and the algorithm for processing the received NMR signals additionally includes the operation of correction of signal values proportional to the amount of water in the sample ( Av) for each sample, depending on the amount of oil in it according to the formula:

Avk = Av × K,

where K = 1-Rm / Ppr;

Av is the value of the NMR signal proportional to the amount of water in the sample;

Avk - the adjusted value of the NMR signal proportional to the amount of water in the sample;

K is the correction factor;

Rm is the mass of oil in the sample, in grams;

Rpr - the mass of the sample in grams.

Using the coefficient K to correct the values of the Av signals provides the moisture values of samples of meal and meal with errors not exceeding the permissible values for commercially available pulse quantitative NMR analyzers. Table 3 (FIGS. 5 and 6) shows the results of determining the moisture content of cake samples using adjusted values (AVK).

From the data of table 3 it follows that when using the corrected values (AVK), the errors in determining the moisture content of all analyzed samples of oil cake do not exceed the permissible values.

The effectiveness of adjusting the values (Av) for the meal samples is shown in Table 4, which shows the results of determining moisture using the corrected values (Avk).

From the data of table 4 (Fig.7) it follows that when using the corrected values (AVK), the errors in determining the moisture content of all analyzed samples of meal are within the acceptable values.

Table 3 The results of determining the moisture content of the cake samples using the corrected values (Avk) Rpr, g M,% GOST 13979.2-68 In,% GOST 13979.1-68 Av, ton.ed. TO Av corr., Rel. Rv, g B% ΔV,% 14.29 9.64 4.28 30,2 0.908 27.4 0.634 4.43 0.15 14.20 9.64 7.07 77.3 0.910 70.3 0.971 6.84 -0.23 14.10 9.64 8.91 121,2 0.912 110.6 1,219 8.65 -0.26 13.62 9.64 11.88 204.6 0.915 187.2 1,523 11.48 -0.30 13.91 12.76 4,50 31.3 0.878 27.5 0.634 4,56 0.06 14.29 12.76 7.03 79.7 0.881 70,2 0.970 6.78 -0.25 14.12 12.76 9.13 135.0 0.884 119.4 1,265 8.96 -0.17 13.37 12.76 12.22 232.0 0.888 207.1 1,555 11.33 -0.39 12.16 19.61 4.17 18.5 0.812 15.1 0.523 4.30 0.13 12.51 19.61 6.99 65.9 0.818 53.9 0.850 ' 6.80 -0.19 12.58 19.61 8.95 118.6 0.821 97.4 1,145 9.10 0.15 12.45 19.61 12.09 224.7 0.828 186.0 1,511 12,13 0.04 12.06 21.92 7.61 74.6 0.797 59.5 0.892 7.40 -0.21 12.00 21.92 10.05 137.3 0.803 110,2 1,217 10.14 0.09 11.62 21.92 12.15 196.7 0.807 158.8 1,432 12.32 0.17

Thus, the inclusion in the algorithm for processing measurement information when determining oil content and moisture of oilcakes and meal by pulse NMR analyzers, additionally according to the invention, the operation of signal correction (Av) depending on the oil content in the analyzed samples can significantly reduce the error in determining their moisture content.

The claimed technical solution can be used in radio spectroscopy, in particular for the calibration of quantitative NMR analyzers for natural samples of oilcake and meal, as well as for determining the quality indicators of oilseeds by such analyzers. So, for example, the NMR calibration of the oil content and moisture analyzer of oilseeds and their processed products AMV-1006M using natural samples of cake or meal using the proposed technical solution was carried out as follows: cake or meal samples intended for calibration of the NMR analyzer were weighed with an error 0.01 g, then in a special test tube they were sequentially placed in the NMR signal sensor of the graduated analyzer, NMR signals proportional to the amount of oil (Am) and the amount of water (Av) for each sample. The amount of oil (Rm) and water (Rv) in the cake or meal samples was determined by arbitration methods - the amount of oil according to GOST 13979.2-68, and the amount of water according to GOST 13979.1-68.

Table 4 The results of determining the moisture content of meal samples using the corrected values Avk Rpr, g M,% GOST 13979.2-68 In,% GOST 13979.1-68 Av, ton.ed. TO Avk, rel. units Rv, g AT, % ΔV,% 13.00 1.01 4.70 40,4 0.942 38.1 0,600 4.61 -0.09 13.51 1.01 5.44 49.7 0.935 46.5 0.690 5.11 -0.33 13.40 1.01 8.58 107.1 0,903 96.7 1,142 8.52 -0.06 12.69 1.01 11.87 193.9 0.872 169.0 1,527 12.04 0.17 12.10 1.13 5.11 45.6 0.940 42.8 0.651 5.38 0.27 12.10 1.13 5.79 51.0 0.933 47.6 0.702 5.80 0.01 12.80 1.13 8.93 106.9 0.902 96.4 1,140 8.91 -0.02 12.54 1.13 11.97 192.0 0.871 167.2 1,522 ^! 12,13 0.16 11.47 5.56 4.97 43.5 0.894 38.9 0.608 5.30 0.33 12.10 5.56 9.47 122.3 0.851 104.0 1,195 9.88 0.41 12.00 5.56 11.97 189.9 0.826 156.8 1,484 12.37 0.40 13,20 0.7 8.43 99.7 0.910 90.8 1,097 8.31 -0.12 14.00 1.01 8.60 107.1 0.989 105.9 1,209 8.63 0,03 12.50 1.13 8.92 102,2 0.901 92.1 1,107 8.86 -0.06 12.90 3.73 10.69 160.9 0.859 138.3 1,402 10.87 0.18 11.90 5.56 9.42 118.5 0.850 100.7 1,172 9.85 0.43

Based on the obtained signal values (Am) and the corresponding oil mass values (Рm), the calibration characteristic of the NMR analyzer for oil was built:

Pm = f (Am)

Then, in accordance with the proposed technical solution, the correction factor (K) was determined by the formula: K = 1-Rm / Rpr for each sample of cake or meal. The correction of the signal values (Av) was carried out by multiplying the values obtained for the cake or meal meal (Av) by the corresponding correction factor:

Avk = Av × K

Using the adjusted values (ABC) and the corresponding values (Pb) obtained by the arbitration method, we constructed the calibration characteristic of the NMR analyzer for water for cake and meal:

Pb = f (Avk)

The procedure for calculating the correction factor (K) and obtaining the corrected values (Avk) is included in the information processing program for determining the oil content and moisture of the cake and meal after calculating (Am), (Av) and (Rm). This completes the calibration process of the NMR analyzer.

The oil content and moisture content of oilcake and meal on an already calibrated NMR analyzer using the proposed technical solution is carried out as follows: a cake or meal meal intended for analysis is weighed with an error of 0.01 g. The obtained sample mass value (Rpr) is entered into the computer. Then the sample in a special test tube is placed in the signal sensor of the NMR analyzer. In the analysis process, in accordance with an improved measurement information processing algorithm, the values (Am), (Rm), (Av), (K), (Avk) and (Rv) are sequentially determined.

Sample moisture is defined as the ratio:

In,% = Rv / Rpr × 100;

oil content as a ratio:

M,% = Pm / (Rpr-Rv) × 100

At the end of the analysis, only the oil content and moisture content of the cake or meal meal sample are displayed.

The introduction of the corrected NMR signal proportional to the amount of water in the sample into the algorithm for calculating the moisture content of the cake or meal, reduces the measurement error of this indicator of the quality of the sample, thereby achieving the goal and solving the problem.

Claims (1)

A method for the quantitative analysis of substances based on the NMR phenomenon, in particular oil and water, in a sample of an oilseed processing product - oil cake or meal, according to which the analyzed sample is placed in a test tube and introduced into the NMR analyzer of the analyzer, nuclear magnetic resonance signals proportional to the number are recorded analytes in the sample, accumulate them during n measurement cycles, calculate the average values of the NMR signals and calculate the number of analytes in the analyzed sample by the average value NMR signal and equations of dependence of the amplitude of the NMR signal on the amount of analyte, which were obtained by calibrating the analyzer, characterized in that if this method is used to simultaneously determine the amount of oil and water in samples of oilseed processing products - oilcake and meal, NMR signals are recorded proportional to the amount of oil (Am) and the amount of water (Av), find the amount of oil (Rm) and water (Rv) according to a certain algorithm for processing the obtained NMR signals according to the following imp nical equations: Pm = a ₁ · AoM + _1; Pb = a ₂ · A ₁ in + ₂ , where a ₁ , ₁ , a ₂ , ₂ are the coefficients obtained by calibrating the analyzer, and the algorithm for processing the obtained NMR signals additionally includes the operation of correcting signal values proportional to the amount of water in sample (Av) for each sample, depending on the amount of oil in it according to the formula:
Avk = Av · K,
where K = 1-Rm / Ppr;
Av is the value of the NMR signal proportional to the amount of water in the sample;
Avk - the adjusted value of the NMR signal proportional to the amount of water in the sample;
K is the correction factor;
Rm is the mass of oil in the sample, g;
RPR - sample weight, g.

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