DE1598082B2 - PROCEDURE FOR THE IMMEDIATE ANALYSIS OF AQUATIC WARM SOLUTIONS FOR THE CONTENT OF GLUCOSE AND FRUCTOSE - Google Patents

Description

The present invention relates to a method for the immediate analysis of aqueous warm solutions on the content of glucose and fructose, d. H. for simultaneous and instant determination warm aqueous solutions of these two sugars. Such a procedure is a necessary prerequisite the separation of glucose and fructose on ion exchange columns in the technical To be able to carry out a scale (see US Pat. No. 3,044,904 and German Offenlegungsschrift I 567 325). All previously used, known analytical methods for determining glucose and Fructose are useless for the stated purpose, since the determination of the two components is too complicated and, above all, too tedious in continuous operation.

It has now been found that you can get glucose and fructose in warm aqueous solutions immediately can analyze, if one has the optical rotation angle («) and the optical refractive index (> i) measures these solutions at the same temperature as possible. From these values can in itself the concentration of the components can be calculated in a known manner. Although the measurement of Angle of rotation or refractive index in the sugar industry common methods for determining the Representing the concentration of dissolved sucrose is the combination of these measurements for the simultaneous Immediate analysis of mixtures of glucose and fructose has not previously been used.

The reason is to be found in the fact that sugar solutions change their rotation value strongly with temperature and that the Knd rotation value changes during cooling to the usual measuring temperature of 20 "C slowly adjusts (cf. also B r ο w η ο and Ze r ban, Sugar Analysis, 3rd Edition, John Wiley & Sons Inc. 1941, p. 293). Glucose-fructose solutions need to set the final rotation value According to our tests, about 0.5 to 1 hour, which means that it is quick or even without delay Measurement seemed impossible.

Surprisingly, it was found that, despite the difficulties mentioned above, glucose and fructose practically instantly, simultaneously using

ίο the refractive index and angle of rotation can be determined can, if one does not measure these two physical quantities as usual at 20 ° C, but at the same or higher temperature than the temperature of the original solutions. the The rotation value is then set so quickly that the measured values even have an automatic Computer (e.g. analog computer) can be used to automatically control the separation column.

This result could not have been foreseen and is based on a previously unknown effect for which there is still no explanation: namely, if you try to determine the temperature dependence of the rotation value of fructose, more than an hour's waiting time is required for each measuring point, until a sufficiently constant rotation value - adjusts - provided that it is a fructose solution acts that have previously been cooled from higher temperatures to the measuring temperature. If, on the other hand, the fructose solution is heated from a lower temperature to a higher measuring temperature, surprisingly, the angle of rotation is set in a matter of seconds. Through this Finding it was possible for the first time to combine glucose and fructose in warm aqueous solutions to be determined by measuring the angle of rotation (α) and the refractive index (n) and thus to a technically extremely important process. Apparently nobody has yet walked the described path,

1. since the above-mentioned effect of adjusting the rotation value of the fructose was unknown and 2. Because it is, of course, a painstaking job (instead of the values available in the literature for 20 °) to record new calibration values for higher temperatures from the calibration values function equations to determine and to calculate nomograms from this.

To carry out the method according to the invention, part of the from the end of the Warm solution emerging from the ion exchange column, which contains varying amounts of glucose and fructose, Rotation angle and refractive index measured at the same or slightly higher temperature. As measuring devices In principle, all commercially available polarimeters are used for the angle of rotation and the refractive index and refractometers with flow cuvettes in question, the measured values are in the usual way evaluated by means of a nomogram. However, it is preferable to use continuously registering, polarimeters and refractographs with good thermostatic control, in which the solution to be measured is after the passage is fed back to the main stream of the liquid emerging from the separation column

f> .s can be. These continuous devices ge-Uatten it is generally also possible to take the measurement result as a proportional voltage at the same time, which means both a program-controlled

Analog computers and multi-color recorders can be fed.

It goes without saying that the method according to the invention is not only for analyzing the eluates from the start Invert sugar solutions separated by ion exchangers (according to US Pat. No. 3,044,904 and German Offenlegungsschrift 1 567 325), but in principle for the analysis of all technically occurring warm sugar solutions.

The process according to the invention is explained in more detail in the following examples. It shows:
Fig. 1 Nomogram for 60 °,
Fig. 2 Elution diagram glucose-fructose measured at 60 ° and evaluated using the 60 ° nomogram,

Fig. 3 Elution diagram of glucose-fructose measured at 20 ° and with the aid of a 20 ° nomogram evaluated.

example 1

Discontinuous rapid determination of glucose

and fructose in eluates one

Ion exchange column

^{The 6O 0} C warm invert sugar solution exiting at the end of a cation exchange column loaded with calcium ions, more or less separated into glucose and fructose (cf. USA.-Patent 3 044 904 and German Offenlegungsschrift 1 567 325) is partly passed through a polyethylene tube that is as short as possible a polarimeter and passed through a refractometer with flow cuvettes and then reunited with the main stream. The values are read every 10 minutes and evaluated in the usual way using a nomogram calculated for 60 °.

The nomogram (Fig. 1) is calculated from the corresponding calibration curves. The concentration values for Glucose and fructose are entered in a diagram (Fig. 2) and show that glucose and Fructose emerge largely separately from the column. Fractions that predominantly have one component are collected separately and processed to fructose or glucose. Parliamentary groups, which still contain considerable proportions of both components. with the original invert sugar solution combined and again subjected to a chromatographic separation.

For comparison, the emerging from the column sugar solution is passed before entry into the measuring instruments through a cooler and cooled to 2O ⁰ C exactly. Every 10 minutes are read refractive index and optical rotation and evaluated by means of a calculated for 2O ⁰ C nomogram. The values for glucose and fructose are drawn in a diagram as described above (Fig. 3), this shows that the fructose is apparently still contaminated with considerable amounts of glucose. Checking this result with conventional but time-consuming analytical methods for determining fructose and glucose shows that the indications are unequivocal false indications that are based on the fact that the end rotation of the fructose is set too slowly.

B e i s ρ i c 1 2

The as in Example 1 from the Haupistrom animal Hlunte an operated at 55 C Chronuuounipliie · pillar branched-off part of the sugar solutions is heated by a thermostatically controlled water bath at precisely 60 ⁰ C before the measurement. The values for glucose and fructose determined from the measured values for refractive index and angle of rotation by means of a nomogram result in an elution diagram similar to Fig. 1.

Example 3

ίο Continuous rapid determination of glucose and Fructose in eluates from ion exchange columns

^{A partial flow of the 6O 0} C warm eluates exiting at the end of an ion exchange column is passed through a polyethylene tube that is as short as possible through a continuously recorded polarimeter (Zeiss) and a continuously recorded refractograph (Zeiss), from which the measured value is also taken in the form of a proportional voltage can. The liquid flow is then combined again with the main flow of the eluates. The measurement voltages of the polarimeter and the refractograph are entered into an analog computer (Zeiss) which uses a multicolor recorder to reproduce the concentration of glucose and fructose as a continuous elution diagram.

The analog computer has the following empirically determined functional ^{equations that are valid for 60 0 C:}

η? = 1.3270 + 1.38 x 10 " ⁴ c - 4.5 x K
[u _c ] f °. = 62.85 + 3.2 x 10 " ³ c + 2.5 ■
[«F] & = - (80.4 + 1.17 x 10" ² C + 8

10- ⁶ c ²
• 10 " ⁶ C ² )

whereby

c = c _G + c _F = total concentration [g / l]

η = refractive index,
[ci _G ] = specific rotation of glucose,
[a _F ] = specific rotation of fructose.

The concentrations for glucose and fructose result from the following relationships:

1000

C "g] - [" rl

E «c] ■ c -

1000
/

[«El - C« _F ]

herein mean

c _c = glucose concentration [g / l],
c> = fructose concentration [g / l],

/ ■ = length of the polarimeter tube in dm,

ti = angle of rotation in degrees.

The measurement of the rotation value α at ¹ 546 mn (// <; line) instead of the usual / V <i "line takes place because of the longer service life and higher light intensity of mercury lamps.

By entering a tax prounuuiiis in tion Anuloizreduier valves are switched, which I let frictions escape one after the other

Glucose, glucose + fructose, fructose, fructose + glucose, glucose, etc. in three separate containers conduct. If the permissible limit concentration of one component is exceeded in the other the solutions are fed into the collecting tank for mixed fractions, which then - mixed with new invert sugar - returned to the separating column. The factions pure fructose and pure glucose solutions are processed separately.

1 sheet of drawings

Claims (6)

Patent claims: 1. Procedure for the immediate analysis of aqueous warm solutions for the content of glucose and fructose, characterized in that the optical refractive index and the optical The angle of rotation is measured with the temperature as constant as possible. 2. The method according to claim 1, characterized in that the temperature of the solutions for the measurements is kept exactly the same or increased slightly. 3. The method according to claim 1 and 2, characterized in that the measurements are continuous take place in the course of a separation process. 4. The method according to claim 3, characterized in that the measured values are a process computer be fed, which prints out the glucose and fructose content, feeds a recorder or otherwise can be continuously recognized. 5. The method according to claim 3 and 4, characterized in that the process computer is the separation process controls or regulates. 6. The method according to any one of the preceding claims, characterized in that the to analyzing solutions are obtained as eluates on a column exchanger.