DE1598082A1 - Method for the simultaneous determination of glucose and fructose - Google Patents

Description

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CP. Boehringer & S ^ ehne

GmbH Mannheim 1393 1598082

Method for the simultaneous determination of glucose and fructose

The present invention is a method for simultaneous Determination of glucose and fructose, especially for instantaneous simultaneous determination in warm aqueous solutions. One such procedure is necessary prerequisite to be able to carry out the separation of glucose and fructose on ion exchange columns on an industrial scale (cf. ÜS-Pat. 3.044.904 and registration B 83.I46 IVa / e ^ i). 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 in continuous operation and, above all, too tedious.

It has now been found that you can glucose and fructose in warm aqueous Solutions can be determined at the same time if one considers angle of rotation (α) and refractive index (n) measures these solutions and uses them to calculate the concentration of the components in a manner known per se, although - as our experiments have shown - the final rotation value of glucose-fructose solutions on cooling now adjusts very slowly (0.5-1 hour); see also Browne and

approx
Zerban, Sugar Analysis, 3rd Edition, John Wi] ey & Sons Inc. 1941, p. 293. A rapid measurement of the glucose / fructore content of warm aqueous solutions after cooling to the usual measuring temperature of 20 ° is therefore not possible .

Surprisingly, however, it was found that despite the above Difficulties with Glucc.ee and fructose practically without delay, simultaneously medium refractive index and angle of rotation can be determined by using the Measurement of these two physical quantities is not carried out as usual at 20 °, but at the same or higher temperature than the temperature of the original solutions. The setting of the rotation value is then carried out so quickly, that the measured values can even be used via an automatic computer (e.g. analog computer) for the automatic control of the separation column.

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This result could not be foreseen and is based on a previously unknown effect for which there is still no explanation: If you try to determine the temperature dependency of the rotation value of fructose, you need more than an hour of waiting time for each munching point before a sets a sufficiently constant rotation value - except that it is a matter of fructose solutions which have previously been cooled from higher temperatures to the measurement temperature. If, on the other hand, the fructose solution is heated from a lower temperature to a higher measurement temperature, the rotation angle is surprisingly practical This finding made it possible for the first time to determine glucose and fructose simultaneously in warm aqueous solutions by measuring the angle of rotation (α) and the refractive index (n) followed the described V / eg,

1.) as the above-mentioned effect of adjusting the rotation value of the fructose is unknown was and

2.) because it is of course a painstaking job (instead of the one in the Literature existing values for 20) to include new calibration values for higher temperatures, to determine function equations from the calibration values and calculate nomograms from them.

To carry out the process according to the invention, the angle of rotation and the refractive index are measured in part of the warm solution exiting the end of the ion exchange column, which contains varying amounts of glucose and fructose, at the same or slightly higher temperature. In principle, all commercially available polarimeters and refractometers with flow cuvettes can be used as measuring devices for the angle of rotation and the refractive index - the measured values are evaluated in the usual manner using a nomogram. However, it is preferable to use continuously registering polarimeters and refractories that can be easily thermostatted, in which the solution to be measured is returned to the main stream of the separating

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liquid can be fed into the column. This continuous Devices generally also allow the measurement result to be used as a Proportional voltage to be taken, vrmit both a program-controlled Analog computers as well as multi-color posters can be fed.

Of course, the inventive method is not just for analysis the eluates of invert sugar solutions separated on ion exchangers (according to TJS-Fatent 3. ^ 44.904 and our Anaeldunr Aktenzeicl en r 83 146 IVa / 69i suitable, but principally for the analysis of all technically occurring warmths Sugar solutions.

In the following examples iBt d.is erfinduhfrKgprtäspc method explained in more detail!

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Discontinuous rapid determination of glucose and fructose in eluates

an ion exchange column

The invert sugar solution (cf. US Pat. 3.C44.904 and application file number B 83 146 IVa / 89 i) emerging at the end of a cation exchange column loaded with calcium ions, more or less separated into glucose and fructose, is partially over a polyethylene tube as short as possible 1.) through a polarimeter (Perkin Elmer) and 2.) through a refractometer (Zeiss) 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 nomography (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 ^r ; Glucose and fructose emerge largely separately from the column. Fractions that predominantly contain one component are collected separately and processed into fructose or glucose. ' Fractions which still contain considerable proportions of both components are combined with the original invert sugar solution and subjected to another chromatographic separation.

For comparison, the auo leaving the column sugar solution is passed before entry into Keßgeräte through a cooler and thus atcekühlt in exactly 2O ^U C. All ^ ^r> minutes be read refractive index and optical rotation and evaluated by means of a 2 'C calculated Nomcgramms. The values for glucose and fructose are drawn in a diagram as just described (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 the determination of fructose and glucose shows that: ec are clearly false indications that are based on the too slow setting of the final rotation value of the fructose.

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Example 2

The one operated at 55 ° C. as in example 1 of the main stream of the eluates Chromatography column branched off part of the Zudkerlb'sungen is in front the measurement by heating a thermostatted water bath to exactly 60 C, From the measured values for refractive index and angle of rotation using a nomogram The values determined for glucose and pruotose result in a similar elution diagram like fig. 1.

Example 5 Continuous sonell determination of glucose and fructose in eluates of Ion exchange columns

A partial flow of the 60 ° C. exiting at the end of an ion exchange column warm eluate is injected through a polyethylene tube that is as short as possible continuously registering polarimeter (Zeiss) and a continuously registering refractograph (Zeiss), in which the measured value also can be taken in the form of a proportional voltage. Initially end the liquid flow is combined again with the main flow of the eluates. The measuring voltages of the polarimeter and the refractograph are an analog Computer (Ζθιββ) entered, the concentrations of glucose and fructose with the help of a multicolor recorder from the continuous elution diagram reproduces-

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The analog computer has the following empirically determined puncture equations that are valid for 60 C:

n ^ ° = 1.3270 + 1.38. 10 ^"4 c -. 4.5 1O ~ ⁹ c ²

^ ^{= 62 '85 + 5} ' ^{2 '10} " ³ ° ^{+ 2} ' ⁵ * 1Ο" ⁶ ° ²

- - (80.4 + 1.17. 10 " ² c + 8. 1O" ⁶ _C ² )

Where c = c »+ Cp = total concentration [g / l] η = refractive index,
[ctg] = spec. Rotation of the Oluaoee '[a_] = spec. Rotation of fructose

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

₇ ,]. c + 1000 . α P -j-

[ a ]. c - 1υ ^ 0 . a
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here mean Cp = glucose concentration [g / l]

Cp = pructose concentration [g / l]

1 = length of the folarimeter tube in dm-

c £ = angle of rotation in degrees

The measurement of the rotation value α at 546 nm (Hg line) instead of the usual Na _ line is done by:
of mercury lamps.

Na ^ line occurs because of the longer service life and higher light intensity

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By entering a control program into the analog computer, valves switched, which each successively occurring fractions glucose, Qlucnse + Fructose, Fructose, Fruo'tos »+ Glucose, Glucose ... etc. in three Conduct separate containers * If the permissible limit concentration is exceeded one component in the other, the solutions are fed into the seed tank for mixed fractions, which then - with mixed with new invert sugar - again passed through the separation column. the Fractions of pure fructose and pure glucose solution are separated worked up

Fig. 1) Nomograam for 60 °.

Fig. 2) ElutionediagraDon Glucose-Fructoae measured at 60 and

evaluated with the help of the 60-lioiiogram c. Fig. 3) Eluticmadiagraflsm Gluocse-Fructose measured at 20 ° and evaluated with the help of a 20-iota ^ grame.

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Claims (6)

Claims 1.) Method for the simultaneous determination of glucose and fructose in warm aqueous solutions, characterized in that one angle of rotation and refractive index of these solutions and from this in an eich known In other words, the concentration of the components is calculated. 2.) Process according to claim 3, characterized in that one di » Taking measurements at the same or higher temperature than the temperature of the original solutions. 3.) Process according to Claims 1 and 2, characterized in that as warm aqueous glucose / pructose solutions remove the eluates from an ion exchanger separated invert sugar solutions is used. 4 «) Process according to Claims 1 to 3, characterized in that one polarimeter and refractometer with flow cuvettes used for measurement. 5.) Process according to Claims 1 to 4, characterized in that one evaluates the measured values by means of a nomogram. 6.) Process according to Claims 1 to 3, characterized in that one continuously registering polarimeters and refractographs are used for measurement, in which the measured values in the form of proportional Voltages can be taken. 7 «) Process according to claims 1 to 3 and 6, characterized in that one feeds the measured values to an automatic computer. BAD ORKSiNAL 009815/1552 θ.) Method according to claim 7 »characterized in that the results of the computer can be used to control the entire system. 9 «) Method according to claim 7, characterized in that the results of the computer by a multicolor pen continuously in the form of a Diagram can be reproduced. £ AD ORIGINAL 009815/1552 Blank page