DE2243397A1 - Determination of tartaric acid in musts or wines - by reaction with vanadic acid, red colouration formed being measured - Google Patents

Abstract

Vanadic acid is added in excess to a must or wine, and the intensity is measured by the red coloration produced by the reaction between tartaric acid and vanadic acid. This reaction is rendered more accurate by precipitating, the excess vanadic acid with Ag NO3 soln. To eliminate side reactions. The determination is pref. carried out in presence of acetic acid. Active coal can be used to clarify the must or wine before the analysis. The method is accurate and rapid.

Description

Patent application Process for determining the tartaric acid content of Liquids, The invention relates to a method for determining the tartaric acid content of aqueous liquids containing tartaric acid »especially wines and musts, in which you get the tartaric acid from a certain amount of the liquid to be examined mixed with such an amount of an aqueous solution containing vanadic acid, that the vanadic acid is present in a stoichiometric excess to the tartaric acid, and the color intensity of the red color complex formed is determined.

An earlier official method for the determination of tartaric acid was based on the poor solubility of the acidic KalSuntsrtrats, This process is very cumbersome To achieve reliable tartaric acid values, one must follow the rules comply very precisely and have trained specialists available, Another method for the determination of tartaric acid in e.g. wines this is in the "Deutsche Lebensmittel-Rundschau" No. 2, February 1961, pages 36 to 41 described method. According to this procedure the tartaric acid is extracted from the liquid containing tartaric acid along with other acids removed with ion exchangers. By eluting the ion exchanger with an aqueous 21 sodium sulfate solution does an eluate get? that is, the organic acids of the one to be examined Solution contains. After the solution has been buffered with sodium acetate, a solution is added of ammonium metavanadate and acidifies the mixture with sulfuric acid, whereby the solution turns red. The color depth must be measured after a short time (1 1/2 minutes) will. The crude tartaric acid content corresponding to the extinction is derived from a calibration curve read.

By means of a correction factor and the total duration of the Tartaric acid has been calculated, you can then calculate the white acid content, this method was, as in "Deutsche Lebensmittel-Rundschau", issue 5 * May 1965, pages 129 to 132 described improved in the meantime. According to this process one oxidizes in part of the eluate add tartaric acid with periodic acid, after adding the ammonium metavanadate solution the respective extinction value is added to the oxidized and the non-oxidized solution The difference between the two values is determined using a calibration curve Tartaric acid content. According to this procedure, the reproducibility is the same as obtained Tartaric acid is quite good. The procedure is currently valid, official analysis regulation and has been recognized as an internationally used method, disadvantage of this The method, however, is to measure the extinction of the red color complex of tartaric acid due to the strong self-absorption of the yellow vanadic acid blank value whose absorption maximum can be measured, one measures at a wavelength at which the The extinction of the red tartaric acid-vanadic acid complex can still be measured sufficiently, however, the extinction of the yellow vanadic acid blank value is only low and can be eliminated by compensation circuitry of the instrument.

(See cited literature, page 130, left column last Paragraph to right column first paragraph), To carry out this method one must Use quite expensive precision instruments, which are usually only well-equipped Laboratories are available, furthermore requires the necessary reprocessing the equipment of a chemical laboratory for the wine or must. She is still very time consuming. Thus, this procedure is in spite of the over previous procedure It is by no means easier to carry out for serial examinations such as those for female Practice of the winemaker or wine merchant is required> suitable.

In the meantime, the time required has been reduced by that one dispenses with the separation of the acids by ion exchangers and the Directly carries out reaction in the previously decolored wine or must.

(Maurer: 'Weinberg und Keller', 1967, No. 24, page 323>.

The reproducibility of the tartaric acid values obtained by this procedure is not very good, and this procedure also requires precision measuring instruments This process has been improved to such an extent that one can even use the high tartaric acid content of grape musts still have an accuracy of the tartaric acid content of approx. 0.2 gil, (notification letter for food chemistry and forensic Chemie, 1970, page 14), a disadvantage of this improved process is that also To determine the tartaric acid content, the total acid content must be known here, An object on which this invention is based is to provide a method where the red tartaric acid-vanadic acid complex without prior treatment of the wine or must is produced directly and as soon as possible after formation of the color complex converts the excess vanadic acid into an inactive form is transferred, Such a method has compared to the known method Among other things, the following advantages: 1. As a result of the removal of those used in excess Vanadic acid can be used to determine the extinction of the reddish color complex at its absorption maximum measure with simple and inexpensive measuring instruments, with lower demands Even simple visual gauges can be used to check the accuracy of the results be, 2, Due to the rapid removal of excess vanadic acid, no other ingredients of the sample solution are oxidized, so it no longer comes for the formation of the green vanadium salts which falsify the optical measurement Solutions prepared for absorbance measurement are therefore stable over longer periods of time, Another object of the invention is to provide a method that a much simpler, more accurate and faster determination of the Tartaric acid, especially taking into account the needs and possibilities the professionally untrained and not specially equipped with equipment Practice enables.

The invention consists in that one the tartaric acid content of tartaric acid containing, aqueous liquids, celts, in particular wines and moths, determined by that the tartaric acid from a certain amount of the acidified to be examined Liquid by adding excess vanadic acid to a red dye complex converts and determines the tartaric acid content by measuring the color intensity, the invention is characterized in that the excess before the color intensity measurement Vanadic acid by adding an aqueous silver salt solution to a practically insoluble one Silver salt transferred and the precipitate separates 0 To transfer the excess Vanadic acid in the insoluble silver salt are water-soluble silver salts, In general, you should dissolve at least 1110 moles of silver salt in one liter of water It is preferable to use silver nitrate or silver acetate in aqueous or acetic acid Solution, the amount of silver salt solution to be used depends on its concentration and of the amount of vanadic acid to be removed0 It has proven to be useful To work with an excess of silver salt, you usually work with one Excess of 5 to 10 Z over the stoichiometrically required Menp, e, one can however, work with a larger excess without affecting the feasibility the procedure is impaired. However, a deficit of silver salt is to be avoided, The process can be carried out particularly advantageously if one is in strongly acetic acid Solution works, It was also surprisingly found that vanadic acid precipitates practically quantitatively in aqueous, strongly acetic acid solution without the Quantitative formation of the red-colored tartaric acid-vanadic acid complex influenced It is therefore possible to first add the acetic acid to the sample solution to be examined Silver salt solution and then the vanadate solution or the acetic acid sample solution first Add the vanadate solution and then the silver salt solution, Obviously the silver vanadate in a strongly acetic acid solution is not as stable as the red Welic acid-vanadic acid complex. In order to achieve the most quantitative possible formation of the red Tartaric acid-vanadic acid complex on the one hand and as extensive as possible on the other Elimination of the Achieving silver vanadate is preferred to work in solutions> which in the final reaction state have an acetic acid concentration of at least 5 Full preferably between 10 and 20 vol, Z, due to the precipitation of the im Excess vanadic acid applied to tartaric acid (preferably already at the time the formation of the red color complex during the addition of the vanadate solution to the acetic acid silver salt Sample solution) is the formation of colored complexes with others in the wine or must acids contained and also the oxidation of other ingredients with formation green-colored vanadium salts largely suppressed, as liquids containing tartaric acid z, B, wine or mole, usually naturally more or less strongly colored it has been found to be useful to select these dyes before measuring the Remove absorbance. It was found that these dyes should be removed Activated carbon is particularly suitable, Other substances with a large surface such as diatomite, Aluminum oxide and polyamide powder (Wohm DC) decolorize in acetic acid solution zs red wine not, aluminum oxide and polyamide powder absorb the red tartaric acid-vanadic acid color complex, As a result, the extinction values of the solutions to be examined are found to be too low.

This effect was not observed with diatomaceous earth. At work with activated charcoal it is particularly advantageous in one strongly acidified with acetic acid Solution to work, in general you work in a 10 to 35% solution, preferably in a 25 to 30 point solution, this omission achieves that the active carbon sites against the acid groups are preferably acetic acid are occupied and practically no more tartaric acid can be bound practical implementation of the method is given to the mixture of sample solution and Acetic acid silver salt solution to the activated carbon before adding the vanadate solution, When adding the vanadate solution, the excess amount of vanadate, which is not required for the formation of the red tartaric acid-vanadic acid complex, precipitated as silver vanadate the activated carbon and the silver vanadate removed. Possibly existing colloidal Silver vanadate and silver halide are retained on the activated carbon.

The required amount of activated carbon depends on the nature from the given color depth of the sample to be examined. In general, each milliliter is sufficient Sample solution 0.2 to 0.5 grams of activated charcoal0 This amount should not be used as an exception what can be determined by a simple manual experiment can suffice without Impairment of the result also more activated charcoal can be applied0 In the case of the Execution of the method according to the invention does not have to be in a specific order Addition of the solutions must be observed 0 So you can e.g. First add acetic acid, then insert the active colile, for this purpose add the vanadate solution and then add the silver salt solution and filter off0 According to another procedure, the vanadate solution is first added to the acetic acid solution, then add the silver salt solution or vice versa and then add the sample solution Activated carbon and filtered, the easiest and fastest way of working is to that a strong acetic acid silver salt solution is added to the sample to be examined and then the vanadate solution is added, then, if necessary after adding the activated charcoal, filtered off and the absorbance measured, Example 1 The example is standardized and tailored to the determination of tartaric acid content, as used in practice Crying or grape musts are to be expected, The tartaric acid content of such liquids are in the range of up to 10 grams per liter, by changing the respective concentrations of the individual reagents or by increasing or decreasing the amount of to The tartaric acid content can be determined in a simple manner by examining the liquid sample determine from the analysis result, with the standardized determination method the following solutions are used for the implementation: Solution 1: n / 10 molar silver nitrate solution in 30% acetic acid, preparation: 17.0 grams of silver nitrate are placed in a 1 liter electric flask dissolved with about 200 ml of distilled water0 300 ml of glacial acetic acid (mlndeaten 99 Xig) given and with distilled water at 20 degrees Celsius filled up to the mark.

Solution 2: Buffered alkaline ammonium monovanadate solution, preparation 10.0 grams of ammonium monovanadate are weighed into a 1 liter volumetric flask and by adding 150.0 ml of nil sodium hydroxide solution at room temperature 208 ml of a 27% sodium acetate solution are added.

and then with distilled water at 20 degrees Celsius to the mark made up, preparation of the 27% sodium acetate solution, 270 grams of sodium acetate siccum are dissolved in a 1 liter volumetric flask with distilled water and used for Brand replenished.

In these solutions, the concentrations are in relation to one another It is true that from the calibration curve drawn up as follows in compliance with the working instructions the grams of tartaric acid per liter of the liquid under investigation can be read off directly, Setting up the calibration curve: Calibration solutions are prepared with distilled water which contain the following amounts of tartaric acid per liter: 0.2; 0.4; 0.6; 0.8; 1> 0; 2.0; 3.0; 4.0; 5.0; 6.0; 7.0; 8.0; 9.0; and 10.0 grams, three milliliters each of the calibration solutions are placed in 200 ml Erlenmeyer flasks, 15.0 ml of the solution are left in each case 1 and swivel slightly o On a test tube rack, prepare 14 Test tubes, which have a turmeric level at 5 ml, have funnels and funnels on them placed in these folded filters (e.g., Selekta 595 1/2, diameter 12.5 cm), others 14 test tubes or Erlenmeyer flasks (50 ml) are provided, now there add to the mixture of the sample solution in the 200 ml Erlenmeyer flask with solution 1, add a level teaspoon of activated charcoal, swirl for a few seconds vigorously and adds 15.0 ml of solution 2 with constant vigorous swirling, then the contents of the flask are immediately placed on the folded filter and about 5 mol of filtrate are left in The test tube is passed through which are discarded0 Then changes place the funnel on an empty test tube or on the 50 ml Erlenmeyer flask over and catches the rest of the filtrate to 0 When all the filtrates are present (the filtrates maintain their absorbance value for several hours), their absorbance values are measured against an empty cuvette, which is filled with distilled water, at 530 nm. The The layer thickness of the cuvette is usually 1.0 cm. It can vary depending on the one used The measuring instrument may be thicker or thinner. The absorbance values thus obtained will be now plotted graphically against the corresponding concentrations, one obtains such a straight line that approaches zero when the tartaric acid content is below 1.5 grams / liter is curved towards, Example 2 3.0 ml of an untreated grape must are in 15 ml of solution 1 are added to a 200 ml Erlenmeyer flask, and a streak is added Add a teaspoon of activated charcoal and swirl the contents. Then under vigorously swirling 15 ml of solution 2 and the mixture on a folded filter The first 5 ml of the filtrate are discarded, the remainder of the filtrate is collected and measured its absorbance against water at 530 nm. From the calibration curve a tartaric acid content of 3.9 grams / liter can be read off, the catfish acid content according to the official determination method was also 3.9 grams / liter, example 3 According to the manner described in Example 2, the tartaric acid content was one Red wine determined, It was determined to be 2.7 grams per liter.

The determination by the official method was also 2.7 grams per liter.

In the same way, the tartaric acid contents of the following samples were taken Use of the mini photometer manufactured by the company Dr, Lange, Berlin determines: according to the invention amtl, rapid method Ortega grape must 5.3 gll 5.3 g / l Müller-Thurgau must 63 gil 6.3 g / l Silvaner must 7.7 g / l 7.6 g / l red wine 1.8 g / l 1.8 g / l white wine 2.0 g / l 2.0 g / l The examples given clearly show that the inventive Method for the determination of tartaric acid compared to the previously known methods represents a substantial enrichment of the technology. It is now possible that the winemaker in the shortest possible time and in large series, especially at the time of the grape harvest, the respective tartaric acid content of the fresh.

can determine harvested must itself. The one he found The tartaric acid content is usually at least as correct as the durcll Use of the previously valid official wine acid determination method. A The main advantage of the method described here is that that, for example, the winemaker can decide in the shortest possible time for a large number of musts can determine whether or by which method he must deacidify the respective must, furthermore he can take measures based on the exact knowledge of the tartaric acid content, This will lead to the deposition of tartaric acid in wines or sects at a later point in time can be avoided.

Claims (1)

Expectations Method for determining the tartaric acid content of tartaric acid containing, aqueous liquids, especially wines and musts, in which the 'tartaric acid is made a certain amount of the acidified liquid to be examined by adding Excess vanadic acid converted to a red dye and measured the color intensity of the tartaric acid content is determined, which is not possible it is important to note that the excess vanadic acid must be removed before the color intensity measurement by adding an aqueous silver salt solution to one that is practically insoluble in water Silver salt transferred and the precipitate removed, 2, method according to claim I, d u r c h e k e n fl 1 e i c h n e t that one is an aqueous silver salt solution a silver nitrate solution used 3. The method according to claims 1 and 2, d a d u r c h g o k e n n-X e i c h n e t that one is an aqueous, acetic acid silver nitrate solution used, 4. The method according to claims 1 to 3, d a d u r c h g e k e n n-1 It is true that one works in acetic acid solution. 5. The method according to claims 1 to 4, d a d u r c h g e k e n n-1 e i c h n e t that one needs the acetic acid solution before measuring the color intensity treated with activated charcoal,