DE19608808C2 - Sensor, its use and method for producing a dye for the sensor - Google Patents

Description

The invention relates to a sensor according to the preamble of Claim 1, its use according to claim 2 and a procedure to produce a dye for the sensor according to An saying 3.

A sensor of this type is from the publication "An opto chemical sensor for Cd (II) and Hg (II) based on a prophyrin im mobilized on Nafion® membranes "by A. Morales-Bahnik, R. Czolk, J. Reichert and H. J. Ache, Sensors and Actuators B, 13-14 (1993) 424-426. This sensor is on one Plexiglas pane a layer of the Na cation exchanger fion® applied. In its manufacture, the disc with the Nafion layer in an aqueous solution of the dye 5,10,15,20-tetra (4-N-methylpyridyl) porphyrin with metal ions form a chelate complex and four positive charges wears, immersed. The cation becomes obvious Load the exchanger with the porphyrin. The sensor with the with Porphrin-loaded cation exchanger takes from a sample solution metal ions, whereby its optical adsorp change properties. The sensor is used for the analyti detection of cations, in particular of Cd (II) - and Hg (II) ions are proposed.

A similar sensor is described in DE 43 32 512 A1.

The publication: "Activation Parameters for the Reaction of Aquocobalamin (Vitamin B _12a ) with Small Anionic and Neutral Ligands" by HM shows that metal chelate complexes with the corrin backbone are suitable for the detection of cyanide and hydrogen cyanide (hydrocyanic acid) Marques, Dalton Transactions 1991, 339-341. Studies on the determination of thermodynamic parameters of vitamin B ₁₂ cyanide complexes in the publication "the Influence of Chelation in Determing the Reactivity of the Iron in Hemoproteins, and the Cobalt in Vitamin B ₁₂ " by P. George, DH Irvine , SC Glauser, Ann. NY Acad. Sci., 88, 1960, 393 reports. The publication "Anion-Selective Electrodes Based on a Hydrophobic Vitamim B ₁₂ Derivative" by S. Daunert and LG Bachas in Analytical Chemistry, Vol 61, No. 5 (1989) 499-503 describes attempts to produce polyvinyl chloride (PVC) membranes from a derivative of vitamin B ₁₂ and the hydrophobic matrix and to use these membranes as anion-sensitive electrodes.

The invention has for its object a sensor to propose the type mentioned, ent ent a dye holds that with the cation exchanger a very stable Ver Binding is received, so that a high long-term stability of the Sensor results. It is also intended to be used for the sensor and a method for producing the dye is proposed will.

The task is characterized by that in claim 1 Features of the sensor, by the use according to claim 2 and solved by the method described in claim 3.

The sensor according to the invention consists of the transparent Trä on which the layer of the one loaded with the dye Cation exchanger is applied.

A plexiglass pane is suitable as a transparent support. The fixed connection of the plexiglass pane to the layer of Cation exchanger can be prepared in that the Plexiglass slightly dissolved with an organic solvent is, which after drying the solvent the Verbin is made to the layer of the cation exchanger. Al Alternatively, a glass pane can also be used as a transparent support be used. In this case, the link between the Glass pane and the layer of the cation exchanger  provides by the surface with organic groups functio nalized or with a mixture of sulfuric acid and what treated with peroxide.

While in principle all cation exchange materials are suitable for the sensor according to the invention, provided that they are suitable for Ab sorption measurements transparent or for reflection measurements are white reflective, the exchange material is Na fion® preferred. With the trade name Nafion becomes a copo lymer from tetrafluoroethylene and perfluoro [2- (fluorosulfonylethoxy)] propyl vinyl ether.

In the sensor according to the invention, the cation exchanger is loaded with six-fold positively charged cobinamide. The name cobinic acid is the short name of the compound cobinic acid a, b, c, d, e, g-hexa (1- (3-aminobenzyloxymethyl) pyridinium chloride) amide f- (2-hydroxypropylamide) 3, 8,13,17-tetraethyl-1,2,2,5,7,7,12,12,15,17,18-undecamethylcobalt-monoaquo corrin; the structural formula is given in claim 1 and in FIG. 3 (compound I), where R denotes any radicals including hydrogen and L ₁ , L ₂ denotes any ligand.

The main advantage of the dye cobinamide is in that the carrier of the positive charge (which in the sequence Anchor groups are called) an extremely stable connection to manufacture the cation exchanger. The proposed cobin acid amide is therefore also in contact with in long-term operation Solutions of positively charged ions, e.g. B. metal ions, not displaced from the cation exchanger.

The sensor according to claim 1 is particularly suitable for spec Microscopic detection of cyanide or hydrogen cyanide. Although is known per se that corrinoids in the presence of cyanide Cyanide complexes is formed in the sensor according to the invention remarkably, this does not result in this complex formation disturbs that the dye fixes in a cation exchanger  that is not accessible for negatively charged ions without continuing is. By loading the cation exchanger with the Dye change its complexing properties compared to cyanide ions and hydrogen cyanide obviously not disadvantageous.

Absorption spectroscopy can still be done with the sensor Record cyanide concentrations below the ppm range. The sensor is also not very cross-sensitive. In contact with a solution that, in addition to cyanide, contains sulfate, chloride, oxalate, Contains phosphate, carbonate, thiocyanate, iodide and bromide the absorption signal of the cyanide-dye complex is not we considerably influenced.

The dye can be prepared in the following way: The cobinic acid is synthesized by hydrolysis of cobalamin siert. The anchor groups are synthesized in parallel. For this purpose, commercially available 1- (3-nitrobenzyloxymethyl) - pyridinium chloride (NBOP) to 1- (3-aminobenzyloxymethyl) pyridi nium acetate (ABOP) reduced. Finally, the anchor group pen via its amino group to the acid group of cobinic acid coupled. For this, 1 mol of cobic acid and 6 mol of 1- (3-aminobenzyloxymethyl) pyridinium acetate to acid amide vice versa puts.

The invention is described below with reference to 9 figures and Implementation examples explained in more detail.

Show it:

Figure 1 shows the hydrolysis of cobalamin to cobinic acid.

Figure 2 shows the reduction of 1- (3-Nitrobenzyloxymethyl) -pyrido diniumchlorid (NBOP) to 1- (3-amino-benzyloxy methyl) pyridinium acetate (ABOP).

Figure 3 shows the coupling reaction of cobinic acid and 1- (3-aminobenzyloxymethyl) pyridinium acetate (anchor group) to the dye.

Fig. 4 spectra of the complexation of cyanide;

FIG. 5 shows difference spectra complexation;

Fig. 6 is the cyanide signal at various pH values;

Fig. 7 shows the time spectrum of the cyanide-calibration of the sensor;

Fig. 8 is a calibration curve and

Fig. 9 shows the cross sensitivity of the sensor.

example 1 a) Representation of cobalamin-hexacarboxylic acid

The preparation of cobalamin-hexacarboxylic acid from cobalamin was carried out as follows:
500 mg (0.000369 mol; molecular weight: 1355.4 g / mol) of Co balamin (see compound 1 in FIG. 1) were dissolved in 20 ml of 30% NaOH and heated to 80.degree. After 45 minutes, the solution was placed in a digestion bomb with a volume of 25 ml and heated at 180 ° C. for 40 minutes. The solution was neutralized with half-concentrated sulfuric acid and titrated until the color change was purple-orange. It was then back-titrated with sodium carbonate until no more carbon dioxide evolution was observed. The solution was evaporated to dryness on a rotary evaporator and extracted twice with methanol. The solvent was removed on a rotary evaporator and the remaining solid, the cobalamin-hexacarboxylic acid (see compound 2 in FIG. 1), was taken up in water.

b) Synthesis of anchor groups

The conversion of 1- (3-nitrobenzyloxymethyl) pyridinium chloride (NBOP, compound 3 in Fig. 2) to 1- (3-aminobenzyloxymethyl) pyridinium acetate (ABOP, compound 4 in Fig. 2) was carried out by reduction with zinc after the following procedure: 1 g of NBOP (corresponding to 3.562.10 ^-3 mol) was dissolved in 1.5 ml of concentrated acetic acid (glacial acetic acid) in a 10 ml pointed flask and 0.25 g (3.823.10 ^-3 mol) of zinc dust was added. The suspension was stirred for two hours, the color changing from colorless to yellow. Then 2 ml of methanol were added dropwise and 0.25 g of zinc dust was slowly added. After four hours of stirring, a further 0.5 ml of acetic acid and another 0.25 g of zinc dust were added to the suspension. The supernatant clear solution was decanted after stirring for 20 hours and standing for 24 hours, and the remaining precipitate was washed several times with a little methanol and added to the decanted solution. The solution was evaporated in a rotary evaporator and taken up in methanol, leaving poorly soluble zinc acetate as a white precipitate. This extraction is repeated two more times, the precipitate being washed with methanol. The methanolic solution was evaporated in a rotary evaporator and made up with deionized water.

c) coupling reaction

The dye is obtained from a coupling reaction between Co binsäure and the anchor group ABOP obtained. Here rea an amino group with an acid group forms an amide binding.

The reaction equation is shown in Fig. 3. The coupling reaction was carried out according to the following procedure: 10 mg cobinic acid (C ₄₈ H ₇₀ N ₅ O ₁₆ Co; molar mass 1032.04 g / mol; 9.690.10 ^-3 mol) are mixed with 3.6.9.690.10 ^-3 mol = 1744.10 ^-4 mol or 0.048 g ABOP (molar mass: 274.32 g / mol) anchor group added (triple excess). The solution is added to the 0.25 g of 2- [N-morpholino] ethanesulfonic acid (MES; molar mass 195.2 g / mol, 8.5% by weight solution in water) and made up to 50 ml with deionized water. The solution was adjusted to pH 7 with half-concentrated sulfuric acid and mixed with 0.5 g of N- (3-dimethylaminopropyl) -N'-ethyl carbodiimide hydrochloride (EDC, molar mass 191.71 g / mol) and stirred overnight. The addition of EDAC is repeated until there is no visible change in the absorption spectrum.

d) cleaning

The dye was cleaned by gel electrophoresis rese. The excess anchor group migrates in electric field faster than the dye. The yellow one rich that contains the dye was cut out and extracted with methanol. The solvent was in the Rota tion evaporator removed and the residue with deionized water.

Example 2 Manufacture of the sensor

Nafion® served as the carrier for the cation exchanger. A Lö solution of Nafion in a mixture of low, aliphatic Al kohole with about 15 to 20 vol% water on a plexiglass pipetted with a diameter of 10 mm and at a number of revolutions of 3000 revolutions per minute hurls. After one minute the process was repeated; a total of eight layers were applied. After a The Sen was dried for one hour at room temperature sor placed in an aqueous solution of the dye. The tem  temperature of the solution was 40 ° C; drawing up the dye is completed after three weeks.

Example 3 Spectral behavior of that prepared according to Examples 1 and 2 Sensors

In Fig. 4 the complexation of the dye with cyanide is presented. The spectrum of the uncomplexed dye shows an extinction maximum at 446 nm. In the complexed form there are two extinction maxima at 552 nm and at 592 nm. The absorption band shifts into the red spectral range (bathochromic color shift). The difference spectrum is shown in FIG. 5. It shows the change in extinction when sampling with cyanide. At 586 nm there is a clearly positive change in the absorption spectrum, at 446 there is a negative one. The difference in absorbance at wavelengths 586-466 is used as the sensor signal.

Example 4 Influence of the pH value on the sensor signal

Fig. 6 shows the complexation of the dye at various pH values with a constant cyanide concentration. The figure shows that the fastest way to adjust the pH is at high pH values. At a pH of over 10, the complexation is completed in 2-3 min at a cyanide concentration of 1.10 ^-3 mol / l cyanide. The sensor signal is reversible at each of the examined pH values; however, a sufficiently quick decomplexation takes place in the neutral or acidic range. A quick regeneration of the sensor within 2 minutes can be done with an acid solution, e.g. B. with a 0.1 M hydrochloric acid solution.

Example 5 Determination of the calibration curve

To determine the sensitivity, the sensor was sampled with various concentrations. Fig. 7 shows the step increase with increasing cyanide concentrations. A calibration curve was created from FIG. 7, which is shown in FIG. 8. There is an S-shaped course of the calibration curve.

Example 6 Determination of cross-sensitivities

In order to investigate the cross-sensitivity of the sensor to other anions, cyanide was first sampled and then regenerated (see FIG. 9). It can be seen that the dye is empty and reacts to cyanide. The sensor was then sampled at a concentration of interference ions of 1.10 ^-3 mol / l. It was found that with the investigated interference ions chloride, sulfate, nitrate, hydrogen carbonate, phosphate, oxalate, bromide and iodide, no change in the signal is obtained. Subsequently, cyanide was sampled and regenerated. The cyanide sensitivity remains fully intact, ie the interference ions present have not affected the function of the sensor.

Example 7 Long-term stability studies

The stability of the sensor when sampling with deionized Water over a period of a few months does not show any significant change in sensor behavior (kinetics, ampli tude).

Claims (3)

1. Sensor in which a layer of a cation exchanger which is loaded with a positively charged dye with complexing properties is applied to a support, characterized in that the following compound is used as the dye
where R is any radical including hydrogen and L ₁ , L _{2 are} any ligand. 2. Use of the sensor according to claim 1 for spectroscopy detection of cyanide or hydrogen cyanide in a solution solution that is in contact with the sensor. 3. A method for producing the dye for a sensor according to claim 1, comprising the steps:

• a) hydrolysis of cobalamin to cobic acid,
• b) reduction of 1- (3-nitrobenzyloxymethyl) pyridinium chloride (NBOP) to 1- (3-aminobenzyloxymethyl) pyridinium acetate (ABOP),
• c) Coupling reaction between 1 mol of cobinic acid and 6 mol of 1- (3-aminobenzyloxymethyl) pyridinium acetate in such a way that the amino groups of the - (3-aminobenzyloxy methyl) pyridinium acetate form with the acid groups of cobic acid an acid amide.