SU1050363A1 - Membrane of ion-selective electrode for determining nitrite-ion - Google Patents

Abstract

. MEMBRANE OF IONOSELECTIVE ELECTRODE FOR DETERMINATION OF NITRATION, containing a liquid ion,:.::. A mannitric in nitrite form and an organic additive dissolved in nitrobenzene, which is so that, in order to improve the stability and accuracy of the determination of nitrite ion in complex salt solutions, the palladium complex is used as an ion exchange ion ) with 2,2-dysi-5-methylazobenEOL, tetraphenylphosphonium and nitrite ion, and as an organic additive, capric acid amide with the following amounts of components, mg; Palogad complex 50-80 Capric acid amide31.5-5Q 5 4 Nitrobenzene1210-1940

Description

The invention relates to the field of analytical chemistry and can be used by chemical and food industry enterprises in the practice of scientific research. Nitrite is widely found in soils and chemical technology. Knowledge of its concentration (activity) in complex saline solutions is often necessary when conducting a number of technological processes. However, in some cases when using ion-selective electrons. of the genera that do not differ in selective interaction in the membrane phase, selectivity with respect to nitrate, which usually accompanies nitrite ion, is not achieved. The liquid ion-selective on the seismic membrane is known;

Neither nitrite ion. The membrane consists of a 0.1 M solution of methyltrioctylammonium nitrite in decanol with the addition of up to. , 20% n-tert-octylphenoosao However, such an electrode does not have sufficient selectivity to the nitrate ion, in the presence of often accompanying eNry nitSA) rat-ion O OJ

 The closest in technical essence and achievable results

; to the proposed membrane is a membrane of the ion-selective electrode for determining the nitrite ion, containing a liquid ion exchanger in a nitrite form and an organic additive. The ionic associate methyl is used as the liquid ion exchanger. tricaprylammonium nitrite (1-0.5) 1 SGm dissolved in nitrobenzene with an organic additive, which uses (1-0., 5) -.10 M of deschamine and (2-1) and the Pd (II) complex with 2.2 -dioxy-5-methylazobenzene. This membrane is characterized by sufficient selectivity, but the angle of inclination of the electrode function and its reproducibility are rather low, which makes it difficult to use for direct potentiometric determination of nitrite ions. The purpose of the invention is to increase the stability and accuracy of nitrite ion determination. in complex salt solutions while maintaining ii selectivity to the nitrite ion. This goal is achieved by the fact that in the membrane of an ion-selective electrode containing a liquid ion exchanger in nitrite form and an organic additive dissolved in nitrobenzene, the pall complex is used as the liquid ion exchanger. d (P) with 2,2-dioxy-5-methylazobenzene, tetraphenylphosphonium and nitrition, and as the organic additive is capric acid amide, using the following amounts of components, mg: Paasadi complex 50-80 Capric acid amide 31.5-50, 4 Nitrobenzene1210-1940 A liquid membrane is prepared by dissolving 50-80 mg of Pd complex (ll with 2,2-dioxy-5-methylazobenzene, tetraphenylphosphonium and nitrite-ion in 1-1.6 ml of nitrobenzene, previously saturated with amide of capric qiata, which increases electrode stability (amount of amide taken and capric acid corresponds to 31.5 mg / ml.) The drawing shows a graph illustrating the dependence of the emf on concentration.

0.04 M NaCl

AgCl, 1M KC1

Membrane

Ag

0.04M NaNOij

Structurally, the electrode consists of a caprolon body with a membrane of porous Teflon impregnated with nitrobenzene solution. A solution is placed inside the case.

Investigated

1ZhS1, AgCl solution

and internal reference electrode. Standard flow-through chlorine silver electrodes EVL-1U of the Gomel plant 3 are used as external and internal reference electrodes. The Ed (II) electroactive complex is synthesized using the following procedure. To a 2 ml solution of palladium (II) hydrochloric acid (10 mg / ml) was added a solution of 2,2-dioxy-5-methylaobenzo, (40 mg) in acetone (4 ml) and boiled for 20-30 minutes . Then a saturated aqueous solution of hydrochloric acid neutralization is added, 2 ml of 5 M NaiNO are added, and a solution of tetraphenes phosphonium chloride (50 mg) in benzene is formed. The resulting crystal-red color turns into a benzene solution. The organic phase is separated, filtered, and purified from organic impurities on a chromatographic column filled with silica gel. When chloroform is used as eluent, an excess of 2,2-dioxy-5-methylazobenzene is removed: the pshadi (II) complex remaining at the start is added with acetone. Oluate is evaporated and the dried complex is used to prepare the membrane. On the day of the regeneration of the palsadi, the used column was washed with an aqueous: cetonic ammonia solution. The composition of the prepared liquid membranes is given in table. 1. As can be seen from the table. 1 the slope of the electrode function is maximum when the concentration of the complex is 51-80 mg / ml. Concentrations of organic additives in the membrane should be as Bbmie as possible. It is proposed to use T-saturated solutions in the membrane, which additionally facilitates the preparation of these membranes. Preparing solutions of comlex hexane with a concentration of more than 80 mg / ml is not possible, and solutions with a concentration of less than 50 mg / ml. A decrease in the angle of inclination of the electrode function is shown. To remove electrode characteristics, TfiK used a galvanic circuit: 5 measuring equipment. To prevent mixing of the solution from the reference electrode and the internal solution adjacent to the organic phase, a plug of filter paper is used. Before operating, the electrode is balanced by holding for an hour in or 10 M NaNOg solution. The EMF values are measured by the ORION 810A digital potential; the linear impedance impedance is the dependence of the emf on concentration (activity) / comp. J in a range of 10 -10 M NaNOjC with an electrode slope of 47 mV / p. NOg. (Fig. O. After working in concentrated solutions, the calibration curve shifts in a nonlinear region. When operating in the 10 M NaNO interval, the electrode function is ± 2 mI, and the calibration curve does not work for 8 h of L-shift. The membrane life is not less than 1 week. The selectivity was estimated in pure 0.1 M solutions of sodium salts of the corresponding anions. For the calculation, Nikolsky equation was used, where is the constant value, the slope tangent of the electrode function, X is the selectivity constant. Yes of the following electrode, the following selectivity series was obtained: СЮ N02 Вг СГ NOj Sof 1 СГ «3 с 10г | Selectivity constants. U,% r..KH С1 К,. WOi к -: г N0, 10-3: LiO 3 It should be noted that rhodanidion removes the membrane from the system, and the selectivity constant for sulfate ion is very small. The proposed membrane for the ion-selective electrode has a high selectivity to nitrite ion and sufficient stability of the potential. The tangent of the slope of the electrode function is 47 mV / p N0, and in the well-known electrode, this figure was 30 mV / p NO. Moreover, according to the obtained characteristics of the proposed electrode, it can be concluded that it allows one to work much, more precisely, of the known. This makes it possible to measure the concentration (active) of nitrite ion in complex salt solutions directly by potentiometers. The method is simple to implement and express, does not require complex equipment. An ISE prototype was taken as an object of comparison, which is currently undergoing laboratory testing. Comparative characteristics are given in table. 2. In the same place, a comparison is made with ISE, described as analogues. From the table. 2 data shows an improvement in reproducibility and an increase in the tangent of the slope of the electrode characteristic. In addition to Toroj, the data presented in the graph shows a noticeable increase in the accuracy of the proposed electrode.

Composition of liquid membranes

Table 1

Claims (1)

. ION SELECTIVE ELECTRODE MEMBRANE FOR NITRITION DETERMINATION, containing a liquid ion exchange exchanger in nitrite form and an organic additive dissolved in nitrobenzene, with the aim of increasing the stability and accuracy of determining the nitrite ion in complex saline solutions, a liquid palladium (P) complex is used as a liquid ion exchanger. with 2,2 ^ -dioxy-5-methylazobenzene ,, tetraphenylphosphonium and a nitrite ion, and as an organic additive, capric acid amide with the following amounts of components, mg: Palladium complex 50-80 Amide caprine acid 31.5-50.4 Nitrobenzene 1210-1940