SU1670601A1 - Method for photometrically determining mercury - Google Patents

Abstract

The invention relates to methods for the photometric determination of mercury and can be used to increase the sensitivity and determine mercury in the range of 10 ^-6 - 10 ^-7 M in natural and waste waters. The method consists in the preliminary application of the organic p-phenolazo-3-aminorodanine reagent onto tablets of sulfonated styrene copolymer with divinylbenzene on a polyacrylonitrile basis, containing, in wt%: copolymer 45.0 - 55.0

polyacrylonitrile 45.0 - 55.0 (weight of tablets 9-11 mg), by immersing the reagent in a solution (0.5-2.0) ^. 10 ^-5 M. The conversion to the complex compound is carried out at PH 1. 7 tab.

Description

The invention relates to the field of analytical chemistry, in particular to methods of photometric determination of mercury using an organic reagent, and can be used in the analysis of natural and waste waters, industrial solutions.

The purpose of the invention is to increase the sensitivity and determination of mercury in the interval.

This goal is achieved by the fact that according to the method of photometric determination of mercury using p-phenolazo-3-aminorodanine as organic reagent, the reagent is fixed on a solid polymer base in an amount of 5-10 - 2-10 M / g and the determination is carried out at pH 1, and as a solid polymer base, polyacrylonitrile fibrous material disks are used, filled with finely dispersed sulfonated styrene copolymer with divinylbenzene, weighing 9–11 mg, with a thickness of not more than 0.5 mm. The polymer base is characterized by the following ratio of components: sulfonated copolymer 45–55%, polyacrylonitrile fiber 45–55%.

Mercury interacts with p-phenolazo-3-aminorodine (IMFA-3-AR), fixed on a polymer base, in the acidity range of 5 M H2SO4 - pH 5 to form a colored complex compound (color transition from yellow to crimson). The reflection of the IMFA-3-AP disk in the visible region of the spectrum decreases. The maximum change in reflection is observed at 570 nm. The change in reflection at 570 nm is taken as the analytical signal of IMFA-3-AR for the presence of mercury (II). The reaction of IMFA-3-AR with mercury develops when the disks are kept in a mercury solution at pH 1 for 3-5 minutes. The interval of detectable concentrations is 6–60 µg / 100 ml or 0.06– 0.6 µg / ml. S Ю 7–3 M, the detection limit calculated by the 3S criterion is equal to 1 X10 M.

WITH

ABOUT

VI o o o o

The stable structure of the substrate (carrier) and the sufficiently high strength of the reagent complex with mercury ensure effective removal of traces of mercury from large volumes of solutions and highly sensitive determination. By increasing the role of the steric factor, the difficulty of forming complexes saturated with a reagent, the selectivity of the determination of mercury is increased. By reducing the strength of the complex of mercury with SG in the transition to less acidic media (from 14 M NzRSm to pH 1), the selectivity of the determination of Hd in the presence of SG increases dramatically. Characteristics of the proposed method are given in table.1.

Sorbents of different nature were used as carrier for immobilization of p-phenolase-3-aminorodanine: Filler Analytical signal Strongly basic anion exchange resin, No color reaction AV-17 of

CopolymerPerfectly fixed with styrenol with vinylbenzene reagent

Strong acid Strong fixation of sulfonium cationite, color reacted co-SOH (I) styrene dimer with di- Color transition vinylbenzene yellow malinova Slightly basic No color reaction anion exchanger, A-5

Strong retention of the reagent on the carrier and the sensitive reaction of the immobilized reagent were found only in the case of a sulfonated copolymer of styrene with divinylbenzene.

The effect of the acidity of the analyzed solution on the magnitude of the analytical signal, V 100 ml, Snd 310 m: Acidity R 570 nm

5 M NzRSm (N25Sm) 0.030

3 M, 053

2M, 060

1MM, 062

0.5, 060

pH 1 (Nzrsm, H2S04) 0.065 pH 20.064

pH 30.048

pH 40.045

pH 50.028

Carrying out the analysis at pH 1 ensures that the maximum value of the analytical signal AR570 and the maximum system stability are achieved (the reagent is firmly held on the carrier).

The influence of the composition of the polymer base and the content of the reagent on the characteristics of the immobilized reagent (Table 2) was studied. The highest response sensitivity with high accuracy of analysis and system stability is achieved with

the following composition: 45-55% sulfonated copolymer of styrene with divinylbenzene, 45-55% polyacrylamide nitrile fiber. The optimum content of the reagent on a solid carrier (0.5 - 2) M / g. AT

In this interval, the magnitude of the analytical signal is maximum. The mass of the disk 9 - 11 mg with a thickness of not more than 0.5 mm was found to be optimal. It should be noted the interdependence of these indicators. With increasing

5 or by decreasing the mass of the disk at a constant thickness, the analytical signal decreases in Nd (II) (Table 3). An increase in the disk thickness of 0.5 mm also leads to a decrease in the analytical signal.

0 Only a combination of all the signs: p-phenolazo-3-aminorodanine in the amount of (0.5 - 2) 10 M per 1 g of solid carrier, which is a polyacrylonitrile fiber, filled with sulfonated Co5 polymer of spirol with divinylbenzene; nitrile 45 - 55%: 55 - 45%, in the form of a disk with a mass of 9–11 mg and a thickness of not more than 0.5 mm with a pH of 1, ensures the maximum sensitivity, selectivity and expressivity of the analysis (Table 2).

Immobilization of p-phenolazo-3-aminodanine on a polymer base.

Starting material to obtain

5 of the polymer base is a sulfonated copolymer of styrene with divinylbenzene in the form of a fine powder with a particle size of 5 to 10 µm on a polyacrylonitrile substrate of composition: 45-55%

0 copolymer, 45-55% polyacrylonitrile, obtained in the process of forming polyacrylonitrile fiber from a suspension containing polyacrylonitrile and a copolymer in DMF.

5 From the plates of wet fibrous material cut discs no more than 0.5 mm thick, weighing 40- 60 mg (in terms of dry material 9-11 mg). The disks are washed with 50 ml of 0.1 M to turn into the H-form.

0 HCI. Immobilization of p-phenolazo-3-aminodanine is carried out by immersing the disk in a beaker with 10 ml of a 0.05% aqueous ethanol reagent solution. The discs are removed from the solution and washed with distilled water and stored in a wet state. The content of the reagent on the carrier is determined spectrophotometrically by the difference in the absorption of the reagent solutions before and after incubation of the disk. Disk immobilized l-phenolazo-3-aminorodanina

At pH 1 it is colored bright yellow. The deviation in the values of diffuse reflection coefficients for individual disks does not exceed - -3%. The discs are stable in neutral and weakly acidic media.

PRI me R. In 100 ml of the analyzed solution containing 6-60 µg Nd (II), acidified with H2SO4 or HzP04 to pH 1, make a disc with immobilized reagent. With weak stirring, incubated for 3-5 minutes. The disc reflection is then measured at 570 mm. The content of Nd (II) is found from a calibration graph constructed under the same conditions.

The main advantage of the proposed method in comparison with the known one is the high selectivity of the determination of HL (II). The selectivity of the reaction of IM-FA-3-AP with Nd (II) rises almost by an order of magnitude and higher compared with the use of n-phenolase-3-amyrodanine (prototype, type) in solution (Table 1). 1-3 101 times the excess of Cr (lll), Zn, Pb, Nl, Co. will not interfere with the determination of M mercury. Cd, 1-102-Cu, 6 102-Fe (III). The selectivity with respect to chloride ions increases dramatically, almost n order of magnitude, which is probably associated with a decrease in the strength of the complex during the transition from 12 M HzROz to crN1.

The proposed method is tested on river water entering the waterworks. The test results are presented in table 4. The test showed the possibility of using the proposed method for the direct rapid determination of Nd (II) at a concentration level of 0.06-0.6 µg / ml.

Below are the comparative characteristics of the proposed method with the prototype:

Reagent content:

on 1 g of the carrier on the disk Mass of the disk Thickness of the disk Method of immobilization

(0.5-2) (0.5-2) 9-11 mg Not more than 0.5 mm

Keeping the discs in a 0.05% reagent solution for 5 minutes

The method is carried out - Keeping the disc immobilized reagent in the analyzed

a solution with a pH of 1 for 3-5 min. Change in reflection of a disk at 570 nm

The interval of determination is 0.06-0.6 µg / ml or divisible concentration of 3 () M concentrations. Detection limit is 0.02 µg / ml or

Reproducibility, 3 h 0.05 - 0.08 Sr In comparison with the known ones, the proposed method is sensitive, selective and express, as it allows a direct determination of Hd (II) at a content of 0.06 µg / ml. Mine stage of pre-concentration. The simplicity and reproducibility of the method of immobilization of the reagent, as well as the detection of disc color change using reflective spectrophotometry, provide high accuracy of determination.

The following advantages of the method in comparison with the prototype can also be noted: the reagent consumption is reduced - in the usual spectrophotometric method 0.5 mg of reagent is consumed per definition, in the proposed method 0.013 mg; the consumption of HFWD is reduced — in a conventional spectrophotometric procedure, 20 ml of HFWW are consumed per determination. In the proposed method, the determination is carried out at pH 1 (the aggressiveness and viscosity of the medium for the reaction are reduced.

Claims (1)

The invention of the method of photometric determination mercury (II), including its transfer to a complex compound with an organic reagent n phenolazo-3-aminorodine in an acidic medium, characterized in that, in order to increase the sensitivity and determine mercury in the range of 10 - 10 M, the organic reagent is preliminarily applied in an amount (0.5 - 2.0) 10 M / g on a solid sulfated styrene copolymer with divinylbenzene on a polyacrylonitrile basis, containing, in wt.%: Copolymer - 45 - 55; polyacrylonitrile, 45–55, taken in the form of tablets weighing 9–11 mg, and converted into a complex compound at pH 1. Table 1 , 12 MN, P04 10 0 mcg / ml The content of the component "- nentov in the original polymer base, mas% polymer polyacryl "nitrile thirty 70 A5 55 50 50 pH 1 3 "-5 0.06 "-0.6 µg / ml table 2 The content of p-phenolEo "" -3-aminorO - danina, M / g-Yu 5 0.021 0.037 0.043 0.052 0.040 0.038 0.064 0.069 0.061 0.041 0.037 0.063 0.069 0.060 0.052 0.031 0.060 Note. Continuation With an increase in the content of the sulfonated copolymer in the initial basis of 55%, the mechanical nature of the material decreases. T a b faces 4