SPECTROPHOTOMETRIC RESEARCH INTO COMPLEXATION OF TUNGSTEN(VI) WITH O - HYDROXYTHIOPHENOL DERIVATIVES IN THE PRESENCE OF HYDROPHOBIC AMINES Текст научной статьи по специальности «Химические науки»

164 CHEMICAL PROBLEMS 2022 no. 2 (20) ISSN 2221-8688

UDC 543. 42. 062: 546. 77

SPECTROPHOTOMETRY RESEARCH INTO COMPLEXATION OF TUNGSTEN(VI) WITH o-HYDROXYTHIOPHENOL DERIVATIVES IN THE PRESENCE OF

HYDROPHOBIC AMINES

Sh.A. Mammadova, U.B. Abasqulieva A. Z. Zalov, N.A. Novruzova

Azerbaijan State Pedagogical University Uz. Hadjibekov str., 68, AZ1000, Baku e-mail: zalov1966@mail. ru

Received 04.04.2022 Accepted 31.05.2022

Abstract: Spectrophotometric methods were used to study the reaction of complexation of tungsten with derivatives of o-hydroxythiophenol (HTPDs) {2-hydroxy-5-chlorothiophenol (HCTP), 2-hydroxy-5-bromothiophenol (HBTP) and 2-hydroxy-5-iodothiophenol (HITP )} in the presence of aminophenols. Aminophenols used were 2(N,N-dimethylaminomethyl)-4-chlorophenol (API) and 2(N,N-dimethylaminomethyl)-4-bromophenol (AP2), 2(N,N-dimethylaminomethyl) -4-iodophenol (AP3).Optimal conditions for the formation and extraction of mixed ligand complexes (MLC) were found, and the ratios of the components in the complexes established. It revealed that MLC are formed in a weakly acidic environment (pHopt 4.5-5.5). The maximum in the light absorption spectrum is observed at X=460-490 nm. The molar coefficient of light absorption is equal to e = (2.0 -2.8) x 104. Optimal conditions for the formation and extraction of these compounds is the concentration of (1.2-2.5) x 10-3 mol /1 GTP and (2.0-2.8) x10-mol/l AP. The maximum optical density is reached within 5-8 minutes. Tungsten MLC extracts with HTP and AP obeys Beer's law at concentrations of 0.04-3.8 p.g/5 ml. The proposed method was applied to determine Tungsten in steel and in soils.

Keywords: Tungsten, o-hydroxythiophenol derivative and hydrophobic amines, extraction-photometric

method, detection limit, determination.

DOI: 10.32737/2221-8688-2022-2-164-174

Introduction

Spectrophotometric methods [1-5] are among the most precise instrumental methods of analysis for the determination of elements in trace amounts. These methods are remarkable for their versatility, sensitivity and precision. Owing to these methods it is possible to cover a very extensive range of concentrations for the trace analysis of the elements. There are various spectrophotometric methods which suffer from low sensitivity, non-selectivity and complexity in the procedures for the determination of tungsten in trace amounts using thiocyanate, vanadophosphoric acid as ligands [1,3]. Many organic reagents are used as analytical reagents for spectrophotometric determination of tungsten but most of these are not suitable for routine analysis of the metal ion due to one or more of the above drawbacks [1,3,6]. This

circumstance made it necessary to search for new better methods and accordingly,we have synthesized several very effective reagents - o-hydroxythiophenol derivative (HTPDs, L) {2-hydroxy-5-chlorothiophenol (HCTP), 2-hydroxy-5-bromothiophenol (HBTP), and 2-hydroxy-5-iodothiophenol (HITP)} has been used as a complexing agent for tungsten (VI) in the spectrophotometric determination of metal ion to meet the above requirements.

In the present paper, we report results from liquid-liquid extraction-

spectrophotometric experiments on 9 different systems, each of which containing W(VI), a HTPDs and an - aminophenols (AP) {As aminophenole 2(N, N-dimethylaminomethyl)-4-chlorphenol (API) and 2(N, N-dimethylaminomethyl)-4-bromphenol (AP2), 2

CHEMICAL PROBLEMS 2022 no. 2 (20)

www.chemprob.org

(N, N-dimethylaminomethyl) -4-yodophenol for determining tungsten in soils and plants. (AP3) were used}. We suggest new procedures

Experimental part

Reagents and solutions. A standard stock solution (100 mL) of tungsten (VI) containing 1 mg mL-1 of the metal ion is prepared by dissolving an accurately weighed amount (0.179g) of sodium tungstate (A.R) in distilled water. The concentration of the tungsten solution was adjusted gravimetrically by sedimenting tungsten in the form of H2WO4 and weighing WO3 [2, 7]. Lower concentrations at ^g mL-1 (10, 20, 50 and 100) level are prepared by suitable dilution there from.

Chloroform was purified by washing

Cl HCTP pK1=5.10; pK2=

0-3.5 (X=283 nm);

Synthesized compounds were characterized by physicochemical methods: IR [16] and NMR spectroscopy:

HCTP - IR (KBr): 3460 cm-1 v (OH), 2570cm-1 v(sh), 1580 cm-1 v(c6h5); 1H NMR (300.18 MHz, C6D6): 5 5.70 (s, 1H- OH), S 3.40(s, 1H - SH), S 7.05 (s, 2H Ar-H), S 6.25 (s, 2H Ar-H).

HBTP - IR (KBr): 3458 cm-1 v(OH), 2568 cm-1 V(SH), 1550 CM-1 V(C6H5); 1H NMR (300.18 MHz, C6D6): S 5.70 (s, 1H- OH), S 3.40(s, 1H - SH), S 7.05 (s, 2H Ar-H), S 6.25 (s, 2H Ar-H).

HITP- IR (KBr): 3456 cm-1 v(OH), 2578 CM-1 V(SH), 1570 CM-1 V(C6H5); 1H NMR (300.18 MHz, C6D6): S 5.55 (s, 1H- OH), S 3.32(s, 1H- 1SH), S 6.80 (s, 1H Ar-H), S 7.30 (s, 2H Ar-H).

Apparatus. An optimum acidity was created by means of 0.01 M HCl or an ammonium acetate buffer solution and

with conc. H2SO4 and shaking with distilled water followed by washing with a 5% solution of NaOH. Chloroform is used for extraction of W(VI) - HTPDs-AP complex. HTPDs is prepared by reported methods [8] as follows.

Complexing agents may be a dibasic (HCTP, HBTP, HITP, H2L) weak acid, and depending on pH of the medium may be in molecular and anionic forms. Some characteristics of the investigated reagents are presented below:

I

HITP

pK1=5.00; pK2=10.02 0-3.2 (X=290 nm)

controlled using an I-120.2 potentiometer equipped with a glass electrode. The absorbance of the extracts was measured using a KFK-2 photocolorimeter (USSR), a SF-26 spectrophotometer (USSR), equipped with 5 and 10 mm pathlength cells. Muffle furnace was used for dissolution of the samples.

Methods. Portions of a working tungsten solution, 0.1 to 0.8 mL with an increment of 0.1 mL, 1.0-2,0 mL of 0.01 M HCl, and 0.3-0.5 mL of a 0.01 M HTPDs solution were placed in calibrated test tubes with ground stoppers. The mixture was stirred thoroughly for 5 min to reduce tungsten, then 2.0-3.0 mL of a 0.01 M solution of AP was added. The volume of the organic phase was adjusted to 5 mL with chloroform, and the volume of the aqueous phase was brought to 20 mL with distilled water. Following the formation of the hydroxythiophenolate complex of tungsten, it was extracted, and the absorbance

Br

HBTP

10.6 pK1=5.05; pK2=10.4

pH neutral form of existence: 0-3.3 (X=286 nm);

of extracts was measured by a KFK-2 photoelectrocolorimeter at 490 nm.

Results and Discussion

Research into the oxidation state of tungsten. In acidic medium, HTPDs exhibit reducing properties [9-11]. Hence, in the complex formation with HCTP, tungsten (VI) is reduced to tungsten (V) by the reagent itself. This fact was confirmed by ESR spectrometry [11].

Charge of the complex tungsten. The

present study deals with the investigation of W (V) interaction with HTPDs, resulting in the formation of colored complexes insoluble in nonpolar solvents. To determine the sign of the

complex charge, ion exchange chromatography was used: AV-17 anion exchanger in chloroform absorbs a part of solution; the chromatographic column is colored in orange and tungsten is not detected in the filtrate. The anion complex is extracted in the presence of a hydrophobic amine, wherein the complex stability increases , and the color becomes more saturated. To neutralize the charge of the anion complex, aminophenol is used as a hydrophobic amine, which transforms into a aminophenol ion in acidic medium as follows:

OH

CH2N(CH3)2

R

+ H+

c>

OH

+

CH2N(CH3)2

R

Whereas: R = -Cl, -Br, -I

(AP)

(APH+)

The Choice of the Extractant. To

extract complexes, we used CHCl3, C2H4Cl2, CCl4, C6H6, C6H5-CH3, C6H5Cl, W0-C4H9OH, /^o-C5H11OH, n- C4H9OH and their mixes.

Extractability of complexes was assessed by coefficient of distribution (D) and extent of extraction (R%) [9]:

D =

[W ]

org

[W]

aq

R =

100x D

V~

D + Vq-

Chloroform, dichloroethane and chlorobenzene appeared to be the best extractants. Fast division of layers and the maximum value of molar coefficient of absorption were received at extraction of complexes by chloroform. After a single extraction with chloroform about 96.298.8% of tungsten was extracted as an ion associate. Further studies were carried out with chloroform. The concentration of tungsten in the organic phase was determined with dithiol by photometric measurements after back

extraction, while in the aqueous phase it was determined by the difference.

Influence of the pH of the Aqueous

Phase. Studying of dependence of a complex formation from pH showed that, the exit of complexes of tungsten is maximum at pH 4.55.5. Extraction of W (V) enhanced with the increase in the acidity of the initial solution but further increase in acidity lead to the gradual decrease of recovery, which was obviously associated with a decrease in the concentration of the ionized form of o-hydroxythiophenol

derivatives. Probably, it is present in the solution in the non-dissociated state. At pH>7.1 the complexes were hardly extracted, perhaps, owing to the decrease in the degree of AP protonation. The effect of pH on the intensity of the colour reaction is shown in Fig. 1 (Table 1). It could be seen that W(V)- HCTP-Am species are extracted in a great extent at pH values in the range 2.5-7.1 (with AP1), 2.3-6.9 (with AP2) or 2.1-6.8 ( with AP3) W-HBTP-Am complexes are extracted at low pH: 2.2-6.9

(with AP1), 2.0-6.8 (with AP2) or 1.7-6.7 (with AP2). W- HITP-Am complexes are extracted at lower pH: 2.0-6.6 (with AP1), 1.8-6.4 (c AP2) or 1.5-6.2 (with AP3). Existence of one maximum peak of absorbance in the specified limits of pH reaffirms the assumption of formation of one complex connection. The nature of acids (HCl, H2SO4) does not practically influence a complex formation of Molybdenum with o-hydroxythiophenol derivatives and AP.

Fig. 1 Absorbance of W(V)-HTPDs-AP complexes in chloroform pH of the aqueous phase. 1 -W(V)-HCTP-AP1; 2 - W(V)-HBTP-AP1; 3 - W(V)-HITP-AP1. Cw = 109 x 10-5 mol L-1, HTPDs = (2.2-2.8)x10-3mol L-1, Cap = (2.0-2.5)x10-3 mol L-1, X=490 nm, SF-26, £=1.0 cm

Electronic Absorption Spectra. The

absorption maxima (Xmax) of the ternary W(V)-HTPDs-AP complexes is identified within the range of 461-490 nm (Table 1). All color

reactions proved to be rather contrast since the initial solutions are colorless (Vax (HTPDs) = 283-290 nm). Thus, bathochromic shift makes 171-207 nm.

Table 1. Optical characteristics, precision and accuracy of the spectrophotometry determination of

W(V) with HTPDs and AP

Analytical characteristics HCTP HBTP HITP

AP1 AP2 AP3 AP1 AP2 AP3 AP1 AP2 AP3

PH1 2.5-7.1 2.3-6.9 2.1-6.8 2.2-6.9 2.0-6.8 1.7-6.7 2.0-6.6 1.8-6.4 1.5-6.2

pH2 4.5-5.5 4.1-5.3 4.0-5.1 4.3-5.2 4.1-5.0 3.9-4.8 4.0-5.0 3.7-4.8 3.5-4.6

R3/ % 96.2 98.8 96.7 97.4 98.1 98.5 97.2 98.0 96.5

Ânax / nm 490 485 483 480 476 472 470 465 460

M max / nm 207 202 200 194 190 186 180 175 171

Ma4 /L mol-1cm-1 2.8 2.7 2.6 2.4 2.3 2.3 2.2 2.1 2.0

Cp5/ y 1.01 0.95 1.03 1.05 1.06 1.07 1.09 0.99 1.02

Ec6/ lgKe 6.45 6.87 7.24 8.13 8.61 8.72 9.43 9.66 9.89

Sc7/ lgp 7.19 7.36 7.68 8.73 8.97 9.05 10.57 11.25

Wr8 / ^g cm-3 0.5-95 0.5-90 0.5-95 0.5-90 0.5-85 0.5-80 0.5-85 0.5-80 0.5-80

Note: 1- pH range complexation;2- The pH range of maximum extraction, 3- Degree of extraction; 4-Coefficient polymerization; 5- Molar absorptivity; 6- Equilibrium constant; 7- Stability constant; 8- Working range

Close values of maxima of light absorption make it possible to draw a conclusion that the formed complexes were ionic associates. Contrast of reactions was high i.e. initial reagents are colorless while complexes are intensively painted. Molar coefficients of absorption make up (2.0-2. 8)x104 L mol-1 cm .

Reagent Concentration and Incubation Time Influence. The effect of the concentration of HTPDs on the completeness of complexation was studied at the optimum pH and at a constant concentration of tungsten and AP. The optimum amount of AP for the maximum binding of the anionic hydroxyl thiophenolate complex of tungsten [W (V)-HTPDs] into an ionic associate was established by varying the quantity of AP added. For the formation of mixed-ligand complex (MLC) W(V)-HTPDs-AP, the concentration of (1.2 -2.5)x10"3 M of HTPDs and (2.0-2.8) x 10-3 M of AP in the solution is required.

MLC of W(V)-HTPDs-AP were stable

in aqueous and organic solvents and did not decompose for three days, and after extraction, for more than a month. The maximum absorbance is attained within 5-8 minutes.

Stoichiometry of the Complexes and the Mechanism of Complexation. The ratio of components in the complex corresponds to W (V) : HTPDs : AP = 1 : 2 : 2; it was determined by the methods of straight line, equilibrium shift, and the relative yield [12].

Also, additional experiments by the Akhmedly's method [13] showed that the complex exists in monomeric form in the organic phase (obtained coefficient of polymerization y was equal to 0.95-1.09).

The stability constant was determined by crossed lines method. The stability constant of W(V)-HTPDs-AP complexes was calculated and found to be lgP = 7.19-11.25 at room temperature. The sizes of equilibrium constant Kex calculated on a formula

lgKex = lg D - 2lg [AmH +]

were given in Table 1.

The IR spectra of the complexes W-HCTP- AP1, in the field of 780-810 cm1 is indicative of an intensive strip of absorption caused by valent vibration of group [O=W-Cl]2+ [14]. The disappearance of a distinct strip at 2580 sm-1 which is observed within the range HCTP shows that sulfhydryl groups participate in the complex formation. Observed reduction of intensity of a strip of absorption in area of 3200-3600 sm-1, with a maximum at 3455 sm-1, emergence of a wide strip in area 3050-3150

sm-1 shows that the hydroxyl group takes part in

the formation of coordination communication in the ionized state. Detection of strips of absorption at 2385 cm-1 indicates availability of the protonated AP1 [15].

In a highly acidic medium, there are various cationic forms of tungsten (V) in the solution with dominating WO3+ ion [10]. The number of protons replaced by tungsten in a HTPDs molecule appeared to be two. With due regard for the identified component ratio in the complex and an ionic state of tungsten, it was assumed that upon complexation, the following reactions proceed:

From Eqs (1) and (2), one can judge the reaction mechanism: tungsten (VI) is reduced by o-hydroxythiophenol derivative in a hydrochloric acid medium to tungsten (V), and the latter in the form of a chloride complex cation interacts with excess HTPDs. The resulting anionic complex

[WOClR2]2- is reacted with AP, which the acidic solution is in the protonated state (APH+).

Influence of Interfering ions. The

selectivity for the spectrophotometric determination of tungsten in the form of the complex described above is shown in Table 3. It

was established that large amounts of alkali, alkaline earths, and rare earth metals and fluorides, chlorides, and sulfates do not interfere with the determination of tungsten. The interfering effect of Fe (III) was eliminated by introducing a 20% solution of SnCl2 before the addition of the reagent; the effect of Ti (IV) was removed by adding ascorbic acid, and Cu (II), by thiourea. Mo (VI) is acidic medium reduced with HCTP to Mo (V) and is masked by the addition of EDTA. Owing to the fact that tungsten forms a complex in a more acidic medium than vanadium, it can be determined in the presence of large amounts (50 pg) of vanadium.

Table 2. Influence of interfering ions on the determination of tungsten (V) as MLC with HCTP

and AP1 (30,0 pg of W added, n=5, P=95%)

Ion Molar excess of the ion Masking agent Found W, ^g RSD,%

Cu(II) 79 Thiourea 30.0 5

Zr(IV) 76 NaF 30.1 3

Cd(II) 92 29.8 6

Fe(III) 85 29.7 3

Fe(II) 80 30.0 3

Al(III) 210 30.0 4

Ni(II) 85 EDTA 30.2 5

Co(II) 68 EDTA 29.6 4

Ti(IV) 20 Ascorbic acid 29.5 6

Mn(II) 70 29.8 5

U(VI) 60 CH3COO" 30.1 3

Mo(VI) 30 30.3 4

Cr(III) 50 29.7 4

V(IV) 90 30.4 6

Ta(V) 50 30.5 4

Nb(V) 50 30.6 5

Pt(II) 75 N2C4H4O6 30.4 4

Pd(II) 78 29.5 5

To conclude, the analytical parameters pertaining to the proposed method are given in Table 1.

Effect of tungsten (V) concentration.

The adherence to Beer's law was studied by measuring the absorbance value of the series of

solutions containing different concentrations of the metal ion. Beer's law is obeyed over the concentration range 0.04 - 3.8 pg W(V) mL-1 (Fig. 2). Table 3 summarizes the calibration characteristics obtained with HTPDs and AP.

Fig.2. Beer's law range of W (V)- HTPDs-AP complex in chloroform at 470-490 nm

7-W(V)-HCTP-AP1; 2-W(V)-HBTP-AP1; 3-W(V)-HITP-AP1.

Table 3. Analytical characteristics of some ternary complexes of W with HTPDs and AP

Compound SS* (pg cm-2) Beer's law range (pg- mL- LOD*, ng mL-1 LOQ*, ng mL-1 Equation of calibration curves Cc*

W-HCTP-AP1 0.0033 0.05-3.8 11 36 0.032+0.25x 0.9987

W-HCTP-AP2 0.0034 0.04-3.6 12 40 0.027+0.24x 0.9974

W-HCTP-AP3 0.0035 0.05-3.8 11 36 0.045+0.22x 0.9931

W-HBTP-AP1 0.0038 0.04-3.6 12 40 0.039+0.21x 0.9981

W-HBTP-AP2 0.0040 0.04-3.4 15 50 0.015+0.20x 0.9891

W-HBTP-AP3 0.0040 0.05-3.3 14 45 0.014+0.20x 0.9956

W-HITP-AP1 0.0044 0.04-3.4 10 33 0.031+0,18x 0.9989

W-HITP-AP2 0.0046 0.05-3.2 12 40 0.024+0.16x 0.9975

W-HITP-AP3 0.0050 0.05-3.2 9 29 0.023+0.15x 0.9991

*Note: SS- Sandell's sensitivity; LOD- Limit of detection; LOQ- Limit of quantificat ion; Cc-Correlation coefficient.

The proposed method is comparable favorably advantages of better simplicity, rapidity, with the existing ones (Tab. 4) and offers the sensitivity and selectivity [1-3,6].

Table 4. Comparative characteristics of tungsten determination methods

Reagent pH (solvent) nm sx10"4 Beer's law range (^g- ml-1) Sandell's Sensitivity (Mg cm-1)

Toluene-3,4-dithiol [1-3] 1.5-2.0 (CHCl3) 640 1.92 Not known 0.0060

8- Mercaptoquinoline [1,2,6] 0.5-3.0 wo-C4H9OH -CHCl3 (1:1) 412 0.367 <4 Not known

8 - Hydroxyquinoline [2,6] 4.4 (CHCl3) 363 0.64 Not known

Proposed method HCTP-AP1 4.5-5.5 (CHCl3) 490 2.8 0.05-3.8 0.0033

HBTP-AP1 4.3-5.2 (CHCl3) 480 2.4 0.04-3.6 0.0038

HITP-AP1 4.0-5.0 (CHCl3) 470 2.2 0.04-3.4 0.0044

Analytical Applications

Determination of tungsten in steels. 0.1 g

weighed sample of steel [composition steel EU-45 (0.24% of C, 0.60% of Mn, 0.03% of Si, 3.30% of Cr, 0.50% of Ni, 0.50% of W, 0.50% of Mo, 0.30% of V, and the rest of Fe)] was dissolved under heating in 4 mL of freshly prepared mixture of HCl and HNO3 (3: 1) in the presence of a few drops of HF. After the dissolution, 0.5 mL of HCOOH is added, and the mixture is heated until the decomposition of HNO3 occurs. After cooling the mixture is transferred to a 50 mL volumetric flask and diluted up to the mark with water. An aliquot portion of the resulting solution is transferred to a separatory funnel; 3.0 mL of 0.01 M HCl and 0.3-0.5 mL of a 0.01 M HTPDs solution were added, and, after thorough mixing, 2.0-3.0 mL of a 0.01 M AP solution was added. he volume of the organic phase was adjusted to 5 mL with

chloroform, and the volume of the aqueous phase was brought to 20 mL with distilled water. The mixture was shaken for 5-8 min. After layering of the phases, the absorbance of extracts is measured using a KFK-2 photocolorimeter at 490 nm in cuvettes of 0.5 cm thick. The tungsten concentration is found from the calibration curve. The results are shown in Table 5.

Determination of tungsten in soils. The proposed procedures for the determination of tungsten were applied to reveal it in the light-chestnut soil from the Caspian zone. A 0.5 g weight was finely ground in an agate mortar and calcined in muffle furnace for 3 h. After cooling, the sample was treated and dissolved in a graphite cup in a mixture of 16 mL of HF (conc.), 5 mL of HNO3 (conc.), and 15 mL of HCl (conc.) at 50-60oC to remove excess

hydrogen fluoride. A further 8 mL portion of HNO3 (conc.) was added triply to the solution that had each time been evaporated to 5-6 mL. After that, the solution was transferred into a 100 mL volumetric flask and its volume was brought to the mark with distilled water. Thus,

tungsten was identified in aliquot portions of the solution using the proposed procedures.

The accuracy of the results was checked by three independent methods. The results are shown in Table 5.

Table 5. Tungsten content in steel and soil samples determined by different methods («=5, P=95%)

Method Tungsten content in steel (EU-45: 0.50% W) Tungsten content in soil

XX, % RSD,% x104,% RSD,%

Toluene-3,4-dithiol [6] 0.48 3.4 4.65 3.6

8- Mercaptoquinoline [2] 0.52 3.2 4.53 3.9

8 - Hydroxyquinoline [2] 0.51 3.6 4.92 4.5

Proposed method HCTP-AP1 0.47 3.5 4.85 3.2

HBTP-AP1 0.51 3.5 4.49 5.1

HITP-AP1 0.48 3.4 4.71 4.6

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VOLFRAMIN (VI) O-HÍDROKSÍTÍOFENOL TORdMdLdRI УЭ HÍDROFOB AMiNLBRLB

KOMPLEKS omologolmosínín spektrofotometrík todqíqí

§.A. Mzmmzdova, Ü.B. Abasquliyeva, B.Z. Zalov, N.A. Novruzova

Azsrbaycan Dovlst Pedaqoji Universiteti, Üz. Hacibsyov küq. 68, AZ1000, Baki e-pogt: zalov1966@mail. ru

Xülasd: Volframin (VI) o-hidroksitiofenol torsmslsri (HTF) {2-hidroksi-5-xlorotiofenol (HXTF), 2-hidroksi-5-bromotiofenol (HBTF) vs 2-hidroksi- 5-iyodotiofenol (HITP )} vs aminofenollarin i^tiraki ils kompleks smslsgslms reaksiyasi spektrofotometrik tsdqiq edilmi^dir. Aminofenol kimi 2(N,N-dimetilaminometil)-4-xlorfenol (AF1) vs 2(N,N-dimetilaminometil)-4-bromfenol (AF2), 2(N,N-dimetilaminometil)-4-yodfenol (AF3) istifads edilmi^dir. Müxtslifliqandli komplekslsrin (MLK) smsls gslmssi vs ekstraksiyasi ügün optimal §srait, komplekslsrin tsrkibinds komponentlsrin molyar nisbsti müsyysn edilmi^dir. MLK zsif tur^u mühitds smsls gslir (pHopt 4.5-5.5). í^iqudma spektrinds maksimum X=460-490 nm dalga uzunlugunda mü^ahids edilir. Molyar i§iqudma smsali e = (2.0-2.8) x 104-s bsrabsrdir. MLK-lsrin smsls gslmssi vs ekstraksiyasi ügün (1.2-2.5) x 10-3 mol/l HTF vs (2.0-2.8)x10-3 mol/l qatiliqda AF tslsb olunur. Maksimum optik sixliga 5-8 dsqiqs srzinds gatilir. Volframin 0.04-3.8 ng/5 ml qatiliq intervali Ber qanununa tabe olur. Tsklif olunan üsulpoladda vs torpaqda volframi tsyinins tstbiq edilmi^dir.

Agar sozfor: volfram, o-hidroksitiofenol torsmssi vs hidrofob aminlsr, ekstraksiyali-fotometrik üsul, a^karlama hsddi, tsyini.

СПЕКТРОФОТОМЕТРИЧЕСКОЕ ИССЛЕДОВАНИЕ КОМПЛЕКСОБРАЗОВАНИЯ ВОЛЬ ФРАМА(У1) С ПРОИЗВОДНЫМИ о-ГИДРОКСИТИОФЕНОЛА В ПРИСУТСТВИИ

ГИДРОФОБНЫХ АМИНОВ

Ш.А. Мамедова, У.Б. Абаскулиева, А.З. Залов, Н.А. Новрузова

Азербайджанский Государственный Педагогический Университет, Ул. Уз. Гаджибекова, 68, AZ1000 Баку e-mail: zalov1966@mail. ru

Аннотация: Спектрофотометрическими методами изучена реакция комплексообразования вольфрама с производными о-гидрокситиофенола (ГТФ) {2-гидрокси-5-хлортиофенол (ГХТФ), 2-гидрокси-5-бромтиофенол (ГБТФ) и 2-гидрокси-5-иодтиофенол (ГИТФ)} в присутствии аминофенолов. Из аминофенолов использованы 2^^-диметиламинометил)-4-хлорфенол (АФ1) и 2(N,N-диметиламинометил)-4-бромфенол (АФ2), 2^^-диметиламинометил)-4-йодофенол (АФ3). Найдены оптимальные условия образования и экстракции разнолигандных комплексов (РЛК) и установлены соотношения компонентов в комплексах. Установлено, что РЛК образуются в слабокислой среде (рНопт 4.5-5.5). Максимум в спектре светопоглощения наблюдается при Х=460-490

нм. Молярный коэффициент светопоглощения равен £ =(2.0-2.8)* 104. Оптимальным условием образования и экстракции этих соединений является концентрация (1.2- 2.5)*10-3 моль/л ГТФ и (2.0-2.8)*10-3 моль/л АФ. Максимальная оптическая плотность достигается в течение 5-8 мин. Экстракты РЛК вольфрама с ГТФ и АФ подчиняются закону Бера при концентрациях 0.04-3.8 мкг/5мл. Предлагаемый метод был применен для определения вольфрама в стали и почвах. Ключевые слова: вольфрам, производное о-гидрокситиофенола и гидрофобные амины, экстракционно-фотометрический метод, предел обнаружения, определение.