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AZERBAIJAN CHEMICAL JOURNAL № 3 2023 ISSN 2522-1841 (Online)
ISSN 0005-2531 (Print)
UDC 54342.062:546.56
EXTRACTION-PHOTOMETRIC DETERMINATION OF IRON(III) IN OIL AND OIL PRODUCTS OF BAKU USING 2-HYDROXY-5-HALOGENTHIOPHENOL AND HYDROPHOBIC AMINES
A.Z.Zalov\ C.K.Rasulov2, Sh.A.Mammadova1, S.G.Aliyev3
Azerbaijan State Pedagogical University Y.H.Mammadaliyev Institute of Petrochemical Processes of the Ministry of Science and Education
of the Republic of Azerbaijan Azerbaijan State University of Oil and Industrial
Zalov1966@mail.ru
Received 31.01.2023
Accepted 08.02.2023
The purpose of this work is to develop a highly selective method for the photometric determination of iron (III) in environmental objects, in particular, in oil and oil products using hydroxyhalogenthiophenol (H2R) - 2-hydroxy-5-chlorothiophenol, 2-hydroxy -5-bromothiophenol and 2-hydroxy-5-iodothiophenol and hydrophobic amines - 1,10-phenanthroline, a,a'-dipyridyl, diphenylguanidine o-, m-, p-toluidine, o-. m-, p-xylidine. It has been established that the reagent is a dibasic acid and, depending on the acidity of the medium, can be in molecular (H2R) and anionic (HR- and R2-) forms. For 2-hydroxy-5-chlorothiophenol: pKi=5.1; pK2=10.6; 2-hydroxy-5-bromothiophenol: pKi=5.05; pK2=10.4; 2-hydroxy-5-iodothiophenol: pKj=5.0; pK2=10.2. The dependence of the ionization constants (pKa) H2R on the ionic strength of the solution pKn= f(^) in the range ^ = 0 - 1 is linear and is described by the equations: 2-hydroxy-5-chlorothiophenol: pKj=5.2762 - 0.5506^, pK2=10.7289 - 0.4028^; 2-hydroxy-5-bromothiophenol: pK = 5.2643 - 0.6697^, pK2=10.5341 - 0.4191^; 2-hydroxy-5-iodothiophenol: pKj=5.1483 - 0.4634^; pK2=10.3621-0.5066^. The effect of the concentration of reacting components, time, and temperature on the formation of mixed-ligand complexes was studied, and their stoichi-ometry was determined by various methods. It has been established that an extractable compound is formed with a ratio of components of 1:2:2. The complex includes Fe3+ and Fe(OH)2+ ions. The charge of iron (III) complexes with H2R was determined by electromigration and ion-exchange chromatography. The molar absorption coefficient of the complexes is (3.0-4.5)*104 (X = 545-595 nm). The calibration curve is linear in the iron (III) concentration range of 0.40-22.5 mg/ml. The detection limit for Fe(III) at P = 0.95 is 0.011-0.017 mg/ml. The developed technique was applied to determine the trace amounts of iron in oil and oil products.
Keywords: iron(III), halothiophenol hydroxide, extraction, oil, oil products.
doi.org/10.32737/0005-2531-2023-3-126-133 Introduction
One of the most important tasks of analytical chemistry is the determination of metals in environmental objects, especially in natural waters, fruits, oil and oil products. The reliability of the analysis depends on the completeness of the extraction of the determined elements. The modern world is closely connected with the use of fuel and energy resources, energy and many other industries use petroleum products as fuel, which may include gasoline, diesel fuel, fuel oil and other petroleum products. Oil trace elements are metals and non-metals contained in oil (V, Ni, Fe, Zn, Al, Hg, Cd, Cu, Mn, Se,
As, Pb, Sb, Ba, Mo, Cr, Ag, Au, Na, Ca, Br, Si, Sr, Co, Ti, Ga, Sn). Some metals in oils are in the form of salts of organic acids and chelate complexes [1].
Iron belongs to the transition elements and forms very strong coordination bonds with any donor atoms of the ligands. Reagents containing OH groups and donor nitrogen atoms are considered the most suitable for the determination of iron(III) [1-2]. Methods for the photometric determination of iron(III) in the form of mixed ligand complexes (MLC) with this reagent in the presence of third components of various classes are highly sensitive [3-8].
Selective for iron (III) are reagents containing OH-groups. Reactions of Fe(III) with diphenols are more sensitive than reagents containing one OH-group [6]. When one OH group is replaced by an SH group, the selectivity decreases, since elements with an affinity for sulfur interact with SH-containing reagents, and vice versa, the sensitivity increases [1]. Thio-and dithiophenols as analytical reagents are constantly in the focus of attention of researchers [9-14]. This is due to the large range of these compounds, as well as the possibility of obtaining new substances based on well-studied thiophenols.
The purpose of this work is to develop a highly selective method for the photometric determination of iron(III) in environmental objects, in particular, in oil and oil products using hydroxyhalogenthiophenol (H2R, R) - 2-hydr-oxy-5-chlorothiophenol (HCTP), 2-hydroxy-5-bromothiophenol (HBTP) and 2-hydroxy-5-iodothiophenol (HITP) and hydrophobic amines (Am) - 1,10-phenanthroline (Phen), a,a'-dipy-ridyl (Dip), diphenylguanidine (DPG ) o-, m-, p-toluidine (o-Tol), (m-Tol), (p-Tol), o-. m-, p-xylidine (o-Xyl), (m-Xyl), (p-Xyl).
Experimental part
Reagents
An iron(III) solution (0.1 mg/ml) was prepared by dissolving from "x.p. " FeCl3 x6H2O PK2 - pH + lg
ammonium-acetate buffer (pH = 3-11), a constant ionic strength |i=0.1 was maintained using KCl. All reagents used were of at least analytical grade.
Apparatus
Equipment. Spectrophotometric studies of colored solutions were carried out on UV-1240 (Shimadzu) with the thickness of the absorbing layer £=0.5 and 1.0 cm, respectively. The pH of the aqueous phase was measured on an I-120.2 device with a glass electrode.
Dissociation constants H2R
H2R - contains - OH and - SH groups and can dissociate into two steps K1 and K2 (pK1 and pK2) during complex formation. To determine the first and second dissociation constants of hydroxyhalogenthiophenol by pH-metric titration [16], a 0.1 M H2R solution was taken at 20 ± 50C, 1 ml of 1 N HClO4 was added, and the ionic strength p = 0.1 was created using a 2 M KCl solution (1 - 2 ml). The final volume of the titrated mixture is 50 ml. Titration was performed with 1 M NaOH solution. Calculation of K1 and K2 (pK1 and pK2) of H2R dissociation was carried out according to the results of titration [16].
PK - pH + lg[
[R " ]
[HR] + [OH - ]
and
as described in [15]. Solutions with a lower concentration were prepared from stock immediately before use.
We used 0.01 M solutions of H2R and Am in chloroform. The purity of the reagents was controlled chromatographically and by melting point. A constant concentration of hydrogen ions in solutions was maintained using an
[R ] - [OH ] For HCTP: pK =5.1; pK2 = 10.6; HBTP: pK1 =5.05; pK2 = 10.4; HITP: pK1 =5.0; pK2 = 10.2.
It has been established that the reagent is a dibasic acid and, depending on the acidity of the medium, can be in molecular (H2R) and anionic
(HR- and R2-) forms:
X= -CI, -Br, - J
The diagram of the distribution of various forms of the reagent depending on the pH of the medium is shown in Figure 1.
Fig. 1. Distribution diagram of different forms of R depending on the pH of the medium. mole fraction for H2R, HR- and R2-, %. 1- HCTP; 2- HBTP; 3- HITP.
It can be seen that, at pH <2, the reagent is mainly in the H2R molecular form. The dependence of the ionization constants (pKa) H2R on the ionic strength of the solution pKn =f(p) (Figure 2) in the range p = 0-1 is linear and is described by the equations:
HCTP: pK = 5.2762 - 0.5506Vp; pK2 = 10.7289 - 0.4028Vp.
HBTP: pK = 5.2643 - 0.6697Vp; pK2 = 10.5341 - 0.4191Vp.
HITP: pK = 5.1483 - 0.4634Vp; pK2 = 10.3621- 0.5066Vp.
pK2 10.60
in 5
10.48
10.4
10.36
10.15 9.80
pKi 5.25
5 00
4 7
4.5 4 25 4.00
0.2 0.4 0.6 0.8 1.0 Vu
Fig. 2. Dependence of the ionization constants pK (1,2,3) and pK2 (11,21,31) H2R on the ionic strength of the solution CH2R =0.1M. 1,11 - HCTP; 2,21 - HBTP; 3.31 - HITP.
Methods
In volumetric flasks 25 ml was injected from 0.1-1.0 ml (10-100 mg) with an interval of 0.2 ml of the initial Fe(III) solution (0.1 mg/ml), 2.0-2.5 ml of a 0.01 M H2R solution, and 1.0-1.4 ml of Am (in the case of Dip, Phen DPG - 1.2-1.5 ml 0.01 M Am), 1.8-1.0 ml CHCl3 and 2-4 ml buffer solution, diluted with water to the mark. 10 minutes after complete phase separation, the organic layer was separated and its optical density was measured at room temperature on UV-1240 (Shimadzu) at X=540 (590) nm (£=0.5 cm).
The charge of iron(III) complexes with
H2R was determined by electromigration and ion-exchange chromatography.
When studying the electromigration of these complexes, the determination conditions are: CFe = 2.14x10-5 mol/l, Ch2r = (1.12-1.16)x10-3 M, CAm = 0.25-0.35 M (in the case of Dip, Phen, DPG - (2.4-3.0) xio-3 M Am), pH 4-6; voltage 150-170 V, current 10 mA, electrophoresis duration 12 h. The charge of Fe(III)-R complexes was judged by the direction of movement of the colored spot on a strip of filter paper dipped into a buffer solution.
When studying the sign of the charge of homogeneous ligand complexes by ion-exchange chromatography, the test solution containing 2.1410-5 mol/l iron, (1.12-1.16)-10-3 M H2R, 0.25-0.35 M Am (in the case of Dip, Phen, DPG - (2.4-3.0)x10-3 M Am), in an ammonium-acetate buffer medium with a pH of 46, was shaken for 6 hours with 1 g of weighed portions of anion exchanger and cation exchanger. As a result, the colored compound was completely sorbed on EDE-10P, which indicates the anionic nature of the complexes. These data are confirmed by extraction of these complexes with Am chloroform solution.
Equilibrium (Keq) and extraction (Kex) constants
Based on the determination of the molar ratios of the reacting components, it can be assumed that the reactions of iron (III) with H2R and Am proceed as follows: Fe3+ +2H2R^[Fe(HR)2]2-+2H+ (1)
[FeOH(HR)2]2-+ 2HAm+ (HAm+)2[FeOH(HR)2]
(2)
The equilibrium constant of reaction (2) is equal to:
K _ {(HAm)2[FeOH(HR)2]}org
[FeOH(HR)2]2aq[{HAm+)2]aq ( )
Since the distribution ratio (D)
D =
{(,HAm)2[FeOH(HR)2]}org
(4)
[FeOH(HR)2]2a-The reform
Kecl = [(HAm+)]2 (5)
Taking the logarithm of the last expression, we get
lgKeq = lgD - 2lg[HAm+] (6)
Extraction constants were calculated using the equation
lgKex = lg D - 2lg [HR2 ] - 2lg[HAm+] (7)
The values of lgKeq and lgKex calculated by formulas (6) and (7) are 2.09-9.13 and 5.2814.32, respectively.
Results and Discussion
The choice of extractant
Hydrocarbons, their chlorine derivatives, esters, and also their binary mixtures were tested as extractants. Chloroform is the most effective in terms of the maximum degree of extraction (97.5-98.7%) of Fe(III) in the form of MLC and the rapid achievement of equilibrium. The equilibrium concentration of iron in the aqueous phase was determined by the thiocya-nate method [1], and in the aqueous phase, by difference.
Influence of the pH of the aqueous
phase
When iron(III) reacts with H2R and Am, a colored complex is formed at pH 1.6-8.5. The study of the dependence of the optical density on the pH of the solution showed that the formation of MLC of iron (III) with H2R and Am is maximum at pH 3.5-6.0. Fe(III) complexes with H2R and Am are completely destroyed at pH<1.5. Obviously, it is associated with a decrease in the concentration of the ionized form
of H2R. At pH 8.5, the complexes are practically not extracted, which is apparently associated with a decrease in the degree of Am protoniza-tion and a change in the ionic state of iron (III).
Electronic spectra of complexes
Chloroform extracts of MLC Fe(III)-R-Am have a light absorption maximum in the range of 545-595 nm. Knowing the optical density of chloroform extracts and the concentration of iron (III) bound into the complex, the molar absorption coefficients were calculated.
Influence of ligand phase volume and time
concentration,
In the Fe(III)-R-Am system, complex formation depends both on the sequence of merging of the reacting components and on the concentration. The completeness of complex formation and extraction is observed with an excess of reagents.
Light absorption does not decrease when the ratio of the volumes of organic solvent and aqueous solution is 1:20.
MLC of iron (III) with H2R and Am is formed immediately after mixing the solutions of the components. At pHopt it is stable during the day.
Determination of molar ratios of reacting components and stability constants
The ratios of the components in the composition of the resulting colored complexes were established relative to the yield and shift of the equilibrium [17]. The ratio of components in MLC Fe(III):R:Am=1:2:2. It turned out that under the conditions under study, the coordinating iron (III) ion in the formation of a
3+
complex with R-Phen (Dip) is Fe , and in the formation of complexes with R-Am (the rest of Am) it is Fe(OH)2+. Phen and Dip (L) in an acidic medium are singly and doubly protonated at heteroatoms [18] and form an MLC with a mixed sphere: [FeR2L](LH2). The composition of the complexes formed with other amines corresponds to: [FeR2(OH)](AmH)2.
To confirm the ratio of components in the MLC of iron (III) with HCTP and L, a complex compound in the solid state was isolated and
analyzed for nitrogen, chlorine, iron and sulfur. In this case, the following results were obtained:
(PhenH2)[Fe(HR)2(Phen)]
Calculated, %: Fe - 7.88; Cl - 9.98; S -9.00; N - 7.88.
Found, %: Fe-7.95; Cl-10.07; S- 9.13; N-7. 76.
(DipH2)[Fe(HR)2(Dip)]
Calculated, %: Fe-9.47; Cl-12.01; S, 10.83; N-9.47.
Found, %: Fe-9.45; Cl-12.40; S-10.02; N-9.55.
Thus, the results of the study lead to the conclusion that the ratio Fe(III):R:Am=1:2:2 in extractable MLC. The stoichiometry and conditional stability constant (lgP) of homoge-neous ligand Fe(III)-R complexes were deter-mined using the curve crossing method [17]. The results obtained by these methods were confirmed by determining the stoichiometry and it was found that lgP=3.06-10.14. Taking into account the molar ratio of the components in the MLC, their conditional stability constants were determined. It has been found that in the presence of Am, the stability of the complexes increases by about two orders of magnitude: log P=5.28-12.86. The calibration curve is linear in the iron(III) con-centration range of 0.40-22.5 Hg/ml. The limit of photometric detection of Fe(III) in the form of MLC was calculated us-
ing the equation [17]. The detection limit for Fe(III) at P = 0.95 is 0.011-0.017 mg/ml.
Influence of foreign ions
The procedure for the determination of iron(III) with R in the presence of a,a'-dipyridyl and 1.10-phenanthroline has the highest selectivity. So, for example, the determination of iron(III) in the form of MLC Fe(III)-R-Phen does not interfere with more than 3500-fold amounts of alkali, alkaline earth metals, REE and Cl-, NO3-, SO42-; 1000-fold - In(II), Cd(II), Mg(II); 800-fold - Co(II), Ni(II), Mn(II) and U(VI); 400-fold - Cu(II), Pb(II), Cr(III) and Th(IV); 1000-fold - Al(III), Ga(III), In(III), Bi(III), Sb(III), Zr(IV), Hf(IV); 240-fold -Ti(Iv), Nb(V), Ta(V); 200-fold V(V), Mo(VI) and W(VI).
The interfering effect of Cu(II), Cr(VI), and Mn(VII) was eliminated with thiourea; Ti(IV) - ascorbic acid, Zr(IV), Nb(V) and Ta(V) - fluoride ions. If the analyzed solution contains V(V), Mo(VI) and W(VI), then two extractions must be carried out. Extraction at pH <1.5 separates these ions and subsequent extraction at pH 3.5-6.0 transfers the iron(III) compound with H2R into the organic phase. The establishment of pH 3.5-6.0 before the second extraction is carried out by adding a solution of ammonium-acetate buffer.
Table 1. Data to compare the analytical characteristics of methods for the determination of iron(III) with already known reagents
Reagent pH (solvent) X, hm AX, hm ex 10-4 References
Gallic acid - An 6.8 - 7.8 650 380 0.56 [19]
4.9-5.3 365 - 0.794 [2]
Ferron 4.9-5.3 2.9-3.2 600 520 0.571
Pyrocatechin - An 5.1-5.6 (CHCI3 + C6H6) 540 262 0.2 [19]
Thiosalicylic acid - Phen 5-6 (CHCI3) 570 288 1.2 [19]
Salicylic acid ~ 1.2 (H2O) 528 - 0.378 [2]
2,3-dimethylpyrazolone - Phen 2.8-3.2 (H2O) 470 97 1.05 [7]
3.6-4.1 (H2O) 451 78 0.72
HCTP - Phen 3.0-6.0 (CHCl3) 594 311 4.0 Proposed
HCTP - Dip 3.5-6.0 (CHCl3) 595 312 4.2 method
HBTP - Phen 2.8-5.7 (CHCl3) 593 308 3.9
HBTP - Dip 3.3-5.7 (CHCl3) 594 304 4.0
Comparative characteristics of methods for the determination of iron (III)
In Table 1 shows the data that make it possible to compare the analytical characteristics of the procedures for the determination of iron(III) with the already known [2, 7, 19] methods. It can be seen that H2R has advantages over other reagents: the light absorption maximum is strongly shifted to the long wavelength region of the spectrum [2, 7], the molar light absorption coefficient is much higher than the molar light absorption coefficients of other complexes [2, 7, 19].
Analytical application
The proposed method, under already established optimal conditions, was applied to determine Fe(III) in oil and oil products.
Determination of iron(III) in oil and oil products Baku (Table 2)
For analysis, 40 g of the test fuel was placed in a porcelain cup and burned in accordance with GOST 1461 - 75. Then the porcelain cup with ash was placed in a muffle at a tem-
Conclusions
1. Spectroscopic methods were used to study the complexation of Fe(III) using hydroxyhalogenthiophenol (H2R, R) - 2-hydroxy-5-chlorothiophenol (HCTP), 2-hydroxy-5-bromothiophenol (HBTP) and 2-hydroxy-5-iodothiophenol (HITP ) and hydrophobic amines (Am) - 1,10-phenanthroline (Phen), a,a'-dipyridyl (Dip), diphenylguanidine (DPG) o-, m-, p-toluidine (o-Tol), (m-Tol), (p-Tol), o-. m-, p-xylidine (o-Xyl), (m-Xyl), (p-Xyl).
2. It has been established that hydroxyhalogenthiophenols is a dibasic acid and, depending on the acidity of the
perature of 550 ± 200C and kept at a temperature of 1 hour. After cooling, 5 ml of HCl (1:1) was added to the dish, the mixture was boiled to dryness, and 0.5 g of anhydrous Na2CO3 was added to it. Then the cup was placed for 2-3 min in a muffle heated to 8000C. After cooling, the alloy in the cup was dissolved in distilled water, filtered into a flask with a cap. 50 ml and diluted with water to the mark.
An aliquot of the solution (10.0 ml) was transferred into a 25 ml volumetric flask, 2.02.5 ml of a 0.01 M H2R solution, 1.2-1.5 ml of a 0.01 M Dip (Fen), and 1.8-1.0 ml of CHCl3 were added. The required pH value was set using ammonium-acetate buffer and the volume was adjusted to the mark with distilled water. After 5-10 minutes after complete separation of the phases, the organic layer was separated and its optical density was measured at room temperature on UV-1240 (Shimadzu) at X=590 nm (£=0.5 cm). The content of Fe(III) was found according to the calibration curve.
medium, can be in molecular (H2R) and
9
anionic (HR- and R2-) forms. For HCTP: pK1=5.1; pK2=10.6; HBTP: pK1=5.05; pK2=10.4; HITP: pK1=5.0; pK2=10.2.
3. The best extractants were CHCl3, C2H4Cl2 and C6H5Cl. All further studies were carried out with CHCl3. Under optimal conditions, this solvent provides the degree of extraction R = 97.5-98.7%. The degree of extraction of Fe(III) in the form of complexes does not depend on the ratio of the volumes of the aqueous and organic phases in a wide range (from 5:5 to 100:5). The completeness of complex formation and extraction is observed with
Table 2. Results of determination of iron in oil and oil products Baku (n = 5, P = 0.95).
Object of analysis Entered mg/l Found, mg/kg Relative standard deviation
With additive x ± <4 -Jn
Oil 10 16.18 (5.18±0.12)10-5 0.08
Fuel oil 10 12.69 (6.45±0.13)10-3 0.04
Hydron 10 14.31 (8.31±0.15)10-3 0.06
an excess of reagents. Extracts of Fe(III) complexes obey the basic law of light absorption at concentrations of 0.40-22.5 mg/ml.
4. The study of the dependence of complex formation on pH shows that the interaction of Fe(III) with R and Am and their extraction (yield of complexes) into the organic phase are maximum at pH 3.5-6.0. The maximum analytical signal during complex formation is observed at 545-595 nm. Molar absorption coefficients of the complexes s = (3.0-4.5)x104.
5. The ratio of components in the complex: Fe(III): R:Am=1:2:2. In the formation of complexes, the Fe(OH) ion is the coordinating one. Complex formation occurs with the displacement of two protons from one R molecule.
6. Determination of Fe(III) using R and Am does not interfere with ions of alkaline, alkaline earth elements and REE. The interfering effect of ions was eliminated by changing the pH of the medium using masking agents and extraction.
7. The proposed method, under already established optimal conditions, was applied to determine Fe(III) in oil and oil products.
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2-HÍDROKSÍ-5-HALOGENTÍOFENOL УЭ HÍDROFOB AMÍNLORDON ÍSTÍFADO EDÍLMOKLO BAKININ NEFT VO NEFT MOHSULLARINDA DOMÍRÍN (III) EKSTRAKSÍYON-FOTOMETRÍK TOYÍNÍ
A.Z.Zalov, CQRasulov, §.A.Mamm3dova, S.Q.Oliyev
Hazirki i§in maqsadi hidroksialogentiofenol (H2R, R) - 2-hidroksi-5-xlortiofenol, 2 -hidroksi-5-bromtiofenol va 2-hidroksi-5-yodtiofenol va hidrofob aminlar - 1,10-fenantrolin, a,a'-dipiridil, difenilquanidin o-, m-, p-toluidin, o-. m-, p-ksilidin istifada etmakla atraf mühit obyektlarinda, xüsusan da neft va neft mahsullarinda damirin (III) fotometrik tayini ügün yüksak segici metodun i§lanib hazirlanmasi olmu§dur. Müayyan edilmi§dir ki, reagent iki asasli tur§u olub, mühitin tur§ulugundan asili olaraq molekulyar (H2R) va anion (HR- va R2-) formada ola bilar. 2-hidroksi-5-xlorotiofenol ügün: pKi =5.1; pK2 = 10.6; 2-hidroksi-5-bromtiofenol: pKi = 5.05; pK2 = 10.4; 2-hidroksi-5-yodtiofenol: pKi = 5.0; pK2 = 10.2. H2R ionla§ma sabitinin (pKa) mahlulun ion qüvvasindan pKn = Дд) asililigi д = 0 - 1 intervalinda xattidir va novbati tanliklara uygun galir: 2-hidroksi-5-xlortiofenol: pK = 5.2762 - 0.5506^д, pK2 = 10.7289 - 0.4028^д; 2-hidroksi-5-bromtiofenol: pK = 5.2643 - 0,6697^д, pK2 = 10.5341 - 0.419Ыд; 2-hidroksi-5-yodtiofenol: pK = 5.1483 - 0.4634^д; pK2 = 10.3621-0.5066^д. Müxtalifliqandli komplekslarin amala galmasina komponentlarin qatiliginin, vaxt va temperaturun tasiri 6yranilmi§, onlarin stoxiometriyasi müxtalif üsullarla müayyan edilmi§dir. Müayyan edilmi§dir ki, ekstraksiya olunan birla§mada komponentlarin molyar nisbati 1:2:2 kimi olur. Komplekslarin tarkibina Fe3+ va Fe(OH)2+ ionlari daxildir. Damir (III) komplekslarinin H2R ila yükü elektromiqrasiya va ion mübadilasi xromatoqrafiyasi ila müayyan edilmi§dir. Komplekslarin molyar udma amsali (3.0-4.5)*104 (X = 545-595 nm) ta§kil edir. Daracali ayri damirin (III) 0.40-22.5 mkq/ml qatiliq intervalinda xattidir. Fe(III) minimum tayin olunma haddi R = 0.95olduqda 0.011-0.017 mkq/ml-dir. Hazirlanmi§ metodika neft va neft mahsullarinda damirin az miqdarini tayin etmak ügün tatbiq edilmi§dir.
Agar sozlar: damir(III), hidroksihalogentiofenol, ekstraksiya, neft, neft mahsulu.
ЭКСТРАКЦИОННО-ФОТОМЕТРИЧЕСКОЕ ОПРЕДЕЛЕНИЕ ЖЕЛЕЗА(Ш) В НЕФТИ И НЕФТЕПРОДУКТАХ БАКУ С ИСПОЛЬЗОВАНИЕМ 2-ГИДРОКСИ-5-ГАЛОГЕНТИОФЕНОЛА И
ГИДРОФОБНЫХ АМИНОВ
А.З.Залов, Ч.К.Расулов, Ш.А.Мамедова, С.Г.Алиев
Цель настоящей работы - разработка высокоизбирательной методики фотометрического определения железа(Ш) в объектах окружающей среды, в частности в нефти и нефтепродуктах с применением гидроксигалогентиофенола (H2R, R) - 2-гидрокси-5-хлортиофенол, 2-гидрокси-5-бромтиофенол и 2-гидрокси-5-иодтиофенол и гидрофобных аминов - 1,10-фенантролин, a,a-дипиридил, дифенилгуанидин о-, м-, п-толуидин, о-. м-, п-ксилидин. Установлено, что реагент представляет собой двухосновную кислоту и в зависимости от кислотности среды может находиться в молекулярной (H2R) и анионных (HR- и R2-) формах. Для 2-гидрокси-5-хлортиофенол: pKi =5.1; pK2 = 10.6; 2-гидрокси-5-бромтиофенол: pKi =5.05; pK2 = 10.4; 2-гидрокси-5-иодтиофенол: pK1 =5.0; pK2 = 10.2. Зависимость констант ионизации (pKa) H2R от ионной силы раствора pKn =f(^) в интервале д = 0 - 1 линейна и описывается уравнениями: 2-гидрокси-5-хлортиофенол: pK1 = 5.2762 - 0.5506^д, pK2 = 10.7289 - 0.4028^д; 2-гидрокси-5-бромтиофенол: pK1 = 5.2643 - 0.6697^д, pK2 = 10.5341 - 0.419Ыд; 2-гидрокси-5-иодтиофенол: pK1 = 5.1483 - 0.4634^д; pK2 = 10.3621- 0.5066^д. Изучено влияние концентрации реагирующих компонентов, времени и температуры на образование разнолигандных комплексов и определены их стехиометрия различными методами. Установлено, что образуется экстрагируемое соединение с соотношением компонентов 1:2:2. В комплекс входит ионы Fе3+ и Fе(ОН)2+. Заряд комплексов железа (III) с H2R устанавливали методом электромиграции и методом ионообменной хроматографии. Молярный коэффициент поглощение комплексов равен (3.0-4.5)х104 (X = 545-595 нм). Градуировочный график линеен в диапазоне концентрации железа(Ш) 0.40-22.5 мкг/мл. Предел обнаружения Fe(III) при Р = 0.95 составляет 0.011 - 0.017 мкг/мл. Разработанная методика применена для определения микроколичеств железа в нефти и нефтепродуктах.
Ключевые слова: железо(Ш), гидроксигалогентиофенол, экстракция, нефт, нефтепродукт.
19. Pilipenko A.T., Tananaiko M.M. Mixed-ligand and mixed-metal complexes and their application in analytical chem. M.: Chemistry, 1983. 221 p.
