Incorporation Onium System With Cloud Point Extraction Method for Extraction and Determination Iron(III) and Mercury(II) in Different Samples

Introduction

Iron is known as one of the essential nutritional elements for many living organisms due to its role in most of metabolic processes, including oxygen and electron transport, and DNA synthesis. exposure to excess iron can cause several diseases or disorders such as endocrine problems, arthritis, diabetes and liver disease^1,2. Mercury is a toxic element found throughout the environment. Its mobile nature allows it to diffuse through the air, soils and ultimately into water systems³Trace determination of heavy metals is one of the most important issues of chemical analysis⁴ In 1978 Watanab introduced cloud point extraction (CPE) as a new extraction method for determination of Zn with l-(2-Pyridylazo)-2-Naphthol ligand⁵ .Since then CPE was applied widely for determination of various analytes^6-7, mainly for the extraction of metal ions ^8-11. The most important feature of CPE is application of a surfactant, mostly non-ionic as the extractant phase¹² which means that CPE avoids the consumption of large amounts of expensive, toxic and flammable organic solvents¹³.Use crown ether DB18C6 and from acidic HCl media extracted Fe³⁺ ion by application CPL after change Fe³⁺ into FeCl₄^– TritonX-100 was necessary to obtained higher extraction efficiency Thermodynamic data was ΔH_ex=0.159 kJ mol^-1, ΔG_ex=-62.43 kJ mol^-1, ΔS_ex=174.83 J mol^-1K^-1, there are another empirical application for this study in real samples¹⁴.Used CPE methodology for determination Hg²⁺ in different tissues of grilled chickens with application clod vapors atomic absorption and organic agent (DDTP) so Triton X-114¹⁵.By application of CPE method coupled with spectrophotometric technique for extraction and determination of  Hg²⁺ in different samples of fish,new thiazolylazo reagent was synthesized 7-(6-Bromo2-benzothiazolylazo)-8-Hydroxyquinoline and Triton X-114 at specific pH=5, DOL=7.4 ng mL^{-1 16} .Sensitive application method of solvent extraction used onium system for extraction Zn²⁺ from acidic aqueous solution of HCl as oxonium species by used Methyl Stearate ester as sensitive extract ant dissolved in chloroform the study show extracted species giving maximum absorbance at wave length λ_max =275nm,Sandell’s sensitivity = 0.00832μg.cm^-218.

Experimental

Materialsand Solutions

For spectroscopic studies and absorbance measurements used double beam spectrophotometer (Biochrom Libra 560) (UK)so that used Electrostatic water bath (WNB7-45) (England) for heating to CPT, as well as all experiments needed balance (A & D company, Limited, Dool, CE, HR 200, Japan)(±0.0001g).

For preparing all the solutions needing in experiment used high purity materials received from commercial sources without further purification and used Doubly distilled water  with set of suitable glassware, stock  solution 1mg/mL of Fe³⁺ ion prepared by dissolving 0.2880 gm in of FeCl₃ in 100 mL and  for Hg²⁺ ion dissolved 0.1353 gm of HgCl₂ in 100 mL of distilled water  other working solutions preparing by dilution method with distilled water in suitable volumetric flask ,so 1×10^-2 M of Nα-Benzoyl-L-arginine ethyl ester hydrochloride (BAEE) was prepared by dissolving (0.08571gm) in (25mL) distilled water. Other working solutions were prepared by dilution method with distilled water.

Comprehensive Method

10 mL aqueous solution contain 100 µg of metal ion under study Fe³⁺ andHg²⁺ with optimum concentration HCl and 1×10^-4 M (BAEE), in the presence 0.5 mL of non-ionic surfactant Triton X-100.Heating the solution in electrostatic water bath for suitable temperature and time until formation cloud point layer then separated CPL from aqueous solution and dissolved CPL in 5 mL ethanol. The absorbance of alcoholic solution is measured at λ_max=362nm for Fe³⁺ and λ_max= 293nm for Hg²⁺ ion against blank prepared in the same manner without metal ions. but Aqueous solution for Fe³⁺ ion treated according to thiocyanate method but Hg²⁺ ion treated according to Dithizone spectrophotometric method ¹⁸ to determine remainder quantity of metal ions in aqueous solution after extraction and subtraction this quantity from original quantity 100µg to determine the transferred  quantity to CPL to formation onium species extracted then calculated distribution ratio (D).

Whereas   M⁺ⁿ₌ Fe³⁺ &   Hg²⁺

Results and Discussion

Spectrophotometry

10 mL aqueous solution contain 100µg of Fe³⁺orHg²⁺ with 1M HCl and 1×10^-4 M (BAEE),0.5mL 1% Triton X-100. Heating the solution in electrostatic water bath for suitable temperature and time until formation cloud point layer CPL with smaller volume, then separated CPL from aqueous solution and dissolved CPL in 5mL ethanol and talking absorption spectrum in(UV-Vis) region against blank prepared in the same manner without metal ions. The results were as in Figures (1 and 2):

Figure 1: UV-VIS.absorption spectrum for onium species of Fe3+.   Click here to View figure

 

Figure 2: UV-VIS. absorption spectrum for onium species of Hg2+. Click here to View figure

 

The spectrum show wave length for the maximum the absorbance of onium species of Fe³⁺ ion was λ_max= 362 nm but onium species of Hg²⁺ ion was  λ_max= 293 nm.

Variation of Hydrochloric Acid Concentration

Two set 10mL aqueous solutions contain 100µg of Fe³⁺orHg²⁺with different concentration HCl and 1×10^-4 M (BAEE), 0.5mL 1% Triton X-100. Heating the solution to suitable temperature and time until formation CPL, then separated CPL from aqueous solution and complete the procedure according to comprehensive method. The results were as in Figures (4 and 5).

Figure 3: calibration curve for determination metal ions in aqueous solutions.   Click here to View figure

 

Figure 4: effect of HCl concentration on formation and stability of onium species Click here to View figure

Figure 5: effect of HCl concentration on extraction efficient and D value Click here to View figure

 

The results shows 1M HCl was the optimum molar concentration of HCl in aqueous solution for extraction onium species of Fe³⁺ and Hg²⁺ ions at this molar concentration reached to higher extraction efficiency appear higher absorbance and D values because at this molar concentration reached to favorable equilibrium of formation onium species so that partitioning into cloud point layer CPL

4 HCl + Fe³⁺ + 4 H₂O → H(H₂O)₄⁺ ;FeCl₄^–  + 3H⁺  …..(1)

H(H₂O)₄⁺ ;FeCl₄^–+ 3BAEE → H(H₂O)(BAEE)₃⁺ ;FeCl₄^– + 3H₂O ….(2)

H(H₂O)(BAEE)₃⁺ ;FeCl₄^– (Aqua.) → H(H₂O)(BAEE)₃⁺ ;FeCl₄^–  (CPL) …(3)

Any concentration of HCl less than optimum value being not enough to reach favorable equilibria and giving decline in extraction efficiency so that any concentration of HCl in aqueous solution more than optimum value effect to decrease extraction efficiency because effect to increase the rate of backward direction of equilibrium.

Effect of Metal Ions Concentration

Extracted Fe³⁺orHg²⁺ according to onium system as detailed in comprehensive method from 10 mL aqueous solutions contain rising quantity of metal ions with existence 1M HCl The results were as in Figures (6 and 7):

Figure 6: effect of metal ions concentration on formation and stability of onium species extracted Click here to View figure

 

Figure 7: D= f [metal ions] Click here to View figure

 

The results appear linear relation between extraction efficiency and metal ion concentration in aqueous solution to optimum value of metal ion concentration equal to 100 µg at constant of other constant conditions, that in mean increasing in onium species formation and partitioning to CPL with increasing metal ion concentration.

Rising BAEE Concentration Effect

Extracted100µgof each metal ion under study in10mL aqueous solutions by rising concentration of BAEE at constant other condition according to comprehensive method, The results were as in fig Figures (8,9) (8 and 9):

Figure 8 : Effect of BAEE concentration on formation and stability of onium species extracted. Click here to View figure

 

Figure 9 : Effect of BAEE concentration on extraction efficient and D value Click here to View figure

 

The results shows linear relation and reflect increasing in onium species concentration formation and stability with increasing concentration of BAEE, that is mean BAEE is un thermodynamic parameter which in it increasing concentration effect to increase that rate of forward direction of formation onium species with increasing concentration of onium species formed.

Thermodynamic

Effect of temperature on extraction efficiency of onium species by joining onium system and CPE methods involved extraction 100 µg in 10 mL aqueous solutions of each ion in presence 1M HCl ,1×10^-4M (BAEE), 0.5 mL 1% Triton X-100 at rising temperature with 15 minutes of heating at each temperature according to comprehensive method. The results were as in Figures (10 and 11).

The extraction method shows 85°C was optimum temperature for extraction Fe³⁺ ion but  95°C for extraction Hg²⁺ after calculated extraction constant K_ex for each ion by following the relation (2).

Diagram log K_exagainst 1/T K as in Figure (12)

Figure 10: effect temperature on formation CPL and extraction Click here to View figure

 

Figure 11: D = f (T°C) Click here to View figure

 

Figure 12: effect of temperature on extraction constant.   Click here to View figure

 

From the slopes of straight lines in fig (12) and relations (3-5) calculated thermodynamic data of extraction as in table (1)

Table 1: Thermodynamic data of extraction.

Metal ions	ΔHex kJ mol-1	ΔGex kJ mol-1	ΔSex J mol-1K-1
Fe3+	0.195	-66.480	186.254
Hg2+	0.0592	-77.981	212.065

 

At the optimum temperature reaching the thermodynamic equilibrium to formation CPL with favorable distribution to CPL to giving best extraction efficiency.

Effect of Heating Time

According to comprehensive method extracted Fe³⁺and Hg²⁺ from 10mL aqueous solutions involved 100µg of each metal ions and 1M HCl,1×10^-4M (BAEE), 0.5 mL 1% Triton X-100. Heating at optimum temperature for rising time. The results were as in Figures (13 and 14):

Figure 13: heating time effect on CPL formation and onium species extracted.   Click here to View figure

 

Figure 14: heating time effect on extraction efficiency and D value. Click here to View figure

 

The results shows (15min.) was the optimum heating time for extraction Fe³⁺ but for extraction Hg²⁺ ion needing (20min.) for heating. Whereas the heating time represents kinetic side of extraction at optimum value reach best equilibrium of CPL with higher density and small volume ,as well as favorable dehydration at any heating time less than optimum not reached to equilibrium so that at heating time more than optimum value increase the diffusion of micelles with decrease in dehydration so decrease in extraction efficiency.

Effect of Surfactant Volume

From 10mL aqueous solutions contain 100µg of Fe³⁺orHg²⁺ ions at optimum condition in existence rising volume of surfactant Triton X-100 according to comprehensive method. The results were as in Figures (15 and 16):

Figure 15: effect of triton X-100 volume on onium species concentration extracted Click here to View figure

 

Figure 16: effect of triton X-100 volume on extraction efficiency and D value Click here to View figure

 

The results shows 0.5ml of TX-100 was the optimum surfactant volume for extraction both ion Fe³⁺and Hg²⁺this volume help to reached the state of critical micelles concentration CMC and produce best CPL enough to extracted higher quantity of onium species, volume less than optimum not allow to CMC, so that volume more than optimum value and by effect of electrostatic interaction between micelles increase diffusion of micelles with decrease in CPL

Effect of Electrolyte Salts

Extracted metal ions according to comprehensive method at optimum condition and in presence 0.01mL of different electrolytes, the results were as in table (2).

Table-2: Effect of electrolyte on extraction efficiency of Fe³⁺orHg²⁺ ions.

Electrolyte salts	Fe3+		Hg2+
	Abs. 362 nm	D	Abs. 293 nm	D
LiCl	1.832	114.45	1.725	218.50
NaCl	1.716	106.31	1.631	183.30
KCl	1.638	99.00	1.510	165.70
NH4Cl	1.601	91.51	1.480	151.40
MgCl2	1.813	109.52	1.646	192.80
CaCl2	1.616	94.53	1.575	171.21

 

The results appear enhancement in extraction efficiency in presence electrolyte in aqueous solutions because the electrolyte doing to destroying the hydration shell of metal ion Fe³⁺and Hg²⁺so that cause increase in dehydration of micelles that is mean increasing in onium species concentration formation and formation good CPL, also appear this effect differ from electrolyte to other according to behavior of electrolyte in aqueous solutions and LiCl giving the higher effect.

Interferences Effect

From 10 mL aqueous solutions extracted 100µg of Fe³⁺orHg²⁺ ions in presence 1M HCl , 1×10^-4 M (BAEE), 0.5mL 1% TritonX-100 and 0.01ml of some interferences at optimum condition according to comprehensive method. The results were as in Table (3).

Table 3: Effect of interferences on extraction efficiencies

Interferences	Fe3+		Hg2+
	Abs. 362 nm	D	Abs. 293 nm	D 40.11 28.65
Ni 2+	0.235	16.56	0.469
Co 2+	0.328	22.12	0.321
Cd 2+	0.807	57.44	0.646	60.34
Cu 2+	0.610	40.57	0.478	47.32
Zn 2+	0.689	43.83	0.701	80.51 54.47
Mn 2+	0.901	63.81          0.512

 

The results appear all metal cation give partially interferences and effect to decrease extraction efficiency because all these metal ion participation in formation onium species and this participation effect to decline  concentration of  HCl, (BAEE), than optimum values needed to extraction Fe³⁺ and Hg²⁺ and this decline in concentration not allow to reached equilibrium of formation and extraction onium species, but by reason of different ability and behavior of these metal cation  in aqueous solutionsso different participation.

Applications

For spectrophotometric determination of Fe³⁺ and Hg²⁺ in different environmental and vital samples followed, the comprehensive method for extraction metal ion under study from 10mL aqueous solutions contain different quantity of metal cat ion at all optimum condition and after separated CPL from aqueous solutions ,and dissolved CPL in 5mL ethanol and measure absorbance for ethanolic solutions against blank prepared in the same method without metal ions, then plot absorbance against ppm of metal ion as in Figure (17)

Figure 17 : calculation curve for spectrophotometric determination of  Fe3+ and Hg2+   Click here to View figure

 

Any sample after preparing treated according to comprehensive method at optimum condition after measure the absorbance and return to calibration curve for each metal ion determine metal ion in the sample.The results were as in table (4) .

Table 4 : Fe³⁺ and Hg²⁺ content (ppm) in different samples.

samples	Fe3+			Hg2+
	Thiocyanate method 18	Applied method*	RSD %	Dithiazone method 18	Applied method*	RSD %
agriculture 1	13.50	13.20	0.12	0.18	0.17	0.02
agriculture 2	20.60	21.00	0.02	0.20	0.16	0.03
Cow meat (Beef)	01.50	01.60	0.14	0.16	0.20	0.01
chicken (breast)	07.20	07.40	0.12	0.16	0.21	0.05
Drainage fish	17.10	16.80	0.02	0.60	0.58	0.09
River water	01.00	00.90	0.01	0.48	0.51	0.01
garden cress	06.30	06.60	0.13	0.40	0.37	0.14
celery	05.00	05.20	0.15	0.10	0.09	0.12
lettuce	06.80	06.50	0.11	0.15	0.10	0.14
cucumber	05.00	05.40	0.01	0.08	0.10	0.17
Tomato	08.60	08.40	0.30	0.04	0.05	0.05

*Values given represent the average of five analysis of each sample.

 

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