Preparation and Analytical Studying of Ligand (NO2BTAHB) with

(Cu) - Ion

 

Aqeel  Mahdi Jreo*

Department of Chemistry, Collage of Science, University of Kufa, Kufa, Iraq

*Corresponding Author E-mail: aqeel-me79@gmail.com

 

ABSTRACT:

In this study, organic reagent  2-[6-Nitro-2-benzothiazolylazo]-4-hydroxy benzoic acid (NO2BTAHB) was synthesized. A sensitive and selective spectrophotometric method was proposed for the rapid determination of Cu(II) using (NO2BTAHB)  reagent .The reaction between Cu(II) and (NO2BTAHB)  reagent is instantaneous at pH=6.0 and the absorbance remains stable for over 24 hrs.

The Method allows for the determination of Cu(II) over the range (0.1-6.0) μg.ml-1 ,with molar absorptivity of (7.45 x 10+3)l.mol-1.cm-1 and a detection limit of 0.0245μg.ml-1.Recovery and relative error values of precision and accuracy of method were found to be R.S.D=1.7% , Re=98.6% , and Erel =-1.4% . The properties of complex was studied and show; (M:R) ratio was 1:2 at pH=6.0 ,and the stability constant of 7.796 x 10+9L2.mol-2 . The interferences of ions (Ni2+ , CrO2- , Ca2+ , pb2+,Cu+2,WO4-2,MO4-2, Co2+ , Mg2+ , Cd2+, Ba2+ , Bi3+) and masking agents effect on absorbance were studied .

 

KEYWORDS: Human , purified , nutrient , toxic , level.

 

 

INTRODUCTION:

Copper plays a different role in the human body. It is an essential nutrient or a toxic element for human beings, depending on the concentration level [1,2]. Some chromogenic reagents have been used in spectrophotometric methods of determination of copper such as Acetophenone-p-chlorophenylthiosemicarbazone[3], Hydrazinecarboxymide-2-[(2-hydroxyphenyl) methylene (HC22HPM)[4], Piperazine[5],Chloro(phenyl) glyoxime[6], sodium(I) diethyldithiocarbamate[7], brilliant cresyl blue(BCB)[8], cefixime[9], 4-(6-Bromobenzothiazolylazo) Orcinol[10], 3-(2′-thiazolylazo)-2,6-diaminopyridine[11], 2-[2-(4-methylbenzothiazolyl) azo]-5-dimethylamino benzoic acid[12],2[2-(5-bromo thiazolyl) azo]-4-methoxy phenol[13], and 2,6-dichlorophenolindophenol[14] .

 

Thiazolylazo compounds have attracted the attention , as they are sensitive chromogenic reagents in addition to being important complexing agents. These dyes are useful in spectrophotometric determinations due to their good selectivity over a wide range of pH and they are relatively easy to synthesize and purified [15].

 

In this paper, a new (NO2BTAHB) chromogenic reagent was synthesized for spectrophotometric determination of Cu(II).

 

Reagents:

All reagents were of analytical grade. Freshly distilled and deionized water was used for solutions preparations.

Preparation of reagent [16]:

To a mixture of {(4.3 gm of  4- nitro aniline and 3.8gm of ammonium thiocyanate ) in 70 ml glacial acetic acid }, was added drop by drop from burette (1.2 ml Br2 + 15 ml glacial acetic acid ) keeping at temperature >10 Cº. After 15 minutes alkaline solution was added to precipitate the thiazole derivative, 1.145 gm of thiazole and in 50 ml glacial acetic acid then add (5 ml conc. HCl + 25ml water ) to the solution . After that drop by drop from burette a solution ( 0.690 gm NaNO2 + 50 ml H2O ) with stirring at 0-5 Cº to diazonium salt , then ( 0.1.390 gm of parahydroxy benzoic acid + 50 ml ethanol )is added to diazonium salt and 2-[6-nitro-2-benzothiazolyl azo]-4- hydroxy benzoic acid (NO2BTAHB)organic  reagent was formed .

 

 

Standard solutions:

Stock Cu (II) solution- A solution of Cu (II) ( 100 μg.ml-1) was prepared by dissolving ( 0.0392) gm of CuSO4. 5H2O in (100ml) distilled water. Other standard solutions of Cu(II) were prepared by dilution of stock solution with distilled water. -1x10-3 M (NO2BTAHB)standard solution was prepared by dissolving (0.088)g in 250 ml of absolute ethanol .

 

Buffer solution [17] (pH=6.0) was prepared by mixing 12.63ml of (0.2)M Na2HPO4 (which was prepared by dissolving 2.83 gm in 100 ml distilled water) and 7.37 ml of

(0.1)M Citric acid (which was prepared by dissolving 1.92 gm in 100 ml distilled water) .

 

Apparatus:

Spectrophotometric measurements were made with a Shimadzu (UV-Vis.) scientific equipment with 1.0 cm cell for plot spectra .The pD-303. Spectrophotometer, APEL, Japan was used in the other measurements. The pH-meter, 720 WTW, Germany, and FT-IR Spectrophotometer Shimadzu., Japan, were used in this work.

 

Procedure:

To an aliquot containing ≤ 10μg .ml -1 of Cu(II) in a 10-ml volumetric flask, was added 2 ml of buffer solution , and 3.5 ml of (2x10-4M ) of (NO2BTAHB) solution. The solution was diluted to the mark with distilled water, and absorbance was measured at 25Cº and wave length of 618 nm against the reagent solution as a blank  solution prepared under the same conditions.

 

RESULTS AND DISCUSSION:

1-FT-IR spectrum of reagent (NO2BTAHB)

The following table shows the main vibration frequencies of main absorption bands characteristic of reagent

 

Wave number (Cm-1)

Groups

3300-3400

γ O-H , H2OCrys.

2870

γ C – H Aliphatic

3020

γC – H Aromatic

1740

γC =N

1505

γ N=N

1422

γC =C

1128

γC – S

1280

γC – O phenolic

1678

γC = O carboxylic

1362

γC – N

 

 

Fig.1: FT-IR spectrum of reagent (NO2BTAHB)

 

 

2-Properties of the (NO2BTAHB)

(NO2BTAHB) reagent is slightly soluble in water, red powder, orange and stable solution for suitable period time, but in basic medium pH≥ 8.0 the solution being pink .Such behavior may be interpretated by the following equilibria;

 

 

Fig.2: UV-Visible spectrum of  (NO2BTAHB) reagent

 

Study of Cu(II) –(NO2BTAHB)complex:

 

Absorption spectra

a-Ultra violet –visible absorption spectra of (NO2BTAHB)reagent ,and Cu(II) -(NO2BTAHB)complex solution are shown in fig (3).The reagent showed an absorption maximum at 439 nm,and the complex at 618 nm.

 

Fig.3: UV-Visible spectrum of  Cu(II)-(NO2BTAHB) complex

 

 

FT-IR spectrum of Cu- (NO2BTAHB) complex:

Changing in intensities, shift in peaks positions, and fission in azo peak were seen which indicate to formation of  complex as in following figure.

 

Fig.4: FT-IR spectrum of Cu(II) –NO2BTAHB)complex.

 

Effect of pH

The effect of pH was studied over the rang (2-9) adjusted by means of dilute HCl and NaOH solution. Figure (5) shows the relationship between absorbance and pH,where the maximum absorbance obtained in the range of pH =(4.0-7.5) .At 7.5< pH< 4.0 a decrease in absorbance. Therefore, the optimum pH was 6.0, where the absorbance was maximum and constant.

 

Fig (5); Effect of pH on absorbance Cu(II) –(NO2BTAHB)complex.

 

Effect of time

The stability of complex was studied from (0 – 120) min. with 5 minutes. Intervals up to 24 hrs. the maximum absorbance was reached at 10 minutes figure (6) after that

the absorbance remains constant.

 

Fig (6); Effect of time on the stability of Cu(II)–(NO2BTAHB) complex.

 

Effect of temperature

The effect of temperature on absorbance of complex was studied; the study was performed at temperature between       (5 – 80)ºC .Fig (7)show the maximum absorbance obtained at temperature range ( 15 -40 ) ºC which was regarded as a proper temperature of complex formation . At temperatures higher than 40 ºC the absorbance decreases due to dissociation of complex gradually.

 

Fig (7); Effect of temperature on the stability of Cu(II)–(NO2BTAHB)complex.

 

Determination of stoichiometry and formation constant

The composing of complex was studied by jobs method of continuous variations and mole ratio method [18] . Fig (8,9) both methods indicate that the ratio of metal ionto reagent molecules ( M:L) was (1:2) at pH = 6.0 .

 

The formation constant calculated by applied procedure , was found to be (7.796 x10 +9 ) L2. mol-2 .

 

Fig(8): Mole ratio plot ,pH =6.0

 

 

Fig(9): Jobs plot , pH=6.0

 

Suggestion of structural formula of Cu(II) –(NO2BTAHB) complex

From the obtained results of metal to reagent ratio, and depending on thiazolylazo.

Compounds  properties; the following structure can be suggested;

 

Analytical characteristics:

Calibration curve

Linear calibration graph through the origin was obtained which obeyed Beers law over the range ( 0.1 – 6.0 ) μg. ml-1 of Cu (II) . The average molar absorptivity was found to be (7.45 x 10 +3)l. mol-1.Cm -1 . The sandells sensitivity [19] was (0.0088) μg of Cu (II).Cm-2 , and correlation coefficient (r) was 0.992.

 

Fig (10): calibration curve of Cu(II) –(NO2BTAHB) complex

 

Precision and Accuracy:

The relative standard deviation ( R.S.D %) , evaluated from seven independent determination of 3.0 μg. ml -1of Cu(II) was 1.7 %, this result show that this method is highly precise . Also the accuracy of this method was determined by calculated the Erel % for 3.0 μg . ml -1 standard solution of Cu(II) which was found to be (– 1.4 ) and Re% = 98.6 .

 

Interferences

The effect of the ions (Ni2+, CrO2-, Ca2+, pb2+, Cu+2, WO4-2, MO4-2,  Co2+, Mg2+, Cd2+, Ba2+, Bi3+)  which form complex with the reagent during its reaction with Cu(II) were studied. On the other hand, suitable masking agents examined for eliminating the effect of the twelve ions, where the mixture of KI, NaF, Na2S2O3, and  DMG  were found to be a suitable masking agents.

 

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Received on 02.03.2015          Modified on 15.03.2015

Accepted on 25.03.2015      ©A&V Publications All right reserved

Research J.  Science and Tech. 7(1): Jan.-Mar. 2015; Page 01-08

DOI: 10.5958/2349-2988.2015.00001.7