Spectrophotometric determination of Chroumium (III) with (Chromazurol S)

 

Husham Fathel Hashem¹, Iman Essam Arif², Dr. Alaa Frak Hussein³

¹Directorate General of Education, Karbala, Iraq

²University of Karbala, Production Engineering and Metallurgy, Iraq

³Prof. University of Karbala, College of Dentistry, Iraq

 

ABSTRACT:

Chromazurol S reagent from violet complex with chromium (III) in wave length (550 nm). The complex was found to be stable for at least 2 hour the given pH. Beers^, law is obeyed in the concentration range (1.923×10^-5- 2.693×10^-5 M) with molar absorptivity of (1.233×10⁴ L.mol^-1. Cm^-1). The stoichiometry of complex was confirmed by using mole ratio and molar method which indicated the ratio of reagent to metal is (3:1). Measuring conductivity at room temperature the ionic character of the complex. Has been appointed the melting point of the complex and found that the degree of melting is (231-233C). The study of several factors, including the interactions resulting from the presence of positive or negative ions effect, masking agents, reagent concentration, reaction time sequence of additions.

 

INTRODUCTION:

This reagent is known as Chromazurol S and is synonymous with Ch. S and has other terms in some literature (Alberon, Chromoxan pure Blue, Gallo chrome Briuiant Blue B). Which is in the two formulas described below.

 

[3-Sulpho-2,6-dichloro-3-dimethyl-4-hydroxy fuchsone-5,5-dicarboxylic acid]

 

This pH is red-orange at pH = 3-4 and yellow at pH = 4. At pH higher than 8, it shows a higher absorption at 427 nm.) The Chromazurol S detector can have crystalline complexities with a number of metal ions (2).

 

These complexities are extracted by organic solvents when positive ions are present on the surfaces. Molecular absorption in this case is significant (3)

 

Chromium ion has been widely appreciated in a number of spectral methods. Borges and the group (4) were able to estimate chromium ion based on the effect of oxidation with chloride roots. The researcher also used Ukwueze and his group (5) reagent (3, 3,4,5,7-pentahydroxyflavylium) to estimate chromium and cadmium ion. The study (6) was able to conduct a chromium ion spectroscopy us triple detector(2-Hudroxybenzaldiminoglycin) at the wavelength (565nm) and in another study (7), the small quantities of the chromium element in the alloys were estimated using the 2-Thiazolylazo resorcinol. The purple complex showed a peak absorption at 445 nm.) Ionic monocrystalline ion and chromium were estimated using a detector (4,4-Bis (di methyl amino thio benzo phenoet). The present study aims at the possibility of using the Chromazurol S reagent to quantify the chromium element and to know the best conditions for the work measures and to assess the accuracy and compatibility of the proposed method.

 

Chemicals and reagents:

That all the chemicals and reagents used were of high purity (A.R. Grade)

1 The standard solution for chromium trioxide at a concentration of (1mg/mL) was achieved by dissolving (0.769 gm) of water chromium nitrate [Cr (NO3) 2. 9H2O] in 100 mL Distilled water.

2 - The solution of the reagent (Chrome Azurol S) concentration (1.858 * 10-3 M) to melt (0.1gm) of the reagent with distilled water and complete the volume to (100ml) in a volume vial.

3 – M⁺² , Cu⁺² , Ca⁺² , Na⁺¹ , La⁺³ , Zn⁺² , were prepared with a concentration of (1.00 × 10-4 M) By dissolving weights calculated in distilled water. And complete the volume to (100 mL) distilled water.

4. The negative ion ions (SCN^-1, C₄ H₄ O₆, Cr₂O₇ ⁼, Br^-, CH3COO^-, SO₄ ⁼, F^-) were synthesized from the calculated solids of the salts used for these ions in the form of ammonium salts in 10 ml of distilled water

 

Instruments:

1    [Single Beam UV-visible Spectrophotometer LKB 4050 – 012 (England) ]

2    [pH-meter-(Pw.9421) – PHILPS].

3    [Digital conductivity Meter-PHILPS-England].

4    Atomic absorption spectrophotometer – 670 Shimadzu Japan

 

(Procedure):

(Preliminary investigation):

1-Preparationofthe triple chromium complex:

Prepare the 3-D chromium complex in the acid medium by mixing (1ml) of ion solution (Cr⁺³ ) at a concentration of (1.923 × 10^-4 M) with (10ml) of the detector solution at a concentration of 1.86 × 10-5 M, Acid function at (pH = 4) using hydrochloric acid solution (1M) or sodium hydroxide (1 M) followed by complete volume to (25 ml) with distilled water.

 

2. The absorption spectrum of the solution (Chrome Azurol S 0.1%) dissolved in distilled water was recorded. The absorption peak was found at (λmax = 461 nm) as shown in Fig. 1).

 

 

(Figure 1): - Absorption spectrum of the reagent solution

 

Figure (2): - absorbance spectrum of complex

 

Study the best conditions to be complex:

Several variables have been studied that affect the absorption of the complex and determine the optimal conditions for the formation of the complex using the spectral method for the purpose of obtaining a high sensitivity and good selectivity represented by the following:

 

1 - Effect of acid function (Effect of pH):

A series of complex nickel-biodegradation solutions (Ch. S), the concentration of Cr⁺³ ion (1.923 × 10 ^-4 M), was synthesized by mixing 1 ml of ion solution (1.923 × 10^-4 M) with (10 mL) of the reagent solution (2.79 × 10^-5 M). The acid function was modified at different values between pH (1-10). The mixture was then transferred to a (25 mL) volume flask and supplemented to the mark.

 

The results of this study, which are shown in Figure 3, show that the chromatic intensity of the complex solution gradually increases to peak at acidic pH (4), where the complex is magenta, which represents the optimum pH value to reach the highest absorption , The ionic intensity of the complex increases with the acidic function of this limit, and may be due to the beginning of deposition of element ions or due to the complexity of unstable ions (9,10).

 

Figure (3) Effects of pH value

 

2 - Effect of Additive Succession:

To determine the effect of the addition of the reaction components on the absorption of the complex, three additive sequences were adopted, as shown in Table (1).

 

Table (1): - Effect of additive sequencing in the absorption of the triple chromium complex using (1.923 × 10-4) of the ion and (2.79 × 10-5 M) of the reagent at acidic function (pH = 4)

 

Showed the effect of the absorption value, gave the succession of the second and third additions of the mixture lower absorption, and may be due to the competition of ions negative acid or base in the bond with the metal, which leads to lower absorption values. This is indicated by other studies (8,11,12). Therefore, the sequential sequencing of the addition is recommended in the nickel estimate in this manner.

 

3- Effect of Time on Stability of the Complex:

The results of Table (2) show the follow-up of the reagent reaction with the ions with time using the best conditions mentioned above. These results indicate that the chromium triangles are complex and that the complex remains stable (in terms of absorbance values) for 120 minutes of continuous experimentation. The results of this study reinforce the use of this reagent as one of the reagents used to estimate the triangular chromium element and is considered as one of its positive responses. 20)).

 

Table (2): - Effect of time in complex absorbance using (1.923 × 10^-4) of Cr⁺³ with (2.79 x 10^-5 M) of reagent at pH= 4

 

4-Effect of Reagent Concentration:

He studied the effect of changing the concentration of the detector in complex formation. Table (3) presents the results obtained through this study, which show that the absorption values of the complex increase to peak at the addition of (2.798 × 10-5 M) of the reagent solution. This is due to the interaction between the metallic ions and the detector in the direction of complex formation and giving better Color intensity.

 

As the concentration of the reagent continues to increase, the absorption values begin to decrease. This may be due to the formation of new varieties in the solution that are absorbed at different wavelengths and possibly to the condensation of the ions or the solubility of the reagent with the solvent completely. That the behavior of the detector in this study is similar to that found by researchers in other spectral studies (13,14). Or decomposition studies using different detectors (15).

 

Table (3): Effect of addition of different concentrations of reagent in the absorption of the complex using (Cr. 3) (1.923 × 10-4) and (pH = 4)

5 – Effect of the addition of cation activating surfaces

The effect of adding a limited concentration of surface activator (CTMABr)

 

(Cetyl triethyl ammonium bromide) at a concentration of 0.01 m. The results are shown in Table (4)

 

Table (4): Effect of pH on the presence of activated material (CTMABr) in the absorption of Cr + 3 using the concentration of (1.923 × 10^-4 M) of the ion (2.798 × 10^-5 M) of the detector with the addition of (1 ml) (CTMABr) at a concentration of 0.01

 

The results of this study show that there is little or no effect of this substance on the absorption values of the nickel-dipole complex, which is similar to that found by other researchers (16, 17).

 

6- Construction of the calibration curve (Construction of Calibration Curve):

Figure 4 shows the linearity of the calibration curve obtained under optimal conditions for a range of concentrations between (1.923 × 10-5-2.663 × 10-4 M) and a molar mass of 1.233 × 104 L.mol-1.Cm-1 (104 - 105 L.mol.-1Cm-1). This gives a good indication that the method is highly sensitive and can be used to estimate the chromium triangles in low concentrations.

 

Concentrations of metal ([M] X 10^-5)

 

7- (Determination of Stoichiometry of the Complex):

To determine the complexity of the complex, the following methods have been employed:

 

a- (Mole Ratio Method):

Using a fixed and known concentration of chromium ion (1.538 × 10^-4 M) with increasing and proportional concentrations of the reagent used in this study ranged from (0.769 × 10 ^-4 - 9.228 × 10^-4). The results of this study showed that the decomposition of the extracted complex is (1: 3) as shown in Figure (5) and Table (5)

 

Table (5): Mole ratio methods

C Concentration (Ch. S) [L]	C C L: CM	A Abs. of N Ni+2Ch.SComplex
0. 0.769X 10 -4  1. 1.538 X 10 -4  3. 3.076 X 10 -4  4.614 X 10 -4  6 6.152 X 10 -4  7 7.690 X 10 -4 9.228×10-4	0. 0.5 1. 1.0  2 2.0  3 3.0  4 4.0  5 5.0  6.0	0 0.125 0. 0.176 0. 0.268 0. 0.378 0. 0.398 0. 0.411 0. 0.422

 

The value of the complex stability constant in the acid medium is calculated as follows:

 

M+ 3 + L                                      ML3

αc         2αc                                     (1- α)c

 

              [ML 3]

 K =                                                                               (1)

            [M+2][L-] 3

 

whereas:

M ^{+ 3} is the metal ions Cr ^{+ 3}

L^- is the embryo (Ch. S)

If α is the degree of disintegration and (C) the molar concentration of the complex, equation (1) is written as follows

 

              (1- α)

K=

           αc (2αc) 3

 

                 Am – As

α =                                                                                           (3)

                    A_m

whereas
As = Absorption of the complex at the point of equivalence

Am = absorb the complex at the greatest value (17). Of Table 6), it is clear that the complex has a high stability, which enhances the possibility of using the detector (Chromazurol S) in the spectral assessment of this element.

 

Table (6): - The value of K complex stability

 

B. [Molard Method]:

In this way were:

1. Mix (1 ml) of the metal solution at a constant concentration (1.70 * 10-4 M) with an increase of the detector solution at a concentration of 3.344 × 10-3 M after adjusting the acidic function at pH 4 and then taking the absorption) Was found to be (Am = 0. 563).

 

2. Mix (1 ml) of the reagent solution at a concentration of 4.66 × 10-5 M with an increase of the metal at a concentration of 1.923 * 10-3 M). After adjusting the acidic function at pH (4) It is equal to (Al = 0. 182).
It is the relationship:

 

m CM + lC_L                            M_ML_L

 

              0.563                                Am

m/l =                                =                            = 3.09

                 A_l                                    0.182

 

This means that the correlation between the detector and the fractions (1: 3). Thus, it is clear that the two methods employed in this study confirm the correlation of the detector with 1

 

8 -Effect of inter ferrous:

The absorption values of the chromium triplex with the reagent (Chromazurol S) were measured after the addition of positive and negative ions with the spectral ion in experimental conditions obtained during the study. The results of this study are shown in Tables 7 and 8). These results show that the presence of certain ions during the process of forming the chromium complex with the reagent has a different effect on the value of the absorption of the complex depending on the nature of the added ion and its concentration (18.19)

 

 

 

Table 7: Effect of adding some positive ions with different concentrations in the absorption value of the triple chromium complex with the reagent at (3.41 x 10-4 M) and pH (4)

 

Table (8): Effect of addition of some negative ions at different concentrations in the Chromazurol S-Cr + 3 with a standard concentration (3.41 * 10-4 M) and acidic function at pH (4)

 

9. (Effect of Masking agents):

For the purpose of determining how to use the blocking factors on the selective chromium ion chromatography with positive ions, 1 mL was added at a concentration of 0.01 m from some blocking factors as shown in (Table 9).

 

(Table 9): Add -total (1 ml) of Masking agents in the absorption of complex Cr + 3 concentration (2.798 x 10-4 M) function when acidic (pH = 4)

Note from Table 9 that all of the solutions listed in the table complicate the Cr + 3 ion. Therefore they cannot be used as blocking factors for their estimation with the detector

 

10 Determination of the melting point of the complex:

The chromium complex was determined by a triple chromosome with the study reagent found to be complex at a temperature ranging from 231-233 ° C. The differences between melting point values 215-210 ° C () at the degree of disintegration of the complex prove the complexity of the complex and indicates the partial weight gain of the complex compared with the partial weight of the detector used.

 

11 (Measurement of Conductivity):

Molecular conductivity of the complex was studied at room temperature and under optimum conditions and the result is shown in Table (10).

 

Table (10): Molecular conductivity of the complex

 

Since conductivity is a measure of the ability of electrolyte solution to charge electricity through the migration of ions under the influence of an electric field, it is clear from the table that the complex is ionic complex.

 

(Statistical Treatment of the Results):

The relative standard deviation (RSD) and relative error were used as a measure of compatibility and accuracy of results by preparing three chains of nickel ion solution at different concentrations (2.726 × 10-4. 0.044 × 10-4.1.363 * 10-4 M) with the Chromazural S ) Using distilled water solvent. The absorption was repeated five times for each concentration and the results were then calculated to calculate the RSD value as shown in Table (11).

 

 

 

 

Table (11): Consistency and accuracy of the method to estimate ion(Cr3

 

The results of Table (11) showed that the relative standard deviation was between 0.408 and 2.233% by using different amounts of metal ion. The relative error value is between (-0.348%) and (0.764%).

 

Sensitivity of the Spectrometric Method in Determination of Chromium (III):

The term limit was used to denote the sensitivity of the method used to estimate the chromium triglycerides and thus determine the lowest concentration of the chromium ion in this way. The method showed that the minimum concentration that can be determined by this method is nickel (10-6 m) (3.462), which indicates that the method used is highly sensitive and successful (21).

 

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Received on 15.02.2019           Modified on 20.03.2019

Accepted on 28.04.2019         © RJPT All right reserved