Chemometrics of Solvent Extraction of Mn(II) and Fe(III) Bis(salicylidene) Ethylenediamine Complexes in Acid Medium

In this study, the preparation and solvent extraction parameters of Mn(II) and Fe(III) -bis(salicylidene) ethylenediamine (H2SAL) was modeled with classical statistical analyses processed using SPSS19.0 software. The linear correlation coefficients for Mn(II) was between 59.5 to 1.0 % whereas for Fe(III), it was between 48-1.0%. The F-values, a measure of the significance of the models indicated that all the factors are needed though at differing degrees for the preparation and extraction of the metal complexes. The significance level for each model was lower than 5% and as such the relationship can be generalized to the whole process. The experiments indicated that the solvent extraction combined with modeling method was accurate, efficient, and reproducible and can be applied in industrial scale production.


Introduction
Manganese and iron, the twelfth and the fourth most abundant element in the earth crust has concentrations of 9.50×10 2 and 5.63×10 4 respectively [1][2]. Rustamov and Abbasova (2014) [2] have shown that manganese is present in water, sediment, soil and biological samples due to its cumulative nature and as such affect adversely the central nervous system. Iron on the other hand, has been shown to be important in many biological and biochemical processes but in excess, toxicity and eventual death of organisms have been implicated [3].
In the determination, solvent extraction where the complexone and the extractant reacts with the metal ions in aqueous phase to generate a complex compound which could be retained as aqueous raffinate or transferred into the organic medium is routinely used. Kandil et al. (2012) and Ogwuegbu & Chileshe (2000) [12,13] have shown that this method leads to favourable issues such as simplicity, selectivity, preconcentration, high speed, high range of determination, accuracy, ease of operation, precision, wide pH or acidity range, thermal stability and ease of manipulation.
Bis(salicylidene)ethylenediamine -metal complexes have been implicated to be useful in variety of biological, industrial, photochemical, catalytic and other miscellaneous applications [14,15]. The preparation has always followed the organic synthetic pathways as described by Cozzi [16] without much attention to the solvent extraction method. Similarly, determinations of metal ions in spectrophotometry mainly end in evaluating the spectrophotometric properties such as molar absorptivity, detection limit, quantification limit without attention to the contributions of the various variables and their level of participation and relevance in complex formation and extraction.
This work models the preparation and extraction conditions of the complexes of Mn(II) and Fe(III) with a Schiff bis base H2SAL with a view to determining the relevance of the variables and modeling their field applicability.

Materials and Methods
Analar grade reagents were used.

Measurement and Characterization
All measurement and characterizations involving FTIR, NMR, UV-Vis and melting point have been previously reported [19]. Rotary shaker (RF-12 Remi equipment) was used for all equilibrations and shakings. The concentration of the metal ions were determined spectrophotometrically as described elsewhere [18].The contributions of the various parameters to preparation and extraction of the metal complexes was done using SPSS19.0 software.

Solution preparation
Solution of hydrochloric acid, H2SAL, Mn(II) and Fe(II) were prepared according to literature [19].

Synthesis of H2SAL
Synthesis, characterization and nature of H2SAL have been reported previously [18,19].

Metal Extraction Analyses
Preliminary investigation showed highest percentage extraction to be obtained at acid concentration of 10 -4 M, 0.5% H2SAL solution, temperature of 30 o C and shaking time of 15 min. Solution of metal ions (10 cm 3 ) was added with 10 cm 3 of 10 -4 M HCl solution, 5cm 3 of H2SAL solution and 25 cm 3 of chloroform in a beaker. The mixture was stirred in a magnetic stirrer for 10 min and thereafter shaken for 15 min in a rotary shaker at 300 rpm and 30 o C. The solution was then allowed to stand for 10 min in a separatory funnel and the phases separated. The amount of Mn(II) and Fe(III) ions unreacted and in the aqueous phase was determined spectrophotometrically [18]. The quantity of Mn(II) and Fe(III) ions, (b) and extraction efficiency, (%) indicating the quantity of metal ions complexed with H2SAL is as shown in Equations 1 and 2.
where; = initial amount of Mn(II) and Fe(III) ions, = the equilibrium amount of Mn(II) and Fe(III) ions (mg /mL),Y and Z represents quantity of metal solution and mass of H2SAL.

Statistical Consideration
The experimental conditions for the preparation and extraction of Mn(II) and Fe(III) H2SAL complexes which include time, acid concentration, ligand concentration, temperature and metal concentration was modeled to ascertain the relevance, contribution and significance of the factors in the process. The results are presented in Tables 1 to 10 as analyzed using statistical and inferential method.
In Table 1, the coefficient of correlation between the amount extracted and time, temperature, metal concentration, acid concentration and ligand concentration has multiple R 2 of 0.612, 0.830, 1.000, 0.595 and 0.979 respectively indicating 51.2, 59.5 and 97.9% variance of the amount extracted to be accurate to time, acid concentration and ligand concentration. An examination of Table 2 shows that the F values are significant with ligand concentration having the strongest significant value of 92.158. The F -values show that all the variables, listed have impact on the amount of complex extracted.     Table 5, the coefficient of correlation between the variables, time, temperature, metal concentration, acid concentration and ligand concentration and indicates a strong and direct relationship among the variables with significance level for each lower than 5%.

Statistical and Inferential Analysis on the Extraction of Fe (III) H2SAL Complex
An examination of Table 6 shows that the values are significant with acid concentration having the strong F-values of 9.608. Based on this, it is assumed that the variables, temperature, metal concentration, time, acid concentration and ligand concentration have an impact on the amount of complex prepared and extracted. The regression analysis for generating the possible combination of factors for the preparation and extraction of the complex is shown in Tables 7 and 8.
From Table 9, the relationship among the variables is strong, positive and direct. Also, the significance level for each is lower than 5%, and as such the relation can be generalized to the whole process. In Table 9, the relationship is strong and positive for acid concentration whereas for time, it is weak. This was also observed in the extraction process where the extraction process is mainly acid concentration dependent and some complexes at certain acid concentration showed insignificant variation in time of extraction.

Conclusion
The preparation and solvent extraction qualities of a bis Schiff base have been and modeled. The factors of time, acid concentration, temperature, metal ion concentration and ligand concentration are noted to be significant in complex formation and extraction. Acid concentration of 0.0001M, shaking time of 15 minutes, temperature of 30 o C and ligand concentration of 0.5% were suitable for the complexation and extraction. The relationship among these variables was observed to be strong, positive and direct with the significance level for each lower than 5%, and as such the relation can be generalized to the whole process.

Data Availability Statement
The data presented in this study are available in article.

Funding
The author received no financial support for the research, authorship, and/or publication of this article.

Declaration of Competing Interest
The author declares that there is no conflict of interests regarding the publication of this manuscript. In addition, the ethical issues, including plagiarism, informed consent, misconduct, data fabrication and/or falsification, double publication and/or submission, and redundancies have been completely observed by the author.