Preconcentration of Trace Heavy Metal Ions in Textiles and Determination by Flame Atomic Absorption Spectrometer

Abstract

In this thesis, a simple, low-cost, and green effervescence-assisted dispersive liquid-liquid microextraction based on deep eutectic solvent (EA-DES-LPME) method was developed for separation, preconcentration, and determination of lead, copper, nickel, and cobalt in cotton textile products in different colors that collected from various fabric shops in Ankara, Turkey, prior to analysis with flame atomic absorption spectrometry (FAAS). The complexation of metal ions was carried out by using 0.1 % (w/v) 8-hydroxyquinoline (8-HQ) as a complexing agent. The deep eutectic solvent was prepared by mixing choline chloride (ChCl) and phenol (Ph), where used as an extraction solvent. In this method, the dispersion of the extraction solvent is achieved by effervescence reaction, which is performed by carbon dioxide bubbles production. The effervescent agent is environmentally friendly and only produces an increase in the ionic strength and a negligible variation in the pH value of the aqueous sample, which does not interfere with the extraction of the analytes. For this purpose, a special tablet containing ascorbic acid (AA) as a proton donor and sodium carbonate (SC) as a carbon dioxide source in a certain molar ratio was used. THF was utilized as an aprotic solvent and allows the extraction solvent to separate from the aqueous phase by self-aggregation. All parameters related to the effervescence agent and deep eutectic solvent that affects the extraction efficiency were investigated and optimized in detail, as well as the effect of pH, and the amount of 8-HQ and THF. As a result of the optimization studies, the highest extraction efficiency was achieved when pH is 6.0, effervescence tablet composition is (AA: SC) with (2:1) molar ratio, effervescence amount is 0.457g powder or 2 tablets, effervescence time is 2.5 min, DES volume is 1000 µL and synthesized from ChCl: Ph at 1:3 mole ratio, 8-HQ volume is 750 µL, and THF volume is 1000 µL. Under these optimal conditions, the analytical performance of the proposed method was evaluated based on the enhancement factor (EF), limit of detection (LOD), limit of quantification (LOQ), percent recovery, and accuracy criteria. When applying the EA-DES-DLLME method under optimum conditions for Pb (II), Cu (II), Ni (II), and Co (II) the results are as follows: the EFs are 62.5, 52, 57.5, and 52.5 respectively; the LODs in µg L-1 are 2.44, 1.29, 0.58, and 1.55 respectively; the LOQs in µg L-1 are 8.13, 4.30, 1.93, and 5.16 respectively; the percent RSDs (n=10) are 1.07, 1.61, 1.35, and 1.97 respectively. In addition, the method was applied to the real samples (different cotton textiles with different colors), and the recovery results were found as follows: 97.20 – 101.70 % for Pb (II), 97.60 – 101.92 % for Cu (II), 95.65 – 104.35 % for Ni (II), and 96,76 – 101.52 % for Co (II). The concentrations of these trace metal ions in cotton textile samples were found to be in the range of 0.26 – 7.52 µg g-1 Pb (II), 1.27 – 77.35 µg g-1 Cu (II), 0.66 – 5.00 µg g-1 Ni (II), and 0.64 – 5.58 µg g-1 Co (II). On the other hand, it was revealed that the matrix effect is not important in the method and the method can be applied to real samples with high accuracy and sensitivity.