Application of dual cloud point extraction for the enrichment of zinc in serum samples of psychiatric patients prior to analysis by FAAS

It is reported in literature that zinc (Zn2+) has antidepressant activity. In present study Zn2+ was analyzed in blood serum of male patients having various psychiatric disorders (schizophrenia, depression, bipolar). As it is usually present in trace levels. Hence a novel, environmental friendly, dual-cloud point extraction (d-CPE) method was developed for the enrichment of its trace levels in acid digested serum samples. In the first step of d-CPE, Zn2+ was complexed with 1-(2-pyridylazo)-2-naphthol (PAN), and the complex was entrapped in a nonionic surfactant (Triton X-114). After achieving cloud point by heating, the mixture was separated into two layers i.e. aqueous and surfactant-rich by centrifugation. In second step of d-CPE, the analyte complex in the surfactant-rich phase was treated wih acid to extract back the metal analytes in acidic aqueous phase, the mixture was again heated upto cloud point and the whole procedure was repeated. This time the aqueous phase, having the metals, was taken and subjected to FAAS using conventional nebulization. The accuracy of the developed methodologies (conventional and d-CPE), were verified by their application to certified reference material of serum (CRM). Reliability of the method was checked by relative standard deviation (%RSD), which was found to be <5%. The limit of detection and limit of quantification were calculated for the proposed method as 1.09 μg/L, and 3.63 respectively and enhancement factor was found to be 40. The developed procedure was successfully applied to the serum samples of patients (male) having different psychiatric disorders and non-psychiatric control subjects for the determination of Zn2+.