An effervescence tablet-assisted switchable solvent-based microextraction (ETA-SHS-ME) strategy for the on-site pretreatment of water samples was developed in this study. The performance of the suggested strategy was demonstrated by the HPLC-UV determination of steroid hormones (testosterone, progesterone, estradiol and hydrocortisone) in water samples. This analytical task was used as a proof-of-concept example. The ETA-SHS-ME procedure involves dissolution of two effervescent tablets containing a solid proton donor agent (oxalic acid) and an effervescency (NaHCO3) agent as well as a source of organic phase (sodium nonate) in water sample. The proton donor agent reacts with the effervescency agent and water-soluble source of organic phase in aqueous sample phase. The pH changing promotes conversion of sodium nonate into a water-insoluble nonanoic acid dispersed by carbon dioxide bubbles generated in situ. After phase separation an organic phase containing steroid hormones is collected and delivered to a laboratory, and HPLC-UV analysis is performed. The linear calibration ranges were from 5 to 500 ng L− 1 for testosterone, from 25 to 750 ng L− 1 for progesterone, from 10 to 1000 ng L− 1 for estradiol and from 50 to 500 ng L− 1 for hydrocortisone. The LODs, calculated from the blank tests based on 3σ, were 2, 8, 3 and 17 ng L− 1, respectively. The method was successfully applied to the analysis of river samples.
Novelty Statement.
In this research, for the first time, the effervescence tablet-assisted switchable solvent-based microextraction (ETA-SHS-ME) approach was developed and successfully applied for on-site sample pretreatment of water samples. The organic phase is generated in situ in the ETA-SHS-ME procedure compared to the reported in literature effervescence-assisted microextraction approaches. This feature allows to implement microextraction from a large volume of the aqueous sample phase with extremely high enrichment factors. The manufacturing of effervescence tablets for ETA-SHS-ME is simple due to all agents used are solid substances, which can be easily mixed and compressed.
The ETA-SHS-ME was coupled with the HPLC-UV method for the first time and applied for the determination of testosterone, progesterone, estradiol and hydrocortisone in river samples. The effervescence-assisted microextraction procedure was implemented for the determination of steroid hormones in water samples for the first time.
