Determination of Antidepressants in Human Plasma by Modified Cloud-Point Extraction Coupled with Mass Spectrometry

The Chemometric Evaluation of the Factors Influencing Cloud Point Extraction for Fluoroquinolones

This study aimed to analyze the factors that impact the cloud point extraction of ciprofloxacin, levofloxacin, and moxifloxacin. The following independent variables were analyzed: Triton X-114 concentration, NaCl concentration, pH, and incubation temperature. The dependent variable studied was recovery. A central composite design model was used. The applied quantitation method was HPLC. The method was validated for linearity, precision, and accuracy. The results underwent ANOVA^® analysis. The polynomial equations were generated for each analyte. The response surface methodology graphs visualized them. The analysis showed that the factor most affecting the recovery of levofloxacin is the concentration of Triton X-114, while the recovery of ciprofloxacin and moxifloxacin is most affected by pH value. However, the concentration of Triton X-114 also plays an important role. The optimization resulted in the following recoveries: for ciprofloxacin, 60%; for levofloxacin, 75%; and for moxifloxacin, 84%, which are identical to those estimated with regression equations-59%, 74% and 81% for ciprofloxacin, levofloxacin, and moxifloxacin, respectively. The research confirms the validity of using the model to analyze factors affecting the recovery of the analyzed compounds. The model allows for a thorough analysis of variables and their optimization.

Innovative approaches in cloud-point extraction

Cloud-point extraction (CPE) is a pre-treatment technique for the extraction and preconcentration of different chemical compounds, such as metal ions, pesticides, drugs, phenols, vitamins etc., from various samples. CPE is based on the phenomenon of two phases (micellar and aqueous) forming after the heating of an aqueous isotropic solution of a non-ionic or zwitterionic surfactant above the cloud-point temperature. If analytes are added to the surfactant solution under suitable conditions, they should be extracted into the micellar phase, also called the surfactant-rich phase. Recently, the traditional CPE procedure is being increasingly replaced by improved CPE procedures. In this study, recent advances in CPE over the last three years (2020 - 2022), including the application of various innovative approaches, are reviewed. In addition to the basic principle of CPE, alternative extraction media in CPE, CPE supported by various auxiliary energies, a different modified CPE procedure and the use nanomaterials and solid-phase extraction in combination with CPE are presented and discussed. Finally, some future trends for improved CPE are presented.

Dynamic Microwave-Assisted Micelle Extraction Coupled with Cloud Point Preconcentration for the Determination of Triazine Herbicides in Soil

A green and simple method, dynamic microwave-assisted micelle extraction coupled with cloud point preconcentration, was developed for the determination of triazine herbicides in soil samples. The method has the advantages of those two extraction procedures, which could eliminate the interferences from complex soil samples greatly. Non-ionic surfactant Triton X-114 aqueous solution used as extraction solvent was continuously pumped into soil samples. The resulting extract was heated and centrifuged in the presence of NaCl. After centrifugation, the analytes were enriched into the surfactant-rich phase. No filtration or cleaning steps were required. Several key parameters were investigated. The Box-Behnken design was applied to optimize the experimental factors involved in the dynamic microwave-assisted micelle extraction. Good linearity was observed in the range of 1.00-250.00 μg kg-1. The limits of detection were ranged between 0.26 and 1.71 μg kg-1. The recoveries of analytes ranged from 80.3 to 98.3% with the relative standard deviations ranging from 1.1 to 6.6%.

Polydopamine coated hypodermic needles as a microextraction device for the determination of tricyclic antidepressants in oral fluid by direct infusion MS/MS

In-needle microextraction consists of the confinement of the sorbent, by coating or packing, inside a metallic needle. The size of the needles reduces the eluent requirements providing an efficient preconcentration of the analytes. In this work, hypodermic needles coated with polydopamine (PDA) are presented as microextraction devices to isolate six tricyclic antidepressants from oral fluid samples. The coating consists of the in-surface polymerization of dopamine at pH 8.5 and mild conditions (room temperature and water as solvent). The PDA coating over the stainless-steel surface confers the needles with a high extraction ability towards the target analytes. After the extraction, the eluates were analyzed by direct infusion MS spectrometry, working in multiple reaction monitoring (MRM) mode, which provided a sample throughput of 30 samples per hour. The variables affecting the synthesis (number of coating cycles, the concentration of dopamine, and needle surface pre-treatment) and the extraction (sample salinity, sample loading cycles, and the number of elution strokes) were studied in depth. Under the optimum conditions, a matrix-matched calibration model was built. The limits of quantification are between 2 and 5 ng mL⁻¹ with linear ranges up to 1000 ng mL⁻¹ for all analytes. The precision, expressed as relative standard deviation (RSD), is better than 10% for all analytes. Accuracy was calculated as recovery, and the obtained values are between 84% and 107%. A single-blind assay was also performed to evaluate the suitability of the method for real application.

Hypodermic needles coated with polydopamine for the extraction of antidepressants.