Biocompatible chitosan-zinc oxide nanocomposite based dispersive micro-solid phase extraction coupled with HPLC-UV for the determination of rosmarinic acid in the extracts of medical plants and water sample.

In the present research, a procedure was described for the recovery of rosmarinic acid (RA) from medical extract samples using chitosan­zinc oxide nanoparticles as a biocompatible nanocomposite (CS-ZnO-NC). The dispersive micro-solid phase extraction (D-µ-SPE) of RA from the medical extract samples was investigated by using the prepared biocompatible composite as a solid phase. The HPLC-UV method was used for measuring the extracted RA. The important variables (pH, biocompatible composite mass, contact time, and volume of eluent) associated with the extraction process were analyzed by the application of central composite design (CCD). The achieved optimum values for the mentioned variables were 7.0, 10 mg, 4 min, and 180 µL, respectively. The extraction recovery (99.68%) obtained from the predicted model was in agreement with the experimental data (98.22 ± 1.33%). In addition, under the obtained optimum conditions and over the concentration in the range of 2-3500 ng mL-1, a linear calibration curve was obtained with R2 > 0.993. The limit of detection (LOD) and quantification (LOQ) values were computed, and the obtained ranges were respectively from 0.060 to 0.089 ng mL-1 and 0.201 to 0.297 ng mL-1. In addition, the enrichment factors were obtained in the range of 93.7-110.5 with preconcentration factor of 83.3. Therefore, the D-µ-SPE-HPLC-UV method could be used for analyzing RA in the samples of the extracts obtained from the medical plants and water with the recovery values of the analyte in the range of 96.6%-105.4% and the precision with relative standard deviation <5.7%.

Ultrasound combined with manganese-oxide nanoparticles loaded on activated carbon for extraction and pre-concentration of thymol and carvacrol in methanolic extracts of Thymus daenensis, Salvia officinalis, Stachys pilifera, Satureja khuzistanica, and mentha, and water samples.

A dispersive micro solid-phase extraction (DMSPE) technique was developed using manganese-oxide nanoparticles loaded on activated carbon (Mn3O4-NPs-AC) as an effective sorbent combined with ultrasound for the extraction and determination of a trace amount of thymol and carvacrol in methanolic extracts of Thymus daenensis, Salvia officinalis, Stachys pilifera, Satureja khuzistanica and mentha, and water samples. Thymol and carvacrol phenolic compounds were extracted from real samples using acetonitrile (ACN) as the desorption solvent. Using central composite design (CCD), the effects of pH, ionic strength (NaCl), nano-sorbent mass, contact time, and desorption volume were investigated. Additionally, based on five-level variables, response surface methodology was used to determine the individual and interactive effects between factors on the process. The optimized extraction conditions included 12 mg of Mn3O4-NPs-AC as the sorbent, 300 µL of ACN as the desorption solvent, pH 3.0, 0.5 w/v% of NaCl, and 4.5 min sonication time. Under the optimized conditions, for all the samples, the limits of detection were 0.054-0.104 ng mL-1 and the limits of quantification were 0.178-0.345 ng mL-1. The correlation coefficients of the calibration curves were >0.985, i.e. in the range of 0.4-6000 ng mL-1. To validate the effects of the matrix, the recovery, reproducibility, repeatability, and overall uncertainty were calculated for the five methanolic extracts, at 50, 100, and 500 ng mL-1. The recovery ranged between 94.5% and 109.0% with a relative standard deviation of <8.0% for the repeatability and reproducibility precision, which strongly supports the favorable repeatability and reproducibility of the method. The presented method also has the excellent sorbent features of NPs for the sorption of the analyte, which is due to the use of ultrasound for dispersion of the material in the sample matrix.

Cu- and S- @SnO2 nanoparticles loaded on activated carbon for efficient ultrasound assisted dispersive µSPE-spectrophotometric detection of quercetin in Nasturtium officinale extract and fruit juice samples: CCD-RSM design.

A simple, rapid, and efficient method of dispersive micro solid phase extraction (D-µ-SPE) combined with UV-Vis spectrophotometry via ultrasound-assisted (UA) was applied for the determination and preconcentration of quercetin in extract of watercress (Nasturtium officinale), fruit juice and water samples. The sorbent in this method was synthesized by doping copper and sulfide into the tetragonal structure of SnO2-nanoparticles (Cu- and S- @SnO2-NPs) and subsequently loading it on activated carbon (AC). The D-µ-SPE parameters with direct effect on the extraction efficiency of the targeted analyte, such as sample pH, volume of eluent, sorbent mass and ultrasound time were optimized using central composite design method. Under optimized conditions, the calibration graph for quercetin was linear in the range of 20-4000 ng mL-1; the limit of detection and quantitation were 4.35 and 14.97 ng mL-1, respectively and the enrichment factor was 95.24. Application of this method to analyze spiked extract, fruit juice and water samples resulted in acceptable recovery values ranging from 90.3% to 97.28% with intra-day and inter-day relative standard deviation values lower than 6.0% in all cases. Among the equilibrium isotherms tested, Langmuir was found to be the best fitted model with maximum sorption capacity of 39.37 mg g-1, suggesting a homogeneous mode of sorption for quercetin.