Sequential Injection Chromatography with Monolithic Column for Phenothiazines Assay in Human Urine and Pharmaceutical Formulations

Methods: Sequential injection chromatography (SIC) with monolithic column has been proposed with potential benefits for separation and quantification. Objective: To utilize SIC to develop a new assay method for the separation and quantification of some phenothiazines (promethazine, chlorpromazine and perphenazine) in human urine and synthetic pharmaceutical formulations. Methods: The 32 full-factorial design was adopted to study the effect of mobile phase composition on separation efficiency, retention time, peak height and baseline. The separation was conducted on a C18 monolithic column (100 × 4.6 mm) using a mobile phase composition of phosphate: acetonitrile:methanol (60:28:12) at pH 4.0. The detection was carried out using a miniaturized fiber optic spectrometer at 250 nm. Results: Satisfactory analytical features, including number of theoretical plates (1809-6232), peak symmetry (1.0-1.3), recovery (95.5-99.1% in pharmaceutical formulations and 91.6-94.7% in urine), intra-day precision (0.36-1.60% for pharmaceutical formulation and 2.96-3.67 for urine), inter-day precision (1.47-2.28% for pharmaceutical formulation), limits of detection (0.23-0.88 μg/ml) and limits of quantification (0.77-2.90 μg/ml), were obtained. Conclusion: The remarkable advantages of the proposed SIC method are the inexpensiveness in terms of instrumentation and reagent consumption.

Flow-Batch Sample Preparation for Fractionation of the Stress Signaling Phytohormone Salicylic Acid in Fresh Leaves

Salicylic acid (SA) is an important stress signaling phytohormone and plays an essential role in physiological processes in plants. SA fractionation has been carried out batchwise, which is not compatible with the high analytical demand in agronomical studies and increases susceptibility to analytical errors. In this context, a novel flow-batch sample preparation system for SA fractionation on fresh plant leaves was developed. It was based on microwave-assisted extraction with water and conversion of the conjugated species to free SA by alkaline hydrolysis. Free and total SA were quantified by fluorimetry after separation by sequential injection chromatography in a C18 monolithic column. The proposed procedure is directly applicable to plant leaves containing up 16 mg kg−1 SA, with a limit of detection of 0.1 mg kg−1 of SA, coefficient of variation of 3.0% (n = 10), and sampling rate of 4 samples h−1. The flow-batch sample preparation system was successfully applied to SA fractionation in sugarcane, corn, and soybean leaves without clogging or increasing in backpressure. The proposed approach is simple, less time-consuming, and more environmentally friendly in comparison to batchwise procedures.