Multiple responses optimization in the development of a headspace gas chromatography method for the determination of residual solvents in pharmaceuticals

An efficient generic static headspace gas chromatography (HSGC) method was developed, optimized and validated for the routine determination of several residual solvents (RS) in drug substance, using a strategy with two sets of calibration. Dimethylsulfoxide (DMSO) was selected as the sample diluent and internal standards were used to minimize signal variations due to the preparative step. A gas chromatograph from Agilent Model 6890 equipped with flame ionization detector (FID) and a DB-624 (30 m×0.53 mm i.d., 3.00 µm film thickness) column was used. The inlet split ratio was 5:1. The influencing factors in the chromatographic separation of the analytes were determined through a fractional factorial experimental design. Significant variables: the initial temperature (IT), the final temperature (FT) of the oven and the carrier gas flow rate (F) were optimized using a central composite design. Response transformation and desirability function were applied to find out the optimal combination of the chromatographic variables to achieve an adequate resolution of the analytes and short analysis time. These conditions were 30 °C for IT, 158 °C for FT and 1.90 mL/min for F. The method was proven to be accurate, linear in a wide range and very sensitive for the analyzed solvents through a comprehensive validation according to the ICH guidelines. Keywords: Headspace gas chromatography, Residual solvents, Pharmaceuticals, Surface response methodology, Desirability functio

A novel and sustainable pipette-tip solid-phase microextraction testing of six carbon-based nanomaterials as proof of concept for the determination of sixteen emerging pollutants from active veterinary principles

A new and optimized solid-phase microextraction method using pipette tips is proposed as a proof of concept for the extraction of sixteen veterinary drugs: antimicrobials (trimethoprim, enrofloxacin and sulfamethoxazole), external antiparasitics (thiamethoxam, clothianidin, imidacloprid, fipronil, clorpyrifos, lufenuron, and permethrin), internal antiparasitics (fenbendazole and albendazole), anti-inflammatories (prednisolone, diclofenac, and betamethasone), and an anticoccidial (robenidine). In this context, the device has been challenged by many analytes with very different structural and physicochemical properties, which presents a major difficulty in the simultaneous extraction of different APs. To this end, six carbon-based nanomaterials (multi-walled carbon nanotubes (MWCNTs), graphite, graphene oxide (GO), electrochemically expanded graphene (GEQE), electrochemically reduced graphene (ERGO), and commercial and synthetic graphene oxide) were evaluated packing sorbent in the extraction column. Several NMs (GEQE and ERGO) were used for the first time as sorbents in microextractions and were fabricated, synthesized, and characterized in the laboratory. Simple materials available in any laboratory were used to fabricate the devices, showing the simplicity, ease of preparation, and low cost of the proposed device. Optimization of the microextraction device (pipette tip) was performed using chemometric tools (design of experiments and reaction surface methodology) to obtain the sorbent mass and pH to improve retention rates. In addition, a comparative analysis of the extraction of single and multi-analytes and of a batch and a continuous system was performed. Real samples were examined to evaluate the proper performance of the instrument, which can be used in a preanalytical phase of sample handling to isolate analytes from complex samples. Furthermore, a very detailed and comparative study of the physicochemical properties of NM compared to the analytes was performed, providing valuable information on the interactions taking place and the experimental conditions required, which can be extrapolated to many analyses with similar properties. Additionally, the AGREE software was used to determine the environmental friendliness of the extraction methods and to compare them with the literature. Based on the latter considerations, this multi-analyte microextraction method holds great promise for future applications in the determination of novel environmental contaminants in water systems