Ion suppression, reduced long-term robustness and leakage current of the spray voltage during the ionization of trichloroacetic acid; a case study with a methylmalonic acid assay

In-situ formation of deep eutectic supramolecule based extraction method coupled to valve switching ion chromatography mass spectrometry for the determination of aminoglycosides in meat

A novel extraction methodology was developed for extracting nine aminoglycosides (AGs) from meats based on the in-situ formation of deep eutectic supramolecule between analytes and gallic acid. Good chromatographic separation was achieved on a cation-exchange column utilizing solely a diluted organic acid as the eluent. A matrix-switching system was created to divert common inorganic cations from the column effluent to waste, reducing conductance peak values by 99.8 % and mitigating ion suppression in high-resolution electrospray ionization. The methodology was validated and exhibited excellent linearity across a concentration range of 20-800 μg L-1, with correlation coefficients (r) ranging from 0.9982 to 0.9997. The limits of detection and quantification were in the range of 7.1-13.8 μg kg-1 and 22.8-44.0 μg kg-1, respectively. The method was applied to the analysis of nine AGs in forty-five samples, attaining recovery values ranging from 89.1 % to 102.1 % with relative standard deviations of 1.9 %-6.4 %. The study provides a reliable procedure that complies with the requirements of the EU's official methods of analysis for identifying and quantifying the restricted and prohibited substances. The method simplifies operations and shortens extraction times by ingeniously integrating various techniques. It also eliminates the need for toxic reagents and streamlines operations compared to the conventional liquid chromatography. The results showed that IC-MS is a convenient and selective complementary approach to other modes of chromatography for determining multiple AGs in complex samples.

Protein Precipitation by Metal Hydroxides as a Convenient and Alternative Sample Preparation Procedure for Bioanalysis

Protein precipitation is widely used for sample preparation ahead of liquid chromatography. This step is required to analyze small molecules without the interference of proteins contained in the matrix. Organic solvents and acidic chemicals are the two most popular reagents used for this scope. Organic solvents are quite effective precipitating agents, but require a medium-to-large sample dilution. Moreover, a high concentration of organic solvents in sample media can affect reversed phase separations. Therefore, an evaporation step, followed by the resuspension of the analytes in appropriate media, is sometimes required. On the contrary, the addition of acidic compounds is more straightforward, since it keeps the supernatant aqueous and does not require evaporation, but the extreme pH can cause the degradation of analytes and the stationary phase. Herein, an alternative method for protein precipitation using the addition of zinc hydroxide was tested. The main advantages of this method over the other precipitating reagents are the minimal sample dilution required and the maintenance of aqueous media at nearly neutral pH which ensure analyte stability. The protocol ensured an effective protein removal before the analysis of small molecules in biological matrices, resulting in full compatibility with reversed phase chromatography coupled with both UV and mass spectrometric detectors.

A novel automated multi-cycle magnetic solid-phase extraction coupled to LC-MS/MS to study the disorders of six functional B vitamins in patients with gastroenterology and hyperhomocysteinemia

B vitamins are essential for human life and their disorders can cause a variety of diseases. Solid-phase extraction (SPE) coupled to LC-MS/MS is a preferred technique for determining multiple B vitamins, however, their complexity in real biological matrices makes it hard to achieve satisfactory recovery and accuracy when simultaneous detection. In this study, a novel automated multi-cycle magnetic SPE (MSPE) coupled to the LC-MS/MS method was established using a mixed-mode anion exchange magnetic adsorbent for the simultaneous extraction of six functional B vitamins, including methylmalonic acid, riboflavin, pantothenic acid, 4-pyridoxic acid, folic acid, and 5-methyltetrahydrofolate. After three consecutive MSPE cycles, the recoveries of all analytes were between 51.5% and 89.6%. The method exhibited excellent sensitivity and linearity, with a dynamic range of 200-fold (R > 0.99 for all analytes), exceptional accuracy (ranging between 95.4% and 105.6%) and precision (with RSDs ≤ 6.2%) without significant matrix effects or interferences. Compared to manual SPE method, the automated multi-cycle MSPE method has better feasibility and greater vitamin coverage. It shows a high correlation with the manual method for the detection of 5-methyltetrahydrofolate and folate (R > 0.99). A study of patients from the gastroenterology department showed that those undergoing surgery and those with malignancies may be at risk of folate deficiency. In addition, patients with hyperhomocystinemia had higher levels of methylmalonic acid and lower levels of 5-methyltetrahydrofolate, which correlated with homocysteine levels (R = 0.404 and -0.311, respectively) and showed dose-response relationships. This method is highly automated and cost-effective, with minimal systematic error, making it suitable for the analysis of clinical samples.

5-Fluorouracil and Anti-EGFR antibody scaffold chitosan-stabilized Pickering emulsion: Formulations, physical characterization, in-vitro studies in NCL-H226 cells, and in-vivo investigations in Wistar rats for the augmented therapeutic effects against squamous cell carcinoma

This research seeks to optimize a chitosan-stabilized Pickering emulsion (PE) containing 5-fluorouracil (5-FU) as a potential Squamous Cell Carcinoma therapy. The 5-Fluorouracil was also thoroughly analysed using UV spectrophotometry and RP-HPLC, demonstrating exceptional linearity, sensitivity, precision, and robustness. The techniques of characterization revealed Pickering emulsion (PE) morphology, solid-like gel properties, successful encapsulation, and promising anticancer effects. FTIR was used to validate the efficacy of encapsulation, and DSC was used to confirm the post-encapsulation drug stability. The 0.6 % chitosan-stabilized PE showed exceptional stability and drug loading efficiency. Anti-EGFR-5-FU-CS-PE gel was developed for sustained drug release in the treatment of Squamous Cell Carcinoma. Anti-EGFR-5-FU-CS-PE demonstrated potent anticancer effects in vitro, with a lower IC50 than 5-FU and 5-FU-CS-PE. Anti-EGFR-5-FU-PE Pickering emulsions based on chitosan were investigated for their rheological properties, cellular interactions, and therapeutic potential. Both emulsions and gel exhibited sustained in vitro drug release after successful encapsulation. Anti-EGFR-5-FU-CS-PE induced apoptosis, decreased mitochondrial membrane potential, and inhibited the migration of cancer cells. Wistar mice were tested for safety and tumour growth inhibition. All formulations exhibited exceptional six-month stability. Anti-EGFR-5-FU-CS-PE emerges as a viable therapeutic option, necessitating additional research.