Comprehensive Assessment of Flow and Other Analytical Methods Dedicated to the Determination of Zinc in Water

Development and Validation of a UHPLC-MS/MS Method for the Quantification of a Novel PYGB Inhibitor in Plasma: Application to Pharmacokinetic Studies

In previous studies, we reported compound 1 (5-chloro-N-(4-oxo-2,2-dipropyl-3,4-dihydro-2H-benzo[e][1,3]oxazin-6-yl)-1H-indole-2-carboxamide) as a novel PYGB inhibitor, and found that it had better anti-ischemic brain injury activity. In this study, we established and validated a novel UHPLC-MS/MS method for the quantitative determination of compound 1 in plasma, then applied the method to study the pharmacokinetic parameters and brain tissue distribution of compound 1 in SD (Sprague-Dawley) rats after intravenous administration. The experimental results showed that the method met the validation requirements set by the US FDA in terms of linearity, accuracy, precision, and stability. The validated method was then used for pharmacokinetic studies in rat plasma, and it was found that compound 1 exhibited linear pharmacokinetic characteristics when administered in the dose range of 0.8-3.2 mg/kg. Finally, we also conducted a brief preliminary investigation of the brain tissue distribution of compound 1 in rats after injection and found that the brain tissue concentrations at 0.25 h and 2 h of administration were 440 ± 19.1 ng/kg and 111 ± 23.9 ng/kg, respectively. Additionally, the CBrain/CPlasma ratio was 0.112 ± 0.0185 and 0.112 ± 0.0292, respectively. These results indicated that compound 1 was able to cross the blood-brain barrier. This study provides important support for the application of compound 1 in ischemic brain injury diseases.

Determination of dissolved nickel in natural waters using a rapid microplate fluorescence assay method

A new microplate analytical procedure is described for the determination of nickel (Ni²⁺) ions in natural water samples. A lophine analogue fluorescent sensor was synthesized and a spectral study showed a selective fluorescence quenching effect of chemical sensor by Ni²⁺ under optimized conditions. Density functional theory (DFT) calculations confirmed the formation of a Ni(II)L₃ complex obtained by the Job plot. The calculations showed that the fluorescence emission peak of L collapses due to the distortion of L in the complex. The simple and fast microplate procedure allowed us to quantify Ni²⁺ with a linear response from 1.6 to 40 µg L^-1 and a quantification limit of 5.4 µg L^-1 without the need of a preconcentration step. The optimized procedure using high-throughput microplate assay has been applied for the determination of Ni²⁺ in natural water samples with good analytical performances.

A Perspective of the Comprehensive and Objective Assessment of Analytical Methods Including the Greenness and Functionality Criteria: Application to the Determination of Zinc in Aqueous Samples

The recently proposed concept of White Analytical Chemistry (WAC), referring to the Red-Green-Blue color model, combines ecological aspects (green) with functionality (red and blue criteria), presenting the complete method as “white”. However, it is not easy to carry out an overall quantitative evaluation of the analytical method in line with the WAC idea in an objective manner. This paper outlines the perspective of the future development of such a possibility by attempting to answer selected questions about the evaluation process. Based on the study consisting in the evaluation of selected model methods by a group of 12 independent analysts, it was shown how well individual criteria are assessed, whether the variability of assessments by different people is comparable for each criterion, how large it is, and whether averaging the scores from different researchers can help to choose the best method more objectively.