Analytical Methods最新文献

Potassium (K) is among the macronutrients required for crop production and it is absorbed through plant roots from the soil solution. Replenishment of soil K is usually done by fertilizer application; therefore, it is crucial to know the amount of this nutrient that's available in the soil. There's very little literature reporting a turbidimetric method for K determination, and even less in soil samples. The objective of this work is to evaluate a portable low-cost system that allows turbidimetric determination to assess the amount of available K in soil. The turbidimetric method consists of K precipitation with sodium tetraphenylborate (NaTPB). The time and Mehlich-1, Mehlich-1 diluted 1 : 1 and water solutions for the extraction procedure were evaluated. The effect of pH, along with NaTPB volume and sensor signal stability, was also evaluated. With the optimized conditions, calibration of the sensor showed a good linearity (r² = 0.9982), and the limits of detection and quantification were 0.1 and 0.3 mg L^-1 of K, respectively. No significant difference (t test with 95% confidence level) is observed between the results obtained with the sensor and the MP-AES and ICP OES determinations using Mehlich-1 solution for K extraction. The results presented here demonstrate that it is possible to use simple equipment to measure available K in soil on the field by using low amounts of reagents, which could make this analysis more accessible.

We have developed a novel fluorescence sensor based on upconversion nanoparticles (UCNPs) for the rapid and sensitive detection of trace aluminum ions (Al³⁺). The sensor utilizes the inner filter effect (IFE) between the UCNPs and the xylenol orange-aluminum complex (XO-Al³⁺), resulting in significant fluorescence quenching at 543 nm upon Al³⁺ binding. This quenching correlates directly with the Al³⁺ concentration, allowing for quantitative detection within a range of 0-30 μM and achieving an ultra-low detection limit of 0.19 μM. Selectivity of the sensor is enhanced by the incorporation of ascorbic acid, which masks interfering Fe³⁺ ions, thus ensuring accurate determination of Al³⁺ even in the presence of other metal ions. The UCNPs-XO sensor exhibits excellent stability and reproducibility, and minimal interference from commonly co-existing substances. This makes it suitable for the detection of Al³⁺ in various matrices, including food products and environmental water samples. Our work offers a significant advancement in Al³⁺ detection, with potential applications in food safety, environmental monitoring, and public health.

Microplastics raise growing concerns regarding their ubiquity and possible negative impact on human health; therefore, the need for comparable, standardized methods is urgent. Modern instrumental analytical techniques, such as IR and Raman spectroscopy, pyrolysis-gas chromatography-mass spectrometry and electron microscopy, are fundamental for the analysis of microplastics in environmental and biological objects. The quality of the samples prepared is a determining factor in the validity of the results obtained. Based on our research, currently approaches to preparing environmental samples are time-consuming and need some improvements. To overcome this problem, a new method for the preparation of freshwater samples was developed. In our research, peracetic acid and its combination with Fenton's reagent were employed for the first time to prepare natural water samples. Furthermore, we proposed the use of a heavy liquid based on sodium heteropolyoxotungstate with a density of 1.70 g cm^-3, which allows the extraction of polymers with high density and is non-toxic. The new approach was compared with the most commonly used sample preparation method (peroxide oxidation (30% H₂O₂ + 0.05 M Fe(II) solution)) and showed higher recovery efficiency for microplastic particles in both test and freshwater samples collected from the rivers Ob (Novosibirsk, Russia) and Berd (Berdsk, Russia). The obtained results are promising; the time spent on this procedure is no more than 3 hours, which is 6 to 12 times faster than the most widely used methods. In addition, this approach makes it possible to obtain samples suitable for subsequent analysis by any analytical instrumental method.

Glycosphingolipids are glycolipid complexes formed by an oligosaccharide chain covalently linked to a ceramide backbone and play important roles in the occurrence and metastasis of lung cancer. In this study, an UHPLC-HRMS method was developed for the comprehensive profiling of glycosphingolipids, with an in-house library constructed for data interpretation. Serum glycosphingolipids were profiled in 31 healthy controls (HCs) and 92 lung cancer patients with different pathologic subtypes. Over 1700 glycosphingolipids were detected in human serum based on the novel method. A total of 567 differential glycosphingolipids (adjusted P < 0.05, and fold change > 2) were found between lung cancer patients and HCs. Glycosphingolipids can be used as potential biomarkers for lung cancer diagnosis, with sensitivity much higher than that of traditional serum tumor markers. The levels of most glycosphingolipids in squamous cell carcinoma (Squa) were significantly lower than those in small cell lung cancer (SCLC) and adenocarcinoma (Aden). The highest Cer1P abundance in SCLC patients among the three different subtypes of lung cancer was thought to be related to the high malignancy and metastasis of SCLC. An artificial neural network (ANN) model was constructed for the discrimination of the three different subtypes of lung cancer, with accuracy higher than 93%. Beyond providing biomarkers and statistical models for the diagnosis of lung cancer and discrimination of lung cancer subtypes, this study uncovered the variation of glycosphingolipid networks in different subtypes of lung cancer and thereby provided a novel insight to study the pathogenesis of lung cancer and explore therapeutic targets.

N-Nitrosamines, carcinogenic compounds present in dietary and environmental sources and formed endogenously, are believed to be linked with the presence of nitrate and nitrite, both within dietary sources and after intake. To fully evaluate this potential threat to human health, an accurate analytical method to measure N-nitrosamines in biological matrices is necessary. We report a simple, fast, selective mass spectrometry method to detect N-nitrosamines in human urine. Analysis of seven N-nitrosamines, N-nitrosodimethylamine (NDMA), N-nitrosomethylethylamine (NMEA), N-nitrosodiethylamine (NDEA), N-nitrosopiperdine (NPIP), N-nitrosopyrrolidine (NPYR), N-nitrosodi-N-propylamine (NDPA) and N-nitrosodi-N-butylamine (NDBA) in urine was quantitated using Ultra High-Pressure Liquid Chromatography-tandem Mass spectrometry (UHPLC-MS/MS). A Sorbent supported Liquid Extraction (SLE) method was employed to extract N-nitrosamines from 24 hour collected human urine samples. The percent recovery varied between 74.3 to 110 and the limit of detection and limit of quantification ranged from 0.1 to 0.85 ng mL^-1 and 0.22 to 2.06 ng mL^-1 respectively. Precision for inter-day and intra-day assay yielded a % coefficient of variation between 4-10% for all measured compounds in urine. Linear regression analysis of calibration curves for N-nitrosamines measured in urine in the concentration range 0.4-12.8 ng mL^-1 gave correlation coefficients, R² 0.9874-0.9962. Urinary excretion of N-nitrosamines measured in ten healthy subjects resulted in detection of most of the N-nitrosamines including NDMA, NDEA, NPYR, NDPA and NDBA by this method.

A new fluorescent ratiometric switch (BOHB) was developed for swift and selective detection of cyanide ions in aqueous media without any interference from other competitive anions. Upon gradual addition of cyanide ions into the probe solution, a prominent fluorescence color change from yellow to cyan was observed under a UV chamber. The fluorescence changes thus observed were ratiometric, and the detection limit of this new probe was found to be (22.1 ± 0.89) μM, suggesting that the efficiency of BOHB for the detection of cyanide ions is brilliant even at a minute level. The blue shift in fluorescence intensity upon the addition of cyanide ions was attributed to the deprotonation mechanism of acidic protons present in BOHB. This phenomenon was further explored using ¹H-NMR study, which supported the mechanism. Further, stability study was performed over a period of 5 days to prominently establish the stability of BOHB. The probe is also highly capable of recognizing CN^- within a very short time-span (almost 15 seconds), thereby making it a brilliant fluorescent switch for the swift recognition of CN^-. Furthermore, BOHB was employed for real water sample analysis to display its practical application. Besides, the easy-to-prepare dipstick experiment provides a simple, reusable and recyclable protocol for the suitable qualitative identification of CN^-. Lastly, triple negative breast adenocarcinoma (MDA-MB-231) cells were made susceptible to CN^- sensing in a biological system, thereby making BOHB a biomarker tool.

The evaluation of measurement uncertainty involves combining available experimental data with additional knowledge on the impact of sources of uncertainty on the measured value to quantify combined uncertainty. This uncertainty should express the impact of relevant random and systematic effects on the measured value to allow an objective interpretation of the performed quantification. This research discusses how to assess and account for the impact on measurement uncertainty evaluation of uncontrolled high temperature of sample preparation and of supporting experimental validation data on a single calibration of the instrumental method of analysis used. After the detailed inspection of the measurand and measurement process, the various uncertainty components were quantified from experimental data and/or additional information. This research illustrates that experimental limitations can be overcome by a detailed and quantitative understanding of the measurement process. Melatonin content in tea was quantified between 3.7 g kg^-1 and 196 g kg^-1 with a relative expanded uncertainty between 28% and 40%, lower than the target or maximum admissible relative expanded uncertainty of 40%. The use of HPLC-FD calibration several days before sample analysis is the major uncertainty component responsible for up to 82.7% of the measurement uncertainty.

Perfluorooctane sulfonate (PFOS), a ubiquitous persistent organic pollutant, has aroused growing concern due to its adverse effects on human health. Timely onsite monitoring of PFOS in heavily contaminated areas is crucial for effective pollution management and prevention of its spread. However, relevant PFOS detection methods have rarely been reported. Herein, we developed a fluorescence sensing system capable of achieving timely onsite detection of PFOS under outdoor conditions. First, aggregate induced emission (AIE) fluorescence sensors, TPE-PAs, were synthesized. The optimized sensor could selectively interact with PFOS through electrostatic attraction and hydrogen bonding and exhibited prominent fluorescence enhancement after treating with PFOS. There was a good linear relationship between the fluorescence enhancement and PFOS concentration in the range of 0.05-30 ppm, and the limit of detection was measured to be 0.047 ppm. In addition, owing to the AIE fluorescence mechanism and high concentration of TPE-PAs in the sensing medium, the sensor demonstrated excellent anti-interference performance. Second, we developed a portable fluorometer, by modifying the power supply and sample cell of a tiny fluorometer, and further integrated this modified fluorometer, the prepared fluorescence sensor, standard PFOS solutions and other consumables into a portable test system. This test system showed good detection accuracy and reliability and successfully achieved timely onsite PFOS detection in real water samples.

Mn-doped Ti-based MOFs (MnTi MOFs) were synthesized by a solvothermal method, and calcined at high temperature after being mixed with pre-prepared PPy nanotubes to give MnO/TiO₂/C/N-CNTs composites. The composites were studied by SEM, XRD, XPS and FTIR. Based on these composites, a new electrochemical sensor was prepared, which has good electrocatalytic ability for the redox of catechol (CC) and hydroquinone (HQ), and can detect CC and HQ simultaneously. The results showed that the oxidation peak current of CC and HQ increased linearly in the concentration range of 0.50-120.00 μM. The detection limits were 0.033 μM and 0.019 μM, respectively. The constructed sensor has been successfully used for the simultaneous detection of CC and HQ in lake water and tap water, and has a good recovery rate.

Collective endothelial migration is a hallmark of wound healing, which is regulated by spatial concentration gradients of extracellular biochemical factors. Arginine-glycine-aspartate (RGD) peptides play a vital role in regulating cell migration through specific binding to integrins. In this study, a micro-fluidic technology combined with a photopolymerization technique is developed to create gelatin methacryloyl (GelMA)-based substrates with various concentration gradients of RGD peptides. The capability of generating linear and nonlinear RGD concentration gradients was quantitatively verified through numerical simulation and immunohistochemical quantitative experiments. The results of the concentration gradients show a strong concurrence between the immunohistochemical quantification experiments and numerical simulations. Furthermore, endothelial migration experiments were conducted with various concentration gradients of RGD peptides. We have observed that endothelial cells on the surface of gels with a linear concentration gradient exhibit a larger cell area, a longer cell perimeter, and more stress fiber density. Furthermore, the cells demonstrate directional alignment and migration towards regions with a higher RGD concentration. High concentration gradients significantly enhance endothelial cell migration, consistent with observations on surfaces of gels with nonlinear concentration gradients. In brief, we proposed a simple and effective micro-fluidic photopolymerization technique capable of generating diverse concentration gradients of RGD and probing their effects on cell migration. The results suggest that regulating the RGD peptide concentration gradients can alter the migration of endothelial cells, showing potential for promoting wound healing.