Determination of inorganic ions and carbohydrates in cardioplegia and nephroplegia solutions by ion chromatography.

In this study, methods for analyzing inorganic ions and carbohydrates in cardioplegia and nephroplegia solutions were developed and validated using ion chromatography with both conductivity and pulsed amperometric detection. The inorganic ions such as sodium, potassium, and calcium were separated by a cation-exchange column with 27 mM methanesulfonic acid as mobile phase at 0.5 mL/min. The anion (chloride) and carbohydrates (mannitol and glucose) were analyzed by an anion-exchange column using a mobile phase of 20 mM sodium hydroxide at 1.0 mL/min. The methods showed a high sensitivity for all analytes, with quantification limits from 0.0002 to 0.06 mg/L. Good linearities between the peak areas and concentrations were found for all analytes within the selected concentration range (R2  > 0.999). Relative standard deviation values for repeatability and interday precision were 0.1%-1.0% and 0.7%-1.6%, respectively. The accuracy was validated by determining the percentage recovery, which was between 98.0% and 101.3% for all analytes, indicating good accuracy of the methods. The robustness was verified by using an experimental design. Finally, real samples were analyzed to determine the content of the analytes. All assay values were between 96.8% and 102.5%.

Quantification of amino acids secreted by yeast cells by hydrophilic interaction liquid chromatography-tandem mass spectrometry.

Monitoring the levels of amino acids (AAs) in biological cell cultures provides key information to understand the regulation of cell growth and metabolism. Saccharomyces cerevisiae can naturally excrete AAs, making accurate detection and determination of amino acid levels within the cultivation medium pivotal for gaining insights into this still poorly known process. Given that most AAs lack ultraviolet (UV) chromophores or fluorophores necessary for UV and fluorescence detection, derivatization is commonly utilized to enhance amino acid detectability via UV absorption. Unfortunately, this can lead to drawbacks such as derivative instability, labor intensiveness, and poor reproducibility. Hence, this study aimed to develop an accurate and stable hydrophilic interaction liquid chromatography-tandem mass spectrometry analytical method for the separation of all 20 AAs within a short 17-min run time. The method provides satisfactory linearity and sensitivity for all analytes. The method has been validated for intra- and inter-day precision, accuracy, recovery, matrix effect, and stability. It has been successfully applied to quantify 20 AAs in samples of yeast cultivation medium. This endeavor seeks to enhance our comprehension of amino acid profiles in the context of cell growth and metabolism within yeast cultivation media.

Development and Validation of Liquid Chromatographic Method for Fast Determination of Lincomycin, Polymyxin and Vancomycin in Preservation Solution for Transplants.

In this study, a liquid chromatographic method was developed for the fast determination of lincomycin, polymyxin and vancomycin in a preservation solution for transplants. A Kinetex EVO C18 (150 × 4.6 mm, 2.6 µm) column was utilized at 45 °C. Gradient elution was applied using a mixture of mobile phases A and B, both including 30 mM phosphate buffer at pH 2.0 and acetonitrile, at a ratio of 95:5 (v/v) for A and 50:50 (v/v) for B. A flow rate of 1.0 mL/min, an injection volume of 20 µL and UV detection at 210 nm were used. A degradation study treating the three antibiotics with 0.5 M hydrochloric acid, 0.5 M sodium hydroxide and 3% H2O2 indicated that the developed method was selective toward lincomycin, polymyxin, vancomycin and their degradation products. Other ingredients of the preservation solution, like those from the cell culture medium, did not interfere. The method was validated with good sensitivity, linearity, precision and accuracy. Furthermore, lincomycin, polymyxin and vancomycin were found to be stable in this preservation solution for 4 weeks when stored at -20 °C.

Overview of chromatographic and electrophoretic methods for the determination of branched-chain amino acids.

The significance of branched-chain amino acids in diseases was clearly shown over the years. This review aims to describe the available techniques for their analytical determination. The article provides examples of the use of various analytical methods. The methods are divided into two categories: derivatization and non-derivatization approaches. Separation is achieved through different chromatography or capillary electrophoresis techniques and can be combined with different detectors such as flame ionization, ultraviolet, fluorescence, and mass spectrometry. It compares the application of various derivatization reagents or detection as such for different detectors.

Overview of in-capillary enzymatic reactions using capillary electrophoresis.

This review summarizes the research that has recently been performed on in-capillary enzymatic reactions integrated with capillary electrophoresis. The manuscript is subdivided in homogeneous and heterogeneous approaches. The main homogeneous techniques are Electrophoretically Mediated Microanalysis, At-inlet and Transverse Diffusion of Laminar Flow Profiles. The main heterogeneous ones are Immobilized MicroEnzyme Reactors with enzymes grafted on either non-magnetic or magnetic particles. The overview covers the period from 2018 to early 2021. The applications range from drug discovery over natural products to food, beverage and pesticide analysis.

Quantification of allantoin and other metabolites of the purine degradation pathway in human plasma samples using a newly developed HILIC-LC-MS/MS method.

The development of a simple HILIC-LC-MS/MS method to quantify the plasma levels of allantoin, inosine, hypoxanthine, and adenosine, using stripped plasma for the bioanalytical method validation, was the purpose of this study. Chromatographic separation conducted using an XBridge BEH Amide column (2.1 × 150 mm, 3.5 µm) was achieved under gradient elution with two mobile phases: 0.1% formic acid-ACN (5:95) and 0.1% formic acid-ACN (50:50). Multiple reaction monitoring MS detection was performed using a triple quadrupole. The method validation experiments were performed according to the European Medicines Agency and the U.S. Food and Drug Administration guidelines. The lower LOQ was 50 nM, 5 nM, 20 nM, and 2 nM for allantoin, inosine, hypoxanthine, and adenosine, respectively. The recovery was repeatable and stable. The intraday precision ranged from 1.6% to 6.5%, while the interday precision ranged from 3.4% to 58.7%. Therefore, it is necessary to make a matrix-matched calibration curve each day to overcome this issue. Since the quality control samples' stability did not always comply with the guidelines, the samples need to be analyzed soon after collection.

Liquid chromatographic method to follow-up ceftazidime and pyridine in portable elastomeric infusion pumps over 24 h.

Portable infusion pumps are an interesting solution to continue outpatient parenteral antimicrobial therapy (OPAT) at the patient's home. However, the use of ceftazidime for such applications is challenging in view of its relatively poor stability in solution. In this study, elastomeric infusion pumps with 6 or 7 g of ceftazidime were deflated over 24 h in an oven at 33°C while ceftazidime and its degradation product, pyridine, were regularly monitored. Hereto, a fast and sensitive liquid chromatographic (LC) method has been developed using a Kinetex® C18 (150 × 3 mm, 2.6 µm) column with gradient elution. Ammonium formate 20 mM and acetonitrile (ACN) were mixed in a ratio of 98:2 v/v for mobile phase A and 85:15 v/v for mobile phase B. Both were adjusted to pH 4.5 with formic acid. The flow rate was set at 0.4 mL/min. The solution with a starting dose of 6 g ceftazidime was found to be degraded 10% after an average of 19 h 11 min so that an administration of 6 g to the patient was not reached. For the solution with a starting dose of 7 g of ceftazidime, 10% degradation was observed after an average of 18 h 42 min. However, by starting from a higher dose, an average of 6.56 g of ceftazidime could be administered over 24 h. In addition, 1.0% of pyridine versus ceftazidime pentahydrate with sodium carbonate (=mixture for injection) was formed over 24 h.

Diastereomer recognition of three pairs of tetracyclines by electrospray ionization mass spectrometry.

RATIONALE: Stereoisomer profiling is always a difficult issue. Based on the difference between diastereomers, usually because of steric hindrance, isomers can be differentiated by mass spectrometry (MS), although it is often not an easy task. In the current study, tetracycline, chlortetracycline and doxycycline could be distinguished from their respective 4-epimers by MS. METHODS: The electrospray ionization tandem mass spectrometry (ESI-MSn ) analyses were carried out on a Bruker 3000plus ion trap mass spectrometer. For MS/MS experiments, the collision energy was set between 0.18 and 0.45 V to perform energy-resolved mass spectrometry (ERMS). Test solutions were prepared in methanol/water (90:10, v/v) at a concentration of 10 µg/mL. RESULTS: Compared with the collision-induced dissociation (CID) spectrum of protonated tetracycline, the most abundant peak changed from m/z 427 to m/z 410 for 4-epitetracycline. For chlortetracycline and its 4-epimer, differences in relative abundance were observed too. In the CID spectrum of a fragment ion of doxycycline, the abundance of m/z 154 was relatively higher than for the 4-epimer, showing the same trend as in the CID spectra of the other two pairs of tetracyclines. CONCLUSIONS: The CID spectra of tetracycline and chlortetracycline were different from those of their 4-epimers. The CID spectra of protonated doxycycline and its 4-epimer showed only a subtle difference, but the m/z 154 fragment ion in the CID spectra of the fragment ion at m/z 428 offers the possibility to differentiate both epimers.

Determination of Inorganic Ions in Parenteral Nutrition Solutions by Ion Chromatography.

A new, simple and sensitive ion chromatography (IC) method for the determination of sodium, potassium, magnesium, calcium and chloride in a parenteral nutrition (PN) solution was developed and validated. Before sample analysis, a sample pretreatment by calcination was applied which could totally remove interference from other constituents of the PN solution. Methanesulfonic acid (MSA) and sodium hydroxide were used as the mobile phase for the determination of cations and anions, respectively. The calibration curves showed good correlation between analyte peak area and concentration (r2 > 0.999). Detection limits ranged from 0.0001 to 0.02 mg/L and quantification limits from 0.0002 to 0.06 mg/L. Relative standard deviation (RSD) values for repeatability and inter-day precision did not exceed 1.0% and the recoveries for all analytes were between 99.1−101.1%. The robustness was verified by using an experimental design.

Evaluation of aloins, pH and moisture in aloe leaf gel-based personal care products.

OBJECTIVE: Some easily applicable analytical methods were explored to evaluate the quality of personal care products containing aloe leaf gel. Aloins should be absent in these products in view of their side effects. To check this, liquid chromatography (LC) was applied. METHODS: The LC method used a C18 monolithic column combined with gradient elution and ultraviolet (UV) detection. The mobile phase consisted of a mixture of 0.1% formic acid in water (A) and 0.1% formic acid in acetonitrile (B). The method was validated with respect to specificity, linearity, precision and accuracy. Next, it was practically applied for the analysis of commercial samples. In addition, the pH and moisture content were determined. RESULTS: The LC results indicated that aloins were detected in 25% of the analysed commercial samples. Further, it turned out that 42% of the test samples were found to be in the basic pH range and 33% of them contained excessive moisture. CONCLUSION: Proper quality control and adequate labelling of aloe leaf gel-based cosmetics are mandatory to avoid side effects.

OBJECTIF: Certaines méthodes analytiques facilement applicables ont été explorée pour évaluer la qualité des produits de soins personnels contenants du gel de feuille d'aloe. Les aloïnes doivent être absentes de ces produits en raison de leurs effets secondaires. Pour vérifier cela, la chromatographie liquide (CL) a été appliquée. MÉTHODES: La méthode CL a utilisé une colonne monolithique C18 combinée à une élution par gradient et une détection ultraviolette (UV). La phase mobile était constituée d'un mélange de 0,1 % d'acide formique dans l'eau (A) et de 0,1 % d'acide formique dans l'acétonitrile (B). La méthode a été validée en ce qui concerne la spécificité, la linéarité, la précision et l'exactitude. Ensuite, elle a été appliquée pour l'analyse d'échantillons commerciaux. De plus, le pH et la teneur en humidité ont été déterminés. RÉSULTATS: Les résultats CL ont indiqué que des aloïnes ont été détectées dans 25 % des échantillons commerciaux analysés. Il s'est avéré que 42 % des échantillons se trouvaient dans la plage de pH basique et que 33 % d'entre eux contenaient une humidité excessive. CONCLUSION: Un contrôle de qualité approprié et un étiquetage adéquat des cosmétiques à base de gel de feuille d'aloe sont obligatoires pour éviter des effets secondaires.

Recent progress in the LC-MS/MS analysis of oxidative stress biomarkers.

The presence of a dynamic and balanced equilibrium between the production of reactive oxygen (ROS) and nitrogen (RNS) species and the in-house antioxidant defense mechanisms is characteristic for a healthy body. During oxidative stress (OS), this balance is switched to increased production of ROS and RNS, exceeding the capacity of physiological antioxidant systems. This can cause damage to biological molecules, leading to loss of function and even cell death. Nowadays, there is increasing scientific and clinical interest in OS and the associated parameters to measure the degree of OS in biofluids. An increasing number of reports using LC-MS/MS methods for the analysis of OS biomarkers can be found. Since bioanalysis is usually complicated by matrix effects, various types of cleanup procedures are used to effectively separate the biomarkers from the matrix. This is an essential part of the analysis to prepare a reproducible and homogenous solution suitable for injection onto the column. The present review gives a summary of the chromatographic methods used for the determination of OS biomarkers in both urine and plasma, serum, and whole blood samples. The first part mainly describes the biological background of the different OS biomarkers, while the second part reports examples of chromatographic methods for the analysis of different metabolites connected with OS in biofluids, covering a period from 2015 till early 2020. The selected examples mainly include LC-MS/MS methods for isoprostanes, oxidized proteins, oxidized lipoproteins, and DNA/RNA biomarkers. The last part explains the clinical relevance of this review.

Mechanodegradation of Polymers: A Limiting Factor of Mechanochemical Activation in the Production of Amorphous Solid Dispersions by Cryomilling.

In this study, we report on the influence of mechanochemical activation on the chemical stability of amorphous solid dispersions made up of indomethacin and hydroxypropyl methyl cellulose (HPMC), poly(vinylpyrrolidone) (PVP), poly(vinylpyrrolidone vinylacetate) (PVPVA), or Soluplus. In agreement with our recently published work, all applied carriers were found to be prone to polymer degradation. Covalent bonds within the polymers were cleaved and mechanoradicals were generated. Furthermore, decomposition of indomethacin was also observed but occurred only in the presence of polymers. Hence, it is proposed that the generated mechanoradicals from the polymers are responsible for the chemical degradation of indomethacin. Our study also strongly suggests the existence of a critical polymer- and process-dependent molecular weight limit "M∞", below which only limited mechanodegradation takes place since the lower-molecular-weight polymer PVP K12PF had a less profound influence on the degradation of indomethacin in comparison to PVP K25.

Aldehyde oxidase assay by capillary electrophoresis: From off-line, online up to immobilized enzyme reactor.

Capillary electrophoresis is a modern separation technique characterized by many benefits, which qualify it also for enzyme assays and the study of enzyme kinetics during drug development. Homogeneous or heterogeneous approaches can be followed for the enzymatic incubation. In this study, an immobilization procedure of aldehyde oxidase on magnetic particles was developed considering their integration with capillary electrophoresis. A number of magnetic nano/microparticle types were tested for this purpose, showing that aldehyde oxidase was most active when immobilized on bare silica magnetic nanoparticles. Primarily, the reusability of the enzyme immobilized on bare silica nanoparticles was tested. Three consecutive incubations with substrate could be performed, but the activity considerably dropped after the first incubation. One reason could be an enzyme detachment from the nanoparticles, but no release was detected neither at 4°C nor at 37°C during 5 h. The drop in enzymatic activity observed in consecutive incubations, could also be due to inactivation of the enzyme over time at given temperature. For the immobilized enzyme stored at 4°C, the activity decreased to 83% after 5 h, in contrast with a steep decrease at 37°C to 37%.

Study of aldehyde oxidase by micellar electrokinetic chromatography separation of O6 -benzylguanine and 8-oxo-O6 -benzylguanine.

A separation method for O6 -benzylguanine (O6 -BG) and 8-oxo-O6 -benzylguanine (8-oxo-O6 -BG) is developed by using MEKC. This study includes the optimization of separation and incubation parameters for both off-line and on-line procedures. The BGE consisted of 25 mM sodium phosphate buffer-methanol (70:30, v/v), apparent pH 7.4, in which SDS and methyl-ß-cyclodextrin were dissolved yielding final concentrations of 50 and 15 mM, respectively. Separations were performed at 15 kV using an untreated fused-silica capillary (40 cm length, effective length is 30 cm) with the detection wavelength at 195 nm. The capillary was kept at 15°C. Good performances were demonstrated for the repeatability and linearity. The LOQ was determined to be 14 µM for 8-oxo-O6 -BG (S/N = 10). The accuracy values showed a bias of +7.9% for 50 µM and -7.0% for 100 µM. Premix and transverse diffusion of laminar flow profiles (TDLFP) methods were used for on-line mixing and reaction of the substrate O6 -BG with aldehyde oxidase. Both procedures were successful in mixing as well as subsequent separation of the substrate and the metabolite, while the repeatability of TDLFP (14.7% (n = 3)) was much better than the premix technique.

Immobilizing sulfotransferase 1A1 on magnetic microparticles and their evaluation using capillary electrophoresis.

Sulfotransferases are categorized as phase II metabolic enzymes. Human sulfotransferase 1A1 (SULT1A1) is involved in the sulfonation of xenobiotics with aid from the cofactor 3'-phosphoadenosine-5'-phosphosulfate that acts as a sulfonate donor. In this study, we have attempted to immobilize SULT1A1 on magnetic microparticles (MMs). Different functionalized MMs were used to immobilize SULT1A1 and their enzyme activity was compared to the control (enzyme in solution). Paracetamol was used as model substrate. Separation of paracetamol and paracetamol sulfate by CE-UV was optimized and validated. MMs with epoxy based immobilization of SULT1A1 showed better enzyme activity. Hence, they were tested for repeated usage to allow their implementation for the development of a CE immobilized micro enzyme reactor.

Oxidative stress in autosomal dominant polycystic kidney disease: player and/or early predictor for disease progression?

Autosomal dominant polycystic kidney disease (ADPKD), caused by mutations in PKD1 or PKD2 genes, is the most common hereditary renal disease. Renal manifestations of ADPKD are gradual cyst development and kidney enlargement ultimately leading to end-stage renal disease. ADPKD also causes extrarenal manifestations, including endothelial dysfunction and hypertension. Both of these complications are linked with reduced nitric oxide levels related to excessive oxidative stress (OS). OS, defined as disturbances in the prooxidant/antioxidant balance, is harmful to cells due to the excessive generation of highly reactive oxygen and nitrogen free radicals. Next to endothelial dysfunction and hypertension, there is cumulative evidence that OS occurs in the early stages of ADPKD. In the current review, we aim to summarize the cardiovascular complications and the relevance of OS in ADPKD and, more specifically, in the early stages of the disease. First, we will briefly introduce the link between ADPKD and the early cardiovascular complications including hypertension. Secondly, we will describe the potential role of OS in the early stages of ADPKD and its possible importance beyond the chronic kidney disease (CKD) effect. Finally, we will discuss some pharmacological agents capable of reducing reactive oxygen species and OS, which might represent potential treatment targets for ADPKD.

Oxidative stress in chronic kidney disease.

Oxidative stress (OS), defined as disturbances in the pro-/antioxidant balance, is harmful to cells due to the excessive generation of highly reactive oxygen (ROS) and nitrogen (RNS) species. When the balance is not disturbed, OS has a role in physiological adaptations and signal transduction. However, an excessive amount of ROS and RNS results in the oxidation of biological molecules such as lipids, proteins, and DNA. Oxidative stress has been reported in kidney disease, due to both antioxidant depletions as well as increased ROS production. The kidney is a highly metabolic organ, rich in oxidation reactions in mitochondria, which makes it vulnerable to damage caused by OS, and several studies have shown that OS can accelerate kidney disease progression. Also, in patients at advanced stages of chronic kidney disease (CKD), increased OS is associated with complications such as hypertension, atherosclerosis, inflammation, and anemia. In this review, we aim to describe OS and its influence on CKD progression and its complications. We also discuss the potential role of various antioxidants and pharmacological agents, which may represent potential therapeutic targets to reduce OS in both pediatric and adult CKD patients.

Overview of sample introduction techniques prior to GC for the analysis of volatiles in solid materials.

Sample preparation and introduction techniques are very critical steps in gas chromatography analysis and particularly in the analysis of volatiles in solid samples. In these cases, they can be divided into two main categories: direct and indirect approaches, based on how the solid sample is treated, i.e. with and without dissolution (or extraction) of analytes from the solid sample. To enable routine application, coupling with sample preparation techniques (especially solid or solvent-based microextractions) is needed to achieve automation. Here, an overview of the most common sample introduction techniques for gas chromatography with their advantages and drawbacks is presented and discussed, including references to relevant examples. So, this review can serve as guidance for new users.

Exploration of the problems and solutions related to reference introduction prior to calibration of thermal desorber-gas chromatography.

Reference introduction in thermal desorption with gas chromatography is a critical aspect. It is mostly performed by offline liquid calibration using a micro syringe to inject a liquid standard solution on the sorbent in the thermal desorption tube. This is based on the assumptions that the adsorption-desorption process is quantitative and that no sample is lost in manipulating the tube. However, for analytical procedures involving thermal extraction of solid matrices, the adsorption-desorption processes for sample and reference differ and the assumptions are not always fulfilled. This is explored in this work. First, issues related to the online liquid calibration were investigated. With tubes containing only quartz filters, a relative loss of over 80% was noticed for some solvents due to tube manipulation processes. Enclosing a bed of mesoporous silica as sorbent limited the losses to about 25% when samples were immediately analysed, and even better results were obtained when tubes were stored for several hours so that proper adsorption could take place. An additional sweep gas during loading boosted the transfer of analytes with recoveries above 95%. Next, an inline injection system was installed on the thermal desorber instrument. This sorbent free, independent calibration tool avoids the drawbacks of other approaches.