Derivatization Conditions Research Articles

Determination of Free Glycidol and Total Free Monochloropropanediol in Fish and Krill Oil with Simple Aqueous Derivatization and High-Performance Liquid Chromatography-Tandem Mass Spectrometry.

This study introduces a novel method for detecting free glycidol and total free monochloropropanediol (MCPD) in fish and krill oil. Before analysis on high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS), p-(dimethylamino)phenol was used for derivatization of these compounds, enabling the sensitive determination of these contaminants. The sample preparation procedure includes a simple, efficient pretreatment using NaCl aqueous solution extraction and C18 sorbent cleanup (for demulsification), distinguishing glycidol from MCPD under varied reaction conditions for derivatization (weak acidic and strong alkaline aqueous environments). This approach shows broad linearity from 1 to at least 256 ng·mL-1, improved sensitivity compared to standard GC-MS methods, with the limit of detection (LOD) and limit of quantification (LOQ) for MCPD and glycidol in both oil samples verified at 0.5 ng·mL-1 and 1 ng·mL-1, respectively. Different from previous HPLC-MS methods for direct detection of glycidol esters or MCPD esters, this is the first HPLC-MS method used for the detection of free glycidol and total free MCPD in edible oil. Furthermore, this method can be potentially developed for glycidol or monochloropropane diol esters, which is similar to the current official methods adopted for indirect detection of these contaminants in different food matrices. Application of this detection method to real dietary supplements (fish oil and krill oil) revealed MCPD residues in fish oil (maximum detected: 32.78 ng·mL-1) and both MCPD (maximum detected: 2767.3 ng·mL-1) and glycidol (maximum detected: 22.2 ng·mL-1) in krill oil, emphasizing its effectiveness and accuracy for assessing contamination in these supplements.

Nitrogen stable isotope analysis of sulfonamides by derivatization-gas chromatography-isotope ratio mass spectrometry

The continuous introduction of micropollutants into the environment through livestock farming, agricultural practices, and wastewater treatment is a major concern. Among these pollutants are synthetic sulfonamide antibiotics such as sulfamethoxazole, which are not always fully degraded and pose a risk of fostering antimicrobial resistance. It is challenging to assess the degradation of sulfonamides with conventional concentration measurements. This study introduces compound-specific isotope analysis of nitrogen isotope ratios at natural abundances by derivatization-gas chromatography hyphenated with isotope ratio mass spectrometry (derivatization-GC-IRMS) as a new and more precise method for tracing the origin and degradation of sulfonamides. Here, sulfamethoxazole was used as a model compound to develop and optimize the derivatization conditions using (trimethylsilyl)diazomethane as a derivatization reagent. With the optimized conditions, accurate and reproducible δ15N analysis of sulfamethoxazole by derivatization-GC-IRMS was achieved in two different laboratories with a limit for precise isotope analysis of 3 nmol N on column, corresponding to 0.253 µg non-derivatized SMX. Application of the method to four further sulfonamides, sulfadiazine, sulfadimethoxine, sulfadimidine, and sulfathiazole, shows the versatility of the developed method. Its benefit was demonstrated in a first application, highlighting the possibility of distinguishing sulfamethoxazole from different suppliers and pharmaceutical products.Graphical

Cyanoacetohydrazide as a Novel Derivatization Agent for the Determination of UHPLC-HRMS Steroids in Urine.

The possibility of cyanoacetohydrazide usage as a novel derivatizing agent is demonstrated in the presented article, and a comparison with hydroxylamine as the most commonly used reagent is provided. Optimal conditions for steroid derivatization with cyanoacetohydrazide are provided. According to the collected data, the maximum yield of derivatives was observed at pH 2.8 within 70 min at 40 °C with 5 ng/mL limit of detection for all investigated analytes. It was shown that cyanoacetohydrazide derivatives produces both syn- and anti-forms as well as hydroxylamine, and their ratios were evaluated and shown in presented work. An efficiency enchantment from two to up to five times was achieved with a novel derivatization reagent. Its applicability for qualitative analysis of steroids in urine was presented at real samples. Additionally, the reproducible fragmentation of the derivatizing agent in collision-induced dissociation offers opportunities for simplified non-targeted steroidomic screening. Furthermore, cyanoacetohydrazide increases ionization efficiency in positive mode, which can eliminate the need for redundant high-resolution instrument runs required for both positive and negative mode analyses.

Chromatographic Methods for the Determination of Glyphosate in Cereals Together with a Discussion of Its Occurrence, Accumulation, Fate, Degradation, and Regulatory Status.

The European Union's recent decision to renew the authorization for the use of glyphosate until 15 December 2033 has stimulated scientific discussion all around the world regarding its toxicity or otherwise for humans. Glyphosate is a chemical of which millions of tons have been used in the last 50 years worldwide to dry out weeds in cultivated fields and greenhouses and on roadsides. Concern has been raised in many areas about its possible presence in the food chain and its consequent adverse effects on health. Both aspects that argue in favor of toxicity and those that instead may indicate limited toxicity of glyphosate are discussed here. The widespread debate that has been generated requires further investigations and field measurements to understand glyphosate's fate once dispersed in the environment and its concentration in the food chain. Hence, there is a need for validated analytical methods that are available to analysts in the field. In the present review, methods for the analytical determination of glyphosate and its main metabolite, AMPA, are discussed, with a specific focus on chromatographic techniques applied to cereal products. The experimental procedures are explained in detail, including the cleanup, derivatization, and instrumental conditions, to give the laboratories involved enough information to proceed with the implementation of this line of analysis. The prevalent chromatographic methods used are LC-MS/MS, GC-MS/SIM, and GC-MS/MS, but sufficient indications are also given to those laboratories that wish to use the better performing high-resolution MS or the simpler HPLC-FLD, HPLC-UV, GC-NPD, and GC-FPD techniques for screening purposes. The concentrations of glyphosate from the literature measured in wheat, corn, barley, rye, oats, soybean, and cereal-based foods are reported, together with its regulatory status in various parts of the world and its accumulation mechanism. As for its accumulation in cereals, the available data show that glyphosate tends to accumulate more in wholemeal flours than in refined ones, that its concentration in the product strictly depends on the treatment period (the closer it is to the time of harvesting, the higher the concentration), and that in cold climates, the herbicide tends to persist in the soil for a long time.

Optimization of hydrolysis conditions of alginate based on high performance liquid chromatography

Alginate is the most abundant polysaccharide compound in brown algae, which is widely used in various fields. At present, the determination of the content of alginate is mostly carried out using sulfuric acid and trifluoroacetic acid hydrolysis followed by the determination of the content, but the results are not satisfactory, and there are problems such as low hydrolysis degree and low recovery rate. Therefore, in this study, based on the optimization of high performance liquid chromatographic conditions for pre-column derivatization of 1-phenyl-3-methyl-5-pyrazolone (PMP), the hydrolysis effects of sulfuric acid, trifluoroacetic acid (TFA), oxalic acid, and formic acid were compared and the hydrolysis conditions were optimized. The results showed that formic acid was the best hydrolyzing acid. The optimal hydrolysis conditions were 95 % formic acid at 110 °C for 10 h. The hydrolysis effect was stable, with high recovery and low destruction of monosaccharides, which made it possible to introduce formic acid into the subsequent polysaccharide hydrolysis. The pre-column derivatization high performance liquid chromatography method established in this study was accurate and reliable, and the hydrolysis acid with better effect was screened, which provided a theoretical basis for the subsequent determination of alginate content.

Novel fluorescent probes based on sulfur and nitrogen co-doped carbon dots for determination of three N-substituted phenothiazine derivatives in dosage forms

In the current work, sulfur and nitrogen co-doped carbon dots (S,N-CDs) as simple, sensitive, and selective turn-off fluorescent nanosensors were utilized for analysis of three phenothiazine derivatives, including acetophenazine (APZ), chlorpromazine (CPH), and promethazine (PZH). S,N-CDs were synthesized through a green one-pot microwave-assisted technique using widely available precursors (thiourea and ascorbic acid). HRTEM, EDX, FTIR spectroscopy, UV–Vis absorption spectroscopy, and fluorescence spectroscopy were used to characterize the as-synthesized CDs. When excited at 330 nm, the carbon dots produced a maximum emission peak at 410 nm. The cited drugs statically quenched the S,N-CDs fluorescence as revealed by the Stern-Volmer equation. The current method represents the first spectrofluorimetric approach for the determination of the studied drugs without the need for chemical derivatization or harsh reaction conditions. The importance of the proposed work is magnified as the cited drugs do not have any fluorescent properties. The fluorescence of the developed sensor exhibited a linear response to APZ, CPH, and PZH in the concentration ranges of 5.0–100.0, 10.0–100.0, and 10.0–200.0 μM with detection limits of 1.53, 1.66, and 2.47 μM, respectively. The developed fluorescent probes have the advantages of rapidity and selectivity for APZ, CPH, and PZH analysis in tablets with acceptable % recoveries of (98.06–101.66 %). Evaluation of the method's greenness was performed using the Complementary Green Analytical Procedure Index (ComplexGAPI) and Analytical GREEnness metric (AGREE) metrics, indicating that the method is environmentally friendly. Validation of the proposed method was performed according to ICHQ2 (R1) guidelines.

Rapid determination of biogenic amines in ossotide injections by microfluidic chip-mass spectrometry platform: Optimization of microfluidic chip derivatization using response surface methodology

The microfluidic-chip mass spectrometry (MS) platform was developed for the rapid and automatic determination of 10 biogenic amines (BAs) in ossotide injections. The microfluidic chip was primarily consisted of a square unit for derivatization and a solid phase extraction (SPE) unit. The derivatization unit could achieve automatic mixing and reaction between sample and derivatization reagents, after which the targets were purified and enriched in SPE unit, further improving the sensitivity. To select the optimal derivatization conditions, four major parameters affecting derivatization in the microfluidic chip were optimized using Box-Behnken response surface design. On-chip derivatization unit enabled the shortest derivatization time by thorough solution mixing. There is no additional pretreatment required for the entire process. The developed method achieved satisfactory limits of detection (0.045–0.855 ng/mL) and limits of quantitation (0.156–3.11 ng/mL). The recoveries of the method ranged from 75.0 % to 106 % when coupled in-line with MS. This pretreatment chip-MS platform was successfully applied to BAs detection in the commercially available ossotide injections, demonstrating the prospects of this technique as a potential method for the rapid determination. The results of BAs in ossotide injections provide a basis for the formulation of the limit standard in pharmaceutical preparations.

Comparative characteristics of different methods for electrophoretic determination of mono- and disaccarides using derivatization

The following variants of electrophoretic determination of sugars with prior derivatization are considered in the article: reductive amination using p-aminobenzoic acid ethyl ester (ABEE) and condensation with 1-phenyl-3-methyl-5-pyrazolone (PMP). Derivatization products were separated using capillary electrophoresis in both zone and micellar modes, and comparative estimate characteristics were obtained. The best efficiency (ca. 650 thousand theoretical plates), selectivity (2.1–2.4), and LOD (0.8–2.9 μg/mL) was observed for the separation of reductive amination products using micellar electrokinetic chromatography (MEKC). Optimization of derivatization conditions was performed for the reductive amination using the central composite experiment design. Additionally, LOD was lowered by the sample intracapillary concentration in sweeping mode, and sample enhancement factors (SEF) of 13–19 were achieved. A proof-of-concept possibility of the intracapillary reductive amination ensuring electrophoretic mobility of the derivatization reagent using detergent micelles as carrying agents was demonstrated. Both derivatization methods were applied for the analysis of baby food.

Development and Validation of Derivatization Method for Simultaneous Quantitation of Asteracantha longifolia (L.) Nees Phytoconstituents by Liquid Chromatography–Electrospray Ionization–Mass Spectrometry/Mass Spectrometry

ABSTRACT Background: Betulin, lupeol, stigmasterol, and β-sitosterol are the active phytoconstituents accountable for the practical application of Asteracantha longifolia (L.) Nees in ayurvedic treatments as antitumor, hypoglycemic, aphrodisiac, antibacterial, free radical scavenging, lipid peroxidation, and hepatoprotective agent. As an essential medicinal plant in modern and traditional medicine, regularly checking raw material’s quality attributes and quantifying the phytoconstituents is indispensable. Aim: The aim of this study was to optimize derivatization conditions of these four essential phytoconstituents with p-toluenesulfonyl isocyanate (PTSI) reagent and the development of a liquid chromatography–electrospray ionization (ESI)–mass spectrometry (MS)/MS method that aids in the simultaneous detection of these four phytoconstituents. Objective: Thus, derivatization enhances sensitivity for detection in the negative mode with an electron spray ionization source and tandem mass spectroscopy. Further, the sensitive and rapid analytical method for simultaneous quantitation of betulin, lupeol, stigmasterol, and β-sitosterol is subsequently validated in line with the guidelines by ICH and used to quantify the phytoconstituents in two over-the-counter herbal formulations and one plant extract isolated at laboratory scale under batch analysis. Materials and Methods: PTSI reagent of purity <98% procured from TCI and other chromatography reagents of MS grade were utilized in the optimization of an analytical method. Results: The developed LC-ESI-MS/MS-based method demonstrated specificity for the targeted phytoconstituents, with LOD and LOQ values of < 0.13 ng/mL and 0.4 ng/mL, respectively. Linearity was established with a correlation coefficient ≥ 0.998 over a concentration range of 0.2 ng/mL to 6 ng/mL. Precision, expressed as %RSD for peak response, was ≤ 5%. The method showed satisfactory recovery for betulin (98.5%-108.3%), lupeol (95.0%-109.3%), stigmasterol (101.9%-117.0%), and β-sitosterol (99.1%-116.2%). Conclusion: The reagent PTSI reacts rapidly and forms stable derivatives. The derivatization of active phytoconstituents betulin, lupeol, stigmasterol, and β-sitosterol has enhanced the detection sensitivity of the analytical method.

High-sensitivity profiling of dipeptides in sauce-flavor Baijiu Daqu by chemical derivatization and ultrahigh-performance liquid chromatography coupled with high-resolution mass spectrometry

Dipeptides in sauce-flavor Baijiu Daqu are protein degradation products during the fermentation of Daqu, which are believed to play a crucial role in the flavor and quality of Baijiu. Herein, we integrated dansyl chloride derivatization with ultrahigh-performance liquid chromatography coupled with high-resolution mass spectrometry (UHPLC-HRMS) for comprehensively profiling dipeptides in Daqu. The derivatization efficiency was higher than 99.1 % for all 17 dipeptide standards under the optimized derivatization conditions. In total, 118 dipeptides were detected in Daqu. The method was validated and the analytical characteristics including the linearity (spanned across 2–4 orders of magnitude), precision (1.2–19.9 %), limit of detection (varied from 1.1 to 53.4 pmol/mL) and the stability (3.6–15.8 %) are satisfactory. The usefulness of the method was examined by studying the distribution characteristics of dipeptides in Daqu under different production conditions. The present method provides an effective and robust strategy for comprehensively analyzing dipeptide compounds in complex biological samples.

Quantitative determination of chondroitin sulfate with various molecular weights in raw materials by pre-column derivatization with 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate

A simple and reliable HPLC method was developed for quantification of chondroitin sulfate (CS). The procedure is based on precolumn hydrolysis of CS to liberate galactosamine and subsequent derivatization with 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate. Hydrolysis and derivatization conditions were optimized. A linear correlation coefficient of 0.9999 was calculated within the range of 10–1500 μg/mL from the standard curve. The method produces good precision and good accuracy (100.75 % recovery). An advantage over other common methods is its ability to quantify CS of all molecular weights and structures, as evidenced by the determination of CS fractions with narrow molecular weight distributions obtained through depolymerization by different methods, while enzymatic HPLC was proven to be infeasible. Extraction recoveries of CS from monosaccharide mixed samples were > 93 %. The reliability was also validated by a small difference (−1.95 % to 4.12 %) relative to enzymatic HPLC results in analysing representative CS samples of different animal origins and suppliers.

Comparison of 3-nitrophenylhydrazine, O-benzyl hydroxylamine, and 2-picolylamine derivatizations for analysis of short-chain fatty acids through liquid chromatography coupled with tandem mass spectrometry.

Short-chain fatty acids (SCFAs) are metabolites derived from gut microbiota and implicated in host homeostasis. Hence, the profiling SCFAs from biological samples plays an important role in revealing the interaction between gut microbiota and pathogens. Previous studies, liquid chromatography-tandem mass spectrometry (LC-MS/MS) combined with various derivatization strategies have been performed to obtain the SCFA profiles from biological samples. However, it is poor evidence to compare these derivatization regents and conditions. Thus, we present the evaluation of three major derivatization reagents, namely 3-nitrophenylhydrazine (3-NPH), O-benzylhydroxylamine (O-BHA), and 2-picolylamine (2-PA), for the analysis of eight SCFAs classified as C2-C5 isomers using LC-MS/MS. First, in a reversed-phase LC separation, 3-NPH showed good retention capacity. Although O-BHA derivatization showed higher sensitivity and good retention capacity than 2-PA, only 2-PA derivatization could successfully separate eight SCFAs. The matrix effects in human serum ranged 77.1-99.0% (RSD ≤ 3.4%, n = 6) for 3-NPH derivatives, 91.0-94.6% (RSD ≤ 5.4%, n = 6) for O-BHA derivatives, 81.6-99.5% (RSD ≤ 8.0%, n = 6) for 2-PA derivatives. These compared results showed each characteristic of 3-NPH, O-BHA, and 2-PA for SCFA derivatization based on LC-MS/MS approaches.

Room-temperature synthesis of magnetic thiophene-based covalent organic frameworks for derivatization-assisted GC–MS analysis of estrogens in environmental water

Under room temperature conditions, a novel thiophene-based magnetic covalent organic framework (COF) was ingeniously synthesized for the first time, utilizing an uncomplicated and benign Schiff base reaction between 4,4′,4″,4‴-(pyrene-1,3,6,8-tetrayl)tetraaniline (PyTTA) and 2,2′-dithiophene-5,5′-dicarboxaldehyde (BTDA), with Fe3O4 serving as the magnetic nucleus. The fabricated Fe3O4@Py-BTDA COF nanocomposite displays superior crystallinity, homogenous pore size distribution, elevated magnetic responsiveness, and extraordinary thermal and chemical stability, which is an ideal sorbent for magnetic solid phase extraction (MSPE) of estrogens in environmental water samples. The presence of thiophene groups within the Fe3O4@Py-BTDA COF significantly bolsters the π-π interaction between the COF and the target analytes, and meanwhile provides sufficient hydrophobic sites and unique p-π interactions, thus becoming a crucial factor in augmenting the extraction efficiency of estrogens. Due to the high boiling point of estrogens, derivatization is necessary before gas chromatography–mass spectrometry (GC–MS) analysis. So, the conditions of derivatization, extraction and desorption were then systematically optimized. Under the optimal MSPE conditions, a rapid and sensitive method coupling MSPE with GC–MS was developed for the analysis of five estrogens in environmental water samples. The method showed good linearity (r2 > 0.9997) in the range of 0.05–100 μg L−1, low detection limits (4.0–7.0 ng/L), good spiked recoveries (91.56 %-105.80 %), and satisfactory relative standard deviations (RSD, less than 7.4 %). In addition, the method was successfully applied to the determination of estrogens in Yangtze River water, East Lake water, and tap water, with the recoveries in the range of 81.33 %-113.95 % and the RSDs in the range of 0.12 % to 7.69 % at different spiked levels. Estrone (E1) and estradiol (E2) were detected in the Yangtze River water with concentrations of 0.31 μg L−1 and 0.08 μg L−1. And, the prepared Fe3O4@Py-BTDA COF nanocomposite still provides good extraction effect after five cycles of application. The developed method is rapid, simple, sensitive, and environmentally friendly, and has good application in the analysis and determination of estrogens in environmental water samples.

Simultaneous quantification of total and free testosterone in human serum by LC-MS/MS.

Testosterone (TTe) and free testosterone (FTe) are clinically important indicators for the diagnosis of androgen disorders, so accurate quantitative determination of them in serum is clinically of paramount significance. Currently, there is no available method suitable for routine and simultaneous measurement of TTe and FTe. Here, we developed a new UPLC-MS/MS method to quantify serum TTe and FTe simultaneously and accurately. Rapid equilibrium dialysis was used to obtain FTe in serum followed by derivatization with hydroxylamine hydrochloride. With these strategies, TTe and FTe could be measured in single injection. After optimizing the extraction and derivatization conditions, the performance of LC-MS/MS was evaluated and applied to quantify the levels of TTe and FTe in clinical samples from 42 patients. The assays were linear for TTe within the range of 0.2-30ng/mL and for FTe within the range of 1.5-1000pg/mL. This improved method provided a limit of quantification for TTe of 0.2ng/mL and for FTe of 1.5pg/mL. The intra- and inter-run CVs were less than 4.3% and 3.6% for TTe and less than 8.2% and 6.7% for FTe, respectively. The intra- and inter-run accuracies for both TTe and FTe were in the range of 96.1-108.1%. Interference, carryover effect, and matrix effect were in acceptable range. In conclusion, our new LC-MS/MS method is simple to perform and can serve as a reliable method for simultaneous determination of TTe and FTe in clinical practice, providing important information for diagnosis, treatment, and monitoring of androgen-related diseases.

Isotope-labeling in situ derivatization and HS-SPME arrow GC-MS/MS for simultaneous determination of fatty acids and fatty acid methyl esters in aqueous matrices.

Fatty acids (FAs) and fatty acid methyl esters (FAMEs) co-occur in many samples, and analysis of both substance classes is frequently of high interest. To this end, this study introduces the first method for simultaneous determination of FAs and FAMEs including fully automated solvent-free solid-phase microextraction (SPME) arrow headspace extraction combined with isotope-labeling in situ FA derivatization with deuterated methanol (CD3OD). By using the chromatographic isotope effect (ΔRt = 0.03min) and the + 3m/z mass shift, FAs can be selectively differentiated from the FAMEs during gas chromatography tandem-mass spectrometry (GC-MS/MS) operated in the multiple reaction monitoring (MRM) aquisition mode. Additionally, an approach is presented to predict the retention times of deuterated compounds. Optimization of the derivatization conditions was accomplished by design of experiments and found to be 20min, 50°C, 4v/v% CD3OD, and pH 2.1. During method validation, FAs and FAMEs were calibrated in different concentration ranges by standard addition in five real matrices and ultrapure water leading to good linearities and method detection limits for FAs ranging from 1-30µgL-1 and for FAMEs from 0.003-0.72µgL-1. FAs and FAMEs were detected in real samples from surface water, wastewater treatment plant effluent, and three different bioreactor samples and could be quantified in concentrations ranging from 2-1056µgL-1 for FAs and 0.01-14µgL-1 for FAMEs.

Determination of Bisphenol A (BPA) in the Port of Gdynia Waters Using Gas Chromatography Coupled with Mass Spectrometry (GC-MS)

This paper presents a procedure for the determination of bisphenol A (BPA) in seawater. Gas chromatography coupled with mass spectrometry (GC-MS) was used as the analytical method, preceded by analyte isolation via solid-phase extraction (SPE). Initially, the best conditions for extraction, derivatization, and GC-MS analysis were established. The need for derivatization in the determination of BPA was investigated, and for this reason, two methods of sample preparation were compared: with and without the derivatization step. The parameters of the two methods of sample preparation were compared with each other, and a more efficient method was chosen for the analysis of marine water samples. Afterwards, the validation process was carried out and the following parameters were determined: limit of detection (LOD), limit of quantification (LOQ), linearity, precision, reproducibility, and repeatability. Finally, the results of the determination of bisphenol A in water samples collected from five harbor basins of the Port of Gdynia using an unmanned mobile research unit, HydroDron-1, were presented. The identified concentrations ranged from 0.01 µg/L to 0.03 µg/L, depending on the investigated area.

Practical benzylation of N,N-substituted ethanolamines related to chemical warfare agents for analysis and detection by electron ionization gas chromatography-mass spectrometry.

The benzylation of three low molecular weight N,N-disubstituted ethanolamines related to chemical warfare agents (CWAs) to furnish derivatives with improved gas chromatography-mass spectrometry (GC-MS) profiles is described. Due to their low molecular weight and polar nature, N,N-disubstituted ethanolamines are notoriously difficult to detect by routine GC-MS analyses during Organisation for the Prohibition of Chemical Weapons (OPCW) proficiency tests (PTs), particularly in scenarios when they are present at low levels (~1-10 ppm) amidst more abundant interferences. Our studies revealed that the optimal derivatization conditions involved the treatment of the ethanolamine with benzyl bromide in the presence of an inorganic base (e.g., Na2 CO3 ) in dichloromethane at 55°C for 2 h. This optimized set of conditions was then successfully applied to the derivatization of N,N-dimethylethanolamine, N,N-diethylethanolamine and N,N-diisopropylethanolamine present separately at 1 and 10 μg/mL concentrations in a glycerol-rich matrix sample featured in the 48th OPCW PT. The benzylated derivatives of the three ethanolamines possessed retention times long enough to clear the massive glycerol-containing matrix interferences. The protocol herein is introduced as an alternative method for derivatization of these CWA and pharmaceutically important species and should find broad applicability in laboratories where routine forensic analysis is carried out.

Development and validation of derivatization-based LC-MS/MS method for quantification of short-chain fatty acids in human, rat, and mouse plasma

Short-chain fatty acids (SCFAs), the end products of gut microbial fermentation of dietary fibers and non-digestible polysaccharides, act as a link between the microbiome, immune system, and inflammatory processes. The importance of accurately quantifying SCFAs in plasma has recently emerged to understand their biological role. In this work, a sensitive and reproducible LC-MS/MS method is reported for SCFAs quantification in three different matrices such as human, rat and mouse plasma via derivatization, using as derivatizing agent O-benzylhydroxylamine (O-BHA), coupled with liquid-liquid extraction. First, the instrumental parameters of the mass spectrometer and then the chromatographic conditions were optimized using previously SCFAs derivatives synthetized and used as standards. After that, the best conditions for derivatization and extraction from plasma were studied and a series of determinations were performed on human, rat, and mouse plasma aliquots to validate the overall method (derivatization, extraction, and LC-MS/MS determination). The method showed good performance in terms of recovery (> 80%), precision (RSD <14%), accuracy (RE < ± 10%) and sensitivity (LOQ of 0.01 µM for acetic, butyric, propionic and isobutyric acid) in all plasma samples. The method thus developed and validated was applied to the quantification of major SCFAs in adult and aged mice, germ-free mice and in germ-free recipient mice subjected to fecal transplant from adult and aged donors. Results highlighted how plasma concentrations of SCFAs are correlated with age further highlighting the importance of developing a method that is reliable for the quantification of SCFAs to study their biological role.

Contaminants of emerging concern: Silylation procedures, evaluation of the stability of silyl derivatives and associated measurement uncertainty

Analyte range of gas chromatography–mass spectrometry (GC–MS), widely used in environmental analysis, can be significantly broadened by derivatization. Silyl derivatives have improved volatility and thermal stability, chromatographic and mass spectrometric behaviors, and thus detection, structural elucidation and quantification. However, silylation use is often hindered by the stability of generated derivatives and the need to optimize silylation conditions. In this study, we optimized the derivatization conditions for 70 selected contaminants of emerging concern (CEC) using chemometrics approaches. N-methyl-N-(trimethylsilyl) trifluoroacetamide (MSTFA), N, O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) and BSTFA + 1 % trimethylchlorosilane (TMCS) were investigated, among which the latter gave the best yield. CEC were grouped in three derivatization protocols: 60 °C/45 min, 70 °C/90 min, and 70 °C/45 min. The short- and long-term stability of the CEC-trimethylsilyl (TMS) derivatives, i.e. for 28 days and up to 20 weeks were examined in a solvent and artificial wastewater (AWW) extract at 25 °C, 4 °C and − 18 °C, and during repeated five freeze-thaw (F/T) cycles, at two concentration levels: 100 μg/L and 1000 μg/L. Except for TMS derivatives of shikimic acid (SHA), quinic acid (QA) and sulfanilamide (SFA), the remaining derivatized compounds were stable in solvent (EtAc) for 28 days. In AWW extract, TMS derivatives of citric acid (CA), 17β-estradiol (E2), estriol (E3) and 17α-ethinyl estradiol (EE2) were unstable at 25 °C and 4 °C. Within up to 20 weeks, only the TMS derivatives of CA, meso-erythritol (ERY) and bisphenol BP (BPBP) were unstable. The most significant hydrolytic breakdown was observed during repeated F/T cycles. After three cycles, ≤ 20 % of the initial concentration of six and nine CEC-TMS derivatives had degraded in solvent and AWW extracts, respectively. According to the deep statistical comparison (DSC) approach, the most prominent degradation was observed for TMS derivatives of E2, CA, 9-hydroxyfluorene (9-HF), estrone (E1) and trans-3′-hydroxycotinine (T3HC) in solvent; E2, CA, 9-HF, E3 and E1 in AWW extracts and ERY, E2, CA, 9-HF and E1 in both matrices. Finally, the sample concentration of CEC accounted for most of the measurement uncertainty (MU).Based on our findings, we recommend the derivatized samples to be stored at −18 °C for up to 20 weeks to ensure the stability of their TMS derivatives. Sample freezing and thawing of not more than twice is allowed to maintain ≥80 % of the initial CEC-TMS concentration.

Metal–Organic Frameworks for Electrocatalytic CO2 Reduction into Formic Acid

Metal–organic frameworks (MOFs) are used in catalysis due to their high specific surface area and porous structure. The dispersed active sites and limited reaction space that render MOFs have the potential for highly selective electrocatalytic CO2 reduction reaction (ECO2RR). Meanwhile, formic acid (HCOOH) is attracting attention as a liquid product with high economic benefits. This review summarizes the MOFs and their derivatives applied for ECO2RR into HCOOH products. The preparation methods of MOFs as electrocatalysts and their unique advantages are discussed. A series of MOFs and MOF derivatives obtained by electrochemical reduction or carbonization processes are highlighted, including metal nanomaterials, carbon-based nanocomposites, single-atom catalysts, and bimetallic nanocomposites. Depending on the MOF building units (metal ions and organic linkers) and the reaction conditions of derivatization, MOF-based catalysts exhibit rich diversity and controllable modulation of catalytic performance. Finally, the challenges encountered at this stage and the future research directions of MOF-based catalysts are proposed.