Microwave-assisted Derivatization Research Articles

Evaluation of polypropylene microporous membranes as extraction devices for determination of carcinogenic aromatic amines in smoker urine by GC–MS/MS

Exposure to tobacco smoke is highly correlated to the incidence of different types of cancer due to various carcinogenic compounds present in such smoke. Aromatic amines, such as 1-naphthylamine (1-NA) and 2-naphthylamine (2-NA), are produced in tobacco burning and are linked to bladder cancer. Miniaturized solid phase extraction techniques, such as microporous membrane solid phase extraction (MMSPE), have shown potential for the extraction of aromatic compounds. In this study, a bioanalytical method for the determination of 1-NA and 2-NA in human urine was developed using polypropylene microporous membranes as a sorptive phase for MMSPE. Urine samples were hydrolyzed with HCl for 1 h at 80 °C, after which pH was adjusted to 10. Ultrasound-assisted MMSPE procedure was optimized by factorial design as follows. To each sample, 750 µL of methanol was added, and ultrasound-assisted MMSPE was conducted for 1 h with four devices containing seven 2 mm polypropylene membrane segments. After extraction, the segments were transferred to 400 µL of hexane, and desorption was conducted for 30 min. Extracts were submitted to a simple and fast microwave-assisted derivatization procedure, by the addition of 10 µL of PFPA and heating at 480 W for 3 min, followed by clean-up with phosphate buffer pH 8.0 and GC–MS/MS analysis. Adequate linearity was obtained for both analytes in a range from 25 to 500 µg L−1, while the multiple reaction monitoring approach provided satisfactory selectivity and specificity. Intra-day (n = 6) and inter-day (n = 5) precision and accuracy were satisfactory, below 15 % and between 85 and 115 %, respectively. Recovery rates found were 91.9 and 58.4 % for 1-NA and 2-NA, respectively, with adequate precision. 1-NA was found in first-hand smokers’ urine samples in a concentration range from 20.98 to 89.09 µg in 24 h, while it could be detected in second-hand smoker's urine samples, and 2-NA detected in all first and second-hand smokers’ urine samples. The proposed method expands the applicability of low cost MMSPE devices to aromatic amines and biological fluids.

A simple and rapid HPLC-UV method for the determination of valproic acid in human plasma using microwave-assisted derivatization with phenylhydrazine hydrochloride

This study presents an efficient high-performance liquid chromatography with ultraviolet detection (HPLC-UV) method for monitoring valproic acid (VPA) level in human plasma. This method is distinguished by its simplicity, cost-effectiveness, and rapid execution, addressing the limitations associated with other advanced analytical techniques like liquid chromatography-mass spectrometry (LC-MS), gas chromatography-mass spectrometry (GC-MS), and immunoassays, which are generally complex and costly for routine application. A challenge in analyzing VPA is its non-linear protein binding profile and the absence of a chromophore in its structure, making direct detection difficult. To overcome this, the study developed an efficient HPLC-UV for VPA determination in human plasma, utilizing a simplified and rapid microwave-assisted derivatization process. Due to the lack of a chromophore in VPA structure, this work developed a microwave-assisted derivatization of VPA using phenylhydrazine hydrochloride (PH HCl). The process optimization was achieved at 450 W for 50 s, facilitating effective HPLC-UV detection. The derivatized product was characterized using 1H nuclear magnetic resonance (NMR) and Fourier transform infrared spectrometer (FT-IR). The derivative, identified as (Z)-N-phenyl-2-propylpentanehydrazonic acid, demonstrated specificity in plasma analysis with no detectable interference. The method exhibited a linear response for VPA concentrations ranging from 30 to 150 μg/mL, with a correlation coefficient exceeding 0.99. Recovery varied between 86.7% and 107%, with a maximum coefficient of variation (CV) of 10.0%. The findings suggest that the microwave-assisted derivatization technique substantially improves the feasibility and cost-effectiveness of HPLC-UV for the analysis of VPA in plasma. This method provides a viable alternative to conventional HPLC methodologies, offering a balance of efficiency and economic practicality for VPA quantification.

Bibliometric Study of Microwave-Assisted Synthesis of Flavanone Derivatives

This study aims to describe various studies related to synthesizing flavanone derivatives using the microwave-assisted method with a bibliometric approach. Metadata information was collected from Scopus on June 30th, 2023, with three keywords (microwave-assisted OR microwave, synthesis, and flavanone) searched for article titles, abstracts, and keywords. Analysis and research mapping were carried out with VOSviewer. Of the 33 articles relevant for analysis, 15 keyword clusters were obtained, most of which contained a list of flavanone derivatives. Interestingly, none of these clusters contain keywords for well-known compounds from the flavanone group, such as pinostrobin, pinocembrin, or hesperetin. In other words, there is an excellent opportunity to obtain novelty for microwave-assisted derivatization studies of flavanones. The chances of publication of these studies are greater in Chemistry of Heterocyclic Compounds (Springer Nature), Oriental Journal of Chemistry (Scientific Publishers), and Tetrahedron Letters (Elsevier), each with three documents. Meanwhile, most researchers on this topic come from India with 13 documents. This information allows researchers on this topic to determine potential flavanones that have the opportunity to be derivatized by the microwave-assisted method.

Simple and Effective Derivatization of Amino Acids with 1-Fluoro-2-nitro-4-(trifluoromethyl)benzene in a Microwave Reactor for Determination of Free Amino Acids in Kombucha Beverages.

Kombucha is a fermentation product of sweetened tea with a symbiotic culture of acetic acid and yeast bacteria, consumed worldwide for its health-promoting properties. Few reports can be found about free amino acids among the health-promoting compounds found and determined in kombucha. These compounds influence the sensory properties of kombucha, and they are precursors of bioactive compounds, which have a significant role as neurotransmitters and are involved in biological functions. The presented studies proposed a convenient, simple, and “more green” procedure of the synthesis of amino acid derivatives, assisted by microwave energy, followed by chromatographic determination. The structure of 1-Fluoro-2-nitro-4-(trifluoromethyl)benzene was used as a suitable reagent for the derivatization of free amino acids in fermented kombucha beverages prepared from selected dry fruit such as Crataegus L., Morus alba L., Sorbus aucuparia L., Berberis vulgaris L., Rosa canina L., and black tea. The obtained results were discussed regarding the tested beverages’ application as a source of amino acids in one’s daily diet. The obtained results point out that the proposed microwave-assisted derivatization procedure prior to HPLC analyses allows for a significant time reduction and the limitation of using organic reagents.

Measurement of 7-dehydrocholesterol and cholesterol in hair can be used in the diagnosis of Smith-Lemli-Opitz syndrome

7-dehydrocholesterol (7-DHC) and cholesterol (CHOL) are biomarkers of Smith-Lemli-Opitz Syndrome (SLOS), a congenital autosomal recessive disorder characterized by elevated 7-DHC level in patients. Hair samples have been shown to have great diagnostic and research value, which has long been neglected in the SLOS field. In this study, we sought to investigate the feasibility of using hair for SLOS diagnosis. In the presence of antioxidants (2,6-ditert-butyl-4-methylphenol and triphenylphosphine), hair samples were completely pulverized and extracted by micro-pulverized extraction in alkaline solution or in n-hexane. After microwave-assisted derivatization with N,O-Bis(trimethylsilyl)trifluoroacetamide, the analytes were measured by GC-MS. We found that the limits of determination for 7-DHC and CHOL were 10 ng/mg and 8 ng/mg, respectively. In addition, good linearity was obtained in the range of 50–4000 ng/mg and 30–6000 ng/mg for 7-DHC and CHOL, respectively, which fully meets the requirement for SLOS diagnosis and related research. Finally, by applying the proposed method to real hair samples collected from 14 healthy infants and two suspected SLOS patients, we confirmed the feasibility of hair analysis as a diagnostic tool for SLOS. In conclusion, we present an optimized and validated analytical method for the simultaneous determination of two SLOS biomarkers using human hair.

Profiling organic acids in produced water samples using vacuum-assisted sorbent extraction and gas chromatography coupled to Fourier transform Orbitrap mass spectrometry

In this article, we describe the preliminary findings obtained with headspace vacuum-assisted sorbent extraction (VASE) as an alternative for sample preparation in the analysis of organic acids in produced water (PW). VASE is a headspace technique that combines the use of high-capacity sorbent traps and low-pressure conditions. Method development included extraction parameters and thermal desorption conditions. Multivariate optimization using design of experiments (DOE) was performed for variable screening and method optimization. A microwave-assisted derivatization protocol was proposed to convert the organic acids into its corresponding methyl esters (ME). The reaction was conducted in-sample prior to VASE extraction, and had the advantage of dismissing the use of organic solvents. The isolated fraction was analyzed by gas chromatography coupled to high resolution mass spectrometry (GC-HRMS). Quantitative analysis exhibited a linear range from 1 to 100 µg L-1. The reported detection limits ranged from 0.001 to 0.070 µg L-1 using the model acids. The method was successfully applied for qualitative analysis of PW samples. It was possible to detect important classes, such as hydrocarbons, oxygen- and nitrogen- containing compounds. Several NAs species with different double-bond equivalent (DBE) values and carbon numbers could be found in both samples. The greenness of the analytical method was also evaluated, exhibiting better environmental metrics when compared with traditional liquid–liquid extraction.

An ultrasensitive UHPLC-ESI-MS/MS method augmented with a controlled microwave derivatization reaction for quantitation of vitamin D3 and its major metabolites in COVID-19 patients

It is established that vitamin D deficiency is correlated with the disease severity in COVID-19 patients. However, the reliable and sensitive quantitation of vitamin D3 (D3) and its metabolites remains a difficult challenge. Herein, a novel ultrasensitive and reliable UHPLC-ESI-MS/MS method was developed and validated for the quantitation of D3 and its major metabolites in COVID-19 patients. The mass spectral sensitivity was augmented via controlled microwave-assisted derivatization reaction (CMDR) with 2-nitrosopyridine (Pyr-NO) at 65 °C for 2 min. CMDR hyphenation with UHPLC-MS/MS improves detection sensitivity while shortening separation and derivatization reaction times. The precursor to product ion transitions for D3, 25-hydroxy D3 (25(OH)D3), 1,25-dihydroxy D3 (1,25-(OH)2D3) and calcipotriol (CPT) as an internal standard were m/z 493.4 → 231.3, m/z 509.4 → 231.3, m/z 525.4 → 247.3, and m/z 521.4 → 247.3; respectively. The separation of the formed derivatives was conducted using a gradient elution mode with mobile phase A: formic acid (0.1%) in water and mobile phase B: formic acid (0.1%) in acetonitrile. The elution started with 40% (v/v) of B for 0.3 min then increased linearly to 90% (v/v) at 2 min on an Agilent EclipsePlus C18 (50 × 2.1 mm, 1.8 μm) column at a flow rate of 0.3 mL min−1. The method was validated using FDA standards for bioanalytical method validation over a concentration range of 0.02–50 ng mL−1 with correlation coefficient ≥0.9987 and the lower limit of quantitation (LLOQ) were 0.02–0.05 ng mL−1 in human plasma. The developed method has demonstrated excellent comparability to a well-established chemiluminescent immunoassay (CLIA) method for the analysis of D3 metabolites in human samples. The developed UHPLC-ESI-MS/MS method was implemented for routine and reliable quantitation of D3 and its major metabolites in COVID-19 patients.

Validation of a Microwave-Assisted Derivatization Gas Chromatography-Mass Spectrometry Method for the Quantification of 2-Hydroxybutyrate in Human Serum as an Early Marker of Diabetes Mellitus.

Circulating levels of 2-hydroxybutyrate (2HB) are highly related to glycemic status in different metabolomic studies. According to recent evidence, 2HB is an early biomarker of the future development of dysglycemia and type 2 diabetes mellitus and may be causally related to the progression of normal subjects to impaired fasting glucose or insulin resistance. In the present study, we developed and validated a simple, specific and sensitive gas chromatography-mass spectrometry (GC-MS) method specifically intended to quantify serum levels of 2HB. Liquid–liquid extraction with ethyl acetate was followed by 2 min of microwave-assisted derivatization. The method presented acceptable accuracy, precision and recovery, and the limit of quantification was 5 µM. Levels of 2HB were found to be stable in serum after three freeze-thaw cycles, and at ambient temperature and at a temperature of 4 °C for up to 24 h. Extracts derivatized under microwave irradiation were stable for up to 96 h. No differences were found in 2HB concentrations measured in serum or plasma EDTA samples. In summary, the method is useful for a rapid, precise and accurate quantification of 2HB in serum samples assessed for the evaluation of dysglycemia and diabetes mellitus.

Determination of glyphosate, aminomethylphosphonic acid, and glufosinate in river water and sediments using microwave-assisted rapid derivatization and LC-MS/MS.

Glyphosate (N-phosphonomethyl glycine) and glufosinate (ammonium dl-homoalanin- 4-methyl phosphinate) are nonselective, broad-spectrum, and highly polar herbicides that are wildly used for weed control in aquatic systems and vegetation control in non-crop areas. Aminomethylphosphonic acid (AMPA) is the major degradation product of glyphosate. To address the concerns to its environmental residue and the possible adverse effects, the analytical methods by using microwave-assisted derivatization were developed for determining glyphosate, AMPA, and glufosinate in river water and sediments. The methods applied the 9-fluorenylmethyloxycarbonyl chloride (FMOC-Cl) derivatization for the analytes. The microwave heating is first-time applied to reduce the FMOC-reaction time of glyphosate, AMPA, and glyphosate in the environmental samples to less than 2.5min. The microwave-assisted methods were successfully validated for river water and sediment. The linear ranges of 7.8-2000.0ng/L and 0.78-100.0ng/g were achieved by using 10mL of water and 2g of sediments. Glyphosate was found in 30/32% and 25/32% of 32 water and 32 sediments at 27.1-1353.9ng/L and 2.4-189.6ng/g levels. AMPA was found in 30/32% and 30/32% of 32 water and 32 sediments at 60.2-1509.0ng/L and 1.8-233.6ng/g levels. Glyphosate was found in 10/32% of 32 water at 14.8-503.1ng/L levels. No glufosinate residue was observed for 32 sediments. The residues of glyphosate and AMPA were wildly detected in the river waters and sediments near the agricultural regions, and glufosinate was less detected. This is the first study that reported herbicide levels in water and sediment from Taiwan rural areas using microwave-assisted rapid derivatization, useful information for environmental management.

Designed 3D N-doped magnetic porous carbon spheres for sensitive monitoring of biogenic amine by simultaneous microwave-assisted derivatization and magnetic-solid phase extraction

In this paper, the novel 3D N-doped magnetic porous carbon spheres (3D N-MPCSs) was constructed via a simple template-free and self-doping method, followed by a direct carbonization of polymer with Fe3+ for simultaneous activation and magnetization. For the first time, the designed 3D N-MPCSs was used as multifunctional (for extraction and magnetic separation) adsorbents for microwave-assisted derivatization and magnetic solid phase extraction, which exhibited excellent extraction ability for its large surface area, mesoporous structure, spherical morphology, and incorporation of N/O heteroatoms. Moreover, when the microwave-assisted derivatization was combined with the magnetic solid phase extraction, the extraction, derivatization and concentration was completed simultaneously within 135 s. Furthermore, this method has a low detection limit (0.059–0.073 ng mL−1) and high enhancement factors (333 < EFs < 382) for trace biogenic amine (BAs). The recoveries were between 92.3 and 108.8% with relative standard deviations less than 5.9%. Overall, a simple, rapid, efficient and sensitive method for the analysis of BAs in food samples was developed, which provided the basis for routine detection of food safety.

A reliable tool for detecting 7-dehydrocholesterol and cholesterol in human plasma and its use in diagnosis of Smith-Lemli-Opitz syndrome.

Smith-Lemli-Opitz syndrome is a birth defect caused by the deficiency of 7-dehydrocholesterol reductase in cholesterol biosynthesis pathway, which leads to accumulation of 7-dehydrocholesterol and reduction of cholesterol in body fluids. To effectively diagnose Smith-Lemli-Opitz syndrome and monitor therapy, a reliable method for simultaneous detection of 7-dehydrocholesterol and cholesterol is needed. In the presence of antioxidants (2,6-ditert-butyl-4-methylphenol and triphenylphosphine), 50 μL of human plasma were hydrolyzed at 70℃ for 40min with 1M potassium hydroxide in 90% ethanol, and then 7-dehydrocholesterol and cholesterol were extracted by 600 μL of n-hexane for three times. After microwave-assisted derivatization with 70 μL of N,O-bis(trimethylsilyl)trifluoroacetamide at 460 W for 3min, the analytes were measured by gas chromatography-mass spectrometry. The limits of detection were 100ng/mL for 7-dehydrocholesterol and 300ng/mL for cholesterol. Good linearity was obtained in the range of 1-600μg/mL for 7-dehydrocholesterol and 10-600μg/mL for cholesterol, which completely covered the biochemical levels of Smith-Lemli-Opitz syndrome patients that have been reported. A time-saving and accurate gas chromatography with mass spectrometry based method was developed for the determination of 7-dehydrocholesterol and cholesterol in human plasma, which also serves as a useful tool for Smith-Lemli-Opitz syndrome diagnosis, treatment, and research.

An eco-friendly solvent-free reaction based on peptide probes: design an extraction-free method for analysis of acrylamide under microliter volume.

Acrylamide is a group 2A carcinogen and potential endocrine disruptor that can enter the ecosystem by various routes and has recently become a dangerous pollutant. This widely used chemical can enter the human body via air inhalation, food or water consumption, or skin contact. In this study, we developed a peptide probe for the detection of acrylamide by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) after its micro-tagging with a peptide. Direct detection of acrylamide by MALDI-TOF MS is not feasible due to its poor ionization in the MALDI interface, which hinders its analysis by the technique. After microwave irradiation for 2min, the formed acrylamide-peptide derivative was detected easily by MALDI-TOF MS without the need for extraction procedures. The procedure does not involve organic solvents and a water-soluble peptide that allows detection of acrylamide in small sample volumes with a limit of detection (LOD) of 0.05ng/μL. The relative standard deviation (RSD) and relative error (RE) of the measurements were < 6.7% for intra- and inter-day assays. Gel-washing solutions from a polyacrylamide gel experiment were used as a model to study the efficiency of the developed method. Finally, we used the proposed method for the detection of free acrylamide in small volumes of lung epithelial cells (a model to test the air inhalation of acrylamide under a tiny volume of sample) and human urine. The developed method will enable rapid acrylamide detection in environmental and biological samples via a green approach based on microwave-assisted derivatization in water alongside the use of a less toxic derivatization reagent, reusable target plate, and miniaturization protocols.

Separation and determination of 3-hydroxyaspartate by online concentration capillary electrophoresis/laser-induced fluorescence with microwave-assisted derivatization.

A chiral analytical method was proposed based on capillary electrophoresis with laser-induced fluorescence detection coupled with microwave-assisted derivatization for the simultaneous baseline separation and sensitive detection of four stereoisomers of 3-hydroxyaspartate. The derivatization reaction of 3-hydroxyaspartate with 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole was greatly accelerated by microwave irradiation. Under the optimized conditions, the derivatization yield was increased by 20% and the derivatization time was shortened by 20 min when compared with those from conventional water bath heating. In addition, the sensitivity was improved by online sample concentration methods. The detection limit of l-threo-3-hydroxyaspartate obtained by large-volume sample stacking with polarity switching was 5.3nmol/L, which was around 1000-fold lower than that of the capillary electrophoresis/laser-induced fluorescence without stacking. The excellent analytical performance in terms of linearity and precision was also achieved. Furthermore, the developed method was successfully applied to the determination of 3-hydroxyaspartate in the spiked urine, and satisfactory recoveries were obtained ranging from 90.5 to 107.0%.

Validation of a Gas Chromatography-Mass Spectrometry Method for the Measurement of the Redox State Metabolic Ratios Lactate/Pyruvate and β-Hydroxybutyrate/Acetoacetate in Biological Samples.

The metabolic ratios lactate/pyruvate and β-hydroxybutyrate/acetoacetate are considered valuable tools to evaluate the in vivo redox cellular state by estimating the free NAD+/NADH in cytoplasm and mitochondria, respectively. The aim of the current study was to validate a gas-chromatography mass spectrometry method for simultaneous determination of the four metabolites in plasma and liver tissue. The procedure included an o-phenylenediamine microwave-assisted derivatization, followed by liquid-liquid extraction with ethyl acetate and silylation with bis(trimethylsilyl)trifluoroacetamide:trimethylchlorosilane 99:1. The calibration curves presented acceptable linearity, with a limit of quantification of 0.001 mM for pyruvate, β-hydroxybutyrate and acetoacetate and of 0.01 mM for lactate. The intra-day and inter-day accuracy and precision were within the European Medicines Agency’s Guideline specifications. No significant differences were observed in the slope coefficient of three-point standard metabolite-spiked curves in plasma or liver and water, and acceptable recoveries were obtained in the metabolite-spiked samples. Applicability of the method was tested in precision-cut liver rat slices and also in HepG2 cells incubated under different experimental conditions challenging the redox state. In conclusion, the validated method presented good sensitivity, specificity and reproducibility in the quantification of lactate/pyruvate and β-hydroxybutyrate/acetate metabolites and may be useful in the evaluation of in vivo redox states.

Profiling of Steroid Metabolic Pathways in Human Plasma by GC-MS/MS Combined with Microwave-Assisted Derivatization for Diagnosis of Gastric Disorders.

Steroid hormones are associated in depth to cellular signaling, inflammatory immune responses, and reproductive functions, and their metabolism alterations incur various diseases. In particular, quantitative profiling of steroids in plasma of patients with gastric cancer can provide a vast information to understand development of gastric cancer, since both sex hormones and glucocorticoids might be correlated with the pathological mechanisms of gastric cancer. Here, we developed a gas chromatography-tandem mass spectrometry-dynamic multiple reaction monitoring (GC-MS/MS-dMRM) method combined with solid-phase extraction (SPE) and microwave-assisted derivatization (MAD) to determine 20 endogenous steroids in human plasma. In this study, MAD conditions were optimized with respect to irradiation power and time. The SPE enabled effective cleanup and extraction for profiling of steroid hormones in human plasma samples. The MAD could improve laborious and time-consuming derivatization procedure, since dielectric heating using microwave directly increase molecular energy of reactants by penetrating through medium. Furthermore, dMRM method provided more sensitive determination of 20 steroids, compared to traditional MRM detection. The limits of quantification of steroids were below 1.125 ng/mL and determination coefficients of calibration curves were higher than 0.9925. Overall precision and accuracy results were below 19.93% and within ±17.04%, respectively. The developed method provided sufficient detection sensitivities and reliable quantification results. The established method was successfully applied to profile steroid metabolism pathways in plasma of patients with chronic superficial gastritis (CSG), intestinal metaplasia (IM), and gastric cancer. Statistical significances of steroid plasma levels between gastric disorder groups were investigated. In conclusion, this method provided comprehensive profiling of 20 steroids in human plasma samples and will be helpful to discover potential biomarkers for the development of gastric cancer and to further understand metabolic syndrome.

Use of hexamethyldisilazane as a silanizing agent in microwave-assisted derivatization for determining phenolic compounds in wine by gas chromatography

The objective of this study was to propose derivatization assisted by microwave radiation using hexamethyldisilazane as a low cost silanizing agent, in order to determine phenolic compounds in wines. Thus, an analytical method was developed and validated for the quantification of gallic acid, caffeic acid, resveratrol, (−) – epicatechin and (+) -catechin in wine samples by gas chromatography. The Box-Behnken design was used to optimize the experimental conditions of the derivatization reaction and extraction of the analytes from the matrix. The validated method presented limits of quantification in the range of 0.413–1.023 mg L−1 and standard deviation (%RSD) lower than 4.81%. Accuracy was verified by comparing the proposed method with a method that uses BSTFA as silanizing agent, with no significant differences between the determined concentration values. The proposed method was used to quantify the analytes in nine wine samples, with reduced analyte derivatization time, low derivative reagent cost and appropriate values of analytical figures of merit.

Derivatization Method for the Determination of Amino Acids in Tobacco by Gas Chromatography–mass Spectrometry

In this paper, we evaluated the use of a silylation reagent N-methyl-N-(tert-butyldimethylsilyl)trifluoroacetamide in the microwave-assisted derivatization method to replace a traditional prolonged heating method for the determination of 12 amino acids. Several parameters, including the kind of extraction solvent, extraction time, microwave power and microwave time, were optimized. The experiment showed that the optimal derivatization time was 3 min with a microwave power of 240 W. The calibration curves were linear with the correlation coefficients ranging from 0.995 to 1.000 in the concentration levels between 0.1–20 μg/mL and the relative standard deviations were between 4.4 and 18%. The limits of detection were 0.1–2.4 μg/mL and the recoveries of those compounds were 62–115%. A comparison of this method to other methods has demonstrated that the proposed method is a rapid and reliable sample-treatment procedure for amino acids determination in real tobacco samples.

Designed multifunctional visual observation of magnetic ionic liquid coupling with microwave-assisted derivatization for determination of biogenic amines

A multifunctional visual observation of magnetic ionic liquid (MIL) benzyltrioctylammonium thiocyanatecobalt (II) [N8,8,8,B+]2[Co(SCN)42-] with the long-chain alkyl and benzyl group structures was designed and synthesized as microextraction phase. Designed new structural MIL displays good hydrophobicity, high extraction capacity for both aromatic and aliphatic compounds, and has obvious color markers (blue color) which is easy visual separation from aqueous solution through a magnet. In the present work, a green, efficient and rapid samples pretreatment method based on simultaneous derivatization and extraction of aromatic (tyramine, histamine, phenylethylamine, tryptamine) and aliphatic (spermidine and spermine) biogenic amines (BAs) were performed. Microwave-assisted derivatization coupled with MIL-dispersive liquid–liquid microextraction (DLLME) was established for the determination of six BAs in different food samples via HPLC. The method was successfully applied for the analysis of beer and milk samples, and the recoveries of analytes were 93.0–110.3% and 91.2–111.6%, respectively. The limits of detection (LODs) were 0.51–1.49 μg L-1 for six BAs. These results have demonstrated that the proposed method has offered an effective, accurate, and sensitive methodology for BAs residue detection in food sample, and this method has great potential for the routine analysis of large numbers of samples on measuring different kinds of compounds.

Determination of Chloramphenicol and Nitrofuran Metabolites in Cobia, Croaker, and Shrimp Using Microwave-Assisted Derivatization, Automated SPE, and LC-MS/MS-Results from a U.S. Food and Drug Administration Level Three Inter-Laboratory Study.

An interlaboratory study was conducted to test a published, peer-reviewed manuscript in the Journal of AOAC INTERNATIONAL Vol 98, No. 3, 2015, "Quantitation of Chloramphenicol and Nitrofuran Metabolites in Aquaculture Products Using Microwave-Assisted Derivatization, Automated Solid-Phase Extraction, and LC-MS/MS." The purpose of this study was to demonstrate the performance of the method in shrimp, cobia, and croaker matrices. Three U.S. Food and Drug Administration laboratories participated in the collaborative study. The laboratories tested matrix blanks and laboratory-fortified matrix blanks at various levels in three separate matrices. The method evaluation included determination of the LOQ, accuracy, and precision. The reproducibility and repeatability of the RSD, % levels for matrix spikes fortified below the action level were < 10% for all residues in shrimp, < 13% for all residues in cobia except for 3-amino-2-oxazolidinone which was ≤ 22%, and < 16% for croaker. The RSD, % levels for all other spikes in the study were < 14%. Average percent recoveries for all matrices ranged from 81.6% - 102%. The study demonstrated that the method is acceptable for use for the combined determination of chloramphenicol and nitrofuran metabolites in the study matrices. The study showed acceptable quantitation for the high-throughput chloramphenicol and nitrofuran metabolites method.

Quadruplex stable isotope derivatization strategy for the determination of panaxadiol and panaxatriol in foodstuffs and medicinal materials using ultra high performance liquid chromatography tandem mass spectrometry

This work proposed a novel strategy based on quadruplex stable isotope derivatization for sensitive, accurate, speedy and green determination of panaxadiol (PD) and panaxatriol (PT). This strategy integrated with ultrasound-assisted dispersive liquid-liquid microextraction, microwave-assisted derivatization, and magnetic graphene oxide dispersive solid phase extraction as efficient sample pretreatment techniques, coupling with ultra-high performance liquid chromatography tandem mass spectrometry detection in multiple reaction monitoring mode for the analytical purpose of high-throughput, sensitivity, selectivity, green and accuracy. Quadruplex mass spectrometry sensitizing derivatization reagents, 3-N-(D0-/D3-methyl-, and D0-/D5-ethyl-)-2′-carboxyl chloride rhodamine 6 G, were designed, synthesized and applied for the high-throughput derivatization of hydroxyl‑containing PD and PT for the first time. The analogue derivatives of PD and PT standards using 3-N-propyl-2′-carboxyl chloride rhodamine 6 G as derivatization reagent were employed as the internal standards for the mass spectrometry quantitation to minimize matrix effect. All rhodamine 6 G derivatives of PD and PT were easily and selectively adsorbed by magnetic graphene oxide for efficient magnetic dispersive solid phase extraction before injection. Parameters of (micro-) extractions, derivatization and liquid chromatography-mass spectrometry conditions were all optimized in details. Method validation results consisting of linearity, accuracy, precision, repeatability, matrix effect, stability and limits of detection (LODs, 0.02 ng/mL for PD and 0.03 ng/mL for PT) were determined. The analytical performance of this method benefited from efficient integration of suitable sample pretreatment techniques and characteristic structure of rhodamine 6 G with four mass tags in derivatization reagents. The developed and validated method has been applied to the quantitation of PD and PT for the quality assessment of related foodstuffs and traditional Chinese medicinal materials.