Acetic Acid In Acetonitrile Research Articles

High Performance Chromatographic Determination of Asulam Residue in Agricultural Products

Asulam was extracted with 0.1% acetic acid in acetonitrile, acetone, water and diethyl ether successively. Following after clean up with florisil and neutral alumina solid phase extraction cartridge, the elute was determined by HPLC with UV detector. Recoveries were carried out by spiking the standard asulam at the levels of 0.1∼0.3 and 0.05∼0.2 ppm to citrus and sugarcane, respectively. The average recoveries were 83.5 to 90.9% for citrus and 80.6 to 86.7% for sugarcane, and both detection limits was 0.01 ppm.

Determination of 42 mycotoxins in oats using a mechanically assisted QuEChERS sample preparation and UHPLC-MS/MS detection

A method was developed and validated for the simultaneous determination of 42 mycotoxins in oats. The method includes all the mycotoxins listed under Commission Regulation 1881/2006 and Commission Recommendation 165/2013, the emerging mycotoxins (beauvericin, alternariol, alternariol-methyl-ether and enniatins), and two masked metabolites, namely deoxynivalenol-3-glucoside and T-2-glucoside. The method also focuses on a wide range of analytes of toxicological interest. The sample preparation involved extraction with an aqueous acetic acid solution and acetonitrile, followed by QuEChERS with mechanically assisted vibrational shaking. No further clean-up steps were employed, and analysis was performed using ultra-high performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS). Trueness ranged between 78% and 158%, while precision ranged from 1.7% to 49.9% under within-laboratory reproducibility conditions. Beside the high degree of accuracy and sample throughput provided, the method can be applied to a large number of compounds currently not regulated, thus generating knowledge and for risk assessment purposes.

Anthocyanin fingerprinting and dynamics in differentially pigmented exotic soybean genotypes using modified HPLC–DAD method

More than as a phenotypic marker for breeding, seed coat colour of soybean is gaining momentum as a nutraceutical marker owing to the multitude of medicinal effects provided by anthocyanins. The acute obstacle for large scale phenotyping is a rapid, reliable and accurate quantification which simultaneously determines various anthocyanins and hence, in this study, the modified method efficiently separated cyanidin-3-glucoside (C3G), delphinidin-3-glucoside (D3G) and petunidin-3-glucoside (Pt3G) forms by eluting through a RP-C18 column with an optimized isocratic mobile phase containing 18% solvent B (0.4% trifluoro acetic acid in acetonitrile) in solvent A (0.4% trifluoro acetic acid in water). The elution profile of anthocyanins were C3G > D3G > Pt3G, with C3G as the predominant (~ 85%) form. The modified method was validated in terms of linearity (R2 = 0.998), low limit of detection (LOD = 5.8 μg ml−1), limit of quantification (LOQ = 22.25 μg ml−1), precision, repeatability, stability and recovery. C3G dynamics was found increased in a linear trend from 30DAF to later developing stages until maturity. The investigation on characterization of exotic soybean genotypes revealed that, maximum C3G content of 4.9 mg g−1 was in UPSL496 and the least in EC471921 (3.56 mg g−1). There was a positive correlation observed among all the variables, like monomeric anthocyanin content (MAC), C3G, D3G and Pt3G. Clustering and heat map analysis information on this efficient method can be used for future research for germ plasm evaluation and for developing nutritionally C3G enriched high yielding varieties.

Bismuth for Controlled Assembly/Disassembly of Transition-Metal Oxo Clusters, Defining Reaction Pathways in Inorganic Synthesis and Nature.

Trivalent bismuth is a unique heavy p-block ion. It is highly insoluble in water, due to strong hydrolysis tendencies, and known for low toxicity. Its lone pair is structure-directing, providing framework materials with structural flexibility, leading to piezoelectric and multiferroic function. The flexibility it provides is also advantageous for dopants and vacancies, giving rise to conductivity, luminescence, color, and catalytic properties. We are exploiting Bi3+ in a completely different way, as a knob to "tune" the solubility and stability of transition-metal oxo clusters. The lone pair allows capping and isolation of metastable cluster forms for solid-state and solution characterization. With controlled release of the bismuth (via bismuth oxyhalide metathesis), the metal oxo clusters can be retained in aqueous solution, and we can track their reaction pathways and conversion to related metal oxyhydroxides. Here we present isolation of a bismuth-stabilized MnIV cluster, fully formulated [MnIV6Bi2KO9(CH3COO)10(H2O)3(NO3)2] (Mn6Bi2). In addition to characterization by single-crystal X-ray diffraction, solution characterization in acetonitrile and acetonitrile-acetic acid by small-angle X-ray scattering (SAXS) and electrospray ionization mass spectrometry shows high stability and the tendency of Mn6Bi2 to link into chains by bridging the bismuth (and potassium) caps with nitrate and acetate ligands. On the other hand, the dissolution of Mn6Bi2 in water, with and without metathesis of the bismuth, leads to the precipitation of related oxyhydroxide phases, which we characterized by transmission electron microscopy (TEM), electron diffraction, and energy-dispersive spectroscopy, and the conversion pathway by SAXS. Without removal of bismuth, amorphous manganese/bismuth oxyhydroxides precipitate within a day. On the other hand, metathesis of BiOBr yields a solution containing soluble manganese oxyhydroxide prenucleation clusters that assemble and precipitate over 10 days. This allows tracking of the reaction pathway via SAXS. We observe one-dimensional growth of species, followed by the precipitation of nanocrystalline hollandite (identified by TEM). The hollandite is presumably templated by the K+, originally in the crystalline lattice of Mn6Bi2. In this Forum Article that combines new results and prospective, we compare these results to prior studies in which we first introduced the use of capping Bi3+ to stabilize reactive clusters, followed by destabilization to understand reaction pathways in synthesis and low-temperature geochemistry.

FaPEx® Multipesticide Residues Extraction Kit for Minimizing Sample Preparation Time in Agricultural Produce

Abstract Background: The quick, easy, cheap, effective, rugged, and safe method, generally applied to the determination of pesticide residues in food, has been recently modified and adopted for the analysis of pesticide residues worldwide, including Taiwan. Objective: The method still needs to be improved, particularly in efficiency and normalization, because the time costs 20–30 min for extraction and cleanup of multiple pesticides in every food. Methods: In this study, we present a highly efficient and simple sample preparation method that was developed for the determination of 380 pesticide residues in food, including mangoes, scallions, bok choy, apples, carrots, and pea seedlings. The homogenized 1 g samples mixed with 5 mL 1.0% acetic acid in acetonitrile were pushed through the FaPEx® (fast pesticide extraction) kits in a dropwise manner to obtain sample extracts. The total processing time was less than 15 min. The extracts were subject to chromatographic separation followed by GC–tandem MS (MS/MS) and LC–MS/MS analysis. Results: For more than 270 pesticide residues in these foods, the test gave acceptable mean recoveries, ranging between 70 and 120%, and relative SDs below 20%. The LOQ was at least 0.01 mg/kg for 380 pesticides. Conclusions: The developed method can greatly reduce the time needed for multiple pesticide residues analysis. Highlights: FaPEx is used for the extraction of pesticide residues that relies on single-use pre-filled sealed cartridges. FaPEx diminishes operation time, glassware demand, and laboratory space requirement. It also significantly decreases the amount of chemical solvents.

Development and Validation of a Simple LC-MS Method for the Quantification of Oxytocin in Dog Saliva.

Oxytocin (OT) is a mammalian neuropeptide with various functions in regulating birth, lactation, parenting, and social recognition. The study of OT became of increasing interest for the petcare industry due to its role in animal behavior and socialization. In the present study, a simple, sensitive, and accurate liquid chromatography-mass spectrometry (LC-MS) method for quantifying OT in dog saliva was developed and validated. OT and its deuterated internal standard (OT-d5) were detected with multiple reaction monitoring (MRM) in a positive ion mode using an AB Sciex 6500+ QTRAP mass spectrometer. Chromatographic separation was achieved by using an ACE Excel C18 column and a gradient elution at a flow rate of 0.5 mL/min over a 5 min run. The mobile phases consisted of 0.1% (v/v) acetic acid in water and 0.1% (v/v) acetic acid in acetonitrile. After development and optimization, the performance of the method was validated to prove its reliability. Calibration curves were linear over the range of 50–20,000 pg/mL and recovery of OT was above 87.8%. The validated method was successfully applied to evaluate OT concentrations in multiple batches of dog saliva samples.

High Performance Liquid Chromatography (HPLC) Method for Determination of Isoflavones Content in Shade-Tolerant Soybean Dena I

Soybeans (Glycine max (L.) Merrill) are the most common source of isoflavones in human foods which useful for health as preventions of cardiovascular disease, cancer, diabetes, hypertension, osteoporosis, and menopause. The amount of isoflavones in soybeans may differ significantly depends on both genetic and environmental factors. Among the four forms of isoflavones, the highest biological activity is indicated by isoflavones aglycones i.e., genistein, daidzein, and glycitein. Genistein and daidzein found as major compounds with significant amounts contained in soybeans. Indonesian Legumes and Tuber Crops Research Institute (ILETRI) cultivate a shade-tolerant soybeans variety called Dena I to overcome the production of soybeans in Indonesia. Although finding exist for Dena I variety, there are no firm data regarding the isoflavones content of this variety. In this research, high performance liquid chromatography (HPLC) method using a C-18 column with UV detection in optimum condition was performed to identify and quantify the isoflavones content in the extract of Dena I soybean. The satisfied separation was obtained using the mobile phase of acetonitrile-acetic acid 0.1% with the gradual increase of acetonitrile 15-30%, the flow rate of 1 mL/min, and detection wavelength of 260 nm. Isoflavone genistein in Dena I extract was eluted at the retention time (tR) of 24.696 min, the same way with the retention time (tR) of standard genistein of 24.490 min. The concentration of genistein was found 0.0524 mg/g Dena I soybean.

Development and Validation of Novel UPLC-MS/MS Method for the Analysis of Macitentan in Pharmaceutical Formulations

Introduction: Macitentan is an endothelin receptor antagonist drug used in the treatment of pulmonary arterial hypertension. Materials and Methods: A new, sensitive, simple, accurate and rapid ultra-performance liquid chromatography in combination with tandem triple quadruple mass spectrometry (UPLC-MS/MS) method has been developed and validated for the determination of macitentan in pharmaceutical formulations. Macitentan and bosentan which are used as internal standard (IS) were detected using atmospheric pressure chemical ionization (APCI) in positive ion, multiple reaction monitoring (MRM) mode by monitoring mass transitions (precursor to product) m/z 589.1→203.3 and 552.6→311.5, respectively. Chromatographic separation was carried out on reverse phase C18 column (5 µm, 4.6 * 150 mm). Water containing 0.2 % acetic acid in acetonitrile (10:90, v/v) was used as the mobile phase in the isocratic elution. The system was optimized with injection volume of 10 µL, column temperature of 35 °C and flow rate of 1 mL min-1 Retention times were 1.97 min for macitentan and 1.72 min for IS. Results and Discussion: The calibration curve with a high correlation coefficient (0.9997) was linear range 0.5-500 ng mL-1. The lower limit of quantitation (LLOQ) and average recovery values were determined as 0.5 ng mL-1 and 99.7 %, respectively. The developed novel method has been successfully applied for the determination of macitentan in pure form and pharmaceutical formulations. Conclusion: The present method is the first study developed and validated for the determination of macitentan from the pharmaceutical preparations and pure form by UPLC-MS/MS method in the literature.

Tissue distribution study of mangiferin after intragastric administration of mangiferin monomer, Rhizoma Anemarrhenae, and Rhizoma Anemarrhenae-Phellodendron decoctions in normal or type 2 diabetic rats by LC-MS/MS

A simple, accurate, and reliable liquid chromatography-mass spectrometry (LC-MS/MS) method was developed and validated for the determination of mangiferin in rat plasma and tissue homogenates using rutin as an internal standard (IS). Chromatographic separation was achieved on a Shiseido CAPCELL PAK C18 column (150 × 2.0 mm, 5 μm) using a gradient elution of 1% acetic acid in water and methanol at a flow rate of 300 μL·min−1. Quantification was performed on an API 4000+ triple-quadrupole mass spectrometer equipped with a turbo electrospray ionization (ESI) source in positive ion multiple reaction monitoring (MRM) mode. Selected ion monitoring transitions of 423.1 → 273.1 and 611.4 → 303.3 were chosen to quantify mangiferin and IS. Biological samples were pretreated via protein precipitation with acetonitrile-acetic acid. The standard calibration curves were above the ranges of 2 to 500 ng·mL−1 and 5 to 2000 ng·mL−1 for tissues, and 1 to 600 ng·mL−1 for plasma. All calibration curves for tissue and plasma samples showed good linearity (r ≥ 0.9974) over the concentration ranges. Intra- and inter-day precisions were <14.0%, and accuracy ranged from 97.2% to 111.7%. The established method was successfully applied on mangiferin tissue distribution following the intragastric administration of mangiferin, Rhizoma Anemarrhenae (A. Rhizoma) decoction, or Rhizoma Anemarrhenae-Phellodendron (herb pair, HP) decoction under healthy or diabetic conditions. Mangiferin was detected from all the tested tissues (except for brain) after monomer administration, and the concentrations were lower compared with the decoction groups. Distributions in the HP group were lower than those in the A. Rhizoma group, but mangiferin content in pancreas was obviously higher than in other tissues and in the A. Rhizoma group. Compared with healthy rats, mangiferin distributions in pancreas and intestine were lower in diabetic rats administered with the same dose of the herb pair, but still higher than those in other tissues. In addition, distributions in liver, spleen, lung, kidney, stomach, and plasma were higher than those in the normal group.

FaPEx® Multipesticide Residues Extraction Kit for Minimizing Sample Preparation Time in Agricultural Produce

Background: The quick, easy, cheap, effective, rugged, and safe method, generally applied to the determination of pesticide residues in food, has been recently modified and adopted for the analysis of pesticide residues worldwide, including Taiwan. Objective: The method still needs to be improved, particularly in efficiency and normalization, because the time costs 20-30 min for extraction and cleanup of multiple pesticides in every food. Methods: In this study, we present a highly efficient and simple sample preparation method that was developed for the determination of 380 pesticide residues in food, including mangoes, scallions, bok choy, apples, carrots, and pea seedlings. The homogenized 1 g samples mixed with 5 mL 1.0% acetic acid in acetonitrile were pushed through the FaPEx® (fast pesticide extraction) kits in a dropwise manner to obtain sample extracts. The total processing time was less than 15 min. The extracts were subject to chromatographic separation followed by GC-tandem MS (MS/MS) and LC-MS/MS analysis. Results: For more than 270 pesticide residues in these foods, the test gave acceptable mean recoveries, ranging between 70 and 120%, and relative SDs below 20%. The LOQ was at least 0.01 mg/kg for 380 pesticides. Conclusions: The developed method can greatly reduce the time needed for multiple pesticide residues analysis. Highlights: FaPEx is used for the extraction of pesticide residues that relies on single-use pre-filled sealed cartridges. FaPEx diminishes operation time, glassware demand, and laboratory space requirement. It also significantly decreases the amount of chemical solvents.

Ultrahigh-performance liquid chromatography with tandem mass spectrometry for the determination of 10 alkaloids in beagle plasma after the oral administration of the three Coptidis rhizoma extracts

Ethnopharmacological relevanceCoptidis rhizoma (CR) is the dried rhizome of the ranunculaceous plant CR. For decades in China, this plant has been used to treat hypertension, hyperlipidemia, and chronic diarrhea and has been officially included in the Chinese Pharmacopoeia. The present paper presents a review of the pharmacokinetics of CR. Aim of the studyThe pharmacokinetic studies and differences of 10 alkaloids among Coptis deltoidea C. Y. cheng et Hsiao, Coptis chinensis Franch and Coptis teeta Wall. Are seldom reported. This study is the first to determine corydaline, dehydrocorydaline, tetrahydropalmatine, palmatine, magnoflorine, jatrorrhizine, berberine, worenine, berberrubine, and coptisine, which adopted an ultrahigh-performance liquid chromatography-electrospray ionization-tandem mass spectrometry, simultaneously. Materials and methodsChromatographic separation was performed within 8 min by using an Agilent SB-C18 column (150 mm × 2.1 mm, 1.8 μm) with gradient mobile phase consisting of 0.3% acetic acid water (v/v) and acetonitrile at a flow rate of 0.3 mL/min. Multiple reaction monitoring mode was used to detect the tandem mass spectrum in the positive ionization mode by electrospray ionization source. ResultsThe method was fully validated to be linear over a wide concentration (r > 0.9916), and the linear concentration range was 0.195–2260 ng/mL. Intra- and interday precisions were below 14.19% and 18.56% for the 10 analytes, respectively. The accuracy ranged from −9.30% to 6.31%. The extraction recovery of the 10 alkaloids and internal standard ranged from 79.76% to 95.37%. Pharmacokinetic comparative study showed that the Cmax and AUC0-∞ values of dehydrocorydaline, tetrahydropalmatine, palmatine, magnoflorine, jatrorrhizine, berberine, worenine, berberrubine, and coptisine increased significantly (p < 0.05), which was different for beagles after oral administration. The results can help determine the mechanism of action and guide clinical application of these three extracts. ConclusionThis validated method was successfully applied for the pharmacokinetics study of beagle plasma after oral administration of three CR extract types.

Water-soluble and air-stable [2Fe-2S]-metallopolymers: A new class of electrocatalysts for H2 production via water splitting

[2Fe–2S] organometallic complexes are effective electrocatalysts for the reduction of weak acids in acetonitrile to generate molecular hydrogen (H2) (hydrogen evolution reaction, HER). Incorporation of such a [2Fe–2S] catalytic site into metallopolymers has been achieved using atom transfer radical polymerization (ATRP). These well-defined polymers have been structurally characterized by SEC, 1H NMR and IR spectroscopy. These metallopolymers catalyze the electrochemical reduction of acetic acid in acetonitrile. In addition, [2Fe–2S] metallopolymers appended with amino groups were shown to be water-soluble and potent electrocatalysts for H2 production at pH 7. In addition to the exceptional activity of these [2Fe–2S] metallopolymers in water, these catalysts maintain catalytic activity in air unlike comparable molecular catalysts.

Determination of Bisphenol A (BPA) in Commercially Packaged Ready-to-Consume Carbonated and Noncarbonated Water and Nonalcoholic Beverages: A Single-Laboratory Validation Study, First Action 2017.15.

Background: Bisphenol A (BPA) is an endocrine-disrupting compound that could migrate to beverages from packaging materials. AOAC INTERNATIONAL issued a call for methods for determination of free BPA in beverages based on the AOAC Standard Method Performance Requirement (SMPR®) 2017.018. Objective: The objective of the single-laboratory validation (SLV) study was to validate a method for the analysis of BPA in relevant beverages and evaluate its performance characteristics against the AOAC SMPR 2017.18. Methods: The analytical method involves extraction of a beverage sample (10 mL) using 10 mL 1% acetic acid in acetonitrile after the addition of isotopically labeled internal standard. Sodium chloride is added to salt out BPA into the acetonitrile phase. After centrifugation, a freeze-out step is used to remove coextracted lipids. An aliquot of the supernatant upper layer is then analyzed using high-pressure LC coupled to tandem mass spectrometry in electrospray negative ionization mode. Results: Accuracy, repeatability, and intermediate precision were determined by spiking 10 representative nonalcoholic beverage matrixes at three concentration levels. Individual percent recoveries ranged between 76.5 and 113.2%, 86.2 and 114.8%, and 90.9 and 109.3% for the spike levels of 0.3, 1.5, and 20 μg/L, respectively. The repeatability and intermediate precision results were in the range of 0.2-11.3% and 1.8-11.1%, respectively. The LOD was estimated at ≤0.1 μg/L and LOQ was validated at 0.3 μg/L. Conclusions: The validated method performance characteristics met the requirements stated in the AOAC SMPR 2017.018. This method was approved AOAC First Action Official MethodsSM 2017.15. Highlights: SLV study evaluating free BPA at three concentration levels (0.3, 1.5, and 20 μg/L) in 10 types of commercially packaged nonalcoholic beverages (as recommended for the method validation in the AOAC SMPR 2017.018). Validated method performance characteristics (LOD, LOQ, analytical range, accuracy, and precision) met the AOAC SMPR 2017.018. Method approved as the AOAC First Action Official Method 2017.15.

Simultaneous determination of 58 pesticides and relevant metabolites in eggs with a multi-functional filter by ultra-high performance liquid chromatography-tandem mass spectrometry

A sensitive method for the simultaneous determination of 58 pesticides and relevant metabolites in eggs was developed using ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) after clean-up with a multi-functional filter (MFF) based on quick, easy, cheap, effective, rugged, and safe method (QuEChERS). The egg sample was extracted with 5 ml water and 10 ml 1% acetic acid in acetonitrile and then salt out with sodium chloride. The extracted solution was filtered directly through an MFF containing 50 mg PSA, 50 mg C18, and 150 mg magnesium sulphate before UHPLC-MS/MS analysis. The clean-up and filter procedures were integrated using the MFF to substantially improve the work efficiency. Good linearity was shown for each analyte, and all the correlation coefficients exceeded 0.99. The recoveries in the eggs at the five spiked levels were 74.4%–115.2%, and the relative standard deviations (RSDs) were less than 15.3%. The limit of detection (LOD) and the limit of quantitation (LOQ) of 58 pesticides and 8 metabolites in eggs were 0.1–1.0 μg/kg and 0.2–5.0 μg/kg, respectively. The decision limit (CCα) and detection capacity (CCβ) were 3.4–111.1 μg/kg and 6.8–122.1 μg/kg, respectively. This method has also been successfully applied in the determination of actual eggs samples. This developed method is more effective and faster in the monitoring of pesticide residue in eggs compared to the traditional analytical method.

Intermolecular Hydrogen Bond in Acetic Acid Solutions. Raman Spectra and ab initio Calculations

C=O vibrational bands of various aggregated formations of pure acetic acid in the Raman spectra have different values of the depolarization ratio. Ab initio calculations using the Gaussian 98 W program in the Hartree-Fock approximation with the basic set of Gaussian functions RHF 6-31G++(d, p) show that this is how it should be. Thus, the formation of aggregates from molecules leads not only to a change in the dipole moment of the molecules, but also to a change in the bond polarizability tensor. Calculations according to this program showed that one of the hydrogen atoms of CH3 group of acetonitrile can participate in the intermolecular hydrogen bond. This can lead to the formation of closed acetonitrile-acetic acid dimers. However, a comparison of the calculated and experimental data shows that in the case of acid-acetonitrile molecules, the H-bond is formed in the direction of the elongation –О-Н…N of acetonitrile molecules. The activity of one of the hydrogen atoms of the CH3 group of acetonitrile leads to the formation of closed dimeric aggregates in pure acetonitrile with a shift of the СN band of acetonitrile towards lower frequencies. The low-frequency asymmetry of СN acetonitrile band in the Raman spectra is associated with the presence of such aggregates in liquid acetonitrile.

Sensitive inexpensive chromatographic determination of an antimicrobial combination in human plasma and its pharmacokinetic application

This study represents simple inexpensive chromatographic determination of ciprofloxacin (CIP) and tinidazole (TIN) simultaneously in human plasma using HPLC-DAD followed by a pharmacokinetic application. C18 column was used as stationary phase with isocratic elution of a mobile phase composed of acetic acid solution (2%) and acetonitrile (85: 15, v/v) and ornidazole as internal standard (IS) with UV detection at 318 nm. The two drugs and the IS were separated at 6.55, 7.91 and 11.07 min for CIP, TIN and IS, respectively, with good selectivity and sensitivity for their analysis in presence of plasma matrix components and the drugs' metabolites. Sample preparation involved only protein precipitation without any complicated extraction procedures decreasing analysis time. For method validation, FDA regulations for analysis in biological fluids were followed. Pharmacokinetic (PK) study on six healthy volunteers was conducted after single oral dose administration of 500 and 600 mg of CIP and TIN, respectively. Dugs' plasma levels were followed for 12 or 72 h post dosing for CIP and TIN, respectively, and different PK data for the two drugs were calculated and they were comparable to the reported values demonstrating successful future application of the presented method in PK, bioequivalence and bioavailability studies.

Ultrahigh-performance liquid chromatography-tandem mass spectrometry (UHPLC–MS/MS) assay for simultaneous quantifications of CZ48, lactone-stabilized camptothecin, and camptothecin and their pharmacokinetic and biliary evaluations in rats

CZ48, a prodrug of camptothecin (CPT), has a broad spectrum of antitumor activity against various types of human tumors without severe toxicity in preclinical human tumor-xenografted mouse models, which facilitates further preclinical and clinical pharmacokinetic (PK) evaluations of CZ48. In this study, a UHPLC–MS/MS method was developed and validated to simultaneously quantify CZ48 and CPT in rat plasma and bile. Detection was performed using the API 3200 Q Trap triple quadrupole mass spectrometer in a positive ion mode. Chromatographic separation was achieved on Waters ACQUITY UPLC BEH Shield RP18 column with a gradient elution at a flow rate of 0.45 ml/min, using mobile phases of 0.1% acetic acid in water (A) and 0.1% acetic acid in acetonitrile (B). The method was linear at the concentration ranges of 0.98 (LLOQ) −1000 ng/ml of CZ48 and CPT in rat plasma and 3.9 (LLOQ) −1000 ng/ml in bile. Intra- and inter-day accuracy and precision values did not deviate by more than 6.57% and 10.15% for CZ48 and CPT, respectively, in plasma, and 12.09% and 13.48% in bile. Extraction recoveries of CZ48 were 90.18–95.42% from plasma and 86.51 −91.66% from bile. The recoveries of CPT were 91.56–97.06% from plasma and 84.89–89.15% from bile. No significant matrix effects were observed in plasma and bile within 14.00% and 16.19%, respectively. CZ48 and CPT in plasma were stable after extraction process and different storage conditions, including bench-top, processed sample in autosampler, three cycles of freeze and thaw, and long-term (3 month) stability at −80 °C. The application of the validated method was demonstrated by a PK study after an intravenous dose of CZ48 in rats.

Liquid Chromatographic Determination of Malondialdehyde in Plasma Samples After Liquid–Liquid Microextraction

Background: Malondialdehyde is a product of lipid peroxidation of polyunsaturated fatty acids in foods and biological samples and widely used as biomarker of oxidative stress in various diseases. We describe the validation of a new microextraction-LC-UV method for the determination of malondialdehyde (MDA) in the form of 2,4-dinitrophenylhydrazine (DNPH) derivatization in plasma samples. Objective: A new microextraction technique called vortex and N2 assisted liquid-liquid microextraction has been developed for the determination MDA in plasma samples. Method: The DNPH-derivatized MDA was extracted into ethyl acetate as an extraction solvent and measured by LC-UV at 310 nm after evaporation of ethyl acetate and re-dissolving in mobile phase composed of 0.2% acetic acid–acetonitrile (50:50; v/v). This method validated according to U.S. Food and Drug Administration guidelines. Results: The limit of detection of MDA was 0.038 µmol L-1 (2.74 µg L-1) and the intra and interday relative standard deviations were in the range of 3.8-5.0% and 5.5-9.4%, respectively for different concentrations of MDA. Conclusion: A precise and valid method to measure MDA as DNPH derivatization in plasma samples using LC was proposed. Keywords: Malondialdehyde, 2, 4-dinitrophenylhydrazine, vortex assisted liquid liquid microextraction, N2 assisted liquid liquid microextraction, validation, samples.

Development and validation of modified QuEChERS method coupled with GC-MS/MS for 123 pesticide residues in food

In this study, a gas chromatography-tandem mass spectrometry (GC-MS/MS) instrument, which has been widely used in recent years and has high separation power, selectivity and ability to identify pesticides has been used. It is aimed that the main criterion of this analytical method, in which the QuEChERS methodology is used, is applicable to fast, easy, cheap, environmentally friendly and different matrices. At the same time with this method, 123 pesticide residues and their degradation products were quantitatively assayed by GC-MS/MS as well as method validations in tomatoe, lemon, lettuce, almonds, raisins, honey, green pepper, milk and flour. Tomatoe was selected as potential reference matrixes for the target. The steps of concentration and solvent exchange were performed in the resultant extracts for the purpose of improving analytical performance in terms of recovery, precision, linearity, of reducing the amount of co-extracts. Multiple reaction monitoring (MRM) was used to identify and quantify the pesticides. The samples were extracted with 1% acetic acid in acetonitrile, anhydrous magnesium acetate, anhydrous magnesium sulfate and clearing agent. For all pesticides, good linear calibrations with coefficients (R2) ≥0.99 for nearly all of the analytes were obtained. Limit of quantitation of most of the pesticides were in the range of 5-10 ng/g, and recovery of the method validation accuracy parameter was done at two different concentrations 10 ng/g and 50 ng/g were 88.6 - 99.7% and CV 1.60 – 14.0%.

Experimental confirmation of a new invariant for a non-linear chemical reaction

The first non-Onsager thermodynamic invariant for a non-linear chemical system was found experimentally in all domains using “the dual kinetic experiment” in a batch reactor in which the reaction of esterification of ethanol with acetic acid was studied jointly with the reaction of hydrolysis of ethyl acetate. In a typical experiment, a glass flask was loaded with 200 mL of 1 mol/L ethanol and acetic acid in acetonitrile for esterification or 1 mol/L ethyl acetate and water in acetonitrile for hydrolysis at 20, 30, and 40 °C. The obtained experimental result is a justification of the theory presented previously (Constales et al., 2012).