Ammonium Formate Solution Research Articles

Study of the impurity profile and characteristic fragmentation of Δ3 -isomers in cephapirin sodium using dual liquid chromatography coupled with ion trap/time-of-flight mass spectrometry.

According to the requirements of the International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH), the structures of impurities in pharmaceutical products present at over 0.1% need to be confirmed. Therefore, the aim of this study is to separate and identify the impurities in cephapirin sodium drug substances, so as to guide the industry to improve the production process and storage conditions and reduce the amount of impurities in the product. In the first chromatography dimension, a Boston Green ODS (4.6 mm × 250 mm, 5 μm) column was used, with a mobile phase composed of 0.05 M sodium dihydrogen phosphate aqueous solution and acetonitrile. In the second dimension, the column was a Shimadzu Shim-pack GISS C18 (50 mm × 2.1 mm, 1.9 μm), using 10 mM ammonium formate solution and methanol as the mobile phase. The fragmentation behavior of cephapirin and its impurities and isomers was studied and the structures of impurities were deduced based on the MSn data. For six unknown impurities tentative structures were proposed. The degradation behavior of cephapirin sodium was also studied. Impurities 1 to 11 were found in commercial cephapirin sodium samples, indicating that cephapirin sodium should be stored in closed containers. The contradiction between the non-volatile mobile phase and mass spectrometry was solved by means of multiple heart-cutting approaches and an on-line desalting technique. Twelve impurities and isomers were separated and characterized. These results could be used to improve the methods described in pharmacopoeias for the quality control of cephapirin sodium.

Simultaneous Determination and Validation of 5F-ADBICA and 5F-NPB-22 in Whole Blood and Urine by LC/MS–MS

Synthetic cannabinoids (SCs) are the most rapidly growing class of recreational designer drugs. The rapid growth in popularity of SC use among teens and adults is of serious in our country as all of the world. These products are saturated in various plants crumb in order to make herbal appearence. They are not for human consumption and also their chemical structures are rapidly evolving. They are known as “Bonsai” in Turkey. 5F-ADBICA and 5F-NPB-22 are the two most commonly detected compounds in seized herbal products by police forces. The aim of this study was to determine and validate 5F-ADBICA and 5F-NPB-22 in whole blood and urine by LC/MS–MS. No method exists in the literature for the simultaneous determination of these new-generation SCs. 250 µL blank blood was transferred to 16 × 100-mm test tubes. Extraction was performed with 2 mL acetonitrile:ethyl acetate (25:75). The tubes were capped and rotated for 15 min. The samples were then centrifuged for 10 min at 3500 rpm. The organic layer was transferred to other tube and was evaporated to dryness at 45 °C under a stream of nitrogen. 0.5 mL of urine samples, 1.5 mL ice-cold acetonitrile and 0.5 mL of a 10 M ammonium formate solution were added. The mixture was shaken, centrifuged, and 1 mL of the organic layer was transferred into a separate vial and evaporated to dryness under a stream of nitrogen. The dried extracts were reconstituted with mobile phase A. The chromatographic separation was performed with a pentafluorophenylpropyl (PFPP) column (Allure 50 × 2.150 mm i.d., 5 μm, Restek, Bellefonte, PA, USA) using a gradient binary with 10 mM ammonium formate (A) in ultrapure water and methanol (B). The run time is 20 min. The method was validated in terms of limits of detection (LODs) (0.01–0.12 ng/mL) and quantification (LOQs) (0.03–0.36 ng/mL), extraction recovery (ER) (77.4–97.3%), matrix effect (ME) (63.3–83.6%), linearity, intra- and interday precision (CV ˂ 20%) and carryover. A simple, cost-effective, and accurate LC/MS–MS method has been developed for the simultaneous quantification of 5F-ADBICA and 5F-NPB-22 in whole blood and urine. The newly developed analytical methods allow the analysis of new-generation synthetic cannabinoids.

Characterization of four unknown impurities in azithromycin and erythromycin imino ether using two-dimensional liquid chromatography coupled to high-resolution quadrupole time-of-flight mass spectrometry and nuclear magnetic resonance.

A simple and sensitive method was developed for the separation and characterization of four unknown impurities in azithromycin and erythromycin imino ether using two-dimensional liquid chromatography coupled to high-resolution quadrupole time-of-flight mass spectrometry (2D LC/QTOFMS) with positive and negative electrospray ionization. The chromatographic separation in the first dimension was performed with a Waters Xbridge RP18 column in gradient mode using binary mobile phase: (A) phosphate buffer (pH 8.2)-acetonitrile (47:53, v/v) and (B) water-acetonitrile (90:10, v/v). In the second dimension, the chromatographic separation was performed using a Shimadzu Shim-pack GISS C18 column with volatile mobile phases: (A) ammonium formate solution (10 mM) and (B) methanol. The molecular formulae and structures of the four impurities were deduced based on the LC/MS/MS data, and further confirmed using 1 H NMR, 13 C NMR, 1 H-1 H COSY, HSQC and HMBC NMR spectra after semi-preparative isolation of impurities. In addition, the mechanism for the formation of the impurities was also proposed. The contradiction between the non-volatile salt mobile phase and mass spectrometry was solved by means of a multiple heart-cutting 2D LC approach and on-line desalination technology. Four impurities were separated and characterized. These results could further improve the method of official monographs in pharmacopoeias and guides to improve the process of reducing impurity content.

Selective deposition of p-type Cu2O or conductive Cu thin film at 180∘C in air on a quartz glass substrate: Development of an aqueous spray solution using two-compartment electrolysis system

A conductive Cu thin film with a thickness of 170[Formula: see text]nm, electrical resistivity of 8.9(2) [Formula: see text][Formula: see text]cm and adhesion strength of 12(7) MPa was fabricated at 180∘C in air. The spray solutions were prepared by electrolyzing Cu electrodes in an aqueous solution of ammonium formate, and then by adding ethylenediamine-N, N, N[Formula: see text], N[Formula: see text]-tetraacetic acid (EDTA). The surface morphology image of resultant Cu thin film, observed by a field emission scanning electron microscope, revealed Cu grains with particle sizes of ca. [Formula: see text][Formula: see text]nm. It was indicated that the Cu complex containing EDTA ligand in the spray solution plays important roles to (1) provide enough amount of carbon atoms as a reducing agent for phase transition of its coordinated Cu[Formula: see text] to crystalline Cu0 and (2) prevent the product from oxidation under atmospheric O2 during spray coating.

Separation and characterization of unknown impurities in rutin tablets using trap-free two-dimensional liquid chromatography coupled with ion trap/time-of-flight mass spectrometry.

A new high-performance liquid chromatography method was developed for the determination of impurities in rutin tablets to improve on the method of the official monograph in national drug standards. Five impurities in rutin tablets were characterized using trap-free two-dimensional liquid chromatography coupled with ion trap/time-of-flight mass spectrometry (2D-LC/IT-TOFMS) in both positive and negative ion modes of electrospray ionization. In the first dimension, the LC column was a Thermo Acclaim 120™ C18 (4.6 mm × 250 mm, 5 μm), and the mobile phase was composed of 0.1 M sodium dihydrogen phosphate aqueous solution (pH adjusted to 4.4 with phosphoric acid) and acetonitrile (80:20, v/v). In the second dimension, the column was a Shimadzu Shim-pack GISS C18 (50 mm × 2.1 mm, 1.9 μm), and the mobile phase was composed of 10 mM ammonium formate solution and methanol. The structures of five impurities in rutin tablets were deduced based on the MS n data in both positive and negative ion modes, in which two impurities were unknown. Impurity 1, impurity 2 and impurity 3 were proposed as flavonol 3,7-di-O-glycoside, flavonol mono-O-triglycoside and quercetin 3-O-glycoside, respectively, and impurity 4 and impurity 5 were proposed as kaempferol 3-O-rhamnosylglucoside and isorhamnetin 3-O-rhamnosylglucoside, respectively. The method established in this study was simple and reliable for the routine quality control of rutin tablets. The contradiction between non-volatile salt mobile phase and mass spectrometry was solved by means of a multiple heart-cutting 2D-LC approach and on-line desalination technology. Five impurities were separated and characterized. These results provide a scientific basis for further improving the national drug standard of rutin tablets.

Rapid Determination of 13 Sedative Substances and Their Metabolites in Blood by LC-MS/MS.

Objective To establish an analysis method for simultaneous determination of 13 sedative substances and their metabolites in blood by liquid-liquid extraction and liquid chromatography-tandem mass spectrometry （LC-MS/MS） technology and to apply the method to actual cases. Methods The samples were extracted with ethyl acetate after an internal standard was added. The extract was condensed until it was nearly dry and then its residues were dissolved with methanol, filtered through 0.22 μm filter and finally determined. The 13 sedative substances and their metabolites were separated through the C18 chromatographic column, then gradient elution was performed on them with methanol and 20 mmol/L ammonium formate （containing 0.1% formic acid） solution. After that, they were determined in the electrospray positive ion mode and quantified by internal standard method. Results The 13 sedative substances and their metabolites in blood showed good linearity in the range of 5-200 μg/L with correlation coefficients ranging from 0.990 3 to 0.999 8. The detection limits were 0.1-1.0 μg/L. Recovery rates of sedative substances were in the range of 71.2%-93.4% when solutions with concentrations of 10, 50 and 200 μg/L were added. The deviations of intra-day and inter-day relative standard deviations （RSD） were not more than 8.6%. Accuracies （bias） were within ±9.8%. Conclusion This method is rapid, simple, effective and sensitive, and can be applied to analysis of 13 sedative substances and their metabolites in blood in forensic toxicology.

Analytical approaches for the determination of deferiprone and its iron (III) complex: Investigation of binding affinity based on liquid chromatography-mass spectrometry (LC-ESI/MS) and capillary electrophoresis-frontal analysis (CE/FA)

Two rapid and highly sensitive separation techniques were developed for the determination of free and metal-bound deferiprone for binding affinity studies. The chromatographic method was carried out on a high-resolution monolithic column using gradient elution with a mobile phase consisting of ammonium formate solution (pH 7.4; 10 mM), H2O, and methanol pumped at a flow rate of 1.0 mL min−1. Identification was performed on single quadrupole mass spectrometer using electrospray ionization interface at positive polarity. The assay was found to be linear in the concentration range of 0.5–17.5 mM with regression coefficient of r2 > 0.999. The electrophoretic method has been developed to achieve sufficient separation between free drug and the complex using capillary length of 48.5/8.5 cm (Ltot/Leff), 10 kV of applied voltage in negative mode, and large plug of sample injected hydrodynamicallyat10 mbar for 50 s. The linear range of the drug concentrations was 40–240 μM, with regression coefficient r2 > 0.998. The binding parameters have been estimated for both methods in terms of binding constant (LogKa) and number of binding sites (ni). The values LogKa and ni8.3 ± 0.17 and 3.4 ± 0.65 respectively were obtained from the data of liquid chromatography while, the data obtained from capillary electrophoresis resulted in LogKa10.4 ± 0.12 and ni 3.0 ± 0.10.

A reliable HPLC-DAD method for simultaneous determination of related substances in TBI-166 active pharmaceutical ingredient

A sensitive, stability-indicating reversed-phase high-performance liquid chromatography with diode array detection (HPLC–DAD) method has been developed for the determination of TBI-166 and its 10 kinds of related impurities. Chromatographic separation was achieved on a Kromasil ODS column (250 mm × 4.6 mm, 5 μm), with a gradient elution of the mobile phase system consisting of acetonitrile and 1% ammonium formate solution (with 0.2% formic acid). The flow rate was 1.0 mL/min, and the detection wavelength was set at 251 nm. The method was validated according to the International Conference on Harmonization (ICH) guidelines with respect to selectivity, linearity, limits, accuracy, precision, and robustness. The calibration curves were linear from LOQ to 150% of the specification limit of impurity with correlation coefficients not less than 0.999. The limits of quantitation were between 0.123 and 0.257 μg/mL. Accuracy for the related substances was estimated by the recovery ranged from 94.6% to 111.2%. The method was proved to be reliable for the determination of related substances in TBI-166 bulk drug, which is essential and important in the quality control.

Chiral separation of aliphatic primary amino alcohols as o-phthaldialdehyde/mercaptoethanol derivatives on polysaccharide-based chiral stationary phases.

A sensitive chiral high performance liquid chromatography (HPLC) method for the determination of aliphatic primary amino alcohol isomers with o-phthaldialdehyde/mercaptoethanol precolumn derivatization has been developed and validated. Seven chiral columns were tested in a reversed phase mode. Excellent enantioseparation with the resolution more than 2.0 was achieved on Chiralcel OJ-3R. The effect of various chromatographic conditions including column temperature, acetonitrile content in the mobile phase, buffer pH, buffer concentration, and buffer type in the mobile phase on the retention and the selectivity was investigated. The final mobile phase consisted of binary mixture of 20mM ammonium formate solution with acetonitrile (75:25; v/v). The analyses were performed at mobile phase flow rate of 1.0mL/min and the column temperature of 40°C. The fluorescence detection was performed at excitation wavelength of 345nm and emission wavelength of 450nm. The developed method was fully validated in terms of linearity, sensitivity, accuracy, precision, intermediate precision, and selectivity according to International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use guidelines using internal normalization procedure. The proposed chiral method was proved to be highly sensitive, simple, and rapid and was successfully applied to the determination of D-Valinol content in commercially available samples of L-Valinol.

DEVELOPMENT AND VALIDATION OF A RP-HPLC METHOD FOR ESTIMATION OF TELMISARTAN IN HUMAN PLASMA

Objective: The present study was aimed to develop a rapid, specific and sensitive method based on high performance liquid chromatographic method was developed for the determination of telmisartan using indapamide as an internal standard.Methods: The utilization of single step protein precipitation method using methanol as a precipitating agent becomes suitable for analysis of a large number of samples. The developed method was validated as per US-FDA guidelines for telmisartan in human plasma.Result: An isocratic separation was achieved using Hibar C18 (250 x 4.6 mm, 5 μm) column using 10 mmol ammonium formate solution (pH 4.0)–methanol (70:30, v/v) as the mobile phase. Detection was carried out at 275 nm. The method was validated over the range of 0.1–1.5 µg/ml in human plasma with a regression analysis of 0.996. The percentage recovery of the present method was found to be 94.0–99.2 %.Conclusion: The developed analytical method was found to be rapid, single step, plasma preparation coupled with the simple high-performance liquid chromatography coupled with UV detection (HPLC–UV) isocratic chromatographic apparatus makes the method cost-effective and suitable for analysis of a large number of samples.

Rapid determination of bongkrekic acid in Liushenqu by ultra performance liquid chromatography-tandem mass spectrometry

A method for the rapid determination of biotoxin (bongkrekic acid) in the Liushenqu was established using ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The samples were extracted with methanol by ultrasonication, then the pH was adjusted to 8 using ammonia. After filtration, the extract was purified using an Oasis Max strong anion exchange resin column. The Waters HSS T3 column (100 mm×2.1 mm, 1.8 μm) was used for the UPLC-MS/MS analysis. The mobile phase was acetonitrile-10 mmol/L ammonium formate solution (containing 0.1% (v/v) formic acid). MS analysis was performed using an electrospray ionization (ESI) source in the negative and multiple reaction monitoring (MRM) modes. Under the optimum conditions, the linear range of bongkrekic acid was 0.5-100 μg/L (correlations coefficient (R2)>0.99). The recoveries of the bongkrekic acid were 80.6%-85.3%. The intra-day and inter-day relative standard deviations (RSDs) were in the range of 4.2%-6.8% and 8.2%-13.2%, respectively. The limit of detection (LOD) and limit of quantification (LOQ) were 0.4 μg/kg and 1.2 μg/kg, respectively. The results showed that bongkrekic acid residues were detected in Liushenqu, thereby confirming the supporting role of our method for the risk monitoring of biotoxins in health foods and Chinese herbal medicines. This method is simple, easy, sensitive, and suitable for the determination of the bongkrekic acid residues in Liushenqu.

Simultaneous determination of the quaternary ammonium pesticides paraquat, diquat, chlormequat, and mepiquat in barley and wheat using a modified quick polar pesticides method, diluted standard addition calibration and hydrophilic interaction liquid chromatography coupled to tandem mass spectrometry

In this study, a modified Quick Polar Pesticides (QuPPe) method, optimized by a central composite design, was developed to determine quaternary ammonium pesticides (QUATs) residues in barley and wheat by ultra-high-performance liquid chromatographic tandem mass spectrometry (UHPLC-MS/MS) using a hydrophilic interaction chromatography (HILIC) column. Considering the high polarity of these compounds, special conditions of sample preparation and analysis are required. Different mobile phases, extraction procedure and clean-up were evaluated. An isocratic elution with aqueous solution of ammonium formate 60 mmol L−1 (pH 3.7) and acetonitrile, 40:60 (v/v), was selected. Water and acidified methanol as extraction solvent, without heating, and a clean-up with dichloromethane, chitosan and acetonitrile presented good results. The validated method presented satisfactory selectivity, linearity, matrix effect, trueness and precision, providing recoveries from 93 to 110% with RSD < 13% for barley, and 70 to 115% with RSD < 18% for wheat. The complexity of these matrices requires the calibration in matrix and the diluted standard addition calibration (DSAC) procedure has been shown to be an excellent option to compensate for the matrix effect and the losses of the analytes in the extraction. Real samples of barley and wheat were analyzed and 60% presented concentrations of paraquat above the maximum limits allowed by the European Union. The modified QuPPe method combined with DSAC and HILIC-UHPLC-MS/MS demonstrated to be an effective approach to determine QUATs in barley and wheat, and is a good alternative for routine analysis. The use of the biosorbent chitosan is effective, low cost and more ecological when compared to others conventional sorbents.

HPLC Determination of Glyphosate, Aminomethylphosphonic Acid, and Glufosinate Using a Hypercarb Porous Graphite Adsorbent

A method for the HPLC determination of glyphosate, aminomethylphosphonic acid, and glufosinate using the gradient separation of analytes on a Hypercarb porous graphitized carbon adsorbent and an aqueous solution of ammonium formate and ammonia as a mobile phase is proposed. Analytes are detected using quadrupole and three-quadrupole mass spectrometers. In order to increase the retention of the analytes, the chromatographic column is washed with water before the injection of a sample solution. This procedure results in a three- to fourfold increase in the retention factors of the analytes in comparison with the analogues described in the publications.

Development and validation of two LC-MS/MS methods to assay urinary tylerdipine hydrochloride and its metabolites in healthy Chinese subjects

For quantitative assaying tylerdipine hydrochloride, and its two primary metabolites (M2 and M4) in human urine, two sensitive and accurate LC-MS/MS methods were firstly developed and validated, where multiple reaction monitoring (MRM) was applied under positive electrospray ionization mode for tylerdipine and negative electrospray ionization mode for M2/M4, respectively. Urinary proteins were precipitated using acetonitrile, and deuterated isotopes of tylerdipine and M4 ([D5]‑tylerdipine and [D6]-M4) were used as internal standards. Triton X-100, a good surfactant, was used to prevent the adsorption. An Agilent Poroshell 120 column was employed for chromatographic separation of the analytes with the mobile phases of 2 mM ammonium formate solution (containing 0.1% formic acid) and acetonitrile (45:55 for tylerdipine and 75:25 for the M2/M4, v/v). Flow rate was 0.3 mL/min. Calibration curves for tylerdipine, M2 and M4 in urine were linear over the ranges of 0.02–10 ng/mL, 2–1500 ng/mL and 0.5–200 ng/mL, respectively. The precision, accuracy, specificity and stability of two methods all evaluated and achieved the acceptable criteria. The LC-MS/MS methods were successfully applied to assay urinary excretion of tylerdipine and the metabolites in healthy Chinese subjects who orally received a single dose of 20 mg tylerdipine tablet. Generally, the urinary excretion of the two primary metabolites accounted for 11.7% of the total dose of tylerdipine in healthy Chinese subjects, while little tylerdipine was recovered in urine.

Separation and characterization of allergenic polymerized impurities from cephalosporin for injection by trap free two-dimensional high performance size exclusion chromatography × reversed phase liquid chromatography coupled with ion trap time-of-flight mass spectrometry

As requested by regulatory authorities, polymerized impurities are an important issue of quality control. In this study, we presented the utilization of a trap-free two-dimensional chromatography, which was consisted by a high performance size exclusion chromatography (HPSEC) and a reversed-phase liquid chromatography (RP-LC) coupled to ion trap time-of-flight mass spectrometry with positive mode of electrospray ionization, to separate and characterize ten allergenic impurities in ceftazidime for injection, cefazolin sodium for injection, cefoperazone sodium and sulbactam sodium for injection and cefamandole nafate for injection. An effective method for characterizing the polymerized impurities in β-lactam antibiotics was established on the basis of column-switching technique which effectively combined the advantages of HPSEC and the ability of RP-HPLC to identify the special impurities. In the first dimension, the column was the Xtimate SEC-120 analytical column (7.8 mm × 30 cm, 5 μm) and the flow rate was 1.0 mL min−1 with gradient elution using 0.005 mol L−1 phosphate buffer solution at pH 7.0 and acetonitrile as mobile phase. In the second dimension, the analytical column was ZORBAX SB-C18 (4.6 × 150 mm, 3.5 μm) using ammonium formate solution (10 mM) and ammonium formate (8 mM) in [acetonitrile-water (4:1, v/v)] solution as mobile phase at a flow rate of 0.4 mL min−1. Eluent associate with each peak separated in the first dimension was trapped by a 20 μL quantitative loop and then transferred (via a six-port valve) into the second dimension system with volatile mobile phase. Through the multiple heart-cutting 2D-LC approach and online desalting technique, the problem of incompatibility between non-volatile mobile phase and mass spectrometry was solved completely. The fragmentation behaviors of ten allergenic impurities were studied. The structures of ten allergenic impurities in cephalosporin drug substance were deduced based on the HPLC–MSn data, in which four impurities were polymerized impurities. The forming factors of polymerized impurity in cephalosporins were also studied.

Determination of 63 compounds illegally added in tea, substitute tea and beverage foods by ultra-high performance liquid chromatography-tandem mass spectrometry

A method based on ultra-high-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was developed for the simultaneous determination of 63 compounds illegally added in tea, substitute tea, and beverage products. The samples were extracted by ultrasonic extraction using methanol, and the analytes were separated on the Thermo Acclaim RSLC C18 chromatographic column (100 mm×2.1 mm, 2.2 μm) by gradient elution using 5 mmol/L ammonium formate solution containing 0.1% (v/v) formic acid and 0.1% (v/v) formic acid acetonitrile as the mobile phase. The electrospray ion source was operated in the positive ion mode using the dynamic multi-reaction monitoring (dMRM) method, and the results were quantified by the external standard method. The correlation coefficients (R2) of the linear calibration curves were greater than 0.99 in the corresponding mass concentration ranges, and the limits of quantification (LOQs) for the analytes were 0.10-2.50 mg/kg. The average recoveries at three spiked levels ranged from 62.4% to 129.4%. The RSDs of the injection precision and the repeatability of samples were in the range 0.3%-9.6% (n=6). Thus, the proposed method is simple, rapid, accurate, reliable, and applicable for the detection of the illegal addition of antipyretic and analgesic affect compounds in tea, substitute tea and beverage food.

Chromatomass-spectrometric identification of electrochemical transformation products of kresoxim-methyl in solutions

The products of electrochemical transformations of organic compounds are similar in many aspects to the products of their chemical reactions. The information on the nature and the formation mechanisms of such products is important for pesticides because this allows characterizing the mechanisms of their decomposition in the soil, aquatic environments and plants. A set of electrochemical processes involving such pesticide of the strobilurin class as kresoxim-methyl [methyl ( E )-2- methoxyimino-2-(2-( o -tolyloxymethyl)­phenyl)acetate] in its solution in aqueous organic medium [mixture of an aqueous solution of ammonium formate (pH 7.4) and acetonitrile (3: 1 v/v)] with the concentration of 100 mg/mL, and the results of chromatomass-spectrometric identification (HPLC-ESI-MS-MS) of the formed products were considered. It has been revealed that hydrolysis products predominate in the mixture of the kresoxim-methyl electrolysis products, including corresponding carboxylic acid and such demethylation products as oximes. Kresoxim-methyl oxidation products, such as the corresponding hydroxamic acid, have been detected in small amounts only. At the same time, the reduction products – amines, most likely formed from oximes, – have been identified. Keeping in mind the restricted information content of the HPLC-ESI-MS-MS method for establishing the structure of the previously uncharacterized analytes, the method of comparing the relative intensities of the peaks of reaction mixture constituents detected in the positive and negative ionization modes was used in identification of the products of electrochemical transformations. The signals of the protonated amines predominate in the first case, while in the second case the compounds containing carboxyl groups ionized at pH 7.4 are detected. Keywords: Pesticides, kresoxim-methyl, electrochemical processes, hydrolysis, oxidation and reduction, identification of products DOI: http://dx.doi.org/10.15826/analitika.2018.22.3.009 (Russian) Tatiana I. Pushkareva, Sergey S. Ermakov, Igor G. Zenkevich, St. Petersburg State University, Universitetskii prosp., 26, St. Petersburg, 198504, Russian Federation

Moxidectin residues in lamb tissues: Development and validation of analytical method by UHPLC-MS/MS.

The development and validation of a throughput method for the quantitation of moxidectin residues in lamb target tissues (muscle, kidney, liver and fat) was conducted using ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). To achieve higher recovery of the analyte from the matrices, a modified QuEChERS method was used for sample preparation. The chromatographic separation was achieved using a Zorbax Eclipse Plus C18 RRHD column with a mobile phase comprising 5mM ammonium formate solution +0.1% formic acid (A) and acetonitrile +0.1% formic acid (B) in a linear gradient program. Method validation was performed based on the Commission Decision 2002/657/EC and VICH GL49. To quantify the analyte, matrix-matched analytical curves were constructed with spiked blank tissues, with a limit of quantitation of 5ngg-1 and limit of detection of 1.5ngg-1 for all matrices. The linearity, decision limit, detection capability accuracy, and inter- and intra-day repeatability of the method are reported. The method was successfully applied to incurred lamb tissue samples (muscle, liver, kidney and fat) in a concentration range from 5 to 200μgkg-1, which demonstrated its suitability for monitoring moxidectin residues in lamb tissues in health surveillance programs, as well as for pharmacokinetics and residue depletion studies.

Simultaneous quantification of volitinib and gefitinib in rat plasma by HPLC-MS/MS for application to a pharmacokinetic study in rats.

A rapid, simple, and accurate procedure was developed and validated for the simultaneous quantification of two anticancer agents, volitinib and gefitinib in rat plasma by high-performance liquid chromatography with tandem mass spectrometry. The samples were separated by gradient elution from a cyano column within five minutes, using 0.1% formic acid in acetonitrile and 10mM ammonium formate solution (pH 3.0) as mobile phase. When plasma samples were deproteinated by adding methanol, the analytes in the extract were detected in the positive ionization mode with the tracer ion mass of 346.1 → 145.1 for volitinib and 446.8 → 128.1 for gefitinib. The assay was determined to be valid in the concentration ranges of 2 to 1000ng/mL for volitinib, and of 1 to 500ng/mL for gefitinib. Intra- and interday accuracies ranged from 88.0 to 104.7% for volitinib and from 90.3 to 101%, for gefitinib. The precision of the assay ranged from 2.1 to 9.71% for volitinib and 2.31 to 12.1% for gefitinib. This method was successfully applied to a pharmacokinetic study of volitinib and gefitinib after the administration of an intravenous or oral dose, indicating that the developed assay can be used to simultaneously determine the concentrations of volitinib and gefitinib in rat plasma.

Separation and characterization of unknown impurities in cefonicid sodium by trap-free two-dimensional liquid chromatography combined with ion trap time-of-flight mass spectrometry.

Seven unknown antibiotic impurities in cefonicid sodium were separated and characterized by a trap-free two-dimensional liquid chromatography coupled to high-resolution ion-trap time-of-flight mass spectrometry (2D-LC/IT-TOF MS) using both positive and negative modes of electrospray ionization. Trap-free 2D-LC and an online demineralization technique made it possible to characterize cefonicid sodium under the conditions of the official standard, and the TIC chromatogram obtained by LC/MS was in conformity with the LC chromatogram obtained by the official analytical method in the peak sequence of impurities. In the first dimension, the column was a GRACE Alltima C18 (250mm×4.6mm, 5μm), and the gradient elution used 0.02mol·L-1 ammonium dihydrogen phosphate solution and methanol as mobile phase. In the second dimension, the analytical column was a Shimadzu Shim-pack GISS C18 (50mm×2.1mm, 1.9μm) with 10mmol·L-1 ammonium formate solution and methanol as mobile phase. Full scan LC/MS was first executed to obtain the exact m/z values of the molecules. Then LC/MS2 and LC-MS3 experiments were performed on the compounds of interest. The structures of seven unknown degradation products in cefonicid sodium were deduced based on the high-resolution MSn data using both positive and negative mode. The problem of incompatibility between the non-volatile salt mobile phase and mass spectrometry was solved completely by multidimensional heart-cutting approaches and an online demineralization technique, which is worthy of widespread use and application for the advantages of stability and repeatability.