Liquid Chromatography-single Quadrupole Mass Research Articles

Separating the wheat from the chaff: Observations on the analysis of lysergamides LSD, MIPLA, and LAMPA.

Lysergic acid diethylamide (LSD) is a potent psychoactive substance that has attracted great interest in clinical research. As the pharmacological exploration of LSD analogs continues to grow, some of those analogs have appeared on the street market. Given that LSD analogs are uncontrolled in many jurisdictions, it is important that these analogs be differentiated from LSD. This report presents the analysis of blotters found to contain the N-methyl-N-isopropyl isomer of LSD (MIPLA), and techniques to differentiate it from LSD and the N-methyl-N-propyl isomer (LAMPA) under routine conditions. Gas chromatography (GC)-solid phase infrared spectroscopy was particularly helpful. GC-electron ionization-tandem mass spectrometry of the m/z 72 iminium ion also provided sufficient information to distinguish the three isomers on mass spectral grounds alone, where chromatographic separation proved challenging. Derivatization with 2,2,2-trifluoro-N,N-bis (trimethylsilyl)acetamide (BSTFA) also led to improved GC separation. Liquid chromatography single quadrupole mass spectrometry (LC-Q-MS) and in-source collision-induced dissociation allowed for the differentiation between MIPLA and LAMPA based on distinct m/z 239 ion ratios when co-eluting. An alternative LC-MS/MS method improved the separation between all three lysergamides, but LSD was found to co-elute with iso-LSD. However, a comparison of ion ratios recorded for transitions at m/z 324.2> 223.2 and m/z 324.2> 208.2 facilitated their differentiation. The analysis of two blotters by LC-Q-MS revealed the presence of 180 and 186 μg MIPLA per blotter. These procedures may be used to avoid inadvertent misidentification of MIPLA or LAMPA as LSD.

Liquid Chromatography Single Quadrupole Mass Spectrometry (LC/SQ MS) Analysis Reveals Presence of Novel Antineoplastic Metabolites in Ethanolic Extracts of Fruits and Leaves of Annona muricata

Pan African University, Busitema University, Uganda Natural Chemotherapeutics Research Institute, Uganda Directorate of Water Resources Management

Melatonin in Plants and Plant Culture Systems: Variability, Stability and Efficient Quantification.

Despite growing evidence of the importance of melatonin and serotonin in the plant life, there is still much debate over the stability of melatonin, with extraction and analysis methods varying greatly from lab to lab with respect to time, temperature, light levels, extraction solvents, and mechanical disruption. The variability in methodology has created conflicting results that confound the comparison of studies to determine the role of melatonin in plant physiology. We here describe a fully validated method for the quantification of melatonin, serotonin and their biosynthetic precursors: tryptophan, tryptamine and N-acetylserotonin by liquid chromatography single quadrupole mass spectrometry (LC-MS) in diverse plant species and tissues. This method can be performed on a simple and inexpensive platform, and is both rapid and simple to implement. The method has excellent reproducibility and acceptable sensitivity with percent relative standard deviation (%RSD) in all matrices between 1 and 10% and recovery values of 82–113% for all analytes. Instrument detection limits were 24.4 ng/mL, 6.10 ng/mL, 1.52 ng/mL, 6.10 ng/mL, and 95.3 pg/mL, for serotonin, tryptophan, tryptamine, N-acetylserotonin and melatonin respectively. Method detection limits were 1.62 μg/g, 0.407 μg/g, 0.101 μg/g, 0.407 μg/g, and 6.17 ng/g respectively. The optimized method was then utilized to examine the issue of variable stability of melatonin in plant tissue culture systems. Media composition (Murashige and Skoog, Driver and Kuniyuki walnut or Lloyd and McCown's woody plant medium) and light (16 h photoperiod or dark) were found to have no effect on melatonin or serotonin content. A Youden trial suggested temperature as a major factor leading to degradation of melatonin. Both melatonin and serotonin appeared to be stable across the first 10 days in media, melatonin losses reached a mean minimum degradation at 28 days of approximately 90%; serotonin reached a mean minimum value of approximately 60% at 28 days. These results suggest that melatonin and serotonin show considerable stability in plant systems and these indoleamines and related compounds can be used for investigations that span over 3 weeks.

Influence of the presence of natural monosaccharides in the quantification of α-dicarbonyl compounds in high content sugar samples. A comparative study by ultra-high performance liquid chromatography–single quadrupole mass spectrometry using different derivatization reactions

The goal of this work is to evaluate the formation of side α-dicarbonyl compounds in high content sugar samples. These compounds may be originated from fructose and glucose, during different derivatization reactions. The formation of D-glucosone, 3-deoxyglucosone, glyoxal, and methylglyoxal, using three derivatization agents (5,6-diamino-2,4-hydroxypyrimidine, 2,4,5-triamine-6-hydroxypyrimidine, and o-phenylenediamine), and ultra-high pressure liquid chromatography in combination with MS detection, has been assessed in the presence of different levels of monosaccharides. 2,4,5-triamine-6-hydroxy-pyrimidine appears to be the most suitable for the analysis of α-dicarbonyl compounds, in this kind of food samples, and was selected as optimum reagent for the quantification of these compounds. The validation of the method was performed through the establishment of external standard calibration curves and analytical figures of merit, and it showed good linearity over a wide concentration range (r2>0.99), and limits of detection and quantification lower than 42μgL−1 and 142μgL−1, respectively. The validated method has been successfully applied to the determination of the target compounds in honey samples. The intraday and interday assay variability in the analysis of real samples was below 2.3 and 5.7%, respectively, for all analytes.

Quantitative determination of telavancin in pregnant baboon plasma by solid-phase extraction and LC–ESI–MS

The increasing incidence and severity of methicillin- and vancomycin-resistant infections during pregnancy prompted further development of telavancin. The understanding of the pharmacokinetics of telavancin during pregnancy is critical to optimize dosing. Due to ethical and safety concerns the study is conducted on the pregnant baboons. A method using solid-phase extraction coupled with liquid chromatography–single quadrupole mass spectrometry for the quantitative determination of telavancin in baboon plasma samples was developed and validated. Teicoplanin was used as an internal standard. Telavancin was extracted from baboon plasma samples by using Waters Oasis® MAX 96-Well SPE plate and achieved extraction recovery was >66% with variation <12%. Telavancin was separated on Waters Symmetry C18 column with gradient elution. Two SIM channels were monitored at m/z 823 and m/z 586 to achieve quantification with simultaneous confirmation of telavancin identification in baboon plasma samples. The linearity was assessed in the range of 0.188μg/mL to75.0μg/mL, with a correlation coefficient of 0.998. The relative standard deviation of this method was <11% for within- and between-run assays, and the accuracy ranged between 96% and 114%.

Development and validation of a liquid chromatography–mass spectrometry assay for polymyxin B in bacterial growth media

There is increasing interest in the optimization of polymyxin B dosing regimens to treat infections caused by multidrug-resistant Gram-negative bacteria. We aimed to develop and validate a liquid chromatography–single quadrupole mass spectrometry (LC–MS) method to quantify polymyxin B in two growth media commonly used in in vitro pharmacodynamic studies, cation-adjusted Mueller-Hinton and tryptone soya broth. Samples were pre-treated with sodium hydroxide (1.0M) and formic acid in acetonitrile (1:100, v/v) before analysis. The summed peak areas of polymyxin B1 and B2 relative to the summed peak areas of colistin A and B (internal standard) were used to quantify polymyxin B. Quality control samples were prepared and analyzed to assess the intra- and inter-day accuracy and precision. The robustness of the assay in the presence of bacteria and commonly co-administered antibiotics (rifampicin, doripenem, imipenem, cefepime and tigecycline) was also examined. Chromatographic separation was achieved with retention times of approximately 9.7min for polymyxin B2 and 10.4min for polymyxin B1. Calibration curves were linear between 0.103 and 6.60mg/L. Accuracy (% relative error) and precision (% coefficient of variation), pooled for all assay days and matrices (n=84), were −6.85% (8.17%) at 0.248mg/L, 1.73% (6.15%) at 2.48mg/L and 1.54% (5.49%) at 4.95mg/L, and within acceptable ranges at all concentrations examined. Further, the presence of high bacterial concentrations or of commonly co-administered antibiotics in the samples did not affect the assay. The accuracy, precision and cost-efficiency of the assay make it ideally suited to quantifying polymyxin B in samples from in vitro pharmacodynamic models.

Fast screening of perfluorooctane sulfonate in water using vortex-assisted liquid–liquid microextraction coupled to liquid chromatography–mass spectrometry

Fast screening of trace amounts of the perfluorooctane sulfonate anion (PFOS) in water samples was performed following a simple, fast and efficient sample preparation procedure based on vortex-assisted liquid–liquid microextraction (VALLME) prior to liquid chromatography–mass spectrometry. VALLME initially uses vortex agitation, a mild emulsification procedure to disperse microvolumes of octanol, a low density extractant solvent, in the aqueous sample. Microextraction under equilibrium conditions is thus achieved within few minutes. Subsequently, centrifugation separates the two phases and restores the initial microdrop shape of the octanol acceptor phase, which can be collected and used for liquid chromatography–single quadrupole mass spectrometry analysis. Several experimental parameters were controlled and the optimum conditions found were: 50 μL of octanol as the extractant phase; 20 mL aqueous donor samples (pH = 2); a 2 min vortex extraction time with the vortex agitator set at a 2500 rpm rotational speed; no ionic strength adjustment. Centrifugation for 2 min at 3500 rpm yielded separation of the two phases throughout this study. Enhanced extraction efficiencies were observed at low pH which was likely due to enhanced electrostatic interaction between the negatively PFOS molecules and the positively charged octanol/water interface. The effect of pH was reduced in the presence of sodium chloride, likely due to electrical double layer compression. The linear response range for PFOS was from 5 to 500 ng L −1 (coefficient of determination, r 2, 0.997) and the relative standard deviation for aqueous solutions containing 10 and 500 ng L −1 PFOS were 7.4% and 6.5%, respectively. The limit of detection was 1.6 ng L −1 with an enrichment factor of approximately 250. Analysis of spiked tap, river and well water samples revealed that matrix did not affect extraction.

Inter-laboratory comparison of an analytical method for the determination of the feed additive semduramicin in poultry feed at authorised level by liquid chromatography single quadrupole mass spectrometry

A collaborative study was carried out according to internationally recognised guidelines in order to establish the performance characteristics of an LC/MS method for the determination of the feed additive semduramicin (SEM) in poultry feed at the level (20–25 mg kg−1) authorised within the European Union. Fifteen laboratories participated in the validation study, and all reported results. The content of SEM in the tested materials, provided as blind duplicates, ranged from 11.5 mg kg−1, which corresponds to half the mean authorised level, to 45.0 mg kg−1, which corresponds to twice the mean authorised level. All the materials were analysed by the participating laboratories using two different quantification approaches: standard addition and external standard calibration. The relative standard deviation of reproducibility (RSDR) for both quantification approaches varied from 8% to 18%, corresponding to HORRAT values ranging from 0.8 to 1.5, which were therefore in all cases below the critical value of 2.0. Consequently, the proposed analytical method and both quantification approaches can be considered to be fully validated and transferable to the control laboratories and applied for the determination of SEM in poultry compound feed at authorised level within the frame of official control. Further steps in the administrative procedure aiming to adopt the method as part of an ISO/CEN standard are currently ongoing.

Determination of semduramicin in poultry feed at authorized level by liquid chromatography single quadrupole mass spectrometry

A novel liquid chromatography single quadrupole mass spectrometry (LC–MS) method for the determination of the feed additive semduramicin, in poultry feed, was developed and single-laboratory validated. This work was selected as a real case scenario to outline the different steps that may be needed whenever the standardisation of an analytical method in the field of methods of analysis for animal feedingstuffs is attempted. In this manuscript the main achievements reached within the development and the single-laboratory validation of an analytical method for the determination of semduramicin in feedingstuffs are detailed. Semduramicin is extracted from the feedingstuffs with acetonitrile. The obtained extracts are then filtered and diluted appropriately. The separation has been carried out in a reverse phase C18 column using isocratic elution with a mixture of methanol and 20 mM ammonium formate solution as mobile phase. The ammonium adducts have been selected for monitoring the coccidiostats signals in the mass spectrometry detector. The method has been successfully validated for the determination of semduramicin concentrations ranging between half of the minimum authorized concentration (10 mg kg −1) to twice of the maximum authorized concentration (50 mg kg −1). A good relative standard deviation for repeatability (RSD r) varying from 2.8 to 3.2% has been obtained whereas the relative standard deviation for intermediate precision (RSD Int.) ranged from 3.7 to 7.3%. The obtained analytical performance characteristics of the method demonstrated its fitness for the purpose, making thus the proposed method suitable to be submitted for the last phase within the standardisation procedure, i.e. the inter-laboratory study.

Synthesis and analytical follow-up of the mineralization of a new fluorosurfactant prototype

Fluorinated surfactants have become essential in numerous technical applications due to their unparalleled effectiveness and efficiency. The environmental persistence of the non-biodegradable perfluorinated alkyl moiety has become a matter of concern. Therefore, it was searched for new molecules with chemically stable fluorinated end groups which can be microbially transformed into labile fluorinated substances.One prototype substance, 10-(trifluoromethoxy)decane-1-sulfonate, has shown biomineralization. Monitoring the formation of metabolites over time elucidated the mechanism of biotransformation. Analysis was performed utilizing liquid chromatography–single quadrupole mass spectrometry (LC–MS) and quadrupole-time of flight tandem mass spectrometry (QqTOF-MS).It was possible to distinguish between two major degradation pathways of the fluorinated alkylsulfonate derivative: (i) a desulfonation and subsequent oxidation and degradation of the alkyl chain being predominant and (ii) an insertion of oxygen with a subsequent cleavage and degradation of the molecule. The utilized trifluoromethoxy-endgroup resulted in instable trifluoromethanol after degradation of the alkyl chain, which led to a high degree of mineralization of the molecule.

Analysis of carbamate and phenylurea pesticide residues in fruit juices by solid-phase microextraction and liquid chromatography–mass spectrometry

A new analysis method to detect carbamates and phenylurea pesticide residues in fruit juices was developed using solid-phase microextraction (SPME) coupled with liquid chromatography–single quadrupole mass spectrometry (LC/MS) and liquid chromatography–quadrupole ion trap mass spectrometry (LC/QIT-MS). The pesticide residues present in watery matrices as fruit juices were extracted using three types of fibers: 50-μm Carbowax/templated resin (CW/TPR), 60-μm poly(dimethylsiloxane)/divinylbenzene (PDMS/DVB) and 85-μm polyacrylate. The different extraction conditions were evaluated choosing as the best parameters 90 min (time), 20 °C (temperature) and 1 ml (volume). After extraction, the desorption (in a static mode) was performed in the specific interface chamber SPME/HPLC, previously filled with 70% methanol and 30% water. The best recoveries, evaluated at two fortification levels (0.2 and 0.5 mg kg −1) in fruit juices, were obtained using PDMS/DVB and CW/TPR fibers, and ranged from 25 to 82% (monolinuron, diuron and diethofencarb), with relative standard deviations (RSDs) from 1 to 17%. All the limits of quantification (LOQs) were in the range of 0.005–0.05 μg ml −1 and, in any case, equal to, or lower than, maximum residue limits (MRLs) established by Italian and Spanish legislations. The mass spectrometry analyses were carried out using an electrospray ionization (ESI) source operating in the positive mode both for single quadrupole and for QIT mass analysers, operating in selected ion monitoring (SIM) and in multiple reaction monitoring (MRM) modes, respectively. The proposed new method can be applied to the determination of selected pesticides in real samples of fruit juices.