Selected Ion Monitoring Detection Research Articles

Solvent-Free Determination of Selected Polycyclic Aromatic Hydrocarbons in Plant Material Used for Food Supplements Preparation: Optimization of a Solid Phase Microextraction Method.

The exploitation of waste and by-products in various applications is becoming a cornerstone of the circular economy. A range of biomasses can be employed to produce food supplements. An example is a particular extract obtained from plant buds (rich in bioactive molecules), which can be easily retrieved from cities' pruning. In order to safely use this material, its possible contamination by organic pollutants needs to be estimated. A green and simple method to detect priority polycyclic aromatic hydrocarbons (PAHs) in bud samples by head space solid phase microextraction coupled to GC-MS was developed. This strategy, optimized through experimental design and response surface methodology, requires a minimal sample pre-treatment and negligible solvent consumption. The final method was found to be accurate and sensitive for PAHs with mass up to 228 Da. For these analytes, satisfactory figures of merit were achieved, with detection limits in the range 1-4 ng g-1, good inter-day precision (relative standard deviation in the range 4-11%), and satisfactory accuracy (88-105%), along with specificity guaranteed by the selected ion monitoring detection. The method was applied to bud samples coming from differently polluted areas, thus helping in estimating the safety of their use for the production of food supplements.

Distinguishing common SARS-CoV2 omicron and recombinant variants with high resolution mass spectrometry.

A selected ion monitoring (SIM) approach combined with high resolution mass spectrometry is employed to identify and distinguish common SARS-CoV2 omicron and recombinant variants in clinical specimens. Mutations within the receptor binding domain (RBD) within the surface spike protein of the virus result in a combination of peptide segments of unique sequence and mass that were monitored to detect BA.2.75 (including CH.1.1) and XBB (including 1.5) variants prevalent in the state's population in early 2023. SIM detection of pairs of peptides unique to each variant were confidently detected and differentiated in 57.3% of the specimens, with a further 10 or 17.5% (for a total of 74.8%) detected based on a single peptide biomarker. The BA.2.75 sub-variant was detected in 18.7%, while recombinant variants XBB and XBB.1.5 were detected in 13.3% and 25.3% of the specimens respectively, consistent with circulating levels in the population characterised by RT-PCR. Virus was detected in 75 SARS-CoV2 positive specimens by mass spectrometry down to the low or mid 104 copy level, with a single false positive and no false negative identified. This article is the first paper to characterise recombinant strains of the SARS-CoV2 virus by this, or any other, MS method.

Test purchase, synthesis, and characterization of 2-methoxydiphenidine (MXP) and differentiation from its meta- and para-substituted isomers.

The structurally diverse nature of the 1,2-diphenylethylamine template provides access to a range of substances for drug discovery work but some have attracted attention as 'research chemicals'. The most recent examples include diphenidine, i.e. 1-(1,2-diphenylethyl)piperidine and 2-methoxydiphenidine, i.e. 1-[1-(2-methoxyphenyl)-2-phenylethyl]piperidine (MXP, methoxyphenidine, 2-MXP) that have been associated with uncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist activity. Analytical challenges encountered during chemical analysis include the presence of positional isomers. Three powdered samples suspected to contain 2-MXP were obtained from three Internet retailers in the United Kingdom and subjected to analytical characterization by gas chromatography (GC) and high performance liquid chromatography (HPLC) coupled to various forms of mass spectrometry (MS). Nuclear magnetic resonance spectroscopy, infrared spectroscopy and thin layer chromatography were also employed. This was supported by the synthesis of all three isomers (2-, 3- and 4-MXP) by two different synthetic routes. The analytical data obtained for the three purchased samples were consistent with the synthesized 2-MXP standard and the differentiation between the isomers was possible. Distinct stability differences were observed for all three isomers during in-source collision-induced dissociation of the protonated molecule when employing detection under HPLC selected-ion monitoring detection, which added to the ability to differentiate between them. Furthermore, the analysis of a 2-MXP tablet by matrix assisted inlet ionization Orbitrap mass spectrometry confirmed that it was possible to detect the protonated molecule of 2-MXP directly from the tablet surface following addition of 3-nitrobenzonitrile as the matrix.

Application of TLC, HPLC and GC methods to the study of amino acid and peptide enantiomers: a review

Amino acids are very important organic compounds in nature. The biological activity of amino acids depends mainly on their stereoisomeric configuration (d- or l-). Thus, the stereochemical analysis of amino acids and peptides is an important aspect of their characterization. Owing to the increasing role of amino acid configuration in biomedical and pharmaceutical studies, numerous analytical methods have been described in the literature. Among a wide range of analytical techniques available for the steroselective separation of different amino acids, which were obtained from plants or biological samples, chromatographic methods such as thin-layer chromatography, high-performance chromatography and also gas chromatography are very useful. This review presents such systems developed for direct stereoisomeric separation and quantitative determination of amino acid and peptide enantiomers with emphasis on selected literature published during two last decades. Almost all aspects, including sample preparation prior chromatographic analysis, stationary phase, solvent system and detection system, are discussed. New possibilities in chiral amino acid analysis have been opened up by the application of mass spectrometry and infrared detection in thin-layer chromatography and mass spectrometry-selected ion monitoring detection system in gas chromatography. A modern trend in high-performance chromatography is two-dimensional chromatography. These innovations have led to decreased development time and increased amino acid resolution and detectability.

Chiral analytical method development and application to pre‐clinical pharmacokinetics of pinocembrin

An analytical method enabling the detection and quantification of the individual enantiomers of racemic (±) pinocembrin is required to fully characterize its pharmacokinetic disposition. Direct resolution of the enantiomers of pinocembrin was achieved using a novel and simple reversed-phase high-performance liquid chromatography method with electrospray ionization and detection by mass spectrometry in rat serum. A Chiralcel® AD-RH column was employed to perform baseline separation with electrospray positive-mode ionization with selected ion monitoring detection. The standard curves were linear from 0.5 to 100 µg/mL for each enantiomer. The limit of quantification was 0.5 µg/mL. The assay was applied successfully to stereoselective serum disposition of pinocembrin enantiomers in rats. Pinocembrin enantiomers were detected in serum. Both enantiomers had a serum half-life of ~15 min in rats. Similar values of volume of distribution between the enantiomers were also observed: 1.76 L/kg for S-pinocembrin and 1.79 L/kg for R-pinocembrin. Total clearance was 5.527 L//h/kg for S-pinocembrin and 5.535 L/h/kg for R-pinocembrin, and the area under the curve was 1.821 µg h/mL for S-pinocembrin and 1.876 µg h/mL for R-pinocembrin. The large volume of distribution coupled with the short serum half-life suggests extensive distribution of pinocembrin into the tissues.

An LC/MS Assay for Analysis of Vorinostat in Rat Serum and Urine: Application to a Pre-Clinical Pharmacokinetic StudyElham A. Mohamed

The utility of currently reported liquid chromatography mass spectrometry methods for quantitation of vorinostat in plasma or serum may be limited. These methods employ time consuming and expensive procedures such as solid phase extraction or limited-access techniques such as high turbulence liquid chromatography coupled with column switching. This study offers a simple isocratic LC/MS method validated for determination of vorinostat in both rat serum and urine. Proteins were precipitated from serum using ice-cold acetonitrile and daidzein was used as internal standard. Separation was achieved using a Phenomenex Luna ® C 18 (2) (5 μm, 250 x 4.60 mm) column and isocratic elution with a mobile phase consisting of acetonitrile, water, and formic acid (30:70:0.1, v/v/v). Mass spectrometry detection using electrospray positive-mode ionization with selected ion monitoring detection was employed. The calibration curves were linear ranging from 0.05 to 50 μg/ml in serum and from 0.5 to 25 μg/ml in urine. In both biological matrices, assay precision was <15% (RSD) and the intra- and inter-run bias were within acceptable range (–15% to 15%). No degradation of vorinostat in either matrix was found following three freeze-thaw cycles and 24 h storage in the auto-injector. The lower limit of quantitation in rat serum and urine were 0.05 and 0.5 μg/ml, respectively. The upper limit of quantitation in rat serum and urine were 50 and 25 μg/ml, respectively. This assay was applied successfully to a pre-clinical study of vorinostat pharmacokinetics in rats.

Rapid Determination of Underivatized Arginine, Ornithine, Citrulline and Symmetric/Asymmetric Dimethylarginine in Human Plasma by LC–MS

A rapid and specific liquid chromatography-mass spectrometry method was developed for the simultaneous determination of underivatized arginine, ornithine, citrulline, symmetric and asymmetric dimethylarginine in human plasma. The plasma samples were extracted with acetonitrile after addition of isotopic internal standards and then chromatographed on an Atlantis dC18 column (4.6 × 100 mm, 3.0 μm). The mobile phase was composed of 0.03% trifluoroacetic acid in water and the flow rate was 0.6 mL min−1. Selected ion monitoring detection was performed on a single-quadrupole mass spectrometer using positive electrospray ionization. The method was well validated and then successfully applied to a clinical study in healthy subjects.

Validation of a confirmatory method for the determination of melamine in egg by gas chromatography–mass spectrometry and ultra-performance liquid chromatography–tandem mass spectrometry

A sensitive and reliable method was developed and validated for detection and confirmation of melamine in egg based on gas chromatography–mass spectrometry (GC–MS) and ultra-performance liquid chromatography–tandem mass spectrometry (UPLC–MS/MS). Trichloroacetic acid solution was used for sample extraction and precipitation of proteins. The aqueous extracts were subjected to solid-phase extraction by mixed-mode reversed-phase/strong cation-exchange cartridges. Using ultra-performance liquid chromatography and electrospray ionization in the positive ion mode, melamine was determined by LC–MS/MS, which was completed in 5 min for each injection. For the GC–MS analysis, extracted melamine was derivatized with N, O-bis(trimethylsilyl)trifluoracetamide prior to selected ion monitoring detection in electron impact mode. The average recovery of melamine from fortified samples ranged from 85.2% to 103.2%, with coefficients of variation lower than 12%. The limit of detection obtained by GC–MS and UPLC–MS/MS was 10 and 5 μg kg −1, respectively. This validated method was successfully applied to the determination of melamine in real samples from market.

GC–MS Method Development for the Analyses of Thiophenes from Solvent Extracts of Tagetes patula L

The purpose of the present study was to develop GC–MS methods for the qualitative analyses of thiophenes and quantitative determination of 2,2′:5′,2″-terthiophene (α-terthienyl) from the solvent extracts of Tagetes patula L. hairy root cultures and field-grown plants. It was furthermore aimed to characterize the analytical parameters of these methods. Several injection techniques (split, splitless, pulsed splitless and temperature programmed pulsed splitless) were studied in order to achieve the best performance. The pulsed splitless injection combined with temperature programming provided highest signal response, best repeatability and peak shape. The split injection was not sensitive enough and the hot splitless methods had poor repeatability. For quantitative work, an internal standard calibration method was applied using selected ion monitoring detection. Validation studies proved that the global method had good repeatability and satisfactory recovery. The intact plant roots contained the highest amounts of α-terthienyl (590 ± 11.1 μg g−1) while the hairy root clone #TpA6 and #TpR had considerably diverse amounts (421 ± 18.0 and 5.6 ± 0.65 μg g−1, respectively).

Urinary Excretion Study of Coenzyme Q10 in Rats by Ultra-Performance Liquid Chromatography-Mass Spectrometry

A method based on ultra-performance liquid chromatography mass spectrometry (UPLC-MS) applying atmospheric pressure chemical ionization in the positive ion mode is developed for the determination of coenzyme Q10 (CoQ10) in rat urine. The assay involves the extraction of crude urine, fast liquid chromatography on a Waters Acquity UPLC BEH C18 column (1.7 microm, 1.0 x 50 mm), and selected ion monitoring detection using mass transition. The calibration range is found to be 0.05-25 microg/mL, with the lower limit of quantitation of 0.05 microg/mL. Intra- and inter-day precision (relative standard deviation) for CoQ10 in rat urine range from 0.7% to 15%, and accuracy expressed in recovery rates in urine is between 83% and 118%. The recovery of this method is found to be between 80% and 95% at three concentrations. The total cumulative recovery of CoQ10 is 1.16 +/- 1.05% (percentage of dose intake, n = 4) from rat urine collected over 30 h after oral administration of the drug. The UPLC-MS method described allows the quick determination of CoQ10 in rat urine with good precision and accuracy. It is suitable for further excretion studies of CoQ10 in animals.

Evidence for in situ ethanolamine phospholipid adducts with hydroxy-alkenals

Hydroxy-alkenals, such as 4-hydroxy-2(E)-nonenal (4-HNE; from n-6 fatty acids), are degradation products of fatty acid hydroperoxides, including those generated by free radical attack of membrane polyunsaturated fatty acyl moieties. The cytotoxic effects of hydroxy-alkenals are well known and are mainly attributable to their interaction with different molecules to form covalent adducts. Indeed, ethanolamine phospholipids (PEs) can be covalently modified in a cellular system by hydroxy-alkenals, such as 4-HNE, 4-hydroxy-2(E)-hexenal (4-HHE; from n-3 fatty acids), and 4-hydroxy-dodecadienal (4-HDDE; from the 12-lipoxygenase product of arachidonic acid), to form mainly Michael adducts. In this study, we describe the formation of PE Michael adducts in human blood platelets in response to oxidative stress and in retinas of streptozotocin-induced diabetic rats. We have successfully characterized and evaluated, for the first time, PEs coupled with 4-HHE, 4-HNE, and 4-HDDE by gas chromatography-mass spectrometry measurement of their ethanolamine moieties. We also report that aggregation of isolated human blood platelets enriched with PE-4-hydroxy-alkenal Michael adducts was altered. These data suggest that these adducts could be used as specific markers of membrane disorders occurring in pathophysiological states with associated oxidative stress and might affect cell function.

Gas Chromatography Analysis of Urinary Alkoxyacetic Acids as Biomarkers of Exposure to Aliphatic Alkyl Ethers

Analysis of alkoxyacetic acids has received considerable research interest in toxicology because these compounds have been reported as metabolites and biomarkers of exposure to widely used industrial chemicals such as alkyl-substituted ethylene glycols and other aliphatic ethers. This paper describes an improved method for the determination of methoxyacetic acid (MAA), ethoxyacetic acid (EAA), and butoxyacetic acid (BAA) in rat urine. Solid-phase extraction with Bakerbond(T) C18 bonded silica cartridges was successfully employed to isolate the acids from rat urine. The acids were then converted to methyl esters with diazomethane derivatization and analyzed using a gas chromatograph (GC) equipped with a mass spectrometry (MS) and a GC with flame ionization detector (FID). Employing GC-MS under selected ion monitoring detection, the lowest detection concentrations for MAA, EAA, and BAA were determined to be from 2 to 4 ng/mL urine in 1 mL of sample size. This method is 5 to 10 times more sensitive than that using GC-FID. The method described here is superior to the existing ones reported in the literature in that it employs an easy sample treatment procedure and gives much higher recoveries, making it suitable for routine assays. The utility of this new method was demonstrated in a toxicology study of aliphatic alkyl ethers.

Levels of 7-oxocholesterol in cerebrospinal fluid are more than one thousand times lower than reported in multiple sclerosis

In a recent publication [Diestel, A., O. Aktas, D. Hackel, I. Hake, S. Meier, C. S. Raine, R. Nitsch, F. Zipp, and O. Ullrich. 2003. Activation of microglial poly (ADP-ribose)-polymerase-1 by cholesterol breakdown products during neuroinflammation: a link between demyelination and neuronal damage. J. Exp. Med. 198: 1729-1740], extremely high levels of 7-oxocholesterol were reported in cerebrospinal fluid (CSF) of 11 patients with multiple sclerosis (MS) [7.4 +/- 0.3 mg/l (mean +/- SEM)]. The corresponding level of 12 subjects with other kinds of neurological diseases was reported to be 0.5 +/- 0.1 mg/l. Such high levels of 7-oxocholesterol were found to cause neuronal damage of living brain tissues. Using a highly accurate method for an assay of 7-oxocholesterol based on isotope dilution-mass spectrometry and anaerobic conditions during workup, we found that the level of 7-oxocholesterol in CSF from 29 Swedish patients with MS was only 1.2 microg/l (median, ranging from 0.4 to 4.6 microg/l), less than 1/1,000 th of the previously reported level. The level of 7-oxocholesterol in CSF from 24 Swedish control patients was 0.9 microg/l (0.3-2.3 microg/l), slightly but significantly lower than the CSF level in MS patients (P=0.002). In vitro-induced lipid peroxidation of the endogenous cholesterol in CSF increased the level of 7-oxygenated cholesterol metabolites, particularly 7-oxocholesterol, up to approximately 0.3 mg/l. These results are discussed in relation to the fact that 7-oxygenated steroids are easily artificially formed by autoxidation of cholesterol during workup procedures and analysis of sterols and oxysterols from biological samples.

GC—MS in Space Research: Decoding Complex Isothermal Chromatograms Recovered from Space Missions

An analytical procedure is described to study GC-MS isothermal chromatograms simulating those recovered from space missions: in fact GC plays a predominant role in space missions devoted to characterizing the chemical composition of extra-terrestrial atmospheres. SIM (selected ion monitoring) detection was used for monitoring selected chemical classes: a simplified chromatogram can be obtained giving information on the chemical composition of the complex mixture. Since only isothermal GC chromatograms are allowed by flight constraints, a time axis transformation is required to make them homogeneous: i.e., constant retention increments for CH2 additions in terms of a homologous series. The order in the linearized chromatogram can be simply singled out with a chemometric approach based on the study of the Autocovariance Function (ACVF) computed on the digitized chromatogram: the plot of the experimental autocorrelation function (EACF) shows well-shaped peaks if constant interdistances are repeated in different regions of the chromatogram. The method was applied to standard mixtures representative of planetary atmospheres--hydrocarbons, nitriles and oxygenated compounds with between 3 and 12 carbon atoms--analyzed in flight simulating conditions. The coupling of the selectivity of SIM detection with the interpretation power of the EACF procedure proves to be a powerful tool for interpreting data recovered from space missions: the chemical composition of the mixture can be identified by handling the raw SIM chromatograms.

Determination of polynuclear aromatic hydrocarbons in aerosol by solid-phase extraction and gas chromatography–mass spectrum

The optimum procedures for clean up aerosols in silica solid-phase extraction (SPE) cartridge prior to the analysis of polynuclear aromatic hydrocarbons (PAHs) by gas chromatography–mass spectrum (GC–MS) in selected ion monitoring detection mode have been investigated. The silica SPE cartridge is activated by dichloromethane and hexane, and then dried up by vacuum in SPE instrument for about 5 min. The sample volume loaded on the cartridge is 3 ml and after loading the sample the cartridge was dried in vacuum for 5 min. The PAHs were eluted from the cartridge by 3 ml 20% dichloromethane in hexane. The flow-rate of sample loading and eluting was controlled in about 1 ml min −1. The aerosols collected on the campus of Beijing Normal University from August 2001 to July 2002 have been processed with these optimum procedures and 16 EPA priority pollution PAHs in the aerosols have been quantitatively determined.

Enantioselective analysis of methadone in saliva by liquid chromatography–mass spectrometry

Saliva was tested and evaluated as a biological matrix for methadone (Mtd) monitoring. Conventional method using a narrow bore C 18 column, and an enantioselective method using a narrow bore α 1-acid glycoprotein column, were developed using liquid chromatography coupled with a mass spectromeric (MS) detector. After optimisation of MS conditions by flow injection analysis, selected ion monitoring detection was used to enhance sensitivity. The total Mtd concentration and the enantiomeric ratio in saliva were validated using an experimental design. The methods were applied to samples provided by heroin addicts undergoing a Mtd treatment. Results on total Mtd determination showed a very poor correlation between saliva and serum, whereas the enantiomeric ratios of Mtd gave a very good one.

High-performance liquid chromatography/atmospheric pressure chemical ionization mass spectrometric method for the analysis of catecholamines and metanephrines in human urine.

An assay of norepinephrine (NE), epinephrine (E), dopamine (DA), normetanephrine (NE) and metanephrine (MN) based on high-performance liquid chromatography (HPLC) in combination with atmospheric pressure chemical ionization mass spectrometry (APcI-MS) is described. The catecholamines and metanephrines were extracted from urine and aqueous samples using Bio-Rex 70 cation-exchange resin and subjected to analysis by HPLC/APcI-MS. The separation was performed on a C18 column in 50 mM ammonium formate buffer, pH 3.0, using a flow rate of 0.8 mL/min. Acetonitrile was added post-column at a flow rate of 0.2 mL/min via a post-column addition tee. The total analysis time was 6.5 min. The quantitative analysis was performed using 3,4-dihydroxybenzylamine (DHBA) as the internal standard (I.S.). Selected ion monitoring detection was applied: m/z 170 (for NE), 184 (for E and NM), 154 (for DA), 198 (for MN) and 140 (for DHBA, I.S.). The limits of quantitation were 5 ng/mL for NE, E and DA and 2.5 ng/mL for NM and MN. The recovery ranged from 75 to 83% for each analyte. The method was found to be simple and highly selective for the determination of catecholamines and metanephrines in the urine of patients suspected of pheochromocytoma.

Monitoring of olanzapine in serum by liquid chromatography–atmospheric pressure chemical ionization mass spectrometry

A selective assay of olanzapine with liquid chromatography atmospheric pressure chemical ionization (LC–APCI–MS, positive ions) is described. The drug and internal standard (ethyl derivative of olanzapine) were isolated from serum using a solid-phase extraction procedure (C 18 cartridges). The separation was performed on ODS column in acetonitrile–50 m M ammonium formate buffer, pH 3.0 (25:75). After analysis of mass spectra taken in full scan mode, a selected-ion monitoring detection (SIM) was applied with the following ions: m/z 313 and 256 for olanzapine and m/z 327 and 270 for the internal standard for quantitation. The limit of quantitation was 1 μg/l, the absolute recovery was above 80% at concentration level of 10 to 100 μg/l. The method tested linear in the range from 1 to 1000 μg/l and was applied for therapeutic monitoring of olanzapine in the serum of patients receiving (Zyprexa™) and in one case of olanzapine overdose. Olanzapine in frozen serum samples and in frozen extracts was stable over at least four weeks. The examinations of urine extracts from patients receiving olanzapine revealed peaks of postulated metabolites (glucuronide and N-desmethylolanzapine).

MONITORING OF OLANZAPINE IN SERUM BY LIQUID CHROMATOGRAPHY-ATMOSPHERIC PRESSURE CHEMICAL IONIZATION MASS SPECTROMETRY.

Abstract A selective assay of olanzapine with liquid chromatography atmospheric pressure chemical ionization (LC–APCI–MS, positive ions) is described. The drug and internal standard (ethyl derivative of olanzapine) were isolated from serum using a solid-phase extraction procedure (C 18 cartridges). The separation was performed on ODS column in acetonitrile–50 m M ammonium formate buffer, pH 3.0 (25:75). After analysis of mass spectra taken in full scan mode, a selected-ion monitoring detection (SIM) was applied with the following ions: m/z 313 and 256 for olanzapine and m/z 327 and 270 for the internal standard for quantitation. The limit of quantitation was 1 μg/l, the absolute recovery was above 80% at concentration level of 10 to 100 μg/l. The method tested linear in the range from 1 to 1000 μg/l and was applied for therapeutic monitoring of olanzapine in the serum of patients receiving (Zyprexa™) and in one case of olanzapine overdose. Olanzapine in frozen serum samples and in frozen extracts was stable over at least four weeks. The examinations of urine extracts from patients receiving olanzapine revealed peaks of postulated metabolites (glucuronide and N -desmethylolanzapine).

The analysis of fluvalinate in beeswax using GC/MS

A method for quantitation of the synthetic pyrethroid fluvalinate in beeswax has been developed. The method uses the internal standard permethrin added in the first acetonitrile extraction step. Subsequent cleanup involves partitioning into ether and use of a florisil column. The final gas chromatography was performed on a capillary column with selected ion monitoring detection using a mass spectrometer. The presence of fluvalinate was confirmed by the retention times of two identical peaks which had a 75:25 area ratio of the peaks at m/z of 250:252 (ion contains chlorine). Fluvalinate recovery of 108 and 97% were obtained at the 0.52 and 1.04 ppm spike level (respectively) using peak area calculations. The detection limit was determined to be 0.05 ppm.