Ionization In Negative Ion Mode Research Articles

Development and validation of a UPLC-MS/MS method for the quantification of sugars and non-nutritive sweeteners in human urine

High-intensity sweeteners (‘sweeteners’), such as sucralose, saccharine, acesulfame, cyclamate and steviol, are replacing sugars in many food products, but biomarker-based data on their population-wide exposure, as well as analytical methods that can quantify urinary concentrations of sugars and sweeteners simultaneously, are lacking. Here, we developed and validated an ultra-pressure liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS) method to quantify glucose, sucrose, fructose, sucralose, saccharine, acesulfame, cyclamate and steviol glucuronide in human urine. Urine samples were prepared by a simple dilution step containing the internal standards in water and methanol. Separation was achieved on a Shodex Asahipak NH2P-40 hydrophilic interaction liquid chromatography (HILIC) column using gradient elution. The analytes were detected using electrospray ionization in negative ion mode, and selective reaction monitoring was optimized using the [M−H]- ions. Calibration curves ranged between 34 and 19,230 ng/mL for glucose and fructose, and 1.8 to 1,026 ng/mL for sucrose and the sweeteners. The method has acceptable accuracy and precision, which depends on the application of appropriate internal standards. Storage of urine samples in lithium monophosphate gives the best overall analytical performance, and storage at room temperature without any preservatives should be avoided since this leads to reduced glucose and fructose concentrations. With the exception of fructose, all analytes were stable throughout 3 freeze–thaw cycles. The validated method was applied to human urine samples, demonstrating quantifiable concentrations of the analytes which were in the expected range. It is concluded that the method has acceptable performance to quantitatively determine dietary sugars and sweeteners in human urine.

Understanding the mechanism of CO2-Assisted electrospray ionization for parameter optimization in supercritical fluid chromatography mass spectrometry

Supercritical fluid chromatography (SFC) is often coupled with electrospray ionization mass spectrometry (ESI-MS) for analyte detection because of its detection capability to a wide range of chemical properties. However, MS sensitivity is highly dependent on the chromatographic conditions, so that it is important to understand the ionization mechanism to determine the optimal chromatographic conditions. The ionization mechanism in SFC/ESI-MS is different to that of liquid chromatography because of the use of CO2 as a mobile phase. Some studies have suggested that alkoxycarbonic acids are formed in the mixture of CO2 and the alcohol modifier, and these species contribute to ionization in CO2-assisted SFC/ESI-MS. Therefore, in this study, we investigated CO2-assisted ESI to test this hypothesis, and we confirmed that methoxylcarbonic acid is generated in CO2/methanol mixtures and contributed to ion generation and detection because it acts as a proton donor in positive-ion mode. However, methoxylcarbonic acid interfered with ionization in negative-ion mode. Addition of ammonium acetate, which is often added to the modifier for negative ion detection in SFC/MS analysis, did not contribute to the recovery of MS sensitivity, although it tended to suppress the formation of metoxylcarbonic acid. This is likely due to ion suppression and neutralization of the negative sites of the analytes by anions or cations derived from ammonium acetate in the negative ion mode. Thus, additive-free methanol/CO2 was the most suitable mobile phase for obtaining high sensitivity in SFC/MS. To demonstrate the practicality of these findings, we tested our optimal mobile phase selection for pesticide analysis. In addition, we tested the addition of 0, 1, and 5 mM ammonium formate to the modifier and make-up solvent, and found that the addition of 1 mM ammonium formate gave the best results in pesticides analysis. In SFC/MS, salt is often added to improve separation or prevent desorption, but our findings suggest that the concentration of salt must be kept as low as possible to achieve highly sensitive MS detection. The results of this study reveal the best selection of the optimal conditions for the modifier and make-up solvent for CO2-assisted SFC/MS analysis and will be useful for the method development in SFC/MS.

Determination of Gypenoside A and Gypenoside XLIX in Rat Plasma by UPLC-MS/MS and Applied to the Pharmacokinetics and Bioavailability.

In this work, a UPLC-MS/MS method was developed for the determination of gypenoside A and gypenoside XLIX in rat plasma. For chromatographic separation, a UPLC BEH C18 column was employed, the mobile phase comprised acetonitrile: water (w/0.1% formic acid), and the elution time was 4 min. Detection of each compound was enabled by electrospray ionization in negative-ion mode, and quantitative analysis was enabled by operating in multiple reaction monitoring (MRM) mode by monitoring the transitions of m/z 897.5⟶403.3 for gypenoside A, m/z 1045.5⟶118.9 for gypenoside XLIX, and m/z 825.4⟶617.5 for the internal standard. The calibration curves for gypenoside A and gypenoside XLIX demonstrated excellent linearity (r > 0.995) over the range of 2–3000 ng/mL. The intraday and interday precisions of gypenoside A and gypenoside XLIX were within 14.9%, the intraday and interday accuracies ranged from 90.1% to 113.9%, the recoveries were all greater than 88.3%, and the matrix effect ranged from 87.1% to 94.1%. The developed method was successfully applied in the determination of the pharmacokinetics of gypenoside A and gypenoside XLIX. Gypenoside A and gypenoside XLIX had very short half-lives in rats, with oral t1/2z of 1.4 ± 0.2 h and 1.8 ± 0.6 h, respectively, and low bioavailabilities (0.90% and 0.14%, respectively).

Characterization of crude oils derived from carbonate and siliciclastic source rocks using FTICR-MS

The scope of this study was to develop robust lithofacies proxies which are less affected by other geochemical processes such as maturity and biodegradation. Here, crude oils derived from carbonate and siliciclastic source rocks from different petroleum settings were investigated using Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS), thereby providing information on the role of depositional environment in controlling the chemical composition of hydrocarbons. The carbonate oils belong to the Western Canada Sedimentary Basin (WCSB) and the siliciclastic oils were mainly collected from the Austrian parts of the Molasse Basin and the Vienna Basin, Austria. The variations in chemical composition, aromaticity as well as alkylation degree of the main compound classes in both oil types are discussed in detail using data from FTICR-MS in two different ionization modes: electrospray ionization in negative ion mode (ESI–N) and atmospheric pressure photoionization in positive ion mode (APPI–P). The results obtained from both ionization modes indicate that the chemical compound distributions of acidic constituents such as oxygen-only components (the O1 to O4 classes) and the N1S1 class, as well as sulfur and hydrocarbon species in oils from carbonates are clearly different from those generated by siliciclastic rocks. Most likely, the observed differences are attributed to depositional environments of the respective source rocks as the impacts of other processes such as thermal maturity and biodegradation, were mitigated by selection of non-biodegraded oils that display comparable maturation levels. The calculated vitrinite reflectance (%Rc) in most of the selected oils range between 0.5 and 0.8. The observed differences in chemical composition of oils from carbonates and siliciclastics lead to suggested novel source-sensitive proxies based on the DBE distribution of the S1 and HC species (from APPI–P) and the O1 and N1S1 classes (from ESI–N). The former proxy is the ratio of the S1 class DBE 9 group (radical ions; likely sum of alkylated dibenzothiophenes) relative to the HC class DBE 10 group (radical ions; likely sum of alkylated phenanthrenes). It appears that this proxy is mirroring the “DBT/P ratio” obtained from GC–MS data over a much broader range of molecular masses up to approximately 1000 Da. The other proxy is based on the observed differences between the O1 class DBE 4 group and the N1S1 class DBE 14 group. Whereas oils derived from the siliciclastic source rocks show higher concentrations of the O1 class, oils originated from the carbonate source units are enriched in the N1S1 species. Finally, published FTICR-MS data (APPI–P) from both oil source types with varying levels of maturation and biodegradation are included, in order to verify the robustness of the proposed proxies.

Unravelling the impact of lithofacies on the composition of NSO compounds in residual and expelled fluids of the Barnett, Niobrara and Posidonia formations

The influence of lithofacies on the composition of NSO (nitrogen-, sulfur- and oxygen- containing) compounds in unconventional petroleum systems has been investigated using examples of biogenic carbonate-rich Niobrara Shale, biogenic quartz-rich Barnett Shale and detrital clay-rich Posidonia Shale. The chosen sample sets all contain Type II marine kerogen in the peak–late oil window. Solvent extracts were analyzed using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS), combined with atmospheric pressure photoionization in positive ion mode ((+)-APPI) and electrospray ionization in negative ion mode ((−)-ESI). Covering source and reservoir units, our study furthermore enables tracing the impact of lithofacies on primary petroleum migration within the Niobrara and Barnett shales.Siliciclastic Barnett and Posidonia shale extracts reveal higher proportions of NSO compounds confirming their generally higher retention capacities for polar organic compounds. However, different retention specificities of biogenic quartz- and clay-rich rocks are indicated by varying NSO compound compositions in their bitumen fraction: biogenic quartz preferentially preserves and retains organonitrogen compounds, while the more polar acidic organooxygen species are preferably retained by clay minerals. Extracts from the carbonate rocks contain a larger fraction of nonaromatic cyclic sulfoxides and amides that are likely formed by oxidation processes during maturation of organic matter.Fractionations induced by the intra-formation migration differ between the Barnett and Niobrara sample sets. While low-polarity organonitrogen species are retained in both Barnett (to a greater extent) and Niobrara source units, a preferential migration of highly alkylated and small acidic NSO components out of the source is only observed in the Niobrara samples.

Direct mass spectrometric analysis of naphthenic acids and polycyclic aromatic hydrocarbons in waters impacted by diluted bitumen and conventional crude oil

Crude oil spills have well-documented, deleterious impacts on the hydrosphere. In addition to macroscopic effects on wildlife and waterscapes, several classes of petroleum derived compounds, such as naphthenic acids (NAs) and polycyclic aromatic hydrocarbons (PAHs), may be released into the water and present aquatic contamination hazards. The concentrations of these contaminants may be affected by both oil type and water chemistry. We characterize the concentrations of NAs and PAHs in natural and constructed waters, spanning a range of pH and salinity, and directly compare the influence of diluted bitumen (DB) and conventional crude (CC) oil, using condensed-phase membrane introduction mass spectrometry (CP-MIMS) as a direct sampling, on-line technique. The concentration and isomer class profiles of classical NAs in the aqueous phase were assessed using electrospray ionization in negative-ion mode as [M-H]− whereas PAH concentrations were monitored using liquid electron ionization (LEI) in positive-ion mode as [M+•]. NA concentrations (0.03–25 ppm) were highly pH-dependent, and an order of magnitude greater in water samples contaminated with DB than CC. Conversely, concentrations of naphthalene (10–130 ppb) and alkyl-naphthalenes (10–90 ppb) were three to four-fold higher in water samples exposed to CC. We demonstrate that naturally occurring dissolved organic matter does not bias results from the membrane sampling approach employed, and that DB and CC contaminated waters can be differentiated using principal component analysis of the NA isomer class distribution in both constructed and natural waters. Finally, we describe the first demonstration of the concurrent analysis of trace NAs and PAHs in the same water sample by controlling perm-selectivity at the membrane and the ionization mode of the mass spectrometer. The techniques employed here for trace analysis of petroleum derived compounds in water can be applied to rapid screening and real-time monitoring of contamination and remediation processes.

NSO-compounds in oil-bearing fluid inclusions revealed by FT-ICR-MS in APPI (+) and ESI (−) modes: A new method development

The origins of hydrocarbons occurring in oil-bearing fluid inclusions (FIs) have been studied in detail over the last four decades, but very little is known about co-occurring nitrogen, sulfur and oxygen (NSO)-containing compounds. Here, we outline a new method for gathering valuable information on NSO-compounds using the Fourier Transform-Ion Cyclotron Resonance-Mass Spectrometry (FT-ICR-MS) in combination with Atmospheric Pressure Photoionization in positive ion mode (APPI (+)) and Electrospray Ionization in negative ion mode (ESI (−)). A key element was to develop a rigorous acid-free cleaning protocol to make oil inclusions from a broad range of host materials accessible to the very sensitive FT-ICR-MS technique. Although oil contamination from surrounding organic matter could not be entirely eliminated, the procedure enables distinction of external contaminants and identification of affected NSO-compound classes allowing a conditional interpretation of the FT-results of FI samples, especially for compounds measured in the APPI (+) mode. First insights into the high molecular weight hydrocarbons and NSO-compounds in FI oils are presented here using examples from Germany, Tunisia, Pakistan and Mexico.

Regiochemical Assignment of N-Acylphosphatidylethanolamines (NAPE) by Liquid Chromatography/Electrospray Ionization with Multistage Mass Spectrometry and Its Application to Extracts of Lupin Seeds.

1,2-Diacyl-sn-glycero-3-phospho-N-acyl-ethanolamines (NAPE) are low abundance phospholipids but important constituents of intracellular membranes of plant tissues, responsible for generating bioactive N-acylethanolamine (NAE), which participates in several physiological processes such as regulation of seed germination and protection against pathogenic attacks. From an analytical point of view, the critical aspect of these bioactive lipids lies in the determination of fatty acyl chains located in sn-1/sn-2 position on the glycerol backbone (O-linked), along with the amide-bound (N-linked) fatty acyl chain. Here, the identity and occurrence of NAPE in lipid extracts of lupin seeds (Lupinus luteus L.) was assessed by electrospray ionization in negative ion mode upon reversed-phase liquid chromatography (RPLC-ESI) coupled to mass spectrometry (MS) either at high- (i.e., Orbitrap FTMS) or low- (linear ion trap, LIT) resolution/accuracy. Collisional induced dissociation (CID)-tandem MS and MS3 acquisitions of chemically prepared NAPE allowed to unequivocally recognize the N-linked fatty acyl chain and to establish the diagnostic product ions that were successfully applied to identify NAPE in lipid extracts of yellow lupin seeds. The most abundant NAPE species were those containing N-acyl groups C18:1, C18:2; a minor prevalence was found for C16:0, C18:0, and C18:3, and almost the same acyl chains O-linked on the glycerol backbone in several sn-1/sn-2 combinations were observed. The positional isomers of NAPE species were identified as deprotonated molecules ([M-H]-) at m/z 978.7541 (three isomers 52:3), m/z 980.7694 (two isomers 52:2), m/z 1002.7535 (four isomers 54:5), m/z 1004.7686 (two isomers 54:4), m/z 1006.7837 (two isomers 54:3), and m/z 1008.8026 (single isomer 54:2). The total amount of NAPE in lupin seeds ranged in the interval of 2.00 ± 0.13 mg/g dw, in agreement with other edible legumes. We anticipate our approach to be a robust assessment method potentially applicable to biological extracts containing NAPE species and can provide comprehensive profiles and contents.

Identification of isoflavones in the extract of supplements for menopause symptoms by direct infusion electrospray ionization tandem mass spectrometry.

In recent years high consumption of dietary supplements has been observed. However, the consumption of dietary supplements may lead to the unexpected side effects that can be related to the number of adulterated supplements quite often marketed. It has prompted the search for a fast and reliable method of identification of main active compounds in the supplements. In this study, the isoflavones present in the methanol extracts of dietary supplements for menopause symptoms were identified by using direct infusion electrospray ionization tandem mass spectrometry. The product ion spectra of [M-H]- ions derived from the extracts matched very well those obtained for standard compounds. Daidzein, genistein, and glycitein were identified in the soy-based supplements, while daidzein, formononetin, and biochanin A were identified in the red clover-based ones. The respective [M+Na]+ ions were also detected; however, their product ion spectra did not allow isoflavone identification. It can be concluded that the main isoflavones present in the extracts of dietary supplements can be successfully and quickly identified by using the direct infusion electrospray ionization in negative ion mode, followed by the tandem mass spectrometry experiment.

Analysis of Flavonoids in Dalbergia odorifera by Ultra-Performance Liquid Chromatography with Tandem Mass Spectrometry.

Dalbergia odorifera, a traditional Chinese medicine, has been used to treat cardio- and cerebrovascular diseases in China for thousands of years. Flavonoids are major active compounds in D. odorifera. In this paper, a rapid and sensitive ultra-high performance liquid chromatography-triple quadrupole mass spectrometry method was developed and validated for simultaneous determination of 17 flavonoids in D. odorifera. Quantification was performed by multiple reaction monitoring using electrospray ionization in negative ion mode. Under the optimum conditions, calibration curves for the 17 analytes displayed good linearity (r2 > 0.9980). The intra- and inter-day precisions (relative standard deviations) were lower than 5.0%. The limit of quantitation ranged from 0.256 to 18.840 ng/mL. The mean recovery range at three spiked concentrations was 94.18–101.97%. The validated approach was successfully applied to 18 samples of D. odorifera. Large variation was observed for the contents of the 17 analytes. Sativanone and 3′-O-methylviolanone were the dominant compounds. The fragmentation behaviors of six flavonoids were investigated using UPLC with quadrupole time-of-flight tandem mass spectrometry. In negative ion electrospray ionization mass spectrometry, all the flavonoids yielded prominent [M − H]− ions. Fragments for losses of CH3, CO, and CO2 were observed in the mass spectra. Formononetin, liquiritigenin, isoliquiritigenin, sativanone, and alpinetin underwent retro-Diels–Alder fragmentations. The proposed method will be helpful for quality control of D. odorifera.

Development and Validation of a UPLC-ESI(-)-MS/MS Methodology for the Simultaneous Quantification of Hesperidin, Naringin, and their Aglycones in Chicken Tissue Samples.

The dietary supplementation of livestock with antioxidants to improve the meat quality represents an active research area of high commercial impact. In order to investigate the optimal dosing, analytical methodologies need to be developed in various tissues to evaluate which concentration does remain in the tissue. We aimed to develop and validate a sensitive and specific methodology for the simultaneous quantitative determination of hesperidin, naringin, hesperetin, and naringenin in chicken tissue samples employing ultra-performance LC-tandem MS. Lipid extraction using cold chloroform was performed followed by protein precipitation by cold acetone. Chromatography was performed on a C18 column using a ternary gradient of water, acetonitrile, and isopropanol-acetonitrile-acetone (58+40+2, v/v) as the mobile phase. Detection was performed by electrospray ionization in negative ion mode with the selected reaction monitoring technique. Calibration plots exhibited good linearity (r2 > 0.99) over the concentration range from 0.125 to 25 μg/g tissue for the four analytes, and the lower LOQ for the four analytes was 0.125 μg/g tissue. The repeatability as percent relative SD and precision as percent accuracy were <20 and >80%, respectively. The developed methodology was applied for the quantitative determination of hesperidin, naringin, hesperetin, and naringenin in tissue samples after dietary supplementation with 1.5 g/kg hesperidin and 1.5 g/kg naringin in Ross 308 broiler chickens. This is the first methodology to access naringin, naringenin, hesperidin, and hesperetin in chicken tissue. It involved simple sample preparation, and the mass spectrometry based detection ensures high specificity and sensitivity.

Simultaneous determination of six compounds in rat plasma by ultra-performance liquid chromatography with tandem mass spectrometry: Application in the pharmacokinetic study of Qing Gan-Shu Yu-Fang

A rapid and high selective ultra-performance liquid chromatography (UPLC) with tandem mass spectrometry method for simultaneous determination of six compounds including albiflorin, paeoniflorin, picroside I, picroside II, saikosaponin A, and saikosaponin D in rat plasma was developed and validated using butyl p-hydroxybenzoate as an internal standard. One-step direct protein precipitation with acetonitrile was used to extract the compounds from the rat plasma samples. Chromatographic separation was achieved using an ACQUITY UPLC BEH C18column (100 mm × 2.1 mm, 1.7 μm) at a flow rate of 0.4 mL/min, using gradient mode containing 0.1% formic acid in water and acetonitrile were used as the Mobile phase A and B. Electrospray ionization in negative ion mode and multiple reaction monitoring were used to identify and quantify active components. Calibration curves showed good linearity (R2 > 0.9908) over a wide concentration range for all compounds. The intra- and interday precision (relative standard deviation) ranged 2.4%–7.0% and 2.6%–8.0%, respectively. The accuracy (relative error) was from −13.0% to 13.2% at all quality control levels. The recovery ranged from 81.1% to 92.5%. The validated method was successfully applied to pharmacokinetic study in rats after oral administration of Qing Gan-Shu Yu-Fang. The results show that one can draw a conclusion that these six active ingredients can be quickly absorbed and play a pharmacodynamic role rapidly in vivo.

A pharmacokinetic study on oleracone C after oral and intravenous administration

Oleracone C, a new homoisoflavanone recently isolated from the plant Portulaca oleracea L., has obvious pharmacological activities. Subsequently, its pharmacokinetic profiles in rats' plasma after oral and intravenous administrations were studied by a simple and rapid ultra high-performance liquid chromatography electrospray ionization quadrupole-time of flight mass spectrometry (UHPLC-ESI-Q-TOF/MS) with apigenin as an internal standard (IS). The analysis was performed on an Agilent Zorbax Eclipse Plus C18 Column (2.1 × 50 mm, 1.8 μm) by elution with acetonitrile and water (containing 0.1% formic acid) at a flow rate of 0.3 mL/min. Electrospray ionization in negative ion mode was used to quantify oleracone C and apigenin, with monitored ion m/z values of 299.0915 [M − H]− and 269.0455 [M − H]−. The linear range was established over the concentration range 10–2000 ng/mL (r = 0.9971). The limit of detection (LOD) and limit of quantification (LOQ) were 3 and 10 ng/mL for oleracone C, respectively. The RSD and RE of intra- and inter- day accuracy and precision were all less than 15%. The pharmacokinetic results indicated that oleracone C was rapidly distributed with the time to peak concentrations of 0.03 h and 0.33 h, respectively after intravenous and oral administrations and presented a low absolute bioavailability of 8.32%. This is the first study to successfully examine the pharmacokinetics of homoisoflavanone in rats' plasma after oral and intravenous administrations, using rapid, sensitive and specific UHPLC-ESI-Q-TOF/MS method.

Study on a dSPE-LC-MS/MS method for lysophosphatidylcholines and underivatized neurotransmitters in rat brain tissues

A dispersed solid phase extraction method for high performance liquid chromatography-tandem mass spectrometry analysis of lysophosphatidylcholines and underivatized neurotransmitters in rat brain tissues has been developed. Lysophosphatidylcholines (16:0, 18:0, 18:1, 20:4, 22:6), dopamine, 5-hydroxytryptamine, glutamine, dihydroxy-phenyl acetic acid, 5-hydroxyindole acetic acid and γ-aminobutyric acid were included. Dispersed solid phase extraction method was developed with the aiming to minimize the matrix effects. The cleanup procedure has been followed by rat brain homogenate, nitrogen blow drying, reconstitution, dispersive solid phase extraction and separation. Type and size of sorbent, the re-dissolving solution of the tissues, dilute solution, elution solution and the appropriate acidic or alkaline environment of the system were optimized for the purpose of obtaining a minimized matrix effect. Reversed-phase liquid chromatography was used for separation and mass spectrometry with multiple reaction monitoring was used for quantification. Electrospray ionization in negative ion mode was suitable for dihydroxy-phenyl acetic acid and 5-hydroxyindole acetic acid, while the other substances were detected in positive ion mode. The method was validated with linear range, method detection limit, limit of quantitation, matrix effects, relative recovery and the intra and inter-day precision. Linear range was at 0.1–1000 ng/mL for γ-aminobutyric acid and glutamine, 1.0–1000 ng/mL for dopamine, 10–1000 ng/mL for 5-hydroxytryptamine, 50–1000 ng/mL for 5-hydroxyindole acetic acid, dihydroxy-phenyl acetic acid and lysophosphatidylcholines. The mean matrix effect was between 52.48% and 123.12% and the CVs ranged from 0.41% to 10.96%. Mean relative recovery was from 65.17% to 114.89%, and the CVs ranged from 0.14% to 8.68% at 3 concentration levels for all compounds. Intra-day precision was with coefficients of variation between 0.20% and 14.7%. Inter-day precision values varied <9.21%, with coefficients of variation between 0.18% and 9.21%. The developed method was used to quantify lysophosphatidylcholines and underivatized neurotransmitters in healthy rat brain tissues in this study.

Simultaneous determination of bentazone and its metabolites in postmortem whole blood using liquid chromatography–tandem mass spectrometry

A liquid chromatography–tandem mass spectrometry method with solid-phase extraction (SPE) was developed and validated for the detection and quantitation of bentazone and its two hydroxylated metabolites, 6-hydroxybentazone and 8-hydroxybentazone, in postmortem blood. Sample cleanup was performed using a hydrophilic-lipophilic balanced (HLB) SPE cartridge and then separated on a C18 LC column using a gradient elution of 0.1% formic acid in distilled water and 0.1% formic acid in methanol. The identification of bentazone and its hydroxylated metabolites was performed using tandem mass spectrometry with electrospray ionization in negative ion mode with selective reaction monitoring. The retention times of bentazone, 6-hydroxybentazone, 8-hydroxybentazone, and 2-methyl-4-chlorophenoxyacetic acid (MCPA, internal standard) appeared separately in the chromatogram. The matrix effect, recovery, and process efficiency of bentazone were 75.3%, 103.6% and 77.9%, respectively. In addition, good accuracy (88.2–110.5%), precision (0.5–7.5%, bias), and linearity (5–500ng/mL) were obtained with this method. The limit of detection (LOD) of bentazone, 6-hydroxybentazone, and 8-hydroxybentazone were 0.05, 0.5, and 0.5ng/mL, respectively. The method developed herein was applied to authentic samples from three fatal cases from 2016 for the determination of the corresponding bentazone and its metabolites levels. The concentration ranges of bentazone, 6-hydroxybentazone, and 8-hydroxybentazone in the heart blood from the three victims were 46.0–91.8, 4.2–6.2, and 0.2–0.6μg/mL, respectively.

Determination of N-acetylneuraminic acid in poultry eggs by ultra performance liquid chromatography–tandem mass spectrometry

N-acetylneuraminic acid is an important member of sialic acids which is a family of nine-carbon carboxylated sugars most frequently found in terminal position in glycoconjugates. It was widely distributed in different portions of organisms. In this study, a method of ultra performance liquid chromatography–tandem mass spectrometry was developed for the determination of N-acetylneuraminic acid in poultry eggs. The N-acetylneuraminic acid was freed by heating the materials in 0.1 M H2SO4 at 80°C for 2 h. Then, chloroform reagent was used to eliminate phospholipids, cholesterol and other organic impurities, meanwhile, it was able to precipitate protein. In the cleanup step, C18 solid phase extraction columns were used to purify the matrix. Determination of N-acetylneuraminic acid was performed with electrospray ionization in negative ion mode. Chromatographic separation was performed on a Waters Acquity UPLC BEH C18 (100 × 2.1 mm, 1.7 μm) analytical column. The gradient elution reagent was acetonitrile and water (containing 0.1% formic acid). The tandem spectrometer was operated in the Multiple Reaction Monitoring mode. The linearity over of sialic acids on-column had a correlation coefficient greater than 0.999. The detection method of N-acetylneuraminic acid in the poultry eggs had good precision and acceptable recovery.

Determination of Eugenol in Aquatic Products by Dispersive Solid-Phase Extraction and Ultra-High-Performance Liquid Chromatography-Tandem Mass Spectrometry

A novel procedure, dispersive solid-phase extraction coupled with ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS), was developed for the determination of eugenol in aquatic products (shrimp, crab, and carp). Aquatic products were extracted with acetonitrile and primarily purified by dispersive solid-phase extraction with graphitized carbon black as absorbent. The pretreated acetonitrile extract was detected by UHPLC-MS/MS. UHPLC was carried out on Dikma Endeavorsil C18 (30 mm × 2.1 mm, 1.8 μm) column eluted by methanol and water (80:20 v/v) at a rate of 0.30 mL min−1. Tandem mass spectrometry was performed by electrospray ionization in negative ion mode to identify and quantify eugenol during multiple reaction monitoring. Under optimized analytical conditions, the matrix-matched spiked calibration sample demonstrates good linearity between 5.0 and 500.0 μg kg−1 with a linear regression coefficient of 0.9996. The average recovery of eugenol from aquatic products is 95.3–103.4% at spiked levels between 5 and 50 μg kg−1 with a relative standard deviation (n = 6) less than 5.4%. The limits of detection and quantification for eugenol were calculated to be 1.47 and 4.91 μg kg−1, respectively. In comparison with those reported, the proposed method has advantages in low detection limit, high recovery, and short analysis time, meeting the requirements for the determination of trace eugenol residue in aquatic products.

Role of Maturity in Controlling the Composition of Solid Bitumens in Veins and Vugs from SE Turkey as Revealed by Conventional and Advanced Geochemical Tools

Solid bitumens found in veins and cracks may have formed from once liquid petroleum by thermal chemical alteration such as maturation or by oxidative processes associated with thermochemical sulfate reduction (TSR), biodegradation, or weathering. In this study, we investigated 22 solid bitumen samples from 17 different veins in the Sirnak Province in southeast Turkey using conventional and advanced geochemical tools with respect to their formation. Southeast Turkey is located in an active collision zone from the Alpine orogeny, and compressional pressure occurred with different intensities across the region, generating an overall increase in maturation from west to east. Special focus was paid to the characterization of polar compounds containing nitrogen, sulfur, and oxygen (NSO) of high molecular weight using Fourier transform ion cyclotron resonance mass spectrometry with electrospray ionization in negative ion mode (ESI-FT-ICR-MS). The results indicate that, among possible secondary processes, thermal...

An optimized method for the accurate determination of patulin in apple products by isotope dilution-liquid chromatography/mass spectrometry.

Patulin, a mycotoxin produced by several molds in fruits, has been frequently detected in apple products. Therefore, regulatory bodies have established recommended maximum permitted patulin concentrations for each type of apple product. Although several analytical methods have been adopted to determine patulin in food, quality control of patulin analysis is not easy, as reliable certified reference materials (CRMs) are not available. In this study, as a part of a project for developing CRMs for patulin analysis, we developed isotope dilution liquid chromatography-tandem mass spectrometry (ID-LC/MS/MS) as a higher-order reference method for the accurate value-assignment of CRMs. (13)C7-patulin was used as internal standard. Samples were extracted with ethyl acetate to improve recovery. For further sample cleanup with solid-phase extraction (SPE), the HLB SPE cartridge was chosen after comparing with several other types of SPE cartridges. High-performance liquid chromatography was performed on a multimode column for proper retention and separation of highly polar and water-soluble patulin from sample interferences. Sample extracts were analyzed by LC/MS/MS with electrospray ionization in negative ion mode with selected reaction monitoring of patulin and (13)C7-patulin at m/z 153→m/z 109 and m/z 160→m/z 115, respectively. The validity of the method was tested by measuring gravimetrically fortified samples of various apple products. In addition, the repeatability and the reproducibility of the method were tested to evaluate the performance of the method. The method was shown to provide accurate measurements in the 3-40 μg/kg range with a relative expanded uncertainty of around 1%.

Determination of seven phthalate metabolites in human urine by high performance liquid chromatography-tandem mass spectrometry

A method has been developed for the analysis of seven metabolites of phthalates in human urine by high performance liquid chromatography-tandem mass spectrometry ( HPLC-MS/MS). The urine samples were hydrolyzed with glucuronidase followed by purification with solid-phase extraction (SPE) cartridges. Both 0. 1% formic acid in water (v/v) and 0.1% formic acid in acetonitrile were used as the mobile phases in a gradient mode. The chromatographic separation was achieved on a phenyl column. Mass detection was then conducted by electrospray ionization in negative ion mode and multiple reaction monitoring mode. The components were quantified by stable isotope-labelled (13C-) phthalate monoester internal standards. The calibration curves of the seven phthalates metabolites showed good linear relationships in the range of 0.2-200.0 µg/L (r > 0.999 76). The recoveries at three levels were from 88.8% to 108.9% with relative standard deviations no more than 17.05%. The limits of detection of the method were 13.43-80.2 ng/L. The limits of quantification were 44.77-267.37 ng/L. This method was successfully applied to the determination of metabolism of phthalates in human urine with efficiency, increased accuracy and high sensitivity.