Positive Chemical Ionization Mode Research Articles

A comprehensive HRMS methodology using LC-(ESI)-/GC-(APCI)-QTOF MS complementary platforms for wide-scope target screening of >750 pesticides in olive oil.

This study presents the development and validation of a comprehensive high-resolution mass spectrometry (HRMS) methodology for the detection of 771 pesticides in olive oil, using liquid chromatography with electrospray ionization, operating in positive and negative mode, and gas chromatography with atmospheric-pressure chemical ionization in positive mode, both coupled to quadrupole-time-of-flight mass spectrometry (LC-(ESI)-/GC-(APCI)-QTOF MS). Special reference is made to the post-acquisition evaluation step, in which all LC/GC-HRMS analytical evidence (i.e. mass accuracy, retention time, isotopic pattern, MS/MS fragmentation) is taken into account in order to successfully identify the compounds. The sample preparation of the method involves a QuEChERS-based protocol, common for both techniques, differentiated only on the reconstitution step, making the method highly applicable in routine analysis. A smart evaluation of method's performance was carried out, with 65 representative analytes comprising the validation set. The method was validated in terms of linearity, accuracy, matrix effect and precision, while the limits of detection and quantification of the method were estimated. Finally, twenty Greek olive oil samples were analysed in both analytical platforms and the findings included the pesticides lambda-cyhalothrin, chlorpyrifos, phosphamidon, pirimiphos-methyl and esprocarb at low ng g-1 level.

Detection of some synthetic cannabinoids using GC-PCI-MS/MS: Comparison between isobutane and ammonia as reagent gases

This study was conducted to investigate the ionization and fragmentation behavior of some synthetic cannabinoids (SCs) by examining the formation of their product ions using reagent gases having different proton affinities. Ammonia (NH3) and isobutane (i-C4H10) were employed as reagent gases in positive chemical ionization (PCI) mode using gas chromatography-tandem mass spectrometry (GC-PCI-MS/MS) to qualitatively detect SCs. Under usual operational conditions, the intensity of responses in terms of either ion abundances or peak areas obtained for protonated molecules is significantly influenced by the reagent gases. Ammonia produced two to three times greater responses than isobutane. Additionally, the results showed that the NH3–CI and i-C4H10–CI spectra do not contain the adduct ions for these SCs.

The use of gas chromatography – high resolution mass spectrometry for suspect screening and non-targeted analysis of per- and polyfluoroalkyl substances

This study is a workflow development for the analysis, identification, and categorization of per- and polyfluoroalkyl substances (PFAS) using gas chromatography-high resolution mass spectrometry (GC-HRMS) with non-targeted analysis (NTA) and suspect screening techniques. The behavior of various PFAS in a GC-HRMS was studied with regards to retention indices, ionization susceptibility, fragmentation patterns, etc. A custom PFAS database was constructed from 141 diverse PFAS. The database contains mass spectra from electron ionization (EI) mode, as well as MS and MS/MS spectra from positive and negative chemical ionization (PCI and NCI, respectively) modes. Common fragments of PFAS were identified across a diverse set of 141 PFAS analyzed. A workflow for suspect screening of PFAS and partially fluorinated products of incomplete combustion/destruction (PICs/PIDs) was developed which utilized both the custom PFAS database and external databases. PFAS and other fluorinated compounds were identified in both a challenge sample (designed to test the identification workflow) and incineration samples suspected to contain PFAS and fluorinated PICs/PIDs. The challenge sample resulted in a 100% true positive rate (TPR) for PFAS which were present in the custom PFAS database. Several fluorinated species were tentatively identified in the incineration samples using the developed workflow.

Sequential Extraction and Characterization of Nitrogen Compounds after Hydrothermal Liquefaction of Sewage Sludge.

Organic solid wastes such as sewage sludge are potential feedstocks for the production of drop-in biofuels. Hydrothermal liquefaction (HTL) is a process that converts the wet sewage sludge into an organic biocrude. To fulfill industrial fuel standards, the considerable heteroatom content of the biocrude needs to be lowered by downstream processes. Nitrogen (N) contained in several compounds poses a challenge and yet, the complex chemical composition of HTL-biocrude samples has hindered detailed analysis and understanding. In particular, N-containing aromatic substances appear very persistent in biocrude. In the present work, two alkaline (NaHCO3 and NaOH) and one acidic (HCL) aqueous solutions were subsequently applied to extract and recover polar N-containing compounds from the biocrude matrix with an N-content of 3.8 wt %. Gas chromatography-mass spectrometry, atmospheric pressure chemical ionization in positive mode, and Fourier transform ion cyclotron resonance mass spectrometry were applied for their characterization and results show that a large share of N-compounds with an aromatic, pyridinic structure was found in the acidic extracted fraction with an N-content of 9.5 wt %. Aliphatic N-compounds were less affected by the separation and ended in the residual fraction. N-compounds with multiple oxygen functionalizations are enriched in the alkaline extracted fractions. This showed that N-compounds with an aromatic structure are strongly affected by polar groups and can potentially be extracted by downstream processes with appropriate solvents.

Rapid assessment of fatty acyls chains of phospholipids and plasmalogens by atmospheric pressure chemical ionization in positive mode and high-resolution mass spectrometry using in-source generated monoacylglycerol like fragments intensities

We recently published a new concept using monoacylglycerol-like fragments [MG+H-H2O]+ (ions B) produced in-source by atmospheric pressure photoionization in positive mode and high-resolution mass spectrometry for the determination of the fatty acyl (FA) composition of triacylglycerols (TGs) from plant oils. This study extends the concept to the phospholipids (PLs) category and shows that the APCI+ source can also be used. Moreover, the coupling with NP-LC allows to simultaneously analyze different PLs classes in the same sample. We compared the relative intensities of the ions B produced in-source to the % composition of FAs determined by GC-FID. In the case of PLs from natural extracts composed exclusively of diacyl-PLs, the relative intensities of ions B are close to the % of the FAs obtained by GC-FID. This approach is not directly useable for extracts containing plasmalogens (P-PLs). For these PLs, acidic hydrolysis by HCl fumes allows hydrolyzing selectively vinyl ether functions to form lyso-PLs. The analysis of hydrolyzed extracts makes it possible to obtain the composition of P-PLs FAs thanks to the lyso-PLs thus formed, while the diacyl-PLs composition remains unchanged. Unlike GC-FID FAs determination, this approach allows a distinction between the diacyl-PLs and P-PLs FAs composition. We also found that the ion B intensities were consistent among the PL classes (PG, PE, PA, PI, CL, PS and PC) and lyso- forms (LPE and LPC). In the case of the diacyl-PLs extracts analyzed, no statistically significant differences were found between the PLs FAs compositions calculated from ion B intensities and the corresponding GC-FID data. A weighting coefficient was applied to correct ion B intensities issued from polyunsaturated FAs with three or more double bonds. The fatty alkenyls composition of P-PLs could also be calculated from the % intensities of specific ions.

Development of an analytical method for the determination and quantification of n-nitrosodimethylamine in olmesartan by HPLC-MS/MS

In this study, a simple, rapid, and highly sensitive analytical method has been developed and validated for the detection, separation, and quantification of N-nitrosodimethylamine in the active pharmaceutical ingredient olmesartan medoxomil, as well as in manufactured tablets and marketed tablets, using high-performance liquid chromatography-mass spectrometry. Chromatographic separation was achieved using the Agilent Eclipse XDB-C18 column (5 m × 4.6 mm × 150 mm) with a binary gradient with water as mobile phase A and 0.1 % formic acid in methanol as mobile phase B, flow rate 0.5 mL/min, B. Due to the presence of polar groups, N-nitrosodimethylamine is successfully ionized and quantified in positive atmospheric pressure chemical ionization mode using multiple reaction monitoring. The method was validated according to International Conference on Harmonization of Technical Requirements for Registration of Pharmaceuticals for Human Use guidelines, evaluating the limit of detection and quantification, a good signal-to-noise ratio, and an excellent regression coefficient greater than 0.995 were found. The accuracy (expressed as recovery) of the method was performed in triplicate obtaining satisfactory results between 80 and 104 %, with a precision (%RSD) of 0.34 – 1.50 %. The method can be used routinely for the determination and quantification of N-nitrosodimethylamine in olmesartan.

Determination of unbound piperaquine in human plasma by ultra-high performance liquid chromatography tandem mass spectrometry

Piperaquine (PQ) is an antimalarial drug that is highly protein-bound. Variation in plasma protein contents may affect the pharmacokinetic (PK) exposure of unbound drug, leading to alteration of clinical outcomes. All published methods for determination of PQ in human plasma measure the total PQ including both bound and unbound PQ to plasma proteins. There is no published method for unbound PQ determination. Here we report an ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) method for determination of PQ in human plasma filtrate prepared by filtering human plasma through Millipore Microcon® centrifugal filters (10k NMWL). The filter cup had to be treated with 5% benzalkonium chloride to reduce non-specific binding to the filter devices before filtration of plasma samples. Multiple reactions monitoring (MRM) of the ion pairs m/z 535/288 for PQ and m/z 541/294 for the internal standard (IS) was selected for quantification. When electrospray ionization (ESI+) was used, paradoxical matrix effect was observed despite the structure similarity of the deuterated IS: Ion suppression for PQ versus ion enhancement for the PQ-d6, even though they were closely eluted: 0.62 min versus 0.61 min. Separation was achieved on Evo C18 column (50 × 2.1 mm, 1.7 μm, Phenomenex Inc.) eluted with 10 mM NH4OH and MeCN. When atmospheric pressure chemical ionization in positive mode (APCI+) was used for ion source, matrix effect diminished. Separation was achieved on a PFP column (30 × 2.1 mm, 1.7 μm, Waters, Corp.) eluted with aqueous 20 mM ammonium formate 0.14% trifluoroacetic acid (A) and methanol-acetonitrile (4:1, v/v) containing 0.1% trifluoroacetic acid (B) at 0.8 mL/min flow rate in a gradient mode: 30–30–80–80–30–30%B (0–0.1–1.0–1.40–1.41–1.50 min). The retention time was 0.67 min for both PQ and the IS. The method was validated with a linear calibration range from 20 to 5,000 pg/mL and applied to clinical samples.

Measurement of Urinary Free Cortisol and Cortisone by LC-MS/MS.

Monitoring urinary free cortisol (UFC) excretion helps assess adrenal function and is used to screen for endogenous Cushing's syndrome caused by an adrenal or pituitary tumor. While serum cortisol levels fluctuate in response to time of day, stress, and concentrations of cortisol-binding globulin (CBG), a 24-h urine collection measures the cortisol produced over the entire day and does not suffer from as much variability as a serum measurement.We describe here a method of measurement of urinary free cortisol (UFC) and cortisone using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Urine samples, combined with stable isotope-labeled internal standards, are extracted by liquid-liquid extraction using ethyl acetate and hexane. An API 5500 mass spectrometer operated in positive atmospheric pressure chemical ionization (APCI) mode is used for detection.

An LC-APCI+-MS/MS-based method for determining the concentration of neurosteroids in the brain of male mice with different gut microbiota

BackgroundAlthough the interaction between the gut microbiota and central nervous system (CNS) is well-known, the effects of gut microbiota on different brain regions remain obscure. New methodIn present study, we developed a simple and sensitive high-performance liquid chromatography-tandem mass spectrometry with atmospheric pressure chemical ionization in positive mode (LC-APCI+-MS/MS) for simultaneous detection of 12 analytes in the rodent’ brain with different housing conditions ResultsThe results showed that male mice in XZ group had significantly higher brain levels of dehydroepiandrosterone (DHEA), androstenedione (A4), testosterone (T), progesterone (P), corticosterone (CORT), aldosterone (ALD) and 11-dehydrocorticosterone (11-DHC) than those in SPF group. CORT level was higher in the left prefrontal cortex, whereas ALD and 11-DHC levels were higher in the left hypothalamus than in the right symmetrical areas in both groups. DHEA and CORT levels were highest in the striatum than in the prefrontal cortex, hippocampus, hypothalamus, regardless of the region and group (XZ and SPF). Comparison with existing methodsThese results demonstrated that the method developed in this study provides, for the first time, direct quantitation of neurosteroids in male mice brain. ConclusionsDHEA levels showed a left-lateralized pattern in the hippocampus and hypothalamus. Mice in the XZ group showed significantly elevated levels of CORT and/or its metabolites, ALD and 11-DHC in brain than mice in the SPF group. Insanitation living conditions increased more diverse gut microbiota.

Advances in the development of detection techniques for organophosphate ester flame retardants in food

Organophosphate ester (OPE)-based flame retardants and plasticizers are widely utilized in various industrial products, and are being increasingly used as substitutes for gradually phased brominated flame retardants (BFRs). According to the different types of substituents used, OPEs are mainly divided into alkyls, halogenated compounds, and aromatics, which have widely varying physicochemical properties. OPEs can induce neurotoxicity, carcinogenicity, and damage in endocrine and reproductive systems in humans. Examples of halogenated OPE are tris(2-chloroisopropyl) phosphate (TCIPP) and tris(1,3-dichloropropyl) phosphate (TDCIPP), which are suspected to be carcinogenic. OPEs have emerged as pollutants in environmental and food matrices as a result of volatilization and abrasion processes. Due to its low content in the food matrix and serious background interference, there is a lack of reliable and sensitive analytical methods. Recently, there has been a focus on the detection of OPE flame retardants in food. In this paper, we have reviewed the current status and development trends of OPE detection methods in various foodstuffs. First, the physicochemical properties of more than 30 common OPEs were summarized. Even when using the same extraction solvent, there are obvious differences in extraction efficiency according to different compound properties. To simultaneously analyze multi-component OPE flame retardants in food, it is very important to choose the appropriate extraction solvent to meet the required extraction efficiency of compounds with a wide range of polarities. In addition, although OPE flame retardants are not easily hydrolyzed under neutral conditions, they will degrade to a certain extent under strong acidic and alkaline conditions. It is worth mentioning that avoiding the removal of lipids and other interferences in food matrices under strong acidic and alkaline conditions. Different pretreatment methods, such as accelerated solvent extraction, matrix solid-phase dispersion extraction, microwave-assisted extraction, ultrasonic-assisted extraction, QuEChERS, solid-phase extraction, gel permeation chromatography, and dispersive solid-phase extraction are also compared. Combining the advantages of ultrasonic assisted extraction (UAE) and QuEChERS pretreatment technology can reduce the waste of extraction solvent and internal standard solution. For lipid-rich matrices like biological samples, it is necessary to remove lipid interference by SPE columns or GPC purification. Furthermore, the characteristics of separation and detection techniques, such as GC, GC-MS/MS, and LC-MS/MS, are discussed. Comparing detection limits and recovery data with those reported in the literature, GC-MS/MS can provide improved selectivity, precision, and limits of detection in complex food matrices, but LC-MS often suffers from ion suppression, matrix interferences, and incomplete separation of some OPEs. Since electron impact (EI) has higher ionization efficiency, it produces many fragment ions, thus creating a more complete spectral library, which is conducive to structural identification. When using GC-MS/MS to determine OPE flame retardants, the EI mode was usually used. However, positive chemical ionization (PCI) and electron capture negative ionization (ECNI) modes were also used sometimes. In the section on quality control, the main sources of standards and internal standards, possible sources of blank contamination, and the research status of measures to reduce matrix effects have been reviewed. To avoid blank contamination, all the laboratory equipment should be carefully cleaned, heated at high temperatures, and rinsed with polar or non-polar organic solvents in order to remove all interfering organic residues. Isotopically labeled internal standard and isotopic dilution mass spectrum quantification methods are used to reduce matrix effects. Owing to the limited availability of commercial standards and the relatively high cost, alternative approaches, such as matrix-matched calibration or standard addition methods, are required. The screening and identification of unknown metabolites of OPEs and related analytical methods based on high resolution mass spectrometry could also be studied for precursor OPEs in foodstuffs in the future.

Selective, rapid and simultaneous determination of ergosterol and ergocalciferol in mushrooms by UPLC-Q-TOF-MS

An ultra-performance liquid chromatography coupled to atmospheric pressure chemical ionization-quadrupole time-of-flight mass spectrometry method has been optimized and validated for the determination of ergosterol and ergocalciferol in mushroom samples, using cholecalciferol as surrogate standard.The separation was carried out with a Synergi Hydro-RP column (100 mm x 3.00 mm i.d, 2.5 μm particle size), (Phenomenex, CA, USA) column, thermostated at 35 °C. The mobile phase was 0.1 % formic acid aqueous solution and methanol in gradient elution mode and it was achieved in 5 min approximately. Detection was achieved by atmospheric pressure chemical ionization in positive mode and quadrupole time-of-flight mass spectrometry. Desolvation and interface temperatures were set at 500 °C and 150 °C, respectively. The recoveries obtained were within 92–105 % for ergosterol, 77–81 % for ergocalciferol and 83–87 % for cholecalciferol. Method limits of detection were 0.4 and 0.5 μg g−1 for ergosterol and ergocalciferol, respectively, and method limits of quantitation were 1.2 and 1.3 μg g−1 for ergosterol and ergocalciferol, respectively.A rapid and simple extraction procedure using small amount of sample (100 mg) with hexane was optimized and the method was applied to the determination of ergosterol and ergocalciferol in white button mushrooms (Agaricus bisporus var. bisporus) exposed to UV irradiation. Results were compared to the corresponding non-irradiated mushrooms.

LC-APCI+-MS/MS method for the analysis of ten hormones and two endocannabinoids in plasma and hair from the mice with different gut microbiota

The effect of gut microbiota on the activity of the HPA and HPG axes and ECS is a short-term or long-lasting process remains unclear in rodents. However, the extant studies focused only on its short-term effect on the HPA activity because there is lack of reliable biomarkers characterizing short-term activity of the HPG axis and ECS and long-term activities of the three endocrine systems. The endogenous levels of aldosterone (ALD), 11-dehydrocorticosterone (11-DHC), estradiol (E2), estrone (E1), androstenedione (A4), dihydrotestosterone (DHT), corticosterone (CORT), dehydroepiandrosterone (DHEA), testosterone (T), progesterone (P), N-arachidonoyl ethanoamide (AEA) and 1-arachydonoyl glycerol (1-AG) in hair and plasma are the potential long-term and short-term biomarkers of the three systems. This study aimed to develop the sensitive and selective methods for simultaneous quantitation of the twelve compounds in rodent’s hair and plasma. Then the methods were used to explore the differences in the hair levels of the twelve compounds between the mice in XZ group possibly having gut microbiota with more diversity and SPF group possibly having gut microbiota with less diversity and the inter-group differences in the plasma levels in the response to 1-h restraint stress. The methods were based on high performance liquid chromatography tandem mass spectrometry with atmospheric pressure chemical ionization in positive mode. The methods were adopted for 20 mg hair and 100 μL plasma, respectively. Hair samples were incubated in methanol at 40 ℃ for 24 h, and were performed by solid phase extraction. Plasma samples were implemented by liquid-liquid extraction with ethyl acetate. The methods showed limit of quantification at 0.06–1.3 pg/mg and 0.03-0.6 ng/mL and recovery ranging between 87.7–115.1 % and 86.1–114.6 % for all compounds in rodent’s hair and plasma, and the intra-day and inter-day coefficients of variation less than 15 %, and good freeze/thaw and short-term stability. The present methods also had good reliability as demonstrated by the sex difference in the testosterone levels in hair and plasma. The inter-group comparison revealed that the mice in XZ group showed significantly higher hair levels than those in SPF group for 1-AG and most of hormones except for T and P. The non-stressed female mice in SPF showed significantly higher plasma levels than those in XZ for AEA and most of hormones except for E2, A4, DHT, T and 1-AG, but there were no inter-group differences for the stressed mice except for DHEA and 11-DHC and for the non-stressed male mice. Additionally, the stressed mice showed significantly higher corticosterone level in plasma than controls for male and female mice in XZ and male mice in SPF, but it was not true for female mice in SPF.

Gas chromatography-tandem mass spectrometry-based detection of half nitrogen mustards in plasma as a new biomarker of nitrogen mustard exposure.

The development and optimization of an analytical method for the detection and identification of reactive metabolite of organochlorine chemical warfare agent nitrogen mustards (NMs), 2-[(2-chloroethyl)(alkyl)amino]ethanol (CEAAE), known as half nitrogen mustard, in blood samples is presented, herein. In this study, half nitrogen mustards in plasma are presented as a new and unambiguous biomarker of NM exposure since the fully hydrolyzed product, i.e., amino alcohols, are common industrial chemicals that can be present as such without getting exposed to NMs. Thus, the detection of half nitrogen mustard as a biomarker holds great significance for verification by the Chemical Weapon Convention (CWC) and will also be helpful in understanding the pharmacokinetics of NM-based chemotherapeutic pro-drugs. To the best of our knowledge, this is the first report on the detection of half nitrogen mustards in any matrice, including plasma. A very simple sample preparation protocol was developed for its extraction from plasma samples. Heptafluorobutyrylation and gas chromatography-tandem mass spectrometry in the positive chemical ionization mode were developed for the detection and identification of halfNMs. The developed method has shown excellent analytical figures of merits such as a wide range of linearity (1.0-50 ng mL-1), low limit of detection (0.3-0.5 ng mL-1), and low limit of quantification (1.0 ng mL-1). The interday and intraday reproducibilities were also less than 15%. The developed method was successfully applied to real-world samples; in vitro human plasma was spiked with ∼1 ng mL-1 of all the NMs and in vivo studies were done with rats intravenously exposed to 1 × LD50 of bis(2-chloroethyl)methylamine (HN2).

A reference isotope dilution headspace GC/MS method for the determination of nitrite and nitrate in meat samples

SummaryA novel method for the determination of nitrite and nitrate in meat products is presented. The samples were ground and extracted in hot water with the presence of and internal standards. The solution was buffered with sodium bicarbonate and reacted with triethyloxonium tetrafluoroborate to convert nitrite and nitrate into EtNO2 and EtONO2. Such derivatives could be detected by headspace GC/MS in positive chemical ionisation mode with 0.05 µg g−1 and 1.0 µg g−1 LOD. The method was used for and quantitation in the 0.5‐300 and 2.5‐300 µg g−1 ranges. The method was applied for the analysis of fifteen meat products. Despite minimal sample preparation, the headspace sampling ensured a clean chromatography for over 135 analyses (throughput ten samples per hour). The proposed method offers selective GC/MS detection combined with high‐precision isotope dilution calibration, it is suitable for metrological applications and can support regulations on meat safety (European Commission, 2011).

Analytical methods to access the chemical composition of an Euphorbia tirucalli anticancer latex from traditional Brazilian medicine

Ethnopharmacological relevanceEuphorbia tirucalli L. is widely used by Brazilian folk medicine, mainly for its anticancer activity. However, its commercialization was banned by The Brazilian National Sanitary Surveillance Agency (ANVISA) due to the presence of some compounds considered toxic, such as the diterpene esters.Aim of the study: Chemical and biological analyses were performed with the Brazilian Euphorbia tirucalli latex to support its wide traditional use in Brazil. Material and methodsLatex was collected by using two procedures, in a solution of dichloromethane: methanol (3:1, 100 mL) and in 100 mL of distilled water. The first procedure was concentrated as a crude extract and the second one was partitioned with hexane and dichloromethane. The partitions and crude extract were subjected to phytochemical analyses using three different methods: Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS) with electrospray ionization sources in negative mode (ESI(−)) as well as in tandem mass spectrometry ESI(−) MS/MS and Atmospheric Pressure Chemical Ionization in positive mode (APCI(+)), Gas Chromatography coupled Mass Spectrometry (GC-MS) and Nuclear Magnetic Resonance (NMR) (1H-NMR and 13C-NMR). The cytotoxic potential was evaluated using the crude extract in macrophages RAW 264.7 and Gastric Adenocarcinoma (AGS) cancer cells. The evaluation of immunomodulatory activity was made through the detection of Nitric Oxide (NO) and cytokines as Tumor necrosis factor α (TNF-α) and Interleukin-6 (IL-6). ResultsGC-MS showed the presence of some esters of fatty acids, for instance myristic, palmitic, stearic, oleic and linoleic acid and, mainly, triterpenes such as euphol and tirucallol. With NMR, most of the signals were related to triterpenoids euphol and tirucallol. However, when the latex was analyzed with ESI(−) FT-ICR MS, a wide variety of molecules from different classes of natural products (fatty acids, diterpenes, triterpenes, steroids) were found. On the other hand, when APCI(+)FT-ICR MS was used, the ion M+. At ratio mass-charge (m/z) 426.38567, related to triterpenes euphol and tirucallol masses, presented the most intense peak, with a mass error of −0.11, indicating high accuracy. Diterpene esters from 4-deoxyphorbol and ingenol were identified only by ESI(−)FT-ICR MS and ESI(−)FT-ICR MS/MS. When evaluated biologically, the crude latex showed immunomodulatory activity, as it reduced the production of the pro-inflammatory cytokines TNF-α, IL-6 and NO, and the effect on NO reduction was more significant, obtaining in a similar result to the N(ω)-Nitro-L-Arginine Methyl Ester (L-NAME) standards, as well as significant cytotoxic activity with half inhibitory concentration (IC50) values of 69.43 ± 1.29 μg/mL against AGS without damaging healthy ones. ConclusionIt was verified that the Brazilian Euphorbia tirucalli latex consists mainly of the triterpenes euphol and tirucallol, which may be the main cause of the anticancer activity attributed to the plant, but many other minor compounds could have been determined by the FT-ICR MS method, such as the diterpene esters. It has antitumor potential because it acts selectively against cancer cells and it also prevents the progression of tumors, because it carries an important immunomodulatory effect.

Simultaneous quantitation of zidovudine, efavirenz, lopinavir and ritonavir in human hair by liquid chromatography-atmospheric pressure chemical ionization-tandem mass spectrometry

Nowadays, zidovudine, efavirenz, lopinavir and ritonavir are important components of the second-line antiretroviral therapeutic regimen of National Free Antiretroviral Treatment Program in China. The measurement of antiretroviral drugs in hair will facilitate for the evaluation of the long-term adherence to highly active antiretroviral therapy. Nevertheless, no study illustrated simultaneous quantitation of the four drugs in hair. The study intended to develop a simple, sensitive and selective method for simultaneous quantitation of the four drugs in hair. The detection employed high liquid chromatography tandem mass spectrometry with atmospheric pressure chemical ionization in positive mode. Hair samples were incubated in methanol at 40 °C for 16 h. The method showed the limit of detection at 18, 8, 5 and 6 pg/mg for zidovudine, efavirenz, lopinavir and ritonavir, respectively. The linear range (R2 > 0.99) was 36–5000 pg/mg for zidovudine, 16–5000 pg/mg for efavirenz, 10–50,000 pg/mg for lopinavir and 12–12,500 pg/mg for ritonavir. The intra-day and inter-day coefficients of variation were <15% and the recovery varied from 88.1 to 110.5%. The population analysis revealed that patients with high adherence showed significantly higher drug concentrations in hair than those with low adherence for both AZT and EFV (ps < 0.05). There was high association in drug contents in hair between AZT and EFV or LPV and RTV (ps < 0.05).

Application of supercritical fluid chromatography coupled to mass spectrometry to the determination of fat-soluble vitamins in selected food products

In the present manuscript, we describe a fully optimized and validated method suitable to analyse nine compounds (retinyl acetate, retinyl palmitate, retinol, α-tocopherol, α-tocopheryl acetate, cholecalciferol, ergocalciferol, phylloquinone, menaquinone-4) representing the major contributors to the fat-soluble vitamin activity of selected food products (infant formulas, adult nutritionals, infant cereals and mixed meals). Sample preparation involves direct solvent extraction using enzyme-assisted matrix disintegration and methanolic protein precipitation. Direct injection of the extract allows quantification of vitamins A, E and K in only 7 min, while vitamin D is determined after fast derivatization of the extract. Separation is achieved by supercritical fluid chromatography and detection performed by tandem mass spectrometry in positive Atmospheric Pressure Chemical Ionization mode. Results on a Standard Reference Material (SRM 1849a Infant/Adult Nutritional) were not statistically different from reference values. Full validation of the method showed excellent overall performance. Average recovery rate was between 90 and 110% for all vitamins and matrixes. The methodology shows enhanced safety and reduced cost as compared with previously published methods, together with potential for application to more complex matrixes. The full procedure can be easily applied in control laboratories dramatically increasing sample throughput and reducing solvent consumption.

Rapid analysis of forensic-related samples using two ambient ionization techniques coupled to high-resolution mass spectrometers.

This paper highlights the versatility of interfacing two ambient ionization techniques, Laser Diode Thermal Desorption (LDTD) and Atmospheric Solids Analysis Probe (ASAP), to high-resolution mass spectrometers and demonstrate the method's capability to rapidly generate high-quality data from multiple sample types with minimal, if any, sample preparation. For ASAP-MS analysis of solid and liquid samples, the material was transferred to a capillary surface before being introduced into the mass spectrometer. For LDTD-MS analysis, samples were solvent extracted, spotted in a 96-well plate, and the solvent was evaporated before being introduced into the mass spectrometer. All analyses were performed using Atmospheric Pressure Chemical Ionization in positive mode. Seven consumer "Spice" packets were combined and analyzed by both ASAP and LDTD, which identified 11 synthetic cannabinoids/cathinones by full MS and MS/MS experiments. To further show the usefulness of these techniques, black tar heroin was analyzed, which resulted in the identification of heroin and its impurities (monoacetylmorphine, papaverine, and noscapine). These experiments were performed on the LTQ-Orbitrap to demonstrate the ability to perform both parallel and serial MS and MSn experiments. Interfacing LDTD and ASAP to high-resolution mass spectrometers allows for expeditious analysis of a wide range of samples, with minimal or no sample preparation. Both allow for rapid full scan, MS/MS, and/or MSn experiments from a single sample introduction. Published in 2017. This article is a U.S. Government work and is in the public domain in the USA.

Formation of Haloacetonitriles, Haloacetamides, and Nitrogenous Heterocyclic Byproducts by Chloramination of Phenolic Compounds.

The potential formation of nitrogenous disinfection byproducts (N-DBPs) was investigated from the chloramination of nitrogenous and non-nitrogenous aromatic compounds. All molecules led to the formation of known N-DBPs (e.g., dichloroacetonitrile, dichloroacetamide) with various production yields. Resorcinol, a major precursor of chloroform, also formed di/trichloroacetonitrile, di/trichloroacetamide, and haloacetic acids, indicating that it is a precursor of both N-DBPs and carbonaceous DBPs (C-DBPs) upon chloramination. More detailed experiments were conducted on resorcinol to understand N-DBPs formation mechanisms and to identify reaction intermediates. Based on the accurate mass from high resolution Quadrupole Time-of-Flight GC-MS (GC-QTOF) and fragmentation patterns from electronic impact and positive chemical ionization modes, several products were tentatively identified as nitrogenous heterocyclic compounds (e.g., 3-chloro-5-hydroxy-1H-pyrrole-2-one with dichloromethyl group, 3-chloro-2,5-pyrroledione). These products were structurally similar to the heterocyclic compounds formed during chlorination, such as the highly mutagenic MX (3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone) or halogenated pyrroles. To our knowledge, this is the first time that the formation of halogenated nitrogenous heterocyclic compounds is reported from chloramination process. The formation of these nitrogenous byproducts during chloramination might be of concern considering their potential toxicity.

Technical note: Analytical refinements of the methane indicator archaeol in bovine feces, rumen fluid, and feedstuffs.

Archaeol (1,2-di-O-phytanyl-sn-glycerol) is a cell membrane lipid component of methanogens that has the potential to be used as a biomarker for methane production in ruminants. However, its analysis via gas chromatography-mass spectrometry (GC-MS) is challenging because of its molecular size and structure. In this study, 2 different sample preparation methods were tested, Soxhlet and sonication-aided extraction, and the methods were compared for extraction efficiency using the internal standard (IS; 1,2-di-o-hexadecyl-rac-glycerol). The extraction efficiency of the Soxhlet method for fecal archaeol was twice that of sonication. With the use of a high-temperature GC column, the retention times of IS and archaeol were 17.6 and 19.4 min, respectively, with a total run time of only 25 min. The molecule ions m/z 611.4 (IS) and m/z 725.8 (archaeol), or alternatively the fragment ion of the glycerol moiety m/z 130.0, were used for identification and quantification via GC-MS in positive chemical ionization mode. The intra-assay coefficients of variation for fecal archaeol measurements were 1.3% (m/z 725.8) and 2.1% (m/z 130.0) (n=3), respectively. Fecal archaeol quantifications did not differ between the use of the molecule or glycerol moiety ions (paired t-test, n=156). Archaeol concentrations tended to be 3.3% greater in samples stored at -20°C before drying compared with samples that were immediately dried after collection (paired t-test, n=5). The detection limit of archaeol was 0.5 µg/g of fecal dry matter (DM); no archaeol could be detected in feed samples. In different fractions of rumen fluid, archaeol levels ranged from 1.9 to 24.0 µg/g of DM. In 10 cows fed the same grass and corn silage/hay-based ration, diurnal variations of fecal archaeol levels (5 time points over 2 d) were cow dependent and ranged from 26.2 to 77.2 µg/g of DM (mean 48.4 µg/g of DM). Thus, within-animal variation in cows on the same diet was between 4 and 27%. We suggest that this finding is related to the amount and time of the latest feed intake event before the fecal sampling. Feeding pattern can determine the passage rate of digesta through the alimentary tract and thus the duration of contact time of archaea with their substrate.