Identification and in vitro antioxidant activities of phenolic compounds isolated from Cynoglossum cheirifolium L.

In an extensive search for bioactive compounds from plant sources, the quantitative and qualitative characterisation of the compounds present in Cynoglossum cheirifolium extracts was studied. Total phenolic and flavonoid contents were determined by spectrophotometric techniques. In vitro antioxidant and radical scavenging profiling was determined through DPPH^? scavenging activity and Ferric reducing antioxidant power (FRAP). Our study showed that leaves produce more phenolic compounds, followed by flowering aerial part. The butanolic fraction obtained from leaves extract exhibited the highest total phenolics (78.65 ± 3.58 mg GAE/g DW) and flavonoids (22.15 ± 4.66 mg CE/g DW). In contrast, this fraction displayed the highest DPPH^? scavenging ability with IC₅₀ values of 0.06 ± 0.003 mg/mL. The RP-HPLC-PDA analysis of phenolic compounds from leaves of C. cheirifolium lets to identify: rosmarinic acid, ferulic acid, caffeic acid, p-coumaric acid, syringic acid, sinapic acid and rutin. The obtained results indicate that this plant represent a valuable source of natural antioxidants.     

Ethanolic extracts of Moringa oleifera Lam.

This paper reports the evaluation of the antioxidant potential of the ethanolic extracts of the leaves (EL), flowers (EF), seed pods (EP) and seeds (ES) from Moringa oleifera Lam. The antioxidant potential was assessed, upon the addition of the extracts to fish oil, by means of the total extractable phenol content (TEP), the DPPH^· free radical scavenging efficiency and using pressurized differential scanning calorimetry (P-DSC). The results of TEP and DPPH^· showed that the ES extract does not present a potential to be used as an antioxidant additive, and it was thus discarded from the remaining analyses. Thus, the following treatments were prepared: pure fish oil, fish oil with BHT (100 mg kg^?1), fish oil with TBHQ (100 mg kg^?1) and fish oil with EL, EF and EP—all at the concentration of 100 mg kg^?1, in relation to the total extractable phenolics contained in each one of the extracts. The leaf and flower extracts displayed a protecting effect, with an increase in about 20 and 11 % of the OIT values, respectively. However, such protection was smaller than that conferred by the synthetic antioxidants utilized. As for the thermal analysis results, it was noticed that EL presented the highest thermal stability among the extracts.     

Simultaneous Determination of Testosterone and Testosterone Enanthate in Equine Plasma by UHPLC-MS-MS

Testosterone and testosterone enanthate are performance-enhancing substances that are banned in racehorses competing in the State of Pennsylvania (PA). A tolerance concentration of 2,000 pg mL^?1 plasma has been established for testosterone in intact colts and stallions at the time they are competing in PA. Testosterone enanthate is a precursor of testosterone and can be used to boost plasma testosterone concentration above natural, age and seasonally variable plasma concentration. To control abuse, a verifiable method for rapid determination of both substances in equine plasma was needed. For this reason, an ultra high performance liquid chromatography-tandem mass spectrometry method for high-throughput analysis of both analytes in equine plasma was developed. Analytes were recovered from plasma by liquid–liquid extraction using mixture of methyl tert-butyl ether and ethyl acetate (50:50, v/v), separated on a C₁₈ sub-2 μm column and detected on a triple quadrupole mass spectrometer using positive electrospray ionization mode with selected reaction monitoring scan. SRM ion transitions of m/z 289 → m/z 97, m/z 289 → m/z 109, m/z 289 → m/z 79 were used for testosterone identification while m/z 401 → m/z 253, m/z 401 → m/z 271, m/z 401 → m/z 97 were employed for testosterone enanthate. Retention time and product ion intensity ratio were used as confirmation criteria to ascertain the presence of both analytes in equine plasma. The limits of detection, quantification and confirmation were 50 pg 0.5 mL^?1, 100 pg 0.5 mL^?1 and 250 pg 0.5 mL^?1, respectively for both analytes. The method was validated for recovery efficiency, sensitivity, matrix effect, linearity, precision and accuracy. This method is routinely used in the PA program for androgenic anabolic steroids doping control in racehorses and in the on-going testosterone enanthate pharmacokinetics study. The method is defensible, fast, selective, specific and reproducibly reliable.     

LC�CMS�CMS Quantitative Determination of Brivudine in Human Plasma and Its Application to Pharmacokinetic Studies

A sensitive and specific liquid chromatography?Celectrospray ionization?Ctandem mass spectrometry method has been developed and validated for the identification and quantification of brivudine in human plasma using diclofenac as an internal standard. The method involves extraction with ethyl acetate. The analyte was separated on a C₁₈ column and analyzed in multiple reaction monitoring mode with a negative electrospray ionization interface using the [M?CH]^? ions, m/z 332.8??m/z 80.9 for brivudine, m/z 293.6??m/z 249.5 for diclofenac. The method was validated over the concentration range of 5.54?C2,836 ??g L^?1 for brivudine. The intra-and inter-day precisions were less than 8.91% in terms of relative standard deviation (RSD), and the accuracy was within ?4.22% in terms of relative error (RE). The lower limit of quantification (LLOQ) was 5.54 ??g L^?1 with acceptable precision and accuracy. There were almost no matrix effects. Recovery of brivudine spiked in drug-free plasma was higher than 77.17%. The method was used to study the pharmacokinetic profile of brivudine in human plasma after oral administration of brivudine tablets.     

Solvation effects in the electrochemistry of diphenylpicrylhydrazyl

The electrochemistry of diphenylpicrylhydrazyl (DPPH) was studied in nitromethane, nitrobenzene, benzonitrile, acetonitrile, acetone, methanol, ethanol, propanol-2,N,N-dimethylformamide,N,N-dimethylacetamide, and dimethylsulfoxide employing cyclic voltammetric technique. Reversible behaviour was observed for the systemsDPPH/DPPH ⁺ andDPPH/DPPH ^? in all solvents on the platinum microelectrode. The variation of ΔE ^form=(E _oxidation ^form ?E _reduction ^form ) upon solvent can be well described by a complementaryLewis acid—base model for solvent—solute interactions: ΔE ^form=?3.685DN?4.537An+651.84 with a correlation coefficient ofr=0.991 (E ^form stands for formal potential whereasDN andAN are the donor number and the acceptor number). The solvent effect on the position of the spectral absorption ofDPPH is also discussed;v _max values show good linear regression with the π*-parameter introduced byKamlet andTaft.     

LC–MS–MS Determination of Troxerutin in Plasma and Its Application to a Pharmacokinetic Study

A highly sensitive liquid chromatography–tandem mass spectrometry (LC–MS–MS) method for the determination of troxerutin in human plasma using tramadol as internal standard (IS) has been developed and validated. Sample preparation involved liquid–liquid extraction with ethyl acetate–isopropanol (95:5, v/v). The analyte and IS were separated by RP–LC with gradient elution using 10 mM ammonium acetate containing 0.1% formic acid and methanol at a flow rate of 0.9 mL min^?1. LC–MS–MS in the positive ion mode employed multiple reaction monitoring of the transitions at m/z 743.2→435.3 and m/z 264.1→58.0 for troxerutin and IS, respectively. The assay was linear in the concentration range 0.01–10 ng mL^?1 with precision and accuracy within assay variability limits as per FDA guidelines. The assay was successfully applied to a pharmacokinetic study involving oral administration of 300 mg troxerutin to eight healthy Chinese volunteers.     

Mass and charge assignment for electrospray ions by cation adduction

The assignment of the mass (m) value from the m/z value for ions with a multiple number of charges (z) in electrospray mass spectra usually utilizes multiple peaks of the same m but different z values, or unit-mass—separated isotopic peaks of the same z value from high resolution spectra. The latter approach is also feasible with much less resolving power using adduct ions of much higher mass separation. The application of this to mixture spectra containing many masses, such as spectra from tandem mass spectrometry (MS/MS) ion dissociation, does not appear to have been pointed out previously. Thus, replacing two protons by one Cu²⁺ ion increases the mass by 61.5 Da, with this shift providing a mass scale for assignment of m and z from this pair of m/z values. The more common Na⁺ adduct peaks provide a 22.0 Da separation, of utility for 1000 resolving power only below approximately 10 kDa. Further, collisional dissociation lowers the degree of Cu²⁺ adduction in the resulting sequence-specific fragment ions much less than that of the corresponding Na⁺ adducts, making the Cu²⁺ adducts far more useful for m and z determination in MS/MS studies.     

Increased phosphatidylcholine (16:0/16:0) in the folliculus lymphaticus of Warthin tumor

Warthin tumor (War-T), the second most common benign salivary gland tumor, consists mainly of neoplastic epithelium and lymphoid stroma. Some proteins and genes thought to be involved in War-T were evaluated by molecular biology and immunology. However, lipids as an important component of many tumor cells have not been well studied in War-T. To elucidate the molecular biology and pathogenesis of War-T, we investigated the visualized distribution of phosphatidylcholines (PCs) by imaging mass spectrometry (IMS). In our IMS analysis of a typical case, 10 signals were significantly different in intensity (p?+ (m/z 772.5), [PC (16:0/20:4)?+?K]⁺ (m/z 820.5), [PC (16:0/20:3)?+?K]⁺ (m/z 822.5), [PC (18:2/20:4)?+?K]⁺ (m/z 844.5), and [PC (18:0/20:5)?+?K]⁺ (m/z 846.5). PC (16:0/16:0) was increased specifically in the folliculus lymphaticus of War-T lymphoid stroma, suggesting a different metabolism. Localization of PC (16:0/16:0) might reflect inflammation activity participating in the pathogenesis of War-T. Thus, our IMS analysis revealed the profile of PCs specific to the War-T region. The molecules identified in our study provide important information for further studies of War-T pathogenesis.     

LC-MS-MS Determination and Pharmacokinetic Study of Clozapine in Human Plasma

A sensitive and selective liquid chromatographic method coupled with tandem mass spectrometry was established and validated for the determination and pharmacokinetic study of clozapine in human plasma. Ethyl acetate extraction was used for plasma sample preparation with mirtazapine as internal standard. Chromatographic separation was achieved on a Hanbon Kromasil C₁₈ (250 mm × 4.6 mm, 5 μm) column by isocratic elution with a mixture of 70 volumes of methanol and 30 volumes of water containing 0.2% ammonium acetate and 0.1% formic acid as mobile phase delivered at 1.0 mL min^?1. The MS-MS detection was carried out on a tandem mass spectrometer using positive electrospray ionization and multiple reaction monitoring with argon for collision-induced dissociation. The ion transitions were monitored as follows: m/z 327 to m/z 270 for clozapine and m/z 266 to m/z 195 for the internal standard (mirtazapine), respectively. Calibration curves were generated over the concentration range from 0.10 to 200 ng mL^?1 with the lower limit of quantification of 0.10 ng mL^?1, and two segments of linear calibration curves were established by regressing in the way of least-square in the range from 0.10 to 5.0 and 5.0 to 200 ng mL^?1, respectively. The intra- and inter-day precision and accuracy were determined at three different concentration levels, 0.20, 10.0 and 100 ng mL^?1, and were all better than 15% (n = 5). This specific and sensitive liquid chromatography coupled with tandem mass spectrometry has been successfully applied to a pharmacokinetic study of clozapine after a single oral dose of 25 mg in healthy Chinese volunteers.     

Effect of extraction method on phenolic content and antioxidant activity of mistletoe extracts from Viscum album subsp. abietis

The total content of polyphenols and flavonoids determined in the same plant and their corresponding antioxidant activities may vary widely, depending on the extraction conditions applied. This study was conducted to optimise the extraction conditions of phenolics and flavonoids from the mistletoe plant. Various extraction methods, i.e. ultrasound-assisted extraction technology, maceration, maceration with stirring, accelerated solvent extraction (ASE), and extraction under reflux were evaluated for their percentage extraction of polyphenols (TPC) and flavonoids (TFC) from Viscum album subsp. abietis. In addition, the anti-radical activity of extracts was analysed using the 2,2-diphenyl-1-picrylhydrazyl method. The effects of temperature, solvent type, and concentration on the phenolic extraction efficiency and antioxidant activity were studied using chemometric and statistical methods. The results showed that the extracts of V. album subsp. abietis contained large amounts of polyphenols and flavonoids (up to 57.673 mg g^?1 and 9.955 mg g^?1 of dry extract, respectively) and exhibited potent antioxidant activity, hence representing promising sources of powerful antioxidants. Due to its high extraction efficiency and considerable saving of time and solvent, ASE was more effective than the other extraction techniques. Extracts prepared with water-polar solvent mixtures displayed the highest TPC, TFC, and antioxidant activity, while organic polar solvents were the least efficient extractants.     

Characterisation and quantification of liposome-type nanoparticles in a beverage matrix using hydrodynamic chromatography and MALDI–TOF mass spectrometry

This paper describes the characterisation of liposome-type nanoparticles (NPs) dispersed in a beverage matrix. Characterisation is based on a two-step procedure: first, liposomes are separated on the basis of size in the nanometre range by use of hydrodynamic chromatography (HDC); second, chemical characterisation is performed by use of MALDI–TOF mass spectrometry (MS). Characterisation of three types of Coatsome liposome, a commercially available type of empty liposome, was investigated. All three liposome types, Coatsome A?=?anionic, N?=?neutral, and C?=?cationic, gave single peaks in HDC, reflecting diameters of 153, 187, and 205 nm, respectively. Subsequent MALDI–TOF MS in positive mode furnished major signals at m/z?=?734.5 ([M?+?H]⁺ adduct) and m/z?=?756.6 ([M?+?Na]⁺ adduct) of l-(α)-dipalmitoylphosphatidylcholine (DPPC) monomer and dimeric adducts at m/z?=?1468.1 and m/z?=?1490.1, respectively. MALDI–TOF MS in negative mode gave a signal at m/z?=?721.3 ([M???H]^? adduct) of l-(α)-dipalmitoylphosphatidylglycerol (DPPG), except for Coatsome C which lacks this phospholipid. After HDC separation of Coatsome A NPs the major DPPC and DPPG signals can be detected in the expected fractions by use of MALDI–TOF MS in positive and negative modes, respectively. Validation of the analytical strategy revealed linearity (R ²?>?0.99), repeatability (relative standard deviation <10 %), and reproducibility (relative standard deviation between days <10 %) were good, recovery was 61?±?5 %, and the limit of quantification was 1 mg?mL^?1 in this matrix. With 4 mg Coatsome A mL^?1 20 out of 20 samples furnished the 734.5 and 756.6 signals typical of DPPC in MALDI–TOF MS characterisation.     

Untersuchungen zur aufklärung des mechanismus des redoxsystems flavinmononucleotid/dihydroflavinmononucleotid: I. Coulometrische bestimmung der elektronenübergangszahl der reduktion von flavinmononucleotid

The reduction of flavinmononucleotide in 0.05 M H₂SO₄ was investigated. The charge number of the electrode reaction was determined coulometrically; it goes through a minimum of z=1.6±0.1, when the degree of reduction, x, is about 1/2; for small and for large degrees of reduction z is equal to 2. The sum of the anodic and cathodic diffusion currents decreases until the degree of reduction, x?0.6. This observation and the minimum found for the dependence of z on x, may be explained by the formation of the complex (FMNH⁺·FMNH₂). It is possible to oxidize this complex within the potential range investigated by us but not to reduce it. The existence and non-reducibility of this complex was confirmed experimentally. Spectroscopic investigations also showed that the complex (FMNH^*·FMNH₂) is formed, for the extinctions at 570 and 900 nm do not obey the relation (E₅₇₀)² ≈ E₉₀₀.     

LC Determination of Trace Biogenic Amines in Foods Samples with Fluorescence Detection and MS Identification

A pre-column derivatization method for the simple, sensitive determination of biogenic amines using 10-ethyl-acridine-3-sulfonyl chloride (EASC) as labeling reagent with fluorescence detection and mass spectrometry (MS) identification has been developed. After pre-column derivatization, the labeled biogenic amines were separated on a Hypersil BDS-C18 column by gradient elution. The derivatives showed an intense protonated molecular ion corresponding m/z [M + H]⁺ in positive-ion mode. The collision-induced dissociation of protonated molecular ion formed specific fragment ions at m/z 196.5, m/z 222.7, m/z 224.4 and m/z 272.5, m/z 286.2. Satisfactory linear responses were observed at the concentration range of 0.02?C10 ??mol L^?1 with coefficients of >0.9993. Detection limits obtained by the analysis of a derivatized standard containing 0.2 pmol of each biogenic amine, were from 20.22 to 109.2 fmol (at a signal-to-noise ratio of 3). The relative standard deviations of retention times and peak areas for each biogenic amine were <0.96 and 3.22%, respectively. Recoveries except for PUT were in the range of 96.7?C103.6% for chicken sausage and 95.8?C104.6% for pork sausage The established method for the determination of biogenic amines except for PUT from real samples was satisfactory.     

An automated method for measurement of methoxetamine in human plasma by use of turbulent flow on-line extraction coupled with liquid chromatography and mass spectrometric detection

Methoxetamine is a new ketamine derivative designer drug which has recently become available via the Internet marketed as “legal ketamine”. It is a new dissociative recreational drug, acting as an NMDA receptor antagonist and dopamine reuptake inhibitor. The objective of this study was to develop on-line automated sample preparation using a TurboFlow device coupled with liquid chromatography with ion-trap mass spectrometric detection for measurement of methoxetamine in human plasma. Samples (100 μL) were vortex mixed with internal standard solution (ketamine-d4 in acetonitrile). After centrifugation, 20 μL of the supernatant was injected on to a 50 mm?×?0.5-mm C18XL Turboflow column. The retained analytes were then back-flushed on to a 50 mm?×?3-mm (3 μm) Hypersil Gold analytical column for chromatographic separation, then eluted with a formate buffer–acetonitrile gradient. Methoxetamine and the IS were ionized by electrospray in positive mode. Parent [M + H]⁺ ions were m/z 248.1 for methoxetamine and m/z 242.0 for the IS. The most intense product ions from methoxetamine (m/z 203.0) and the IS (m/z 224.0) were used for quantification. The assay was accurate (96.8–108.8 % range) and precise (intra and inter-day coefficients of variation <8.8 %) over the range of 2.0 (lower limit of quantification) to 1000.0 ng mL^?1 (upper limit of quantification). No matrix effect was observed. This method has been successfully applied to determination of plasma concentrations of methoxetamine in the first French hospitalization case report after acute intoxication; the plasma concentration was 136 ng mL^?1.     

Metabolite Characterization and Correlations with Antioxidant and Wound Healing Properties of Oil Palm (Elaeis guineensis Jacq.) Leaflets via 1H-NMR-Based Metabolomics Approach

Oil palm (Elaeis guineensis Jacq.) leaflets (OPLs) are one of the major agricultural by-products generated from the massive cultivation of Malaysian palm oil. This biomass is also reported to be of potential value based on its health-improving effects. By employing proton nuclear magnetic resonance (¹H-NMR) spectroscopy combined with multivariate data analysis (MVDA), the metabolite profile of OPLs was characterized and correlated with their antioxidant and wound healing properties. Principal component analysis (PCA) classified four varieties of extracts, prepared using solvents ranging from polar to medium polarity, into three distinct clusters. Cumulatively, six flavonoids, eight organic acids, four carbohydrates, and an amine were identified from the solvent extracts. The more polar extracts, such as, the ethyl acetate-methanol, absolute methanol, and methanol-water, were richer in phytochemicals. Based on partial least square (PLS) analysis, the constituents in these extracts, such as (+)-catechin, (−)-epicatechin, orientin, isoorientin, vitexin, and isovitexin, were strongly correlated with the measured antioxidant activities, comprising ferric reducing antioxidant power (FRAP), 2,2-diphenyl-1-picrylhydrazyl (DPPH), and nitric oxide (NO) free radical scavenging activities, as well as with cell proliferation and migration activities. This study has provided crucial evidence on the importance of these natural antioxidant compounds on the wound healing properties of OPL.     

LC-DAD-ESI-MS Characterization of Carbohydrates Using a New Labeling Reagent

A novel labeling reagent 1-(2-naphthyl)-3-methyl-5-pyrazolone (NMP) coupling to liquid chromatography with electrospray ionization mass spectrometry for the detection of carbohydrates from the derivatized rape bee pollen samples is reported. Carbohydrates are derivatized to their bis-NMP-labeled derivatives. Derivatives showed an intense protonated molecular ion at m/z [M+H]⁺ in positive-ion detection mode. The mass-to-charge ratios of characteristic fragment ions at m/z 473.0 could be used for the accurately qualitative analysis of carbohydrates. This characteristic fragment ion is from the cleavage of C2–C3 bond in carbohydrate chain giving the specific fragment ions at m/z [MH-C _m H_2m+1O _m -H₂O]⁺ for pentose, hexose and glyceraldehydes and at m/z [MH-C _m H_2m-1O _m+1-H₂O]⁺ for alduronic acids such as galacturonic acid and glucuronic acid (m = n ? 2, n is carbon number of carbohydrate). No interferences for all aliphatic and aromatic aldehydes presented in natural environmental samples were observed due to the highly specific parent mass-to-charge ratio and the characteristic fragment ions. The method, in conjunction with a gradient elution, offered a baseline resolution of carbohydrate derivatives on a reversed-phase Hypersil ODS-2 column. The carbohydrates such as mannose, galacturonic acid, glucuronic acid, rhamnose, glucose, galactose, xylose, arabinose and fucose can successfully be detected.     

Simultaneous Determination of Pethidine and Atropine in Rabbit Plasma by LC�CMS�CMS and Its Application to a Pharmacokinetic Study after Intramuscular Administration

A sensitive and selective liquid chromatography?Ctandem mass spectrometry method for the determination of pethidine and atropine in rabbit plasma was developed and validated. The analytes and internal standard (IS) are extracted from plasma by liquid?Cliquid extraction using ethyl acetate, and separated on a Zorbax SB-Aq column (2.1 × 150 mm, 3.5 ??m) using acetonitrile?C0.1% formic acid as mobile phase with gradient elution. Electrospray ionization source was applied and operated in positive ion mode, and multiple reaction monitoring mode was used for quantification using target fragment ions m/z 247.8 ?? 219.7 for pethidine, m/z 289.9 ?? 123.8 for atropine and m/z 295.0 ?? 266.8 for IS, respectively. The assay is linear over the range of 5?C1,000 ng mL^?1 for pethidine and atropine, with a lower limit of quantification of 3 ng mL^?1 for pethidine and 5 ng mL^?1 for atropine. Intra-day and inter-day precision are less than 11% and the accuracy are in the range of 90.4?C106.3%. Furthermore, the newly developed method is successfully used for the determination of pethidine and atropine in rabbit plasma for pharmacokinetic study.     

Study of the Gas-Phase Intramolecular Aryltrifluoromethylation of Phenyl(Trifluoromethyl)Iodonium by ESI-MS/MS

The gas-phase reactions of the reactive λ ³-phenyl(trifluoromethyl)iodonium (PhI⁺(III)CF₃, 1 at m/z 273) to the radical cation of iodobenzene (PhI^?+, 2 at m/z 204) via the loss of ·CF₃ and the radical cation of trifluoromethylbenzene (PhCF₃ ^?+, 3 at m/z 146) via the loss of ·I, were studied by electrospray ionization tandem mass spectrometry (ESI-MS/MS). Interestingly, the gas-phase intramolecular coupling reaction of CF₃ with phenyl via the CF₃ migration process of 1 at m/z 273 from iodine to the phenyl to give 3 at m/z 146 could only occur according to an intramolecular aromatic substitution mechanism. Density functional theory (DFT) calculations showed that the gas-phase intramolecular aryltrifluoromethylation of 1 at m/z 273 to 3 at m/z 146 occurred via a Meisenheimer complex intermediate (MC), where the triplevalent I center of 1 was reduced to monovalent I. Most importantly, the structure of 3 at m/z 146 derived from 1 at m/z 273 in ESI-MS/MS process was confirmed by comparison of its MS/MS with that of an authentic PhCF₃ ^?+ at m/z 146 acquired from the electron ionization (EI)-MS/MS analysis of PhCF₃. Thus, our studies revealed the intrinsic reactivity tendencies of λ³-phenyl(trifluoromethyl)iodonium under solvent-free conditions.      

Determination of diquat and paraquat in water by liquid chromatography-(electrospray ionization) mass spectrometry

A method for the determination of the herbicides diquat and paraquat in water was developed using liquid chromatography-(electrospray ionization) mass spectrometry [LC-(ESI)MS]. The analytes were isolated on an ENVI-8 DSK solid phase extraction (SPE) disk and eluted with 5-M trifluoroacetic acid (TFA). The eluate was evaporated to dryness and the analytes were redissolved in the mobile phase (7% methanol/93% water/25-mM TFA). The extract was analyzed by liquid chromatography (C1 column) with postcolumn addition of propionic acid/methanol followed by (ESI)MS. Diquat was detected using the [M²⁺ ? H⁺] ion (M²⁺ = dication) at m/z 183, whereas paraquat was detected using the mono-trifluoroacetate ion pair [M²⁺/^?OOCCF₃] at m/z 299. Quantitation was done by isotope dilution mass spectrometry using d ₄-diquat and d ₈-paraquat and the corresponding ions [M²⁺ ? D⁺] and [M²⁺/^?OOCCF₃] at m/z 186 and m/z 307, respectively. Detection limits of 0. 1 and 0. 2 µg/L, respectively (based on the dications), were adequate to meet the Ontario Drinking Water Objectives of 70 and 10 µg/L, respectively, and the Ontario Provincial Water Quality Objective for diquat of 0. 5 µg/L. Precision and accuracy were 14% and 6% for diquat and 12% and 3% for paraquat.     

Antioxidant activity and phenolic compounds of buckwheat and barley by the data of spectrophotometry and HPLC

The antioxidant activity of buckwheat and barley extracts by reaction with 1,1-diphenyl-2-picrylhydrazyl and the total of phenolic compounds have been determined using the Folin-Ciocalteu reagent. It has been found that water-ethanol extracts of buckwheat are characterized by higher antioxidant activity (6.2 ± 0.5 μM-eq. of Trolox/g) and concentration of phenolic compounds (4.41 ± 0.07 mg-eq. of rutin/g) compared to barley extracts (4.2 ± 0.3 μM-eq. of Trolox/g and 2.4 ± 0.1 mg-eq. of rutin/g, respectively). A series of phenolic compounds have been identified by HPLC with UV detection and mass spectrometric detection with electrospray ionization. The main phenolic compounds-antioxidants in buckwheat extracts are rutin, catechin and epicatechin, 1-O-caffeoyl-O-rutinoside (m/z 487), and epicatechin-O-3,4-dimethylgallate (m/z 469), and in the barley extract, catechin, prodelphinidin B3 (m/z 593), procyanidin B3 (m/z 577), and procyanidin C2 (m/z 865).