Hollow fibre-based liquid phase microextraction combined with high-performance liquid chromatography for the analysis of flavonoids in Echinophora platyloba DC. and Mentha piperita

A simple, inexpensive and efficient three phase hollow fibre liquid phase microextraction (HF-LPME) technique combined with HPLC was used for the simultaneous determination of flavonoids in Echinophora platyloba DC. and Mentha piperita. Different factors affecting the HF-LPME procedure were investigated and optimised. The optimised extraction conditions were as follows: 1-octanol as an organic solvent, pH_donor = 2, pH_acceptor = 9.75, stirring rate of 1000 rpm, extraction time of 80 min, without addition of salt. Under these conditions, the enrichment factors ranged between 146 and 311. The values of intra and inter-day relative standard deviations (RSD) were in the range of 3.18–6.00% and 7.25–11.00%, respectively. The limits of detection (LODs) ranged between 0.5 and 7.0 ng mL⁻¹. Among the investigated flavonoids quercetin was found in E. platyloba DC. and luteolin was found in M. piperita. Concentration of quercetin and luteolin was 0.015 and 0.025 mg g⁻¹ respectively.     

The effect of sulphuric acid activation on the crystallinity,surface area,porosity, surface acidity,and bleaching power of a bentonite

The Hanç?l? (Keskin, Ankara, Turkey) bentonite was activated with H₂SO₄ by dry method at 97 °C for 6 h to obtain optimum parameters for imparting a maximum bleaching power towards soybean oil. The H₂SO₄ content in dry bentonite-acid mixture was changed between 0% and 70%. The natural and activated samples were examined by X-ray diffraction (XRD), N₂ adsorption–desorption, and n-butylamine adsorption (from the solution in cyclohexane). The specific surface area (S), specific micro–mesopore volume (V), mesopore size distribution (PSD), and surface acidity (n_m) of the samples were determined. The bleaching power (BP) of each sample for alkali-refined soybean oil was determined. The S, V, n_m, and BP increase after activation at various acid contents up to 40% H₂SO₄ without any considerable change in crystal structure of the smectite. The BP is controlled more by the PSD rather than other adsorptive properties of the bleaching earth. The optimum parameters for activation to obtain maximum bleaching power, are H₂SO₄% = 50–60, S = 250–230 m² g⁻¹, V = 0.46–0.47 cm³ g⁻¹, n_m = 9.0 × 10⁻⁴–8.4 × 10⁻⁴ mol g⁻¹ and PSD mainly distributed between 1.4 and 6.0 nm.     

Molecularly imprinted solid phase extraction coupled to high-performance liquid chromatography for determination of trace dichlorvos residues in vegetables

In this paper, we prepared a highly selective imprinted polymer by a room temperature ionic liquid-mediated bulk polymerization technique, using dichlorvos as the template, methacrylic acid as the functional monomers, and trimethylolpropane trimethacrylate as the cross-linker. This functionalized material was characterized by FT-IR, static and kinetic adsorption experiments, and the results showed that this imprinted sorbent exhibited good recognition and selective ability, and offered fast kinetics for the adsorption and desorption of dichlorvos. Using the prepared material as a solid phase extraction sorbent, a novel sample pre-treatment technique that can be coupled to high-performance liquid chromatography (HPLC) had been developed for determination of trace dichlorvos residues in foods. Under the selected experimental condition, the detection limit (S/N = 3) of dichlorvos was 94.8 ng L⁻¹, and the peak area precision (RSD) for five replicate detections of 10 μg L⁻¹ dichlorvos was 4.41%. The blank samples of cucumber and lettuce spiked with dichlorvos at 0.005 and 0.02 μg g⁻¹ levels were determined with recoveries ranging from 82.1% to 94.0%.     

Voltammetric behaviour and square-wave voltammetric determination of the potent antioxidant and anticarcinogenic agent ellagic acid in foodstuffs

The voltammetric behaviour of ellagic acid (EA) is investigated by cyclic, differential pulse and square-wave voltammetry (CV, DPV and SWV, respectively). Based on the anodic oxidation peak at approximately 0.42 V in acetic/acetate buffer (pH 5.5) a robust and a highly reliable square-wave voltammetric method is presented for the determination of EA. The oxidation peak current was linearly dependent on the concentration of EA in the range of 1.0 × 10⁻⁷–1.5 × 10⁻⁶ mol/L (r = 0.9997), with a detection limit of 1.0 × 10⁻⁸ mol/L (S/N = 3) and a quantification limit of 3.4 × 10⁻⁸ mol/L (S/N = 10), good reproducibility and a satisfactory level of selectivity towards others polyphenols. The proposed method was applied to the determination of free and total EA in fruits, nuts and juices with good analytical results being obtained.     

Dispersive liquid–liquid microextraction combined with sweeping micellar electrokinetic chromatography for the determination of some neonicotinoid insecticides in cucumber samples

A rapid, simple and sensitive method has been developed for the analysis of some neonicotinoid insecticides in cucumber samples by using dispersive liquid–liquid microextraction (DLLME) coupled with sweeping in micellar electrokinetic chromatography (MEKC). Under optimised conditions, the enrichment factors were achieved in the range from 4000 to 10,000. The linearity of the method was in the range from 2.7 to 200 ng g⁻¹ for thiacloprid, acetamiprid and imidacloprid, and in the range from 4.0 to 200 ng g⁻¹ for imidaclothiz in cucumber samples, with the determination coefficients (r²) ranging from 0.9924 to 0.9968. The limits of detection (LODs, S/N = 3) ranged from 0.8 to 1.2 ng g⁻¹. The relative standard deviations (RSDs) at the concentration levels of 10.0 and 50.0 ng g⁻¹ each of the neonicotinoid insecticides in cucumber samples varied from 3.8% to 6.3%. The developed method has been successfully applied to the analysis of the neonicotinoid insecticides in cucumbers with a satisfactory result.     

Monitoring of fatty acid composition in virgin olive oil by Fourier transformed infrared spectroscopy coupled with partial least squares

A rapid Fourier transformed infrared (FTIR) attenuated total reflectance (ATR) spectroscopic method was applied to the determination of fatty acid (FA) profile and peroxide value (PV) of virgin olive oil. Calibration models were constructed using partial least squares (PLS) regression. A FA calibration model was constructed in the spectral range from 3033 to 700 cm⁻¹. Oleic acid (62.0–80.0%), linoleic acid (5.3–15.0%), saturated fatty acids (SFA, 12.6–19.7%), mono-unsaturated fatty acids (MUFA, 64.4–81.0%) and poly-unsaturated fatty acids (PUFA, 6.0–15.9%) were considered for chemometric analysis. PV (5.7–15.7 meq O₂ kg⁻¹) was calibrated using the signal of the full spectral range 4000–700 cm⁻¹ with first derivative pre-treatment. The LODs of the FTIR-chemometric methods were: 3.0% for oleic acid, 0.5% for linoleic acid, 1.3% for SFA, 3.0% for MUFA, 0.3% for PUFA and 1.0 meq O₂ kg⁻¹ for PV. Analytical methods were evaluated by use of validation samples (n = 25 for all the FA related parameters and n = 10 for PV) with nearly quantitative recovery rates (98–103%). The proposed method provided results comparable to official procedures, with the advantages of being less expensive and more rapid.     

Electrooxidation of flavonoids at platinum electrode studied by cyclic voltammetry

Flavonoids are natural vegetable dyes synthesized from phenylalanine. They are responsible for colour of blooming plant portions. Moreover, they are very important for human health due to their activity as free radical acceptors. Cyclic and differential pulse voltammetry was used in the determination of kinetic parameters of flavonoids electrooxidation. Electrochemical measurements of the oxidation of organic compounds can be helpful in understanding how these compounds are metabolised by living organisms. Flavonoids electrochemical oxidation is an irreversible reaction at a platinum electrode. In the case of morin hydrate, rutin, dihydroxyflavone, trihydroxyflavone, hesperidin, quercetin, the first step of the electrooxidation includes an exchange of two electrons during the oxidation of hydroxyl groups in the ring B. Hydroxyl groups in the rings A and C are probably oxidised in subsequent steps. The heterogeneous rate constants (k_bh) determined for the flavonoids electrooxidation are as follows: morin – 3.59 × 10⁻⁴, rutin – 4.42 × 10⁻⁴, dihydroxyflavone – 4.54 × 10⁻⁴, trihydroxyflavone – 4.19 × 10⁻⁴, hesperidin – 4.50 × 10⁻⁴ and quercetin – 4.63 × 10⁻⁴ cm s⁻¹. Their anodic transition coefficient ranged from 0.63 to 0.48 (n = 2). Xanthone and flavone were oxidised easiest and quickest among other substrates at the platinum electrode with the heterogeneous rate constants (k_bh) of 7.08 × 10⁻⁴ and 6.46 × 10⁻⁴ cm s⁻¹, respectively.     

Determination of molybdenum by adsorptive anodic stripping voltammetry of molybdenum–alizarin violet complex at an acetylene black paste electrode

A reliable and sensitive procedure for the determination of trace levels of molybdenum by adsorptive anodic stripping voltammetry is proposed. The method is based on adsorptive accumulation of the molybdenum (Mo)–alizarin violet (AV) complex onto an acetylene black paste electrode (ABPE), followed by oxidation of the adsorbed species by voltammetric scan using a second-order derivative modulation. For voltammetric determination of molybdenum, the parameters influencing the peak current have been optimized. Under the selected conditions, the electrode demonstrated linear response over a wide range of Mo(VI) concentration (6.0 × 10⁻⁹–1.0 × 10⁻⁵ mol/L), the detection limit was 2.0 × 10⁻⁹ mol/L (S/N = 3) for 120 s accumulation. The effects of potential interfering ions were studied, and it was found that the proposed procedure was free from most interferences. The method has been applied to the determination of molybdenum in plant foodstuffs, and satisfied results were obtained.     

Mate (Ilex paraguariensis St. Hilaire) saponins induce caspase-3-dependent apoptosis in human colon cancer cells in vitro

Saponins are naturally occurring metabolites associated with several health benefits. The objective was to quantify and purify saponins from mate dry leaves, and to assess their anti inflammatory and apoptotic mechanisms in human colon cancer cells in vitro. Matesaponins were extracted with methanol from dry leaves, partially purified and quantified. Leaves contained 10–15 mg/g dry weight total saponins, predominantly matesaponins 1 and 2. HPLC and LC/ESI-MS-MS identified saponins in six preparative chromatographic fractions (A, B, C, D, E, and F). Major matesaponins were identified as 1 [M–H]⁻ = 911 and 2 [M–H]⁻ = 1057, with trace amounts of 3 [M–H]⁻ = 1073, 4 [M–H]⁻ = 1219, and 5 [M–H]⁻ = 1383. Fractions D, E, and F significantly inhibited iNOS (IC₃₅ = 36.3, 29.5, 43.7 μM), PGE₂ (IC₃₅ = 23.1, 22.3, 11.7 μM) and COX-2 (IC₃₅ = 45.7, 32.4, 17.0 μM). Fraction F reduced nuclear translocation of nuclear factor-κB subunits p50 (49.8%) and p65 (49.0%) and induced apoptosis through suppression of Bcl-2 and increased Bax protein expressions and activated caspase-3 activity. Saponins in leaves of mate prevent inflammation and colon cancer in vitro.     

Enantioselective degradation of diclofop-methyl in cole (Brassica chinensis L.)

The stereoselective degradation of the racemic diclofop-methyl and its chiral degradation product, diclofop (the hydrolysate of diclofop-methyl), in cole has been investigated. Both enantiomers of diclofop-methyl and diclofop were extracted by organic solvent and detected by chiral high-performance liquid chromatography–diode array detector (DAD). Cellulose-tris-(3,5-dimethylphenylcarbamate)-based chiral column was used for the chiral separation of the four enantiomers applying a mixture of n-hexane and 2-propanol (98:2) concluding 0.1% TFA as mobile phase at a flow rate of 1.0 mL/min. The assay method was linear over a range of concentrations (0.5–250 mg L⁻¹), and the mean recovery was more than 60% for all the enantiomers. The limit of detection for all the enantiomers was 0.2 μg g⁻¹ in plant. Racemic diclofop-methyl was foliar sprayed to cole. Stereoselective behaviour was observed in the diclofop-methyl degradation process. The (S)-diclofop-methyl dissipated faster than (R)-diclofop-methyl. In the case of diclofop, the generation and degradation rates of (S)-enantiomer were higher than (R)-enantiomer in the plant.     

Simultaneous determination of nine ginsenosides in functional foods by high performance liquid chromatography with diode array detector detection

A method for simultaneous determination of nine ginsenosides including two pairs of isomers and F-group ginsenosides in functional foods by high performance liquid chromatography with diode array detector detection is presented in this paper. After samples were ultrasonically extracted with 60% methanol aqueous solution and centrifuged, the ginsenosides Rg1, Re, Rf, Rb1, Rb3, Rg3, 20(S)-F1, 20(S)-F2, and 20(S)-Rh2 in sample solution were separated by an ODS column with a programmed gradient elution with a mobile phase consisting of water and acetonitrile. Qualitative determination was based on the retention time and the characteristic absorption spectra of ginsenosides and standard curves were used for quantification. Recoveries were from 91.5% to 104.5%. The limits of detection were from 7.0 ng to 16.5 ng. The relative standard deviations were <5% (intra-day) and 1.77–7.04% (inter-day). Ginsenosides in six kinds of functional foods were determined by this method with satisfactory results.     

Multiresidue determination of tetracycline antibiotics in propolis by using HPLC-UV detection with ultrasonic-assisted extraction and two-step solid phase extraction

An analytical method in propolis was developed and validated for the determination of four tetracyclines (TCs) by high performance liquid chromatography (HPLC) for the first time. After extraction by ultrasound, the extracting solution was subjected to Oasis HLB and weak cation-exchange cartridge to remove water-soluble and fat-soluble flavonoids, aromatic acids, terpenoid compounds, wax, and pollen debris. The calibration curves of fortified samples showed acceptable linear response (R² > 0.99) through a range of 100–5000 ng g⁻¹ in 20 replicates of six concentrations and the analysis of variance (ANOVA) was performed to validate the regression data. The limit of quantification of four TCs were 100 and 150 ng g⁻¹, respectively. The recoveries of the four TCs for propolis samples spiked with 100–500 ng g⁻¹ were in the range of 61.9–88.5% and the RSDs were between 4.80% and 13.2%. Traces of tetracycline were found in two out of 30 analysed real samples.     

Interaction of milk α- and β-caseins with tea polyphenols

The interaction of α- and β-caseins with tea polyphenols (+)-catechin (C), (−)-epicatechin (EC), (−)-epigallocatechin (EGC) and (−)-epigallocatechin gallate (EGCG) was examined at a molecular level, using FTIR, UV–visible, CD and fluorescence spectroscopic methods as well as molecular modelling. The polyphenol binding mode, the binding constant and the effects of polyphenol complexation on casein stability and conformation were determined. Structural analysis showed that polyphenols bind casein via both hydrophilic and hydrophobic interactions with overall binding constants of K_C–α-cas = 1.8 (±0.8) × 10³ M⁻¹, K_EC–α-cas = 1.8 (±0.6) × 10³ M⁻¹, K_EGC–α-cas = 2.4 (±1.1) × 10³ M⁻¹ and K_{EGCG–α-cas} = 7.4 (±0.4) × 10³ M⁻¹, K_C–β-cas = 2.9 (±0.3) × 10³ M⁻¹, K_EC–β-cas = 2.5 (±0.6) × 10³ M⁻¹, K_EGC–β-cas = 3.5 (±0.7) × 10³ M⁻¹ and K_{EGCG–β-cas} = 1.59 (±0.2) × 10⁴ M⁻¹. The number of polyphenol bound per protein molecule (n) was 1.1 (C), 0.9 (EC), 1.1 (EGC), 1.5 (EGCG) for α-casien and 1.0 (C), 1.0 (EC), 1.1 (EGC) and 1.5 (EGCG) for β-casein. Structural modelling showed the participation of several amino acid residues in polyphenol–protein complexation with extended H-bonding network. Casein conformation was altered by polyphenol with a major reduction of α-helix and β-sheet and increase of random coil and turn structure suggesting further protein unfolding. These data can be used to explain the mechanism by which the antioxidant activity of tea compounds is affected by the addition of milk.     

The reduction of Cu(II)/neocuproine complexes by some polyphenols: Total polyphenols determination in wine samples

A new method is presented for spectrophotometric determination of total polyphenols content in wine. The procedure is a modified CUPRAC method based on the reduction of Cu(II), in hydroethanolic medium (pH 7.0) in the presence of neocuproine (2,9-dimethyl-1,10-phenanthroline), by polyphenols, yielding a Cu(I) complexes with maximum absorption peak at 450 nm. The absorbance values are linear (r = 0.998, n = 6) with tannic acid concentrations from 0.4 to 3.6 μmol L⁻¹. The limit of detection obtained was 0.41 μmol L⁻¹ and relative standard deviation 1.2% (1 μmol L⁻¹; n = 8). Recoveries between 80% and 110% (mean value of 95%) were calculated for total polyphenols determination in 14 commercials and 2 synthetic wine samples (with and without sulphite). The proposed procedure is about 1.5 more sensitive than the official Folin–Ciocalteu method. The sensitivities of both methods were compared by the analytical responses of several polyphenols tested in each method.     

Analysis of multi-pesticide residues in the foods of animal origin by GC–MS coupled with accelerated solvent extraction and gel permeation chromatography cleanup

A new analytical method was developed to simultaneously determine residues of 109 pesticides (including isomers) in the foods of animal origin. Acetonitrile was selected for accelerated solvent extraction (ASE) for effectively extracting the pesticides from the fatty samples. The cleanup was performed with an automated gel permeation chromatography (GPC) cleanup system. The prepared samples were analysed with GC–MS in the selected ion monitoring mode (SIM) using one target and two qualitative ions for each analyte. Chlorpyrifos-d₁₀ was used as an internal standard. The lowest limit of detection was 0.3 μg kg⁻¹ for some pesticides. The recoveries and relative standard deviations (RSDs) were checked by spiking untreated samples with pesticides at 0.05, 0.1 and 0.2 mg kg⁻¹. The average recoveries of most pesticides were from 62.6% to 107.8%. The precision values expressed as RSD were all ?20.5% (n = 6). Good linearity (r ? 0.99) was observed between 0.05 and 1.5 μg mL⁻¹.     

Liquid chromatography–tandem mass spectrometry for the determination of chrysoidine in yellow-fin tuna

A high performance liquid chromatography (HPLC) coupled to electrospray ionisation tandem mass spectrometry (MS/MS) method was described for the residue detection of chrysoidine in yellow-fin tuna in the present study. Samples were cleaned up with solid phase extraction (SPE) cartridge, and then injected into HPLC for separation. Multiple-reaction monitoring (MRM) was applied for quantitative determination. Results showed that the low limit of detection (LOD) of the method was 1.25 × 10⁻¹² g, and the low limit of quantification (LOQ) was 0.42 μg/L. The standard calibration curve was y = 2333.9x −845 (r² > 0.99) with the linear range of 0.63–100 μg/L. The average recoveries of chrysoidine ranged from 86.0% to 108.0% when the spiked concentration was from 0.5 μg/kg to 20 μg/kg. And the developed method also showed the good test precisions (RSD%: 4.38–14.27%).     

Multiresidue method for determination of 88 pesticides in berry fruits using solid-phase extraction and gas chromatography–mass spectrometry: Determination of 88 pesticides in berries using SPE and GC–MS

A method using solid phase extraction (SPE) cleanup followed by gas chromatography–mass spectrometry (GC–MS) has been established for quantitative determination of 88 pesticide residues in berry fruits including raspberry, strawberry, blueberry and grape. Based on an appraisal of the characteristics of GC–MS, validation experiments were conducted for 88 pesticides. In the method, solid-phase extraction was carried out using Envi-Carb cartridge coupled with NH₂-LC cartridge with acetonitrile–toluene (3:1, v/v) as the eluted solvent. In the linear range of each pesticide, the correlation coefficient was R² ? 0.99. At the low, medium and high three fortification levels of 0.05–0.5 mg kg⁻¹, recoveries fell within 63–137%. The relative standard deviation was between 1% and 19% for all 88 pesticides. Low limits of detection (0.006–0.05 mg kg⁻¹) and quantification (0.02–0.15 mg kg⁻¹) were readily achieved with this method for all tested pesticides.     

Determination of cyclamate in artificial sweeteners and beverages using headspace single-drop microextraction and gas chromatography flame-ionisation detection

A new method for determination of cyclamate was developed using headspace single-drop microextraction (HS-SDME) and gas chromatography (GC). The method is based on the reaction of cyclamate and nitrite in the acidic media and microextraction of cyclohexene formed for subsequent determination with GC. Conditions for both derivatisation and HS-SDME have been optimised. The calibration curve for cyclamate determination showed good linearity in the range of 30–1000 μmol L⁻¹ (R² = 0.9992) and the limit of detection (S/N = 3) was estimated to be 5 μmol L⁻¹. The repeatability and reproducibility for a 200 μmol L⁻¹ of cyclamate were 4% and 4.8% (N = 5), respectively. The purposed method was successfully applied for determination of cyclamate in beverages and sweetener tablets. The average recovery of spiked samples was 97%. The results demonstrated that the developed method is simple, rapid, inexpensive, accurate and remarkably free from interference effects.     

Flow injection analysis of total curcuminoids in turmeric and total antioxidant capacity using 2,2′-diphenyl-1-picrylhydrazyl assay

A simple flow injection analysis procedure is proposed for the determination of curcuminoids content in turmeric extracts. The method is based on the formation of a coloured complex between 4-aminoantipyrine and curcuminoids, in the presence of an oxidising reagent such as potassium hexacyanoferrate (III) in alkaline media. Conditions selected as a result of these trials were implemented in a flow injection analytical system in which the influence of injection volume, flow rate, reagent concentration and mixing coil length, was evaluated. Under the optimum conditions the total amount of curcuminoids could be determined within a concentration range of 5–50 μg mL⁻¹ which can be expressed by the regression equation y = 0.003x − 0.0053 (r² = 0.9997). The limits of detection and quantitation were found to be 0.6 μg mL⁻¹ and 1.8 μg mL⁻¹, respectively. The reproducibility of analytical readings was indicative of standard deviations <2%. The sample was extracted and analysed by using the proposed method. The percentage recoveries were found to be 94.3–108.0. The proposed system was applied to the determination of curcuminoids content in turmeric. The total curcuminoid contents in turmeric extract were found to be 0.9–4.3% (w/w). The development method is simple, economic, rapid and especially suitable for quality control in pharmaceutical plants.     

Voluntary food fortification with folic acid in Spain: Predicted contribution to children’s dietary intakes as assessed with new food folate composition data

The Spanish market offers a significant number of folic acid (FA) voluntarily fortified foods. We analysed FA and (6S)-5-methyltetrahydrofolic acid ((6S)-5-CH₃-H₄PteGlu) content in ready-to-eat cereals (RTEC) (n = 68) and cow’s milk (n = 25) by a previously validated affinity chromatography–HPLC method. Contribution to potential FA intakes for children aged 2–13 years, was assessed using food consumption data from a representative nationwide study, folate Recommended Dietary Intakes (RDI), and Upper Levels (UL). Results showed that at all food fortification levels obtained, fortified products provided more than tenfold FA than (6S)-5-CH₃-H₄PteGlu. For RTEC, the high fortification level provided 6–21%, per serving, of RDI and ?32% of ULs at 90th percentile of RTEC consumption (P90). Milk products fortified at the higher level reached on average 54–136% of RDI per serving and only exceeded UL at P90 of milk consumption in children aged 2–5 years.