SFC-UV determination of diflubenzuron residues,teflubenzuron and triflumuron in apple and pear pulps for baby food

Summary A method to determine residues of diflubenzuron (DFB), teflubenzuron (TFB), triflumuron (TFM) at 0.01 ppm with recoveries above 60% in apple and pear pulps for baby food is described. DFB, TFB and TFM are extracted with methanol, and cleaned up by SPE using C18 stationary phase and methanol mobile phase. Analysis of the three pesticides is by SFC-UV at 254 nm using a Diol column, and CO₂ at 30 MPa and 40°C modified with acetonitrile (10%) mobile phase.     

Determination of some selected polycyclic aromatic hydrocarbons in environmental samples by high-performance liquid chromatography with fluorescence detection

Summary Analytical methods for the determination in environmental samples, of some selected Polycyclic Aromatic Hydrocarbons (PAH's), which are included on the EPA Priority Pollutant list, have been developed and evaluated. The methodology involves the extraction of PAH's from water samples by solvent extraction with dichloromethane. Solid samples were ultrasonically extracted with acetone/hexane and the extract was cleaned up on a silica gel/alumina column. The concentrated and cleaned up extracts were analysed by HPLC on a polymeric C₁₈ column using a gradient of acetonitrile/water as the mobile phase and fluorescence detection. Typical detection limits lie in the range of 1–30 ng ml^–1 of the analytes, but after sample pretreatment detection limits of 10–300 ng l^–1 were obtained. The extraction, clean-up and HPLC methodology was applied to the determination of selected PAH's in coal washings samples and the method was validated by the quantification of PAH's in a natural contaminated and a spiked sediment.     

果蔬中8种苯甲酰脲类农药残留量的液相色谱-串联质谱法测定

建立了果汁蔬菜中8种苯甲酰脲类(杀虫脲、氟苯脲、氟虫脲、氟啶脲、除虫脲、氟铃脲、灭幼脲、氟丙氧脲)农药残留量的液相色谱-电喷雾串联质谱(LC-ESI MS/MS)测定方法。样品用乙腈提取后无需净化,经盐析过滤并以水稀释(1∶1)后,经Waters Atlantis(d C18色谱柱分离,5 mmol/L乙酸铵水溶液和乙腈梯度洗脱,以电喷雾电离串联质谱在负离子多反应监测(MRM)模式下进行测定并确证,外标法定量。8种苯甲酰脲类农药在1.0~100μg/L范围内线性良好,相关系数为0.990 0~0.999 9。对8种农药在毛豆基质中3个添加水平下的回收率进行测定,平均回收率为92%~110%,相对标准偏差为5.5%~12%。方法的检出限(S/N=3)为0.04~0.42μg/kg,定量下限(S/N=10)为0.2~1.5μg/kg。     

Chemometric analysis based on high-performance liquid chromatographic data in the fingerprint construction of selected Achillea species

Fourteen Achillea species were collected, extracted using Soxhlet apparatus with dichloromethane and methanol as solvents. The obtained methanolic extracts were analyzed using the reversed-phase high-performance liquid chromatography–diode array detector (RP-HPLC-DAD) with the Kinetex C18 column and the mobile phase consisting of methanol–water–0.1% formic acid mixture (gradient 5–85% (v/v)) at 30°C with the run time of 45?min and the detection wavelength 320?nm. Next, the chromatograms were preliminarily processed with smoothing, noise reduction, background subtraction, and alignment in the SpecAlign program (version 2.4.1) to construct the fingerprints of studied extracts. Selected standards (phenolic acids and flavonoids) were analyzed in the same chromatographic conditions and its presence in extracts was confirmed based on their spectra and the retention time values. The chemical similarity between the samples was evaluated using the Pearson correlation coefficient as similarity parameter, Euclidean distance index, the principal component analysis, and cluster analysis (CA).     

Determination of seventeen polar/thermolabile pesticides in apples and apricots by liquid chromatography/mass spectrometry

A simple liquid chromatography/mass spectrometry (LC/MS) approach for the determination of widely used representatives of polar/thermolabile pesticides in fruits was developed and validated. The group of pesticides comprised benzimidazoles and azoles (carbendazim, thiabendazole, imazalil, propiconazole, prochloraz, epoxiconazole, flusilazole, tebuconazole, bitertanol); N-methylcarbamates (carbaryl, carbofuran, methiocarb); and phenylureas and benzoylphenylureas (linuron, diflubenzuron, triflumuron, teflubenzuron, flufenoxuron). Matrixes (apple, apricot) were extracted with acetonitrile and crude extracts were cleaned up by solid-phase extraction (SPE) using either mixed cation exchange or hydrophilic lipophilic balance cartridges. LC separation of pesticides was performed on a reversed-phase column, Discovery C18. Electrospray ionization and ion trap MS/MS detection were applied. For most pesticides, overall recoveries ranged from 75 to 122%, and repeatability (as relative standard deviation) from 5 repetitive determinations of recovery ranged from 3 to 21%. Carbofuran was the only compound for which recovery was not satisfactory due to its loss in the SPE cleanup step. Limits of detection were 0.1-3 microg/kg for benzimidazole and azole fungicides and carbamate insecticides. For urea insecticides, detection limits were slightly higher (3-10 microg/kg).     

Mixture design optimization of extraction and mobile phase media for fingerprint analysis of Bauhinia variegata L

Two statistical mixture designs were used to optimize the proportions of solvents used in both the extraction medium and the reversed liquid chromatographic mobile phase to improve the quality of chromatographic fingerprints of Bauhinia variegata L extracts. For modeling, the number of peaks was used as a measure of fingerprint information. Three mobile phases, each with a chromatographic strength of two, gave good results. A methanol/water (77:23 v/v) mixture resulted in 17 peaks in the chromatographic fingerprint whereas acetonitrile/water (64.5:35.5 v/v) and methanol/acetonitrile/water (35:35:30 v/v/v) mixtures resulted in 18 and 20 peaks, respectively. The corresponding optimum solvent compositions to extract chemical substances for these three mobile phases were ethanol/acetone (25:75 v/v/v) and dichloromethane/acetone (70:30 v/v) mixtures, and pure dichloromethane, respectively. The mixture designs are useful for understanding the influence of different solvents on the strengths of the extraction medium and the mobile phase.     

Critical assessment of three high performance liquid chromatography analytical methods for food carotenoid quantification

Three sets of extraction/saponification/HPLC conditions for food carotenoid quantification were technically and economically compared. Samples were analysed for carotenoids α-carotene, β-carotene, β-cryptoxanthin, lutein, lycopene, and zeaxanthin. All methods demonstrated good performance in the analysis of a composite food standard reference material for the analytes they are applicable to. Methods using two serial connected C₁₈ columns and a mobile phase based on acetonitrile, achieved a better carotenoid separation than the method using a mobile phase based on methanol and one C₁₈-column. Carotenoids from leafy green vegetable matrices appeared to be better extracted with a mixture of methanol and tetrahydrofuran than with tetrahydrofuran alone. Costs of carotenoid determination in foods were lower for the method with mobile phase based on methanol. However for some food matrices and in the case of E–Z isomer separations, this was not technically satisfactory. Food extraction with methanol and tetrahydrofuran with direct evaporation of these solvents, and saponification (when needed) using pyrogallol as antioxidant, combined with a HPLC system using a slight gradient mobile phase based on acetonitrile and a stationary phase composed by two serial connected C₁₈ columns was the most technically and economically favourable method.     

Thin-layer chromatographic fingerprinting of the nonvolatile fraction extracted from the medicinal herb Cistus incanus L.

ABSTRACT

The aim of this study was to provide the first from-start-to-end thin-layer chromatographic method of fingerprinting the Cistus incanus L. raw herbal material, with a purpose to further use it for rapid screening, authentication, and quality control of the traded C. incanus L. herbs. To this effect, 12 different C. incanus L. samples purchased as herbal teas from a local market were extracted by means of the accelerated solvent extraction (ASE) with chemometrically optimized solvent extraction mixture and temperature (methanol–water, 27:73, v/v; 130°C), to derive the polar fraction from the plant samples. Then, the extracts were developed in two thin-layer chromatographic systems, both using the commercially precoated silica gel 60 chromatographic plates, yet two different mobile phases (mobile phase 1, ethyl acetate–formic acid–acetic acid–water, 100:11:11:13, v/v/v/v, and mobile phase 2, ethyl acetate–dichloromethane–formic acid–acetic acid–water, 100:10:10:10:11, v/v/v/v/v). The chromatograms were densitometrically scanned in the reflectance mode at the wavelength λ?=?366?nm to obtain fingerprints of the extracts derived from individual C. incanus L. samples. Mobile phase 2 performed slightly better, because with its use, the maximum number of 11 peaks could be seen in the respective fingerprints, whereas with mobile phase 1, the maximum number of 10 peaks only. Then an antioxidant potential of the investigated herbal extracts was assessed, making use of mobile phase 2 and the 0.20% methanol solution of 2,2-diphenyl picrylhydrazyl as a visualizing reagent. The resulting chromatograms were densitometrically scanned in the extinction mode at the wavelength λ?=?550?nm to obtain biological fingerprints of the extracts. Finally, chromatographic and biological fingerprints underwent a semiquantitative evaluation in terms of the contents of the extracted polar fraction and an overall antioxidant potential of the individual plant species.     

Immobilized versus coated amylose tris(3,5-dimethylphenylcarbamate) chiral stationary phases for the enantioselective separation of cyclopropane derivatives by liquid chromatography

The solvent versatility of Chiralpak IA, a new chiral stationary phase (CSP) containing amylose tris(3,5-dimethylphenylcarabamate) immobilized onto silica gel, is investigated for the enantioselective separation of a set of cyclopropane derivatives using ethyl acetate or dichloromethane (DCM) as non-standard mobile phase eluent and diluent, respectively in high-performance liquid chromatography (HPLC). A comparison of the separation of cyclopropanes on both immobilized and coated amylose tris(3,5-dimethylphenylcarbamate) chiral stationary phases (Chiralpak IA and Chiralpak AD, respectively) in HPLC using a mixture of n-hexane/2-propanol (90/10 and 99/1, v/v) as mobile phase with a flow rate of 0.5 ml/min and UV detection at 254 nm, is demonstrated. The optimized method of separation is used for an online HPLC monitoring for the Rh(II)-catalyzed asymmetric intermolecular cyclopropanations in dichloromethane. Direct analysis techniques without further purification, workup or removal of dichloromethane were summarized. The method provides an easy and direct determination of the enantiomeric excess of the cyclopropanes and selectivity of the catalyst used without any further work up.     

Improved RP-HPLC Method for Analysis of Isoquinoline Alkaloids in Extracts of Chelidonium majus

A new high-performance liquid chromatographic method has been developed for analysis of isoquinoline alkaloids in extracts of Chelidonium majus L. Samples were extracted with acidic methanol and the extracts were purified by solid-phase extraction on Supelclean LC-18 cartridges. Optimized conditions resulted in high recovery and reproducibility. Simultaneous determination of protopine, chelidonine, coptisine, sanguinarine, and berberine was performed by HPLC on a C₁₈ reversed-phase column. Use of the Luna C18(2) new-generation silica-based stationary phase and 14.7:18:67.3 (v/v) acetonitrile-methanol-30 mM ammonium formate, pH 2.80, as mobile phase resulted in excellent peak shapes. Validation proved the repeatability of the method was good and recovery was satisfactory. Lower limits of detection were 0.2 ng for coptisine, 0.4 ng for sanguinarine, and 0.5 ng, for protopine, chelidonine, and berberine.

     

Rapid sample preparation methods for analysis of residues of sulfamethazine and its N4-acetyl and desamino metabolites in swine tissue by HPLC

Rapid sample preparation methods for the determination of sulfamethazine (SMZ) and its N4-acetyl and desamino metabolites in swine tissues at the 0.1 mg kg-1 level are presented. The methods use sonication-aided extraction with dichloromethane. For SMZ and N4-acetyl SMZ analysis extracts are cleaned up and concentrated on a silica disposable column followed by HPLC on a CP Spher C8 column using acetonitrile-sodium acetate buffer as the mobile phase. For desamino-SMZ analysis the extract was cleaned up and concentrated on a Florisil disposable column, followed by HPLC on a Nucleosil 5-CN column after formation of an ion-pair complex with 1-heptanesulfonic acid. For desamino SMZ peak identification by diode-array UV/VIS detection is also described. Mean recoveries from spiked tissue samples were about 87% (muscle) and 76% (kidney) for SMZ and N4-acetyl SMZ and about 70% for desamino SMZ.     

High-performance liquid chromatographic determination of benzoylurea insecticides residues in grapes and wine using liquid and solid-phase extraction

A method for the determination of the benzoylurea insecticides diflubenzuron, triflumuron, teflubenzuron, lufenuron and flufenoxuron in grapes and wine by HPLC has been developed and validated. Grape samples (50 g) were homogenized and extracted with ethyl acetate-sodium sulfate and further cleaned-up by solid-phase extraction on silica sorbent. Wine samples (10 ml) diluted with water (1:3) were solid-phase extracted on an octadecyl sorbent using methanol as the eluent. The pesticides were separated on a reversed-phase octadecyl narrow-bore column by gradient elution and the residues were determined with a UV diode array detector. The calibration plots were linear over the range 0.05-5 micrograms/ml. Recoveries of benzoylurea pesticides from spiked grapes (0.02-2.0 mg/kg) and wine (0.01-0.2 mg/l) were 85.8-101.6% and 69.1-104.8%, respectively, and the limits of quantification for these insecticides were < 0.01 mg/kg for grapes and < 0.01 mg/l for wine. The method was applied to the determination of flufenoxuron and teflubenzuron residues in grapes from treated fields and in produced wine.     

Simultaneous LC–MS–MS Determination of Zolmitriptan and Its Active Metabolite N-Desmethylzolmitriptan in Human Plasma

A specific and sensitive liquid chromatography-electrospray ionization tandem mass spectrometry method was developed for the determination of zolmitriptan and N-desmethylzolmitriptan in human plasma. The analytes and the internal standard (IS) paroxetine were extracted by liquid–liquid extraction with a mixture of saturated ethyl acetate:dichloromethane (4:1) and were separated using an isocratic mobile phase on a XTerra RP18 column. The mobile phase used was acetonitrile: 5 mM ammonium acetate: formic acid (50:50:0.053, v/v/v). Zolmitriptan and N-desmethylzolmitriptan in a range of 0.25–20 ng mL⁻¹ were easily quantified. The validated method can be applied to pharmacokinetic and bioequivalence studies.

     

高效液相色谱法同时测定中药材亳菊中多菌灵、吡虫啉和啶虫脒的残留量

建立了同时测定中药材亳菊中多菌灵、吡虫啉和啶虫脒残留量的高效液相色谱分析方法。样品经盐酸溶液超声提取,乙醚除杂,二氯甲烷萃取后,采用ODS柱,以V(乙腈):V(0.1%磷酸,三乙胺调pH至3.6)=14:86为流动相,270nm波长处检测。结果三种农药呈良好的线性关系(r为0.9997、0.9998和0.9999),最低检出浓度分别为0.04,0.02和0.1 mg/kg。方法的平均加标回收率范围分别为:83.8%～101.3%,81.8%～90.8%和83.6%～95.0%,对应的RSD分别为:3.9%～4.3%,2.6%～3.3%和3.5%～5.9%。方法能够满足多菌灵、吡虫啉和啶虫脒在中药材亳菊中残留分析的要求。     

Determination of tenoxicam in human plasma by high-performance liquid chromatography

A high-performance liquid chromatographic method for the determination of tenoxicam in plasma has been developed. Tenoxicam was extracted from buffered plasma (pH 3 or 4, respectively) with dichloromethane and the evaporated extracts were analysed on a C18 reversed-phase column using a methanol-phosphate buffer mobile phase and with UV detection at 371 nm. The detection limit was 20 ng/ml using a 0.5-ml sample. The method is selective with respect to the 5'-hydroxy metabolite, which is present in plasma after multiple administration of tenoxicam; this metabolite may also be determined using this procedure.     

Synthesis of a stationary phase based on silica modified with branched octadecyl groups by Michael addition and photoinduced thiol–yne click chemistry for the separation of basic compounds

A novel silica‐based stationary phase with branched octadecyl groups was prepared by the sequential employment of the Michael addition reaction and photoinduced thiol–yne click chemistry with 3‐aminopropyl‐functionalized silica microspheres as the initial material. The resulting stationary phase denoted as SiO₂‐N(C18)₄ was characterized by elemental analysis, FTIR spectroscopy and Raman spectroscopy, demonstrating the existence of branched octadecyl groups in silica microspheres. The separations of benzene homologous compounds, acid compounds and amine analogues were conducted, demonstrating mixed‐mode separation mechanism on SiO₂‐N(C18)₄. Baseline separation of basic drugs mixture was acquired with the mobile phase of acetonitrile/H₂O (5%, v/v). SiO₂‐N(C18)₄ was further applied to separate Corydalis yanhusuo Wang water extracts, and more baseline separation peaks were obtained for SiO₂‐N(C18)₄ than those on Atlantis dC18 column. It can be expected that this new silica‐based stationary phase will exhibit great potential in the analysis of basic compounds.     

液相色谱-串联质谱法测定动物肝脏中黄曲霉毒素

建立了动物肝脏中黄曲霉毒素G2、G1、B2、B1的高效液相色谱-串联质谱检测方法。样品经体积比为84∶16的乙腈-水溶液提取,离心后通过真菌毒素多功能净化柱,净化液氮气吹干,用流动相定容,采用C18柱分离,10mmol/L的甲酸铵溶液和甲醇作为流动相,以50∶50比例等度洗脱,在多重反应监测(MRM)正离子模式下进行分析。各组分在9min内完全分离,方法线性关系良好,黄曲霉毒素G2、G1、B2、B1的检出限分别为0.030、0.026、0.016、0.027μg/kg,三个加标水平下平均回收率在81%～98%之间,相对标准偏差小于2%。该方法简便快速,准确可靠,可用于动物肝脏中黄曲霉毒素的测定。     

Automated screening of reversed‐phase stationary phases for small‐molecule separations using liquid chromatography with mass spectrometry

There are various reversed‐phase stationary phases that offer significant differences in selectivity and retention. To investigate different reversed‐phase stationary phases (aqueous stable C₁₈, biphenyl, pentafluorophenyl propyl, and polar‐embedded alkyl) in an automated fashion, commercial software and associated hardware for mobile phase and column selection were used in conjunction with liquid chromatography and a triple quadrupole mass spectrometer detector. A model analyte mixture was prepared using a combination of standards from varying classes of analytes (including drugs, drugs of abuse, amino acids, nicotine, and nicotine‐like compounds). Chromatographic results revealed diverse variations in selectivity and peak shape. Differences in the elution order of analytes on the polar‐embedded alkyl phase for several analytes showed distinct selectivity differences compared to the aqueous C₁₈ phase. The electron‐rich pentafluorophenyl propyl phase showed unique selectivity toward protonated amines. The biphenyl phase provided further changes in selectivity relative to C₁₈ with a methanolic phase, but it behaved very similarly to a C₁₈ when an acetonitrile‐based mobile phase was evaluated. This study shows the value of rapid column screening as an alternative to excessive mobile phase variation to obtain suitable chromatographic settings for analyte separation.     

Molecularly imprinted polymers applied to the clean-up of zearalenone and α-zearalenol from cereal and swine feed sample extracts

A molecularly imprinted polymer prepared using 1-allylpiperazine (1-ALPP) as the functional monomer, trimethyltrimethacrylate (TRIM) as the crosslinker and the zearalenone (ZON)-mimicking template cyclododecanyl-2,4-dihydroxybenzoate (CDHB) has been applied to the clean-up and preconcentration of this mycotoxin (zearalenone) and a related metabolite, alpha-zearalenol (alpha-ZOL), from cereal and swine feed sample extracts. The extraction of ZON and alpha-ZOL from the food samples was accomplished using pressurized liquid extraction (PLE) with MeOH/ACN (50:50, v/v) as the extraction solvent, at 50 degrees C and 1500 psi. The extracted samples were cleaned up and preconcentrated through the MIP cartridge and analyzed using HPLC with fluorescence detection (lambda (exc)=271/ lambda (em)=452 nm). The stationary phase was a polar endcapped C18 column, and ACN/MeOH/water 10/55/35 (v/v/v, 15 mM ammonium acetate) at a flow rate of 1.0 mL min(-1) was used as the mobile phase. The method was applied to the analysis of ZON and alpha-ZOL in wheat, corn, barley, rye, rice and swine feed samples fortified with 50, 100 and 400 ng g(-1) of both mycotoxins, and it gave recoveries of between 85 and 97% (RSD 2.1-6.7%, n=3) and 87-97% (RSD 2.3-5.6%, n=3) for alpha-ZOL and ZON, respectively. The method was validated using a corn reference material for ZON.     

Liquid chromatographic determination of aniline in table-top sweeteners based on pre-column derivatization with 1,2-naphthoquinone-4-sulfonate

A liquid chromatographic method for the determination of aniline in cyclamate sweeteners based on a pre-column derivatization with 1,2-naphthoquinone-4-sulfonate (NQS) is proposed. Aniline traces were extracted from the cyclamate samples using dichloromethane. After solvent evaporation, the dry residue was derivatized with NQS at pH 9.5 and 85 degrees C for 1 min. The aniline derivative, which was extracted from the reacting mixture, was redissolved in the eluent solution and injected into the chromatographic system. The separation of aniline derivative from other amine impurities was carried out in a C18 column using a 2% acetic acid-methanol (40:60, v/v) mobile phase. Results from the analysis of aniline in the sweetener samples with the proposed method were compared with those from the standard method. A good concordance between the two methods was observed.