固相萃取-高效液相色谱电化学法检测大鼠血浆儿茶酚胺

建立了一种Oasis HLB固相萃取-高效液相色谱（HPLC）电化学检测大鼠血浆儿茶酚胺（CAs）的方法。血浆样本在形成二苯基硼酸-儿荼酚胺复合物后经优化的固相提取技术,得到较高样本回收率。以Atlantis C18色谱柱为固定相,确定了各种影响色谱的参数,如流动相组成、pH范围及检测器的设定。儿茶酚胺所有组分肾上腺素（E）、去甲肾上腺素（NE）和多巴胺（DA）的平均提取回收率在90％～95％之间。E、NE和DA的质量浓度在0．25～30ng／mL时与峰面积呈良好的线性关系（r值分别为0．9989,0．9992和0．9984）;检出限为0．4pg。该法灵敏、准确、重现性好、结果可靠。     

Determination of cisapride in human plasma by high-performance liquid chromatography with fluorescence detection

Summary A new sensitive HPLC-FLD method has been developed and validated for the determination of cisapride in human plasma for a bioequivalence study. A gradient method was used to remove late-eluting plasma components of no interest. The separation was performed on a Li-ChroCART 250-4 Purospher RP-18 (5 μm particle) analytical column fitted with a LiChroCART 4-4 Purospher RP-18 endcapped (5 μm particle) guard column. The excitation and emission wavelengths were 295 and 350 nm during fluorescence detection. The calibration plot was linear in the range of 5–200 ng mL⁻¹. A demethoxy analogue of cisapride was used as internal standard.     

Determination of vitamin K homologues by high-performance liquid chromatography with on-line photoreactor and peroxyoxalate chemiluminescence detection

A sensitive and highly selective high-performance liquid chromatography (HPLC) method was developed for the determination of vitamin K homologues including phylloquinone (PK), menaquinone-4 (MK-4) and menaquinone-7 (MK-7) in human plasma using post-column peroxyoxalate chemiluminescence (PO-CL) detection following on-line ultraviolet (UV) irradiation. The method was based on ultraviolet irradiation (254 nm, 15 W) of vitamin K to produce hydrogen peroxide and a fluorescent product at the same time, which can be determined with PO-CL detection. The separation of vitamin K by HPLC was accomplished isocratically on an ODS column within 35 min. The method involves the use of 2-methyl-3-pentadecyl-1,4-naphthoquinone as an internal standard. The detection limits (signal-to-noise ratio = 3) were 32, 38 and 85 fmol for PK, MK-4 and MK-7, respectively. The recoveries of PK, MK-4 and MK-7 were greater than 82% and the inter- and intra-assay R.S.D. values were 1.9-5.4%. The sensitivity and selectivity of this method were sufficient for clinical and nutritional applications.     

Determination of the antidepressant paroxetine and its three main metabolites in human plasma by liquid chromatography with fluorescence detection

A high-performance liquid chromatographic method has been developed for the determination in human plasma of the specific serotonin reuptake inhibitor (SSRI) antidepressant paroxetine and its three main metabolites (M1, M2, M3). Fluorescence detection was used, exciting at λ = 294 nm and monitoring emission at λ = 330 nm for paroxetine (λ_exc = 280 nm, λ_em = 330 nm for M1 and M2; λ_exc = 268 nm, λ_em = 290 nm for M3). Separation was obtained on a reversed-phase C18 column using a mobile phase composed of 66.7% aqueous phosphate at pH 2.5 and 33.3% acetonitrile. Imipramine (λ_exc = 252 nm, λ_em = 390 nm) was used as the internal standard. A careful pre-treatment of plasma samples was developed, using solid-phase extraction with C8 cartridges (50 mg, 1 mL). The calibration curves were linear over a working range of 2.5-100 ng mL⁻¹ for paroxetine and of 5-100 ng mL⁻¹ for all metabolites. The limit of detection (LOD) was 1.2 ng mL⁻¹ for PRX and 2.0 ng mL⁻¹ for the metabolites. The method was applied with success to plasma samples from depressed patients undergoing treatment with paroxetine. Hence, the method seems to be suitable for the therapeutic drug monitoring of paroxetine and its main metabolites in depressed patients’ plasma.     

Determination of the antidepressant mirtazapine and its two main metabolites in human plasma by liquid chromatography with fluorescence detection

A high-performance liquid chromatographic method for the determination in human plasma of the recent noradrenergic and specific serotonergic antidepressant (NaSSA) mirtazapine and its two main metabolites, N-desmethylmirtazapine and 8-hydroxymirtazapine, has been developed. Fluorescence detection was used, exciting at λ = 290 nm and monitoring emission at λ = 370 nm. Separation was obtained by using a reversed-phase column (C8, 250 mm × 4.6 mm I.D., 5 μm) and a mobile phase composed of 75% aqueous phosphate buffer containing triethylamine at pH 3.0 and 25% acetonitrile. Melatonin was used as the internal standard. A careful pre-treatment of plasma samples was developed, using solid-phase extraction with phenyl cartridges (100 mg, 1 mL). The calibration curves were linear over a working range of 5-150 ng mL⁻¹ for mirtazapine and of 2.5-75.0 ng mL⁻¹ for N-desmethylmirtazapine and 8-hydroxymirtazapine. The limit of quantitation (LOQ) was 2.5 ng mL⁻¹ and the limit of detection (LOD) was 1.25 ng mL⁻¹ for all analytes. The method was applied with success to plasma samples from depressed patients undergoing treatment with mirtazapine. Precision data, as well as accuracy results, were satisfactory and no interference from other drugs was found. Hence the method is suitable for therapeutic drug monitoring of mirtazapine and its metabolites in depressed patients’ plasma.     

Analysis of triazine in water samples by solid-phase microextraction coupled with high-performance liquid chromatography

Solid-phase microextraction (SPME) coupled with high-performance liquid chromatography (HPLC) for the determination of triazine is described. Carbowax/templated resin (CW/TPR, 50 μm), polydimethylsiloxane/divinylbenzene (PDMS/DVB, 60 μm), polydimethylsiloxane (PDMS, 100 μm), and polyacrylate (PA, 85 μm) fibers were evaluated for extraction of the triazines. CW/TPR and PDMS/DVB fibers were selected for further study. Several parameters of the extraction and desorption procedure were studied and optimized (such as types of fibers, desorption mode, desorption time, compositions of solvent for desorption, soaking periods and the flow rate during desorption period, extraction time, temperature, pH, and ionic strength of samples). Both CW/TPR and PDMS/DVB fibers are acceptable; a simple calibration-curve method based on simple aqueous standards can be used. The linearity of this method for analyzing standard solution has been investigated over the range 5-1000 ng mL⁻¹ for both PDMS/DVB and CW/TPR fibers. All the correlation coefficients in the range 5-1000 ng mL⁻¹ were better than 0.995 except Simazine and Atratone by CW/TPR fiber. The R.S.D.s range from 4.4% to 8.8 % (PDMS/DVB fiber) and from 2.4% to 7.2% (CW/TPR fiber). Method-detection limits (MDL) are in the range 1.2-2.6 and 2.8-3.4 ng mL⁻¹ for the two fibers. These methods were applied to the determination of trazines in environmental water samples (lake water).     

Determination of glutathione content in grape juice and wine by high-performance liquid chromatography with fluorescence detection

A modified preparation of sample was developed for the determination of glutathione content in grape juice and wine by high-performance liquid chromatography with fluorescence detection, using on-line pre-column derivatization. Ice-cold deoxygenated methanol was used to deactivate the oxidation enzymes in juices or wines and keep the glutathione stable. The optimum recovery of glutathione content in grape juice and wine was obtained when either the sample of grape juice or wine was mixed in ice-cold deoxygenated methanol in the ratio 10:90 (v:v) and further diluted in sodium acetate buffer in the ratio 1:1 (v:v). The optimized method was validated for linearity, limit of detection, limit of quantification, precision and uncertainty. According to the validation data the method is appropriate for the determination of glutathione content in grape juice and wine. Glutathione contents in grape juices made from White Muscat grapes and Sauvignon Blanc wines were analysed. The average glutathione content in 28 young Sauvignon Blanc wines was 12.5 mg L⁻¹.     

Determination of thiamine in blood serum and urine by high-performance liquid chromatography with direct injection and post-column derivatization

Thiamine (vitamin B₁) was determined in human serum and urine by HPLC with fluorimetric detection of its oxidation product, thiochrome. The samples were injected directly into the chromatographic system without previous treatment or dilution. A column filled with an ultra-high molecular weight surface-modified polyethylene (PE) was able to separate matrix components from analyte and also to allow a good chromatographic resolution of thiamine. The interaction of thiamine, thiocrome and both matrices (serum and urine) with PE was studied off- and on-line to determine the optimal procedure for vitamin B₁ determination. When carried off-line, matrix adsorption yield was 49 mg serum proteins/g polymer and components of 1000 μl urine/g polymer. In an on-line arrangement, the yield dropped to 10 mg/g and 150 μl/g, respectively. The matrix/analyte separation was carried out in an on-line procedure on a 50×4.6-mm, 25-μm PE column, using a water-sodium phosphate-methanol gradient elution. Part of the matrix was eluted within the first 2 min and thiamine after 3.8 min. The rest of the matrix retained on the column was eluted after thiamine at the last step of the gradient elution. Analysis time was 12 min. The within-day and day-to-day precision gave C.V. varying from 3.6% to 14.5% and recoveries from spiked samples were in the range of 84.8-98.8%.     

New scandium rhodium boride Sc<Subscript>4</Subscript>Rh<Subscript>17</Subscript>B<Subscript>12</Subscript> with a framework structure: synthesis,crystal structure,and properties

The new scandium rhodium boride Sc₄Rh₁₇B₁₂ was synthesized by arc-melting of the elements followed by annealing in inert atmosphere. The crystal structure of Sc₄Rh₁₇B₁₂ was solved using single crystal X-ray diffraction data. The structure can be described as a three-dimensional frame-work formed by trigonal prisms [BRh₆] and [BRh₅Sc] with isolated boron atoms inside the prisms and trigonal prisms [BRh₅B] representing the coordination polyhedra of paired boron atoms. The temperature dependences of the magnetic susceptibility and specific resistance of Sc₄Rh₁₇B₁₂ revealed that the compound is a Pauli paramagnet and shows metal-like specific resistance.     

Study of solid-phase extraction for the determination of sequestering agents in river water by high-performance liquid chromatography

Anion-exchange solid-phase extraction accompanied with high-performance liquid chromatography has been developed for the determination of six kinds of aminopolycarboxylic acids (APCAs) in river water [N-(2-hydroxyethyl)ethylenediaminetriacetate (HEDTA), ethylenediaminetetraacetate (EDTA), 1,3-propanediaminetetraacetate (PDTA), diethylenetriaminepentaacetate (DTPA), 1,2-propanediaminetetraacetate (MeEDTA), and O,O′-bis(2-aminoethyl)ethyleneglycoltetraacetate (GEDTA)]. The enrichment of APCAs using an anion-exchange cartridge was successfully done by the removal of anions, which competed with APCAs in anion-exchange processes. Barium chloride solution was added to river water and the mixture was passed through On Guard II Ag and H cartridges and then a Bond Elut Jr.SAX cartridge to enrich APCAs. After elution, APCAs were analyzed on two reversed phase C30 columns connected in series and detected with ultraviolet detection. The enrichment using solid-phase extraction permitted the determination of APCAs in river water at concentrations as low as 1 nM. Good recoveries (83–111%) were obtained for each APCA by the standard addition method on three river water samples with high accuracy (RSD 1.8–9.5%). Applying this method, two kinds of APCAs, EDTA and DTPA, were determined in samples from the Oyabe and Senbo Rivers in Japan.     

Quantitative plasma determination of a novel antiretroviral derivative of zidovudine by solid-phase extraction and high-performance liquid chromatography

A solid-phase extraction methodology, followed by high-performance liquid chromatography (HPLC) quantification with UV absorbance detection (λ=267 nm), was developed in order to study the stability of 3′-azido-3′-deoxy-5′-O-isonicotinoylthymidine (AZT-Iso), a novel derivative of the antiretroviral AZT, in different matrixes. The half-lives (t _1/2) for AZT-Iso were 1.19, 1.13 and 0.30 h for human, rat and rabbit plasma, respectively, and 14.91 and 25.49 h for potassium phosphate buffer (pH 7.4) and human serum albumin solution, respectively. The HPLC method proved to be selective, sensitive and accurate. Good recovery, linearity and precision were achieved using p-fluorophenol as an internal standard. The validity of this method was tested using synthetic mixtures of the intact drug with its decomposition products. In conclusion, the method presented is applicable to in vivo pharmacokinetics studies of AZT-Iso in rats.     

Quantification of several monohydroxylated metabolites of polycyclic aromatic hydrocarbons in urine by high-performance liquid chromatography with fluorescence detection

A high-performance liquid chromatographic method with fluorescence detection has been developed to determine the urinary polycyclic aromatic hydrocarbon metabolites 2-hydroxynaphthalene, 2-hydroxyfluorene, 9-hydroxyphenanthrene, 1-hydroxypyrene and 3-hydroxybenz[a]pyrene. Solid phase extraction (SPE) was used to clean up the samples, and washing with 30% methanol was found to be the best way to remove interferences in the matrix. The method detection limits ranged from 0.044 μg/L for 1-hydroxypyrene to 1.615 μg/L for 3-hydroxybenz[a]pyrene, and the recoveries ranged between 40% for 3-hydroxybenz[a]pyrene and 99% for 2-hydroxynaphthalene. The within-day relative standard deviation was lowest for 2-hydroxynaphthalene at 0.67% and went up to 2.42% for 3-hydroxybenz[a]pyrene, and the between-day relative standard deviation ranged from 3.84% for 9-hydroxyphenanthrene to 10.42% for 2-hydroxyfluorene. The correlation coefficients were between 0.9962 and 0.9998. The developed method was successfully used to analyze samples from student volunteers in a high school.     

Analysis of meloxicam by high-performance liquid chromatography with cloud-point extraction

A simple cloud-point extraction method for the determination of meloxicam in human serum was developed. Meloxicam was extracted from serum sample after adding 1 mL of 3% (v/v) Triton X-114 aqueous solution in the presence of 1M HCl and 60 mg NaCl. The meloxicam, present in the surfactant-rich phase, was enriched again with acetonitrile. Tenoxicam was used as the external standard. The separation was achieved on a C18 analytical column with a mobile phase consisting of aqueous acetic acid (1%, v/v) and acetonitrile (54:46, v/v). UV detection was performed at 360 nm. The response was linear over the range 45–2000 ng mL⁻¹ in human serum, and intra- and interday precisions of less than 15.0% were obtained. The relative error was within ±3.0%. The recoveries of meloxicam were larger than 92.0%. The method was compared with liquid–liquid extraction. The results showed that the new method has a considerable LOQ and higher recoveries but poorer precision than liquid–liquid extraction, which exhibited poor recoveries of less than 86.0%, precisions of less than 5.0% and relative errors of less than 7.0%. The method was used for the determination of meloxicam in healthy human volunteers.     

Determination of methoxsalen in dosage forms by high-performance liquid chromatography

Summary A new, rapid, sensitive, and specific method for the determination of methoxsalen in dosage forms using HPLC has been developed. methoxsalen is extracted in chloroform, evaporated on a water bath, and the residue is redissolved in ethanol. A standard solution of khellin (internal standard) in ethanol is added, and injected. A plot of peak height ratio (methoxsalen/internal standard) vs. concentration of methoxsalen gave a straight line (r=0.998). The column used was a stainless steel, 3.8 mm×30 cm, and the mobile phase was methanol: water (6040) at a flow rate of 2 cm³/min. Retention times for methoxsalen and khellin were 3.45 and 9.6 min, respectively. This method was found superior to the spectrophotometric assay in that no interference was encountered from structurally similar compounds or from coloring agents used in some commercial methoxsalen products.     

Determination of vitamin K<Subscript>1</Subscript> in blood serum by high-performance liquid chromatography

A method is proposed for the determination of vitamin K₁ concentration in blood serum using HPLC on a Gemini C18 (250 mm × 4.6 mm ID, 5 μm) column and elution with a methanol–acetonitrile–dichloromethane (45 : 50 : 5, v/v) mobile phase at a flow rate of 1 mL/min and detection at 248 nm. The limit of detection for the vitamin is 0.5 ng/mL and relative error is 19%. The volume of sample in the column is 100 μL. The method has been applied to the evaluation of vitamin K₁ deficit in a human body in medical practice.     

Fingerprint analysis of Dioscorea nipponica by high-performance liquid chromatography with evaporative light scattering detection

High-performance liquid chromatographic method (HPLC) with evaporative light scattering detection (ELSD) coupled with microwave-assisted extraction (MAE) as an efficient sample preparation technique has been developed for fingerprint analysis of Dioscorea nipponica. The samples were separated with an Agilent C8 column using water (A) and acetonitrile (B) under gradient conditions (0-10 min, linear gradient 20-40% B; 10-12 min, linear gradient 40-42% B; 12-25 min, isocratic 42% B) as the mobile phase at a flow rate of 1 mL min⁻¹ within 22 min. The ELSD conditions were optimized at nebulizer-gas flow rate 2.7 L min⁻¹ and drift tube temperature 90 °C. Precision experiments showed relative standard deviation (R.S.D.) of peak area and retention time were better than 2.5%; inter-day and intra-day variabilities showed that R.S.D. was ranged from 0.78% to 4.74%. Limit of detection was less than 50 μg mL⁻¹ and limit of quantification was less than 80 μg mL⁻¹. Accuracy validation showed that average recovery was between 97.39% and 104.07%. The method was validated to achieve the satisfactory precision and recovery. Relative retention time and relative peak area were used to identify the common peaks for fingerprint analysis. There are nine common peaks in the fingerprint. The quality of seven batches of D. nipponica samples was evaluated to be qualified or unqualified by the parameters “difference” and “total difference” of common peaks. Furthermore, the contents of important medicinal compounds (dioscin, prodioscin and gracillin) in different batches of D. nipponica samples were determined simultaneously using the developed HPLC-ELSD method. The results indicated variation of the herb quality which might be related to different producing area, growing condition, climate, harvest time, drug processing and so on. The developed analytical procedure was proved to be a reliable and rapid method for the quality control of D. nipponica.     

Determination of thiol by high-performance liquid chromatography and fluorescence detection with 5-methyl-(2-(<Emphasis Type="Italic">m</Emphasis>-iodoacetylaminophenyl)benzoxazole

A new high-performance liquid chromatographic (HPLC) method for measuring low molecular weight (LMW) thiol-containing compounds, including cysteine (CysH), glutathione (GSH), N-acetylcysteine (Nac), penicillamine (PA), and 2-mercaptoethanol (2-ME), has been developed by using 5-methyl-(2-(m-iodoacetylaminophenyl)benzoxazole (MIPBO) as fluorescence-labeling reagent. The derivatization and separation conditions have been investigated in detail. Detection limits ranging from 3.5 to 15.0 fmol were achieved for the thiols investigated in a 16 min separation with detection wavelengths 310 and 375 nm for the excitation and emission, respectively. The utility of the proposed method has been validated by measuring CysH in human urine samples.     

Hydrothermal synthesis and thermodynamic properties of 2CaO·3B<Subscript>2</Subscript>O<Subscript>3</Subscript>·H<Subscript>2</Subscript>O

2CaO·3B₂O₃·H₂O which has non-linear optical (NLO) property was synthesized under hydrothermal condition and identified by XRD, FTIR and TG as well as by chemical analysis. The molar enthalpy of solution of 2CaO·3B₂O₃·H₂O in HCl·54.572H₂O was determined. From a combination of this result with measured enthalpies of solution of H₃BO₃ in HCl·54.501H₂O and of CaO in (HCl+H₃BO₃) solution, together with the standard molar enthalpies of formation of CaO(s), H₃BO₃(s), and H₂O(l), the standard molar enthalpy of formation of −(5733.7±5.2) kJ mol⁻¹ of 2CaO·3B₂O₃·H₂O was obtained. Thermodynamic properties of this compound were also calculated by a group contribution method.     

Features of laser desorption/ionization mass spectrometry fragmentation of vitamin B<Subscript>12</Subscript>

A comparative analysis of the laser desorption/ionization of vitamin B₁₂ by matrix-assisted laser desorption/ionization (MALDI) and desorption/ionization on porous silicon (DIOS) was carried out. The mass spectra obtained were interpreted and the pathways for ion formation and decomposition were established. The MALDI fragmentation of the positive vitamin B₁₂ ions is more extensive than the DIOS fragmentation. The most extensive fragmentation was found using the MALDI method for negative vitamin B₁₂ ions, which are lacking when using the DIOS method. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 43, No. 4, pp. 251–256, July–August, 2007.     

Determination of cobalamins (hydroxo-, cyano-, adenosyl- and methyl-cobalamins) in seawater using reversed-phase liquid chromatography with diode-array detection

A high-performance liquid chromatography method was developed for the separation and determination of four cobalamins in seawater. Chromatographic separation was performed on a reversed-phase discovery RP-amide C₁₆ column with buffer potassium dihydrogenphosphate and acetonitrile as the mobile phases in linear gradients elution mode. Cobalamins were previously preconcentrated in C₁₈ resins cartridges. Detection was performed using UV-diode array detector in a range of λ of 200–400 nm. The method showed to be linear over a range of 1–300 ng mL⁻¹ with acceptable precision and accuracy. The detection limits ranged between 0.07 pg mL⁻¹ for 5′-deoxyadenosylcobalamin and 0.5 pg mL⁻¹ for hydroxocobalamin. The mean cobalamins recoveries for direct determination ranged between 76 and 93% for hydroxo-, cyano- and methylcobalamin, while the recovery for 5′-deoxyadenosylcobalamin was only 31% suggesting that the preconcentration method was not valid for this cobalamin. The method was successfully applied to coastal seawater where the concentrations ranged from 4.2 to 7.3 ng L⁻¹ for hydroxo-, 1.4–3.9 ng L⁻¹ for cyano-, 2.1–4.6 ng L⁻¹ for 5′-deoxyadenosyl- and 33–83.5 ng L⁻¹ for methylcobalamin.