Simultaneous determination of acetaminophen, dextromethorphen hydrobromide and pseudoephedrine hydrochloride in a new drug formulation for cold treatment by HPLC

Summary A rapid and accurate HPLC method is described for the simultaneous determination of acetaminophen, dextromethorphen hydrobromide and pseudoephedrine hydrochloride in a new cold formulation. Chromatographic separation of the three pharmaceuticals was performed on a Hypersil CN column (150×5.0 mm, 5 μm) with a mobile phase mixture of an ion-pairing solution, methanol and acetonitrile (25:57:18, v/v), at a flow rate of 1.0 mL min⁻¹, with detection at 220 nm. Separation was complete in less than 10 min. The method was validated for linearity, accuracy, precision, limit of quantitation and robustness. Linearity, accuracy, and precision were found to be acceptable over the ranges of 2.06∼20.6 μg·mL⁻¹ for acetaminophen, 0.202∼2.02 mg·mL⁻¹ for pseudoephedrine hydrochloride and 0.042∼1.06 mg·mL⁻¹ for dextromethorphen hydrobromide.     

Preparation of a novel polymer gel electrolyte based on N-methyl-quinoline iodide and its application in quasi-solid-state dye-sensitized solar cell

Using poly(acrylonitrile-co-styrene) as polymer host, 1,2-propanediol carbonate, dimethyl carbonate and ethylene carbonate as mixture solvent, N-methyl-quinoline iodide and iodine as the source of I⁻/I₃ ⁻, a novel polymer gel electrolyte with ionic conductivity of 5.12 × 10⁻³ S· cm⁻¹ at 25°C was prepared by sol-gel and hydrothermal methods. Based on the polymer gel electrolyte, a quasi-solid-state dye-sensitized solar cell was fabricated. The solar cell possess better long-term stability and light-to-electrical energy conversion efficiency of 4.04% under irradiation of 100 mW· cm⁻². The influences of polymer host, solvent, N-methyl-quinoline iodide and temperature on ionic conductivity of the polymer gel electrolyte and the performance of the dye-sensitized solar cell was discussed.     

Determination of vitamin B<Subscript>1</Subscript> in seawater and microalgal fermentation media by high-performance liquid chromatography with fluorescence detection

A highly sensitive high-performance liquid chromatographic method with fluorescence detection has been developed for determination of vitamin B₁. Vitamin B₁ was converted into a fluorescent compound by treatment with hydrogen peroxide–horseradish peroxidase and the derivative was subsequently analyzed by HPLC on a Waters Spherisorb ODS2 column (250 mm×4.6 mm ID, 5 μm) with 40:60 methanol–pH 8.5 acetate buffer solution as mobile phase and fluorescence detection at 440 nm (with excitation at 375 nm). The calibration graph was linear from 5.00×10⁻¹⁰ mol L⁻¹ to 5.00×10⁻⁷ mol L⁻¹ for vitamin B₁ with a correlation coefficient of 0.9991 (n=9). The detection limit was 1.0×10⁻¹⁰ mol L⁻¹. The method was successfully used for determination of vitamin B₁ at pg mL⁻¹ levels in microalgal fermentation media and seawater after solid-phase extraction. Recovery was from 89 to 110% and the relative standard deviation was in the range 1.1 to 4.3%.     

Determination of sulfanilamide based on the Mn(II)-catalyzed oscillating chemical reaction

A convenient and sensitive method for determination of sulfanilamide (SNA) was described based on the Mn(II)-catalyzed oscillating chemical reaction. Under optimum conditions, a linear relationship existed between the changes of oscillating period or amplitude and the negative of logarithm of SNA concentration in the range of 4.27 × 10⁻⁸ mol ·L⁻¹ ∼ 7.41 × 10⁻⁶ mol ·L⁻¹ (RSD, 0.85%) and 9.33 × 10⁻⁸ mol ·L⁻¹ ∼ 3.02 × 10⁻⁶ mol ·L⁻1 (RSD, 1.08%), respectively. The lower limit of detection was found to be 2.69 × 10⁻⁸ mol ·L⁻¹ and 6.03 × 10⁻⁸ mol ·L⁻¹, respectively.      

Determination of molecular weights and Mark–Houwink constants for soluble electronically conducting polymers

Intrinsic viscosities and gel permeation chromatography data were used to evaluate the Mark–Houwink constants of the soluble electronically conducting polymer, poly(3-hexylthiophene) (P3HT):K and a are 2.28 × 10^-3 cm³/g and 0.96, respectively, in tetrahydrofuran (THF) at 25°C. Mark–Houwink constants were used to calibrate gel permeation chromatography (GPC) columns for P3HT. Number-average molecular weights of P3HT determined with modified calibration curves agreed well with those determined by an absolute method, embulliometry. Molecular weights estimated using unmodified polystyrene calibration procedures were significantly larger than true values.     

SOLUTION PROPERTIES OF LADDER-LIKE POLYMER POLYPHENYLSILSESQUIOXANES

Solution properties of ladder-like polymer polyphenylsilsesquioxane (PPS) were studied by measurement of intrinsic viscosity, small angle laser light scattering and gel permeation chromatography. It was found that PPS can be modeled with a wormlike continuous cylinder rather than a wormlike coil. A plot of (M~2/[η])~(1/3) vs. M~(1/2) was employed in obtaining the persistence length (2λ)~(-1) and effective hydrodynamic diameter. When MW≤5×10~5, Mark-Houwink equation is adequate in describing the relationship between MW and [η] with αabout unity. This implies that PPS chain is semi-stiff. For GPC experiments, it was shown that universal calibration can be applied in PPS. When molecular weights of PPS are sufficiently high, their molecular weight distributions are often very broad.     

Simultaneous Determination of Palladium, Platinum and Rhodium by On-Line Column Enrichment and HPLC with 4-Hydroxy-1-Naphthalthiorhodanine as Pre-Column Derivatization Reagents

In this paper, 4-hydroxy-1-naphthalthiorhodanine (HNTR) was synthesized, and a new method for the simultaneous determination of palladium, platinum and rhodium ions as metal-HNTR chelates was developed using rapid column high-performance liquid chromatography combined with on-line enrichment. The palladium, platinum and rhodium ions were pre-column derivatized with HNTR to form colored chelates. The Pb-HNTR, Pt-HNTR and Rh-HNTR chelates could be absorbed onto the front of the enrichment column when they were injected into the injector and sent to the enrichment column [ZORBAX Stable Bound, 4.6 × 10 mm, 1.8 μm] with a buffer solution of 0.05 mol L⁻¹ sodium acetate-acetic acid (pH 4.0) as mobile phase. After enrichment, and by switching the six-ports switching valve, the retained chelates were back-flushed by mobile phase and traveling towards the analytical column. Separation of these chelates on the analytical column [ZORBAX Stable Bound, 4.6 × 50 mm, 1.8 μm] was satisfactory with 68% acetonitrile (containing 0.05 mol L⁻¹ of pH 4.0 sodium acetate-acetic acid buffer salt and 0.1% of tritonX-100) as mobile phase. Palladium, platinum and rhodium were separated completely within 2 min. The detection limits (S/N = 3) of palladium, platinum and rhodium are 1.2 ng L⁻¹, 1.5 ng L⁻¹ and 1.8 ng L⁻¹, respectively. This method was applied to the determination of palladium, platinum and rhodium in water, urine and soil samples with good results.     

Ensemble of carbon fiber ultra-microelectrodes modified with nanotubes, and its application to the determination of dopamine

An ensemble of carbon fibers ultra-microelectrode modified with carbon nanotubes (EUME-CNTS) has been constructed based on a thin carbon nanotubes film which was coated onto surfaces of carbon fibers of ultra-microelectrode. SEM micrographs illustrated the image of carbon nanotubes on the carbon fiber surface. The electrochemical characteristics of the EUME-CNTS has been investigated by cyclic voltammetry. The electrochemical properties of dopamine on this electrode were also studied, and the detection limit was found to be 2.0 × 10⁻⁹ mol·L⁻¹. Linear calibration plots were obtained for the oxidation peak current in a range 1.0 × 10⁻⁷–8.0 × 10⁻⁵ mol·L⁻¹. Correspondence: Xiuhua Liu, Kuaizhi Liu, Department of Chemistry and Chemical Engineering, Henan University, Henan Kaifeng 475001, P.R. China     

Size Exclusion Chromatography of Nonionic and Anionic Copolymers of Vinylpyrrolidone

Abstract

Size exclusion chromatography (SEC) of poly(vinylpyrrolidoneco-vinylacetate), PVPVA, and poly(vinylpyrrolidone-co-dimethylamincethylmethacrylate-co-vinylcaprolactan),PVPDMMAEMAVC, is evaluated in terms of resolution between polymer and solvent peaks using aqueous and nonaqueous mobile phases. A 1:1 (v/v) water/methanol, 0.1M LiNO₂ mobile phase is used with four Waters Ultrahydrogel columns with pore sizes of 120Å, 500Å, 1000Å, and 2000Å. DMF, 0.1M LiNO₃ mobile phase is used with three different two column sets. Two of the column sets are comprised of a mixed bed packing of poly(styrene-co-divinyl benzene), obtained from Shodex (KD80M), followed by either an Ultrahydrogel 120Å or a PLge1 100Å. The third two column set is a PLge1 10⁴Å followed by a PLgel 500Å. Any of the second columns in these sets improve separation between the trailing end of the polymer peak and the leading end of the solvent peak but the column set using an Ultrahydrogel 120Å yields a separation of these peaks whose valley is closer to the baseline. The aqueous mobile phase with the four column set yields a separation between the trailing end of the polymer peak and the leading end of the solvent peak whose valley is closest to the baseline. Recovery of PVPVA and PVPDMAEMAVC from the columns evaluated is 100%. Vinylpyrrolidone compositions of PVPVA ranging from 30 to 70 mole % were studied using both mobile phases. SEC of     

超高效液相色谱法测定水果和饮料中残留的氟嘧菌酯和嘧螨酯

建立了多种水果和饮料中氟嘧菌酯和嘧螨酯残留的超高效液相色谱测定方法。样品用乙酸乙酯-环己烷(体积比为1∶1)超声波萃取,凝胶渗透色谱法净化,超高效液相色谱-二极管阵列检测器检测,外标法定量。采用BEH C18色谱柱(50 mm×2.1 mm,1.7 μm),流动相为水-乙腈(体积比为3∶7),流速为0.3 mL/min,柱温为40 ℃,紫外检测波长为251 nm。实验结果表明：氟嘧菌酯和嘧螨酯在0.05～2 mg/L范围内线性关系良好(r>0.999),在不同的基质中添加3个浓度水平(0.01,0.05,0.1 mg/kg)的氟嘧菌酯和嘧螨酯,两者的回收率均在82.60%～101.11%之间,相对标准偏差为5.4%～15.3%;检出限不大于6 μg/kg,定量限不大于20 μg/kg。     

Determination of Yttrium by Resonance Light Scattering Technique

 Yttrium was determined by means of the resonance light scattering (RLS) technique. The characteristics of resonance light scattering spectra of yttrium-1, 6-bi(1′-phenyl-3′-methyl-5′-pyrazolone-4′-) hexanedione (BPMPHD), the effective factors and optimum conditions were studied. In the pH range of 5.0–6.1, yttrium-BPMPHD complex produces three characteristic peaks of RLS at 365, 402 and 467 nm. The enhanced intensity of RLS is proportional to the concentration of yttrium in the range of 1.0×10⁻⁸ to 1.0×10⁻⁵ mol · L⁻¹. The limit of detection is 5.9×10⁻⁹ mol · L⁻¹. The method has been used for the determination of Y³⁺ in mixed rare earths. Correspondence: Key Lab for Colloid and Interface Chemistry of Education Ministry, School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, People’s Republic of China. e-mail: wux@sdu.edu.cn Received July 3, 2002; accepted October 20, 2002     

Application of gel permeation chromatography to polyelectrolytes: Salt rejection mechanism and molecular-weight distribution

Gel permeation chromatography (GPC) of polyelectrolytes in dimethylformamide (DMF) is studied. Three methods of monitoring elution (conductimetry, viscosimetry, refractometry) are used to investigate the molecular-weight distribution and, independently, the chemical composition expressed in terms of the ionic charge density as a function of the chain length in two copolymers of acrylonitrile and sodium methallylsulfonate. The distribution on the gel of the neutral salt NaNO₃ added to the DMF and used for elution is discussed in terms of Donnan exclusion; in addition, it is concluded that to obtain the correct molecular-weight distribution, GPC measurements must be performed with an eluent containing a neutral salt at a concentration at least 5 × 10^?2M to prevent electrostatic exclusion. The main difficulty in reaching rigorous conclusions comes from the dependence of the calibration curve on the salt composition of the eluent owing to interactions—dependent on the quality of the solvent—between the polystyrenes used as standards and the porous silica gel. Nevertheless, this perturbation is small and the agreement between the average molecular weights obtained by GPC and by direct determination is good and indicates that the universal calibration proposed for neutral polymers is also valid for polyelectrolytes.     

Characterization of Polyphenylene Sulfide Using Gel Permeation Chromatography with Triple Detection

The increasing world demand for polyphenylene sulfide (PPS) due to its unique properties has augmented the pressure on development of analytical methods to evaluate its molecular weight distribution and structure. Whilst gel permeation with triple detection (GPC3D) has been considered for PPS analysis, its development and effectiveness has been impaired because of, firstly, the high temperature needed to maintain solubility (>205°C), and, secondly, a very low dn/dc for the polystyrene calibration standards in 1-chloronaphthalene. This article presents practical recommendations to overcome these early difficulties by discussing the results obtained on PPS samples analyzed with a commercially available GPC3D instrument.     

Simultaneous determination of hydrochlorothiazide and losartan potassium in tablets by high-performance low-pressure chromatography using a multi-syringe burette coupled to a monolithic column

This contribution describes use of a separation method based on on-line coupling of a multisyringe flow system with a chromatographic monolithic column for simultaneous determination of hydrochlorothiazide and losartan potassium in tablets. The system comprised a multisyringe module, three low-pressure solenoid valves, a monolithic C₁₈ column (25 mm × 4.6 mm i.d.), and a diode-array detector. The mobile phase was 10 mmol L⁻¹ potassium dihydrogen phosphate (pH 3.1)-acetonitrile-methanol (65:33:2 v/v/v) at a flow rate 0.8 mL min⁻¹. UV detection was carried out at 226 nm. The multi-syringe chromatographic (MSC) method with UV spectrophotometric detection was optimized and validated. Results from validation were very good. The analysis time was about 400 s. The method was found to be applicable to routine analysis of both compounds in tablets. The coupling of the monolithic columns with a multi-syringe flow-injection analysis manifold provides an excellent and inexpensive tool to solve the separation problems without use of HPLC instrumentation.     

RP-LC Determination and Pharmacokinetic Study of Ferulic Acid and Isoferulic Acid in Rat Plasma After Taking Traditional Chinese Medicinal-Preparation: Guanxinning Lyophilizer

A sensitive, simple, and accurate method for determination and pharmacokinetic study of ferulic acid and isoferulic acid in rat plasma was developed using a reversed-phase column liquid chromatographic (RP-LC) method with UV detection. Sample preparations were carried out by protein precipitation with the addition of methanol, followed by evaporation to dryness. The resultant residue was then reconstituted in mobile phase and injected into a Kromasil C₁₈ column (250 × 4.6 mm i.d. with 5 μm particle size). The mobile phase was methanol-1% formic acid (33:67, v/v). The calibration plots were linear over the range 5.780–5780 ng·mL⁻¹ for ferulic acid and 1.740–348.0 ng·mL⁻¹ for isoferulic acid. Mean recoveries were 85.1% and 91.1%, respectively. The relative standard deviations (RSDs) of within-day and between-day precision were not above 15% for both of the analytes. The limits of quantification were 5.780 ng·mL⁻¹ for ferulic acid and 1.740 ng·mL⁻¹ for isoferulic acid. This RP-LC method was used successfully in pharmacokinetic studies of ferulic acid and isoferulic acid in rat plasma after intravenous injection of Guanxinning Lyophilizer.

     

Fluorimetric determination of traces of europium(III) using a new chelator and acetate or phosphate in dimethylsulfoxide as enhancers

A new Schiff-base ligand [N, N′, N″-Tri- (2,4-dihydroxyacetophenone) – triaminotriethylamine (TDATA)] with a tripodal structure was synthesized. Its fluorescence intensity with the europium(III) complex was increased about 178-fold in the presence of sodium acetate (NaAc) and about 126-fold in the presence of sodium phosphate (Na₃PO₄) solution. After adding the organic solvent dimethylsulfoxide (DMSO) to the above system, which leads to Eu³⁺ the fluorescence was further enhanced about 12-fold. Spectrofluorimetric determination of trace amounts of Eu³⁺ based on the phenomenon was performed. The excitation and emission wavelength is 365 nm and 615 nm, respectively. Under optimum conditions, the fluorescence intensities vary linearly with the concentration of Eu³⁺ in the range of 4.9 × 10⁻¹²–3.2 × 10⁻⁶ mol · L⁻¹ with a detection limit of 4.5 × 10⁻¹² mol · L⁻¹ (for the TDATA-NaAc-DMSO system) or 6.2 × 10⁻¹¹–8.6 × 10⁻⁶ mol · L⁻¹ with a detection limit of 6.0 × 10⁻¹¹ mol · L⁻¹ (for the TDATA-Na₃PO₄-DMSO system). Interferences of some rare earth metals and other inorganic ions are described. The method is a selective, sensitive, rapid and simple analytical procedure for the determination of europium(III) in a high purity yttrium oxide and synthetic sample. The mechanism for the fluorescence enhancement is also discussed.     

Peak compression in semi-preparative supercritical fluid chromatography

Summary Peak compression of a dihydropyridine drug, clevidipine, is obtained in both analytical and semi-preparative scale supercritical fluid chromatography, resulting in extremely high apparent efficiencies. The observed effect, when utilising a carbon dioxide/2-propanol mobile phase with a bare silica stationary phase, is achieved when the retention of the clevidipine peak is controlled to coalesce with a system peak, generated as a result of having water in the sample. Apparent efficiencies of 350,000 and 170,000 plates meter⁻¹ were obtained when 0.25 and 0.5 mg, respectively, are directly injected to a 200×4.6 mm ID 5 μm Hypersil silica packed column. The effect was extended to a semi-preparative system where apparent efficiencies in the region of 2,000,000 plates meter⁻¹ were observed when 0.3 mg of a clevidipine sample containing 80% water was injected to a 250×10 mm I.D. column containing 5-μm Hypersil silica particles.     

Voltammetric study of the interaction of the ofloxacin–copper complex with DNA, and its analytical application

The electrochemical behavior of the ofloxacin–copper complex, Cu(II)L₂, at a mercury electrode, and the interaction of DNA with the complex have been investigated. The experiments indicate that the electrode reaction of Cu(II)L₂ is an irreversible surface electrochemical reaction and that the reactant is of adsorbed character. In the presence of DNA, the formation of the electrochemically non-active complexes Cu(II)L₂-DNA, results in the decrease of the peak current of Cu(II)L₂. Based on the electrochemical behavior of the Cu(II)L₂ with DNA, binding by electrostatic interaction is suggested and a new method for determining nucleic acid is proposed. Under the optimum conditions, the decrease of the peak current is in proportional to the concentration of nucleic acids in the range from 3 × 10⁻⁸ to 3 × 10⁻⁶ g · mL⁻¹ for calf thymus DNA, from 1.6 × 10⁻⁸ to 9.0 × 10⁻⁷ g · mL⁻¹ for fish sperm DNA, and from 3.3 × 10⁻⁸ to 5.5 × 10⁻⁷ g · mL⁻¹ for yeast RNA. The detection limits are 3.3 × 10⁻⁹, 6.7 × 10⁻⁹ and 8.0 × 10⁻⁹ g · mL⁻¹, respectively. The method exhibits good recovery and high sensitivity in synthetic samples and in real samples.     

Separation of15N by chemical exchange in NO, NO2−HNO3 system under pressure

The basic isotopic exchange reaction is responsible for the separation of¹⁵N in the Nitrox system that between gaseous nitrogen oxides and aqueous nitric acid with a single stage separation factor α=1.055 for 10M nitric acid, at 25°C and atmospheric pressure takes place. In order to know what happens in¹⁵N separation at higher pressure, when the isotopic transport between two phases is improved, a stainless steel laboratory experimental plant with a 1000 mm long × 18 mm i.d. column, packed with triangular wire springs 1.8×1.8×0.2 mm², was utilised. At 1.5 atm (absolute), and 2.36 ml·cm⁻²·min⁻¹ flow rate HETP was 7% smaller than at atmospheric pressure and 1.5 times smaller flow rate. HETP at 3.14 ml·cm⁻²·min⁻¹ flow rate and 1.8 atm is practically equal with that obtained at atmospheric pressure and 2 times smaller flow rate. The operation of the¹⁵N separation plant at 1.8 atm (absolute), instead of atmospheric pressure, will permit doubling of the 10M nitric acid flow rate and of¹⁵N production of the given column.     

Study of adsorption kinetics for fluorescent whitening agent on fiber surfaces

Adsorption kinetics for a stilbene derivative type fluorescent whitening agent (FWA) on fiber surfaces was studied based on a real-time spectroscopic measurement system. Results showed that the time-dependent behavior of FWA agrees to that of a mono-molecular adsorption layer on fiber surfaces,as characterized in Langmuir-type expression. The adsorption has two distinguishable stages includ-ing initial fast phase with the primary constant of 1.51×1014 and the later near-equilibrium phase with the secondary constant of 4.96×10-4. The maximum amount of FWA adsorbed on fiber surfaces is 1.67×10-4g (per dry weight based fiber) in the initial phase. A mathematical model of adsorption kinetics was therefore established and evaluated. This model is important for the optimization of FWA applica-tion in papermaking.