New detection modes for the determination of cephalosporins and their decomposition products

Summary The feasibility of using fluorescence and electrochemical detection after high performance liquid chromatography separation is investigated for a sensitive and selective determination of cephalosporins and their decomposition products. The sensitivity and detectability of fluorescence and electrochemical detection are compared to those of UV absorption detection. The methods have been validated for the determination of cephalosporins in biological fluids and for stability studiesin vitro.     

Determination of Penicillins and Cephalosporins N-Pyrrolylderivatives by HPLC

Abstract

An isocratic reversed-phase liquid chromatographic method for the determination of different types of penicillins and cephalosporins N-pyrrolylderivatives using UV detection at 254 nm is described. The mobile phases were aqueous methanolic (40–60%, v/v), 0.05M potassium phosphate buffer, pH 6.0.

The method is sufficiently sensitive and precise and is thus highly suited for use in the kinetic studies.     

An Isocratic HPLC Method for the Determination of Cephalosporins in Plasma

Abstract

An isocratic reversed-phase liquid chromatographic method for the determination of eight cephalosporins in human plasma using UV detection at 254 nm is described. Plasma proteins were precipitated using acetonitrile prior to injection of a 10 μl aliquot onto an octadecylsilane column. The mobile phases consisted of 6–11% acetonitrile in sodium dihydrogen phosphate (0.01M). The minimum detectable limit for each drug was less than 1 γg/ml of plasma. Possible interference from other drugs which might be administered concurrently is discussed. The reproducibility and precision of the method for cephalosporin assay are shown from the analysis of plasma containing 5–500 γg/ml of plasma. The chromatographic behavior of the eight cephalosporins was examined by varying mobile phase conditions.     

The High Performance Liquid Chromatography and Detection of Phospholipids and Triglycerides. III. Response of the Differential Refractive Index and Ultraviolet Absorption Detector

Abstract

A liquid chromatographic differential refractive index detector (RI) and an ultraviolet absorption (at 195 nm) detector (UV) were studied for detection of triglyceride (TG) and phospholipid (PL) molecular species. It was found that the log UV/RI detector response ratio was linearly related to the log of the number of conjugated double bonds (degree of unsaturation) of the lipid in a predictable fashion, indicating the usefulness of the combination of both detectors in TG and PL analysis. The detection limit of the RI detector for TG and PL was found to be 5 × 10 ^?7 M or as sensitive as the UV detector for saturated TG and PL.     

β-Naphthol as a Chromophore and Fluorophore Forming Reagent in the HPLC Determination of Alkyl Halides

Abstract

A suitable chromophore- and fluorophore- forming reagent for the detection of alkyl halide water contaminants is β-naphtol. The ether derivatives are separated from each other and excess β-naphthol reagent by reverse, phase HPLC and are detected by ultraviolet absorption or fluorescence. A method for the determination of alkyl halides is presented. The method is applicable to concentration levels in the ppm range for UV detection and in the ppb concentration range using fluorescence detection.     

A Comment on the Use of Colorimetric Determinations of Phenolic Compounds in Surface Water

Abstract

Total phenolic compound values were determined in samples of river water by means of the Folin-Ciocalteu colorimetric method, while HPLC with UV detection was used to identify individual phenols. Preconcentration was needed in all cases to meet the required detection limits. Given the absorption coefficients of the components, the error incurred when a curve calibrated against phenol only is used to evaluate a mixture was calculated.     

Electrochemical Detection of Retinoids Using Normal Phase HPLC

Abstract

Non-aqueous electrochemical (EC) detection of 13-cis-retinoic acid, all-trans retinoic, acitretin and vitamin A palmitate in non-aqueous solvents are reported.

Non-aqueous (EC) detection allows for normal-phase chromato-graphy of these compounds prior to detection. The normal phase system used a mobile phase of HEX/THF/AcOH for the separation of all four compounds. The stationary phase was either silica or PVA-sil. The lipophilic salts, t-butylammoniumtetrafluoroborate or t-butyl-ammoniumhexafluorophosphate necessary for EC detection were added post-column.

The limit of detection (LOD) for EC detection of these compounds is approximately 1 ng on column compared with an LOD by UV absorption of 2 ng on column.

The linear detection for these compounds with the EC detector was about two orders of magnitude.     

High-Performance Liquid Chromatography of Domoic Acid,a Marine Neurotoxin,with Application to Shellfish and Plankton

Abstract

A recent outbreak of poisoning resulting from the consumption of cultured blue mussels (Mytilus edulis L.) from a localized area in Eastern Canada has been attributed to the presence of domoic acid (1), a relatively rare neurotoxic amino acid, previously found only in some algae of the family Rhodomelaceae. Studies on aqueous extracts of shellfish tissue indicated that the toxin and several of its isomers could be separated (and isolated in sufficient amounts for subsequent structural identification) by reversed-phase high-performance liquid chromatography (HPLC) with ultraviolet (UV) diode array detection (DAD). Aqueous acetonitrile containing 0.1% v/v trifluoroacetic acid was used as mobile phase. As the retention time and characteristic UV absorption spectrum of 1 (λ_max = 242 nm) permit unequivocal identification, the HPLC-DAD procedure was refined with a microbore column to provide a rapid (5 min), sensitive (0.3 ng detection limit) and reproducible assay method for the determination of 1 in shellfish tissue. Extraction was accomplished by boiling homogenized shellfish tissue for 5 min with distilled water. Extracts were taken through an octadecylsilica solid phase extraction clean-up prior to HPLC. This method has been applied to a variety of shellfish and phytoplankton samples.

BRIEF

Reversed-phase HPLC with ultraviolet diode array detection was used to analyze shellfish tissue and phytoplankton extracts for domoic acid. A rapid (5 min) and sensitive (0.3 ng detection limit) assay is presented.     

Indirect ultraviolet detection of alkaline earth metal ions using an imidazolium ionic liquid as an ultraviolet absorption reagent in ion chromatography

A convenient and versatile method was developed for the separation and detection of alkaline earth metal ions by ion chromatography with indirect UV detection. The chromatographic separation of Mg²⁺, Ca²⁺, and Sr²⁺ was performed on a carboxylic acid base cation exchange column using imidazolium ionic liquid/acid as the mobile phase, in which the imidazolium ionic liquid acted as an UV‐absorption reagent. The effects of imidazolium ionic liquids, detection wavelength, acids in the mobile phase, and column temperature on the retention of Mg²⁺, Ca²⁺, and Sr²⁺ were investigated. The main factors influencing the separation and detection were the background UV absorption reagent and the concentration of hydrogen ion in ion chromatography with indirect UV detection. The successful separation and detection of Mg²⁺, Ca²⁺, and Sr²⁺ within 14 min were achieved using the selected chromatographic conditions, and the detection limits (S /N = 3) were 0.06, 0.12, and 0.23 mg/L, respectively. A new separation and detection method of alkaline earth metal ions by ion chromatography with indirect UV detection was developed, and the application range of ionic liquids was expanded.     

Determination of Aztreonam by liquid Chromatography with UV and Amperometric Detection

Abstract

A comparative study of UV and amperometric detection of aztreonam after HPLC separation is presented. At pH 2.0 and a detection potential of +1.15 V (vs. Ag/AgCl), the detection limits with amperometric detection are about two times higher (3–5 ng) than those obtained with UV detection (1–3 ng) for aztreonam and its main decomposition products, the E-isomer and open-ring aztreonam. With the advantage of specificity for the aminothiazole group of the aztreonam molecule, amperometry can be used as an alternative or complementary mode to UV detection for the determination of aztreonam in injectable formulations and in human serum.     

A biacylhydrazone-based chemosensor for fluorescence ‘turn-on’ detection of Al3+ with high selectivity and sensitivity

A simple Al³⁺ fluorescent chemosensor (1) based on diacylhydrazone has been designed and synthesized by the condensation reaction of 2-hydroxy naphthaldehyde and metaphthalic hydrazide. The chemosensor 1 displays a specific and sensitive response to Al³⁺ over other cations in DMSO solution. Upon the addition of DMSO solution of Al³⁺, the sensor 1 shows an immediate fluorescence ‘turn-on’ response and emitting strong blue emission with visible color change from colorless to green. The fluorescence quantum yield enhanced from 7.24% to 48.68%. Meanwhile, the fluorescence and UV absorption spectra detection limits of the chemosensor 1 for Al³⁺ were 2.0 × 10^?7 M and 5.6 × 10^?7 M respectively, indicating the high sensitivity of 1 to Al³⁺. Furthermore, test strips based on 1 were fabricated, which could be used as a convenient test kit for the detection of Al³⁺ and an efficient Al³⁺ controlled fluorescent security display materials.     

几种多氮杂环高能化合物的光电子能谱与紫外吸收光谱

多氮杂环化合物由于含氮量高, 具有很高的生成焓, 而且分解产物一般不会对环境造成污染, 因此这类化合物用于环境友好的炸药和推进燃料的前景十分诱人, 成为当前高能量材料的研究热点之一. 利用紫外光电子能谱实验手段和量子化学计算研究了四种多氮杂环化合物[1H-tetrazole (1), 5-aminotetrazole (2), 1,5-diaminotetrazole (3), 1,4-bis(1-methyltetrazol-5-yl)-1,4-dimethyl-2-tetrazene (4)]的电子结构, 提供了这些化合物的电离能: 实验结果表明四个化合物的第一电离能分别为: 11.22, 9.40, 9.27, 9.18 eV; 同时报道了这四个化合物在乙氰溶液中的紫外吸收光谱: 化合物 1～3 均只有一个紫外吸收峰带, 分别为193, 216, 218 nm, 化合物 4 在230和298 nm出现了两个吸收带.     

HPLC Method Development for a New Antiarrhythmic Drug

Abstract

The present report concerns HPLC method development for chemical samples of a new antiarrhythmic drug 2-methyl-5-phenyl-5-[2-[2-N, N-bis (1-methylethyl amino] ethyl]-1,3 diazabicyclo [4.4.0] octen-4-one (MPMED). Selectivity optimization for MPMED and several synthetic process intermediates with reversed-phase HPLC conditions is described. Also, the use of electrochemical and UV absorption detection for MPMED samples has been evaluated. The developed method has been validated for generation of assay data for chemical lots of MPMED.     

Atomic Absorption Spectrophotometry as a Chromatography Detector for Copper-Amino Acid Complexes in Human Serum

Abstract

In this paper an automatic sampling device is used for the electrothermal atomic absorption detection of copper-amino acid complexes in human serum after separation on an ion exchange chromatographic column. Adsorption chromatography on a silica gel column is used to separate the major naturally occurring copper amino-acids, copper-histidine and copper-glutamine, with subsequent detection by electrothermal atomic absorption.     

β-Blocking Agents: Determination of Biological Levels Using High Performance Liquid Chromatography

Abstract

Nine β-blocking agents have been tested and dosed by high performance liquid chromatography. Six of them, acebutolol an acebutolol metabolite, atenolol, metoprolol, propranolol and sotalol are detected with a fluorometric detector. Oxprenolol, pindolol and timolol can be quantified by their UV absorption at variable wavelength. A method is developped to find the best conditions of extraction and detection for each blocking agent. Experimental trials have led to a simple procedure for all compounds. Only pindolol and timolol plasma levels are non suitable for high performance liquid chromatography and need mass fragmentography or gas chromatography with electron capture detection.

However, pharmacokinetic parameters can be reached, for timolol and pindolol, through urinary excretion since sensitivity of the procedure is within the range of urinary levels.

The method has been applied, as well, to pharmacokinetic studies on sotalol, acebutolol, acebutolol metabolite, atenolol, propranolol, pindolol and timolol.     

Quantitative Estimation of Urinary Metabolites in Ruminants by High-Performance Liquid Chromatography

Abstract

A reversed-phase high-performance liquid chromatographyc method for a simultaneous determination of cretinine (C); Uric Acid (A); Hipoxanthine (HX); Xanthine (X); Hippuric Acid (HA); Benzoic Acid (BA) and Phenylacetic Acid (PAA) in urine of ruminants is described.

Separation was achieved on a Nova-PaK column by-gradient elution. Quantitation and detection limits were determined Detection is effected by UV absorption at 254 nm with a total analysis time of less than 30 min. An aliquot of diluted urine is injected directly into the liquid chromatographic column.

The proposed HPLC method was verified for linearity, accuracy, precision and applicability.     

Zn(II)-containing metallo-supramolecular polymers: synthesis,photophysical and electrochemical properties

Abstract

Two novel building blocks M1, M2 with different electronic structures, were synthesized based on 2,2′:6′,2″-terpyridine modified with cyano-p-phenylenevinylene (CN-PV) and carbazole moieties through Knoevenagel condensation and Suzuki coupling, respectively. Directed by transition metal ion Zn²⁺, the metallo-homopolymers P1, P2 and metallo-copolymer P3 were obtained via self-assembly polymerization. The structures of the monomers and metallo-supramolecular polymers were fully characterized by MS, ¹H-NMR and ¹³C-NMR. Meanwhile, the UV–vis absorption, photoluminescence (PL) and electrochemical properties of these compounds were systematically investigated. With respect to that of the monomers, both the UV–vis absorption and PL spectra of the polymers are significantly red-shifted. The resulting metallo-supramolecular polymers show similar double absorption peaks (342, 418?nm for P1, 339, 410?nm for P2, and 332, 412?nm for P3), which is caused by the π–π* transition and intramolecular charge transfer (ICT). Further, all the polymers display red-orange emission in toluene and narrow electrochemical energy gaps of 1.46, 1.65 and 1.48?eV for P1, P2, and P3, respectively.     

A New Method for the HPLC Analysis of Pt(II) in Urine

Abstract

An analytical method has been developed to measure Pt(II) in urine via derivatization and UV or HPLC analysis. A measured quantity of urine is heated briefly with diethyl ammonium diethyl-dithiocarbamate, and the resulting Pt(Et₂NCS₂)₂ is extracted into a measured volume of chloroform. Concentrations of Pt(II) are determined by UV absorption at 346 nm or by reverse phase HPLC analysis. The detection limit for Pt(II) as its dithiocarbamate is ～ 1 ng by HPLC; the concentration limit for HPLC analysis by direct extraction was ～ 25 ng/ml. Chromatographic response was linearly related to Pt(II) concentration over the range 100-4, 000 ng/ml; dilution of more concentrated samples has extended this range to at least 30, 000 ng/ml. This method has been applied to the analysis of Pt(II) in the urine of patients who have received cis-dichlorodiamniineplatinum(II) (CDDP) chemotherapy.     

HPLC‐UV Detection for Analysis of p‐Benzoquinone Dioxime and p‐Nitrosophenol,and Chromatographic Fingerprint Applied in Quality Control of Industrial p‐Benzoquinone Dioxime

Abstract

A reliable reversed‐phase high performance liquid chromatographic (HPLC) method has been developed for simultaneous determination of p‐benzoquinone dioxime (BQD) and its related impurity p‐nitrosophenol (NSP). Separation was achieved on a Kromasil C₁₈ column by using methanol‐water‐NH₄Ac‐NH₃ solution (pH=7.0, 50 mM) (30/50/20, v/v/v) as the mobile phase, and detection was operated by UV absorption at a wavelength of 305 nm. The method was seen to have good linearity, accuracy, and precision for the concentration range and to be an attractive choice for the quality control of BQD for industrial use. Moreover, the HPLC‐UV‐vis fingerprint of BQD has been established, and successfully applied to quality control of industrial BQD in laboratories of some rubber factories in China. Chromatographic fingerprints of intermediates would become an effective strategy for accelerating the progress of fine chemical industry.     

Potencies of ligand-exchange capillary electrophoresis in the determination of biologically active compounds

The analytical potencies of ligand-exchange capillary electrophoresis (LECE) in regard to the determination of bioactive substances are discussed. As it is shown, complexation with copper(II) in the electrophoretic determination with UV detection makes possible the determination of amino acids, amines, and sugars, which do not absorb in the UV region, with the limits of detection 5–10 mg/L, and reduce the detection limits of the absorbing analytes, such as tryptophane, tyrosine, and histamine by 2–3 times. Prospects for using online preconcentration for the reduction of c _min are shown on an example of aliphatic amino acids, i.e., thirtyfold preconcentration is attained. LECE is shown to be applicable to the simultaneous determination of glucose, Na(⁺), and K(⁺) in human blood serum. Also versions of ligand-exchange capillary electrophoresis with direct UV detection and capillary zone electrophoresis with indirect one are compared in terms of efficiency, time of analysis, and limit of detection. The potencies of the LECE method are compared with those of ligand-exchange chromatography.