A simple HPLC-MS method for the quantitative determination of the composition of bacterial medium chain-length polyhydroxyalkanoates

Bacterial poly(hydroxyalkanoates) (PHAs) vary in the composition of their monomeric units. Besides saturated side-chains, unsaturated ones can also be found. The latter leads to unwanted by-products (THF ester, secondary alcohols) during acidic cleavage of the polymer backbone in the conventional analytical assays. To prevent these problems, we developed a new method for the reductive depolymerization of medium chain-length PHAs, leading to monomeric diols that can be separated and quantified by HPLC/MS. Reduction is performed at room temperature with lithium aluminum hydride within 5-15 min. The new method is faster and simpler than the previous ones and is quantitative. The results are consistent with the ones obtained by quantitative (1)H NMR.     

The application of elemental analysis to the determination of the composition of a mixture of pyridine compounds

The composition of a gross mixture of pyridine compounds was determined rapidly and inexpensively by the use of standard microanalytical techniques. Spectral data corroborated the elemental results.     

The precession technique in electron diffraction and its application to structure determination of nano-size precipitates in alloys.

Crystal structure of nano-scale precipitates in age-hardening aluminum alloys is a challenge to crystallography. The utility of selected area electron diffraction intensities from embedded precipitates is limited by double scattering via matrix reflections. This effect can be signally reduced by the precession technique, which we have used to collect extensive intensity data from the semicoherent, metastable eta-precipitate in the Al-Zn-Mg alloy system. A structure model in the space group P-62c is proposed from high-resolution microscopy and electron diffraction intensities. The advantages of using the precession technique for quantitative electron diffraction is discussed.     

A simple HPLC-DAD method for determination of adapalene in topical gel formulation

A simple stability indicating high-performance liquid chromatography method for the analysis of adapalene in pharmaceutical gel formulation is developed and validated. An isocratic separation is performed using a Merck RP-8 (150 mm × 4.6 mm i.d., particle size 5 m) column and a mixture of acetonitrile water (67:33, v/v, pH adjusted to 2.5 with phosphoric acid) as the mobile phase. The detection is achieved with a photodiode array detector at 321 nm. The specificity of the method is verified by subjecting both the reference substance and the pharmaceutical form to hydrolytic, oxidative, photolytic, and thermal stress conditions. There is no interference from the excipients of the formulation on the determination of adapalene in gel. The response is linear over the concentration range of 8.0-16.0 μg/mL (r > 0.999) with a limit of detection and quantification of 0.04 and 0.14 μg/mL, respectively. The mean recovery is 100.8%. The RSD values for the intra- and inter-day precision studies are < 1.2%. The method is validated by reaching satisfactory results for linearity, selectivity, specificity, precision, accuracy, robustness, and system suitability.     

Identification and quantitative determination of diphenylarsenic compounds in abandoned toxic smoke canisters

Knowledge of the exact nature of the constituents of abandoned chemical weapons (ACW) is a prerequisite for their orderly destruction. Here we report the development of analytical procedures to identify diphenylchloroarsine (DA/Clark I), diphenylcyanoarsine (DC/Clark II) and related substances employed in one of the munitions known as "Red canister". Both DA and DC are relatively unstable under conventional analytical procedures without thiol derivatization. Unfortunately however, thiol drivatization affords the same volatile organo-arsenic derivative from several different diphenylarsenic compounds, making it impossible to identify and quantify the original compounds. Further, diminishing the analytical interference caused by the celluloid powder used as a stacking material in the weapons, is also essential for accurate analysis. In this study, extraction and instrumental conditions have been evaluated and an optimal protocol was determined. The analysis of Red canister samples following this protocol showed that most of the DA and DC associated with pumice had degraded to bis(diphenylarsine)oxide (BDPAO), while those associated with celluloid were dominantly degraded to diphenylarsinic acid (DPAA).     

Fluorometric method for quantitative determination of glucose and its application to human serum.

By coupling the Fenton reaction with the glucose oxidase (GOD)-catalyzed reaction, we have developed a fluorometric method for the determination of glucose; the linear response range and the detection limit are 0.108-2.59 microg/ml and 0.0432 microg/ml, respectively. This approach is selective and has the advantages of using inexpensive reagents and avoiding interferences. Satisfactory results were obtained for the determination of glucose in human serum samples.     

A simple clean-up procedure for the quantitative determination of PCBs in complex materials

Summary A simple, rapid, low cost and uniform single-step clean-up procedure with a column containing two silica gel packings of different mesh size for the quantitative determination of PCBs by capillary gas chromatography (ECD) is reported. Its application to 9 complex matrices, among them a transformer oil, a waste motor oil, and an oil from a tempering bath, shows that in contradiction to other clean-Up methods nearly all accompanying substances can be separated. The reproducibility of 4.7% and the recovery rate of 92.7% for the PCBs are comparable with data found in literature.

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Einfaches Clean-up-Verfahren zur quantitativen Bestimmung von PCBs in komplexen Materialien

     

饮料及糖果中亮蓝、苋菜红及柠檬黄的简便定量分析EI北大核心CSCD

采用定性与定量相结合,建立了测定饮料及糖果中共存色素亮蓝(BRIB)、苋菜红(AMA)及柠檬黄(TAR)的简便吸收光谱法。BRIB,AMA及TAR在pH 3.50 Tris-HCl条件下,分别与乙基绿反应生成离子缔合物,产生新的特征吸收光谱。定量测定波长分别为588 nm(BRIB体系)、532 nm(AMA体系)和426 nm(TAR体系),表观摩尔吸光系数(κ)分别为4.24×10^(4)L/(mol·cm)(BRIB体系)、3.35×10^(4)L/(mol·cm)(AMA体系)和2.64×10^(4)L/(mol·cm)(TAR体系),线性范围分别为0.05~18.8 mg/L(BRIB体系)、0.05~13.3 mg/L(AMA体系)和0.05~11.7 mg/L(TAR体系),检出限分别为35μg/L(BRIB体系)、27μg/L(AMA体系)和30μg/L(TAR体系),定量限分别为0.61 mg/kg(BRIB体系)、0.47 mg/kg(AMA体系)和0.52 mg/kg(TAR体系)。该方法用于市售饮料及糖果中共存BRIB,AMA及TAR的测定,加标回收率为97.8%~103%(BRIB体系)、97.9%~102%(AMA体系)和98.1%~103%(TAR体系),相对标准偏差分别为2.0%~2.8%(BRIB体系),1.2%~2.6%(AMA体系)和1.6%~2.6%(TAR体系)。     

Quality control in combinatorial chemistry: determination of the quantity,purity, and quantitative purity of compounds in combinatorial libraries

The quality of combinatorial libraries determines the success of biological screening in drug discovery programs. In this paper, we evaluate and compare various methods for measuring identity, purity, and quantity (yield) of combinatorial libraries. Determination of quantitative purity reveals the true library quality and often indicates potential quality problems before full-scale library production. The relative purity can be determined for every member in a large library in a high-throughput mode, but must be cautiously interpreted. In particular, many impurities are not observable by relative purity measurements using detectors such as UV(214), UV(254), and evaporative light-scattering detection. These "invisible" impurities may constitute a significant portion of the sample weight. We found that TFA, plastic extracts, inorganic compounds, and resin washout are among these impurities. With compelling evidence, we reach a conclusion that purification is the only way to remove "invisible" impurities and improve the quantitative purity of any compound even though some compounds may have a high relative purity before purification.     

用手性高效液相色谱法拆分并测定氯苄哌醚联苯酰苯甲酸盐(英文)

氯苄哌醚联苯酰苯酸盐主要用于止咳,L-氯苄哌醚联苯酰苯酸盐具有更高活性.采用手性色谱柱,建立了氯苄哌醚联苯酰苯酸盐光学异构体的拆分方法,并将其用于氯苄哌醚联苯酰苯酸盐的检测.结果表明,采用Chiralcel OD-H柱,在流动相V(正己烷)∶V(异丙醇)∶V(二乙胺)=98∶2∶0.1的条件下,2个异构体能同时达到基线分离,检测波长为254nm,氯苄哌醚联苯酰苯酸盐检测极限为10ng.这表明所建立的分离分析方法可方便可靠地用于该化合物的光学纯度检测.     

Identification and quantitative determination of some inorganic lanthanide compounds by diffuse reflectance spectroscopy

Diffuse reflectance spectroscopy in the UV, visible, and near-IR regions is found to allow the detection and identification of lanthanide oxides, fluorides, sulfides, and sulfofluorides without decomposing and dissolving samples. A nondestructive method for the detection and quantitative determination of more than 1 wt % of Eu(II) in the corresponding fluorides is proposed.     

The application of chromatographic visualization test to determination of hydrophobic properties of aliphatic compounds

The experimental material obtained shows the possibility of using new fuchsine to compare the hydrophobic properties of aliphatic compounds. The test presented here seems to be of analytical importance, especially with chromatographic investigations and when selecting proper extracting systems.     

Modified HS-SPME for determination of quantitative relations between low-molecular oxygen compounds in various matrices

Similar quantitative relations between individual constituents of the liquid sample established by its direct injection can be obtained applying Polydimethylsiloxane (PDMS) fiber in the headspace solid phase microextraction (HS-SPME) system containing the examined sample suspended in methyl silica oil. This paper proves that the analogous system composed of sample suspension/emulsion in polyethylene glycol (PEG) and Carbowax fiber allows to get similar quantitative relations between components of the mixture as those established by its direct analysis, but only for polar constituents. It is demonstrated for essential oil (EO) components of savory, sage, mint and thyme, and of artificial liquid mixture of polar constituents. The observed differences in quantitative relations between polar constituents estimated by both applied procedures are insignificant (F_exp < F_crit). The presented results indicates that wider applicability of the system composed of a sample suspended in the oil of the same physicochemical character as that of used SPME fiber coating strongly depends on the character of interactions between analytes-suspending liquid and analytes-fiber coating.     

Preparation of dendrimer-like polyamidoamine immobilized silica gel and its application to online preconcentration and separation palladium prior to FAAS determination

A amino-terminated G 4.0 dendrimer-like polyamidoamine (PAMAM) immobilized silica gel (PAMAMSG) was prepared with a divergent method by repeating two processes: (1) Michael addition of methyl acrylate (MA) to surface amino groups; and (2) amidation of the resulting esters with ethylenediamine (EDA) from γ-aiminopropyl silica gel (APSG) core. It was then used for the first time as microcolumn packing for the flame atomic absorption spectrometry (FAAS) determination of trace or ultra trace Pd(II), after flow injection (FI) online preconcentration and separation process. A limit of detection (LOD) of 3.9 ng ml⁻¹ was achieved when 0.200 μg ml⁻¹ Pd(II) was preconcentrated in 0.2 mol l⁻¹ HCl medium with a sampling flow rate of 6.0 ml min⁻¹ for 60 s and the relative standard deviation (R.S.D.) was 1.7%. The proposed method was successfully used for the determination of Pd in two metallurgical samples.