Raman spectroscopic studies of the cure of dicyclopentadiene (DCPD)

The cure of polydicyclopentadiene conducted by ring-opening metathesis polymerisation in the presence of a Grubbs catalyst was studied using non-invasive Raman spectroscopy. The spectra of the monomer precursor and polymerised product were fully characterised and all stages of polymerisation monitored. Because of the monomer's high reactivity, the cure process is adaptable to reaction injection moulding and reactive rotational moulding. The viscosity of the dicyclopentadiene undergoes a rapid change at the beginning of the polymerisation process and it is critical that the induction time of the viscosity increase is determined and controlled for successful manufacturing. The results from this work show non-invasive Raman spectroscopic monitoring to be an effective method for monitoring the degree of cure, paving the way for possible implementation of the technique as a method of real-time analysis for control and optimisation during reactive processing. Agreement is shown between Raman measurements and ultrasonic time of flight data acquired during the initial induction period of the curing process.     

Application of atmospheric pressure ionization HPLC-MS-MS for the analysis of natural products

Summary The development of techniques utilizing atmospheric pressure ionization, namely atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI), has pioneered the coupling of liquid chromatography (HPLC) with mass spectrometry in recent years. Both ESI and APCI generate ions from polar and labile biomaterials with remarkable ease and efficiency. In particular, the use of HPLC with tandem mass spectrometry (MS-MS) opens further dimensions in the field of bioorganic analysis. Thus, HPLC-MS-MS provides the tools for direct elucidation of the structure and variety of polar natural compounds in complex matrices. In order to develop efficient and straightforward strategies for the analysis of polar natural products, the potential and the limitations of these hyphenated analytical techniques are discussed using heterocyclic aromatic amines, fumonisins, acylated glycoconjugates and regioisomeric fatty acid hydroperoxides as examples. Presented at the 21^st ISC held in Stuttgart, Germany, 15^th–20^th September, 1996     

Fermentation monitoring using multisensor systems: feasibility study of the electronic tongue

The electronic tongue based on an array of 30 non-specific potentiometric chemical sensors has been applied to qualitative and quantitative monitoring of a batch fermentation process of starting culture for light cheese production. Process control charts were built by using PLS regression and data from fermentations run under normal operating conditions. Control charts allow discrimination of samples from fermentation batches run under abnormal operating conditions from normal ones at as early as 30–50% of fully evolved fermentations. The capability of the electronic tongue to quantify concentrations of important organic acids (citric, lactic and orotic) in the present type of fermentation media was demonstrated. Average prediction errors were assessed in the range 5–13% based on test set validation. Correlation between peptide profiles determined using HPLC and the electronic tongue output was also established. The electronic tongue was demonstrated to be a promising tool for fermentation process monitoring and quantitative analysis of growth media.http://www.electronictongue.com     

Synthesis and structure–property relationships of acrylic core–shell particle-toughened epoxy networks

The use of emulsion polymerization to prepare core–shell rubber (CSR) toughening particles with different shell thickness-to-core diameter ratios is described. The conditions leading to controlled particle size and morphology are discussed. The particle shell is crosslinked during the synthesis so that its integrity and morphology are maintained upon curing of the epoxy network. The mixing of the CSR particles with the reactive epoxy and the processing of toughened-epoxy networks are described. The characteristics of each phase and the mechanical properties of the materials are reported. The fracture parameters (K_lc, G_lc) are discussed in relation to the structure of the CSR-particles.     

排水监测质量保证体系的建立

依据ISO9000质量管理标准和ISO／IEC17025标准，从排水监测管理的目标、技术要求及完善与提高三个方面论述了建立排水监测质量体系的方法和措施，以确保排水监测的各项质量活动能够科学、公正、适时、有效地开展，并对排水监测体系中各要素制定管理方法及控制措施，以不断完善排水监测的管理，提高排水监测质量水平。     

Time-integrated monitoring of polycyclic aromatic hydrocarbons (Pahs) in groundwater using the ceramic dosimeter passive sampling device

Passive sampling relies on the uptake of contaminants into appropriate sampling devices along a diffusion gradient without using pumps or bailers. Thus, for example, in groundwater sampling, changes to flow due to pumping can be avoided. If the diffusion gradient can be maintained for extended periods, contaminants can be sampled continuously over time without any action, allowing to determine time-weighted average contaminant concentrations. We here show that the Ceramic Dosimeter, a solid receiving phase passive sampler using a ceramic membrane as sorbent container and diffusion barrier, can be used without calibration for the long-term monitoring of polycyclic aromatic hydrocarbons (PAHs) in groundwater.     

Liquid chromatography-tandem mass spectrometry for the determination of a new oxazolidinone antibiotic DA-7867 in human plasma

A liquid chromatography-tandem mass spectrometric (LC/MS/MS) method for the determination of a new ox-azolidinone antibiotic DA-7867, (S)-[N-3-(4-(2-(1-methyl-5-tetrazolyl)-pyridine-5-yl)-3- fl uorophenyl)-2-oxo-5-oxazolidinyl]methyl acetamide, in human plasma was developed. DA-7867 and internal standard, linezolid, were extracted from human plasma with ethyl acetate at acidic pH. A reverse-phase LC separation was performed on Luna C(8) column with the mixture of acetonitrile-ammonium formate (10 mm, pH 4.5; 35:65, v/v) as mobile phase. The analytes were determined using an electrospray ionization tandem mass spectrometry in the multiple-reaction-monitoring mode. The lower limits of quanti fi cation for DA-7867 was 2.5 ng/mL. The single liquid-liquid extraction quantitatively recovered DA-7867 and internal standard from plasma samples at the ranges of 82.2-86.7%. DA-7867 was stable in blank human plasma at room temperature for 24 h and following three freeze-thaw cycles.     

Peptide Modified Electrodes as Electrochemical Metal Ion Sensors

Sensors for the detection of metal ions are of considerable importance for enabling the monitoring of environmental samples for metal ion contamination directly in the field. This review outlines the use of peptides and amino acids as the recognition element of electrochemical sensors for metal ion detection. Initially the complexation of metals by peptides is discussed followed by the immobilization of peptides on electrode surfaces. Subsequently, the application of peptide modified electrodes for detecting metals is reviewed and finally challenges and future prospects are outlined.     

Simple, sensitive and rapid liquid chromatographic/electrospray ionization tandem mass spectrometric method for the quantification of lacidipine in human plasma

A simple, sensitive and rapid liquid chromatographic/electrospray ionization tandem mass spectrometric method was developed and validated for the quantification of lacidipine in human plasma using its structural analogue, amlodipine, as internal standard (IS). The method involves a simple single-step liquid-liquid extraction with tert-butyl methyl ether. The analyte was chromatographed on an Xterra MS C(18) reversed-phase chromatographic column by isocratic elution with 20 mM ammonium acetate buffer-acetonitrile (10:90, v/v; pH 6) and analyzed by mass spectrometry in the multiple reaction monitoring mode. The precursor to product ion transitions of m/z 456.4 --> 354.4 and m/z 409.3 --> 238.3 were used to measure the analyte and the I.S., respectively. The chromatographic run time was 1.5 min and the weighted (1/x(2)) calibration curves were linear over the range 0.1-25 ng ml(-1). Lacidipine was sensitive to temperature in addition to light. The method was validated in terms of accuracy, precision, absolute recovery, freeze-thaw stability, bench-top stability and re-injection reproducibility. The limit of detection and lower limit of quantification in human plasma were 50 and 100 pg ml(-1), respectively. The within- and between-batch accuracy and precision were found to be well within acceptable limits (<15%). The analyte was stable after three freeze-thaw cycles (deviation <15%). The average absolute recoveries of lacidipine and amlodipine (IS) from spiked plasma samples were 51.1 +/- 1.3 and 50.3 +/- 4.9%, respectively. The assay method described here could be applied to study the pharmacokinetics of lacidipine.     

Mass spectrometric determination of selected microbial constituents using fused silica and chiral glass capillary gas chromatography

Summary Applications of quantitative gas chromatography/mass spectrometry (selected ion monitoring) to clinical and ecological microbiology are described. The technique permits determination of selected microbial metabolites and can be used for the rapid diagnosis of, for example, tuberculosis by ion-focusing of specific branch-chain fatty acids. The technique is also used to determine diaminopimelic and muramic acids, and D- and L-amino acids separated by chiral gas chromatography, in the low picogram range. The latter method has the potential to detect and quantitate microbial populations.Presented at the 14th International Symposium on Chromatography London, September, 1982