Application and new possibilities of automation in liquid chromatography

Summary The different steps of automation of an HPLC system are discussed. With automatic sample injection, a higher through put and a better reproducibility can be achieved than with manual injection.Peak processing systems are necessary to manage the flood of data. Post run optimization of the integration parameters are possible with a computer system. Data systems provide an enormous flexibility to produce different kinds of reports, summaries and graphs and to perform statistical calculations.The assay and purity control of a peptide hormone injection (Lys⁸-Vasopressin) is shown as an example of automated HPLC. Reversed phase gradient elution with UV and reaction detection is used.     

Application of flowing-stream techniques to water analysis Part II. General quality parameters and anionic compounds: halogenated, sulphur and metalloid species

In the first part of this review [Talanta 60 (2000) 867], flowing-stream methods (namely, segmented flow analysis (SFA), continuous-flow analysis (CFA), flow-injection analysis (FIA), sequential-injection analysis (SIA), multicommuted flow-injection analysis (MCFIA) and multisyringe flow-injection analysis (MSFIA)) were presented as powerful analytical tools for nutrient determination in water samples when coupled to photometric/fluorimetric detection, flow-through ion-selective electrodes or amperometric sensors.In the present paper, relevant flow methods applied to the monitoring of anionic species as well as to the determination of general parameters for water quality evaluation (such as pH, alkalinity, chemical and biochemical oxygen demand, conductivity and total ionic content) are reviewed, and their background, detection technique and noteworthy analytical features are detailed. Furthermore, other techniques, such as flow systems connected to hydride-generation atomic absorption spectrometry, should be highlighted as practical approaches for metalloid determination since a series of speciation schemes are demonstrated to be readily adaptable.     

XPS study on early stages of heat deterioratin of silicon-containing aromatic polymide film

Early stages of heat deterioration of some siliconcontaining aromatic polyimide thin films with disiloxane groups (I) in their main chains were studied with XPS. It was found that the thermal decomposition of silicon-containing aromatic polyimides takes place at lower temperatures than those not modified with silicon. The low thermal stabilities observed are explained by the easier decomposition of silicon–carbon bonds (e.g. silicon–methylene, silicon–aryl) than other bonds (e.g. carbon–carbon, carbon–oxygen). Particularly, silicon–methylene bonds (II) readily undergo thermal oxidative decomposition and start to decompose at 350°C under aerobic conditions. This starting temperature of thermal decomposition is lower by 100°C than that of the corresponding polyimide not modified with silicon. In the case of polyimide incorporating silicon–aryl bonds (III) instead of silicon–methylene bonds, the decrease in the thermal decomposition temperature is as small as 50°C, and decomposition under aerobic conditions starts at 400°C.      

Revision of ISO guide 25

 ISO/IEC guide 25 is the internationally recognised base document for the accreditation of laboratories. Laboratory accreditation is a system of peer assessment and a formal recognition that a laboratory is competent to perform specific tests or types of tests ISO/IEC guide 25 plays a fundamental role in the life of the analytical chemist and is pivotal to the acceptance of the philosophy "once tested everywhere accepted" and to ensuring the mutual acceptance of test data. Within the EU, the attainment of accreditation to ISO/IEC guide 25 has become a way of life and it is now mandatory for laboratories engaged in certain regulatory work areas. Guide 25 is currently under revision and over the past 2 years or so it has been the subject of much debate among the calibration and testing community and it has engendered a considerable amount of written and oral comments. The latest revision entitled "Draft International Standard ISO/IEC DIS 17025: General Requirements for the Competence of Testing and Calibration Laboratories" was circulated to national standard organisations for their "comment and approval" in mid 1998. Voting on this document commenced on 9 July and terminates on 9 December 1998. It is anticipated that a final draft could be circulated in 1999. In accordance with the Vienna agreement this is a parallel ISO/CEN enquiry. This paper will discuss the implications of the technical requirements of the current document for analytical chemistry with particular emphasis on, the strengths, weaknesses and deficits inherent in the draft circulated in July 1998.     

Enantioseparation and quality control of biperiden in pharmaceutical formulations by capillary electrophoresis

An original capillary electrophoretic method has been developed and applied for the enantioselective analysis of the antiparkinson drug biperiden in pharmaceutical formulations, using a modified cyclodextrin as the chiral selector. Baseline enantioseparation of the racemic compound was achieved in less than 7 min using an uncoated fused silica capillary (50 μm i.d. and 48.5, 40.0 cm, total and effective length, respectively), filled with a background electrolyte consisting of a 50 mM phosphate buffer at pH 3.5 supplemented with 3% (w/v) β-cyclodextrin sulphate and applying a voltage of 20 kV, reversed polarity. Samples were injected by pressure (50 mbar, 90 s) at the cathodic end of the capillary and detection wavelength was 195 nm (bandwidth: 10 nm). A simple and fast pre-treatment procedure allowed the complete extraction of the drug from commercial formulations (sustained release tablets and ampoules for injections) without any interference from the matrix. Good linearity was found in the 1–50 μg/mL concentration range; the limit of quantitation was 1 μg/mL and the limit of detection was 0.4 μg/mL. Precision and accuracy were good, with R.S.D. values always lower than 2.8% and a mean recovery value of 101.1%. The method was suitable for the quality control of biperiden in commercial formulations.     

The Swiss External Quality Assessment Scheme in Bacteriology and Mycology 1992–1996

 The Swiss External Quality Assessment Scheme in Bacteriology and Mycology was created in 1980 and has been organised since 1983 by the Department of Medical Microbiology in Zurich. The number of Swiss participants has steadily risen from 66 in 1989 to 92 in 1996. Twelve bacterial and fungal strains are sent to the participants in four despatches, each containing three specimens, per year. Scores are allocated per specimen and range between 0 and 1. Participants with mean scores of ≤0.75 are considered poor performers. The mean scores increased from 0.85 in 1992 to 0.91 in 1996. This improvement can be attributed to the educational effect of the external quality control scheme, since all participants receive a detailed discussion for each specimen together with their individual results. On average, both large University and Cantonal (state) laboratories as well as private laboratories show satisfactory performance. In particular, laboratories officially recognised by the Swiss Federal Office of Public Health (SFOPH) rate better than non-recognised participants. Many small regional hospital laboratories, most of them not SFOPH-recognised, are often among the poor performers. They are often managed by technical staff and lack a trained microbiologist. The recently introduced legislation in Switzerland renders participation in external quality assessment schemes compulsory, and all clinical microbiology laboratories are required to employ qualified microbiologists. This will certainly help to improve the quality standards of all laboratories performing microbiological tests. Received: 13 November 1997 · Accepted: 28 December 1997     

Analysis and interpretation of data from real-time PCR trace detection methods using quantitation of GM soya as a model system

Recent years have seen an increased interest in DNA trace detection methods involved in many areas of bioanalytical research, such as quantitation of genetically modified (GM) ingredients in food products. There is little in the way of standardisation of data handling from these methods, and the data generated needs to be analysed appropriately if the results are to be interpreted correctly. This paper describes particular aspects of real-time PCR trace detection methods in order to increase the understanding of data generated using this bioanalytical technique. Using the specific example of GM soya detection and quantitation, it focuses on the production of calibration curves based on the mean and individual data values, the interpretation of correlation coefficients, regression techniques, and discusses suitable data analysis arising from simple and more complex experimental designs following transformation. By using the approaches outlined in this paper, more accurate analysis of data from real-time PCR and GM trace detection methods could be achieved.     

Optimization of the composition and pH of the mobile phase used for separation and determination of a series of quinolone antibacterials regulated by the European Union

Summary To ensure the safety of human food the European Union (EU) has set tolerance levels for quinolone compounds in animal products, so screening and confirmatory analytical methods are required for monitoring of these drugs. In this work, the proportion of organic modifier and the pH of acetonitrile-water mixtures used as mobile phases were optimized for separation of a group of quinolones. Linear solvation energy relationship (LSER) formalism based on the single solvent polarity parameterE _T ^N was used to predict the chromatographic behaviour of the compounds as a function of the amount of acetonitrile in the mobile phase. Correlation between retention and the pH of aqueous-organic mobile phases has also been used to optimize mobile-phase pH. The optimized mobile phase was a linear gradient starting from 18∶82 (v/v) acetonitrileacetate + formate buffer, pH 2.5. Quality data were determined and were satisfactory. The method detection limit was approximately 10 ng mL⁻¹ for most of the quinolones studied. The proposed mobile phase is compatible with mass spectrometric detection of the substances.