Polyhydroxyalkanoates (PHA) are polyesters of various hydroxyalkanoates accumulated in numerous bacteria. All of the monomeric units of PHA are enantiomerically pure and in R-configuration. R-Hydroxyalkanoic acids can be widely used as chiral starting materials in fine chemical, pharmaceutical and medical industries. In this study, we established an efficient method for the production of chiral hydroxyalkanoic acid monomers from PHA. Pseudomonas putida cells containing PHA were resuspended in phosphate buffer at different pH. We observed that the optimal initial pH for intracellular PHA degradation and monomer release was at pH 8-11 with pH 11 as the best. At initial pH 11, PHA containing 3-hydroxyoctanoic acid and 3-hydroxyhexanoic acid was degraded with an efficiency of over 90% (w/w) in 9 h, and the yield of the corresponding monomers was also over 90%. Under the same conditions, unsaturated monomers were also effectively produced from PHA containing 3-hydroxy-6-heptenoic acid, 3-hydroxy-8-nonenoic acid, and 3-hydroxy-10-undecenoic acid. The monomers (e.g., 3-hydroxyoctanoic acid) were further isolated using solid phase extraction and purified on reversed phase semipreparative liquid chromatography. We confirmed that the purified 3-hydroxyoctanoic acid monomer has exclusively the R-configuration.

Triglycerides, together with nine synthetic phenolic antioxidants most commonly used to prevent oxidation of edible oils and fats, as well as the natural antioxidants tocopherols and a-tocopherol acetate, were separated by high performance liquid chromatography by means of a reversed phase Cls-column and gradient elution with water/acetonitrile/methanol/isopropanol. Besides dilution of the oil with isopropanol/hexane, no further example preparation was required. UV detection was applied. The synthetic antioxidants propyldodecylgallate, octyldodecylgallate, dodecylgallate, 3-tert-butyl-4-hydroxyanisol, tert-butylhydroquinone, 3,5-di.tert.butyl-4-hydroxytoluene, 2,6.di-tert-butyl-4.hydroxymethylphenol, 2,4,5-trihydroxybutyrophenone and nordihydroquaiaretic acid, as well as a-and 6-tocopherol and atocopherol acetate were base-line separated; f~ and ytocopherol, however, eluted together. The triglycerides, detected at ~ --215 nm, were separated according to their partition number. The absorption at ~ --215 nm revealed saturated and unsaturated triglycerides. The absorption at ~ --280 nm indicated triglycerides with conjugated unsaturation, relating information about refining and heat treatment of the oil. Oxidized unsaturated triglycerides showed absorption at k = 230 nm. Triglycerides of ricinoleic acid, a hydroxymonounsaturated acid, gave identical UV spectra. The simultaneous detection of antioxidants and triglycerides may be used to study inhibition effects by antioxidants in oils.

In the 1990s the CCQM (Comité consultatif pour la quantité de la matière) defined the term 'primary method'. It also identified some methods that are considered to be primary. One of these methods is titrimetry. In this paper, the principle of titrimetry and two practical examples performed at the highest metrological level in the frame of key comparison CCQM-K8 are discussed. It is evident that titrimetry is a very powerful method leading to highly accurate results when performed correctly, and does not depend on whether the classical metrological approach or a new experimental design using modern laboratory technology is applied.

This report describes a key comparison of monoelemental calibration solutions, organized under the auspices of the Consultative Committee for Amount of Substance (CCQM) in 1999-2000 and piloted by the Federal Laboratories for Materials Testing and Research (EMPA, Switzerland) and the Laboratoire National d'Essais (BNM-LNE, France). Solutions of aluminium, copper, magnesium and iron were measured. Although different methods of measurement were applied, most of the thirteen participating national metrology institutes achieved results within the required target range for a combined standard uncertainty of 0.5 % relative for each element. The methods used were titrimetry, coulometry, gravimetry, isotope dilution mass spectrometry and inductive coupled plasma/emission spectrometry.

E n H . B r i i s c h w e i l e r , Hebne F e l b e r u n d R S c h w a g e r + Eidgenossische Materialpriffirngs-und V2rsuchanstalt, St. GahdSchwekBienenwachs, ein Stoffwechselprodukt der Honigbiene Apis mellifca, ist das dteste von Menschen genutzte Natunvachs. Seine Zusammensetzung ist heute weitgehend bekannt. 70-80 1% des Bienenwachses sind Fettsaureund Hydroxyfettsaureester hoherer Alkohole, 10-15 freie Fettsauren und 10-20'k Kohlenwasserstoffe. Mittels Gaschromatographie konnen ca. 65 des nicht hydrolysierten Wachses erfaDt werden. Die restlichen 35 "/ u stellen im wesentlichen schwer fliichtige Di-und Triester dar. Ein vollstiim diges Bild ergibt die gaschromatographische Analyse einer hydrolysierten und silylierten Wachsprobe, bei der alle Bestandteile bzw. deren Hydrolyseprodukte getrennt werden. Man erhdt fur Bienenwachs charakteristische Chromatogramme, in denen Fremdzusatze leicht erkannt werden konnen. Fat Sci. Technol. 91. Jahrgang Nr. 2 1989 Fat Sci. Technol. 91. Jahrgang Nr. 2 I989 Fat Sci. Technol. --91.Jahrgang Nr. 2 1989 / / Fat Sci. Techno]. 91. Jahrgang Nr. 2 1989

A new measurement concept has been published in the name of seven global scientific and technical organizations. The concept is based exclusively on observable quantities and solely aims at the comparability of results between laboratories. The main tasks of the analyst to obtain results that are comparable with those of other laboratories are to properly validate the analytical procedure and establish adequate calibration or control for each value and each condition defined in the procedure; if necessary, to correct for recognized significant systematic effects; and to evaluate the combined standard uncertainty and report the result as an interval (value and uncertainty). The concept has been adopted by all leading national metrology institutes around the world, for example, by the National Institute for Standards and Technology of the United States. In this article, an example for the implementation of measurement uncertainty in lectures on analytical chemistry is presented. Furthermore, the measurement concept published in the Guide to the Expression of Uncertainty in Measurement (GUM) is compared with the current state-of-practice.

National Metrological Institutes (NMI's) from fifteen different countries participated in interlaboratory comparisons where concentrations of about 1 g kg À1 in solutions of aluminium, copper, iron, magnesium, chloride and phosphate were measured. A very high comparability of the results irrespective of the analyte and the applied measurement technique was observed. The relative in-between laboratory standard deviations of the results as reported by the participating laboratories were between 0.13% for copper and chloride up to 0.33% for aluminium, and all of the 81 results were found in the range of AE1% with respect to the reference value. Due to the gravimetric preparation of the samples, a conventional true reference value was calculated, and no significant deviations of the reference values and the means of all results reported by the institutes were found.

The selective determination of phosphonates in detergents with ion chromatography is disturbed by the presence of Al or other metal ions. Due to the formation of stable metal-phosphonate complexes, phosphonate is linked and thus a determination is not possible. The disturbance caused by AlIII can be eliminated by adding a competing agent to the analyte solution.