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A collaborative study was organised, according to the ISO 5725 protocol, for the evaluation of methods of residue analysis of chloramphenicol on a national basis and as potential reference methods for the European Community. The methods to be examined were RIA and HPLC. Reference samples were prepared with defined contents of chloramphenicol in the order of 1 μg/kg in milk and 10 μg/kg in meat, respectively. The analytical methods used for the determination of the “true” value of chloramphenicol contents were radioimmunoassay (RIA) and gas chromatography with either electron capture detection (GC/ECD) or mass specific detection (GC/MSD). Each concentration level was analysed 16 times by RIA, 5 times by GC/ECD and twice by GC/MSD. An additional object of our studies was the examination of the packed and coded samples for homogeneity. The influence of duration and temperature of storage and the influence of irradiation were investigated.

A new column system for the isothermal analysis of H2, O2, N2, CO, CH4, CO2, C2H4, C2H6 and C2H2 is described. Higher hydrocarbons and water are backflushed from the system. The use of 13X molecular sieve in a relatively deactivated state shortens the elution times of the light components and improves peak shapes. Both factors enable quantitative analyses to be carried out satisfactorily at lower concentrations than would otherwise be possible. Analysis of all compounds listed can be carried out in eleven minutes. Sparingly activated 13X molecular sieve columns have proved to be very stable and rarely require reactivation. The method of column switching employed avoids the use of mechanical valves in the sample path and is suitable for automatic operation.

A fast, simple and robust method for the routine determination of chlormequat (CCC) in pears and pear concentrates is described. The method is based on sample clean-up using an SPE strong cationic exchange (SCX) cartridge followed by analysis on a benchtop liquid chromatograph coupled to an atmospheric pressure electrospray ionisation mass spectrometer (LC-ESI-MS). The instrument is equipped with a weak cationic exchange (WCX) column. For quantification, ionsm/z 122 and 124, representing the chloro isotopes of the molecular ion, are monitored. Recoveries for chlormequat at three levels (50, 100, 250 ppb) from pears are in the range of 81–85%, and from pear concentrates in the range of 90–93%. The dynamic range covers concentrations from 10 to 500 μg kg−1 (ppb) with a correlation coefficient of r=0.999. During validation, the reproducibility (RSD) for the standard solution is found to be 4.3% (n=8; within one day) and 6.0% (n=16, day-to-day), the limit of detection (LOD) is 3 ppb (3 S/N) and the limit of quantitation (LOQ) is 10 ppb. Residue levels in pears purchased from a local supermarket in December 1998 and January 1999 were as high as 8 mg kg−1 (8 ppm). The method can also be applied to the determination of CCC in other fruits and concentrates e.g. apples and grapes.

A humic acid stationary phase is evaluated for studying by capillary electrochromatography (CEC) the binding of four pesticides with humic acid (HA), the main organic component in soil. It was demonstrated that the humic acid capillary was stable in terms of efficiency and retention during a long period of time. It appeared that HA has a lower affinity for neutral than for charged pesticides. The influence of the mobile phase constitution on the pesticide retention was also investigated in order to provide valuable information about the binding mechanism. The results suggest that the interactions of the pesticides during CEC are solely based on chromatographic mechanisms and that electrophoresis only plays a minor role. As well, it was shown that the HA stationary phase was able to separate these pesticides by CEC with a low analysis time. This HA capillary column could soon become attractive to determining the risk assessment of pesticides.

The carotenoids lutein and zeaxanthin have been identified as the macular pigments of the human retina. Nutritional epidemiological reports indicate that high consumption of fruits and vegetables rich in these carotenoids is correlated with reduced risk of some illnesses, e.g. agerelated macular degeneration (AMD). Because carotenoids are extremely sensitive to UV light and oxygen, they occur in nature as several Z/E stereoisomers which can differ considerably in their biological effectiveness. With particular regard to dietary supplementation we have focussed on identification and quantification of all the carotenoid stereoisomers occurring in a variety of raw and processed homegrown and commercial spinach samples, a natural source of carotenoids. Isolation of the unstable carotenoid stereoisomers from biological tissues without sample-preparation artifacts requires a mild, rapid, complete, and reproducible extraction technique such as matrix solid-phase dispersion (MSPD). Separation and unequivocal structural elucidation of the main carotenoid stereoisomers was achieved by use of hyphenated analytical techniques and exclusion of light and oxygen. HPLC analysis with highly selective C30 columns was used for quantitative determination of the main Z/E carotenoid stereoisomers and HPLC-APCI-MS and HPLC-NMR on-line coupling was used for unequivocal structural elucidation. Whereas HPLC-APCI-MS can distinguish between the carotenoids lutein and zeaxanthin, HPLC-NMR enables identification of all the main Z/E stereoisomers.

Liquid chromatography with amperometric detection (LC-AD) is developed and applied to simultaneously determine five aromatic amines. In the LC-AD, a new carbon nanotubes/poly(3-methylthiophene) modified dual-electrode is fabricated and then used as the working electrode. It is found that this chemically modified electrode (CME) exhibits efficiently electrocatalytic oxidation for aromatic amines with relatively high sensitivity, stability and long-life. Thus, lower detection in LC-AD can be achieved, which are 4.0 × 10−8 mol L−1 for aniline, 1.6 ×10−7 mol L−1 for 4-nitroaniline, 1.0 × 10−7 mol L−1 for 4-chloroaniline, 1.5 × 10−7 mol L−1 for 1-naphthylamine, 1.7 × 10−7 mol L−1 for 2-bromoaniline. The recoveries of the five analytes are also determined, which range between 0.95 and 1.05 for drinking water, 0.86 and 1.10 for the LiWa River water.