AbstractTwo-step targeted 2D planar chromatographic method (2DTLC) was used in the determination of ginkgolic acids in pharmaceuticals and dietary supplements. The choice of the extraction method and the separation technique was guided by the formulation type (capsule, tablet, tincture) with expected low amounts of ginkgolic acids in the analyzed herbal samples. Separation of ginkgolic acids C15:1 and C17:1 on HPTLC RP18 WF254s was preceded by its separation from the sample matrix on TLC Si60 F254s. Mobile phases consisted of acetonitrile/water/formic acid (80:20:1, V/V/V) and n-heptane/ethyl acetate/formic acid (20:30:1, V/V/V), resp. Identification of separated compounds was based on 2D-TLC co-chromatography with reference substances and off-line 2D-TLC x HPLC-DAD-ESI-MS analysis. Quantification of ginkgolic acids C15:1 and C17:1 was conducted densitometrically. Among the analyzed products, the presence of ginkgolic acids was confirmed only in herbal drugs containing 60 % ethanolic tinctures of Ginkgo biloba leaves. The use of TLC in the quantification of ginkgolic acids C15:1 and C17:1 in ginkgo extracts was described for the first time.
A competitive enzyme-linked immunosorbent assay (ELISA) for ginkgolic acids (GAs) was developed using monoclonal antibody (MAb) 9F raised against 6-(13-formylheptyl) salicylic acid covalently coupled to bovine serum albumin (BSA). ELISA, at an effective measuring range of 300 ng/ml–1 μg/ml of GA 15:1, was successful in detecting GAs content in ginkgo leaves and standardized extracts due to the lack of cross-reactivity against various related compounds. The sensitive and simple immunoassay developed in this study was validated to be specific for the quantitative determination of total GAs content in ginkgo crude drugs with no interference from the sample matrix. The analytical recovery of spiked GA 15:1 was 103% in a concentration range between 10 and 40 mg/g dry weight of ginkgo leaves.
It is now possible to determine proper motions of high-velocity objects in such a way as to obtain with some accuracy the velocity vector relevant to the Sun. If a potential field of the Galaxy is assumed, one can compute an actual orbit. A determination of the velocity of the globular clusterωCentauri has recently been completed at Greenwich, and it is found that the orbit is strongly retrograde in the Galaxy. Similar calculations may be made, though with less certainty, in the case of RR Lyrae variable stars.
Using the new reductions of the IUE light curves by Sonneborn et al. (1997) and an extensive set of HST images of SN 1987A we have repeated and improved Panagia et al. (1991) analysis to obtain a better determination of the distance to the supernova. In this way we have derived an absolute size of the ringRabs= (6.23 ± 0.08) x 1017cm and an angular sizeR″ = 808 ± 17 mas, which give a distance to the supernovad(SN1987A) = 51.4 ± 1.2 kpc and a distance modulusm–M(SN1987A) = 18.55 ± 0.05. Allowing for a displacement of SN 1987A position relative to the LMC center, the distance to the barycenter of the Large Magellanic Cloud is also estimated to bed(LMC) = 52.0±1.3 kpc, which corresponds to a distance modulus ofm–M(LMC) = 18.58±0.05.
A symposium on the future of the International Latitude Service (I. L. S.) is to be held in Helsinki in July 1960. My report for the symposium consists of two parts. Part I, denoded (Mk I) was published [1] earlier in 1960 under the title “Latitude and Longitude, and the Secular Motion of the Pole”. Part II is the present paper, denoded (Mk II).
In South Africa the modern outlook towards time may be said to have started in 1948. Both the two major observatories, The Royal Observatory in Cape Town and the Union Observatory (now known as the Republic Observatory) in Johannesburg had, of course, been involved in the astronomical determination of time almost from their inception, and the Johannesburg Observatory has been responsible for the official time of South Africa since 1908. However the pendulum clocks then in use could not be relied on to provide an accuracy better than about 1/10 second, which was of the same order as that of the astronomical observations. It is doubtful if much use was made of even this limited accuracy outside the two observatories, and although there may – occasionally have been a demand for more accurate time, it was certainly not voiced.
Application of targeted 2D planar chromatography in the control of ginkgolic acids in some herbal drugs and dietary supplements