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1.
It is known that a distance-regular graph with valency k at least three admits at most two Qpolynomial structures. We show that all distance-regular graphs with diameter four and valency at least three admitting two Q-polynomial structures are either dual bipartite or almost dual bipartite. By the work of Dickie(1995) this implies that any distance-regular graph with diameter d at least four and valency at least three admitting two Q-polynomial structures is, provided it is not a Hadamard graph, either the cube H(d, 2)with d even, the half cube 1/2H(2d + 1, 2), the folded cube?H(2d + 1, 2), or the dual polar graph on [2A2d-1(q)]with q 2 a prime power. 相似文献
2.
J. H. Koolen 《European Journal of Combinatorics》2002,23(8):987
Bannai and Ito conjectured in a 1987 paper that there are finitely many distance-regular graphs with fixed degree that is greater than two. In a series of papers they showed that their conjecture held for distance-regular graphs with degrees 3 or 4. In this paper we prove that the Bannai–Ito conjecture holds for degrees 5–7. 相似文献
3.
Phillip L. Kempster Jacobus F. Staden Henk R. Vliet 《Fresenius' Journal of Analytical Chemistry》1988,332(2):153-156
Summary Using an 11 ml centrifugal type spray chamber, a rapid sample introduction rate of 320 injections per hour may be achieved when interfacing flow injection analysis and inductively coupled plasma emission spectrometric techniques. Calcium was determined in water samples with a relative standard deviation of better than 3.5% over the analytical range of 10 to 200 mg · l–1 Ca. Mean recovery was 97%.
Calciumbestimmung im Wasser mit dem Flow-injection-Prinzip kombiniert mit der Induktions-gekoppelten Plasma-Emissions-Spektrometrie (FIA-ICP)相似文献
4.
Development and validation of a stability-indicating HPLC method for the determination of degradation products in dipyridamole injection 总被引:1,自引:0,他引:1
Summary The development and subsequent validation of an isocratic high-performance liquid chromatographic (HPLC) procedure employing
ultraviolet (UV) detection for the determination of degradation products in Dipyridamole Injection is reported. The development
of this assay involved the evaluation of several factors including buffer type, ionic strength, pH, organic composition, and
column type. The described method is simple, reproducible, accurate, and selective. The precision, relative standard deviation
(RSD), amongst five sample preparations for total degradation products was not more than (NMT) 10.2 %, while the individual
degradation products were NMT 12.1%. Intermediate precision, as determined from fifteen sample preparations, generated by
two Analysts on different HPLC systems over three days, exhibited an RSD for total and individual degradation products of
8.2 % and NMT 27.5 %, respectively. The mean absolute recovery of dipyridamole using the described method is 102.1±1. 9%,
(mean±SD, n=12) over the concentration range of 0.03 % to 5.0 % of its label claim of 5 mg mL−1. The limit of detection and limit of quantitation were 0.1 and 0.3 μg mL−1, respectively. The linearity of the peak response was verified with respect to dipyridamole concentration over a range of
0.3 and 50 μg mL−1 (0.03 % to 5.0 % label claim). The Standard and Assay Preparations are stable for up to 48 hours at room temperature. The
selectivity was evaluated by subjecting the finished product (Dipyridamole Injection) to thermal, acidic, basic, oxidative
and fluorescent radiation stress conditions. No interference in the analysis of degradation products was observed, showing
the method is stability-indicating. 相似文献
5.
A simple and sensitive sequential injection spectrophotometric procedure is proposed for the determination of trace amounts of iodide in pharmaceutical preparations. The method is based on the catalytic effect of iodide on the (tetra base) 4,4′-methylenebis(N,N-dimethylaniline)-chloramine-T reaction in acidic solution. The method involves a sequential aspiration of 255 μl sample/standard followed by 170 μl tetra base and then 128 μl chloramine-T solutions into a carrier stream to be stacked inside a holding coil and flow reversed through a reaction coil towards a detector. The resulting colored compound is measured at 600 nm using an UV/Vis-spectrophotometer. All the parameters that affect the reaction were evaluated and the calibration curve is linear over a range of 0.1–6.0 μg l−1 of iodide concentration with detection limit of 0.05 μg l−1. A sample throughput of 80 samples per hour and relative standard deviation of less than 2.0% was achieved. The method is successfully applied for the determination of iodide in three different samples (tablets). 相似文献
6.
A new class of monocrystalline diamond paste-based electrodes is proposed for the determination of chromium(III) at trace levels in vitamins. Three types of monocrystalline diamond—natural diamond 1 (natural diamond), synthetic diamond 50 (synthetic-1), and synthetic diamond 1 (synthetic-2)—were used for electrode construction. The linear concentration ranges are between 10–10 and 10–8; 10–9 and 10–7, and 10–10 to 10–8 mol L–1, with limits of detection of 10–12, 10–12, and 10–11 mol L–1, when natural diamond, synthetic-1, and synthetic-2, respectively, are used as electrode materials. For electrodes based on natural diamond and synthetic-1 it was found that Cr(III) yields a peak at about +0.275±0.015 V (vs. Ag/AgCl) within a predetermined positive potential range situated between +0.4 and +0.2 V, while for the electrode based on synthetic-2 the peaks are found at +0.300±0.015 V (vs. Ag/AgCl). The proposed method is reliable for the determination of chromium(III) at trace levels in two vitamin tablets (RSD<0.2%). 相似文献
7.
Enantioselective, potentiometric membrane electrodes (EPMEs) based on carbon paste impregnated with different maltodextrins {dextrose equivalent (DE) 4.0-7.0 (I), 13.0-17.0 (II) and 16.5-19.5 (III)} as chiral selectors for the assay of S-perindopril is described. The proposed electrodes could be reliably employed in the assay of S-perindopril raw material and from its pharmaceutical formulation, Coversyl® tablets. The electrode based on maltodextrin (I) showed the best enantioselectivity and time-stability. The surfaces of the electrodes are easily renewable by simply polishing on an alumina paper. 相似文献
8.
A fully automated sequential injection spectrophotometric method for the determination of phenylephrine hydrochloride in pharmaceutical preparations is reported. The method is based on the condensation reaction of the analyte with 4-aminoantipyrine in the presence of potassium ferricyanide. The absorbance of the condensation product was monitored at 503 nm. A linear relationship between the relative peak height and concentration was obtained in the range 0.5-17.5 mg l−1. The detection limit (as 3σ value) was 0.09 mg l−1 and repeatability was 0.8 and 0.6% at 2.5 and 5 mg l−1, respectively. Results obtained by this method agreed very well with those obtained by the AOAC official method. 相似文献
9.
Jacobus F. van Staden Cornelius J. Hattingh Daniel Malan 《Fresenius' Journal of Analytical Chemistry》1995,351(8):758-761
An on-line gas diffusion/dialyser unit has been designed and incorporated into the manifold of a flow injection system for the simultaneous determination of two different species in a single sample injected into the FIA system. A fast and reliable fully automated two-component flow injection procedure has been carried out where a single sample (50 l industrial effluent water) is injected into a carrier stream and simultaneously gas diffused and dialysed in a single on-line gas diffusion/dialyser unit for the determination of ammonia and chloride, respectively. The results obtained for the ammoniacal nitrogen and chloride in industrial effluent water compared well with data obtained by standard methods. The relative standard deviation for industrial effluent water samples with concentrations of ammoniacal nitrogen in the range between 0.050 and 1 g/l and chloride from 0.127 to 2.531 g/l have been better than 1.0% for ammoniacal nitrogen and 0.5% for chloride, respectively. The proposed system could be attractive for routine analyses of industrial effluent water. 相似文献
10.
Jacobus F. van Staden 《Fresenius' Journal of Analytical Chemistry》1995,351(2-3):181-185
The on-line double membrane dialyser described previously was coupled in series to a single dialyser in the manifold of a flow injection system to include the determination of samples with a high chloride content simultaneously with calcium in industrial effluents from a single sample injection. 50 l of industrial effluent samples are injected into a carrier stream and are simultaneously dialysed in the double on-line dialyser for chloride and calcium. The dialysed chloride sample zones are further directed to a second dialyser that is incorporated in series with the first dialyser. This enables laboratories to determine samples with a very high chloride content up to 60 g/l simultaneously with calcium by using an automated tandem on-line dialysis technique. The fast and reliable fully automated two-component flow injection procedure operated at a sampling frequency of 90 samples per hour and the results obtained for chloride and calcium in industrial effluents compared well with those obtained by standard methods. 相似文献