Search Results

You are looking at 31 - 40 of 1,889 items for :

  • "Precision" x
  • All content x
Clear All

Abstract  

A slightly modified procedure of direct substoichiometric isotope dilution analysis is theoretically treated and its advantages are stated. The precision of one case of reverse isotope dilution is calculated, and tables for rapid calculation of optimum measuring conditions and of the resulting errors are given. The precision and optimum conditions are calculated for determining the count rate ratios of two radioisotopes present in a mixture using two instruments (absorbers), and pertinent tables are presented.

Restricted access

Abstract  

The high-precision uranium determination by reduction with ferrous sulfate in phosphoric acid and titration with dichromate, which is applicable to nuclear-grade uranium compounds in which the uranium exists nearly exclusively as U(IV), has been modified. The modification enlarges the range of applicability of the original method to include the analysis of uranium compounds in which the uranium exists as U(VI) or as a mixture of U(IV) and U(VI), such as U3O8. The modified method has the same precision, relative freedom from interferences and applicability for routine use as the original method.

Restricted access

Abstract  

The success of a systematic application in INAA using γ-lines of ≥50 keV depends on the accuracy and precision and thus on the reproducibility of the measuring conditions. This text describes a procedure based on a 30 mm2 planar ultrapure Ge detector with a multichannel analyzer.

Restricted access

Abstract  

Some methods for the experimental α-determination in the 1/E1+α epithermal reactorneutron spetrum are critically compared with respect to their accuracy and precision. The analysis is based on the error propagation theory. Besides the general formulae numerical examples are elaborated for specific conditions in the Thetis reactor (Gent) and the WWR-M reactor (Budapest).

Restricted access

Context

Bacoside A, a triterpenoid saponin, is a major constituent isolated from Bacopa monnieri (L.) Wettst. (Scrophulariaceae), used as a memory enhancer. Bacoside A and B are active ingredients in Bacopa herb and have antioxidant and hepatoprotective activities

Objective

A new rapid, simple, and economical high-performance thin-layer chromatographic (HPTLC) method was developed and validated for densitometric quantitative analysis of bacoside A in powdered leaves from different geographical regions of India.

Materials and methods

An amount of 10 mg mL−1 methanol extract of powdered leaves from different geographic regions was used for sample application on precoated silica gel 60 F254 aluminum sheets. Standard bacoside A (1 mg mL−1) was used for calibration curve. HPTLC separation was performed on percolated silica gel aluminum plate 60 F254 (20 cm × 10 cm with 0.2 mm thickness) as a stationary phase using ethyl acetate–methanol–water (4:1:1) as the mobile phase. Quantification was achieved by densitometric analysis at 598 nm over the concentration range of 500–4000 ng band−1.

Result

Compact and well-resolved bands for bacoside A from powdered leaves of different geographic regions were found at retardation factor (R f) 0.53 ± 0.02. The linear regression analysis data for calibration curve showed good linear relationship with regression coefficient r 2 = 0.9996 and r 2 = 0.99810 with respect to peak area and peak height. The method was validated for precision, recovery, and robustness as per the International Conference on Harmonization (ICH) guidelines. Variation in quantitative analysis of bacoside A in powdered leaves sample from different geographic regions was found by HPTLC method.

Discussion and conclusion

The highest and lowest content of bacoside A in powdered leaves sample from Jammu and Kerala regions, respectively. The variety of B. monnieri in Jammu is superior to other regions of India. The proposed developed HPTLC method can be applied for the quantitative determination of bacoside A in powdered leaves of plant and its formulation.

Restricted access

Abstract  

The precision and accuracy of two closely similar radioanalytical methods are compared using the statistical approach (5 parallel experiments for each distribution): sub- and superequivalence isotope dilution analysis and concentration dependent distribution. The solvent extraction system used for both procedures involves the distribution of radiobarium between aqueous phase and nitrobenzene solution of the acid of cobalt dicarbolide H+ {–(3)–1,2–B9C2H11]2 Co and mono-p-nonyl phenyl ether polyethylene glycol HO(CH2 CH3 O)20–(C6H4)C9H13. The influence was tested of the choice of a concrete person to evaluated the results of the analysis by graphic methods upon the precision and accuracy. The advantages and drawbacks of different graphical evaluation procedures are compared.

Restricted access

Abstract  

In this paper we investigate the retrieval capabilities of six Internet search engines on a simple query. As a case study the query “Erdos” was chosen. Paul Erdos was a world famous Hungarian mathematician, who passed away in September 1996. Existing work on search engine evaluation considers only the first ten or twenty results returned by the search engine, therefore approximation of the recalls of the engines has not been considered so far. In this work we retrieved all 6681 documents that the search engines pointed at and thoroughly examined them. Thus we could calculate the precision of the whole retrieval process, study the overlap between the results of the engines and give an estimate on the recall of the searches. The precision of the engines is high, recall in very low and the overlap is minimal.

Restricted access

Abstract  

Some of the rare earth elements have been determined in U.S.G.S. Standard Rocks W1 and G2 using instrumental neutron activation analysis with a Ge(Li) detector. The experimental conditions were chosen to investigate the precision and accuracy to be expected when using the method for routine purposes. The results are compared with data obtained after chemical group separation of the rare earths and with data reported by other workers; the agreement is, in general, good. La, Ce, Nd, Sm, Eu, Tb, Yb, Lu and Se were determined with the instrumental method and, after group separation, data were obtained for Gd, Dy, Ho and Tm in addition. It is concluded that the accuracy of the data obtained with the non-destructive method is, in general, as good as the precision for each element.

Restricted access

Abstract  

A method has been developed to routinely analyse managanese ores and ferro-manganese, by neutron activation making use of a cylindrical 1 Ci226Ra−Be source. A description of the source, the moderator and the pneumatic irradiation facility is given. The irradiation position has been optimized for minimum flux gradients and maximum reproducibility. Samples and standards consist of pellets pressed from a mixture of powdered material and graphite weighing approximately 5 g. Samples and standards alternatively go through a sequence of 20 min irradiation, 20 min decay, and 20 min counting. Pyrolusites containing from 30 to 55% Mn and ferro-manganese containing approximately 80% Mn have been analysed with a precision of 0.1% absolute.

Restricted access

Abstract  

Different reference materials of environmental and geological origin, such as NBS 1633a (Coal Fly Ash, CFA), NBS 1645 (River Sediment, RS), GXR-2, and IAEA Soil-5, were investigated by short time activation analysis. The samples were analyzed in 5 replicates each between 100 to 150 mg, at neutron flux of 1.3 E 12 cm–2 s–1, using a high rate — high resolution gamma spectroscopy with a Loss Free Counting (LFC) System to correct the dead time and pile up to 500,000 cps. The results of the measurements indicate that the precision in determination of28Al,46mSc, and52V is between 1 to 6%. Different evaluation programs (i.e. ALCHEM, AKTAN, and ND-PEAK) were used to calculate the peak areas. The results indicate that, at lower counts, the statistical error of peak area calculation becomes more significant. Finally, Mössbauer spectroscopy was used to investigate the main Fe compounds present in some reference materials.

Restricted access