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Articles by Barbara Walna
Total Records ( 2 ) for Barbara Walna
  Kamila Klimaszewska , Costel Sarbu , Zaneta Polkowska , Barbara Walna and Jacek Namiesnik
  A highly informative chemometrical method using linear discriminant analysis was employed in this paper for the characterisation and classification of hoarfrost samples collected in Poland. From the classification matrix, it was concluded that good discrimination (an overall 69% correct classification and 93% correct classification for the samples originated from Gdańsk) between hoarfrost samples of different origin could be achieved by using the ion concentrations retained in the model. Discriminant analysis was not only used for classifying the hoarfrost samples according to origin and location but also for detecting the most important variables that discriminate between the groups. It was found, according to different statistical parameters, that the highest contribution to the discriminatory power of the model was given by NO3*=0814; F=5.54), PO43–*=0.888; F=3.06) and F-*= 0.892; F = 2.92). The smallest contribution was observed for Mg2+*=0.961; F=0.98). The results obtained in this study illustrate that discriminant analysis allows a rational classification and grouping of hoarfrost samples using chemical composition for their characterisation.
  Iwona Kurzyca , Barbara Walna and Jerzy Siepak
  The paper presents some research problems concerning the use of different methodologies, particularly focusing on reliability and comparability based on the authors' own research and some literature. The differences involving such factors as the place, mode and frequency of sampling, kinds of samples taken, duration and method of storage from the time of sampling to the time of analysis, preparation of samples for analysis, and verification and interpretation of the results, were investigated. The most significant changes were observed in precipitation samples obtained as a result of different collecting procedures - both in terms of method and frequency. The differences in concentrations of some ions for the corresponding samples of wet and bulk deposition exceeded 100%. On the other hand, the equalisation of samples and results led to the differences in results reaching 20%. The results of analyses of precipitation samples collected within a certain time sequence (monthly) poured together in amounts proportional to the precipitation events, differed from the figures obtained for samples collected on a daily basis and averaged. The greatest differences were observed in the pH and in concentrations of  ,  , and Ca2+. The changes of the composition of precipitation samples stored at a variety of conditions were also investigated. The greatest changes were observed for    , and   concentrations. Changes in pH during storage could even range over 1.6 units, which corresponded to more than a 15-fold difference in H+ concentrations. Evaluation of analytical methods applied with the verification of the validation parameters has been also presented. Moreover, data verification and interpretation by a different method, e.g. comparing the measured value of conductivity with the calculated one or balancing the determined cations and anions, as well as use of statistics (including chemometric techniques), are presented.
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