Celina Pieszko

Derivative spectrophotometry in the analysis of mixtures of phenols and herbicides

Derivative spectrophotometry (zero-crossing technique) was applied to the determination of selected phenols and herbicides in two-component mixtures. Methyl- and chlorophenols (3-methylphenol, 2,3- and 3,4-dimethylphenol, 2,5-, 2,6- and 3,4-dichlorophenol and 2,4,5-trichlorophenol) and triazine, uracil and urea herbicides (simazine, propazine, hexazinone, bromacil and metoxuron) were examined. The RSD values ranged between 0.05 and 4% and the recoveries obtained were between 97 and 110%. The developed derivative spectrophotometric method was also applied as a complementary technique for the separation of overlapping peaks of sample compounds obtained by HPLC with diode-array detection. Metoxuron and 3-methylphenol, metoxuron and 2,5-dichlorophenol and simazine and 2,6-dichlorophenol were determined simultaneously by this method at the level of 1 x 10(-3) g l-1.

Determination of energizers in energy drinks

The method of UV/VIS derivative spectrophotometry for the determination of caffeine and B vitamins in energy drinks after solid phase extraction has been developed. Caffeine has been determined in the mixture with B2 vitamin with zero-crossing technique from the I derivative spectra (λ = 266.8 nm), and B3 in mixture with B6 vitamin from the II derivative spectra (λ = 280.1 nm). B12 vitamin has also been determined in a three-component mixture with vitamins B3 and B6. Taurine in drinks has been determined from the basic spectra after derivatization with ninhydrin (λ = 570 nm).

ANALYSIS OF SOME AROMATIC AMINES BY MEANS OF DERIVATIVE SPECTROPHOTOMETRY

ABSTRACT Derivative spectrophotometry (DS) was applied for the determination of selected aromatic amines in two-compound mixtures. Following pairs were analysed: o- and m-toluidine, o- and p-toluidine, m- and p-toluidine; o- and m-phenylenediamine (PDA), o- and p-PDA, m- and p-PDA; p,p′-diaminodiphenylmethane (DADPMe) and p-toluidine. The developed method of DS was used as a complementary technique to HPLC with DAD detector as it allows the determination of compounds, which give a common peak in a chromatographic system.

Derivative spectrophotometry in the analysis of bromacil and metoxuron in the presence of simazine or propazine and hexazinone

ABSTRACT The method for the determination of propazine, simazine, bromacil, hexazinone and metoxuron by zero order and derivative spectrophotometry has been worked out. In the three-component mixtures it was possible to analyse metoxuron and bromacil in the presence of simazine or propazine and hexazinone applying the first order derivative spectra (zero-crossing technique). Detection was at 298.0 nm and 310.0 nm for bromacil and metoxuron, respectively. Calibration graphs were linear from 1 to 50 mg/l for bromacil and 1 to 30 mg/l for metoxuron. Recoveries were 98–120% for water; the RSD (n = 5) were 0.6–4.9%. For soil, recoveries were 90–130% and the RSD (n = 5) were 1.5–14.8%.

Separation and identification of metals in human bones, placenta and milk and in air by adsorption and ion-exchange thin-layer chromatography.

A TLC method for the separation of heavy metals and their complexes with dithizone, 4-(2-pyridylazo)resorcinol and ethylenediaminetetraacetic acid was devised and conditions for the solid-phase extraction of heavy metal ions in human bones, placenta and milk after microwave mineralization and in air after alkaline absorption were elaborated.

UV spectrophotometric investigations of biologically active maleic anhydride copolymers

UV spectra and absorption coefficients of biologically active copolymers of maleic anhydride with carbohydrates, terpenes and 1,3-dioxane derivatives were measured. The quantitative relationships of absorbance vs concentrations of polymers were determined as well. The possibility of determining the copolymer contamination due to monomers and oligomeric compounds was shown.