Vladimir Grdinić

Simultaneous determination of traces of heavy metals by solid-phase spectrophotometry

A coupling sensitive solid phase spectrophotometric (SPS) procedure for determination of traces of heavy metals (Me-SPS) and multicomponent analysis by multiple linear regressions (MA), a simple methodology for simultaneous determination of metals in mixtures was inaugurated. The Me-SPS procedure is based on sorption of heavy metals on PAN-resin and direct absorbance measurements of colour product Me-PAN sorbed on a solid carrier in a 1-mm cell. This methodology (Me-SPS-MA) was checked by simultaneous determination of metals in synthetic mixtures with different compositions and contents of metals important in pharmaceutical practice: Zn, Pb, Cd, Cu, Co, and Ni. Good agreement between experimental and theoretical amounts of heavy metals is obtained from the recovery test (78.3-110.0%). The proposed method enables determination of particular metal ion at the ng mL(-1) level and it was successfully applied to the determination impurities from heavy metal traces in pharmaceutical substances (Cu in ascorbic acid, Pb in glucose, and Zn in insulin). The proposed procedure could be possible contribution to the development of pharmacopoeial methodology for a heavy metals test.

Spectrophotometric determination of vanadium(V) with desferrioxamine B

A naturally occurring trihydroxamic acid, desferrioxamine B, reacts with the vanadium(V) ion in strongly acidic aqueous solutions producing a stable 1 : 1 complex (log K= 6.09 at 22 °C). This red-violet chelate, used for the spectrophotometric determination of trace amounts of vanadium(V)(λmax.= 480 nm, molar absorptivity, Iµ= 3.15 × 103 l mol–1 cm–1), obeys Beers law in the vanadium concentration range 0.5–50.0 p.p.m. The interferences of many foreign substances have been examined, and a sensitive, highly selective, accurate and precise method for the determination of vanadium(V) is proposed.

Surface and capillary effects on detection limits of chromophoric analytical systems

Abstract Sorption and capillary effects of a solid supporter in microqualitative analysis can be studied using suitable chromophoric analytical systems. The identification limits (LI) of various analytical tests have been determined applying several types of microqualitative supporters of ion-exchange resin group and filter paper. The differences in LI values can be explained by the differences in phase volumes and areas in which the analytical reaction product ( AR ) accumulates. Accumulation of AR by sorption and division of AR by capillary spreading have the opposite effects on LI values. When AR is a colored complex the place of its formation in the identification test has also significant effect on LI values. However, it is difficult to correlate the sorption of AR on a supporter to the conditions of its formation in the solution and to the ionic character of the complex. Also, no relationship between simple physical properties of supporters and detection limits developed. The experimental techniques applied (spot test, resin spot test, ring test) affect the sensitivity of the microqualitative analysis significantly.

Importance of factors for ruggedness test in phase solubility analysis

Abstract In the preparation of chemical reference substances for pharmaceuticals it is essential to make an accurate assessment of the content of impurities. The phase solubility analysis (PSA), a method based on intrinsic thermodynamic properties of matter, is employed to detect contaminating substances and to estimate their concentration. Factors that influence the performance of the PSA method, particularly the reproducibility, are varied to find the optimal analytical conditions and to design a sufficiently rugged method. The ruggedness test is carried out by deliberately varying factors: weight of sample, solvent composition, bath temperature, agitation time, agitation speed, amount of clear solution and others. Simple factorial experiments can be applied to develop a procedure for routine determinations of the purity of a substance through the application of precise solubility measurements.