Jadranka Vuković

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.

Characterization of disposable optical sensors for heavy metal determination

This paper presents the development, characterization and quality control of analytical methods based on the use of disposable optical sensors for determination of heavy metals. Chromogenic reagents such as 1-(2-pyridylazo)-2-naphthol, (2-pyridylazo)resorcinol, Zincon, Ferrozine, and Chromazurol S were used to develop optical sensors of heavy metal ions found as contaminants in pharmaceutical substances and products, such as Zn(II), Cu(II), Ni(II), Fe(II), and Fe(III). The chromogenic reagents were immobilized in polymeric membranes by spin-coating from cocktails containing all reagents needed. The methods were prevalidated using a comprehensive quality control strategy based on a system of mathematical/statistical testing and diagnosis of each prevalidation step. This system involved characterization of analytical groups; checking of two limiting groups; testing of data homogeneity; recognition of outliers; and determination of analytical functions, limiting values, precision and accuracy. The prevalidation strategy demonstrated the reliability of the proposed method and pointed out some limitations. Combining the optical sensors with multicomponent linear regression allowed simultaneous determination of multiple metals in synthetic mixtures with different compositions. Good agreement between experimental and theoretical amounts of heavy metals in the mixtures was obtained for the majority of sensors and metals. Even better agreement was obtained between the experimental and theoretical total amounts of metals in the mixtures. The proposed analytical methods were successfully applied to the determination of zinc in pharmaceutical preparations of insulin and the determination of metal mixtures in a commercial nasal spray of isotonic seawater. The reliable and sensitive individual optical sensors developed in this study may be useful for designing a multimembrane optical tongue that with appropriate further optimization can be used for screening heavy metals in various matrices.

Trichome micromorphology in Teucrium (Lamiaceae) species growing in Croatia

Micromorphological investigation of the types, dimensions and distribution of characteristic trichomes in leaves and stems in Teucrium L. species (T. arduini L., T. chamaedrys L., T. flavum L., T. montanum L., T. polium L., and T. scordium L. subsp. scordioides Schreb.) distributed in Croatia was carried out as part of the taxonomical study of the genus Teucrium. Secretory types of hairs, peltate and capitate hairs were observed on the epidermis of stems and leaves of all investigated species. Non-secretory, acicular hairs were almost completely lacking on stems of T. scordium subsp. scordioides. Flagelliform hairs were not found in T. flavum and T. polium. Cladose hairs were present only in T. polium. The largest micromorphological variability was established between wild and cultivated samples of T. arduini and T. scordium subsp. scordioides, while cultivated and wild specimens of T. polium were almost identical. Differences were primarily observed in trichome dimensions and much less in micromorphological features.

One-step solid-phase UV spectrophotometric method for phenol determination in vaccines: Development and quality assessment

A solid-phase spectrophotometric technique was used to develop very sensitive, inexpensive, onestep procedure for determination of phenol (UV-SPS procedure). The proposed procedure is based on simultaneous sorption of phenol on an anion exchanger QAE Sephadex A-25 (40 mg), within 10 min at pH 11 and measurement of the intrinsic absorbance of the solid phase in a 1-mm cell at 289 and 500 nm, without previous derivatization. The optimum experimental conditions were investigated and comprehensive quality control of the new procedure was carried out using a prevalidation strategy accompanied by a very informative system of diagnosis. The UV-SPS procedure is characterized with both ideal calibration and analytical evaluation function within analyte working range from 0.3 to 3.0 μmol (6.0 to 60.0 nmol/mL). Random deviations (from ±0.3 to ±5.0%) and systematic deviations (from −3.0 to +4.9%) confirmed the favourable precision and accuracy of the UV-SPS method. Evaluated limiting values (LD = 1.0 μM, LQ = 6.0 μM) showed that this method enables determination of very low levels of phenol. The sensitivity of UV-SPS procedure is 50 times higher than that provided by the corresponding method in solution. The UV-SPS method was successfully applied to the determination of phenol in vaccines (recovery 95.6–103.4%).