Development of laboratory reference material: Soil 1. Baseline and highly elevated concentrations of metals and polycyclic aromatic hydrocarbons.

Reference materials play a key part in systems of inspection and quality control of results of analytical measurements. The main limitation in using certified reference materials (CRM) is their high price, which results from the long and costly process of producing the reference material. An alternative to costly CRM materials is the employment of laboratory reference materials, particularly for interlaboratory control of measurement results and procedures. Under the auspices of the Chair of Analytical Chemistry at the Chemical Department of Gdansk University of Technology, research on the development of new reference materials is being conducted. At present, the research is aimed at producing a new laboratory reference material (LRM): 'Soil 1. Baseline and Highly Elevated Concentrations of Metals and Polycyclic Aromatic Hydrocarbons' - LRM soil 1. This paper presents the production stages of the developed laboratory reference material: acquisition of raw material from soil samples taken from the environment of the Tri-city (in Polish, Trójmiasto Gdansk, Sopot, Gdynia) bypass road, homogenization and subsequent dosage into appropriate containers, tests of homogeneity of sampled material within one container and between containers, based on the results of the determination of selected parameters (total carbon, content of optional metals - Hg, Fe, Cu Zn, Mn, Mg, water content, content of PAH-group analytes). The obtained results of homogeneity tests of the proposed future laboratory reference material have confirmed the homogeneity of soil samples within a container and between containers. Currently, interlaboratory tests are being carried out to determine the reference value.

Evaluation of porcelain surface treatments and agents for composite-to-porcelain repair.

Intraoral repairs often involve bonding composite to fractured porcelain. Newer adhesive systems, currently referred to as multipurpose systems, include materials with recommended procedures for repair of porcelain. This laboratory study evaluated various treatment regimens with the ProBond adhesive system. Three different porcelain surface procedures were used: (1) air abrasion with aluminum oxide (50 microm), (2) 8% hydrofluoric acid, and (3) air abrasion and hydrofluoric acid. Eight different treatment procedures were then used to bond 10 composite cylinders to porcelain surfaces in each group. Shear bond strengths (in megapascals) were determined with an Instron testing machine after storage in water for 24 hours at 37 degrees C and after 3 months of storage and thermocycling. The combination of air abrasion and hydrofluoric acid on porcelain surfaces before bonding composite recorded the most consistently effective bond strengths. Four of the treatment regimens in the air abrasion groups yielded low bond strengths at 3 months. This study also indicated that silane treatment of porcelain is critical for development of suitable bond strengths for composite.

Laboratory evaluation of surface treatments for composite repair.

This laboratory study evaluated the strength of composite repairs using various surface treatment procedures. Roughening a previously cured composite surface, with either a diamond instrument or aluminum oxide air abrasion, yielded composite to composite repair strengths that were not significantly different (P > 0.05) than bonding composite to the air-inhibited layer of a cured composite. The bond strengths of composite repairs were slightly higher when using an unfilled bonding agent but not significantly different (P > 0.05) than the same repair techniques without the bonding agent.