Toxicological analyses: analytical method validation for prevention or diagnosis.

The need for reliable results in Toxicological Analysis is recognized and required worldwide. The analytical validation ensures that a method will provide trustworthy information about a particular sample when applied in accordance with a predefined protocol, being able to determine a specific analyte at a distinct concentration range for a well-defined purpose. The driving force for developing method validation for bioanalytical projects comes from the regulatory agencies. Thus, the approach of this work is to present theoretical and practical aspects of method validation based on the analysis objective, whether for prevention or diagnosis. Although various legislative bodies accept differing interpretations of requirements for validation, the process for applying validation criteria should be adaptable for each scientific intent or analytical purpose.

A new restricted access molecularly imprinted fiber for direct solid phase microextraction of benzodiazepines from plasma samples.

Restricted access molecularly imprinted polymers (RAMIPs) are hybrid materials that present selective binding sites for a template (or similar molecules), and an external hydrophilic layer that avoids the binding of proteins to the material, making them appropriate for the sample preparation of protein fluids. RAMIPs have been used successfully in online and offline solid phase extractions, but there is no application as a fiber in solid phase microextraction (SPME), to the best of our knowledge. In this paper, molecularly imprinted fibers were synthesized inside glass capillary tubes (0.53 mm i.d.), using diazepam and methacrylic acid as template and functional monomer, respectively. The MIP fibers were coated with a cross-linked bovine serum albumin (BSA) layer, resulting in RAMIP fibers that were used in the SPME of benzodiazepines directly from biological fluids. The BSA layer acts as a protective barrier that avoids the binding of proteins from the sample by an electrostatic repulsion mechanism. The protein exclusion capacity of the RAMIP fiber was about 98%, which is selective to benzodiazepines in comparison with other drugs (citalopram and fluoxetine). The SPME was optimized and the extraction conditions were set as follows: 1000 µL of the sample diluted with water (1 : 0.5, v : v), no pH adjustment, an extraction time of 20 min at 500 rpm, and elution with 200 µL of acetonitrile for 5 min at 500 rpm. The fibers were used in the SPME of benzodiazepines directly from plasma samples, followed by HPLC-DAD analyses. The method was linear for bromazepam (50-750 µg L-1), clonazepam (15-250 µg L-1), alprazolam (15-350 µg L-1), nordiazepam (100-2100 µg L-1) and diazepam (100-2600 µg L-1), with correlation coefficients higher than 0.97. Relative standard deviations (precision) and relative errors (accuracy) ranged from 0.5 to 20.0%, and -15.6 to 21.6%, respectively.

New advances in restricted access materials for sample preparation: A review.

The determination of organic and inorganic analytes from biological samples need efficient sample preparation procedures in order to capture the analyte in a media with many macromolecules, which can cause analytical errors and problems with the instruments. Thus, "intelligent" sorbents, called restricted access materials (RAMs), have been widely used with these samples, due to their ability to retain analytes and exclude macromolecules. These materials have been obtained by modifying the external surfaces of conventional sorbents (e.g. polymers, carbon nanotubes, active carbon, and silica-based materials) with hydrophilic groups (chemical barrier), as well as by the presence of small pores (physical barrier) accessible only to low molecular weight molecules. Supramolecular solvents (SUPRAs) have also been used as RAMs, due to their abilities to exclude proteins according to size or through precipitation with the solvents. Therefore, due to the relevance of these materials, this review presents an overview of the most recent advances in obtaining RAMs based on silica, polymers, carbon nanotubes, (activated) carbon, and solvents, as well as their applications in biological sample preparation.