Introduction Complete blood count (CBC) is one of the fundamental tests for assessing a patient's condition. Despite widespread automation in hematology, manual blood smear analysis remains essential. This study aimed to evaluate the use of manual blood smears, both unstained and May–Grünwald–Giemsa (MGG)-stained, as a novel alternative biological matrix for xenobiotic determination.
Methods Analytical standards of selected 2-phenylethylamine derivatives were added to K₂EDTA whole blood, followed by manual smear preparation. Half of the smears were stained using the MGG technique. The developed method involved transferring the matrix from the slide into a test tube, followed by extraction with an n-hexane/ethyl acetate mixture under alkaline conditions. Analyses were conducted using UHPLC-ESI-QqQ-MS/MS. In unstained smears, xenobiotics were monitored across concentrations ranging from pg/mL to µg/mL. Total hemoglobin was evaluated at low (critical), moderate, and normal levels. The method was further applied to evaluate xenobiotic stability in blood smears stored at room temperature, the typical storage condition for such samples.
Results The study demonstrated that unstained blood smears can serve as a valuable alternative matrix for xenobiotic determination, enabling detection not only in poisoning cases (toxic/lethal concentrations) but also in exposure assessments, with a limit of quantification down to the ng/mL range. Despite substantial differences in total hemoglobin concentration, effective xenobiotic detection was achieved. In MGG-stained smears, however, staining steps reduced detection capabilities, and a qualitative interpretation approach is recommended.
Conclusions The results indicate that small blood volumes are sufficient for both qualitative and quantitative toxicological analyses, particularly in unstained smears. Furthermore, the ability to detect substances at trace levels highlights the necessity for cautious interpretation due to contamination risk. The findings regarding unstained blood smears, including stability results, may provide valuable support for toxicological examinations of blood traces on other glass surfaces.
