Determination of lopinavir cerebral spinal fluid and plasma ultrafiltrate concentrations by liquid chromatography coupled to tandem mass spectrometry.

A method for the determination of lopinavir (LPV) concentrations in cerebral spinal fluid (CSF) and plasma ultrafiltrate (UF) was developed and validated to analyze clinical specimens from patients receiving antiretroviral treatment with lopinavir/ritonavir. The CSF (400 microL sample volume) final calibration range for LPV was 0.313-25.0 ng/mL. The final calibration range for UF (50 microL sample volume) was 1.25-100 ng/mL. The samples were prepared using liquid-liquid extraction, concentrated, and analyzed using a reversed phase isocratic separation. Detection was achieved in positive mixed reaction monitoring mode on a triple quadrupole mass spectrometer. Isolation of LPV through chromatographic separation and proper selection of calibration matrix were important factors in achieving accurate results. Plasma UF was found to be an equivalent calibration matrix to CSF whereas plasma matrix produced a positive bias in samples with unknown concentrations. Artificial CSF media prepared chemically were biased and less superior than UF. Sources of plasma for the UF did not affect accuracy. Several CSF sources were tested for specificity of the method and LPV concentrations were accurately produced with atmospheric pressure chemical ionization source producing more accurate results than the electrospray source. The method successfully measured LPV concentrations in CSF that were previously undetectable by HPLC as well as UF from protein binding studies.

Evaluation of lacrimal fluid as an alternative for monitoring glucose in critically ill patients.

OBJECTIVE: This study evaluated the use of lacrimal fluid glucose concentrations as a minimally invasive, alternative sampling strategy for monitoring glucose concentrations in surgical/trauma ICU patients. DESIGN AND SETTING: Prospective, paired sample study in an adult surgical/trauma ICU. PATIENTS: Patients receiving subcutaneous or intravenous insulin requiring routine capillary blood glucose measurements. Patients receiving ocular lubricants, artificial tears, or routinely administered ophthalmic medications and patients with facial injuries were excluded. INTERVENTIONS: Lacrimal fluid was collected using glass capillary tube placed near the cul-de-sac of the eye. Capillary blood glucose was determined using a bedside glucose meter as per routine ICU care. MEASUREMENTS AND RESULTS: Lacrimal fluid glucose concentration was analyzed using high-performance liquid chromatography with pulse amperometric detection. Forty-four paired samples from five patients were analyzed. Pearson correlation between lacrimal fluid (microM) and blood glucose (mM) concentrations and the proportional change from baseline revealed no significant associations. Due to the very poor association, enrollment was discontinued after five patients. CONCLUSIONS: Lacrimal fluid and blood glucose concentrations were poorly correlated, suggesting that the former is not a reliable alternative to blood glucose monitoring in surgical/trauma ICU patients requiring insulin therapy.

Separation of bioconjugated quantum dots using capillary electrophoresis.

Capillary electrophoresis (CE) with laser-induced fluorescence (LIF) detection was used to separate different bioconjugated CdSe/ZnS quantum dots (QDs). The QD nanocrystals studied were conjugated to the biomolecules streptavidin, biotin, and immunoglobulin G. The bioconjugated QDs showed different electrophoretic mobilities, which appear to depend upon the biomolecule that is attached to the QD and the buffer solution used. The use of a polymeric additive into the CE run buffer improved the resolution of the bioconjugates. Under CE conditions, the interaction between QD bioconjugates containing streptavidin (QDSt) and biotin (QDBi) was monitored. Under a given set of experimental conditions, the fluorescence intensity of QDSt and QDBi emitting light at 655 nm indicated that about 90% of QDBi complexed with 70% of QDSt. A two-color experiment that made use of two different sizes of QD (i.e., 585 and 655 nm) indicated that 30% of the 655 nm QDBi complexed with 53% of the 585 nm QDSt. The use of QDs with different emission properties allows the selective monitoring of two different wavelengths while using one single excitation source. This, in turn, allowed the monitoring of overlapping peaks in the electropherogram when newly formed products resulting from the interaction of the two bioconjugated QDs appeared.