Publications (3)8.7 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Direct analysis of dried blood spot (DBS) samples was investigated using a prototype semi-automated robotic device that allows the direct elution of sample spots from a DBS paper card to an online SPE cartridge. The eluted SPE samples were analyzed with high-performance LC-MS/MS. A LLOQ of 0.01 ng/ml was achieved with a linear calibration range from 0.01 to 25 ng/ml. Optimal performance data were obtained from spotting the internal standard solution on the card before blood spotting. Internal standard addition from the system injector loop produced intra-assay inaccuracy of -9.0-7.3% and precision of 1.3-8.2%, and inter-assay inaccuracy of -3.5-3.9% and precision of 4.4-8.7%. Results demonstrated the feasibility of a semi-automated online rapid direct elution method that avoids manual extraction for DBS sample analysis using the online DBS-SPE system coupled to LC-MS/MS.
    Bioanalysis 06/2012; 4(12):1445-56. DOI:10.4155/bio.12.111 · 3.03 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A two-layered polymeric membrane is employed for the formation of separated dried plasma spots from whole blood as an alternative to the direct analysis of whole dried blood spots (DBS). This dried plasma spot (DPS) analysis procedure precludes potential issues of hematocrit differences in whole blood samples while providing pharmokinetic data from plasma rather than whole blood. The described procedure is also semi-automated thus providing a simpler work flow for LC/MS/MS bioanalysis procedures. Molecular filtration of red blood cells (RBC) from applied microsamples of whole blood fortified with guanfacine and its stable isotope internal standard was accomplished with a two-layer polymeric membrane substrate. The lower membrane surface containing the separated plasma spot was physically separated from the upper membrane followed by semi-automated direct elution of the sample to an online solid-phase extraction (SPE) cartridge followed by liquid chromatography coupled to tandem mass spectrometry (LC/MS/MS). A two-layer membrane sample preparation substrate produced plasma from whole blood without centrifugation which could be directly eluted for semi-automated LC/MS/MS bioanalysis. Standard curves were constructed by plotting peak area ratios between the analyte and the stable isotope labeled internal standard (SIL-IS) versus the nominal concentration in whole blood. A weighted 1/x(2) linear regression was applied to the data from DPS samples. Standard curves were linear over the range 0.25-250 ng/mL human whole blood. The representative regression equation was y = 0.0142x + 0.00248 (R(2) = 0.995) for the described DPS assay. The described work demonstrates proof-of-principle using membrane sample preparation techniques to form DPS samples from whole blood for subsequent bioanalysis by LC/MS/MS. This approach has the potential to eliminate the hematocrit issues from the current controversy surrounding validation of DBS assays.
    Rapid Communications in Mass Spectrometry 05/2012; 26(10):1208-12. DOI:10.1002/rcm.6212 · 2.64 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Dried blood spot (DBS) technology was evaluated for the quantitative determination of guanfacine in human blood in clinical studies. A very sensitive DBS assay has been developed using HPLC coupled with an AB Sciex 5500 QTRAP® (Applied Biosystems/MDS Sciex, ON, Canada) MS system (LC-MS/MS) with a linear calibration range of 0.05 to 25 ng/ml. High-resolution MS using an Exactive Orbitrap® (ThermoFisher, LLC., CA, USA) was compared with the QTRAP using extracted exact mass ion current profiles for guanfacine and its stable-isotope-incorporated internal standard. The sample preparation employed liquid-liquid extraction with methyl t-butyl ether of 5 mm punched DBS card disks, followed by reversed-phase HPLC separation coupled with either MS/MS or high-resolution MS. Routine experiments were performed to establish the robustness of the DBS assay, including precision, accuracy, linearity, selectivity, sensitivity and long-term stability of up to 76 days. In addition, several factors that potentially affect quantitation were investigated, including blood volume for DBS spotting, punch size and punch location. A sensitive research assay with a LLOQ of 0.05 ng/ml was developed and subjected to several components of a method validation common to a regulated bioanalysis procedure employing DBS. This method development and partial validation study determined that spot volume, punch size or punch location do not affect assay accuracy and precision. The DBS approach was successfully applied to a clinical study (a Phase I, randomized, double-blind, placebo-controlled, crossover study to assess the effect of varying multiple oral doses of guanfacine on the pharmacokinetic, pharmacodynamic, safety, and tolerability profiles in healthy adult subjects). The pharmacokinetic profiles for 12 volunteers generated from the DBS assay and from a previously validated plasma assay were compared and were found to be comparable. DBS incurred samples collected from finger prick blood and directly applied to the DBS cards were also analyzed for comparison. From a bioanalytical perspective, DBS sample collection and analysis is a potentially viable alternative for guanfacine determination in clinical studies, utilizing approximately 100 µl of blood per subject profile compared with a few millilitres of blood drawn for conventional plasma bioanalysis.
    Bioanalysis 11/2011; 3(22):2501-14. DOI:10.4155/bio.11.262 · 3.03 Impact Factor