High-speed gradient parallel liquid chromatography/tandem mass spectrometry with fully automated sample preparation for bioanalysis: 30 seconds per sample from plasma

On-line immunoaffinity-liquid chromatography-mass spectrometry for identification of amyloid disease markers in biological fluids

Disease-specific alterations in proteins and peptides such as the appearance of new isoforms, changed relative concentrations of known isoforms, or changed catabolism characterize the group of protein precipitation disorders collectively known as amyloidoses. The goal of this study was to develop an approach for isolating and characterizing the pool of isoforms of a polypeptide of interest from biological fluids for use in development of diagnostic markers and elucidation of pathogenesis. For this purpose, we employed an on-line immunoaffinity-liquid chromatography-mass spectrometry (IA-LC-MS) modular approach using antibodies binding populations of protein isoforms. In this system, crude biological samples, e.g., serum, may be injected and subjected to fast hands-off analysis. The setup consists of an optional preclear column for removal of unspecific binding components, an immunoaffinity column, a short cartridgelike reversed-phase column, and an electrospray time-of-flight mass spectrometer. We have tested the system for the automated analysis of three amyloid-related polypeptides, serum amyloid P component, amyloid beta-peptide, and beta2-microglobulin, and we show the feasibility of detection of altered isoforms or determination of relative abundance of isoforms of the proteins from serum or cerebrospinal fluid samples. For each new protein investigated, the only change needed in the system is a new antibody or antibody mixture and the selection of a reversed-phase cartridge of appropriate hydrophobicity.

Higher-throughput screening for Caco-2 permeability utilizing a multiple sprayer liquid chromatography/tandem mass spectrometry system

In the current drug discovery environment, higher-throughput analytical assays have become essential to keep pace with the screening demands for drug metabolism and pharmacokinetics (DMPK) attributes. This has been dictated by advances primarily in chemical procedures, notably combinatorial and parallel syntheses, which has resulted in many-fold increases in the number of compounds requiring DMPK evaluation. Because of its speed and specificity, liquid chromatography/tandem mass spectrometry (LC/MS/MS) has become the dominant technology for sample analysis in the DMPK screening assays. For higher-throughput assays, analytical speed as well as other factors such as method development, data processing, quality control, and report generation, must be optimized. The four-way multiplexed electrospray interface (MUX), which allows for the analysis of four LC eluents simultaneously, has been adopted to maximize the rate of sample introduction into the mass spectrometer. Generic fast-gradient HPLC methods that are suitable for approximately 80% of the new chemical entities encountered have been developed. In-house-written software programs have been used to streamline information flow within the system, and for quality control by automatically identifying analytical anomalies. By integrating these components together with automated method development and data processing, a system capable of screening 100 compounds per week for Caco-2 permeability has been established.

Capillary array high-performance liquid chromatography of nucleic acids and proteins

An array of monolithic poly(styrene/divinylbenzene) capillaries with individual column thermostats was constructed to demonstrate its utility for the separation of nucleic acids, proteins, and tryptic digests in combination with UV absorbance detection. Because of polymerization-related variation in surface area of monolithic columns, the concentration of acetonitrile required for elution of DNA fragments in denaturing HPLC may vary sufficiently to affect the degree of denaturation. Modulation of column temperature offers a convenient way to harmonize elution profiles among columns. Individual regulation of column temperature also provides the means to determine rapidly in a single parallel run the optimum temperature for resolution of biomolecules. Given the high reproducibility of separations among columns and the ease with which poly(styrene/divinylbenzene)-based stationary phases can be modified to accommodate different modes of chromatography, such arrays will find broad applicability in proteogenomics.

Ultrafast liquid chromatography/tandem mass spectrometry bioanalysis of polar analytes using packed silica columns

Ultrafast liquid chromatography/tandem mass spectrometry (LC/MS/MS) bioanalysis was demonstrated with the use of packed silica columns operated under elevated flow rates. A special effort has been made to achieve ultrafast analysis without sacrificing chromatographic resolution. Two multiple analyte/metabolites assays, (1) morphine/morphine-6-glucuronide(M6G)/morphine-3-glucuronide(M3G) and (2) midazolam/1'-hydroxymidazolam/4-hydroxymidazolam, were used to demonstrate the speed, sensitivity, peak shape and separation of the ultrafast methods utilizing silica columns. In both methods adequate chromatographic separation was a necessity because quantitation results would be otherwise compromised due to cross interference between different selected reaction monitoring (SRM) transitions. Baseline resolutions between morphine, M6G and M3G in human plasma extracts were achieved within 30 s on a 50 x 3 mm Betasil silica column operated at 4 mL/min of isocratic acetonitrile/water mobile phase. The total injection-to-injection cycle time was 48 s with a simple, single-autosampler/single-column setup, when a Shimadzu SIL-HT autosampler was used. Baseline resolution between 1'-hydroxymidazolam and 4-hydroxymidalolam in monkey plasma extracts was achieved within 33 s using similar conditions. Due to the absence of carry-over in this case, no rinsing of the injection needle was necessary, resulting in a cycle time of only 39 s/sample. These ultrafast methods were successfully used to analyze extracted biological samples and proved to be reproducible, reliable and generated equivalent pharmaco-kinetic (PK) results to those obtained by regular flow LC/MS/MS analysis to support discovery PK studies.

Generic serial and parallel on-line direct-injection using turbulent flow liquid chromatography/tandem mass spectrometry

The development of turbulent flow chromatography (TFC) has enabled considerable growth in the utility of on-line direct-injection technologies. TFC has now become established in a large number of varied analytical environments, particularly drug discovery/pharmacokinetics, metabolite profiling, combinatorial library purification, pre-clinical and clinical GLP applications. The utility of turbulent flow technology for in-house pre-clinical and clinical quantitative applications has necessitated extensive valve-cleaning procedures, and consequently lengthy cycle-times, to effectively remove the system carry-over. In-house requirements for assay validation require carry-over less than 20% of the lowest level of quantification (LLOQ), corresponding to 0.02% carry-over for a linear calibration range incorporating 3 orders. A generic turbulent flow chromatography protocol has been developed for drug discovery that incorporates polymeric turbulent flow extraction (cyclone) with C18-based reverse-phase chromatography. Further, multiple wash steps are incorporated within the methodology to meet in-house requirements for carry-over. Selection of novel switching-valve materials based on polyarylethyl ketone (PAEK) and Hastelloy/Valcon E autosampler injection hardware has enabled us to significantly impact the cycle-time required to reduce carry-over. Consequently, optimal usage of switching valves has enabled parallel operation for a generic on-line direct-injection methodology to successfully reduce the total cycle-time. Overall reductions from 4 min per sample to 90 s per sample are shown with comparable data quality using a proprietary target molecule from 0.1-100 ng/mL. This paper describes the hardware configuration and methodologies utilized to perform generic serial and parallel on-line direct-injection using a Turboflow HTLC 2300 system.

Studies on azaspiracid biotoxins. I. Ultrafast high-resolution liquid chromatography/mass spectrometry separations using monolithic columns

In this study, the performance of monolithic columns was evaluated for ultrafast liquid chromatography/mass spectrometry (LC/MS) analyses and for high-resolution separations of several azaspiracid biotoxin analogs. Because of their high permeability, monolithic columns offer a number of advantages over conventional packed columns; viz., very low backpressures and relatively flat van Deemter curves at high flow rates. That is, very high flow rates can be used for ultrafast analyses or, by using longer than normal columns, high-resolution separations are possible. In a series of experiments, we varied the mobile phase flow rates between 1 and 8 mL/min, and studied their impact on chromatographic parameters such as retention time, resolution, number of plates and pressure. The chromatographic run times could be reduced to ca. 30 s without a significant change in the separation efficiency. A signal intensity comparison revealed interesting differences between atmospheric-pressure chemical ionization (APCI) and electrospray ionization (ESI) in their flow-rate dependency. An explanation with respect to the behavior as of a mass-flow or a concentration-dependent device is given in the paper. Additionally, the column length was varied between 10 and 70 cm. As a result, the number of theoretical plates increased substantially. In the example shown in the report, an increase from 13 000 plates for a 10-cm column to 80 000 for a 70-cm column is demonstrated. In addition, the potential of the monolithic columns for high-resolution LC/MS separations is shown for a complex biotoxin mixture, which was separated on a 40-cm-long column.