Screening by LC–MS-MS and Fast Chromatography: An Alternative Approach to Traditional Immunoassays?

Stefan König, Thomas Wüthrich, Werner Bernhard, and Wolfgang Weinmann (University of Bern, Switzerland)
In our routine drug analysis workflow, urine samples originating from traffic control or accidents and from intoxications are screened by immunoassay (cloned enzyme donor immunoassay) with good selectivity and sensitivity for illegal drugs, psychotropic drugs, hypnotics, and tranquilizers. However, zolpidem, zopiclone, and zaleplone — three important hypnotics — are not part of current immunoassay screening and there is no antibody available for these three compounds. To overcome this disadvantage of our screening workflow, a new technique was developed based on liquid chromatography coupled with tandem mass spectrometry with very short run times, combined with column switching. This method allows for the simultaneous quantification of the "z-drugs" and all major benzodiazepines in human urine samples.

Advantages of HILIC Mobile Phases for LC–ESI–MS–MS Analysis of Neurotransmitters

Raluca-Iona Chirita-Tampu (University of Bacau, Romania), Caroline West, Laetitia Fougere, and Claire Elfakir (University of Orleáns, France)
This article investigates the influence of liquid mobile phase composition on the response measured in electrospray ionization-mass spectrometry (ESI–MS) for 12 selected neurotransmitters. The aim was to find the optimal conditions to achieve sufficient limits of detection (LOD) that would permit their detection by liquid chromatography-tandem mass spectrometry (LC–MS–MS) in biological samples (brain extracts). The advantages of solvent-rich mobile phases typically used in hydrophilic interaction liquid chromatography (HILIC) are clear. The HILIC–ESI–MS–MS system optimized for the 12 selected compounds analysis presented significant advantages over other existing methods.

A Sensitive and Cost-Effective LC–MS-MS Method for Determination of 1, 25-Dihydroxyvitamin D3 in Human Plasma

Jenny P. Dai, Allan Xu, Eric J. Battaglioli, Bruce A. Stanley, and Robin T. Wilson (Pennsylvania State University)
The biologically active form of vitamin D is an important analytical target in both research and clinical practice. However, quantification of 1α,25-dihydroxyvitamin D3 (1,25(OH)2D3) has been challenging because of the extremely low levels in circulation — in the low picograms-per-milliliter range. Here, we report a sensitive, time-efficient, and cost-effective liquid chromatography–tandem mass spectrometry (LC–MS-MS) method that combines the use of immunoaffinity extraction, 4-phenyl-1,2,4-triazole-3,5-dione (PTAD) derivatization, and methylamine adduction.

Inaccuracies in Quantification of Peptides—A Case Study Using Beta Endorphin Assay

H. M. D. R. Herath, R-R Kim, P. J. Cabot, P. N. Shaw, and A. K. Hewavitharana (School of Pharmacy, The University of Queensland)
In recent years, significant attention has been paid to the use of peptides as therapeutic agents. Even though peptides have been shown to be promising therapeutics for many disease conditions, developing them as drugs is a challenging process. Incorrect quantification of peptides may lead to false conclusions in research and may also adversely affect the dosage that is prescribed for patients. Here, we present two possible sources of errors that may both contribute to significant inaccuracy in peptide assay methods: the filtration material (cellulose) used in sample clean up and the vial material (glass and plastic) used in liquid chromatographic analysis. This study is based on β-endorphin but has relevance for most peptide assays.

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