LCGC North America-07-01-2016

While immunoassay (EIA) is a prevalent screening technique it is also prone to issues such as high false positive rates because of lack of analyte specificity. Mass spectrometry was therefore investigated as an alternative screening technique for the ability to improve analyte specificity on a comparable time scale. In this study, a rapid online sample preparation and injection method was developed using a commercially available guard cartridge on a conventional LC–MS-MS system. Using a two-point calibration curve to provide semi-quantitation, a robust method was developed and validated that improved upon the high false positive rate observed in immunoassay screening.

How to optimize the key variables in GC analysis–GC columns and detectors

A reliable autosampler is one key requirement for unattended operation of a liquid chromatograph.

A solid phase microextraction (SPME) method was developed using a new overcoated PDMS–DVB fiber for immersion extraction of pesticide residues from spaghetti sauce. The overcoating, which consisted of polydimethylsiloxane, offered protection to the SPME fiber, making it more resistant to physical and chemical damage. Also, it increased fiber selectivity for the smaller analyte molecules over macromolecules present in sample matrix. This then allowed it to be used in immersion extraction of a very complex matrix-spaghetti sauce. Performance of the overcoated fiber was compared to a nonovercoated fiber of the same chemistry for method accuracy, precision, and durability. The SPME method developed using the overcoated fiber was then compared to extraction of the same pesticides in spaghetti sauce using a conventional QuEChERS method for extraction and cleanup. SPME was comparable to the QuEChERs method for both accuracy and precision. However, its main advantage over QuEChERS was in sensitivity and method simplicity.

While gas chromatographers may take their septa for granted, in fact these small and seemingly unremarkable polymer discs keep air out of the carrier gas stream when used in an inlet and keep sample intact and uncontaminated when used in a sample vial. Choosing the wrong septa can compromise method accuracy and repeatability as well as reduce column lifetime in extreme cases. This installment addresses septa for inlets and sample vials.

Microflow LC–MS-MS has seen a surge of attention, development, and popularity among research scientists and bioanalysts over the last few years. The potential of this technology to provide better sensitivity, less solvent waste, near-zero dead volume, and high through-put are a big part of this renewed interest. However, microflow LC techniques are hardly a new idea. More than 40 years ago, in 1974, a group at Nagoya University in Japan first developed a microcolumn liquid chromatography system, elements of which can be found in today’s commercial products. With the advances in technology over the last several years, development and implementation of this technique have been kicked into high gear. In this article, we discuss the history of microflow LC–MS-MS, the current state of the art, and where the future might lead for this rapidly growing technology.

This application note demonstrates the analysis of charge variants of Rituximab (both innovator and biosimilar molecules) using multiple heart-cutting two-dimensional liquid chromatography (2D-LC) with mass spectrometry (MS) detection.

Click the title above to open the LCGC North America July 2016 regular issue, Vol 34 No 7, in an interactive PDF format.