Optimizing the balance between false positive and false negative error probabilities of confirmatory methods for the detection of veterinary drug residues

Sensitive detection of clenbuterol by hybrid iridium/silicon nanowire-enhanced laser desorption/ionization mass spectrometry

There is increasing demand for anti-doping drug monitoring in sports and food safety checks by developing sensitive and fast analytical methods. Here we report the development of hybrid Ir/SiNW as a new MALDI matrix for the detection of small molecules. This matrix is characterized by sufficient UV absorption, low-noise background, and high efficiency in ionization of small molecules. Sensitive detection of clenbuterol (LOD: 0.18 pmol) and a variety of other small molecules has been achieved using the Ir/SiNW matrix with a reproducible performance. Compared to the individual components separately, the matrix of hybrid Ir/SiNW synthesized via in situ growth can promote the MS signal intensity by up to 10 fold under identical experimental conditions. We provide a unique mechanism for the high performance of the hybrid Ir/SiNW matrix with the characteristic properties of hydrogen atom transfer and enhanced protonation at the interface of the hybrid nanostructures. Our approach of using a hybrid Ir/SiNW matrix enables detection of clenbuterol quantitatively in complicated biological samples and in vivo experiments, promising a useful tool for food security and anti-doping drug monitoring in sports.

Establishing the fitness for purpose of mass spectrometric methods

This report is submitted by a working group sponsored by the ASMS Measurements and Standards Committee. The group responded to a 1998 opinion piece dealing with mass spectrometry in trace analysis (Bethem, R. A.; Boyd, R. K. J. Am. Soc. Mass Spectrom. 1998, 9, 643-648) which proposed that the concept of fitness for purpose addresses the needs of a wide range of analytical problems. There is a need to define fitness for purpose within the current context of mass spectrometry and to recommend processes for developing and evaluating methods according to suitability for a particular purpose. The key element in our proposal is for the interested parties to define in advance the acceptable degree of measurement uncertainty and the desired degree of identification confidence. These choices can serve as guideposts during method development and targets for retrospective evaluation of methods. A series of more detailed recommendations are derived from basic principles and also from reviews of current practice. This report highlights some areas where consensus is evident, but also revealed the need for further work in other areas. The recommendations are aimed primarily for the laboratory analyst but we hope they will be accessible to the non-scientist as well. Our goal was to provide a framework that can support informed decisions and foster discussion of the issues, because ultimately it is the responsibility of the analyst to make choices, provide supporting data, and interpret results according to scientific principles and qualified judgment.