Tandem mass spectrometry testing

Figure 5.65 LC-UV and LC-MS-MS (multiple-reaction monitoring (MRM)) traces from the analysis of a enzymatically digested solution of 100 p,g salmon testes DNA (for nomenclature, see text). Reprinted by permission of Elsevier Science from Comparison of negative- and positive-ion electrospray tandem mass spectrometry for the liquid chromatography-tandem mass spectrometry analysis of oxidized deoxynucleosides , by Hua, Y., Wainhaus, S. B., Yang, Y., Shen, L., Xiong, Y., Xu, X., Zhang, F., Bolton, J. L. and van Breemen, R. B., Journal of the American Society for Mass Spectrometry, Vol. 12, pp. 80-87, Copyright 2000 by the American Society for Mass Spectrometry.

On the other hand, if only specific GC detectors, e.g. the electron capture, nitrogen-phosphorus or flame photometric detectors, are tested, the argument of lack of GC method sensitivity is not acceptable. In most cases mass spectrometric detectors provide the sensitivity and selectivity needed. Unfortunately, tandem mass spectrometry (MS/MS) or MS" detectors for GC are still not widely used in official laboratories, and therefore these techniques are not always accepted for enforcement methods. 

As analytical and bioanalytical methods must be validated before using them for routine sample analysis and after changing method parameters (see Chapter 8), instruments such as liquid chromatography coupled with mass spectrometry (LC-MS) or tandem mass spectrometry (LC-MS/MS), which are utilized to perform the analysis, should be calibrated and qualified. In addition, an instrument s performance should be tested for suitability prior to use on practically a day-to-day basis. 

Stock standard solutions weigh out accurately about 5-10 mg AdoMet (Sigma A7007) and AdoHcy (Sigma A9384) and dissolve in 1 ml of 1 mmol/1 HC1. These can be stored at -20°C for at least 2 years. Sonication may be needed to ensure complete dissolution. Note that AdoMet can break down into AdoHcy and this can be tested by HPLC with either ultraviolet or tandem mass spectrometry detection. 

Riediker, S., J.M. Diserens, and R.H. Stadler. 2001. Analysis of P-lactam antibiotics in incurred raw milk by rapid test methods and liquid chromatography coupled with electrospray ionization tandem mass spectrometry. J. Agric. Food Chem. 49 4171—4176. 

Eichhorst JC, Etter ML, Rousseaux N, Lehotay DC (2009) Drugs of abuse testing by tandem mass spectrometry a rapid, simple method to replace immunoassays. Clin Biochem 42(15) 1531—1542. doi S0009-9120(09)00322-l [pii] 10.1016/j.clinbiochem.2009.07.019... 

Wang Q, Zhao JG, Ballard JM, Shambor SM, Tsai EW, Ip D. 1999. Application of tandem mass spectrometry to FOSAMAX dissolution testing, presented at the Mass Frontier Symposium, Purdue University, October 10, 1999. 

S. McSheehy, P. Pohl, R. Fobinski, J. Szpunar, Investigation of arsenic speciation in oyster test reference material by multidimensional HPLC-ICP MS and electrospray tandem mass spectrometry (ES MS/MS), Analyst, 126 (2001), 1055D1062. 

There have been a few reports in the literature where hair has been analyzed directly for cocaine analytes, without analyte isolation. The earliest report was by Valente et al., who compared direct incubation of hair with the antiserum in an RIA test with acid, base, and methanol isolation. Although cocaine analytes were detected using this method, only 31% were recovered. In 1993, Kid well and Welch etal. noted that cocaine analytes could be observed in hair using tandem mass spectrometry (MS/MS) with no prior isolation. The washed samples were rapidly heated and the vaporized material analyzed. However, Welch et al. report that unambiguous results were only obtained when the hair samples were cryogenically powdered, which required more effort than preisolation of the analytes. 

D. H. Wilson, D. Sepe, and G. Barnes, Inter-laboratory differences in sirolimus results from six sirolimus testing centers using HPLC tandem mass spectrometry (LC/MS/MS), Clin. Chim. Acta 355 (2005), 211-213. 

The first procedure available for analysis of cyclosporine was an RIA developed by Sandoz Pharmaceuticals, the producer of cyclosporine. This immunoassay exhibits approximately 30% cross-reactivity with inactive metabolites, and the test is now considered obsolete. Nonisotopic immunoassays have been developed for whole-blood analysis. HPLC methods have been developed and are used now by many laboratories. A practical HPLC tandem mass spectrometry method is included on this book s accompanying Evolve site, found at http //evolve.elsevier.com/Tietz/ textbook/. 

Immunoassays may not be specific for the tested drug. Similar drugs may result in a positive test for example, pseu-doephedrine, present in cold medications, may produce a positive response in immunoassays designed to detect amphetamine and methamphetamine. Therefore it is imperative that positive screening tests be confirmed by an alternate, more definitive test. The most widely accepted method for drug confirmation is GC-MS. For further discussion of this technique, the reader is referred to Chapter 7. Liquid chromatography-tandem mass spectrometry is also used for rapid detection of drugs of abuse. 

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