Common Mode Analysis case studies

For example, common mode failures and the need for additional layers of protection have not been addressed thus far in this Case Study. The Markov Analysis shows the various states and transitions between diem. In particular, the significance of unrevealed failures in backup systems is brought to the fore. 

HPLC analysis of taxanes is achieved almost exclusively in reversed phase mode on various stationary phases. The normal-phase HPLC mode has been applied in very limited cases and resulted in broad peaks and long analysis times (retention times of 45 min for paclitaxel and 38 min for cephalomannine). The namre of the sample is the main criterion for the choice of the stationary phase. Analysis of plant material is performed mostly on phenyl, biphenyl, and pentafluorophenyl materials, but silica-based cyano, Cig, and Cg materials have been used as well. C18 phases are the most common material utilized in pharmacokinetic studies. Mobile phases typically consist of mixtures of methanol, acetonitrile, and water or buffer (mostly ammonium acetate). Detection is performed by UV, mostly in the low region of 225 -230 nm. Taxanes give similar UV spectra with a minimum at 210-215 nm and a maximum at 225-232 nm. Therefore, detection is performed, preferably at 227-228 nm. Dual/multiple UV detection is performed in both low and upper regions, e.g. 227 and 273 nm 230 and 280 nm 227, 254, and 270 nm, etc. (Fig. 2). 

GC-MS has been the technique most commonly implicated in the determination of estrogens in environmental samples. Both conventional MS and ion trap (IT)-MS detection have been accomplished in the El mode at 70 eV, usually in the selected ion monitoring (SIM) mode, and, in most cases, after sample derivat-ization, while the use of negative (N)CI has seldom been reported. The sensitivity of GC-MS-MS was reported to be in the range 20 pg pi (limit of quantification). A recent study has also discussed the possibilities of high-resolution (HR)MS for analysis of steroid sex hormones in environmental samples, showing that, with 20 000 resolution, lOpg of ethynyl estradiol can be detected. This amount corresponds to a detection limit of 1 ppt if the ethynyl estradiol is in 11 of water (concentrated into a 0.1 ml extract, followed by injection of 1 pi). 

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