GC and MS Properties of β-Blockers as tert-Butyldimethylsilyl Derivatives and as Ethoxycarbonyl/Trimethylsilyl Derivatives

MASS SPECTROMETRIC FRAGMENTATION OF TRIMETHYLSILYL AND RELATED ALKYLSILYL DERIVATIVES

This review describes the mass spectral fragmentation of trimethylsilyl (TMS) and related alkylsilyl derivatives used for preparing samples for analysis, mainly by combined gas chromatography and mass spectrometry (GC/MS). The review is divided into three sections. The first section is concerned with the TMS derivatives themselves and describes fragmentation of derivatized alcohols, thiols, amines, ketones, carboxylic acids and bifunctional compounds such as hydroxy- and amino-acids, halo acids and hydroxy ethers. More complex compounds such as glycerides, sphingolipids, carbohydrates, organic phosphates, phosphonates, steroids, vitamin D, cannabinoids, and prostaglandins are discussed next. The second section describes intermolecular reactions of siliconium ions such as the TMS cation and the third section discusses other alkylsilyl derivatives. Among these latter compounds are di- and trialkyl-silyl derivatives, various substituted-alkyldimethylsilyl derivatives such as the tert-butyldimethylsilyl ethers, cyclic silyl derivatives, alkoxysilyl derivatives, and 3-pyridylmethyldimethylsilyl esters used for double bond location in fatty acid spectra. © 2019 Wiley Periodicals, Inc. Mass Spec Rev 0000:1-107, 2019.

Electrically enhanced microextraction for highly selective transport of three β-blocker drugs

Facilitated transport of three β-blocker drugs including atenolol (ATE), betaxolol (BET) and propranolol (PRO) was investigated under electrical field across a supported liquid membrane (SLM) using phosphoric acid derivatives as selective ion carriers, dissolved in 2-nitro phenyl octyl ether (NPOE). In the presence of di-(2-ethylhexyl) phosphate (DEHP) and tris-(2-ethylhexyl) phosphate (TEHP) in the membrane phase, the three β-blockers showed completely different transport behaviors which enabled highly selective separation of the drugs. Each β-blocker migrated from 3 mL of sample solutions, through a thin layer of specific organic solvent immobilized in the pores of a porous hollow fiber, and into a 15 μL acidic aqueous acceptor solution present inside the lumen of the fiber. The influences of fundamental parameters affecting the transport of target drugs including type of ion carrier for selective separation of each drug and its concentration in the membrane phase, extraction voltage, time of transport, pH of donor and acceptor phases, stirring speed of donor phase and salt effect were studied and optimized. After microextraction process, the extracts were analyzed by high-performance liquid chromatography with ultraviolet detection. Under optimal conditions, ATE was selectively extracted from different saliva samples with recovery of 37%, which corresponded to preconcentration factor of 74. A good linearity was achieved for calibration curve with a coefficient of determination higher than 0.997. Limits of detection and intra-day precision (n=3) were less than 2 μg L(-1) and 8.8%, respectively.