Xterra

A good starting point for LC-MS method development is a 50 x 2.1 mm Xterra MS Qg column (3.5 pm) injection volume 5 pL mobile phase H2O/ACN 90/10 to 10/90 v/v 250pLrnin 1 gradient 50 °C. Generic protocols and smart automated (or zero) method development is coming within reach [559]. 

These three polymeric HALS stabilisers can be detected and positively identified in extracts from polyolefins using an Agilent Ion-trap instrument with positive APCI. Figure 34 shows a chromatogram for a 5-ppm standard of Tinuvin 622 in tetrahydrofuran (THF) and the peak mass spectrum (Figure 35). Similar data for Chimassorb 944 in THF are shown in Figures 36 and 37, respectively. A Waters Xterra C8 150 x 2.00 mm 3 pm 125A column at 60°C with the mobile phase of isopropanol +700 pl/1 hexylamine was employed. 

The use of high flow and fast gradient HPLC has gained a lot of popularity because of the ability to reduce LC/MS/MS cycle times during bioanalysis. In the case of fast gradient HPLC, peak shapes were improved and method development times were minimized, especially when multiple analytes with diverse functionalities had to be separated. Flows as high as 1.5 to 2 mL/min were achieved on a 2.1 x 30 mm Xterra C18 column.7 Details are discussed in a recent review.8... 

An SPE cartridge can be used multiple times, especially after the samples are pretreated with protein precipitation. Bourgogne et al. (2005) quantitated talinolol, a p -adrenoceptor antagonist used to treat arterial hypertension and coronary heart disease, in human plasma. The sample was first precipitated with perchloric acid and the supernatant was injected directly. An Xterra MS analytical column (50 x 4.6 mm, 3.5 [m, Waters) with a C18 recolumn filter (4x2 mm, 3.5 /.mi, Phenomenex) and a C8 EC cartridge were chosen. The cycle time was 4.8 min and linear range was 2.5 to 200 ng/mL. Protein precipitation allowed the SPE cartridge to be used for more than 90 injections. 

Because the instability of the N-oxide metabolite, which was subjected to decomposition during sample preparation (solvent evaporation during offline SPE), online SPE LC/MS became the method of choice for the application. Hsieh et al. (2004) built a system with two TFC cartridges and one analytical column, and another system with two TFC cartridges and two analytical columns for GLP quantitative bioanalysis of drug candidates. A Turbo C18 (50 x 1.0 mm, 5 /.mi, Cohesive Technologies), an Xterra MS C18 (30 x 2.0 mm, 2.5 /mi), and a guard column were used. Protein precipitation preceded injection. The cycle times for the two systems were 0.8 and 0.4 min. 

Gritti, F. and Guiochon, G, Effect of the pH, the concentration and the nature of the buffer on the adsorption mechanism of an ionic compound in reversed-phase liquid chromatography, ii. Analytical and overload band profiles on Symmetry-C-18 and Xterra-C-18, J. Chromatogr. A, 1041, 63, 2004. 

FIGURE 6.3 Plot of column efficiency against sample mass for three neutral compounds (3-phenylpropanol, caffeine, phenol), and three charged compounds (propranolol, nortriptyline, 2-NSA [2-naphthalenesulfonic acid]) on XTerra MS (15 x 0.46 cm, 3.5 pm particles). Mobile phase acetonitrile-formic acid (overall concentration 0.02 M) pH 2.7 (28 72, v/v) except for caffeine (12.5 77.5, v/v). Flow rate 1 mL min . Column temperature 30°C. Injection volume 5 pL. 

Column XTerra MS (pyridine) 3.5 p,m, 15 x 0.46 cm ID. Mobile phase acetonitrile buffer 28-72 (v/v). The calculations of ionic strength ignore the effect of the organic solvent. 

Saturation Capacities in mg on Primesep 100, Primesep 200, and XTerra RP18 Columns of the Same Dimensions (15 cm x 0.46 cm, 5 (cm Particle Size)... 

Fornal et al. [75] determined selectivity differences for bases in RP-HPLC under high pH conditions. They used quantitative structure retention relationships (QSRR) to model retention behavior. They reported that the stability of the columns they used (Waters XTerra MS, Zorbax Extend, Thermo BetaBasic) was limited with... 

FIGURE 9 Moderately rapid gradient separation. Column XTerra MS C, IS, 4.6x 20mm 3.5p.m. Gradient 0 to 100% B over 4min,A 0.1% formic acid in water, B 0.1% formic acid in acetonitrile. Flow rate 3.0mL/min. Temperature 30°C. Detection UV at 254 nm. Instrument Alliance 2795 with 996 photodiode array detector. Compounds (I) acetanilide, (2) triamcinolone, (3) hydrocortisone, (4) 2-amino-7-chloro-5-oxo-5H-[l]benzopyrano[2,3-b]pyridine-3-carbonitrile, (5) 6a-methyl-17a-hydroxyprogesterone, (6) 3-aminofluoranthene, (7) 2-bromofluorene, (8) perylene, (9) naphtho(2,3-a)pyrene. 

Primary screens were performed in duplicate on mixtures of 80 compounds (1 pM per compound, 5 pM protein), where samples in each mixture were orthogonally pooled so that no two compounds that are in one well are also together in another well. Primary hits were achieved when the same compound in two wells were observed. The GPC spin-column eluates were partially resolved using a reversed-phase C18 HPLC column (Waters Xterra 2.1 x 20.0 mm) with a 1-min ballistic gradient and total cycle time of 2 min. The HPLC eluates were analyzed with a Micromass eight-way MUX interfaced to an LCT Tof ESI-MS system. Achieved throughput was 100 000 compounds per day. 

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