kazakevich - hplc for pharmaceutical scientists (wiley, 2007)

... Applications of LC-NMR, 916 20.4 LC-MS-NMR (or LC-NMR-MS or LC-NMR/MS), 916 20.4.1 Introduction, 916 20.4.2 Modes of Operation for LC-MS-NMR, 917 20.4.3 Applications of LC-MS-NMR, 926 20.5 Conclusions, ... technologies in- cluding automated high performance liquid chromatography (HPLC) , fast HPLC, automated method development, HPLC- MS (mass spectrometry), HPLC- NMR (nuclear magnetic re...

Ngày tải lên: 03/04/2014, 12:19

... rates are applied. For example, optimum flow rate of 1.0mL/min may be employed for a 4.6-mm-i.d. column. A 2.1-mm-i.d. column has optimum flow rate of 0.2 mL/min. For LC/ESI-MS, ESI-MS is compatible ... excellent tools for structural characterization of complex molecules. A third type of MS/MS instruments is a hybrid of tandem-in-space and tandem-in-time devices, including the Q-trap (Q...

Ngày tải lên: 15/12/2013, 12:15

... atoms in a structure can provide additional information for struc- tural characterization, such as the differentiation between N- or S-oxide for- mation and hydroxylation in drug metabolism studies. ... calibration can provide an order-of-magnitude greater mass accuracy than external calibration for the FT-MS analysis. One example is the high-resolution ESI-FT-ICR MS analysis of a mixt...

Ngày tải lên: 15/12/2013, 12:15

... (Figure 8-2 ). [2]. TYPES OF METHODS 349 Figure 8-1 . Synthesis of TMP. (Reprinted from reference 1, with permission.) Impurity 1 and Impurity 2, were identified as 2,4-diamino- 5-( -4 -ethoxy- 3,5-dimethoxybenzyl) ... 2,4-diamino- 5-( -4 -ethoxy- 3,5-dimethoxybenzyl) pyrimidine and 2,4-diamino- 5-( 3-bromo-4, 5- dimethoxybenzyl) pyrimidine, respectively (structures shown in Fi...

Ngày tải lên: 15/12/2013, 12:15

... screening can be per- formed. For method column screening, generally columns with 10-cm or 5-cm × 3.0-mm i.d. could be used that are packed with 3- m particles. Implementa- tion of a column switcher ... the respective ana- lytical method that is applied to a real in-process sample or a dosage form for subsequent HPLC analysis. The analytical procedure must specify the manu- facturer,...

Ngày tải lên: 15/12/2013, 12:15

... shorter columns for gradient scouting experiments (5 cm × 4.6mm ) packed with 3- m columns or use a high- pressure system (max pressure 15,000 psi) with 10-cm × 2.1-mm, 1. 7- m parti- cles. Use 35–45°C ... ionized form or use a 25 mM ammonium hydroxide buffer (pH 10.5) or 25 mM N-methyl pyrrolidine buffer (pH 10.5) to analyze in its neutral form. Use a 10-cm × 3.0-mm column packed with...

Ngày tải lên: 15/12/2013, 12:15

... were conducted on a 1 5- × 4.6-mm, 3- m column. However, the pH scouting analysis could have been performed faster. A 5-cm × 4.6-mm column on a conventional low-pressure HPLC system could have been ... 5-cm or 10-cm × 2.1-mm column, packed with 1. 7- m particles, could have been used in conjunction with an ultrahigh-pressure HPLC system, allowing for further reduction of the anal...

Ngày tải lên: 15/12/2013, 12:15

... can Π Π rL rL r r 2 30 2 46 30 46 0 425 . . . . . -i.d.column -i.d.column -i.d.column 2 -i.d.column 2 == METHOD DEVELOPMENT APPROACHES 425 be performed for further structural elucidation of the impurities. Deuterated experiments can be performed ... synthetic by-product elucidation. Take, for example, the two compounds 5-aminoindazole and 1-aminoindan, both of which have an [M + H] + of 1...

Ngày tải lên: 15/12/2013, 12:15

... DEVELOPMENT Figure 8-6 4. Separation of synthetic tocopherols by reversed-phase HPLC (280 nm). (1) δ-tocopherol, (2) γ-tocopherol, (3) β-tocopherol, (4) α-tocopherol, (5) α-tocopheryl acetate. ... band dis- tortion of the peaks in the chromatogram. Columns packed with 5- m parti- cles typically use 2- m porosity inlet frits to contain the packing; for the 3- m particles, 0. 5-...

Ngày tải lên: 24/12/2013, 18:15

... interactions employed in normal-phase HPLC (see Chapter 5). 2. Dispersive forces are employed in reversed-phase HPLC (see Chapter 4). 3. Ionic forces are employed in ion-exchange HPLC (see Chapter 4, Section ... stronger interaction in reversed-phase HPLC) , which are insoluble in polar or aqueous solvents. Figure 1-5 demonstrates the application of normal-phase HPLC for the sep...

Ngày tải lên: 24/12/2013, 18:15