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Figure 16.5 Isolation of albuterol from human plasma by means of solid-phase extraction (SPE).. RAM are most often selected for the analysis of low-molecular-weight drugs, their impurities, and metabolites [50–52]. Dual-mode porous packings are used in the most popular RAM columns.. These packings are used typically for the analysis of drugs in blood, because proteins present in these samples will...
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organic solvents requires indirect heating via the placement of a microwave-absorbing device in the extraction vessel. These devices are usually rods or a powder of a microwave-absorbing material such as carbon black coated with an inert polymeric substance (e.g., PTFE) that will not contaminate the sample. Multiple samples can be simultaneously processed in a microwave oven, so the sample throughput...
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Bland, Proceedings of the 3rd Annual International Symposium on Sample Prepara- tion and Isolation using Bonded Silicas, Analytichem International, Harbor City, CA, 1986, pp. 17.1 INTRODUCTION, 810 Quick Fix, 809. 17.2 PREVENTION OF PROBLEMS System Performance Tests Periodic Maintenance System-Suitability Testing Historical Records Tips and Techniques, 814. 17.3 PROBLEM-ISOLATION STRATEGIES Divide and Conquer, 819. 17.3.2 Easy versus Powerful, 820. 17.3.3...
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In our experience, this will fix leaky check valves most of the time, presumably by removing unwanted contaminants from the ball and/or seat of the seal. See Section 17.4.2.2 for additional discussion on the possible causes of and corrections for check-valve sticking.. 17.2.5.5 Leak Detection. Drips, puddles, and leak alarms usually make location of the leak simple. 17.2.5.6 Repairing Fitting...
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Figure 17.2 Schematic of low-pressure needle-seal. Failure of the injection rotor-seal can result in leaks at the injection valve. The rotor typically is made of a hard polymer, such as PEEK, Vespel, or one of the fluoropolymers, and contains tiny passages that connect the fluid passages in the stator. The stator may consist of the stainless-steel valve body, or it...
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17.4.3.5 Temperature Problems. A 1 ◦ C increase in column temperature will normally decrease retention by 1–2% (Section 2.3.2.2), so a method that is operated without column-temperature control will be subject to changes in retention as the temperature of the laboratory changes during the day. 17.4.3.6 Retention-Problem Symptoms. Re-installation of the previous column should confirm this. Legacy methods may require...
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isolation of the HPLC system from the electrical circuit, as well as pump and detector troubleshooting, could not solve the problem. Rather, movement of the system away from its original location reduced the frequency of the noise, and with sufficient distance eliminated it. An example of this is shown in Figure 17.11a for a gradient of 5–80% ACN-phosphate buffer (pH-7)...
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Figure 17.22 Separation of tipredane epimers. In Figure 17.22a, the pure S-epimer was injected, and peaks for both the R- and S-epimers are observed in the chromatogram (i..e, reaction of S-epimer to R). The injection of the pure R-epimer (Fig. 17.22b) shows a similar, but reduced conversion to the alternate epimer. When the column was changed to Resolve C 18...
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Leaks (Section 17.4.1): Symptoms and Sources. Location Sub-location/Symptom Possible Source Solution Pre-pump. Fitting Loose fitting Tighten or replace. Loose or damaged valve. Tighten valve or replace manifold. Pump Fittings Loose or damaged Tighten or replace. Tighten or replace. Stainless steel Loose or contaminated. clean or replace. PEEK Loose or. Fittings Loose or damaged See fittings adjustments, Sections Low-pressure needle. Worn...
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Degas mobile phase. clean or replace check valve, replace pump seal. Clean or replace check valve, replace pump seal. Mobile-phase solvents are of primary concern, because their properties must often fall within narrow limits for acceptable performance. However, these same properties also influence the choice of the sample-injection solvent and solvents used for sample preparation. Table I.1 lists several solvent...
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II.1 SEQUENCE OF OPERATIONS. combine the buffer ingredients with water to obtain the aqueous buffer (solution A). confirm or adjust the pH of solution A with a pH meter. combine a given volume (e.g., 200 mL) of organic buffer (solution B) with a given volume (e.g., 800 mL) of solution A from step 2 to obtain the final mobile phase...
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TỔNG HỢP VÀ NGHIÊN CỨU HÌNH THÁI, TÍNH CHẤT CỦA LỚP PHỦ PbO 2 KẾT TỦA ĐIỆN HÓA TRÊN NỀN THÉP MỀM VÀ KHẢ NĂNG ỨNG DỤNG LÀM ĐIỆN CỰC TRONG PIN CHÌ DỰ TRỮ. Điện cực trên cơ sở PbO 2 /vật liệu nền được ứng dụng trong tổng hợp điện hóa [1], oxi hóa các hợp chất ô...
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Brillouin–Wigner perturbation theory 556 Brueckner function 526. diamagnetic spin–orbit contribution 669 digonal hybridization 408. direct spin–spin interaction 669 dispersion energy 694. “drain-pipe” of reaction 772 DRC 768. 1080 Subject Index exchange–correlation energy 586. General Hartree–Fock method (GHF) 341. Hamiltonian, clamped nuclei 223 Hamiltonian of reaction path 784. Hartree–Fock method, general (GHF) 341 Hartree–Fock method, restricted (RHF). Hartree–Fock method, Unrestricted (UHF)...
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No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means electronic, mechanical, photocopying, recording or otherwise without the prior written permission of the publisher. 2.1 Symmetry of the Hamiltonian and its consequences. 2.1.2 Invariance with respect to translation. 2.1.3 Invariance with respect to rotation. 2.1.5 Invariance of the...
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6.12.1 Conical intersection. 6.12.2 Berry phase. 6.13.2 “Russian dolls. 8.10.1 Valence Shell Electron Pair Repulsion (VSEPR. 454 9.10 Solid state quantum chemistry. 9.10.1 Why do some bands go up. 9.10.2 Why do some bands go down. 9.10.3 Why do some bands stay constant. 9.12.1 Fock matrix corrections. 9.12.2 Total energy corrections. 10.1 Correlation cusp condition. 10.2 The Hylleraas function. 10.3...
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hold infinity in the palm of your hand and eternity in an hour. The apple looks quite different when lit by full sunlight, or when placed in the shade.. The same?. On the other hand, imagine how incredibly complicated the chemistry of friendship is.. Any model relies on our perception of reality (on the appropriate scale of masses and time)...
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It is suggested that the reader start with the following.. A study of the TREE diagram.. In this section readers are made aware of their current position on the TREE diagram. In this way, they know the relationship of the current chapter to other chapters, what chapters they are expected to have covered already, and the re- maining chapters for...
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this simple qualitative picture from classical theory – something had to be done. On 14 December 1900, the generally accepted date for the birth of quantum theory, Planck presented his theoretical results for the black body treated as an ensemble of harmonic oscillators. proportional to the frequency ν of vibrations of a single oscillator of the black body.. It is...
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wave function. The state of the system is described by the wave function = (x t), which depends on the coordinate of particle x at time t. (x t)(x t) dx = (x t) 2 dx (1.1) gives the probability that at time t the x coordinate of the particle lies in the small interval [ x x + dx...
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The spin quantum number s characteristic of the type of particle 37 (often called simply its spin), can be written as: s = n 2 , where n may be zero or a natural number (“an integer or half-integer” number). an integer s (e.g., s = 1 for deuteron, photon. The magnetic 39 spin quantum number m s quantizes the...