Sample preparation purity

Acquisition of Spectra sample source sample purity sample preparation spectrometer type spectral resolution additional data possible (e.g., special sample conditions file format)... 

To compare devices of various brands, it is important to make sure that the supplied samples are of the same quality (same concentration, purity, sample preparation protocol). If the specifications require that GC-MS will be used for dosing, one must plan to supply a range of calibration solutions to check the linearity of the response in quantification. This calibration range must be produced from matrix... 

Investigated is the influence of the purity degree and concentration of sulfuric acid used for samples dissolution, on the analysis precision. Chosen are optimum conditions of sample preparation for the analysis excluding loss of Ce(IV) due to its interaction with organic impurities-reducers present in sulfuric acid. The photometric technique for Ce(IV) 0.002 - 0.1 % determination in alkaline and rare-earth borates is worked out. The technique based on o-tolidine oxidation by Ce(IV). The relative standard deviation is 0.02-0.1. 

Large quantities of solvents are employed for sample preparation, in particular, and these are then concentrated down to a few milliliters. So particularly high quality materials that are as free as possible from residual water and especially free from nonvolatile or not readily volatile impurities ought to be employed here such impurities are enriched on concentration and can lead to gross contamination. The same considerations also apply to preparative chromatography. Special solvents of particular purity are now available. 

In addition to instrumental improvements, various approaches have been used to improve the purity or geometry of sources of natural samples for gamma spectrometric measurement. For example, improvements in source preparation for " Th measurement in water and sediment samples by gamma spectrometry are discussed in Cochran and Masque (2003). It should be emphasized that one of the main advantages of gamma spectrometry is ease of use, since in many cases samples may be analyzed directly or with significantly reduced sample preparation compared to alpha, beta, or mass spectrometric techniques. 

Solid-phase microextraction eliminates many of the drawbacks of other sample preparation techniques, such as headspace, purge and trap, LLE, SPE, or simultaneous distillation/extraction techniques, including excessive preparation time or extravagant use of high-purity organic solvents. SPME ranks amongst other solvent-free sample preparation methods, notably SBSE (Section 3.5.3) and PT (Section 4.2.2) which essentially operate at room temperature, and DHS (Section 4.2.2),... 

In our laboratories, a cycle time of 90 sec can be achieved with a dilution factor of 1 25 for a given sample concentration, allowing the purity and identity control of two and a half 384-well microtiter plates per day. The online dilution eliminated an external step in the workflow and reduced the risks of decomposition of samples in the solvent mixture (weakly acidic aqueous solvent) required for analysis. Mao et al.23 described an example in which parallel sample preparation reduced steps in the workflow. They described a 2-min cycle time for the analysis of nefazodone and its metabolites for pharmacokinetic studies. The cycle time included complete solid phase extraction of neat samples, chromatographic separation, and LC/MS/MS analysis. The method was fully validated and proved rugged for high-throughput analysis of more than 5000 human plasma samples. Many papers published about this topic describe different methods of sample preparation. Hyotylainen24 has written a recent review. 

The next section describes the utilization of //PLC for different applications of interest in the pharmaceutical industry. The part discusses the instrumentation employed for these applications, followed by the results of detailed characterization studies. The next part focuses on particular applications, highlighting results from the high-throughput characterization of ADMET and physicochemical properties (e.g., solubility, purity, log P, drug release, etc.), separation-based assays (assay development and optimization, real-time enzyme kinetics, evaluation of substrate specificity, etc.), and sample preparation (e.g., high-throughput clean-up of complex samples prior to MS (FIA) analysis). 

Rare Earth metals. As mentioned in 6.3.1 rare earth metals and their alloys can be considered an especially representative example of the problems related to the preparation of high-purity samples, to the impurity role in defining the alloying behaviour, etc. These problems and several peculiar aspects of the rare earth metallurgy have been extensively underlined by Gschneidner (1980) who gave a description of several preparation and purification methods. These are briefly summarized below. 

Figure 3.5 Measurement of the chiral purity of commercially available Jacobson s catalyst using a cyclodextrin-based CSP. (a) Lower trace / ,/ -enantiomer product upper trace / ,/ -enantiomer product artificially enriched with S -enantiomer and (b) lower trace S. S -enantiomer product upper trace S. S -enantiomer product artificially enriched with / ,/ -enantiomer. (Conditions CYCLOBOND 1 2000RSP 25 cm X 0.46 cm i.d. mobile phase acetonitrile triethylamine glacial acetic acid [1000 0.5 2.5, v/v] flow rate 1 ml/min temperature ambient detection UV at 240 nm sample preparation 1 mg/ml in acetonitrile injection volume 10 fxl). Reprinted from [19], copyright 1998, with permission of Wiley-Liss, Inc., a subsidiary of John Wiley and Sons, Inc.

Figure 3.7 Determination of the enantiomeric purity of SB-214857 API using CD-modified CE. Distomer content measured at 0.06% by area. (Conditions plain fused silica capillary, 50 cm effective length, 57 cm total length, 75 pm i.d. buffer lithium phosphate [pH 3.0, 100 mM] containing 0.05% (w/v) hydroxyethy[cellulose and 1.5 mM dimethyl- 8-CD voltage 30 kV temperature 20°C detection UV at 200 nm sample preparation 0.2 mg/ml in water sample introduction 5 s at 35 mbar, capillary inlet at anode.)...

Mass spectrometry (MS) is widely used to ascertain the purity, total mass of the protein produced, and detect any covalent modifications (Cohen and Chait, 2001). Both electrospray ionization (ESI) and MALDI may be used although for intact proteins ESI has the advantage of being accurate to 1 Da. Using the simple protocol described in Protocol 2.11, the MS of whole protein samples can be readily automated without the need for sample preparation. This method has proved successful for the... 

When compared with conventional extraction and sample preparation methods, the developer claims that the MAP technology reduces production time, energy, solvent consumption, and waste production, while increasing extraction yields and product purity. 

Octadecyldimethylamine oxide (CieDAO) was a commercial sample from Onyx Chemical Company, Jersey City, N. J. (25% active). After evaporating the solvent in a rotary evaporator under reduced pressure, the crude product was recrystallised several times from ethyl acetate. The final product was dried and stored in vacuo over P2O5. Sodium octadecyl sulfate (SODS) was a sample prepared in this laboratory previously, and was recrystallised from ethanol before use. Sodium dodecyl sulfate (SDS) was obtained from Aldrich Chemical Company, and was of 98% purity. It was further purified by repeated crystallisation from ethanol followed by ether extraction. Benzene and methanol were gold-label reagent grade, purchased from Aldrich Chemical Company (Metuchen, N. J.). 

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