Sample preparation solid samples

Sample Preparation. Solid samples were finely powdered and dusted onto mylar tape. In order to minimize thickness effects some model compound samples were diluted with boron nitride. Liquid samples... 

For on-bead analysis vibrational spectroscopy (IR-spectroscopy) can be employed attenuated total reflection is a method allowing fast and nondestructive on-bead analysis of small samples (single bead analysis) without significant sample preparation. Solid phase NMR is the method of choice if complex structural analysis is intended on the support. Spatially resolved analysis on the resin is possible with microscopic techniques. 

For the determination of Pb, Zn and Mn in coal samples with solid sampling GF-AAS, calibration curves were prepared either from three appropriate NIST coal SRMs or solution standards. Identical results were obtained for Pb and Zn, while only solid SRMs gave correct results for Mn (Ah et al. 1989). 

Principles and Characteristics Solid-phase microextraction (SPME) is a patented microscale adsorp-tion/desorption technique developed by Pawliszyn et al. [525-531], which represents a recent development in sample preparation and sample concentration. In SPME analytes partition from a sample into a polymeric stationary phase that is thin-coated on a fused-silica rod (typically 1 cm x 100 p,m). Several configurations of SPME have been proposed including fibre, tubing, stirrer/fan, etc. SPME was introduced as a solvent-free sample preparation technique for GC. 

Sample Preparation Liquid Samples, Extracts, and Solutions of Solids... 

An excellent review of modern sorptive sampling techniques that could be considered for the enrichment of volatiles from mammalian secretions appeared recently [10]. To be on the safe side, more than one sample preparation and sample enrichment method should be used to analyze mammalian secretions. If GC and GC-MS analyses are employed, the results obtained with split/split-less, on-column, SPME and solventless (solid) sample introduction methods [11,12] should be compared. 

There are several techniques to prepare solid samples for IR analysis solid KBr pellets, melts, solutions, and mulls. While analyzing chemicals related to the CWC, introduction of additional absorbance bands in the spectra should be avoided. Therefore, the last two methods should not be used if other methods are available, since they always have peaks present because of solvent or oil. 

Conversion of a solid matrix into a liquid matrix involves the decomposition of the sample. One of the major problems in preparing solid samples for trace element analysis is the potential risk of contamination. Contamination can arise from several sources the grade of reagents used the vessels used for digestion and the subsequent dilution of the sample and human involvement. 

Sample preparation. Solid phase extraction on C-18 column, elution with 0.1% triethyl-amine in methanol. 

Name GsIStiPI Sample preparation Solid film, sodium chloride cell... 

Name Hydroxypropyl methyl cellulose phthalate Sample preparation Solid film, potassium bromide disk... 

Infrared Sample Preparation Liquid Samples Solid Samples... 

Raman spectroscopy is a nondestructive tool and requires little or no sample preparation. A sample may be analyzed in solid or powder form or in an aqueous solution and placed in glass containers such as an NMR tube, GC vial, test tube, light-path cell, or glass bottle. Aside from structure elucidation and functional group analysis, FT-Raman may be used for quantitative determination of polymorphs in a preformulation study. 

After expression and purification, protein samples are often initially available as lyophilized solids, in which the proteins are correctly folded but in an amorphous arrangement with an isotropic distribution of orientations. This form of the protein may be used for NMR studies but the lack of water can significantly affect the strucmres of the individual protein molecules. One simple way to overcome this is to rehydrate the sample with small amounts of water." The effect can be quite significant, as illustrated in Fig. 2 for a sample of the 76-residue protein ubiquitin. Flash freezing offers the opportunity of preparing solid samples of proteins in which the solution-state structure is largely preserved." " ... 

To prepare solid samples for analysis, information about the solubility of the analyte must be collected. The solubility of a solute is the concentration of the solute when it is at equilibrium with the solid substance, that is, the solution is saturated. For the preparation of a solid drug substance or product, the final drug concentration should be considerably less than the drug s solubility, to assure reliable recovery from day to day. 

Sample preparation. Solid particles and any substances which may be strongly adsorbed on the gel should be removed from the sample. The mass and concentration of the solutes are only important in so far as they affect the viscosity. If the sample viscosity is more than about twice that of the eluant, then this leads to poor resolution. The sample capacity, in terms of volume, is also important. 

Several factors must be considered for a particular biomacromolecular structure application that will affect the choice of spectroscopic methods. These include structural resolution necessary, chemical nature of biomacromolecule (protein, nucleic add, or glycan), amount/concentration of biopolymer available, sample preparation (solid or solution), solvents of interest, and desired structure information (secondary or tertiary structure). Structural resolution varies considerably for the various spectroscopic methods, with X-ray diffraction and NMR providing atomic resolution (high resolution) and ultraviolet (UV) absorption revealing merely information about the polarity of the chromophore s environment (low resolution). X-ray studies require crystals while NMR experiments prefer solutions in deuterated solvent. Solvent preferences can affect the choice of spectroscopic method as, for example, infrared (IR) encoimters strong interference from water, while optical rotatory dispersion (ORD) and circniar dichroism (CD) do not. Some of the commonly used spectroscopic methods in structural analyses of biomacromolecules will be discussed. 

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