Chromatography purity

Size exclusion chromatography Purity and oligomeric state... 

It is easy to find out which of these mechanisms is dominating by performing washing trials. One should check high-performance liquid chromatography purity of the wet filter cake, washed filter cake, mother liquor, and extremely washed filter cake with about 30% and then 70% of the API washed off. Data from these experiments will provide a clear picture of the mechanism of incorporation, which can suggest corrective measures. 

Chemicals. The o-xylene was an American Petroleum Institute standard sample, with stated impurities of 0.005 0.004 mole %. Other hydrocarbons were purified by gas chromatography. Purity was checked by gas chromatography on three columns of different selectivity except for 0.02% p-xylene in the m-xylene, no more than 0.002% of any impurity was detected. Samples were stored in vacuo. 

Since botulinum is a neurotoxin, large-scale production should meet biosafety level 3 containment and strict handling to avoid the possible human intoxication. Fermentation is carried out in complex medium containing casein hydrolysate, yeast extract, and glucose for 4 days. Then, botulinum toxin is precipitated with 3 N sulfuric acid followed by purification with DEAE-Sephadex column. Botulinum toxin was crystallized then and purified by additional steps using various affinity and size exclusion chromatography. Purity and quality were checked by animal testing. Production and purification steps vary with Clostridium strain used and botulinum type to be produced. ... 

Styrene monomers were purified by vacuum distillation. Dimer was fractionated using gel permeation chromatography (purity 99% 1% impurity was monomer and trimer). 

Reversed-phase high performance Hquid chromatography has come into use for estimating the purity of proteins and peptides as weU. However, before employed, a high performance Hquid chromatographic (hplc) profile of a given protein must be completely vaHdated (43). 

Gas chromatography or Hquid chromatography (23) are commonly used to measure impurities such as acetic, dichloroacetic, and trichloroacetic acids. High purity 99+% chloroacetic acid will contain less than 0.5% of either acetic acid or dichloroacetic acid. Other impurities that may be present in small amounts are water and hydrochloric acid. 

Specifications and Analytical Methods. The commercial material is specified as 97% minimum purity, determined by gas chromatography or acetylation. Moisture is specified at 0.05% maximum (Kad-Fischer titration). Formaldehyde content is determined by bisulfite titration. 

Specifications and Analytical Methods. Purity is determined by gas chromatography. Technical grade butenediol, specified at 95%... 

Specifications and Analytical Methods. Vinyl ethers are usually specified as 98% minimum purity, as determined by gas chromatography. The principal impurities are the parent alcohols, limited to 1.0% maximum for methyl vinyl ether and 0.5% maximum for ethyl vinyl ether. Water (by Kad-Fischer titration) ranges from 0.1% maximum for methyl vinyl ether to 0.5% maximum for ethyl vinyl ether. Acetaldehyde ranges from 0.1% maximum in ethyl vinyl ether to 0.5% maximum in butyl vinyl ether. 

RO—CF=CF2, are obtained by reaction with sodium salts of alcohols (26). An osone—TFE reaction is accompanied by chemiluminescence (27). Dimerization at 600°C gives perfluorocyclobutane, C Fg further heating gives hexafluoropropylene, CF2=CFCF2, and eventually perfluoroisobutylene, CF2=C(CF2)2 (28). Purity is deterrnined by both gas—Hquid and gas—soHd chromatography the in spectmm is complex and therefore of no value. 

Table 4 lists the specifications set by Du Pont, the largest U.S. producer of DMF (4). Water in DMF is deterrnined either by Kad Fischer titration or by gas chromatography. The chromatographic method is more rehable at lower levels of water (<500 ppm) (4). DMF purity is deterrnined by gc. For specialized laboratory appHcations, conductivity measurements have been used as an indication of purity (27). DMF in water can be measured by refractive index, hydrolysis to DMA followed by titration of the Hberated amine, or, most conveniendy, by infrared analysis. A band at 1087 cm is used for the ir analysis. 

Large quantities of butane are shipped under contract standards rather than under national or worldwide specifications. Most of the petrochemical feedstock materials are sold at purity specifications of 95—99.5 mol %. Butane and butane—petroleum mixtures intended for fuel use are sold worldwide under specifications defined by the Gas Processors Association, and the specifications and test methods have been pubHshed (28). Butanes may be readily detected by gas chromatography. Butanes commonly are stored in caverns (29) or refrigerated tanks. 

Analytical and Test Methods. o-Nitrotoluene can be analyzed for purity and isomer content by infrared spectroscopy with an accuracy of about 1%. -Nitrotoluene content can be estimated by the decomposition of the isomeric toluene diazonium chlorides because the ortho and meta isomers decompose more readily than the para isomer. A colorimetric method for determining the content of the various isomers is based on the color which forms when the mononitrotoluenes are dissolved in sulfuric acid (45). From the absorption of the sulfuric acid solution at 436 and 305 nm, the ortho and para isomer content can be deterrnined, and the meta isomer can be obtained by difference. However, this and other colorimetric methods are subject to possible interferences from other aromatic nitro compounds. A titrimetric method, based on the reduction of the nitro group with titanium(III) sulfate or chloride, can be used to determine mononitrotoluenes (32). Chromatographic methods, eg, gas chromatography or high pressure Hquid chromatography, are well suited for the deterrnination of mononitrotoluenes as well as its individual isomers. Freezing points are used commonly as indicators of purity of the various isomers. 

Optically Active PO. The synthesis of optically pure PO has been accompHshed by microbial asymmetric reduction of chloroacetone [78-95-5] (90). (3)-2-Meth5loxirane [16088-62-3] (PO) can be prepared in 90% optical purity from ethyl (3)-lactate in 44% overall yield (91). This method gives good optical purity from inexpensive reagents without the need for chromatography or a fermentation step. (3)-PO is available from Aldrich Chemical Company, having a specific rotation [0 ] ° 7.2 (c = 1, CHCl ). 

Instmmental methods of analysis provide information about the specific composition and purity of the amines. QuaUtative information about the identity of the product (functional groups present) and quantitative analysis (amount of various components such as nitrile, amide, acid, and deterruination of unsaturation) can be obtained by infrared analysis. Gas chromatography (gc), with a Hquid phase of either Apiezon grease or Carbowax, and high performance Hquid chromatography (hplc), using siHca columns and solvent systems such as isooctane, methyl tert-huty ether, tetrahydrofuran, and methanol, are used for quantitative analysis of fatty amine mixtures. Nuclear magnetic resonance spectroscopy (nmr), both proton ( H) and carbon-13 ( C), which can be used for quaHtative and quantitative analysis, is an important method used to analyze fatty amines (8,81). 

Gas Chromatography (gc). A principal advantage of gas chromatography has been the faciUty with which it can be combined with mass spectrometry for amino acid identification and confirmation of purity. The gc-mass spectrometry combination offers the advantage of obtaining stmctural information rather than the identification by retention time in hplc. 

Specifications and Analytical Methods. The purity of 2-pyrrohdinone is determined by gas chromatography and is specified as 98.5 wt % minimum. Maximum moisture content is specified as 0.5 wt %. Typical purities are much higher than specification. 

A number of processes have been devised for purifying thionyl chloride. A recommended laboratory method involves distillation from quinoline and boiled linseed oil. Commercial processes involve adding various high boiling olefins such as styrene (qv) to react with the sulfur chlorides to form adducts that remain in the distillation residue when the thionyl chloride is redistilled (179). Alternatively, sulfur can be fed into the top of the distillation column to react with the sulfur dichloride (180). Commercial thionyl chloride has a purity of 98—99.6% minimum, having sulfur dioxide, sulfur chlorides, and sulfuryl chloride as possible impurities. These can be determined by gas chromatography (181). 

Purity of toluene samples as well as the number, concentration, and identity of other components can be readily determined using standard gas chromatography techniques (40—42). Toluene content of high purity samples can also be accurately measured by freezing point, as outlined in ASTM D1016. Toluene exhibits characteristic uv, it, nmr, and mass spectra, which are useful in many specific control and analytical problems (2,43—45). 

With the exception of gasoHne grade /-butyl alcohol (GTBA), the butanols are generally marketed in bulk in the pure isomeric form. ASTM specifications (29) for n-, iso- and j -butyl alcohol are given in Table 3. Butanol specification purity is routinely obtained by gas chromatography (30). 

The detection and determination of traces of cobalt is of concern in such diverse areas as soflds, plants, fertilizers (qv), stainless and other steels for nuclear energy equipment (see Steel), high purity fissile materials (U, Th), refractory metals (Ta, Nb, Mo, and W), and semiconductors (qv). Useful techniques are spectrophotometry, polarography, emission spectrography, flame photometry, x-ray fluorescence, activation analysis, tracers, and mass spectrography, chromatography, and ion exchange (19) (see Analytical TffiTHODS Spectroscopy, optical Trace and residue analysis). 

Specifications, Analysis, and Toxicity. Dicyandiamide is identified quaHtatively by paper chromatography and quantitatively by ultraviolet spectrometry of the chromatogram. More commonly, total nitrogen analysis is used as a purity control or the dicyandiamide is converted by hydrolysis to guanylurea, which is determined gravimetrically as the nickel salt (50). Methods based on the precipitation of silver dicyandiamide picrate are sometimes used (51). Dicyandiamide can also be titrated with tetrabutylammonium hydroxide ia pyridine solution. Table 4 gives a typical analysis of a commercial sample. Dicyandiamide is essentially nontoxic. It may, however, cause dermatitis. 

Cyclohexanone purity is most readily deteanined by gas-Hquid chromatography over DC-710 or carbowax 20M-on-chromosorb. Impurities such as cyclohexane, ben2ene, cyclohexanol, and phenol do not interfere. In the absence of other carbonyl compounds cyclohexanone may be deterrnined by treatment with hydroxylamine hydrochloride, which forms the oxime, as follows ... 

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