Chromatographic analysis performance

The minor (R,S) diastereomer is present in the crude reaction mixture to the extent of approximately 0.9% as determined by capillary gas-liquid chromatographic analysis performed on a Hewlett-Packard 5790A gas chromatograph equipped with a Hewlett-Packard 3390A integrator and HP-1 methylsilicone gum column (25 m x 0.2 mm x 0.33 pm film thickness). The checkers found that HPLC analysis (Zorbax SB-Phenyl column 25 cm x 4.6 mm, 40 60 MeCN/0.1% aqueous phorphoric acid, 1.5 mL/min, 250 nm detection) provided satisfactory resolution of the R,R- and R,S-diastereomers. The minor diastereomer is hardly discernible by 1H NMR (500 MHz) after purification by flash chromatography. 

The chromatographic analysis performed during electrolyses on Pt-Pb electrodes showed that sucrose is mainly transformed in I -MAS (major product) and 6-MAS. A very few amount of degradation products were detected. However, it must be noted that two reaction products remained unidentified. 

The identification of an unknown peak in a chromatographic analysis, performed by the Shimadzu SPD-M6A UV/Vis photodiode array detector, combined with data acquisition software Class MlOA, is presented in Fig. 3A-C. The spectrum file of the selected peak is compared against reference spectra in a user-built hbrary. Data processing through the mathematical approach mentioned above defines the best match. The numerical... 

The potential curves were found to be much more expressive. After an initial shift of potential by 200 mV or more to positive values a shift to the negative potentials, which is due to formation of p-amino-chlorobenzene, immediately commences. The potential of the catalyst reaches a maximum with the absorption of 3 moles of hydrogen and then decreases sharply. It is clear that this is due to acidification of the solution by the hydrochloric acid formed. Chromatographic analysis, performed at the point corresponding to maximum potential, demonstrated the presence of p-aminochlorobenzene in the solution and the absence of chloride ions. The selectivity of the process can thus be controlled directly by the potential of the catalyst. Similar possibilities were observed earlier in the hydrogenation of fats [3],... 

In current industrial practice gas chromatographic analysis (glc) is used for quahty control. The impurities, mainly a small amount of water (by Kad-Fischer) and some organic trace constituents (by glc), are deterrnined quantitatively, and the balance to 100% is taken as the acetone content. Compliance to specified ranges of individual impurities can also be assured by this analysis. The gas chromatographic method is accurately correlated to any other tests specified for the assay of acetone in the product. Contract specification tests are performed on product to be shipped. Typical wet methods for the deterrnination of acetone are acidimetry (49), titration of the Hberated hydrochloric acid after treating the acetone with hydroxylamine hydrochloride and iodimetry (50), titrating the excess of iodine after treating the acetone with iodine and base (iodoform reaction). 

Purity. Gas chromatographic analysis is performed utilizing a wide-bore capillary column (DB-1, 60 m x 0.32 mm ID x 1.0 //m film) and a flame ionization detector in an instmment such as a Hewlett-Packard 5890 gas chromatograph. A caUbration standard is used to determine response factors for all significant impurities, and external standard calculation techniques are used to estimate the impurity concentrations. AHyl chloride purity is deterrnined by difference. 

Time-Delay Compensation Time delays are a common occurrence in the process industries because of the presence of recycle loops, fluid-flow distance lags, and dead time in composition measurements resulting from use of chromatographic analysis. The presence of a time delay in a process severely hmits the performance of a conventional PID control system, reducing the stability margin of the closed-loop control system. Consequently, the controller gain must be reduced below that which could be used for a process without delay. Thus, the response of the closed-loop system will be sluggish compared to that of the system with no time delay. 

Chromatographs can perform a total composition analysis for a sample. It is possible but inconvenient to provide an analog input for each component. Furthermore, it is often desirable to capture other information, such as the time that the analysis was made (normally the time the sample was injected). 

E. Menziani, B. Tosi, A. Bonora, P. Reschiglian and G. Eodi, Automated multiple development high-performance thin-layer chromatographic analysis of natural phenolic compounds , 7. Chromatogr. 511 396-401 (1990). 

Gas chromatographic analysis was performed on a 2.2-m. 10% diethylene glycol succinate column at 80°. 

BAILEY R G, NURSTEN H E and MCDOWELL I (1994) Isolation and high-performance liqnid chromatographic analysis of thearubigin fractions from black tea , J Chromatogr A, 662, 101-2. 

Shack, D. and Reznik, H., High-performance hqnid chromatographic analysis of betax-anthins in Centrospermae (CaryophyUales), Ztschr. PflanzenphysioL, 94, 163, 1979. Gandla-Herrero, E., Escribano, 1., and Garcla-Carmona, F., Betaxanthins as pigments responsible for visible finorescence in flowers, Planta, 222, 586, 2005. 

Strack, D. and Reznik, H., High-performance liquid chromatographic analysis of betaxanthins in Centrospermae (Caryophyllales), Ztschr. Pflanzenphysiol, 94, 163, 1979. 

Goodall, I., Dermis, J. J., Parker, 1., and Sharman, M. (1995). Contribution of high performance liquid chromatographic analysis of carbohydrates to authenticity testing of honey. 

Kunitani, M. and Kresin, L., High-performance liquid chromatographic analysis of carbohydrate mass composition in glycoproteins, /. Chromatogr., 632, 19 1993. 

Principles and Characteristics Because of the limited selectivity of extraction, a chromatographic analysis is almost always needed. Recently, a fair amount of progress has been made regarding the front end of the total analysis procedure, namely the integration of sample preparation (this being the analytical bottleneck) and separation. The idea behind such systems is to perform sample extraction, cleanup and concentration as an integral part of the analysis in a closed system. Scheme 7.2 shows the main procedures related to sample preparation for chromatographic analysis. 

As another criterion of purity, the amino acid content of heparins should be determined. This is usually performed by ion-exchange88 or liquid89 chromatographic analysis of hydrolyzates. Reasonably pure heparin preparations contain < 1% of total amino acids, mostly L-serine and glycine. Heparin preparations should also be analyzed for residual solvents, and analytical (as well as biological) data be expressed on a dry basis. (Heparins equilibrated with atmospheric humidity contain up to 15%, or even more, of water.) Unless volatile materials are completely removed or accounted for, elemental analyses of heparin are meaningless. 

Nagels, L.J., Creten, W.L. (1985). Evaluation of the glassy carbon electrochemical detector selectivity in high-performance liquid chromatographic analysis of plant material. Anal. Chem. 57, 2706. 

Elevated temperature can also be a very effective way to increase column performance and reduce the second-dimension elution time range as retention is generally reduced at higher temperatures. This has been utilized by Carr and coworkers (Stoll et al., 2006, 2007) to perform very fast second-dimension elution time ranges, and it should be considered for faster chromatographic analysis in general. 

C. Mathe, G. Culioli, P. Archier, C. Vieillescazes, High performance liquid chromatographic analysis of triterpenoids in commercial frankincense, Chromatographia, 60, 493 499 (2004). 

One of the main problems of the pyrolysis technique is related to the low volatility of pyrolysis products arising from natural and some synthetic macromolecules. In fact, the polar acidic, alcoholic and aminic moieties are not really suitable for gas chromatographic analysis. Their poor volatility and their polarity cause a rather low reproducibility of the pyrograms, low sensitivity for specific compounds, and strong memory effects. Memory effects need to be borne in mind when the pyrolysis of polar molecules is performed. Polar pyolysis products may not be completely eluted by the gas chromatographic column, and... 

Forni E, Polesello A, Montefiori D and Maestrelli A. 1992. A high performance liquid chromatographic analysis of the pigments of blood-red prickly pear (Opuntia ficus-indica). J Chromatogr 593 177-183. 

When solvent extraction was performed, the procedure used by Dutka et al. [406] was followed with a slight modification 2 ml of concentrated hydrochloric acid and 5 ml of 20% (w/v) sodium chloride were added to each litre of water sample. The sample was extracted with vigorous mixing three times with 100 ml each of hexane for 30 min. The combined extract was washed with two 50 ml portions of acetonitrile (saturated with hexane) followed by two 50 ml portions of 70% ethanol. The hexane was then brought to dryness on a rotary evaporator under reduced pressure. The sample was re-dissolved in 100-200 pi of carbon disulfide, and 1-5 pi of the solution was used for gas chromatographic analysis. 

The methyl-[14C]-dimethyltin chloride was used to compare the performance of packed and megabore capillary columns in a gas chromatographic analysis for separating mixtures of a carbon-14 labelled trimethyllead chloride, tetramethyltin, dimethyltin dichloride and methyltin trichloride. The megabore column was able to separate all four methyltin compounds quickly, i.e., before the tetramethyltin decomposed into trimethyltin chloride and dimethyltin dichloride (equation 47), a reaction which did occur on the packed columns. Thus, the megabore column enabled the determination of the precise distribution of the various methyltin compounds in an environmental sample. The packed columns, on the other hand, could not separate dimethyltin dichloride and the methyltin trichloride and allowed significant decomposition of the tetramethyltin during the 15 minutes the analysis required. 

Viehauer S. et al., 1995. Evaluation and routine application of the novel restricted-access precolumn packing material Alkyl-Diol Silica Coupled-column high-performance liquid chromatographic analysis of the photoreactive drug 8-methoxypsoralen in plasma. J Chromatogr B 666 315. 

---