Calibration Compounds Research Articles

Modification of a packed column gas chromatograph/mass spectrometer

A packed-column gas-chromatograph/mass-spectrometer (GC/MS), Hewlett-Packard 5982, was modified to accommodate fused silica capillary columns. The original GC/MS interface and chemical-ionization sample-line in the ion-source were changed to allow the end of a fused silica capillary column to enter the ion-chamber directly. For chemical-ionization operation, the reagent gas was brought into the MS through the direct-insertion probe port. The calibration compound was introduced through the electron-impact sample-inlet, which simplified the operation. The modified system yields higher sensitivity and more efficient separation, as well as simpler operation, without sacrificing any original instrument functions.

High-performance size-exclusion chromatography of lignin and its derivatives

High-performance size-exclusion chromatography of different lignins was studied using styrene—divinylbenzene copolymer gel columns. Acetylated and silylated model compounds were compared with underivatized samples to see the effect of possible adsorption or intermolecular association on the chromatography. The results showed that these phenomena did not cause any major interference in the chromatographic system described here. Derivatization increased the average molecular weights of lignins by more than was calculated from the hydroxyl content. We believe that the derivatization changed the hydrodynamic volume of the molecules, so the calibration compounds should also be changed. Alternatively, this might reflect some kind of association between the non-polar groups in the lignin molecules. For this reason the average molecular weights of lignin cannot be calculated by subtracting the mass of derivative groups from the average molecular weight of derivatized samples. Polystyrene calibration was found unsuitable in the analysis of lignin derivatives. The lignin model compound calibration seemed to be promising.

Intercomparison of 11 mass spectrometers applied for quantitative organic analysis in Denmark

Eleven mass spectrometers all connected with a gas chromatograph were used for quantitative determination by the isotopic dilution technique. The purpose of the investigation was to compare the virtual performances of the instruments rather than the routines of the individual laboratories. Therefore, calibration compounds and samples were distributed to the participants. A satisfactory linearity but poor reproducibility was found.

Quaternary ammonium salts as calibration compounds for fast atom bombardment mass spectrometry

Quaternary ammonium salts as calibration compounds for fast atom bombardment mass spectrometry

Retention indices in reversed-phase liquid chromatography. Calibration of the system

A simple retention model based on interaction indices allows easy prediction of retention in reversed-phase liquid chromatography. The accuracy of prediction depends on the choice of calibration compounds necessary to characterize the relationship between the capacity ratio and the interaction index. The procedure used to evaluate a series of standards for calibration purposes is described. It is shown that, with a correct choice of calibration compounds, it is possible to predict retention under widely different conditions of solvent compositions — both different organic solvents and different concentrations. The described model is used to explain selectivity changes, including inversions in the elution order.

Peroxisomal fatty acid oxidation as detected by H2O2 production in intact perfused rat liver.

1. H2O2 formation associated with the metabolism of added fatty acids was quantitatively determined in isolated haemoglobin-free perfused rat liver (non-recirculating system) by two different methods. 2. Organ spectrophotometry of catalase Compound I [Sies & Chance (1970) FEBS Lett. 11, 172-176] was used to detect H2O2 formation (a) by steady-state titration with added hydrogen donor, methanol or (b) by comparison of fatty-acid responses with those of the calibration compound, urate. 3. In the use of the peroxidatic reaction of catalase, [14C]methanol was added as hydrogen donor at an optimal concentration of 1 mM in the presence of 0.2 mM-L-methionine, and 14CO2 production rates were determined. 4. Results obtained by the different methods were similar. 5. The yield of H2O2 formation, expressed as the rate of H2O2 formation in relation to the rate of fatty-acid supply, was less than 1.0 in all cases, indicating that, regardless of chain length, less than one acetyl unit was formed per mol of added fatty acid by the peroxisomal system. In particular, the standard substrate used with isolated peroxisomal preparations (C16:0 fatty acid) gave low yield (close to zero). Long-chain monounsaturated fatty acids exhibit a relatively high yield of H2O2 formation. 6. The hypolipidaemic agent bezafibrate led to slightly increased yields for most of the acids tested, but the yield with oleate was decreased to one-half the original yield. 7. It is concluded that in the intact isolated perfused rat liver the assayable capacity for peroxisomal beta-oxidation is used to only a minor degree. However, the observed rates of H2O2 production with fatty acids can account for a considerable share of the endogenous H2O2 production found in the intact animal.

The application of total hydrocarbon flame ionization detectors to the analysis of hydrocarbon mixtures from motor vehicles, with and without catalytic emission control

The successful application of total hydrocarbon analyzers to the analysis of hydrocarbon mixtures requires linear response with respect to a single calibration compound. Flame ionization detectors configured for total hydrocarbon analysis (premixed flames) do not respond in the same manner to all hydrocarbon species. A discussion of the source of the phenomena is presented.

Unification of rotary motion feedthroughs for ultrahigh vacuum evaporation systems: G A Shaumyan et al, Elektron Tekh Tekhnol Organiz Proizv, 5, 1970, 70–74 ( in Russian)

A packed-column gas-chromatograph/mass-spectrometer (GC/MS), Hewlett-Packard 5982, was modified to accommodate fused silica capillary columns. The original GC/MS interface and chemical-ionization sample-line in the ion-source were changed to allow the end of a fused silica capillary column to enter the ion-chamber directly. For chemical-ionization operation, the reagent gas was brought into the MS through the direct-insertion probe port. The calibration compound was introduced through the electron-impact sample-inlet, which simplified the operation. The modified system yields higher sensitivity and more efficient separation, as well as simpler operation, without sacrificing any original instrument functions.

Micro X-ray spectral investigation of Ti- and Ti-Ag to A-995 ceramic seals: E S Zhmud et al, Elektron Tekh Elektron SVCh, 11, 1970, 117–123 ( in Russian)

A packed-column gas-chromatograph/mass-spectrometer (GC/MS), Hewlett-Packard 5982, was modified to accommodate fused silica capillary columns. The original GC/MS interface and chemical-ionization sample-line in the ion-source were changed to allow the end of a fused silica capillary column to enter the ion-chamber directly. For chemical-ionization operation, the reagent gas was brought into the MS through the direct-insertion probe port. The calibration compound was introduced through the electron-impact sample-inlet, which simplified the operation. The modified system yields higher sensitivity and more efficient separation, as well as simpler operation, without sacrificing any original instrument functions.

Correction. Fluorescent Compounds for Calibration of Excitation and Emission Units of Spectrofluorometer

Correction. Fluorescent Compounds for Calibration of Excitation and Emission Units of Spectrofluorometer

Fluorescent Compounds for Calibration of Excitation and Emission Units of Spectrofluorometer.

Fluorescent Compounds for Calibration of Excitation and Emission Units of Spectrofluorometer.