Addendum to "tentative method for the continuous analysis of total hydrocarbons in the atmosphere (flame ionization method)": flame ionization detector.
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Air Ionization↗
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Triacylglycerol analysis of potential margarine base stocks by high-performance liquid chromatography with atmospheric pressure chemical ionization mass spectrometry and flame ionization detection.
Several margarine base stock candidates have previously been prepared for the purpose of finding better, more oxidatively stable food components: high-saturate vegetable oils, randomized vegetable oils, vegetable oil-hard stock blends, and interesterified vegetable oil-hard stock blends. Here are reported the triacylglycerol compositions of these products, determined using reverse-phase high-performance liquid chromatography (HPLC) coupled with a flame ionization detector or a quadrupole mass spectrometer with an atmospheric pressure chemical ionization source. Triacylglycerol percent composition results for samples of known composition (randomized and interesterified samples) exhibited less average error by HPLC coupled with a quadrupole mass spectrometer with an atmospheric pressure chemical ionization source, after application of response factors, than the results by HPLC coupled with a flame ionization detector. The fatty acid compositions calculated from the mass spectrometric data exhibited less average error than the fatty acid compositions resulting from the flame ionization detector data. The average error of the fatty acid compositions by the mass spectrometer was lowest for interesterified blend samples, next lowest for randomized samples, then followed by high-saturated fatty acid oils, normal oils, and blends. Analysis of the vegetable oil-hard stock blends by mass spectrometer required special treatment for calculation of response factors.
Chromatography, High Pressure Liquid↗
Analysis of triacylglycerol positional isomers in food products as brominated derivatives by high-performance liquid chromatography coupled with a flame ionization detection.
Reversed-phase HPLC resolution and HPLC-flame ionization detection quantitation of model triacylglycerol positional isomer pairs (important in the study of food formulation lipids) after facile conversion to brominated derivatives is reported. The positional isomers in the triacylglycerol pairs were at least 98% resolved from each other during reversed-phase HPLC. Triacylglycerol quantitation obtained by HPLC-flame ionization detector was checked against standard positional isomer pairs known by mass. The flame ionization detection area percent gave absolute error range of 0.3-1.6% per triacylglycerol.
Bromine↗
Improved reproducibility and quantitative analysis of phospholipids by flame ionization detection.
Quantitative analysis of phospholipids by flame ionization was improved by careful application of samples with a Hamilton syringe and use of a sealed dual tank system. Chromarods developed more consistently with reproducible scanning times or RF values (coefficient of variation of 1%) and with sharper peaks if development was carried out in a sealed dual tank system. The Chromarods were placed in the inner tank, which was the standard ground glass topped tank furnished with the Iatroscan TH-10 system. This inner tank was placed inside a larger thin-layer chromatography tank which was sealed with silicone grease and the lid held in place with a lead brick. Both tanks were lined with absorbent paper and contained the same solvent system. Biological samples quantified with these procedures and measured in amounts between 1 and 30 micrograms had coefficients of variation between 0.2 and 6%. An efficient method of completely separating neutral lipids from phospholipids and allowing quantitative determination of cholesterol is described. Scanning times and RF values of various phospholipids are compared to determine the best separation of the major phospholipids found in 3T3-L1 and leukocyte membranes.
Cell Membrane↗
A simple screening method for plasma lipids by thin-layer chromatography with flame ionization detection.
Thin-layer chromatography was carried out on glass rods coated with Silica gel (chromarod) and the fractions were detected with a flame ionization detector (FID). This system was applied to the fractionation and screening of plasma lipids. As the relative response of the flame ionization detector depends on the nature of the lipids, correction factors had to be introduced. These correction factors were derived from comparison of the results of the thin-layer chromatography with flame ionization detection with those obtained by conventional chemical analysis of the same sample. The coefficients of variation of the lipid profiles were comparable for both techniques. The absolute lipid concentration for the various fractions obtained by combination of the concentration of the total lipids with the relative lipid profile, correlate very well with the values obtained by conventional chemical analysis of the various lipids.
Cholesterol↗
GLC analysis of hydrocortisone, triamcinolone acetonide, and desonide in culture media of mouse and human dermal fibroblasts using flame-ionization detection.
A quantitative GLC assay with flame-ionization detection capable of detecting nanogram quantities of hydrocortisone, triamcinolone acetonide, and desonide in biological fluids was developed. This assay consisted of two extractions of the glucocorticoids from 1 N sodium chloride-treated cell culture media into ethyl acetate and subsequent double derivatization with methoxyamine and N-trimethylsilylimidazole. The chemical structures of methoxime-trimethylsilyl derivatives were confirmed by GLC-mass spectrometry. The methoxime-trimethylsilyl derivatives were stable for 24 hr. The applicability of this assay was demonstrated by studies of the glucocorticoid levels in L-929 and human dermal fibroblasts cell culture media over prolonged incubation (0--96 hr).
Adult↗
Separation and determination of polyether carboxylic antibiotics from Streptomyces hygroscopicus NRRL B 1865 by thin-layer chromatography with flame ionization detection.
Thin-layer chromatography coupled with flame ionization detection was used to develop a method to separate and to determine simultaneously three polyether carboxylic ionophore antibiotics (abierixin, nigericin and grisorixin) produced by Streptomyces hygroscopicus NRRL B 1865. Various proportions of chloroform, methanol and formic acid (or acetic acid as a substitute for formic acid) were used in the developing solvent to determine changes in RF values of the antibiotics and to allow conditions for maximum resolution to be obtained. Development on Chromarods SII with chloroform-methanol-formic acid (97:4:0.6, v/v/v) gave satisfactory and reliable separations of the three polyether antibiotics. Under these conditions, the internal standard methyl desoxycholate was found to be suitable for their simultaneous determination in the lipid extracts of Streptomyces hygroscopicus NRRL B 1865.
Calibration↗
Separation and quantitation of molecular species of plant phosphatidylcholine by high-performance liquid chromatography with flame ionization detection.
A method is described for the direct quantitation of phosphatidylcholine molecular species by reverse phase high-performance liquid chromatography employing flame ionization detection. The method is shown to be applicable to plan phosphatidylcholine. The molecular species are separated with a C18 column eluted in an isocratic mode. Detection by a commercially available flame ionization detector overcomes the problems of detecting underivatized naturally occurring lipids using ultraviolet detectors, and allows direct and rapid mass determination of the resolved molecular species. Detection limits for quantitation are defined.
Chromatography, High Pressure Liquid↗
Determination of sodium dodecyl sulfate in hydrophilic ointments by thin-layer chromatography with flame ionization detection.
Thin-layer chromatography with flame ionization detection (TLC-FID) was compared with colorimetric and HPLC methods for measuring sodium dodecyl sulfate (SDS), an anionic surfactant, in hydrophilic ointments prepared according to the Japanese Pharmacopoeia, the United States Pharmacopoeia and British Pharmacopoeia. The TLC-FID method was found to be better than the colorimetric method in terms of simplicity and accuracy in the determination of SDS in hydrophilic ointments. Quantification of a small amount of SDS was not possible using HPLC with refractive index detection due to the low sensitivity of the detector.
Chemical Phenomena↗
Quantitative gas-chromatographic flame-ionization method for chloramphenicol in human serum.
We describe a flame-ionization gas-chromatographic procedure for determination of the potentially toxic antibiotic, chloramphenical, in serum. The serum (500 mul) is extracted into ethyl acetate and nonpolar impurities are subsequently partitioned into hexane. The drug is chromatographed as its bis-trimethylsilyl derivative, with the analog thiamphenicol as the internal standard. Within-run precision (CV) is 4.4% at a serum concentration of 41 mg/liter and 9.2% at a concentration of 5 mg/liter. Over a six-month period, the run-to-run variation was 5.1% at 40 mg/liter (n = 24). Results by the gas-chromatographic method compared well with those by an established colorimetric procedure; mean concentrations for the comparison samples in the two procedures were 18.4 mg/liter and 17.6 mg/liter, respectively (n = 27), with a coefficient of correlation of 0.998. The gas-chromatographic method is more precise and specific than classical microbiological procedures and is suitable for routine therapeutic monitoring of serum chloramphenicol concentrations.
Chloramphenicol↗
Influence of tryptophan loading on urinary excretion of anthranilic acid and 3-hydroxyanthranilic acid by men and women as determined by alkali flame ionization gas chromatography.
A gas chromatographic method with alkali flame ionization detection is described for the determination of urinary total (free and conjugated) anthranilic acid (AA) and 3-hydroxyanthranilic acid (HAA) as their pentafluorobenzyl esters. Prior to analysis, urine was hydrolysed using hydrochloric acid in a boiling water bath. The highest AA and HAA yields were obtained with 4 M hydrochloric acid and a hydrolysis time of 4 h. The coefficients of variation of the between-run analyses of AA and HAA at the endogenous level were 7.2 and 5.8%, respectively. The average recovery for both substances was 84%. The method described has been used to study the excretion of AA and HAA in the urine of healthy males and females before and after an oral load of tryptophan. Furthermore, the influence of oral contraceptives has been investigated. Results indicate that for both sexes the excretion of AA in the urine was higher than that of HAA, except after tryptophan loading. The excretion of AA by women was higher than by men. For HAA, the results of both sexes were comparable. Furthermore, for neither of the sexes was a diurnal variation of AA or HAA observed. After tryptophan loading, the formation of HAA was increased by more than that of AA. Results obtained for women on oral contraceptives indicate a hormonal-induced inhibition of AA formation.
3-Hydroxyanthranilic Acid↗
Determination of fruit juice authenticity by capillary gas chromatography with flame ionization detection.
A method using capillary gas chromatography with flame ionization detection was developed to determine the addition of high-fructose syrup and beet or cane invert syrup to apple or orange juice. Fingerprint oligosaccharides in these inexpensive sweeteners were not detectable (area < 1000) in pure apple or orange juice. One hundred twenty-three pure apple juice and 60 pure orange juice samples representing growing regions around the world were analyzed. Ten samples were intentionally adulterated with each sweetener at levels of 5, 10, and 15%. The detection limit for each sweetener was 5%.
Beverages↗
Flame-ionization GLC assay for fluorouracil in plasma of cancer patients.
A rapid and specific flame-ionization GLC method was developed for the determination of plasma fluorouracil. The chloro analog is used as the internal standard. The method involves the isolation of both the drug and the internal standard from plasma on a strong anion-exchange column at pH 10. Elution is performed with acetic acid in methanol. The evaporated eluate is dissolved in tetrahexylammonium hydroxide. An aliquot of the resulting solution is introduced directly into the gas chromatograph, where conversion to the bishexyl derivatives and subsequent separation take place. The extraction recovery from blank plasma, to which fluorouracil was added, was 96.8 +/- 2.4% (SD). Linearity was proven in the range from 0 to 25 micrograms/ml, whereas the detection limit of the method was estimated at about 2 micrograms/ml of plasma. The within-run precision was determined at three different fluorouracil levels. To demonstrate method applicability, plasma samples obtained from cancer patients to whom 1 g of fluorouracil had been administered intravenously were analyzed.
Alkylation↗
Stability studies of carbamate pesticides and analysis by gas chromatography with flame ionization and nitrogen-phosphorus detection.
As a result of thermal stability studies of carbamate pesticides, a method has been proposed for their direct determination by gas chromatography in the ranges 1-20 and 0.1-1 mg l(-1), using flame ionization and nitrogen-phosphorus detection, respectively. The method allows the determination of propham, propoxur, carbofuran, carbaryl, methiocarb, isopropoxyphenol and naphthol in powdered potato samples. The analytes were previously extracted with a light petroleum-dichloromethane (1:1, v/v) mixture and preconcentred by solid-phase extraction through a C8 cartridge. The recoveries obtained from spiked potato samples (n=4 replicates) at two concentration levels, 10 and 0.5 mg of pesticide per kg of sample, were in the ranges 72-115 and 50-73%, with relative standard deviations of 2-7 and 5-8%, respectively. The detection limits were 50-210 and 41-53 microg kg(-1) with flame ionization and nitrogen-phosphorus detection, respectively, and reaching the maximum residue levels, 0.05 mg kg(-1) for methiocarb and propoxur, set by the Real Decreto 280/1994 (based on the European directive).
Calibration↗
Determination of volatile residual solvents in traditional Chinese medicines by headspace solid-phase microextraction and cryogenic gas chromatography with flame ionization detection.
A method based on headspace solid-phase microextraction and cryogenic gas chromatography with flame ionization detection was developed for the determination of volatile residual solvents in traditional Chinese medicines. A laboratory-made cryogenic chromatographic system was used for the separation of 15 kinds of residual solvents. During the analysis, a 65 microm PDMS/DVB fiber was used to extract the residual solvents, the extraction time was controlled at 0 degrees C for 15 min, and the NaCl content of the sample was maintained at 30%. The limits of detection ranged from 0.08 (for octane) to 5000 microg/L (for ethanol), and the relative standard deviations were < 8%. The recoveries from spiked samples ranged from 88 to 112%. Trace levels of residual solvents in several traditional Chinese medicines were effectively identified and quantified.
Calibration↗
Thin-layer chromatography-flame ionization detection Iatroscan system.
The thin-layer chromatography-flame ionization detection (TLC-FID) Iatroscan system is a technique which is still being evolved. Quantification with the TLC-FID system relies heavily on the accurate setting up and calibration of the instrument. An appreciation of the factors that influence the analysis can eliminate significant errors. At least a few of the numerous operating variables need to be fixed to obtain coherent results from different laboratories. Hydrogenation of the sample is recommended in order to improve quantification with the Iatroscan system. The improved reproducibility obtained with automatic sample spotters compared with manual spotting indicates that autosampling is highly advisable.
Chromatography, Thin Layer↗
Application of thin-layer chromatography with flame ionization detection to the characterization of organic extracts from diesel exhaust particulates.
Thin-layer chromatography with flame ionization detection has been applied to the analysis of organic extracts of diesel exhaust particulates. Non-volatile organics whose boiling points are higher than ca. 300 degrees C can be analyzed, with a detection limit of ca. 0.03 micrograms and a relative standard deviation of ca. 10%. The organic extracts are separated into aliphatics , aromatics and polars by the development procedure with n-hexane, and the polars can be separated further by using toluene as the solvent. Some examples of application are presented.
Chromatography, High Pressure Liquid↗
Prediction of relative response factors for flame ionization and photoionization detection using self-training artificial neural networks.
The relative response factors (RRFs) of a flame ionization detection (FID) system and two pulsed discharge photoionization detection (PID) systems with different discharge gases are predicted for a set of organic compounds containing various functional groups. As a first step, numerical descriptors were calculated based on the molecular structures of compounds. Then, multiple linear regression (MLR) was employed to find informative subsets of descriptors that can predict the RRFs of these compounds. The selected MLR model for the FID system includes seven descriptors and two selected MLR models for the PID systems with argon- and krypton-doped helium as the discharge gases, respectively, include six and five descriptors. The descriptors appearing in the MLR models were considered as inputs for the self-training artificial neural networks (STANNs). A 7-7-1 STANN was generated for prediction of RRFs of the FID system, and two STANNs with the topologies of 6-7-1 and 5-6-1 were generated for the two PID systems. Comparison of the results indicates the superiority of neural networks over that of the MLR method. This is due to the nonlinear behaviors of relative response factors for all type of detectors studied in this work.
Flame Ionization↗