Determination of morphine by electron capture gas-liquid chromatography

We describe a micromethod for determining as little as 0.1 microgram of morphine per liter of human urine. The procedure is about 20-fold more sensitive than are currently used gas-liquid chromatographic methods. It is particularly suitable for use as a confirmatory method for large-scale radioimmunoassay screening tests. The procedure involves extraction of morphine from urine and analysis of its heptafluorobutyryl derivative by gas-liquid chromatography with electron capture detection. Morphine can be determined by this procedure over a range of 0.1-200 microgram/liter of urine, 2 pg of the pure derivative being the lowest amount detectable. Urine samples from patients receiving methadone were analyzed by thin-layer chromatography, radioimmunoassay, and our procedure. The results by our procedure agreed well with those obtained by radioimmunoassay.     

Determination of perfluorocarboxylic acids by gas-liquid chromatography in rat tissues

Gastrin plays an important role in regulating gastric acid secretion and gastrointestinal mucosal growth but its cellular sites of action in man have not been determined. Using cryostat sections of gastric mucosal tissue we have identified (125I-gastrin binding followed by fixation-wet emulsion autoradiography) and characterized (125I-gastrin binding followed by counting) a gastrin receptor binding site in the human stomach. This site displayed binding characteristics similar to those observed in isolated cell systems: specifically, 125I-gastrin binding was rapid (t1/2 approximately 10 min at 37 degrees C), temperature-dependent (3.5 fold more radioligand bound at 22 degrees C than at 4 degrees C) and saturable. The binding of the radioligand was also tissue specific and was five-fold greater in the gastric body than in the gastric antrum and duodenum. In the autoradiographs, silver grains were localized only to parietal cells and not to other epithelial cell types. In the presence of 40 nM gastrin grains were no longer present over parietal cells demonstrating that these sites were both saturable and of high affinity. These data provide the first demonstration of gastrin binding sites (putative receptors) on parietal cells in the human stomach and suggest that gastrin acts directly on these cells to help regulate gastric acid secretion and/or mucosal growth.     

Identification of N-nitrosodimethylamine in ambient air by capillary gas-liquid chromatography mass spectrometry computer

Organic vapors in ambient air, at or near an industrial site in Baltimore, Maryland, were collected by adsorption on a sorbent of porous polymer (Tenax GC, 35/60). The pollutants were recovered by thermal desorption and analyzed by gas-liquid chromatography mass spectrometry computer using capillary glass SCOT columns. N-Nitrosodimethylamine was identified from its mass spectrum as a constituent of the atmosphere in the areas sampled. The identification of this compound was confirmed by comparison of its mass spectrum with that of authentic N-nitrosodimethylamine; identical retention times of unknown and authentic compound on three different capillary columns were observed.     

The determination of methionine in proteins by gas-liquid chromatography

Intact methionine residues in proteins were rapidly and precisely determined by measuring methyl thiocyanate released during the reaction with CNBr and separated by g.l.c. Conditions for the reaction and for chromatography on columns of Porapak P-S are described. The recovery of methyl thiocyanate from several methionine derivatives and analogues were examined. Carbamoylmethionine was adopted as a stable primary standard and ethyl thiocyanate as internal standard. The measured methionine content of several isolated proteins was close to the theoretical value indicated by previous work and the results for these and a range of food proteins agreed well with results obtained by ion-exchange chromatography after performic acid oxidation. Since CNBr does not react with methionine sulphoxide and a preliminary hydrolysis is not required, the method discriminates between methionine and any methionine sulphoxide that may be present. It could be useful in studies on the nutritional availability of methionine in processed foods.     

Determination of orthophosphoric and orthophosphorous acids in the workplace air using ion chromatography

The authors elaborated a method measuring air level of orthophosphorous and orthophosphoric acids by means of ion chromatography within the range of 0.1-25 mg/cu m. The samples are extracted through concentration on a filter. The analysis regime includes depression of the background levels. The separating column (4 x 200 mm) is filled with anion exchanger BT IAN, the suppressing column (6 x 150 mm) is filled with cation exchanger Dowex 50 x 8, the elutriating agent is 1.5 mM of sodium carbonate, the detector is conductometric. Minimal amounts of ions that could be detected in the analyzed solution are 7-10 ng (HPO32-), 10-15 ng (HPO 42-). The method is designed to analyze the air of workplace.     

纸上色层分离-重量法测定铝铌合金中铌

铝铌合金中铌的含量对铝铌合金的性能和应用有直接影响。使用纸上色层分离-重量法测定铌时,铌与其他元素的分离效果受层析剂配比和环境的影响较大。实验通过考察称样量、层析剂配比、层析时间、共存元素的影响等,最终确定了最佳的试验条件,实现了铝铌合金中铌含量的准确测定。试样经氢氟酸和硝酸溶解,将浓缩后的溶液涂在色层纸上,利用铌与铝及其他共存元素在特定的层析剂中迁移速率的不同,实现铌与其他共存元素的分离;将含有铌的色层纸在900℃马弗炉中灼烧至恒量。对于铌质量分数为50%~80%的铝铌合金,称样量选择0.10g,层析剂中4-甲基-2-戊酮、丁酮、氢氟酸、硝酸体积比为125∶42∶32∶7,层析时间为6h时分离效果最佳,试样中共存的铁、钼、硅、镍、铬等微量元素对测定结果无影响,若样品中钽的质量分数大于0.01%,需从粗氧化铌沉淀中减去氧化钽的质量。实验方法用于3种铝铌合金样品中铌的测定,结果的相对标准偏差(RSD,n=11)为0.18%~0.29%;加标回收率为98%~102%。选择4家实验室协同验证,经科克伦检验测试结果无明显差异。     

纸上色层分离-重量法测定铝铌合金中铌

铝铌合金中铌的含量对铝铌合金的性能和应用有直接影响。使用纸上色层分离-重量法测定铌时,铌与其他元素的分离效果受层析剂配比和环境的影响较大。实验通过考察称样量、层析剂配比、层析时间、共存元素的影响等,最终确定了最佳的试验条件,实现了铝铌合金中铌含量的准确测定。试样经氢氟酸和硝酸溶解,将浓缩后的溶液涂在色层纸上,利用铌与铝及其他共存元素在特定的层析剂中迁移速率的不同,实现铌与其他共存元素的分离;将含有铌的色层纸在900℃马弗炉中灼烧至恒量。对于铌质量分数为50%～80%的铝铌合金,称样量选择0.10g,层析剂中4-甲基-2-戊酮、丁酮、氢氟酸、硝酸体积比为125∶42∶32∶7,层析时间为6h时分离效果最佳,试样中共存的铁、钼、硅、镍、铬等微量元素对测定结果无影响,若样品中钽的质量分数大于0.01%,需从粗氧化铌沉淀中减去氧化钽的质量。实验方法用于3种铝铌合金样品中铌的测定,结果的相对标准偏差(RSD,n=11)为0.18%～0.29%;加标回收率为98%～102%。选择4家实验室协同验证,经科克伦检验测试结果无明显差异。     

Enzymatic activity assays in the hepatic cell by mass fragmentography associated with gas-liquid chromatography

The most generalized methods in enzymology are based on the quantitative assay of compounds, substrate or coenzyme, by spectrophotometry without any separation. Such a method is ruled out if the colorimetric reaction is not specific of the compound. In liver enzymology, aside the classical metabolic pathways, such assays are difficult to apply, especially when several metabolic steps are investigated. It is therefore necessary to use separative methods to isolate the metabolized substrate(s). For instance, the reductive catabolism of corticosterone leads to fourteen isomers (two dihydrocompounds, four tetrahydrocompounds and eight hexahydrocompounds) in which their respective productions are sex and age-linked. A position isomer of corticosterone, the 18-hydroxy-11-deoxy-corticosterone, follows the same reductive route. In adrenals some reduced metabolites arise from these two steroid hormones and are age dependent. When such metabolites are amenable to volatilization for gas chromatography, the interfacing of the gas chromatograph to the mass spectrometer allows to identify each compound introduced in the spectrometer. Among the ions produced by fragmentation of a compound or of a family of compounds, several specific fragments can be selected to be monitored along the chromatographic run leading to mass peaks which are quantitatively proportional to the amount of compounds, as far as other foreign molecules do not contribute fo fragment productions. These methods called mass fragmentography or multiple ion detection, or selected ion monitoring, allow with the help of all the resources of gas chromatography such the derivatization of studied molecules with heavy isotope labeled reagents to use the same unlabeled derivatized molecules as carriers and internal standards at once. This method allows to quantitate at the level of the picomolecule or less. Examples will be given with the study of the metabolism hormone steroids and xenobiotic compounds by the liver and adrenals in the animal and by isolated liver and adrenal cell cultures.     

Measurement of thiamylal and thiopental in plasma by electron capture and flame photometric gas-liquid chromatography

We describe an isothermal gas-liquid chromatographic procedure developed for measuring thiamylal and thiopental in plasma. The unchanged drug is extracted into ethyl acetate from acidified plasma, together with an internal standard. The solvent is removed, the residue methylated, aliquots, diluted with benzene, are injected into a 183-cm gas-liquid chromatographic column containing 3% OV-17. Sensitivity of detection is in the nanogram to picogram range.     

Plasma pentobarbitone levels. Estimation by gas-liquid chromatography after clinical doses

A simple and relatively quick method of estimating pentobarbitone in plasma samples is reported using an ether extraction and gas-liquid chromatography. Glutethimide was used as the internal standard and proved reliable. Reproducible results were obtained in plasma following 100 mg pentobarbitone given by mouth or intramuscular injection. Evaporation in a heating block at 37 degrees C and storage of samples at -20 degrees C prior to analysis is recommended.     

Automated urinary steroid profiles by capillary column gas-liquid chromatography and a computing integrator

13 Urinary steroid metabolites have been determined by automated gas-liquid chromatography with a 20-m glass capillary column and a computing integrator. Concentrations up to 2 mg/24 h computed by the integrator compare well with those obtained by peak height measurements. At higher concentrations discrepancies occurred, paticularly for the C21 steroids where falsely low values were calculated using peak heights. Mean excretion by healthy males and females of seven steroid metabolities is presented.     

Determination of percent body fat by the newly developed sulfur hexafluoride dilution method and air displacement plethysmography

The reliability and validity of two newly developed densitometric methods for determining the human body volume and percent body fat (%FAT), the sulfur hexafluoride dilution method (SHF) and air displacement plethysmography (ADP), were evaluated in comparison with the underwater weighing method (UWW). Seven healthy male volunteers (age 31 to 44, mean height 166.0 cm, weight 61.4 kg) participated in this study. The same-day test-retest coefficients of variation (CVs) for body volume and %FAT measurements were not significantly different among the three methods. SHF and UWW showed a strong correlation in terms of body volume and %FAT, with the correlation coefficients (r) being 0.9997 and 0.986, respectively. The correlation between ADP and UWW was slightly weaker (r = 0.9997 for body volume and 0.907 for %FAT). However, body volumes measured by SHF and ADP were significantly different from that by UWW when compared by mean values. Such differences were also found for %FAT measurements. The regression lines of body volume measured by SHF and ADP on that by UWW were almost equivalent to the line of identity. However, those of %FAT measured by SHF and ADP on that by UWW were significantly different from the line of identity. Because the reliability of SHF and ADP appeared to be high, further validation and improvement are required and worth doing.     

Studies on photodegradation of vitamin K1. I. Determination of vitamin K1 by gas-liquid chromatography (author''s transl)

Glucosyl sphingosine was isolated from the spleen of a patient with adult-type Gaucher's disease. The yield of purified glucosyl sphingosine was 9.3 nmoles/g wet tissue. The gas chromatography-chemical ionization mass spectrum of acetylated glucosyl sphingosine showed peaks due to the presence of ions formed by successive loss of acetic acid (mass 60) from the molecular ion (QM+, 714). Fragments from acetylated sugar, m/e 331, and from the sphingosine residue, m/e 306, were also detected. The GC-CI mass spectrum of the trimethylsilyl derivative of glucosyl sphingosine showed peaks due to the molecular ion (QM+, 822), ions from the sugar moiety (m/e 361, 271), and ions from the sphingosine base (m/e 264, 280). Fragmentation analysis of the purified sample by GC-EI and GC-CI mass spectrometry confirmed the structure glucopyranosyl(1 leads to 1)-1,3-dihydroxy-2-amino-4-octadecene.