Detection of Tocopherol in Oilseed Rape (Brassica napus L.) Using Gas Chromatography with Flame Ionization Detector

The variation among Chinese genotypes of Brassica napus L. for seed tocopherols content and their analysis using gas chromatography has not been comprehensively reported till to date. In the present study, the tocopherol contents of four Chinese genotypes of Brassica napus L., namely, Gaoyou 605, Zhejiang 619, Zheshuang 758, and Zheshuang 72, were evaluated using three modified sample preparation protocols （P1, P2, and P3） for tocopherol extraction. These methods were distinguished as follows. Protocol one （P1） included the evaporation of solvent after extraction without silylation. Protocol two （P2） followed the direct supernatant collection after overnight extraction without drying and silylation. Protocol three （P3） included trimethylsilylation with N,O-bis（trimethylsilyl） trifluoroacetamide. Genotypic comparison of tocopherol and its isoforms revealed that Gaoyou 605 was dominant over the other genotypes with （140.5＋ 10.5）, （316.2＋ 9.2）, and （559.1＋ 24.3） ~tg g-~ of seed meal ct-, 7-, and total （T-） tocopherol, respectively, and a 0.44＋0.04 ^- to 7-tocopherol ratio. The comparison of the sample preparation protocols, on the other hand, suggests that P3 is the most suitable method for the tocopherol extraction from Brassica oilseeds and for the analysis of tocopherols using gas chromatography flame ionization detector （GC-FID）. Trimethylsilylation is the key step differentiating P3 from P1 and P2. Variations detected in tocopherol contents among the Chinese rapeseed （B. napus） genotypes signify the need to quantify a wide range of rapeseed germplasm for seed tocopherol dynamics in short and crop improvement in long.

A system consisted of flame ionization detector and sulfur chemiluminescence detector for interference free determination of total sulfur in natural gas

A new detection system consisted of a flame ionization detector（FID） and a sulfur chemiluminescence detector（SCD） was developed for sensitive and interference free determination of total sulfur in natural gas by non-separation gas chromatography. In this system, sulfur containing compounds and hydrocarbons were firstly burned in the FID using oxygen rich flame and converted to SO_2, CO_2 and H_2O, respectively. The products from FID were transported into the SCD with hydrogen rich atmosphere wherein only SO_2 could be reduced to SO and reacted with O_3 to produce characteristic chemiluminescence. Therefore, the chemiluminescence of CO found in conventional SCD were eliminated because CO_2 could not be reduced to CO under these conditions. The experimental parameters were systematically investigated. Limit of detection obtained by the proposed system is better than 0.5 mmol/mol for total sulfur and superior to those previously reported. The proposed method not only retains the advantages of the conventional SCD but also provides several unique advantages including no hydrocarbon interference, better stability, and easier calculation. The utility of this technique was demonstrated by the determination of total sulfur in real samples and two certified reference materials（GBW 06332 and GBW（E） 061320）.

Development of a Derivatization-free GC-FID Method for Evaluation of Free Fatty Acid Levels in Plasma of Diabetic Nephropathy Patients

Metabolism of free fatty acids（FFAs） is related to several important physiological events and therefore their quantitaion in biological samples arouses extensive interest and efforts.Existing gas chromatography with flame ionization detector（GC-FID） methods for the analysis of FFAs normally require derivatization of them in order to lower boiling points.But this extra procedure tends to induce additional error and it is laborious and time-consuming.A derivatization-free method was therefore established in the present investigation to determine FFAs in human plasma by capillary（GC-FID）.After extraction of FFAs from plasma,a highly polar FFAP（free fatty acid in plasma） column was employed to directly quantitate FFAs concentration,free from derivatization reaction.All sample pretreatments were carried out at room temperature,improving recovery of short-chain FFAs.Heptadecanoic acid（C17：0） was employed as internal standard,and the proposed method was validated for recovery,precision,sensitivity,stabi-lity,and linearity.Validation data show that it is suitable for clinical study that has been applied to the evaluation of FFAs levels in plasma of diabetic nephropathy（DN） patients during the course of treatment.Forty-seven patients diagnosed with DN were admitted to the double-blind experiment.Control group（n=17） underwent solely basic treatment and the patients did not show significant change in FFAs concentration during six months of treatment.Experiment group（n=30） was supplied with traditional Chinese medicine besides basic treatment.After six months of medication,their plasma concentration of palmitic acid（C16：0）,stearic acid（C18：0） and oleic acid（C18：1n-9） decreased while linolenic acid（C18：3n-3） increased significantly（P〈0.05）.These four compounds could be served as biomar-kers in the evaluation of drug efficacy,and their quantitation in plasma may provide additional information for disease progression in DN patients.