Separation of selenium species and their sensitive determination in rice samples by ion-pairing reversed-phase liquid chromatography with inductively coupled plasma tandem mass spectrometry.

A highly sensitive method was developed for the simultaneous separation and determination of organic and inorganic selenium species in rice by ion-pairing reversed-phase chromatography combined with inductively coupled plasma tandem mass spectrometry. To achieve a good separation of these species, a comparison between anion-exchange chromatography and ion-pairing reversed-phase chromatography was performed. The results indicated that ion-pairing reversed-phase chromatography was more suitable due to better separation and higher sensitivity for all analytes. In this case, a StableBond C18 column proved to be more robust or to have a better resolution than other C18 columns, when 0.5 mM tetrabutylammonium hydroxide and 10 mM ammonium acetate at pH 5.5 were used as the mobile phase. Moreover, an excellent sensitivity was obtained in terms of interferences by means of tandem mass spectrometry in the hydrogen mode. The detection limits were 0.02-0.12 µg/L, and recoveries of five selenium species were 75-114%, with relative standard deviations ≤ 9.4%. This method was successfully applied to the analysis of rice samples. Compared with previous studies, the proposed method not only gave comparable results when used for measuring selenium-enriched rice, but it can provide greater sensitivity for the detection of low concentrations of selenium species in rice.

GPC-1 may serve as a predictor of perineural invasion and a prognosticator of survival in pancreatic cancer.

OBJECTIVE: The purpose of this study was to investigate the expression of glial cell derived neurotrophic factor (GDNF), glypican-1 (GPC-1), and matrix metalloproteinase-9 (MMP-9), and their association with clinicopathologic characteristics as well as prognostic significance in pancreatic cancer. METHODS: Immunohistochemical assessment of GDNF, GPC-1, and MMP-9 was performed in 62 cases of surgically resected pancreatic cancer. Perineural invasion in pancreatic cancer was observed by marking nerve fiber with S-100, while 16 normal pancreatic tissues were used as normal control. Correlations of GDNF, GPC-1 and MMP-9 expressions with clinicopathologic parameters were analyzed. A survival analysis was performed to find the prognostic significance. RESULTS: The expressions of GDNF, GPC-1 and MMP-9 in pancreatic cancer tissue were significantly higher than of those in normal pancreatic tissues (41/62 vs. 5/16 for GDNF, 35/62 vs. 2/16 for GPC-1, and 37/62 vs. 3/16 for MMP-9; p<0.01, respectively). The overexpression of GDNF, GPC-1, and MMP-9 in pancreatic cancer tissue was significantly related to the perineural invasion (p<0.05). Although the overexpression of these genes was related to poor survival, GPC-1 had an independent prognostic effect on overall survival. CONCLUSION: GPC-1 is significantly related to the perineural invasion of pancreatic cancer, holding some prognostic significance in patients with pancreatic cancer.