An analytical method of on-line injection technique including on-line dilution and on-line preconcentration with inductively coupled plasma mass spectrometry ( ICP-MS ) was established for the determination of trace metals in seawater, such as Cr, Mo, Cu, Pb, Zn, Cd, Fe, Mn, Ni, V, Co. This method could automatically make standard curves and match matrix, and by the on-line dilution and preconcentration modes, 11 trace metals could be analyzed directly. With high-level automation, CASS-5 and NASS-6 seawater standard samples were analyzed accurately by this method. The recovery of metals in seawater sample addition was between 80% and 115%. The method quantitation limits (μg/L ) of theses metals in seawater were 0. 06(Cr), 0. 06(Mo), 0. 01(Cu), 0. 005(Pb), 0. 01(Zn), 0. 006(Cd), 0. 03 (Fe), 0. 02(Mn), 0. 01(Ni), 0. 01(V), and 0. 01 (Co), respectively. This method was applied to analyze seawater samples of various salinities in Zhejiang coast, and the analysis results were consistent with results of conventional atomic absorption method.

Objective:To investigate the diagnostic value of dynamic contrast enhanced MRI (DCE-MRI) quantitative parameters for preoperative staging of gastric cancer and its relationship with prognostic factors.Methods:The clinical data of 98 patients with gastric cancer from March 2021 to March 2022 in Guangyuan First People′s Hospital were retrospectively analyzed. All patients underwent DCE-MRI examination, MRI features were observed, and the DCE-MRI quantitative parameters were recorded, including the transport constant (K trans), volume fraction (V e) and rate constant (K ep). The expression levels of human epidermal growth factor receptor 2 (HER2) and epidermal growth factor receptor (EGFR) in gastric cancer tissue were detected by immunohistochemistry methods. The correlation between DCE-MRI quantitative parameters and T stage, HER2, EGFR of gastric cancer was analyzed by Spearman method; the receiver operating characteristic (ROC) curve was used to evaluate the diagnosis value of DCE-MRI quantitative parameters in T staging of gastric cancer. Results:Among 98 patients with gastric cancer, T 1 to T 2 staging was in 50 cases, T 3 to T 4 staging was in 48 cases; HER2 positive expression in gastric cancer tissue was in 35 cases, negative expression was in 63 cases; EGFR positive expression in gastric cancer tissue was in 43 cases, negative expression was in 55 cases. The K trans and V e in patients with T 3 to T 4 staging were significantly higher than those in patients with T 1 to T 2 staging: (0.25 ± 0.04) min -1 vs. (0.19 ± 0.03) min -1 and 0.45 ± 0.11 vs. 0.39 ± 0.09, and there were statistical differences ( P<0.01); there was no statistical difference in K ep between the two ( P>0.05). The K trans and V e in patients with HER2 positive expression were significantly higher than those in patients with HER2 negative expression: (0.27 ± 0.06) min -1 vs. (0.19 ± 0.03) min -1 and 0.49 ± 0.13 vs. 0.38 ± 0.08, and there were statistical differences ( P<0.01); there was no statistical difference in K ep between the two ( P>0.05). The K trans and V e in patients with EGFR positive expression were significantly higher than those in patients with EGFR negative expression: (0.28 ± 0.07) min -1 vs. (0.17 ± 0.04) min -1 and 0.50 ± 0.14 vs. 0.36 ± 0.08, and there were statistical differences ( P<0.01); there was no statistical difference in K ep between the two ( P>0.05). Spearman analysis result showed that the K trans was positively correlated with gastric cancer T stage, and the expression of HER2, EGFR in gastric cancer tissue ( r = 0.539, 0.612 and 0.640; P<0.01), the V e was positively correlated with gastric cancer T stage, and the expression of HER2, EGFR in gastric cancer tissue ( r = 0.462, 0.551 and 0.583; P<0.01), while there was no correlated between K ep and gastric cancer T stage and the expression of HER2, EGFR in gastric cancer tissue ( P>0.05). ROC curve analysis result showed that the area under the curve of K trans combined with V e in diagnosis the T 3 to T 4 staging of gastric cancer was 0.929, with a specificity of 81.25% and a specificity of 92.00%. Conclusions:The DCE-MRI quantitative parameters K trans and V e have certain value in the diagnosis of gastric cancer T staging, and they are closely related to the expression of prognostic factors HER2 and EGFR.