A Soil Water Extraction Method Using Accelerated Solvent Extraction Technique for Stable Isotope Analysis / 分析化学

Soil water is one of the most important components in hydrological cycle. The stable hydrogen and oxygen isotopes in soil water have been increasingly used in the ecological, environment and hydrological research. In view of different techniques for extracting soil water, there is significant difference in theδD andδ18 O composition. This paper presents a method for analyzing hydrogen and oxygen isotopes in soil water by using elemental analyzer and isotope ratio mass spectrometry with accelerated solvent extraction for sample pretreatment. The conditions are: extraction solvent: dichloromethane, temperature: 100 ℃, pressure of 10. 3 MPa, static time:10 min. The samples were extracted three times, and with cycle values of four, four and three, respectively. Comparing with the added water, the deuterium and oxygen isotope values in the extracted soil water enrich 2. 12‰-4. 58‰ and 0. 17‰-0. 93‰, respectively. The reproducibility of replicate extractions of soil water is around ±0. 89‰ for δD and ±0. 37‰ for δ18 O.

Accuracy of systolic pressure variation in monitoring blood volume / 中华麻醉学杂志

Objective To evaluate the accuracy of systolic pressure variation (SPV) in monitoring blood volume in patients.Methods Twenty-two ASA Ⅱ or Ⅲ patients (17 male,5 female),aged 49-79 yr,with body height 153-173 cm,weighing 55-89 kg,scheduled for elective coronary artery bypass grafting under cardiopulmonary bypass,were studied.Stroke volume variation (SVV) was monitored based on the arterial pressure wave and SPV measured based on the invasive arterial pressure wave after changing the title.After the chest was closed,the volume load test was immediately carried out.6％ hydroxyethyl starch 130/0.4 50-80 ml/min was infused via the jugular vein until cardiac index (CI) increased by 10％.HR,mean arterial pressure (MAP),SPV,CI,SVV,stroke volume index (SVI),systemic vascular resistance index (SVRI),central venous pressure (CVP),and pulmonary capillary wedge pressure (PCWP) were recorded in supine position (T1),at 30° head-down tilt before skin incision (T1'),before (T2) and after opening the chest in supine position (T2'),before (T3) and after the volume load test in supine position after closing the chest (T3'),in supine position after skin closure (T4),and at 30° head-down tilt after skin closure (T4').The difference in SPV and SVV (△SPV and △SVV) was calculated.The receiver operator characteristic curve for △SVV and △ SPV in determining blood volume changes was plotted.Results MAP,CVP,PCWP,CI,and SVRI were significantly increased,while SVV and SPV were decreased at T1' compared with those at T1 (P ＜ 0.05).HR was significantly increased,while CVP was decreased at T2' compared with those at T2 (P ＜ 0.05).MAP,CVP,PCWP,and CI were significantly increased,while SVV and SPV were decreased at T3' compared with those at T3 (P ＜ 0.05).MAP,CVP,and PCWP were significantly increased,while SVV and SPV were decreased at T4' compared with those at T4 (P ＜ 0.05).The area under receive operator characteristic curve for △SVV and △SPV in determining blood volume changes was 0.603 and 0.616 respectively,and there was no significant difference (P ＞ 0.05).Conclusion SPV can accurately monitor the blood volume in patients.