氮(dan)吹儀主要用(yong)于(yu)氮(dan)吹濃縮步驟(zou)，基本原理是與氮(dan)氣(qi)瓶鏈(lian)接(jie)，通過減壓閥將氮(dan)氣(qi)通入到氮(dan)吹儀的通氣(qi)板中，然(ran)后通過通氣(qi)板上的氮(dan)吹針對樣(yang)品(pin)進(jin)行吹掃達到濃縮目的，并(bing)在試管(guan)底(di)部(bu)進(jin)行加熱(re)用(yong)來(lai)加速溶劑的揮發。那么，影響濃縮的因素有(you)哪(na)些呢(ni)？
氮氣流壓力對回收率(lv)的影響
旋渦(wo)氮(dan)吹濃縮(suo)儀氮(dan)氣(qi)(qi)流(liu)量改(gai)變是通過調節氮(dan)氣(qi)(qi)壓力實現,管徑不變,流(liu)量與壓力成正比關系。氮(dan)氣(qi)(qi)流(liu)的壓力越(yue)大(da),氮(dan)氣(qi)(qi)流(liu)流(liu)量就(jiu)越(yue)大(da)。氮(dan)氣(qi)(qi)流(liu)撞到(dao)試管壁形成旋渦(wo),溶(rong)(rong)劑(ji)接(jie)觸表面積和旋渦(wo)剪力越(yue)大(da),溶(rong)(rong)劑(ji)的蒸發越(yue)快,同(tong)時(shi)不停吹掃氮(dan)氣(qi)(qi)能避(bi)免(mian)溶(rong)(rong)劑(ji)與空氣(qi)(qi)發生化(hua)學反應。
水(shui)浴溫度對(dui)氮氣流的影響
濃縮(suo)(suo)(suo)管浸在水(shui)(shui)浴(yu)中(zhong),通(tong)(tong)過傳熱控制(zhi)濃縮(suo)(suo)(suo)管內溶(rong)液溫(wen)(wen)度(du)(du)。通(tong)(tong)常(chang)水(shui)(shui)浴(yu)溫(wen)(wen)度(du)(du)控制(zhi)范圍從30℃到60℃。溫(wen)(wen)度(du)(du)設定根據濃縮(suo)(suo)(suo)管里溶(rong)劑的沸點(dian)和被分析物(wu)質(zhi)(zhi)(zhi)性質(zhi)(zhi)(zhi)而(er)(er)定。水(shui)(shui)浴(yu)溫(wen)(wen)度(du)(du)一(yi)般要低(di)于溶(rong)劑沸點(dian)溫(wen)(wen)度(du)(du),否則可(ke)能(neng)蒸發(fa)速度(du)(du)過快(kuai),回收率(lv)可(ke)能(neng)降(jiang)低(di)。但是溫(wen)(wen)度(du)(du)設置過低(di),會(hui)導致(zhi)(zhi)濃縮(suo)(suo)(suo)時(shi)(shi)(shi)間(jian)過長(chang),長(chang)時(shi)(shi)(shi)間(jian)氮氣吹(chui)掃也會(hui)導致(zhi)(zhi)待測物(wu)質(zhi)(zhi)(zhi)揮發(fa)。在設置水(shui)(shui)浴(yu)溫(wen)(wen)度(du)(du)時(shi)(shi)(shi)應充分考(kao)慮溶(rong)劑的沸點(dian)和揮發(fa)性。溫(wen)(wen)度(du)(du)高,能(neng)縮(suo)(suo)(suo)短濃縮(suo)(suo)(suo)時(shi)(shi)(shi)間(jian),避免目標物(wu)質(zhi)(zhi)(zhi)與空氣長(chang)時(shi)(shi)(shi)間(jian)接(jie)觸,減少目標物(wu)質(zhi)(zhi)(zhi)揮發(fa),但過高溫(wen)(wen)度(du)(du)會(hui)導致(zhi)(zhi)溶(rong)劑沸騰,從而(er)(er)降(jiang)低(di)回收率(lv)。