First and foremost, ensure your sample is compatible with your freeze dry system before you use the unit. A good rule of thumb is to plan for your most challenging sample and choose a system based on that need.
It's not possible to modify a freeze dryer’s condenser temperature.
The condenser temperature should be 10 to 15°C below the sample’s eutectic point. Low freezing point solvents, for instance, should not be used on -50°C units.
Certain acids should not be used with bare stainless steel and should only be used with PTFE models. Systems that reach -84°C are ideal for lyophilizing samples with low eutectic temperatures (like those that contain acetonitrile).
Systems that reach -105°C can handle samples containing small amounts of ethanol.
冻干的物质一定要和冷阱的温度相匹配,一般选型为物料冰点低于冷阱温度10到15℃;
不锈钢的冷阱不大适合含有较多酸性物质的冻干,可将冷阱做耐腐蚀的铁氟龙喷塑;
-80℃的冷阱比较适合低冰点物料(比如乙腈);
-105℃冻干机可用于冻干含有少量的乙醇类物料。
真空泵日常保养
定期和正确保养真空泵可保持真空泵性能和使用寿命;
首先保证冻干的物料适合的冻干机类型。
1. 如果是油泵,必须定期更换泵油,至少是500小时就要更换;如果发现油不清澈透明,脏,乳化,必须马上更换。
2. 冻干过程有较多粉尘产生的物料,需要选择合适的粉尘过滤器,减少甚至避免粉尘进入真空泵。如果不确定,冻干过程通过观察泵的油镜看是油是否浑浊。
3. 有些物料冻干需要在冻干机和真空泵中间增加有机溶剂或者酸性捕集器;
一般的油泵适合于含水性物料,含有有机溶剂或酸性物料选择分子杂交泵,或者采用其他方式去掉有机溶剂或者酸。
Note that some pumps, such as hydrocarbon free scroll pumps, can pull a deep vacuum for freeze drying without using oil. If you've chosen a scroll pump, make sure to change the scrolls after every 40,000 hours of use.
每次用完冻干机后必须清理干净。
It's necessary to defrost and drain the condenser after each standard run.
每次使用后必须保证冷阱里面无水;含有化学物质或者有机溶剂的每个部件要清理干净。不让水尤其是含有化学物质的水留在冷阱里。
如果用过酸性物质,必须让冷阱接触过的地方中和;
使用注意:
1. 没有*预冻结实的物料不能干燥;否则大量的水分会蒸发或者升华,从而使冷阱无法及时捕捉并进入真空泵。
2. 冻干过程中如果发现物料开始融化,应该及时将物料从冻干机中取出。
真空计章节
真空计一般采用皮拉尼真空规管或者热电偶型号真空规管。
皮拉尼电阻型测量范围广可测量0.5Pa 到110kpa,一般采用高精度电阻的钨丝制作,遇到较高氧气直接供电容易烧坏,真空计供电时候,真空泵应该启动。
冻干机使用后没有及时清理干净冷阱,更容易损坏真空规管
。
热电偶型真空计测量范围较窄,一般为200pa 以下,不过冻干机的冻干范围一般在5-20Pa,冻干时候真空测量可使用,且热偶型相比皮拉尼型较为耐用。
杂质可能粘到规管电阻丝上,造成真空计不准或者定期需要清洗钨丝或者热偶,可将探头前部浸泡在纯酒精中清洗,取出后倒置晾干后再使用。