(1) filler (stationary phase)-core
Choosing suitable packing for solid phase extraction column is the premise to ensure ideal results.
(2) strength of eluent
1. When using common stationary phase, the solvent strength increases with its polarity.
2. Using reversed-phase stationary phase, the strength of solvent increases with the weakening of its action mechanism. (3)PH value.
The PKa of ion exchange stationary phase, analyte and interfering substance is different. By adjusting the PH value, the stationary phase can be charged, the analyte has opposite charge, and the interfering substance has no charge. Or conversely, the stationary phase is charged, the interfering substance is charged oppositely, and the analyte is uncharged, thus achieving the purpose of separation and purification.
At present, nitrogen blower is also called nitrogen blow dryer and automatic rapid concentrator. There are two kinds of nitrogen blowers in the market: dry nitrogen blowers and water bath nitrogen blowers. It has been recognized and accepted by more and more people that nitrogen blower replaces traditional rotary evaporator to concentrate samples.
1. Working principle of nitrogen blower
We know that there are two ways to accelerate evaporation: to strengthen the surrounding air flow and its temperature. Nitrogen is an inert gas that can isolate oxygen and prevent oxidation. Nitrogen blower uses the rapid flow of nitrogen to break the gas-liquid balance above the liquid, thus accelerating the volatilization speed of the liquid; The temperature is raised by dry heat or water bath heating (the boiling point of the target is generally higher than the boiling point of the solvent), so as to achieve the purpose of concentration.
2. Main components of nitrogen blower
It mainly includes gas distribution chamber, gas needle, height adjustment bracket, nitrogen interface, height fine adjustment parts, pillars, fixed parts, chassis, bushing, heating block, sample test tube or bottle and other parts.
3. How to use the nitrogen blower (taking the water bath nitrogen blower as an example)
After installing the nitrogen blower, support the chassis in a constant temperature water bath, turn on the power supply of the water bath, set the temperature of the water bath, and start heating the water bath. Lift the nitrogen blower, put the samples to be evaporated and concentrated on the sample positioning rack respectively, and lift them by the tray. The height of the tray and the positioning rack can be adjusted according to the size of the experimental sample test tube. Open the needle valve of the flowmeter, and the nitrogen will reach the gas distribution plate through the flowmeter and gas transmission pipe, and then be sent to the needle valve pipes (installed on the gas distribution plate) at all levels or above after gas distribution. Then, by adjusting the needle valve of the needle valve tube, nitrogen is blown to the liquid sample test tube through the needle valve tube and the needle, and the needle valve tube can be slid up and down by adjusting the lock nut, so that the height of the needle is adjusted, so that ripples are blown on the surface of the sample, and the sample will not splash. Finally, put the nitrogen blower in a water bath until evaporation and concentration are completed.
4. Advantages of nitrogen blower
(1) can handle multiple samples at one time, and its advantage is more obvious in multi-factor and multi-level repeated experiments.
(2) The experimental operation is concise and flexible. The process of concentration can be adjusted at any time without constraints.
(3) In the experiment, operators are not required to maintain for a long time, which saves manpower.
(4) The nitrogen blower has accurate and sensitive concentration, which can avoid sample loss.
5. Application field of nitrogen blower
Nitrogen blowing instrument is mainly used for purification and preparation of analytical samples such as chromatography and mass spectrometry, and is widely used for volatilization of solvents such as water, toluene, methanol and acetone. Application fields include:
(1) pesticide residue analysis: such as vegetables, fruits, grains, plant tissues, etc.
(2) Environmental analysis: such as drinking water, groundwater and polluted water samples.
(3) Pharmaceutical drug inspection: such as traditional Chinese medicine.
(4) Biological analysis: such as serum, plasma, blood and urine.
(5) Commodity inspection: such as the inspection of dioxin and Crauste Luo; (6) Food and drinks: such as milk, wine, beer, liquid drinks, etc.