Headspace Sampler Maintenance

1, septum:

The septum is mainly used for sealing injection and cleaning the injection needle. Generally, the septum can reach the life of more than one hundred injections. Different manufacturers have different material life spans, such as Agilent BTO (temperature and bleed) septum More than 400 times of life, while the red silicone septum is generally one hundred times. If you find that the inlet pressure drops, you can check whether the septum wears badly and the sealability deteriorates. Replace if necessary. Gutter debris can cause the background to rise. It can also contaminate the liner and block the column. It should be replaced frequently, and it must not wait until it is changed. A lot of color friends generally overtighten in installing and replacing the septum, which will cause the septum to shrink too much and become hard. When the sample is injected, the septum is likely to produce debris, and the service life is greatly reduced. Generally, it can be tightly sealed without air leakage.

2, liner:

The liner serves as the sample vaporization chamber in the GC. The sample is vaporized in the liner and brought into the gas phase. There are deactivation and no deactivation. There are also split/splitless, splitless, diverted, and direct flow. Sample, direct connection, focus, PTV, etc. Occasional replacement or incorrect use can result in poor peak shape, solute discrimination, poor reproducibility, sample decomposition, and ghost peaks. Liner maintenance is mainly cleaning, silanization and rational use of glass wool.

1) General cleaning Headspace sampler is mainly rinsed with pure water, methanol or anhydrous ethanol or ultrasonic cleaning. The contamination can be wiped gently with a cotton swab. Excessive force can not be used to avoid damaging the inner surface to generate active sites, and then placed in an oven 70 Degree of drying after drying and cooling can be sealed and stored.

2) Silanization is one of the most effective ways to eliminate surface activity of the carrier. It can eliminate the silanol groups on the surface of the carrier, weaken the hydrogen bonding force, and inactivate the surface. The general method is to soak or reflux for more than 1 hour with a 5 to 8% solution of the silylation reagent in toluene, then wash with anhydrous methanol to neutrality, and dry for use. Commonly used silylating agents are dimethyldichlorosilane (DMCS), trimethylchlorosilane (TMCS) and hexamethyldisilazane (HMDS). The best silanization is DMCS, followed by HMDS, and the TMCS is poor.

3) Use of headspace sampler glass wool. In most practical applications, a certain amount of glass wool can usually be filled inside the liner to increase the vaporization efficiency of the sample, and at the same time, it can also prevent the septum debris from clogging the column, but if glass wool is not used More live or breakpoints will increase the active points and will have a negative effect. The following applications do not recommend the use of glass wool: phenols, organic acids, pesticides, amines, drugs of abuse, reactive polar compounds, thermally unstable compounds.

4) Metal gasket (splitter/splitless plate): The function of sealing and current limiting, such as pure copper, stainless steel, and gold plating, is the best for gold plating. Regular or on-demand inspection, there is pollution can be detached with pure water or organic solvent ultrasonic cleaning, can be gently wiped with a cotton swab indicates that hard objects can not be scratched on the surface.

5) Column seal: Seal the connection between column and liner. Generally pure graphite, Teflon, metal, Vespel or 100% Vespel are added in proportion. The pure graphite material is generally used once, if the sealing effect can also be used repeatedly. Other materials can be used multiple times to seal without leakage.

The headspace sampler has a wide range of applications as a gas sampler for gas chromatography in the fields of food, medicine, environmental protection, and agriculture. Because the instrument adopts the pressure balance method for sample injection, it is characterized by reproducibility, good stability, and low sample residue, and is used by many users. Therefore, the current social possession of the instrument is relatively large.

Replace the upper and lower sealing rings of the syringe system regularly. The specific method can be seen in the user's guide. The needle seal has a service life of about 2500 cycles. On the touch screen, the useful life can be set 2400 times. After the number of uses expires, the instrument will display the replacement information on the status bar. After the replacement is completed, clear the count value. If the instrument is used frequently, it is generally best to do a system leak detection and valve leak detection in one month, find the leak, replace the needle seal.

In the process of using the instrument, the occurrence of failure is unavoidable. However, as long as the proper operation of the headspace sampler is used properly and an effective method is used for maintenance, the failure rate of the instrument can be reduced.

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