Factors To Be Considered In Selecting Syringe Filter

When treating chromatographic samples with syringe filter, other impurities should be avoided in the process of filtration. The appearance of such impurities may be that the shell material or filter membrane will shed particulate matter and bring it into the filtrate.

Therefore, the material of the filter membrane and the shell structure is very important. Different types of filter membranes are suitable for different types of samples.

Hydrophilic sample
The hydrophilic diaphragm has an affinity for water and is suitable for filtering water as a matrix solution. The available filter membranes are mixed cellulose ester (MCE), polyethersulfone (PES), nylon, hydrophilic PTFE, hydrophilic PVDF, etc.

Strongly corrosive organic solvents
Inert membranes such as PTFE, PVDF, and polypropylene (PP) are commonly used.

Protein solution
Selection of low protein adsorption membrane, such as hydrophilic PVDF, PES membrane.

Ion Chromatography
PES membrane filter is generally considered to be more suitable for the filtration of low inorganic ions solution.

If there are too many Impurities in the sample, the needle filter with pre-filtration should be considered when the filtration resistance is too large. The effect of 33mm is ideal.

Introduction And Selection Guide For Syringe Filters

Syringe filters are usually disposable. Normally, a sample corresponds to a filter head, because there is the possibility of cross-contamination when used many times. The material selection of the filter in the filter head is also the key to the correct use of the filter head.

Syringe filters do not need to change membranes and clean filters, which eliminates complex and time-consuming preparations, and are widely used in laboratories.

Guidelines for selection of Syringe filters and filter membranes

Selecting different kinds of filter membranes with different pore sizes to filter the mobile phase and samples can clarify and remove bacteria and impurities. It is of great significance for the protection of chromatographic system and chromatographic column.

Housing of syringe filter

High-pressure polypropylene (PP) has high-temperature resistance, no leakage, no need to change membranes and clean, and the preparation work of eliminating complicated and time-consuming is to filter small sample products of high-performance liquid chromatography and GC.

Selection of filter specifications

13 micron and 25 microns are commonly used, i.e. 13 microns is selected for a sample volume of 2-10 ml and 25 microns for a sample volume of 10-100 ml.

Introduction And Selection Guide For Syringe Filters

Brief Introduction And Performance Of Sample Vial

Sample vial produced by Hawach Scientific is suitable for high precision laboratories with high requirements and particularly fit for storing laboratory samples.

Actually, Hawach Scientific owns a strong team of technical after-sales service and strict quality management procedures, which aims to provide customers with first-class product quality and good production efficiency.

Special design in sample vials can remove the human factor, provide customers with the ideal confidentiality and consistency, and avoid over-tightening. Our sample vials are sold all over the world network of distributors and support a full range of our business.

Performance of Sample Vial

Sample vial provided by our company is noted for good performance, there is some brief description of it. All the sample vials are packaged in an independent box which is designed to reduce sample bottle damage and contamination; precision molded neck can improve auto-sampler processing; strict quality assurance provides dimensional consistency from batch to batch; wide warranted compatibility can match various auto-sampler; crimp caps offer a tight seal to reduce the possibility of sample evaporation; and pre-assembled caps can avoid accidents occurred from liquid spatter.

Brief Introduction And Performance Of Sample Vial

Partition Chromatography of Flash Column

The partition chromatography of flash column implements the separation by using the difference of components’ solubility between the immobile phase and mobile phase.

Commonly, the immobile phase is liquidus solvent. It uses bonding and adsorption to distribute in the flash column or the surface of the supporter. In fact, the process of partition chromatography is a process in which the components continue to reach solubility equilibrium between the immobile phase and the mobile phase.

In general, the carriers of liquid-liquid partition chromatography mainly include silica gel, infusoria earth, and cellulose. Normally, when we separate water-soluble components or components with strong polarities, such as natural base, glycoside, saccharides, and organic acid, we mostly take solvents with strong polarity, including water and buffer solution, as the immobile phase. As for the mobile phase, we often use formyl trichloride, ethyl acetate, and butyl alcohol. On the whole, this is called normal-phase chromatography of the flash column.

On the other side, when we separate fat-soluble chemical compounds, such as higher aliphatic acid, grease and free steroidal, we can take paraffin oil as the immobile phase. Relatively, we take solvents with strong polarity including water and methyl alcohol, as the mobile phase. This is called reverse-phase chromatography of the flash column.

Partition Chromatography of Flash Column

Working Principle of Membrane Filter

Membranes filters are used for the separation and enrichment of solutes in solution, and also for the separation of colloidal suspensions.

Water flow through the membrane is not very fast, so in order to pass the required amount of water, the monomer area of the membrane device should be large, and many thin membrane tubes should be filled in a small space. In addition, the film with a thickness of less than 100um must have the ability to withstand high pressure, so we should try to make various kinds of pressure-resistant films.

There are five types of the membrane filter: plate-frame type, spiral type, bridge type, tubular type, and hollow fiber type. Porous materials should be used for the plate-and-frame membranes. The spiral type is coiled, and the bridge type is to insert a large area of the membrane into a small folded volume.

Tube membranes also need porous materials. Raw water passes through the inner side of the pipe and seepage flows out of the pipe. This kind of membranes is commonly used for passengers, but also for externally pressurized ones. The outer diameter of the hollow system is several hundred um, and most fiber tubes are packed in the system.

Working Principle of Membrane Filter

Why the Pipette Cannot Suck Properly

There are several reasons for the pipette’s failure to suck properly.

Firstly, we can install the original suction head on the pipette to test the function. If the pipette with the original head can work normally, there is no problem with the pipette. The reason may be the leakage of air caused by the mismatching between the suction head and the pipette.

Secondly, if the pipette is always equipped with the same suction head and cannot suck properly suddenly, the problem is not the suction head. It is very likely that the pipette has not been maintained for a long time. What we can do is removing the suction head thrust ring, suction head conical sleeve and other parts of the pipette, wiping the piston with alcohol, and removing all kinds of dirt.
And then we can apply the silicone grease to the piston part, re-install the unloaded parts and press the operation button to distribute the silicone grease on the piston to the sleeve. Finishing above, the pipette can be used normally.

Thirdly, if the pipette cannot be used normally after maintenance, the parts of the pipette may be damaged.

Why the Pipette Cannot Suck Properly

To List The Advantages Of QuEChERS

Development stages

Traditional sample processing techniques have undergone several stages of liquid-solid extraction, liquid-liquid extraction, and solid-phase extraction.

In 2003, based on the experience of these extractions, FDA chemists invented a method for effectively separating trace amounts of pesticide residues in various fruits and vegetables. Combined with the high sensitivity and selectivity of liquid quality and temperament, QuEChERStechnology has been greatly developed.

Advantages of QuEChERS

The QuEChERS method has the following advantages:
1. High recovery rate: recovery rate of a large number of polar and volatile pesticides greater than 85%;
2. High accuracy: it can be corrected by the internal standard method;
3. A wide range of analyzable pesticides: including polar and non-polar pesticides and capable of obtaining better recovery rates;
4. Fast analysis: complete 6 samples in 30 minutes;
5. Solvent efficient, low-polluting, low cost, and excluding the chloride-containing solvent;
6. Easy operation: it can be well completed without good training and high skill;
7. Fewer contact with working staff: the acetonitrile is sealed immediately after being added to the container;
8. Simple structure: few glassware are used in the sample preparation process.

To List The Advantages Of QuEChERS