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1. Syringe Filter

1.1 What are 4 mm and 50 mm syringe filters different from others?
For 4mm, Filter sample volume is less than 1ml, its low adsorption capacity to ensure the maximum sample recovery rate, and used HPLC samples with low solid content, capillary electrophoresis of biological samples.
For 50mm, both inlet and outlet is 7~13 mm stepped hose barb connection with 6:100 Luer slip, more suitable for gas filtration.
13mm, 25mm and 33mm syringe filters are the most regular and widely used diameter with great market demands and welcome your inquiry anytime.

1.2 What is the relationship between the important technical parameters of Syringe filter?
The greater the diameter of the filter, the greater the filtration area it will have with the sample size larger.

2. Membrane Filter

2.1 What do the terms ''hydrophilic'' and ''hydrophobic'' mean in the filtration industry?

Hydrophilic filters are easily wet with water. Hydrophilic filters can be wetted with virtually any liquid, and are the preferred filters for aqueous solutions, as appropriate by compatibility. Once wetted, hydrophilic filters do not allow the free passage of gases until the applied pressure exceeds the bubble point and the liquid is expelled from the pores of the membrane.
Hydrophobic filters will not wet in water but will wet in low surface tension liquids, for example, organic solvents such as alcohols. Once a hydrophobic filter has been wetted, aqueous solutions also will pass through. Hydrophobic filters are best suited for gas filtration, low surface tension solvents, and venting. In certain applications, hydrophobic filters are used to filter aqueous solutions because of compatibility requirements. Water or aqueous solutions can also pass through a hydrophobic filter once the water breakthrough pressure is reached.

2.2 Do you have Sterile membrane filter? What's the main usage for it?
Yes, there's sterile single packed MCE gridded membrane filter in supply.
Sterile, gridded cellulose mixed ester membrane filters are widely used for routine microbiological quality control, colony counting, particle testing, microscopy and sterility testing. the membrane filters are ready-to-use and each filter is individually packed, offering highest security whilst saving preparatory time. The various filter colors allow the best possible contrast to the colonies for easy and reliable quantification and identification.

2.3 What is the difference between pore size and porosity?
The pore size of a membrane refers to the size of the "holes" in the filter media.

Porosity of a membrane is the number of or percentage of pores contained in a filter.

3. Glass Vials

3.1 Can glass vials be frozen and what do you need to know?

Most glass vials can tolerate temperatures down to -4˚C, a common temperature for shortterm storage of test samples without requiring special precautions.

A glass vial containing mostly organic solvents can be stored at temperatures as low as -80˚C.

However, extra care should be taken with vials and closures made from polypropylene since these materials become increasingly brittle at temperatures below 0˚C.

3.2 GC/HPLC Vial Septa Selection Guide

Optimise performance and results by choosing the right septum for your application:
3.2.1 PTFE Septa
Exceptional solvent resistance;
Only suitable for single injection use – not recommended for sample storage before or after injection;
Not resealable;
The most economical septa;
Maximum service temperature 260°C.
3.2.2 PTFE/Silicone Septa
Excellent resealing capabilities – highly recommended for multiple injections and sample storage;
Autoclavable and excellent resistance to coring;
PTFE chemical resistance until pierced then the septa will have the compatibility of silicone;
Temperature range -40°C to 200°C;
Pre-slit PTFE/Silicone Septa;
Reduces the possibility of coring with blunt tipped needles or for applications using a thin gauge needle;
Used to prevent vacuum from forming inside the vial;
Temperature range -40°C to 200°C.
3.2.3 PTFE/Silicone/PTFE Septa
Recommended for multiple injections due to above average resealing capabilities;
Autoclavable and excellent resistance to coring;
Recommended for demanding applications such as internal standards, trace analysis or applications where there will be a long time between injections;
Temperature range -40°C to 200°C.

4. Vacuum Filtration

4.1 How to choose the membrane filter for vacuum filtration?
The selection of the membrane is the key to achieve the best filtration effect. The material must be suitable the different characteristics of the filter medium and has to be chemical resistant against it. PTFE is the best choice with diameter of 47mm or 50mm.

4.2 What should be paid attention to when using vacuum filtration?
Depending on the different characteristics of the solutions, choose the suitable membrane filter between the funnel and the filter head, align the ground part and fix with clamp.

Press the switch to start the pump, put the solwent into the funnel to filter.

When filtering prevent overloading the collection bottle. Solvent into the pump may be hazardous or can damage the pump.

If there is leakage between filter head and funnel, please check wether ground part is align and the membrane is flat, if the clamp is fixed and proper seated.

When the flow rate decreases, check whether there are excessive impurities on the membranes affecting the filtration speed and please replace the membrane filter if required.

The solvent filtration apparatus is fragile cargo, please do not move it entirely, and avoid taking the clamp to move.

5. Flash Column

5.1 How to choose a right flash column?

Should be selected from the application, filter, seasoning particle size and filter area.

5.2 What is gradient elution? In what case gradient elution was used?

In order to improve the analysis results and some operations need to continuously changing the mobile phase the solvent ratio of the components in a continuous change in the polarity of mobile phase, the analysis of each component have the appropriate capacity factor, K, and the variety of all groups can in the shortest time to achieve optimum separation. The elution mode known as gradient elution.
Gradient elution can play an important role in the following situations:
Analysis of a variety of samples with a wide K value at the degree of large molecular sample analysis.
Samples containing strong retention of interferents, a peak in the target compound set the gradient elution and disruptors eluted, so as to avoid the effect of data collection in the next time.
Analysis method is established, do not know its elution situation, use the gradient elution, find out the better elution conditions.

6. Filter Paper
6.1 what's the ash content for filter paper?

Our qualitative filter paper are manufactured from high quality cotton linters with ash content of less than 0.1%, while quantitative filter paper are acid washed qualitative filter paper with ash content less than 0.01%.

6.2 What's the advantages of cotton linters filter paper?
Strong and higher loading capacity; good heat resistance(140 degree) and chemical compatibility; can be fold and ashed.

6.3 How do filter papers work?
Filter papers are actually depth filters. Various parameters influence their effectiveness: Mechanical particulate retention, absorption, pH, surface properties, thickness and strength of the filter paper as well as the shape, density and quantity of particles to be retained. The precipitates deposited on the filter form a “cake layer”, which – depending on its density – increasingly affects the progress of a filtration run and decisively affects the retention capability. For this reason, it is essential to select the right filter paper to ensure effective filtration. This choice also depends on the filtration method to be used, among other factors. In addition, the amount and properties of the medium to be filtered, the size of the particulate solids to be removed and the required degree of clarification are all decisive in making the right choice.

7. HPLC Column
7.1 What's high performance liquid chromatography (HPLC)?

High performance liquid chromatography is now one of the most powerful tools in analytical chemistry. It has the ability to separate, identify, and quantitate the compounds that are present in any sample that can be dissolved in a liquid. Today, compounds in trace concentrations as low as parts per trillion may easily be identified. HPLC can be, and has been, applied to just about any sample, such as pharmaceuticals, food, nutraceuticals, cosmetics, environmental matrices, forensic samples, and industrial chemicals.

7.2 What's the cleaning procedures for HPLC column?
The following general procedures are recommended for regeneration of column performance:
1. Disconnect and if applicable reverse the column.
2. Connect the column to the pump, but not the detector.
3. Follow the appropriate flushing procedure for the type of column, using 10-20 column volumes of each solvent. Always make sure that the last solvent used will be compatible with the mobile phase.
4. The flow rate should not exceed that specified on the QC chromatogram for the particular column, but preferably should be maintained at 25-50% of the normal working flow rate.

7.3 What's the storage conditions for silica based HPLC columns?
The conditions under which a column is stored will affect its lifetime. All buffers, salts and ion-pairing reagents should be flushed from the column before storage. Ideally, the storage solvent should be as shown on the initial column test chromatogram provided by the manufacturer. Column end plugs should be fitted to prevent solvent evaporation and the subsequent drying out of the packing bed.

8. SPE Cartridge
8.1 What's the steps of a solid-phase extraction procedure?

The following section describes the steps involved in a complete solid-phase extraction procedure. In many applications, one or more of the steps, listed below and subsequently described by general examples, can be omitted, thereby simplifying the procedure. The procedures illustrated here use samples containing dyes so that separations may be easily visualized. Keep in mind that most samples contain colorless components that require some type of detector or test to locate them in the collected fractions. Use the following information as a guideline in the development of your own procedure or when modifying procedures published in the literature.
1. Pretreatment of the sample
2. Conditioning of the cartridge
3. Loading the sample
4. Elution of the fractions

8.2 What's the classification of SPE cartridges?
According to principle of reaction, SPE is divided into the following three categories.
1. Normal-phase extraction- Adsorbents used in normal phase extraction are polar.
2. Reversed-phase extraction- The sorbent and the target analytes by reversed-phase extraction is usually the non-polar or weak polar, relying mainly on non polar and non polar interactions, is a fan of Edward force or dispersion force.
3. Ion exchange extraction is relying on the interaction between target analytes and sorbent.