Selection For Filter Membrane: NYLON Or PDVF?

The first kind of membrane material is nylon. It has good temperature resistance and good chemical stability. The nylon membrane can withstand disinfection by saturated steam at 121℃ for 30 minutes, and its highest working temperature is 60℃.

And on the other hand, it can withstand many organic and inorganic compounds, such as dilute acid, dilute alkali, alcohols, esters, oils, hydrocarbons, halogenated hydrocarbons, and organic oxides.

The nylon filter membrane is applied to many industries. It may be used for the water filtration in the electronic, microelectronic and semiconductor industry, filtration of tissue culture medium, filtration of drug solution, beverage, and high purification chemical products, and filtration of aqueous solutions and organic mobile phases.

The other is PVDF. This kind of membrane has high mechanical strength and high tensile strength. More than this, it has good heat resistance, good chemical stability, low protein adsorption rate, strong negative static electricity, and hydrophobicity. The membranes have two forms: the hydrophobic one and the hydrophilic. However, it can’t tolerate acetone, DMSO, THF, DMF, dichloromethane, and chloroform.

Hydrophobic PVDF filter membranes are mainly used in gas and steam filtration and high-temperature liquid filtration. Hydrophilic PVDF membranes are mainly used in tissue culture media, additives, and other bactericidal filtration solvents and the filtration of the essence of chemical raw materials, sterilizing of reagents, filtration of high-temperature liquids, etc

.Selection For Filter Membrane: NYLON Or PDVF?

Operation And Tips For Management of HPLC Columns

Operation of HPLC Columns

In daily separation analysis, it is significant to properly use column, or the service life of the column efficiency of it can be directly affected. In the course of column loading, unloading or replacement, strong mechanical vibration should be prevented so as not to produce gaps in the column bed.

If the column is used for routine analysis, a special column may be arranged for each kind of conventional analysis to prolong the life of the column.

Additionally, avoid sharp changes in pressure and temperature, because the sudden temperature will affect the filing condition of the column and urge the packing in the column. And the rotation of the valve should not be too slow when the valve is injected.

Tips for management of HPLC Columns

Generally speaking, Hawach HPLC columns cannot recoil, only when the producer indicates that the column can recoil, the impurities left in the column can be removed by recoil.

Otherwise, the recoil will quickly reduce the column performance. It the pressure increases in the operation process, the firing filter may be blocked, the filter should be replaced or removed for cleaning.

Operation And Tips For Management of HPLC Columns

Hawach C18 SPE Cartridge

Hawach C18 SPE cartridge is a sample pre-treatment device mainly used for extraction, separation, and concentration. It is mainly applied in the pre-treatment process of the compound contained in food, agricultural and livestock products, and biological products.

Operation Principle

The solid-phase extraction technique is a separation and purification process of samples by adopting the selective adsorption and elution method, which is based on the liquid-solid phase chromatography theory.

Commonly, the sample solution needs to pass through the adsorbent first during the use of the C18 SPE cartridge. In this way, the substance under test could be retained. Secondly, to wash out the impurity with a moderately strong solvent and elute the sample quickly with a small amount of solvent. Thereby, rapid separation and purification could be achieved.

Application

The C18 SPE cartridge is quite suitable in the water analysis, especially in the pre-treatment analysis of the pesticide residue, organic substance, phenolic compounds contained in water. In the analysis of residual pesticide, the methanol is often used as eluent.

As for the determination of organic substance, it requires immediate analysis as long as it is sampled to the vial due to its instability. For the analysis of phenolic compounds, it employs tetrahydrofuran as eluent.

Hawach C18 SPE Cartridge

Tips For Pipette Operation

Here are as follows：

1. The pipette should not be dried in the oven.

2. The pipette should not remove the too hot or too cold solution.

3. The same pipette should be used as far as possible in the same experiment.

4. After the pipette is used, it should be washed with tap water and distilled water immediately and placed on the pipette rack.

5. Pipette and volumetric bottles are often used in conjunction with each other, so the relative volumes of both pipettes and volumetric bottles are often calibrated before they are used.

6. In order to reduce measurement errors when using the pipette, the solution of the required volume should be lowered from the top scale (0 scales) at each time, instead of absorbing as much volume as needed.

7. There are old and new pipettes. The old Pipettes are marked with the word “blow”. It is necessary to use ear washer to blow out the residual liquid in the orifice of the pipettes. The new style does not exist. Never blow out the residual orifice, otherwise, it will cause excessive liquid withdrawal.

Tips For Pipette Operation

Multi-branch Vacuum Filtration

Hawach Scientific co., LTD. is a professional technology company integrating analytical chemical product development, manufacturing, sales, and service. Company since its inception, has been to maintain the stability of the pace of development, the scientific and technological innovation, to provide customers with more valuable products at the core of the concept, fully depending on the use of production, continuous improvement, strive to build to become a high-tech enterprise in the industry with global influence.

Multi-branch Vacuum Filtration is designed and manufactured for the simultaneous filtration of multiple samples. At present, domestic laboratories generally adopt glass material sand core filtration device when filtering solutions. This method can only filter one sample at a time, with slow filtration speed, low efficiency, and high labor intensity.

For operators who need to filter multiple samples simultaneously, it is more convenient to use multiple filters. Since each filter rack has an independent control valve, only one vacuum pump is required to support the single or multi-link simultaneous operation. Stainless steel multi-link filter bracket is designed for filtration operation at 180℃; Aluminum alloy clamps are reasonably and tightly designed to fit the filter cup and the middle filter head together and ensure strict sealing without leakage.

At the same time, 316L sanitary grade stainless steel material is acid and alkali resistant, corrosion-resistant, easy to high-temperature disinfection, so that the analysis results are more stable and reliable.

Features:
1. Each bracket is equipped with independent control valve, which is flexible to use, convenient to sterilize and efficient.
2. It can detect three or six samples at the same time, with high sensitivity, low probability of false-positive and simple operation.
It is widely used in chemical analysis, biochemical pharmacy, sanitary inspection, environmental inspection, water quality analysis, food, beverage, scientific research and so on.

Multi-branch Vacuum Filtration

About The Establishment Of QuEChERS Method

Before QuEChERS born

In 1989, Barker et al. first proposed a matrix solid-phase dispersion (MSPD) technique for simultaneously dispersing and extracting solid and semi-solid samples. The method grinds a solid-phase extraction material coated with various polymers such as C18 with a sample, and packs it as packing, and elutes various analytes with different solvents.

The technology concentrates the process of sample homogenization, extraction, purification, etc. in the traditional sample pretreatment; reduces the steps of tissue soaking, sedimentation, centrifugation, pH adjustment, and sample transfer. The loss of the sample is avoided, and it is gradually widely used in various fields.

QuEChERS born

In 2003, the US Department of Agriculture Food and Drug Administration and the Slovenian Institute of Public Health jointly developed a new sample pretreatment technology based on MSPD technology. Anastassiades and Lehotay proposed solid phase extraction and matrix solid phase dispersion technology.

The detection method is a sample pretreatment technology which is quick, easy, cheap, effective, rugged and safe, called the QuEChERS method. It is essentially the combination and derivation of solid phase extraction and MSPD technology.

Buffered QuEChERS

In 2004, in order to improve the recovery rate of certain alkali-sensitive pesticides, Lehotay et al. proposed a buffered QuEChERS method, in which acetonitrile containing 0.1% acetic acid is used as an extract, and anhydrous sodium acetate is used as a salting-out agent.

About The Establishment Of QuEChERS Method

Application Of Qualitative Filter Paper On Engine Oil Detection

For some vehicles, especially the ones beyond the warranty period, lots of owners prefer to decide the oil change cycle by themselves. The qualitative filter paper test method is a simple way for people to determine a reasonable oil change interval of the oil.

Testing Method

First of all, make sure that the temperature of the engine oil is as high as the outside temperature. And then use an oil dipstick to extract the oil and drop it 1-2 drops in the middle of a piece of qualitative filter paper. Next, the filter paper should be put on an empty container (cup) horizontally. The last step is to leave it for 24-48 hours and then to observe the oil spot and judge the oil life.

Result Analysis

There are mainly three annular areas shown on the filter paper in the test result, including diffusion ring (the center circle spot), deposition ring (the one next to diffusion ring), and oil ring (the peripheral ring of the deposition ring).

If there is no obvious boundary between the diffusion ring and deposition ring and their color is uniformly distributed, it means the engine oil is good enough to continuously used.

If the color of the deposition ring is deeper and the diffusion ring is wider while the oil ring is in different shades of yellow, that indicates the oil has been contaminated yet still usable. If the deposition ring is in deep dark with dense sediments and the diffusion ring is narrower while the color of the oil ring is deeper, or there is no longer a diffusion ring, it means the engine oil has to be changed.

Application Of Qualitative Filter Paper On Engine Oil Detection