Common Faults And Troubleshooting Methods In HPLC Column

 The hardware of the HPLC column includes the column tube and fittings which contain the chromatographic packing material used for the effect of the separation. The hardware not only needs to strong enough to stand back-pressure in the process of separation, but also needs to be well-controlled, acting leak-free, minimum-volume, and zero-dead-volume. It provides a flowing path for the sample at the inlet and the analyte bands at the outlet。

The hardware of the HPLC needs to be chemically inert relative to the separation system, including sample, mobile, and stationary phases. The columns which are made of stainless steel have the character of the highest pressure resistance. If you need to complete the special chemical or biological applications, where the inert surfaces are required, the engineered plastic and glass columns with less pressure tolerance, will be the better choice.

The chromatographic resolution shows the degree of how two compounds are separated. The ability of mechanical and chemical separation of the HPLC column are the key factors to determine the separation. The ability of mechanical separation is created by the length, particle size, and packed-bed uniformity of the HPLC column. The ability of chemical separation is created by the physicochemical competition for compounds between the packing material in the column and the mobile phase.

Operating Conditions of HPLC Column
HPLC column is preferably constant temperature and humidity. The temperature is between 15-30 degrees Celsius, relative humidity is less than 80%, the room should be well ventilated, and air flows generated by air conditioning or other equipment do not directly below the instrument. What’s more, it is better to avoid direct light, stay away from high electrical interference and high vibration equipment.

Common Faults and Troubleshooting Methods in HPLC Column

One common fault is that HPLC column pressure is too high. In this situation, the following methods can be adopted:
1. Remove the protective column, see if the column pressure is still high, otherwise it is the protection column problem, if column pressure is still high, re-check;
2. Take the column from the instrument, if the pressure is still not down, it is pipe blocked, to be cleaned, if the pressure drop, the column inlet, and outlet in turn connected to the instrument, with 10 times the volume of the column flow phase washing column, if column pressure still not down, re-check;
3. Replace the column inlet sieve plate, if column pressure drop, indicating that the solvent sample contains solid particles if column pressure is still high, can be connected between the sampler and the protective column on-line filter.

Another problem is that baseline is instability, fluctuation, or drift, in this situation, the following methods can be adopted:
1. The mobile phase has dissolved gas, ultrasonic degassing can be used for 15-30 minutes;
2. single-way valve blockage can remove the ultrasonic plug;
3. There are leak points in the system, determine the leak location and repair;
4. Column balance is slow, especially when the mobile phase changes, it can be washed with a medium strength solvent. When changing the mobile phase, it is washed with 10-20 times the volume of flow relative column before analysis.

Common Faults And Troubleshooting Methods In HPLC Column

SPE Cartridge: The Essential Tool For Sample Preparation

 To isolate a species in a sample or to clean-up a sample before analysis, the solid phase extraction (SPE) is called the sample preparation technique which uses a solid adsorbent to adsorb select species from solution. The solid adsorbents are usually contained in a cartridge device, or on a disk. The goal of the solid phase extraction is to remove interferents in the matrix from the analyte and put out a solution that contains primarily analyte.

When the sample going through the SPE cartridge or disk very slowly, you can find that the analyte and some of the sample matrix compounds will be retained on the SPE material. The awash solvent that we have selected can remove components from the SPE sorbent and retain others at the same time, according to the properties of the analyte and the SPE sorbent.

SPE is pretty advanced in the way of simplifying complex sample matrices and purifying compounds of interest. It performs perfectly when fractionating complex mixtures for analysis by classification, and concentrating analytes present at low levels too.

Good Retention for Polar Compound

Hawach scientific normal phase CN SPE cartridge is of strong retention for polar compounds in samples or compounds with similar structures. Hawach normal phase CN SPE cartridge has excellent sample load ability and wide elution volume, which makes it can be applied in different conditions such as in normal phase and reversed phase adsorbents. Moreover, it provides the strongest polarity among sorbents in the normal phase and fits for separating compounds in various samples.

Separation Mechanism of Normal Phase CN SPE Cartridge

Hawach Scientific normal phase CN SPE cartridge is a process in which polar substances are dissolved in non-polar solvents, and adsorbed through a strongly polar stationary phase. The interaction between the two forces includes dipole pairs, hydrogen bonds, and electron pairs. Common adsorbents are alumina, magnesium silicate, diatomite, and silica gel.

Additionally, it can adsorb the target compounds in liquid samples, separate them from the matrix and interfering compounds, and then eluent them with eluent or heat desorption to achieve the purpose of separating and enriching the target compounds. Because of its safety, high recovery rate, good reproducibility, easy to operate, fast, wide application range, easy to realize automatic operation, and so on.

Activation of SPE Cartridge

If the cationic column of the polymer matrix is used, it can be directly sampled without activation. If the cationic column of silica gel matrix is used, the activation is to open the carbon group chain bonded on silica gel and make it fully effective. Methanol is to dissolve with the carbon chain, and excessive water is to dissolve the sample solution.

When you perform SPE cartridge, the first step you should do is to pre-treat the sample, such as dilution and PH adjustment. The second step is to condition the cartridge by running water or solvent through it. After that, it is time to load the sample and elute the fractions.

SPE Cartridge: The Essential Tool For Sample Preparation

The Use Of Membrane Filter

 During the experiment, there were some problems. It was thought that the original sample might be too dirty, which caused the collapse of the sieve plate. Is there a problem with membrane selection? Stuffed heart! It is not clear what is right or wrong. The only way to protect the chromatographic column and liquid injection system is to continue to strictly control the sample pretreatment.

For analysis, sample pretreatment is not only an essential link but also a technical work. Regardless of ultrasound or oscillation, the liquid phase system should be filtered after the solution of the main drug is guaranteed. The role of membrane filter is very important. Today we’re going to talk about membrane filter.

What is the most important function of the membrane filter? Analyze the door of the system and its protective effect. The microporous membrane is made of polymer chemical material, and the porous additive is applied to the support layer after special treatment.

Tips for using syringe filters

Syringe filter is the most commonly used for dissolution and liquid phase sample pretreatment. A day does not know how many times, small make up today to tell some of the tips that we usually pay little attention to.

Before inhaling the sample, suck about 1ml of air into the syringe to minimize liquid residue. Inhale the sample into the syringe, invert the syringe, wipe the residue on the top, connect the syringe filter to the syringe, and gently tighten to ensure good sealing. Filter the sample in the syringe and inject it into the bottle. Remove the filter, inhale the air into the syringe, reconnect the filter head, and press the pushrod to filter out all residual samples. Maximize sample recovery.

Tips: During the filtration process, it is better not to use a syringe less than 10ml to avoid liquid leakage caused by excessive pressure.

Design of membrane filter adsorption test

The membrane filter should be inspected before use to determine whether it has an adsorption effect on the measured components. No matter the dissolution, or the content, or the relevant substances, if the membrane filter has an effect, it will lead to the subsequent output results are wrong. Whatever the drug’s structure, it is always right to examine it before the trial begins. According to different analyses and test items, the determination of membrane filter adsorption and verification methods are slightly different.

Determination of dissolution

Before the dissolution test, the membrane filter adsorption test must be carried out.

The membrane filter adsorption test method is as follows: take the reference solution and compare the absorbance/peak area value after direct injection without filtration and filtration according to the prescribed method. Or the use of raw materials and blank auxiliary materials to configure the solution. High speed centrifugation and membrane filter were used respectively.

The absorbance/peak area of the centrifugal supernatant and the filtered solution were compared. The primary filtrate of different volumes was discarded. The above methods are for reference only, different operation methods of actual projects are different, please adjust them according to the actual situation.

The Use Of Membrane Filter

Function, Classification, And Selection Of Syringe Filter

 Syringe filters are divided into organic and water systems. What are they used to filter? The syringe filter structure has two parts, housing, and membrane, which can be made of different materials. Usually, housing is polypropylene pp or nylon polyamide. Polypropylene has stable properties and is resistant to various solvents.

The so-called water system/organic system should be classified according to the material of the filter membrane, which is suitable for filtering aqueous solutions (for life sciences) and organic solutions (for chemistry). The so-called organic system should be used to filter aqueous solutions without any problems, but the water system may be dissolved by organic solvents, which is not suitable for the filtration of organic systems.

Classifications

Common filter membranes have pore diameters of 0.22 micron and 0.45 micron. The diameter of the filter is 1.0, 1.3, and 2.5 cm. It is used with disposable syringes and needles. It is placed between the two and the interface is standard, which is commonly used to process HPLC samples.

The price of syringe filters is divided into one-time and multi-time, organic or water-based, the specifications are Φ13 or Φ25, used for sample filtration in liquid or gas phase analysis. Filter materials include nylon (Nylon), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), mixed cellulose (MCE), cellulose acetate (CA), glass fiber, polypropylene ( PP), polyethersulfone (PES).

Selection method of syringe filter

1) Hydrophilic samples: select hydrophilic membranes, which have an affinity for water and are suitable for filtering water-based solutions. Available filter membranes are mixed cellulose ester, polyethersulfone (PES), etc.

2) Strongly corrosive and aggressive organic solvents (Properties: transparent, colorless liquid): generally use hydrophobic membranes, such as PTFE, polypropylene (PP), and other material quality filter membranes.

3) Protein solution: Choose a membrane with low protein adsorption, such as PVDF membrane. The microporous filter membrane is made by using polymer chemical materials and applying pore-forming additives on the support layer after special treatment. To be used for the filtration of water-based solutions, it is also called a water-based membrane.

4) Ion chromatography: PES filters are generally considered to be more suitable for filtration of solutions with low inorganic ions.

In addition to considering the above factors, the volume of the sample should also be considered. Generally, when the sample size is less than 2ml, a 4mm diameter microfilter is used; when the sample size is between 2-10ml, a 13mm diameter filter is used.

When the sample size is greater than 10ml, choose a 25mm diameter filter. The microporous filter membrane is made by using polymer chemical materials and pore-forming additives after special treatment and smearing on the support layer.

Customized Spray Dryer

 

Vacuum spray dryer

In addition to small spray dryer and centrifugal spray dryer, Hawach also has anhydro spray dryer for you choose. Hawach as a leading spray dryer equipment manufacturer, we also supply other high speed centrifugal spray dryers, include vacuum spray dryer, organic solvent spray dryer, anhydro spray dryer, and other spray dryers, which could especially solve the problem of spray dryer for heat sensitive materials.

Hawach’s spray dryer machine price is really competitive, now we have clients from many countries. In so many spray drying equipment manufacturers, Hawach is special because we always keep our original intention, that is: Providing customers with the most perfect equipment and services.

Key features of anhydro spray dryer:

1. Vacuum spray dryer could bear low spray drying temperature (50-130 centigrade), which solves the problem of spray drying for heat sensitive materials.
2. Anhydro spray dryer has an LCD touch screen with Chinese-English operation panel,
3. Sprayed granule with normal distribution and good mobility, so the noise is low.
4. Two fluid sprayers made from stainless steel precision components with integral design, which make this high speed centrifugal spray dryer easy to use and clean.
5. Real-time PID temperature control with a precision of 1 centigrade.
6. The peristaltic pump adjusts the feeding volume.
7. Automatic needling with speed adjustable, which ensures the efficiency and continuity of the experiment.
8. Compact design in the vacuum spray dryer, easy to use, and move.
9. Nozzle: 0.5mm, 0.7mm,1mm, 1.5mm, 2mm optional.
10. spray dryer machine price is more competitive.

Customized Spray Dryer

Difference Between Molecular Distillation And Traditional Distillation Technology

 The difference between molecular distillation and traditional distillation technology? Molecular distillation can effectively solve many problems that traditional distillation techniques cannot solve, and improve the shortcomings left by traditional distillation techniques.

Molecular distillation technology improves the general distillation environment requirements. Since molecular distillation reaches a certain temperature difference, it can be separated at multiple temperatures. Traditional distillation requires strict requirements and can only be carried out after controlling the boiling point of the material.

Traditional distillation bubbling and boiling are relatively common, and it can also cause splashing or endanger the health of workers. Molecular distillation can evaporate freely on the surface of the liquid film, and the pressure required for operation is small. Molecular distillation can be easily done without these problems.

Molecular distillation technology is suitable for increasing types of materials, which is different from ordinary distillation. Ordinary distillation is only suitable for certain materials.

Different distillation time is required, molecular distillation heating time is short, in the actual application operation process, more cost savings, and the purification process is also higher.

How to achieve separation under low pressure by molecular distillation equipment

The molecular distillation separation process of low-pressure distillation of molecular distillation equipment during operation takes place between 0.01Pa and 0.1Pa. During operation, its distillation pressure can increase the average free path of the molecular movement of the compound, thereby expanding the average between the compounds. The difference in free path achieves separation.

It is generally in the traditional distillation technology is still kettle distillation, the compound to be separated is vaporized into a gas at the boiling point first, the gaseous compound is pumped out under the action of the vacuum pump, and it can be condensed when it flows through the condenser.

The long-distance between the condenser and the evaporation surface makes this distance full of gaseous compounds, making it difficult to reduce the pressure at the evaporation surface. For molecular distillation technology, due to the close arrangement of the condenser and the evaporation surface, once the compound to be separated volatilizes, it will be condensed, so the partial pressure of the gaseous compound between the condenser and the evaporator surface is low, and the separation of the compound at low pressure can be achieved.

Difference Between Molecular Distillation And Traditional Distillation Technology

Some Facts You Should Know When Selecting The Bottle-Top Dispensers

 Before you select the right bottle-top dispenser for your lab, there are 3 key facts you should know, chemical compatibility, viscosity, and volume. The compatibility of a chemical with a dispenser can be divided into four categories: acids, bases, solvents, and highly corrosive liquids. All models of Hawach bottle-top dispenser are made of the materials which have excellent chemical resistance and can be used very safely.

For viscosity, if the solution is highly viscous with a kinematic viscosity of between 75 and 500 mm2/second, you need to select the bottle-top carefully. Also, you need to pay more attention and pump the dispenser slowly for the applications.

The most popular bottle-top dispensers with an adjustable volume dispenser and you need to select a volume to dispense according to the volume range and the supporting volume increments.

Manual bootle-top dispensers are an excellent tool in the laboratory, but do you know what electric bottle-top dispensers can provide? There are 5 models for use bottle-top dispensers.

  

1. Greatly improved the ergonomic experience

Prolonged pipetting operations are often painful and may even cause repetitive strain injuries. With electric bottle-top dispensers, you no longer need to turn the knob or plunger to adjust the pipetting volume, and you can operate the piston with one key without pressing the plunger. Your thumbs, wrists, and hands will thank you for this!

2. Better precision and accuracy

Electric bottle-top dispensers use a motor to control the movement of the piston, so you can aspirate and dispense a preset volume accurately every time. The pipetting process (including volume and speed) can also be pre-programmed and saved on the bottle-top dispensers so that it can be executed in the same way every time. Since everyone uses the same pipetting procedure, it can greatly reduce human error and avoid differences between operators, so repeatability is better, and better repeatability means better results!

3. One part of the liquid container, four applications

An electric dispenser can complete the work of four different laboratory instruments. Such as standard pipetting, repeated dispensing, dilution, and titration procedures. a. Repeat dispensing mode, instead of repeat dispenser. b. Sample dilution mode, instead of diluter. c. Pipetting mode, instead of manual bottle-top dispensers. d. Manual pipetting mode, instead of the titrator.

Just select the appropriate program, you can use the same electric bottle-top dispensers to perform the above four applications.

4. Simple and intuitive calibration

The calibration of the electric bottle-top dispensers is simple and fast. You only need to verify the performance of the bottle-top dispensers (for example, through a weight test), and then enter the actual dispensing volume compared to the target dispensing volume, and the bottle-top dispensers will calibrate itself. The built-in calibration reminder function helps to comply with SOP requirements, which is especially important for GLP/GMP laboratories.

In addition, electric bottle-top dispensers can usually replace two manual bottle-top dispensers, because the motor can accurately, precisely, and repeatably control a shorter stroke distance, so it can complete a wider range with better performance pipetting within the measuring range. And if only one bottle-top dispenser needs to be maintained, the corresponding calibration time and cost will be reduced.

5. Simplify the complicated pipetting process

The pre-set program will prompt the user to input basic parameters, such as the volume of the liquid or the number of liquids, which can greatly reduce human error. Many electric bottle-top dispensers also allow users to create step-based custom programs to customize the entire process from start to finish.

Some Facts You Should Know When Selecting The Bottle-Top Dispensers

Hawach C8 Flash Columns, Always Ready For Your Separation Requirements

 Described as a “quick-and-dirty” method in literature, flash chromatography is a method of liquid chromatographic separation in the chemical and organic laboratories, especially when you seek for fast preparative applications. flash chromatography can be carried out with hands or with the appropriate equipment.

Flash column chromatography has become a common tool when separating fine chemicals since its description in the 1970s. Different from HPLC, in process of the flash chromatography, compounds will be separated on normal phases under low pressure. Therefore, flash chromatography is called as low-pressure or medium-pressure liquid chromatography.

If you compare flash chromatography with HPLC separation, you will find the flash chromatography more efficient and economical, in the way of saving both of your time and money. Different from HPLC, in process of the flash chromatography, compounds will be separated on normal phases under low pressure. Therefore, flash chromatography is called as low-pressure or medium-pressure liquid chromatography.

A flash chromatography system is perfect for precisely analyzing the separation peak by using a UV or IR detector. Due to the modular design, the flash column chromatography systems can be reconfigured too.

Twenty years ago, the first packed flash chromatography columns were marked as the big progress in the field of flash chromatography. Today, the legend is still helping us a whole new level of improving the quality and efficiency of the process of isolating a single chemical compound from mixed samples.

Packed with C8 reversed phase silica, Hawach C8 columns have an excellent resolution for critical separations. Compared with C18 columns, they can not only provide faster analysis but increase selectivity and reproducing ability as well. Hawach C8 columns which need marginally more polar phase than C18, have a high surface area. That factor can provide additional resolution to the polar phase.

As a kind of less hydrophobic column with high surface area, optimal carbon load, and unique bonded silica packing, Hawach C8 column is an ideal choice when analytical laboratories need extra selectivity and higher speed than the C18 column. These columns also can provide you the stable and reliable results with a long using-life, high silica gel quality, worldwide Luer fittings, and lowest cost for your lab.

Distribution Balance of Flash Column

Hawach flash column is a distribution method based on distribution balance. The chromatographic system consists of two phases, one is the stationary phase and the other is the mobile phase. When the two phases move relative, the difference in the distribution equilibrium properties of each component in the mixture is repeatedly used, and finally, the purpose of separating each other is achieved.

Chromatography has been invented for more than 80 years. It is a common method for purifying and separating organic or inorganic substances. The stationary phase polarity is larger than the mobile phase, and the opposite is reverse phase chromatography.

The activity of Adsorbent and Its Regulation

The adsorption capacity of adsorbents is often called activity. The adsorbent activity depends on how much of their water content and the most active adsorbent contains the least amount of water. The activity of adsorbent is generally divided into five levels, expressed by I、II、III、IV and V, respectively. The larger the number IS, the smaller the activity IS. Adding certain water to the adsorbent can reduce its activity; conversely, if some water in the adsorbent is removed by heating treatment, it can increase its activity, which is called the activation of the adsorbent.

Hawach C8 Flash Columns, Always Ready For Your Separation Requirements

HAWACH To Discuss How to Remove Residue And Make Full Use Of Pipettor

 A pipettor is a measuring tool that transfers liquid from the original container to another container within a certain range. Pipettor is often used for the pipetting of small or trace liquids in the laboratory, which is widely used in biology, chemistry, and other fields. Also, because of its simple basic structure and convenient usage, it is widely used in clinical laboratories.

Though the shapes produced by different manufacturers are also slightly different, the working principle and operation method are basically the same. Its basic structure mainly includes several parts such as a display window, volume adjustment part, piston, O-ring, straw, and suction head.

How to remove residue from the pipettor
We need to clean it thoroughly after each use, so as not to cause trouble for our next use, but sometimes we find that there are many residues that are not easy to remove. The method HAWACH discusses today will allow you to easily handle these residual liquids.

1. Remove the dropper injection sleeve
Gently hold the dropper ejector, insert the special tool provided by the pipettor, lock the mechanical structure, carefully loosen the dropper ejector, take out the dropper ejector and the sleeve.

2. Remove the dropper cone.
Use the provided special tools to carefully loosen the dropper cone counterclockwise with the wrench end; loosen the dropper cone counterclockwise by hand.

3. Disassemble the parts.
Remove the dropper cone, the suction pipe piston, and the spring. If a filter is installed, remove the filter.
4. The disassembled parts are immersed and disinfected.
Put the dropper cone, dropper thimble, dropper thimble sleeve, pipettor piston, O-ring, and spring into a beaker containing biological disinfectant and soak for at least 30 minutes.

5. Dry the removed parts.
Take out the dropper cone, the dropper thimble sleeve, and the straw piston from the beaker, rinse them repeatedly with distilled water and then dry them with hot air for more than 1 hour.

6. Maintenance and installation of various parts.
Re-apply lubricating oil to the suction cylinder piston according to the requirements of the operation manual, check other parts, and replace the wearing parts, such as replacing the new filter. Follow the reverse steps to reassemble the electronic pipettor.

After completing the cleaning and biological disinfection of the pipettor, pay attention to check the possible wear of the O-ring, check at least every 6 times, and replace if necessary, and calibrate the instrument after replacement.

How to make full use of the pipettor
1. Choose and use the right tip
To ensure better accuracy and precision, it is recommended that the pipetting volume is within the range of 35% -100% of the tip.
2. Installation of tips
For most brands of pipettors, especially multi-channel pipettors, installing the tip is not easy. In order to get good sealing, operators need to insert the pipettor handle into the tip and then tighten it by turning it left or right or shaking it forward. Some will use a pipettor to repeatedly hit the tip to tighten it, but this operation will cause the tip to deform and affect the accuracy. In serious cases, the pipettor will be damaged, so such operations should be avoided. Multi-channel pipettors do not have O-rings, operators can achieve the ideal seal with a single press.

3. Tip immersion angle and depth
The immersion angle of the suction head is controlled within 20 degrees of inclination, and it is better to keep it vertical. The recommended immersion depth of the suction head is as follows:

Specifications of pipettors	immersion depth of the suction head
2µL and 10µL	1 mm
20µL and 100µL	2-3 mm
200µL and 1000µL	3-6 mm
5000 µL and 10mL	6-10 mm

4. Tip cleaning
For normal temperature samples, the tip cleaning can help improve accuracy; however, for high or low-temperature samples, the tip cleaning can reduce the accuracy of the operation. Please pay special attention to it.

5. Pipetting speed
The pipetting operation should keep smooth and proper aspiration speed; excessively fast pipetting speed will easily cause the sample to enter the sleeve, damage to the piston and seal ring, and cross-contamination of the sample.

6. Tips for using pipettors
1) Keep the correct posture during pipetting; do not hold the pipettor tightly at all times, use a pipettor with finger hooks to help relieve hand fatigue; change hands frequently if possible.
2) Check the pipettor sealing condition regularly. Once the seal is found to be aging or leaking, the seal ring must be replaced in time.
3) Perform 1-2 corrections on the pipettor every year (depending on the frequency of use).
4) For most pipettors, apply a layer of lubricant to the piston before and after a period of use to maintain tightness. For regular range pipettors, they can have ideal tightness without lubricant.

HAWACH To Discuss How to Remove Residue And Make Full Use Of Pipettor

Advantages of QuEchERS Pre-Processing

The QuEchERS pretreatment method has been widely adopted by a number of international pesticide residue analysis organizations including the American Association of Official Analytical Chemists (AOAC) because of its simplification of complicated pretreatment steps and the expansion of the range of pesticide residues extracted application.

Due to the complexity of the veterinary drug sample matrix, the different chemical properties of veterinary drugs and pesticides, and many other factors, the application of the QuEchERS pretreatment method in the early stage of the veterinary drug residues was limited.

However, with the continuous exploration and improvement of the experimental method, it is gradually applied to the pretreatment of certain veterinary drugs in food. The QuEchERS pretreatment method combines the multiple steps of extraction, separation, and purification in the experimental process into one step, which greatly reduces It saves the consumption of reagents and consumables, and saves the energy and time of the operators and inspectors.

QuEchERS pretreatment method has a wide range of sample detection and can be applied to a variety of fruits and vegetables, cereals, plants and meat, and other foods. The relevant standards established by the European Union are used to determine the pesticide residues in plant-derived foods.

Anastasiades has also established a relevant website platform that introduces, promotes, and exchanges QuEchERS methods with analysts from various countries. Combined with the properties of various samples to be analyzed, and improved QuEchERS method for various specific matrices was developed.

The method of sample preparation for QuEchERS is mainly divided into two parts, extraction and purification. Acetonitrile is the most suitable solvent for extracting a wide range of polar and multi-residue drugs. For the detection of some drugs, acetonitrile or acetonitrile with a volume fraction of 1% acetic acid can be selected as the extractant. And add a specific ratio of anhydrous magnesium sulfate and sodium chloride or sodium acetate to remove the water in the extraction environment.

To promote the extraction of drugs. Sometimes it is necessary to add an appropriate amount of sodium acetate or sodium citrate to adjust the pH value. The extraction liquid obtained by the extraction is centrifuged and separated into layers and is purified by the method of dispersion solid phase extraction. Add an appropriate amount of anhydrous magnesium sulfate to remove excess water, add silica-based primary amine secondary amine bonded phase adsorbent (PSA) and C18 to purify complex matrix components, such as fatty acid, pigment, and carbohydrate interference.

The QuEchERS method has a good extraction effect when separating many types of drugs. Lopes et al. used the QuEchERS pretreatment method combined with triple quadrupole LC / MS detection technology to derivatize sulfonamides, quinolones, anthelmintics, avermectins, macrolides, and diamino in chicken samples. Many types of drugs with large differences in properties, including benzathine and benzathine penicillin, were tested and analyzed simultaneously.

This method has outstanding advantages such as short detection period, easy operation, high recovery rate, and saving reagents. This method also has the advantages of saving time and reagents. In summary, the QuEchERS method meets the requirements of modern analysis. In order to simplify and optimize the application of this method in the field of veterinary medicine, many researchers have improved and optimized the original method to improve the separation effect of drugs.

An improved pretreatment method of QuEchERS combined with high performance liquid chromatography tandem mass spectrometry detection method was used to detect the residues of tetracycline veterinary drugs in pork. The standard deviation is less than 7.7%, the method has high sensitivity, good repeatability, easy and fast operation. Using the improved pretreatment method of QuEchERS, the analysis and detection methods of 30 commonly used drugs in tea were established, eluting with acetonitrile containing 0.1% acetic acid and methanol (volume ratio 5: 1), the recovery rate reached 74%? 108%, the method sensitivity, precision, and accuracy all meet the testing requirements.

A pretreatment method for the analysis of 30 veterinary drug residues in fish meat was established. The sample was homogenized and then dispersed in water and extracted with nitrile. The results showed that the average recovery rate reached 63% -118% at the three-concentration spike level. It has high sensitivity and meets the testing requirements. Using QuEchERS pretreatment technology to establish seven kinds of sulfonamides in the chicken liver detection method, after extraction and purification of the DisQue extraction tube and purification tube, the recovery rate reached 70% -115%, the method is quick, simple, and easy to operate.

In terms of purifying agents, most analysts use anhydrous magnesium sulfate and C18 and also use PSA or anhydrous magnesium sulfate, C18, and PSA in different ratios. The veterinary drug base does not contain chlorophyll, so basically no GCB is used. Norli et al. Improved the pretreatment method of QuEchERS and established the detection method of 22 drugs in tilapia, salmon, and salmon. Due to the higher fat content in tilapia and salmon, a mixed reagent of 75% acetonitrile and 25% tetrahydrofuran extracted 22 kinds of drugs, the recovery rate has been significantly improved.

Advantages of QuEchERS Pre-Processing

Application And Use Notes Of Anti-Corrosion Diaphragm Vacuum Pumps In Laboratory

 Vacuum refers to a gaseous space with a pressure of less than 101.3kPa. Any device that can draw gas from the container to reduce the gas pressure can be called an anti-corrosion diaphragm vacuum pump. This kind of pump has a steel cylindrical stator. In the stator, there is an eccentric steel solid cylinder as the rotor. The diameter of the rotor is embedded with a sliding plate with a spring. When the motor drives the rotor to rotate, the sliding plate is in the cylindrical shape.

The pump cavity is divided into two areas, and its volume periodically expands and shrinks. After the gas container to be pumped is connected to the air inlet of the pump, when the pump chamber space increases, the gas to be pumped is sucked in. As the rotor rotates, the gas is compressed and discharged from the air outlet.

The rotor continuously rotates, the process of suction, compression, and exhaust is repeated continuously, the gas in the container is continuously reduced, and the air pressure is continuously reduced. The whole machine is immersed in a tank containing lubricating oil. The vapor pressure of the lubricating oil is very low. It plays the role of lubrication, sealing, and cooling.

Application
Anti-corrosion diaphragm vacuum pumps are mainly used in the following aspects in the lab
1. The vacuum drying vacuum pump is connected to the drying box, and the sample can be removed from the sample at a lower temperature in the vacuum drying box and the moisture and the high boiling point impurities that are difficult to volatilize, so as not to decompose the sample at high temperature.

2. Vacuum distillation or reduced pressure distillation can reduce the boiling point of the material and make it steam at a lower temperature. It is suitable for the steaming of organic matter that is easy to decompose at high temperatures.

3.Vacuum filtration: for special materials that are difficult to filter, vacuum filtration can speed up the filtration speed.

4. Others can also be used for tests that require a vacuum.

Use notes
1. Check whether the oil level in the pump is at the marked line of the oil hole before starting up. If the oil is too much, the gas will splash outward from the exhaust hole during operation; if the oil is insufficient, the pump body cannot be completely immersed, and the sealing and lubrication effect will not be achieved, which will damage the pump body.

2. Anti-corrosion diaphragm vacuum pumps are driven by a motor, and the power supply voltage should be consistent with the voltage required by the motor during use. For a three-phase motor, remove the belt before powering on and check whether the direction of rotation of the motor is consistent. Do not reverse the motor and cause the pump to spray out. After checking, connect the belt again.

3. Do not pump condensable vapor directly.

4. Pay attention to the temperature of the motor during operation, and it should not exceed the specified temperature. There should be no friction and metal impact. If there is any abnormality, stop the machine and ask a professional for repair.

5. Before stopping the pump, the air inlet of the pump should be vented to the atmosphere and then the power supply should be cut off to prevent the pump oil from returning pressure to the air extraction system. To this end, a three-way piston is connected to the air inlet, and the three-way piston is placed in a position that not only keeps the system in a vacuum but also vents the pump body to the atmosphere before stopping.

6. The fine gauze net at the air inlet should be cleaned regularly to prevent small solid particles from falling into the pump and damaging the pump body.

Application And Use Notes Of Anti-Corrosion Diaphragm Vacuum Pumps In Laboratory

Production Process And Siphon Principle of Extraction Thimble

 Hawach is committed to the development and production of chromatography consumables, who has advanced production technology, rigorous testing procedures, excellent after-sales service, and a professional R & D team.

The extraction thimbles are made of cotton fiber with high cellulose content according to international standard, with good mechanical strength and excellent retention capacity. It is especially suitable for the extraction of organic compounds in reaction mixtures, foods, natural substances, paints, and paints; binders in paints; powders and tars in gas, asphalt; and the determination of nicotine content. Hawach can provide you with two different extraction thimbles.

Manufactured from highest grade cotton cellulose fibers or 100% pure borosilicate glass binderless microfiber, Hawach extraction thimbles are the best tool to help you get the optimal analytical results. They provide a safe, efficient, and convenient way of solvent extraction of solids and semi-solids with a wide selection of dimensions that can fit most of the Soxhlet extractors. When you choose the extraction thimbles, you should consider the media and the size of the thimbles.

 

The Hawach cellulose extraction thimbles are made of the high alpha cellulose which has the factor of excellent mechanical strength and retention. With smooth interior surface, and absolutely seamless.

Hawach cellulose extraction thimbles can fit most Soxhlet-type, Tecator-type or similar devices. The glass microfiber thimbles which are made of high purity borosilicate glass fibers are widely used for high temperature filtration, up to 550℃. When the solvents are incompatible with cellulose thimble, or the solid particles need to be collected in the air and waste gas analysis, the glass microfiber thimble will be your choices.

When choosing Hawach extraction thimbles, thimble sizes should be considered carefully to fit extractors perfectly. when you calculate the external diameters, don’t forget to make the extra allowance for wall thickness.

Production Process of Extraction Thimble

Traditionally, glass extraction thimble is one of the more easily damaged glassware, and especially the external wall of the siphon reflux tube is easy to break, so you should be careful in the experimental operation.

However, Hawach extraction thimble is widely used in the laboratory, and it is more useful for flammable, toxic, or odorous solutions. Cellulose is made of high-quality cellulose cotton wool with high purity, high mechanical strength, and strong retention. The solid material should be ground before extraction to increase the area of solid-liquid contact.

Siphon Principle of Extraction Thimble

Hawach extraction thimble is a continuous extraction of the required components in solid mixtures with the principle of reflux and siphon of solvent.

When the liquid level of the solvent flowing back into the extraction tube exceeds the siphon of the extraction thimble, the solvent in the extraction tube flows back into the flask at the bottom of the circle, and siphon occurs.

With the increase of temperature, reflux begins again. Before each siphon, the solid material can be extracted by pure hot solvent, and the solvent is used repeatedly, which shortens the extraction time, so the extraction efficiency is high.

Production Process And Siphon Principle of Extraction Thimble

How To Choose And Seal A Sample Vial?

 For general sample collection, storage, and transportation in the labs, Hawach sample vials are available not only in a variety of sizes and colors but also in different volume capacities and material compositions. You can find them sterile, non-sterile, or autoclavable.

Choosing the correct sample vial for your application is important. With lots of options to choose from, it’s also complicated to select them because there are many factors you should consider. When you choose a sample vial, the most important factor is the material of the vials.

If the glass vials are pure, that means they don’t have any contaminants in the components, such as for metal, which might interfere with an experiment. Glass is also resistant of heat, which makes glass vials can be heated to over 500°C。 That’s why we choose glass vials for common use better then the plastic vials.

The glass sample vials can be in the color of clear or amber. The amber sample vials are the best for the easily damaged chemicals, as the color of amber can protect the contents in the vials from UV light which might damage certain chemicals. At the same time, the clear vials can provide for the best visibility of chemicals.
 
How to seal the sample vial? HAWACH has summarized four mainly used sample vials sealing methods.

1. Screw top sample vial
The screw-top sample vial provides a low-evaporation, reusable, and less-harmful sealing method than the crimp cap, and no additional tools are required. Threaded cap sample vials are distinguished by different thread specifications, which are defined by the Glass Packaging Association (GPI). The threaded sample vial consists of two parts: threaded bottle and cap septa.

Threaded sample vial caps are available as either an open perforated cap designed for automatic sampling, a solid cap designed for sample storage, or an integrated PP cap. This piercable screw cap is designed for a single injection because it does not require assembling the cap septa, which can save time for experiment preparation.

2. Crimp top sample vial
Crimped sample vials require aluminum caps for sealing, which are relatively inexpensive. When properly clamped, they provide the best seal for long-term storage. The jaw cover cannot be reused. The cap-pressing device is required to seal and the capping device to remove the sealing cap.

Cappers and disapper are suitable for aluminum caps of different specifications, including an adjustable precision capper for selection. The adjustable manual capping device provides an adjustable stop point on the handle to ensure that the tightness of the cap is consistent every time. Adjust the screw in the metal jaws to change the jaw depth.

The correct jaws are critical because too tight jaws can cause the septum to deform toward the center, damaging the needle and the Teflon layer to form holes larger than the correct jaws. Loose jaws can cause the septum to be punctured or the sample to evaporate.

The manual decapper can safely and quickly remove the aluminum cover with just one grip. The design of decap pliers is similar to pliers, providing an economical option. When the sample contains harmful substances, it is necessary to use the decapper, because the use of the decapper is not easy to cause leakage.

3. Snap-top sample vial
Snap-top vials can be used with crimp caps or bayonet caps, and no tools are required when using bayonet caps. Since its tightness is not as good as crimp top bottles or screw-top bottles, it is recommended for short-term sample storage or non-volatile samples.

4. Cap-pressing sample vial
For HPLC autosampler or other autosamplers that do not require a manipulator to move the sample vial, it is a more economical choice than screw-top vials: cap-pressing sample vial. Most such bottles are sold with PE (polyethylene) caps with star-shaped cuts that are easy to puncture.

How To Choose And Seal A Sample Vial?