pH510-turbid liquid acidity meter introduction and application case analysis

An Lairis pH510-turbid liquid pH meter is designed for turbid liquid or colloidal solutions. The pH value of viscous sample solutions, including milk, jam, water-based paints, cosmetics, soil solutions, sewage and sludge, etc. The micelles or particles tend to cause the electrode cell junction potential to be unstable, resulting in a variety of measurement problems, requiring the use of professional pH electrodes to achieve fast and accurate measurements. This set is equipped with a glass pH electrode for Aleris turbid liquid. It uses a ceramic liquid junction and a long-life reference system to increase the exudation rate of the external reference solution and reduce the liquid junction potential of the micelles or particles. The effect is that a double-liquid reference electrode is used, and the outer chamber is filled with a solution having the same characteristics as the sample, so that the liquid junction potential is more stable.

Performance characteristics

·Automatic calibration from pH to 5 o'clock, with calibration guidance and automatic inspection function;
· Can be calibrated using CH/USA/ NIST standards and custom buffers;
· With high purity water pH measurement mode and ammonia pure water pH measurement mode;
· With EH redox potential measurement mode;
· With stable display and automatic lock display mode, the accuracy and response time of the reading are optimized;
·90×68mm large screen LCD, large font display, white backlight, with time display, clear and easy to operate;
·0~100.0°C automatic/manual temperature compensation system function;
· Data storage 500 groups (manual and automatic storage); in line with GLP data management methods;
·With USB communication interface;
·The temperature unit can be selected as °C or °F;
·The instrument can be restored to factory settings with one button;
·According to IP54 dust and splash proof, the instrument socket has rubber cap seal protection.

Technical Parameters

Applications

Application of pH510 in pH measurement of hand sanitizer

Previously, people used soap, detergent, gasoline, detergent, etc. to wash their hands. Although this can play a certain cleaning effect, it is irritating to the skin, and the skin often appears dry, cracked, peeled, etc. after washing, and the stain removal ability of the operator of some special types of work is not ideal. In particular, oils such as gasoline, because of their toxicity, can cause harm to the human body. Hand sanitizer can avoid the above shortcomings, and it can be used for decontamination, non-toxic, non-irritating, moisturizing and aroma. At present, more and more people choose to wash their hands with hand sanitizer.

However, in the previous two years, a “White Cat” brand hand sanitizer was detected as unqualified pH, which caused people to pay attention to the pH value of hand sanitizer. The pH value of Hand Sanitizer QB2654-2004 is between 4.0-10.0, that is, the acidity and alkalinity of the product is near neutral (pH=7.0), weak acid (pH<7.0), weak base ( pH>7.0) can be, consumers can choose according to the nature of the skin, acid, alkaline too strong on the skin, often used to make the skin creping, dry, and even cracking. So we need to understand the pH of the hand sanitizer.

In this study, we measured the dilution of the same hand sanitizer into three different concentrations of pH.

Operation process

1 Prepare the machine pH510 and pH electrode. The sample samples are: 5%, 10%, 20% hand soap solution.

2 Connect the power supply and plug in the pH electrode. Place the universal electrode holder.

3 Use the standard pH buffer solution for routine calibration.

4 Wash the pH electrode with pure water and dry it, immerse it in the solution to be tested, and put it aside after a little agitation. When the LCD displays stable measured values ​​and icons, it is the measured pH value.

Note Regular calibration:

1. Press the CAL key, the instrument enters the calibration mode, and the 6.68 pH is flashed in the lower right corner of the LCD, indicating that the first point calibration is performed with the pH 6.86 buffer solution.

2. Rinse the electrode with pure water and dry it, immerse it in a pH 6.864 buffer solution, and let it stand still after stirring to stabilize the reading. When the instrument locks 6.86 pH, the LCD will display a stable icon. Press ENTER to calibrate the instrument. After the calibration is successful, the End icon will be displayed. The first point calibration ends.

3. For 3-point calibration, repeat step 2 by changing the buffer of pH4.003 and pH9.182. The operation of 5-point calibration mode is the same as above, but the calibration solution and calibration sequence can be selected at will.

Experimental result

The picture below shows 20%, 10%, 5% solution and pure water

Test chart

Test Data

Analysis: From the above experimental results, it can be seen that the pH value of a brand of hand sanitizer used in this study diluted to three concentrations is about 6.50-6.54, and the pH value of the viscous sample is small after dilution, which is in line with the hand sanitizer. The pH value is specified in QB2654-2004 (4.0-10.0).

Application of pH510 in milk pH measurement

Under normal circumstances, the pH value of pure milk is between 6.4 and 6.8, which is weakly acidic. The pH value can accurately reflect the freshness of milk. Reliable pH measurement is very important for the quality control of fresh milk. The importance of pH is that the on-line pH is mainly considered from the perspective of the freshness of milk and other media contamination in the production process. Freshness is also the focus on the acidity of the product, which will seriously affect the stability of your later products. If the product is reinforced, the pH value is the key basis for the release of the product. It is the quickest way to verify the sterilization effect of your product and whether the product is contaminated.

At the same time, dairy products can rely on pH to ensure that milk does not clump. This critical point is pH 4.3-4.6, and the pH of the milk cannot be lower than this value anyway. This is the so-called isoelectric point of milk protein. When the pH value is within this range, the repulsion between the milk protein molecules is minimal and precipitation is easy. Therefore, the pH of the protein beverage needs to be adjusted to the isoelectric point, but the pH is generally It can't be higher than 6.8. The high pH is not conducive to the product quality. When the pH is higher than 6.8, the protein and the reducing sugar are prone to Maillard reaction during the sterilization process, and the color of the product is browned.

The pH of milk is not easy to measure. They usually contain fat, protein, sulfides and many other substances, all of which interfere with electrode measurements and make measurement errors. In addition, the milk itself or the precipitated protein contaminates the junction of the electrode during the pH measurement of the milk, causing a change in the pH electrode calibration value (zero point and slope). They can also be very thick, very thin, very sticky or very hard, but we have to measure them and get fast and accurate results, so it is difficult to implement. However, if the electrodes are chosen correctly and used properly, your measurements are accurate and reliable. Ordinary pH electrodes will not be able to withstand such high pollution measurement environments, which will cause measurement errors due to poor relinearity of the electrode measurements. Anlai Lisi S3221 glass composite pH electrode adopts Swiss imported ceramic liquid junction and long-life reference system. It has large glass electrode contact area, is not easy to block, and can withstand high pollution. It is very suitable for measuring the pH of viscous liquid such as milk. value.

In this experiment, the Anlerix pH510 main unit was equipped with S3221 glass composite pH electrode and T2132 temperature electrode to measure the pH value of pure milk of Liangming and Yili.

Operation process

1 Prepare the machine pH510 host with S3221 glass composite pH electrode and T2132 temperature electrode, prepare the sample.

2 Connect the power supply. Place the universal electrode holder.

3 Routine calibration of the instrument using the standard pH buffer solution.

4 Wash the pH electrode with pure water and dry it, immerse it in the solution to be tested, and put it aside after a little agitation. When the LCD displays stable measured values ​​and icons, it is the measured pH value.

Note Regular calibration:

1. Press the CAL key, the instrument enters the calibration mode, and the 6.68 pH is flashed in the lower right corner of the LCD, indicating that the first point calibration is performed with the pH 6.86 buffer solution.

2. Rinse the electrode with pure water and dry it, immerse it in a pH 6.864 buffer solution, and let it stand still after stirring to stabilize the reading. When the instrument locks 6.86 pH, the LCD will display a stable icon. Press ENTER to calibrate the instrument. After the calibration is successful, the End icon will be displayed. The first point calibration ends.

3. For 3-point calibration, repeat step 2 by changing the buffer of pH4.003 and pH9.182. The operation of 5-point calibration mode is the same as above, but the calibration solution and calibration sequence can be selected at will.

Experimental result

The picture below shows the picture of Guangming and Yili pure milk and the contrast of pure water.

Test chart

Test Data

Analysis: From the above experimental results, it can be seen that the pH values ​​of the two brands of Guangming and Yili used in this study are 6.61 and 6.67, respectively, which are relatively close, and both are within the standard range of 6.4-6.8.

Maintenance and maintenance

Daily maintenance of pH electrode

General pollution: The electrode was washed with water, 0.1 mol/l NaOH or 0.1 mol/l HCl for several minutes.

● Grease or organic contamination: Wash the electrode with acetone or ethanol for a few seconds.

• Inorganic metal oxide contamination: Wash with less than 1 mol/L dilute acid.

● Resin polymer material contamination: Wash with dilute alcohol, acetone or ether.

● Protein blood cell sediment contamination: Wash with an acid enzyme solution (such as a mother-in-law tablet).

● Contaminant contamination: Dilute bleach and peroxide cleaning.

● Regeneration of the electrode: After long-term use of the electrode, the sensitive glass bulb will age. The electrode is soaked in 0.1mol/L hydrochloric acid for 24h, washed with pure water, and then soaked in the electrode soaking solution for 24h. Preparation of 0.1 mol/L hydrochloric acid: 9 mL of hydrochloric acid was diluted to 1000 mL with pure water. If the passivation is serious, the lower end of the electrode can also be immersed in 4% HF (hydrofluoric acid) for 3~5 seconds, washed with pure water, and then soaked in the electrode soaking solution for 24 hours to renew it.

Preservation of pH electrode

●The protective bottle at the front end of the pH electrode has an appropriate amount of electrode soaking solution, and the electrode tip is immersed therein to maintain the activation of the glass bulb and the liquid junction.

● If the soaking liquid in the protective bottle is found to be turbid and moldy, it should be washed in time and replaced with a new soaking solution.

● The electrode should be protected from long-term immersion in pure water, protein solution and acidic fluoride solution, and prevent contact with organic grease.

● Always keep the instrument clean and dry. Pay special attention to keep the height and cleanness of the meter and electrode sockets. Otherwise, the measurement will be inaccurate or invalid. If it is contaminated, it can be cleaned and dried with medical cotton and anhydrous alcohol.

●Ball protection

The sensitive glass bulb at the front end of the composite electrode cannot be in contact with the hard object, and any damage and bristles will invalidate the electrode. Wash the electrode with pure water before and after the measurement. After cleaning, dry the electrode. Do not use a paper towel to test the bulb. This will make the electrode potential unstable and prolong the response time. After the measurement in the viscous sample, the electrode was repeatedly washed with pure water several times to remove the sample adhered to the glass film. Or wash with a suitable solvent and then wash off the solvent with pure water.

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