Technical paper on physical and chemical inspection 1: "On related technologies in quality control assessment of physical and chemical inspection"
With the rapid development of national science and technology in recent years, all kinds of scientific research work are also expanding. Physical and chemical inspection is an important part of scientific research and inspection in China, especially in health supervision and management. However, due to its high accuracy, physical and chemical research requires that the accuracy of detection must be improved during the detection process. Quality control is a very effective method to improve accuracy, and different tests adopt different quality control techniques.
Physical and chemical inspection; Quality control; Technical analysis; Physics; chemistry
Physical and chemical inspection is a physical and chemical test and inspection with the help of some measuring tools, so it is also called? Instrument inspection? This measuring tool or instrument is very accurate. For example, commonly used measuring tools include micrometer, dial indicator, gauge, microscope, etc. With the reform of health industry and the strengthening of health supervision and management in China, health departments have put forward higher requirements for testing. Physical and chemical testing is an important means of health testing, which provides more accurate testing data for supervision and law enforcement and plays an important role in labor health supervision and management.
1 related technologies in quality control evaluation of physical and chemical inspection
According to the continuous exploration and summary of many researchers for many years, the quality control evaluation of physical and chemical inspection can be mainly divided into the following aspects.
Analysis of metal content deposited on 1. 1 filter membrane This technology is to precipitate it by adding related chemicals, and then filter it, so as to analyze the type and content of the filtered metal. The metal samples deposited on the filter membrane have high stability and will not be lost with the change of natural environment under normal environment. In the process of analyzing the metal content deposited on the filter membrane, attention should be paid to preventing dust pollution. When extracting evaluation samples, we should pay attention to the disinfection and drying of tools to avoid pollution and inaccurate evaluation results. After the inspection, put the sample into a clean dryer.
1.2 analysis of metal content in solid salt As the name implies, this physical and chemical inspection and evaluation technology is to evaluate the metal content and types in solid salt. Like the metal samples deposited by filter membrane, the metal samples in solid salt also have good stability. When extracting samples, we should pay attention to the fact that the sample size should not be too large. Before taking samples, we must dry them for at least one hour. After the evaluation, we should put the sample in a clean dryer.
1.3 analysis of the content of organic poisons adsorbed by activated carbon tube This technical assessment principle is the role of chemical affinity, because the adsorption of activated carbon tube has strong adsorption capacity, and it is not easy to separate it by physical methods. It was separated by chemical affinity and the sample was analyzed. Pay attention to dust-proof and moisture-proof in daily sample preservation. Therefore, the organic toxic samples adsorbed by activated carbon tube are not suitable for refrigerator storage.
Analysis of Toxic Content in 1.4 Aqueous Solution There are many toxic samples to be detected in aqueous solution, such as the content of hydrogen chloride in aqueous solution and the content of chromium trioxide in aqueous solution. The stability of the poison sample to be tested in aqueous solution is poor, and it will change with the change of environment in normal natural state. For example, when the ambient temperature rises, the natural evaporation of water in the sample will increase, and when the sample is stored, if the bottle cap of the aqueous solution is not tightly sealed, it will also lead to water evaporation. Therefore, it is very important to check the preservation of aqueous solution samples. When storing, pay attention to the environment where the temperature will not change. Refrigerator or freezer is a good idea, but also pay attention to whether the sample bottle is sealed.
2. Problems that should be paid attention to in the process of sampling evaluation
2. 1 The sample evaluation process shall be conducted in strict accordance with the specifications and standards. The state has promulgated relevant technical specifications and standards for quality evaluation of physical and chemical inspection. Therefore, in actual operation, we should strictly follow the specifications and standards to prevent errors or inaccurate tests. Before inspection, the scheme of operation and analysis should be clearly written, and reagents should be configured according to relevant indexes and standards. At the same time, a small number of evaluation samples are detected and analyzed first, mainly to detect their concentrations, so as to determine the sampling amount of evaluation samples for analysis. In the actual assessment process, first make a standard curve, including five blank points * * *, and make six copies for each point to calculate the coefficient of variation less than 2%, list the regression equation and calculate the regression coefficient. In order to improve the accuracy of evaluation, we should take three evaluation samples and operate them in the same way as the standard curve, then calculate the average value of these three determinations as the final determination result, and pay attention to calculate its relative standard value, which should be less than 5%, otherwise the error is too large and the data cannot be used as the determination result. Pay attention to various formats and units in the writing process, and strictly follow the standard format.
2.2 Precautions for using instruments and reagents in the inspection process are the pipette used in the experiment, which requires the use of standard measuring instruments produced by units that have obtained measurement certification, or calibrated by inspectors themselves, because the index parameters of the pipette will also affect the accuracy of the inspection. In the whole process of analyzing and evaluating samples, special attention should be paid to absorbing standard reagents and evaluating the dose of sample solution. Secondly, we should pay attention to the distilled water used in the experiment. In the process of sample analysis, the quality of distilled water will profoundly affect the blank value of lead in chemical analysis, and ultimately affect the analysis results. The purity of analytical reagents will also have a great influence on the analytical results. Therefore, in the actual assessment, in order to ensure the accuracy of the results of the assessment samples, distilled water and analytical pure reagents should be used, and GR grade chromatographic pure reagents should be used in the gas chromatography assessment.
3 Conclusion
The quality control evaluation of physical and chemical inspection is not a complicated project, but the importance of its inspection results requires that the inspection results must be more accurate. Therefore, in the evaluation process, it is necessary to ensure that all operations are carried out in strict accordance with standards and specifications to protect samples from pollution, and the test result report must be comprehensive and accurate according to the relevant format requirements. Strengthen the quality control of physical and chemical inspection through standardized operation in all aspects.
refer to
[1] Huang Jialong, Li Cheng, Du Hong, Zhang Yin, Chen Fang. Construction of a new practical teaching mode for health inspection and quarantine technology specialty [A]. Zhejiang Medical Association. 20 12 Zhejiang Medical Education Annual Meeting [C]. Zhejiang Medical Association, 20 12.4.
[2] Notice on Convening the National Symposium on Physical and Chemical Inspection of Materials and Product Quality Control and the 40th Anniversary Celebration of Physical and Chemical Inspection (No.1) [J]. Physical and chemical test (physical volume), 20 12, 02: 92.
[3], Cai, Zhou. Deepening the reform of biochemistry experiment teaching in medical colleges with quality education as the guidance [J]. Hainan Medical, 20 1 1,15:135-137.
[4] Zhang Xiuli, Liao Xingguang, Alina Zhang, Gao Baozhen. 20 10 Evaluation and analysis of quality control assessment results of food hygiene microbiological inspection in Henan Province [J]. China Journal of Hygienic Inspection Technology, 201,07: 856-857.
Physical and chemical inspection technology paper 2: "Study on preparation technology of physical and chemical inspection samples of tea"
The preparation technology of physical and chemical test samples of tea was studied, including the selection and processing of fresh leaves, pretreatment and crushing of raw tea, uniform mixing and subpackaging of crushed samples, uniform stability of test samples and numerical values of test characteristics. Finally, some development suggestions such as transferring standardized samples to laboratories are put forward, hoping to contribute to the development of tea quality testing in China.
Keywords: preparation of physical and chemical test samples of tea
Tea is one of the three major drinks in the world. Compared with other drinks, tea is more affordable and economical, so the drinking range of tea is gradually expanding, with more and more consumers, and it has become the first choice of 2 1 global healthy drinks. However, with the rapid development of commodity economy and the increasingly fierce market competition environment, various fake and shoddy products have appeared, and tea is no exception. In order to meet the requirements of commodity market, crack down on various forms of fake tea and effectively rectify the chaotic tea market, it is urgent to carry out physical and chemical inspection on tea.
I. Overview of Standard Samples for Physical and Chemical Inspection of Tea
The content of testing tea includes testing the quality, physical and chemical standards and hygiene standards of tea. Among them, the physical and chemical inspection items focus on water extract, moisture, tea polyphenols, caffeine and other indicators; Hygienic inspection is the detection of residual pesticides such as bhc in tea, and it is also a scientific inspection of heavy metals and microorganisms.
Standardized samples refer to one or all kinds of uniform and sufficient substances whose characteristic values have been determined, which are mainly used for calibrating equipment, instruments, evaluation methods and assignment of substances. At present, there are standard samples of inorganic elements in tea with assignment characteristics, which were developed by China Institute of Ecological and Environmental Sciences and sold by China Institute of Reference Materials. Other standardized samples that can reflect the physical and chemical indexes of tea have never been purchased. In order to effectively improve the working ability of national tea testing institutions and strengthen the reliability of data determination by testing institutions, it is necessary to design and copy standardized samples for various physical and chemical indexes of tea, which has become the factual basis for testing units to objectively understand the technical level of laboratory tea testing projects.
Second, the preparation technology of tea physical and chemical inspection standard samples
(1) Selection and processing of fresh leaves
The main factors affecting the physical and chemical indexes of tea are the types of tea trees, the time of making tea, the freshness of raw materials and the processing links. In order to fundamentally control the overall quality of raw materials, we must choose the same varieties and tea gardens and pick fresh leaves according to the same picking requirements. Samples of the same grade of crude tea are processed under the same steps. We need to pay attention to two aspects: on the one hand, we need to effectively control the level of raw tea. An important factor to ensure the quality of tea is the moisture contained in tea. If a rough tea sample wants to become a standardized tea sample, its moisture content should be below 6.5%. On the other hand, it is reasonable to control the freshness of raw materials. Processing tea with fresh and tender tea leaves not only consumes high cost, but also produces more fluff, which is very unfavorable for preparing uniform samples. To be a standardized sample of tea, it is best to choose fresh leaves with one bud or three or four leaves as raw materials, and use secondary or below raw tea as raw materials. Some tea samples were made according to the above requirements, and were used as standardized samples to verify the ability of tea by the national accreditation organization of the laboratory. It not only has low cost, but also ensures its consistency from the beginning.
(2) Pretreatment and crushing of crude tea
Freshly processed raw tea usually contains some sundries. In order to ensure the unification of the quality standards of the whole batch of raw tea, it is urgent to find faults in all tea leaves and remove tea stems and stone particles at the same time to avoid the influence of these impurities on the indicators. According to relevant international standards, tea powder must be used as the physical and chemical test sample of tea. Therefore, under the premise of pretreatment, the raw tea samples must be ground. Before grinding, the grinding equipment should be cleaned first, then a small amount of samples should be put in for grinding, and these grinded samples should be cleaned up. Finally, the sample is ground formally, and the ground sample is screened with a sieve with an aperture of 0.6mm ~ 1mm as a preparation sample.
(3) Uniformly mixing the ground samples and subpackaging.
The prepare standardized sample is different from that sample use for normal detection. The number of samples prepared at one time is relatively large. In order to ensure the high uniformity of the samples, the screened ground samples must be fully mixed before the subpackaging operation. After the samples are mixed evenly, they are placed in dry and clean equipment, and the bottle cap is tightly closed, which provides a closed, dry and sun-proof environment for the preservation of tea samples.
(4) Testing the uniformity and stability of the sample.
Randomly take more than 10 samples from the whole sample and check its uniformity. The items to be tested can be used to check the uniformity, and the items that are representative or sensitive to uneven samples can be selected. Each sample is tested by the same tester for more than 2 times under the same environmental conditions. The single factor analysis of variance is used to test the results, and it is fully verified that there is no significant difference between the samples. Only in this way can it be proved that it is a uniform sample. In the uniformity inspection of the samples needed to verify the tea capacity, the related items such as total ash and crude fiber were selected for uniformity inspection. Due to the correct operation of preparing uniform samples in the early stage, the uniformity of the above test results is verified by one-way variance, which shows that it is uniform. The above-mentioned tea project is stable in a closed and dry environment, so the samples used in the above-mentioned project do not need to be tested for stability.
(5) detecting characteristic values
To detect a certain characteristic value, through dozens of laboratories that need to have the ability to detect tea, according to the detection method stipulated by the state, the corresponding characteristic value is determined jointly by applying the method of joint detection between laboratories. That is, according to the method specified in the relevant standards, the test results obtained by each laboratory are counted and calculated, and finally the measurement uncertainty reflected by the characteristic values of standardized samples is determined.
Thirdly, the development of physical and chemical samples of tea.
At present, China is trying to verify the plans of various capabilities. In the activity of verifying the ability of tea, the participating units are very enthusiastic, and more than 100 laboratories have participated in individual projects. In the process of carrying out the work, the staff deeply realized that it was not easy to prepare a large number of samples. In the process of preparing samples, how to ensure the uniformity of samples and test them effectively needs to spend more financial resources and energy. Therefore, the relevant staff think that the number of samples can be increased by verifying the ability of tea. Because the remaining samples have passed the uniformity test after each tea capacity verification, they are further confirmed in the tea capacity verification process; Some excellent laboratories with high technical level can be produced through verification ability. Therefore, when the standardized samples are fixed, the fixed values can be transferred to the test-related data provided by these laboratories. For example, the standard value required for a sample-related project can be defined as the median value of the measured values obtained by various laboratories, and the standardized IQR can be defined as the standard deviation. If these resources can be used scientifically and effectively, not only can the cost of preparing and verifying tea standardized samples be greatly reduced, but also the fixed value results can be infinitely close to the true value, which can meet the requirements of quality inspection units for making tea physical and chemical inspection standard samples.
Concluding remarks
At present, tea workers have rich and professional tea background advantages in preparing tea standard samples. However, in order to upgrade the ability of verifying tea to standardized tea samples, we need to further analyze and understand the relevant research procedures, so as to prepare standardized tea samples with stable results, accurate values and uniform samples, give full play to the legal effect, and make contributions to the development of tea quality inspection in China.
References:
[ 1]GB/T8303―2002。 Preparation of ground tea samples and determination of dry matter content [M]. National Standard of People's Republic of China (PRC), 2009.
[2]CNAS-GL03。 Guide for evaluating the uniformity and stability of proficiency testing samples [M]. China National Accreditation Committee for Conformity Assessment 2008.
Physical and chemical inspection technology Part III: Teaching process design of food physical and chemical inspection technology based on working process.
As one of the important core courses of food nutrition and testing specialty, the teaching of food physical and chemical testing technology will directly affect the quality and quantity of students. Therefore, it is necessary to design the teaching process, cultivate students' enthusiasm, initiative and creativity, and mobilize students' interest in learning, so as to improve the classroom effect of teaching. The teaching process is a comprehensive embodiment of knowledge, experience, methods and abilities, which should reflect both ways and means of doing things. In order to do a good job in the teaching of this course, this paper designs the teaching process of the course of Food Physical and Chemical Inspection Technology, and ensures the teaching effect through the teaching process design, so as to achieve the talent training goal that meets the requirements of enterprises.
First, the curriculum development of food physical and chemical inspection technology
The development of food physical and chemical inspection technology course is oriented to the working process of physical and chemical inspection in enterprises. Physical and chemical inspection workflow design is the task that enterprises need, and learning situation design is the carrier to determine the development process. Specifically, first of all, the specialty of food nutrition and inspection was investigated, and the investigation report was written to analyze the professional ability and working ability required for the post of physical and chemical inspection in enterprises. According to the requirements of professional ability and working ability, the course structure of food physical and chemical inspection technology is analyzed, the course system is optimized, the teaching content of the course is analyzed, the course standard and experimental training guide book are formulated, and then the teaching is designed.
Second, the choice of teaching content and course content structure.
In the selection of teaching content of food physical and chemical inspection technology course, according to the development of national and local food enterprises and the training objectives of food nutrition and inspection specialty in higher vocational colleges, according to the requirements of food physical and chemical inspection post for students' knowledge, ability and quality, according to? That's enough. Is it necessary? The principle of choosing teaching content, according to the principle of professionalism and practicality, choose the teaching project of food physical and chemical training.
Third, the design of teaching process of food physical and chemical inspection technology
The teaching process of food physical and chemical inspection technology course adopts specific tasks to guide the whole process of students' learning. The teaching process of this course is designed according to the process of food physical and chemical inspection, and the physical and chemical inspection items are selected from the tasks required by the job. After the inspection project is selected, the students design the project according to the inspection project. After the scheme design is determined, teachers and students need to discuss and revise it repeatedly. It can only be implemented after it is passed. According to the determined scheme, students complete the preparatory work of experimental training under the guidance of teachers, and then start the training operation. After the operation is completed, the training results are analyzed, and then the opinions of teachers and students are widely collected. Finally, the teacher feeds back the questions to the students to avoid similar mistakes next time. See figure 1 for the teaching process design of the course of food physical and chemical inspection technology.
Figure 1 Teaching Process Design of Food Physical and Chemical Inspection Technology
Fourth, implement project-oriented and task-driven teaching methods based on working process.