"Serial" paint inspectors, I would like to say to you (5) - paint harmful heavy metal element content test, you have a deep understanding?

1What is harmful heavy metal elements in the coating
harmful elements mainly refers to lead, cadmium, chromium, mercury and other biotoxic elements, such elements in the body will accumulate, not easy to discharge out of the body, more than a certain amount will have toxic effects on people and animals, causing biological tissue lesions or dysfunctionThe harmful elements of coatings usually refer to heavy metal elementsThe so-called heavy metal elements, generally refers to the density of more than 4.5g /cm3 of metal elements, in the element altime table about 45 kinds, including copper, lead, zinc, iron, cobalt, nickel, manganese, cadmium, mercury, tungsten, tantalum, gold, silver and so onHarmful heavy metal elements in coatings mainly contain lead, cadmium, chromium, mercury, etc, but because of arsenic, selenium to the harm of organisms and heavy metals similar, so also according to the requirements of heavy metalsHarmful heavy metals in coatings are mainly derived from the use of facial fillers and certain additives in coating production2The test method of harmful heavy metal elements in the coatingthe method of quantitative analysis of heavy metal elements in the coating is divided into chemical analysis method and instrument analysis method, which can be divided into chemical capacity method, spectrophotoscopy method, atomic absorption spectroscopy method, inductive lysate plasma emission spectroscopy method, atomic fluorescence spectroscopy method, polar spectrum method, hydrogenation method, X fluorescence spectroscopy method, etccurrently mainly use atomic absorption spectroscopy (AAS) method, inductively coupled plasma emission spectroscopy (ICP-OES) method, atomic fluorescence spectroscopy (AFS) method, X-fluorescence spectroscopy (XRF) instrument analysis method3The test category of harmful heavy metal elements in paintthere are many kinds of harmful heavy metal elements to be tested in the coatingThe newly released Green Standard GB/T35602-2017 Green Product Evaluation Coatings provide for the testing of nine heavy metal elements: lead (Pb), cadmium (Cd), chromium (Cr), mercury (Hg), arsenic (As), vanadium (Ba), vanadium (Sb), selenium (Se), and cobalt (Co)Mandatory national standard GB18582-2008 "In-wall coating sleuth limit" and GB18581-2009 "solvent wood coating in the limit of hazardous substances" two standards are limited to lead (Pb), cadmium (Cd), chromium (Cr), mercury (Hg) four harmful heavy metal elements content But with the upgrading of environmental policies, there will be more and more elements in the coating that need to be restricted, which is a major trend in technological development in addition to harmful heavy metals to human body, some product standards of coatings, there are iron (Fe), calcium (Ca) and other elements that are not harmful to human body limit This is a requirement in terms of product performance, and the testing method is different from the harmful elements 4 The test classification of harmful heavy metal elements in the coating at present, the test of the content of harmful heavy metal elements in the coating is mainly divided into soluble heavy metal content test and the total heavy metal content test soluble heavy metal content test using the same concentration of human stomach acid solution, generally formulated into 0.07mol /L of dilute hydrochloric acid solution (pH-1.12) treatment of the paint dry film (self-drying or drying), and then use appropriate methods to determine the content of the specified elements The essence is to separate harmful elements by extraction, so that the harmful elements under test are dissolved in acid solution The total heavy metal content test refers to the coating after drying, using the appropriate pre-treatment method to remove the organic components, will be measured elements are all converted into suitable for the instrument to determine the liquid state, and then the use of suitable analytical instruments for testing Total content tests for lead (Pb), cadmium (Cd), chromium (Cr), mercury (Hg), arsenic (As), vanadium (Sb), selenium (Se), cobalt (Co) are tested for total content in GB/T35602-2017, and patoium (Ba) is tested for soluble content The four soluble heavy metal content slots of lead (Pb), cadmium (Cd), chromium (Cr) and mercury (Hg) are required in GB18582-2008 and GB18581-2009 GB24613-2009 "Toy Coatings in the Limit of Harmful Substances" is carried out eight harmful soluble heavy metal element content test 5 Test methods for soluble harmful heavy metal elements
5.1 Major test instruments and equipment atomic absorption spectrometers; atomic fluorescence spectrometers; hydrogenthanator generators; inductively coupled plasma emission spectrometers; acidometers; microporous membranes (pores 0.45 m); agitators, crushing equipment, ovens 5.2 The preparation of the coating film will be stirred evenly Prepare a mixed specimen according to the product's express ratio (the diluent does not need to be added) and, after stirring evenly, prepare a film with a suitable thickness on the glass plate or Teflon plate Under the dry conditions specified in the product specification, the film to be completely dried (self-drying paint if dried, the temperature should not exceed (60 x 2) c), remove the coating film, at room temperature with a crushing device to crush it, so that the size of the coating film is less than 5mm For coating filmthat that cannot be crushed by the shredder (e.g elastic, plastic coating), the coating film is cut with clean scissors so that the size of the coating film is less than 5mm Powdered samples are prepared directly for the test solution 5.3 sample stomping said that the crushed sample 0.5g was placed in a 100mL beaker and 25mL hydrochloric acid solution was added with a pipe After stirring 1min on the blender, measure its acidity with an acidity meter If the pH is greater than 1.5, the pH is adjusted with hydrochloric acid between 1.0-1.5 Stir continuously at room temperature for 1h, then place 1h Then immediately with microporous membrane filtration The filtered filter is saved from light and the analysis test is completed in one day If the filter has a shelf life of more than 1d before the element analysis test, the concentration of the preserved solution is about 1mol/L If the sample size changes, the volume of the added hydrochloric acid solution should be adjusted to 50 times the sample size The speed of the agitator should be adjusted throughout the extraction period to keep the specimen in a suspended state at all times, while minimizing spills 5.4 The conditionsetting of the test instrument test with an atomic absorption spectrometer, an inductively coupled plasma emission spectrometer, and a mercury element using an atomic fluorescence spectrometer or a hydride generator Testing of each element usually has multiple spectral lines to choose from The choice of spectral line takes into account not only the sensitivity of each element but also the applicable condition of the substrate interference of the solution of the element being tested the usual spectrum of atomic absorption spectrometers (with hydride generators): lead (Pb): 283nm; inductively coupled plasma emission spectrometers are usually spectral: lead (Pb) 220nm; cadmium (Cd)226nm; chromium (Cr) 267nm; Mercury (Hg) 194nm; arsenic (As) 197nm; Paa(Ba) 233nm; sb (Sb) 206nm; selenium (Se) 203nm; cobalt (Co) 238 inductively coupled plasma emission spectrometer (ICP-OES) test conditions are set: power: 1.00kW; plasma gas flow: 15L/min; auxiliary gas flow: 1.5L/min; atomized flow: 0.75L/min 5.5 standard solution formulation atomic absorption spectrometer standard reference solution formulation: the selection of suitable capacity bottles and pipettes, with hydrochloric acid solution step-by-step dilution of lead (Pb), cadmium (Cd), chromium (Cr), mercury (Hg) standard solution, preparation series of standard reference solutions Usually formulated as: inductive lying plasma emission spectrometer standard liquid configuration, is usually the purchase of a proven standard substance of a variety of elements of the mixed standard solution dilution, for the non-purchaseable mixing standard, usually need to use a single element of the standard solution for mixing configuration, but to ensure that the mixed standard solution, chemical reaction or other phenomena will not cause the concentration of the standard substance to change 5.6 test the solution after extraction using the detection limit of the appropriate analytical instrument to test the soluble harmful element content If the relative deviation of the two test results is greater than 10%, redo the steps of 5.2 The calculation of the 5.7 results the content of soluble harmful heavy metal elements in the specimen, according to the formula: 5.8 the correction of the results due to the soluble heavy metal test method by the pH of the prepared acid solution, the particle size of the film sample crushed, stirring temperature and other sample pre-treatment conditions have a greater impact, so the results need to be corrected on the basis of the final analysis results That is, the result of calculating the division according to the formula should be subtracted from the result multiplied by the value of the analysis correction coefficient of the corresponding element in the table, as the final analysis results of the element are reported The analytical correction coefficient of each element 5.9 the precision of the test method the repeatability requires that the relative deviation of the two test results of the same operator is less than 20%, and the relative deviation of the test results between different laboratories is less than 33% 6 Tests of total harmful heavy metal content 6.1 Major test instruments and equipment atomic absorption spectrometers; 6.2 the preparation of coating film will be tested sample stirring evenly, according to the product express ratio (diluent does not need to add) to prepare mixed samples, stirred evenly, in the glass plate or Teflon plate preparation thickness of suitable coating film Under the dry conditions specified in the product specification, the film to be completely dried (self-drying paint if dried, the temperature should not exceed (60 x 2) c), remove the coating film, at room temperature with a crushing device to crush it, so that the size of the coating film is less than 5mm For coating filmthat that cannot be crushed by the shredder (e.g elastic, plastic coating), the coating film is cut with clean scissors so that the size of the coating film is less than 5mm Powdered samples are prepared directly for the test solution For samples that cannot be filmed, the preparation of the experimental solution is carried out directly after drying 6.3 sample treatment
sample treatment is usually done in three ways: dry ashification, wet acid digestion and closed microwave digestion The closed microwave digestion method is usually used, which is convenient and fast, and is suitable for pre-processing of many elements When testing volatile harmful elements (e.g mercury, arsenic), dry ashization and wet acid digestion should not be used, and closed microwave digestion should be used for treatment the steps of the closed microwave digestion method: say that the sample after the shredding is about 0.1g to 0.2g (accurate to 0.1mg) placed in the microwave digestion tank, added about 6mL of nitric acid, 2mL or so hydrogen peroxide Then the solution tank is closed, put into the microwave digestion instrument, set the appropriate digestion conditions for digestion After the digestion is completed, the desolving tank is cooled to room temperature, the solution is opened, the solution is filtered with a membrane and transferred to a 50mL capacity bottle Rinse the inner wall and lid of the tank with water, collect the washing liquid in the same capacity bottle, and flush the membrane with water, and the resulting solution is collected in the same capacity bottle, diluted to the scale with water At the same time to do reagent blank test the above method to dissolve the sample, according to the actual condition of the sample to determine the appropriate digestion conditions, to ensure that the organic compounds in the sample are completely removed, so that all the elements under test dissolved If the treated sample has residue, the residue is determined by appropriate measurement means (e.g weighing a second digestion after the residue is dried) to ensure the presence of no measured elements If so, the residue is dissociated twice and the demosis is combined 6.4 Other processes processed samples can be tested using an atomic absorption spectrometer or an inductively coupled plasma emission spectrometer, and the instrument test ingress with a standard reference solution The formulation of the standard reference solution should select a good concentration range so that the test value falls in the middle range of the curve The linear coefficient of the standard curve is best above 0.999 The formula used in the test calculation is the same as the test for soluble heavy metal element content Since the total content test is a determining value of the content of heavy metal elements in the sample, unlike the test of soluble heavy metal element content, the sample test results do not need to be corrected 6.5 Precautions for the total content of heavy metals test
for some insoluble acid substances testing, according to the actual conditions need to be used to remove the conditions of the choice If the sample contains silica, to dissolve completely need to add a trace HF solution, after digestion, and then in the acid-cutting device heating to remove excess HF acid, to prevent corrosion of the torch tube For sulphate, titanium dioxide and other insoluble acid substances, can reduce the weighing, repeated lysing, gradually dissolved samples, or choose other suitable methods to dissolve the sample test For samples containing calcium carbonate, some hydrochloric acid solution sits more suitable for the digestion of the sample The precision of the 6.6 method requires that the relative deviation of the two test results of the same operator is less than 10%, and the reproducibility requires that the relative deviation of the test results between different laboratories is less than 20% whether it is the test of soluble heavy metal content or the test of total heavy metal content, in the process of testing needs to be careful, careful In particular, the formulation of the series of standard solutions, if the concentration deviation between the points is large, then the five points are difficult to line In addition, pay attention to other problems, such as the purity of the instrument acid, the concentration of acetylene and argon, laboratory temperature, humidity and so on These can have an impact on the test results These conditions are noted so that we can quickly and accurately complete the heavy metal content testining in the paint sample " Guide" paint detector, I would like to say to you (6) - the original record of filling in and changing, there are new requirements! relevant wonderful article (click on the title to read) "serial" paint detector, I would like to say to you (1) - from the experimental auxiliary staff W wipe window sill caused by the feeling "serial" paint testing personnel, I would like to say to you (2) - non-volatile content determination, you did the right thing? "serial" paint detector, I would like to say to you (3) - "fine" to operate, reading has "degree", how can do a good job of coating "fineness" test? "serial" coating detector, I would like to say to you (4) - about the corrosion test coating scratch operation, do you understand?