WO2021098128A1 - 消费品化学检测项目的混样定量测试方法与装置 - Google Patents
消费品化学检测项目的混样定量测试方法与装置 Download PDFInfo
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Definitions
- the invention relates to the technical field of chemical detection, in particular to a mixed sample quantitative test method and device for consumer product chemical detection items.
- the mixed test method is to combine several samples into a group.
- test item of a single sample is negative or qualified
- test item of this group of mixed samples is negative or qualified (calculated by a single sample)
- the conclusion is: only one test, the test items of these mixed samples are negative or qualified; when the test items of the mixed sample are positive or unqualified (calculated as a single sample), then the single The samples are checked one by one.
- the mixed sample inspection method firstly, the number of tests can be reduced in the detection and analysis. The most fundamental benefit is to reduce the workload, improve the work efficiency, and greatly reduce the test cost, so as to obtain obvious economic and social benefits; secondly, the mixed sample Inspection can reduce the use of solvents and reagents, thereby reducing environmental pollution and the health effects of experimenters.
- the key to the mixed sample method is how to determine the mixed sample size, that is, how many samples are mixed as a mixed sample to be tested, and how many such mixed samples should be tested under certain accuracy requirements. This is called the mixed sample size, or the number of tests. . If the mixed test method is improperly applied, it will not only save time and cost, but also directly affect the accuracy of the test results.
- the present invention proposes for the first time that the uncertainty is introduced into the mixed test model, based on the selection of representative products and test items Based on the theoretical basis of applied probability theory and mathematical statistics, combined with strict statistical analysis of more than one hundred thousand sample data, the test items that can be applied in the field of consumer goods are refined and are scientific, operability and practical.
- the mixed sample test quantitative model proposes for the first time that the uncertainty is introduced into the mixed test model, based on the selection of representative products and test items Based on the theoretical basis of applied probability theory and mathematical statistics, combined with strict statistical analysis of more than one hundred thousand sample data, the test items that can be applied in the field of consumer goods are refined and are scientific, operability and practical.
- the mixed sample test quantitative model is provided for the first time that the uncertainty is introduced into the mixed test model, based on the selection of representative products and test items Based on the theoretical basis of applied probability theory and mathematical statistics, combined with strict statistical analysis of more than one hundred thousand sample data, the test items that can be applied in the field of consumer goods are refined and are scientific, operability and
- a mixed sample quantitative test method for chemical test items of consumer products including the following steps:
- K max the maximum mixed number, rounded to the end
- L the limit or reporting limit of the item to be tested, in mg/kg
- U rel the relative expanded uncertainty near the limit concentration
- F the limit or reporting limit
- the safety factor of m tot the total mass of the mixed test sample, in g
- V the volume of the constant volume solution, in mL
- IDL the instrument detection limit, in mg/L
- M the limit or report limit corresponding to the item to be tested number
- u rel is the relative standard uncertainty around the limit concentration
- k is the inclusion factor, and the confidence is 95%
- k 2
- u rel,1 is the relative standard uncertainty of the method reproducibility, that is, reproducibility The standard deviation of the data
- u rel,2 the relative standard uncertainty of the method recovery
- u rel,3 the relative standard uncertainty of the standard curve, that is, the standard deviation of the reproducibility data
- u the standard uncertainty around the limit concentration, in mg/L
- L the limit or reporting limit of the item to be tested, in mg/kg
- U 1 the standard uncertainty of the test item 1, unit mg/kg, u 2 , the standard uncertainty of the test item 2, unit mg/kg, u 3 , the standard uncertainty of the test item 3, Unit mg/kg;
- the work-saving efficiency table is as follows Established by:
- S represents the saved workload
- q represents the positive rate/unqualified rate
- K represents the mixed number
- the samples to be tested are grouped according to the most suitable mixing number, and the mixed sample test is performed.
- the maximum content of the substance to be tested in a single test sample is calculated, and if it exceeds the revised limit or reporting limit, the mixed sample is split and tested separately.
- the positive rate/unqualified rate of the item to be tested is less than 20%.
- the value range of the safety factor F of the limit/report limit is 0%-100%.
- a mixed sample quantitative testing device for chemical testing items of consumer products including the following modules:
- the maximum mixed number obtaining module is used to obtain the relevant data of the item to be tested, and enter the following model to obtain the maximum mixed number:
- K max the maximum mixed number, rounded to the end
- L the limit or reporting limit of the item to be tested, in mg/kg
- U rel the relative expanded uncertainty near the limit concentration
- F the limit or reporting limit
- the safety factor of m tot the total mass of the mixed test sample, in g
- V the volume of the constant volume solution, in mL
- IDL the instrument detection limit, in mg/L
- M the limit or report limit corresponding to the item to be tested number
- u rel is the relative standard uncertainty around the limit concentration
- k is the inclusion factor, and the confidence is 95%
- k 2
- u rel,1 is the relative standard uncertainty of the method reproducibility, that is, reproducibility The standard deviation of the data
- u rel,2 the relative standard uncertainty of the method recovery
- u rel,3 the relative standard uncertainty of the standard curve, that is, the standard deviation of the reproducibility data
- u the standard uncertainty near the limit concentration, in mg/L
- L the limit or reporting limit of the item to be tested, in mg/kg
- U 1 the standard uncertainty of the test item 1, unit mg/kg, u 2 , the standard uncertainty of the test item 2, unit mg/kg, u 3 , the standard uncertainty of the test item 3, Unit mg/kg;
- the optimal mixed number determination module is used to query the work-saving efficiency table according to the positive rate or the unqualified rate of the item to be tested, and select the mixed number that saves the most work as the most suitable mixed number from 2 to K max.
- the work-saving efficiency table is established according to the following formula:
- S represents the saved workload
- q represents the positive rate or the unqualified rate
- K represents the mixed number
- the mixed sample test module is used to group the tested samples according to the most suitable mixed number and perform mixed sample test.
- the mixed sample test module calculates the maximum content of the substance to be tested in a single test sample after the mixed sample test, and if it exceeds the revised limit or reporting limit, the mixed sample is split and tested separately.
- the positive rate/unqualified rate of the item to be tested is less than 20%.
- the value range of the safety factor F of the limit/report limit is 0%-100%.
- the invention combines the regulatory limit requirements, measurement uncertainty, mixed sample amount, mixed sample ratio and other parameters to find the maximum mixed number that guarantees the accuracy of the detection result, and then according to the relationship between the qualification rate, the mixed sample number and the workload saving Establish a queryable table. For various items to be tested, you can directly check the table to get the workload saved under different mixed numbers. When the mixed number does not exceed the maximum and the corresponding saved workload is the largest, the mixed The number is the best mixed number, and the mixed sample test is carried out according to the mixed number, which not only saves the workload, improves the detection efficiency, but also obtains reliable detection results.
- Fig. 1 is a schematic flow chart of a mixed sample test method for a consumer product chemical test item of the present invention
- Figure 2 The statistical diagram of the optimization model of the classic scheme one-time mixing method
- Figure 3 is the causality diagram used in the quantitative analysis of the uncertainty component
- Figure 4 is a schematic diagram of the evaluation process of the relative expansion uncertainty of the present invention.
- Figure 5 shows the contents of Resolutions No. 217 and No. 218 of the International Toy Standards Committee of ISO/TC181 "Toy Safety" in 2019.
- the present invention intends to establish a mixed sample test method and device for the mixed sample detection technology of consumer products, so as to provide the best and maximum mixed sample number and risk threshold for mixed sample test under different conditions.
- the method and device are suitable for the calculation of the maximum mixed number suitable for mixed inspection in consumer product inspection.
- the current inspection agencies have a great demand for mixed sample testing for cost-saving considerations.
- the determination of the maximum number of mixed inspections is mostly unfounded. Basically, they rely on the detection limit of the instrument and standard testing. The limit and the test experience value are simply added together, lacking scientificity and accuracy.
- the present invention selects representative products and test items based on comprehensive consideration of regulatory limit requirements, sample uniformity, method detection limit, linear range, measurement uncertainty, mixed sample amount, mixed sample ratio, and mixed sample process.
- a series of parameters such as physical and chemical changes, based on the application of probability theory, mathematical statistics and other theories, combined with strict statistical analysis of nearly 100,000 sample data collected from a large number of testing institutions, have refined the data that can be applied in the field of consumer goods. There are scientific, operability and practical mathematical models in the testing items.
- the probability of positive or unqualified for a certain item of a certain product is p
- the probability of is: q K , only test once at this time; the probability of K mixed samples being positive or unqualified is: 1-q K , at this time, you need to split the test one by one, and test K+1 times in total. If the total number of samples is n, the total number of detections N after grouping is shown in formula (1) and Table 1:
- the wrong conclusion may be drawn, that is, the mixed sample containing positive or unqualified samples is wrongly detected as negative in the first test Or qualified, etc. Therefore, when determining the size of the mixed sample, one should not only pursue the maximization of benefits and efficiency, but also conduct a comprehensive analysis of the factors that affect the accuracy of the results. Among them, such as the type of test items, limit, material, dilution ratio, method detection limit, etc. are all influencing factors. In addition, due to the uncertainty of the mixed test, the selection of the safety factor is also necessary.
- K max the maximum number of samples that can be mixed, rounded to the end
- L--Limit/report limit of the test item mg/kg, select the corresponding value according to different standards and regulations or customer requirements;
- the relative expanded uncertainty around the limit concentration, which represents the reasonable dispersion of the measured value, and the parameter associated with the measurement result is called the measurement uncertainty.
- the expanded uncertainty is the quantity that determines the interval of the measurement result, and most of the value distribution that is reasonably assigned to the measured value is expected to be contained in this interval.
- the expanded uncertainty is the measurement uncertainty expressed by the multiple of the synthetic standard uncertainty.
- u rel is the relative standard uncertainty around the limit concentration
- k is the inclusion factor, and the confidence is 95%
- k 2
- u rel,1 is the relative standard uncertainty of the method reproducibility, that is, reproducibility The standard deviation of the data
- u rel,2 the relative standard uncertainty of the method recovery
- u rel,3 the relative standard uncertainty of the standard curve, that is, the standard deviation of the reproducibility data. Either type A or B evaluation of uncertainty can be performed.
- U rel the relative expanded uncertainty of the test result data near the limit concentration
- u the standard uncertainty near the limit concentration, in mg/L
- L the limit or reporting limit of the item to be tested, in mg/ kg
- the limits of consumer product testing items generally involve the sum of the content of each detected object. For example, the sum of the content of three phthalates in toy products cannot exceed 0.1%, and the sum of the content of 18 kinds of polycyclic aromatic hydrocarbons cannot exceed 1 mg. /kg, therefore, if the limit is the sum of all detected objects, U rel is calculated as follows: (5) and (6):
- IDL--Instrument detection limit mg/L
- the maximum value K max of the number of samples that can be mixed is obtained.
- Step 2 Identify the source of uncertainty
- the quantification of the uncertainty component can generally be analyzed through the causality diagram, as shown in Figure 3; the fourth step. According to formula (5)
- the mixed sample should be tested only once as much as possible, and there is no need to split and test again, reducing the total number of tests;
- the positive rate or unqualified rate of the items to be tested should be low, such as less than 20%;
- the report limit of the test item of a single sample is higher than the method detection limit
- the limit shall be higher than the reporting limit of a single sample.
- the mixed sample test model can be used.
- the mathematical model established by the present invention can scientifically and quickly determine whether the item can be mixed inspection and scientifically calculate the maximum number of mixed samples when conducting chemical inspection tests on consumer products.
- Using the mixed sample inspection method can reduce the number of tests in chemical analysis, achieve the purpose of reducing workload and improving work efficiency; it can also reduce the use of reagents, thereby reducing environmental emissions, reducing the funds for processing a large number of reagents, and reducing testing costs. This has obvious economic and social benefits whether it is for the enterprise or the country.
- the mixed detection method reduces the workload by 57% compared with the sample-by-sample detection, which is the highest value among all the mixed numbers, and the efficiency Reach the highest.
- Example 1 Testing of phthalates in toys with mixed samples
- X i the content of the component in the test sample,% ;
- a i the peak area of the component to be tested in the sample
- V The final constant volume of the sample, ml
- Steps Weigh about 0.02g of certified reference material, and dilute to 100mL (concentration of 200mg/L), pipette 10mL, 2.5mL, 1.25mL, 0.25mL and 0.1mL to 50mL (concentration of 40mg/L , 10mg/L, 5mg/L, 1mg/L, 0.4mg/L).
- the maximum uncertainty of the standard phthalate plasticizer is: 5%.
- the relative standard uncertainty of the 50mLA volumetric flask is: 0.1%;
- Cobs is the average value of the measured value
- C CRM is the standard value of the certified reference material
- Sobs is the standard deviation of the measured value
- n is the number of measurements.
- S std is the standard deviation of the spiked recovery rate
- the entire matrix is completely extracted, so there is no significant difference between the spiked substance and the matrix and can be ignored.
- Plasticizer u(m)/m u(V)/V u(STD) u(R) u(RSD) u(C sam )/C sam U(C sam ) DBP 0.064 0.049 5.3 2.5 4.2 7.2 10.5 BBP 0.064 0.049 5.3 2.7 6.9 9.1 11.2 DEHP 0.064 0.049 5.3 4.5 6.5 9.6 12.1
- the unqualified rate of the agent is 0.5%.
- the mixing number is between 2 and 17.
- the mixing number that saves the most work is 15, which can save 86% of the work. Therefore, the most suitable mixing number is 15.
- the detection limit of one phthalate in a single sample is 187 mg/kg
- the detection limit of the sum of three phthalates in a single sample is 560 mg/kg.
- the maximum DEHP content can also be calculated as follows:
- Example 2 Mixed samples test the content of aromatic amines in textiles.
- the reporting limit refers to each aromatic amine (not the sum of 22 aromatic amines)
- the positive detection rate of banned aromatic amines in textiles is 5% (most of them are aniline, which is the decomposition product of 4-aminoazobenzene, and additional tests are needed to determine whether it actually contains 4-aminoazobenzene.
- Benzene by looking up Table 2, between the mixing number 2-22, the mixing number that saves the most work is 5, which can save 57% of the work, so the most suitable mixing number is 5.
- the detection limit of the method is 1 mg/kg, which far meets the requirement of the report limit of 5 mg/kg.
- the maximum content can also be calculated as follows:
- Resolution 218 of the meeting decided to re-appoint Huang Lina (the applicant of the present invention) as the convener of the ISO/TC181/WG6 working group to undertake the revision task of ISO 8124-6 "Toys and Children's Products Phthalates" ,
- the task content is mainly to introduce the mixed mathematical model of the present invention (for details, please refer to appendix 2). This is of milestone significance for China to occupy the strategic commanding heights of international standards, and it also reflects the originality of the present invention from one side.
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- Automatic Analysis And Handling Materials Therefor (AREA)
Abstract
一种消费品化学检测项目的混样定量测试方法与装置,该测试方法包括:结合法规限量要求、测量不确定度、混样量以及混样比例等参数,求出保证检测结果准确性的最大混合数,再根据合格率、混样数和节省工作量之间的关系建立一个可查询的表格,对于各种待测项目,直接查表即可得出不同混合数下节省的工作量,当混合数未超过最大值,且对应的节省的工作量最大时,该混合数即为最佳混合数,按照该混合数进行混样测试,既节省了工作量,提高了检测效率,又获得了可靠的检测结果。
Description
本发明涉及化学检测技术领域,特别是涉及一种消费品化学检测项目的混样定量测试方法与装置。
随着人民生活水平的提高,消费品的花色品种日益增多,功能也不断增强,因此随之而来,在消费品使用中存在的化学类风险也逐渐较为突出地暴露出来,如:纺织品的甲醛、禁用偶氮着色剂含量超标,皮革产品重金属超标、玩具产品增塑剂超标等。做好消费品安全检测工作,保障消费者安全健康,生产企业和质量检验认证机构责无旁贷。随着“一带一路”项目的铺开,经济全球化的发展,检测意愿的提升,促进检测行业持续高速发展,2015年全球检测行业市场规模达到12257亿美元,其中消费品占9%的份额,预计未来几年将保持5%-7%的年均增速。而我国检测行业的市场规模也在快速增长,2015年已经达到2574亿元。此外,对于很多生产企业来说,产品出厂之前的质量检测是发现不合格产品的有效手段,有利于保证产品的质量。在环保意义层面上讲,数量这么庞大的检测机构,检测过程中产生的污染气体的排放对环境产生污染,检测过程中试剂的使用对实验人员产生的健康隐患都是现实存在的大问题;从检测机构的经济效益层面上讲,消费品检测涉及的样品种类繁多,检测项目繁杂,检测周期长,检测人员的工作任务繁重,试剂的回收处理都需要消耗高额的费用。故在把好质量关的前提下,优化检验流程,提高检测效率,减少污染排放,以“更快、更好、更环保”的理念推动行业的健康发展是国家和质量检验认证机构的重中之重。
每批样品都进行测试,需要花费大量人力、物力、金钱,且不环保。此外,经过统计,大多数检测项目阳性检出率都低于1%。所以选择简单易行,科学有效的筛查方法十分重要。这时候,混合检验法应势而出现了。混合检验法是将若干份样本并为一组,如果对应的是判断单个样本的待测项目是阴性或者合格否,那么当这组混合样本的待测项目是阴性或者合格(以单个样本计算),则结论是:只检验一次,这些混合的样本的待测项目都是阴性或者合格;当混合样本的待测项目是阳性或者不合格(以单个样本计算),则再把混合样本中的单个样本逐个检验。利用混合样本检验法,首先可以在检测分析中减少检测次数,最根本的收益是可以达到减少工作量,提高工作效率,同时大大减少测试成本,从而取得明显的经济效益和社会效益;其次混合样本检验可以减少溶剂和试剂的使用,从而减少对环境的污染和实验人员健康的影响。
早在1943年,Dorfman将其用在感染性疾病研究,将若干份血清并为一组,如结果为阴性,则只需检验一次,如结果为阳性,则分别检验每份血清,使得检测效率大大提高,但会使检测灵敏度降低。目前,在不同行业中,例如流行病学、DNA检测、昆虫学、食品和消费品领域中混合检验均有报道。具体 在消费品领域中,仅GB/T 22048-2015,ISO 8124-6:2018玩具及儿童用品增塑剂检测标准和ISO14362-1:2017纺织品偶氮着色剂检测标准有提及混合测试的要求,而且只能在类似材料中进行,不同类型的材料不可进行混合测试,因为这些混样测试缺少科学地建模,因此检测选用较为保守的方式进行,只能用于筛选定性,并不能用于准确定量,达不到筛选的最大效率。
因此哪些检验项目适合混合检验,混合检验的最大数目如何确定这些核心问题非常需要近一步的深入研究。混合样本方法的关键是如何确定混合样本大小,即混合多少个样本作为一个待测的混合样本,以及在满足一定精度要求下应该检测多少个这样的混合样本,称为混合样本量、或检测次数。混合检验法若应用不当,不但不能节约时间和成本,还会直接影响检测结果的准确性,本发明首次提出把不确定度引入混样测试模型中,选取具有代表性的产品和检测项目为基础,在应用概率论、数理统计等理论基础之上,结合近十万个以上样本数据的严格统计分析,提炼出了可以应用在消费品领域的检测项目中并具有科学性、可操作性及实用性的混样测试定量模型。
发明内容
基于此,有必要提供一种消费品化学检测项目的混样定量测试方法与装置,平衡工作量和检测结果准确性之间的矛盾,区别于现有的定性筛选方法,创新性把该测试方法的合成扩展不确定度引入混合测试模型,明确确定最佳混样数目,形成科学的混样测试定量模型。
为了实现上述目的,本发明采用的技术方案如下。
一种消费品化学检测项目的混样定量测试方法,包括如下步骤:
获取待测项目的相关数据,并录入下述模型,求取最大混合数:
式中,K
max,最大混合数,去尾取整;L,待测项目的限量或者报告限,单位mg/kg;U
rel,限量浓度附近的相对扩展不确定度;F,限量或者报告限的安全系数;m
tot,混合测试样品的总质量,单位g;V,定容溶液的体积,单位mL;IDL,仪器检测限,单位mg/L;M,限量或者报告限对应的待测项目数;
如果限量只是一个化学检测项目,则U
rel,限量浓度附近的相对扩展不确定度根据以下公式计算:
U
rel=u
rel×k
式中,u
rel,限量浓度附近的相对标准不确定度;k,包含因子,取置信度为95%,k=2;u
rel,1,方法再现性的相对标准不确定度,即再现性数据的标准偏差;u
rel,2,方法回收率的相对标准不确定度;u
rel,3,标准曲线的相对标准不确定度,即再现性数据的标准偏差;
如果限量是多个化学检测项目之和,则U
rel,限量浓度附近的相对扩展不确定度根据以下公式计算:
U
rel=u÷L×k
式中,u,限量浓度附近的标准不确定度,单位mg/L;L,待测项目的限量或者报告限,单位mg/kg;k,包含因子,取置信度为95%,k=2;u
1,待测项目1的标准不确定度,单位mg/kg,u
2,待测项目2的标准不确定度,单位mg/kg,u
3,待测项目3的标准不确定度,单位mg/kg;
确定待测项目的阳性率或者不合格率,查询节省工作量效率表,在2~K
max之间选取节省工作量最大的混合数作为最合适的混合数,所述节省工作量效率表按照下式建立而成:
式中,S表示节省的工作量,q表示阳性率/不合格率,K表示混合数;
按照最合适的混合数对待测样品进行分组,并进行混样测试。
优选地,混样测试后,计算单个测试样本的待测物质的最大含量,若超出修正后的限量或者报告限,则将混合样本拆分单独再测。
优选地,待测项目的阳性率/不合格率低于20%。
优选地,限量/报告限的安全系数F的取值范围为0%-100%。
一种消费品化学检测项目的混样定量测试装置,包括如下模块:
最大混合数求取模块,用于获取待测项目的相关数据,并录入下述模型,求取最大混合数:
式中,K
max,最大混合数,去尾取整;L,待测项目的限量或者报告限,单位mg/kg;U
rel,限量浓度附近的相对扩展不确定度;F,限量或者报告限的安全系数;m
tot,混合测试样品的总质量,单位g;V,定容溶液的体积,单位mL;IDL,仪器检测限,单位mg/L;M,限量或者报告限对应的待测项目数;
如果限量只是一个化学检测项目,则U
rel,限量浓度附近的相对扩展不确定度根据以下公式计算:
U
rel=u
rel×k
式中,u
rel,限量浓度附近的相对标准不确定度;k,包含因子,取置信度为95%,k=2;u
rel,1,方法再现性的相对标准不确定度,即再现性数据的标准偏差;u
rel,2,方法回收率的相对标准不确定度;u
rel,3,标准曲线的相对标准不确定度,即再现性数据的标准偏差;
如果限量是多个化学检测项目之和,则U
rel,限量浓度附近的相对扩展不确定度根据以下公式计算:
U
rel=u÷L×k
式中,u,限量浓度附近的标准不确定度,单位mg/L;L,待测项目的限量或者报告限,单位mg/kg; k,包含因子,取置信度为95%,k=2;u
1,待测项目1的标准不确定度,单位mg/kg,u
2,待测项目2的标准不确定度,单位mg/kg,u
3,待测项目3的标准不确定度,单位mg/kg;
最佳混合数确定模块,用于根据待测项目的阳性率或者不合格率,查询节省工作量效率表,在2~K
max之间选取节省工作量最大的混合数作为最合适的混合数,所述节省工作量效率表按照下式建立而成:
式中,S表示节省的工作量,q表示阳性率或者不合格率,K表示混合数;
混样测试模块,用于按照最合适的混合数对待测样品进行分组,并进行混样测试。
优选地,混样测试模块在混样测试后,计算单个测试样本的待测物质的最大含量,若超出修正后的限量或者报告限,则将混合样本拆分单独再测。
优选地,待测项目的阳性率/不合格率低于20%。
优选地,限量/报告限的安全系数F的取值范围为取值范围为0%-100%。
本发明结合法规限量要求、测量不确定度、混样量以及混样比例等参数,求出保证检测结果准确性的最大混合数,再根据合格率、混样数和节省工作量之间的关系建立一个可查询的表格,对于各种待测项目,直接查表即可得出不同混合数下节省的工作量,当混合数未超过最大值,且对应的节省的工作量最大时,该混合数即为最佳混合数,按照该混合数进行混样测试,既节省了工作量,提高了检测效率,又获得了可靠的检测结果。
图1为本发明消费品化学检测项目的混样测试方法的流程示意图;
图2经典方案一次混样法最优化模型统计图;
图3为不确定度分量量化分析所采用的的因果关系图;
图4为本发明相对扩展不确定度的评估过程示意图;
图5为2019年ISO/TC181“玩具安全”国际玩具标委会年有关217号和218号决议内容。
本发明意图建立一种消费品混样检测技术的混样测试方法与装置,实现在不同条件下给出混样测试的最佳与最大混样数目以及风险阈值。该方法与装置适宜于消费品检验中适合混合检验的最大混合数目的计算。
目前的检验机构,出于节约成本的考虑,对混合样品测试有很大的需求,但是混合检验最大数目的确定,大多数是无据可依的,基本上都是依靠仪器检测限,标准检测限和检验经验值简单加和起来,缺乏科学性和准确性。本发明选取具有代表性的产品和检测项目为基础,在综合考虑法规限量要求、样品均匀性、方法检测限、线性范围、测量不确定度、混样量以及混样比例、混样过程中的物理化学变化等一系列参数,在应用概率论、数理统计等理论基础之上,结合从广大检测机构收集回来的近十万个以上 样本数据的严格统计分析,提炼出了可以应用在消费品领域的检测项目中并具有科学性、可操作性及实用性的数学模型。
确定混合检验数目的数学模型的建立
1)工作量分析
若某类产品的某项项目的阳性或者不合格的概率为p,则对应的阴性或者合格的概率为:q=1-p,由于事件的独立性,而K个混合的样本呈阴性或者合格的概率为:q
K,此时只测试一次;K个混合样本呈阳性或者不合格的概率为:1-q
K,此时需要拆分逐一测试,一共测试K+1次,若样本总数是n,则分组后的检测总数N见式(1)以及表1:
式中:
N--检测总的次数;
q--某类产品的某项项目的阴性或者合格的概率;
K--混合数;
n--样本总数。
表1概率分布
显然,当混合分组后的检测总数N小于样本总数n,才可以达到减少工作量,提高工作效率的目的,见式(2)和(3):
并且当阴性或者合格的概率q固定,随着混合数K的变化,节省的工作量S值达到最大时,对应K值,就是理论上效率最佳的混合数。
2)最大混合数分析
考虑到混合检测方案筛检的准确性问题,如果仅从数学角度进行一些简单统计分析,可能得出错误的结论,即含有阳性或者不合格样本的混合样本在第一次检测中错检为阴性或者合格等。因此,在确定混合样本大小时,不可单单只追求利益与效率的最大化,同时也应对影响结果准确性判断的因素进行综合分析。其中,诸如检测项目的种类、限量、材料,稀释比、方法检出限等都是影响因素。此外,由于混合测试具有不确定性,安全系数的选取也是必须的。
a.保证得到正确的测定结论,得出确定混合样本大小K
max的公式,见式(4):
式中:
K
max--可以混合的样本数的最大值,去尾取整;
L--检测项目的限量/报告限,mg/kg,根据不同标准法规要求或者客户要求选取对应的数值;
U
rel--限量浓度附近的相对扩展不确定度,其中表征合理的赋予被测量之值的分散性,与测量结果相联系的参数,称为测量不确定度。扩展不确定度是确定测量结果区间的量,合理赋予被测量之值分布的大部分可望含于此区间,扩展不确定度是由合成标准不确定度的倍数表示的测量不确定度。
由于消费品化学某项目的数学模型都是大部分相乘,如果限量只是一个化学项目,则U
rel,限量浓度附近的相对扩展不确定度根据以下公式计算:
U
rel=u
rel×k
式中,u
rel,限量浓度附近的相对标准不确定度;k,包含因子,取置信度为95%,k=2;u
rel,1,方法再现性的相对标准不确定度,即再现性数据的标准偏差;u
rel,2,方法回收率的相对标准不确定度;u
rel,3,标准曲线的相对标准不确定度,即再现性数据的标准偏差。都可进行不确定度的A类评定或者B类评定。
如果限量是多个化学项目之和,则U
rel,限量浓度附近的相对扩展不确定度根据以下公式计算:
U
rel=u÷L×k
式中,U
rel,测试结果数据在限量浓度附近的相对扩展不确定度;u,限量浓度附近的标准不确定度,单位mg/L;L,待测项目的限量或者报告限,单位mg/kg;k,包含因子,取置信度为95%,k=2;u
1,项目1的标准不确定度,单位mg/kg,u
2,项目2的标准不确定度,单位mg/kg,u
3,项目3的标准不确定度,单位mg/kg。
其中消费品检测项目的限量一般涉及到是各检出物的含量之和,例如玩具产品中三种邻苯二甲酸酯含量之和不能超过0.1%,18种多环芳烃含量之和不能超过1mg/kg,因此,如果限量是各检出物之和,则U
rel见如下式(5)和式(6)计算:
u(a),u(b),…:各检出物的标准不确定度分量;
u(y):各检出物之和的合成标准不确定度;
注:减法的处理原则和加法相同。
F--限量/报告限的安全系数,因检测能力不一样、材料多样性,各实验室可根据经验与历史数据选取合适的安全系数,一般推荐取值范围为0%-100%;
m
tot--混合测试样品的总质量,g;
V--定容溶液的体积,mL;
IDL--仪器检测限,mg/L;
M--限量/报告限对应的测试项目数,如果某限量是三个检测项目之和,则M=3。
根据上式,从方法检出限考虑确保混合检测结果的准确性,得出可以混合的样本数的最大值K
max。
b.U
rel限量浓度附近的相对扩展不确定度的评估,如图4所示,包括如下步骤
第一步.规定被测量;
第二步.识别不确定度的来源;
第三步.不确定度分量的量化,一般可通过因果关系图分析,如图3所示;第四步.根据公式(5)
和公式(6)计算相对扩展不确定度。
混样测试的程序
1.首先判断是否可以进行混样测试,需要满足的条件有以下;
(1)混合样本尽量只测试一次,不需要拆分再测试,减少总测试次数;
(2)待测项目的阳性率或者不合格率要低,比如低于20%;
(3)检测的样本混合后,待测项目如果会产生化学反应,即性质发生改变,则不能混合测试,比如测试pH值;
(4)如果是关注样本的待测项目是否检出,则单个样本的待测项目的报告限要高于方法检出限;
(5)如果是关注样本的待测项目是否合格,则限量要高于单个样本的报告限。
2.以上条件满足后,就可以使用混样测试模型。
(1)计算该项目的扩展不确定度,确定安全系数;
(2)用数学模型公式(4)计算出的最大混合数K
max;
(3)根据待测项目的阳性率/不合格率,查表,选取混合数是2~K
max之间,节省工作量最大的混合数作为最合适的混合数;
(4)测试混合样品后,计算出单个测试样本的某个待测物质的最大含量并与修正后的报告限或者限量进行比较,确定是否拆分单独再测。
本发明建立的数学模型,对进行消费品化学检验测试时,可以科学地快速地判断是否该项目能否进行混合检验以及科学计算出最大混合样品的个数。利用混合样本检验法可以在化学分析中减少检测次数,达到减少工作量,提高工作效率的目的;还可以减少试剂的使用,从而减少对环境的排放,减少处理大量试剂的资金,降低测试成本,这无论是对企业或者国家都有明显的经济效益和社会效益。
如上文提到的公式(2):
和公式(3)
当阴性或者合格的概率q是100%时(即:阳性或者不合格的概率p则为0),混合数K>1就可以节省工作量,即混合多少个都可以节省工作量,如这时候取K=2,则S=0.5,可节省一半的工作量;如取K=4,则S=0.75,可节省四分之三的工作量。各种阳性率p以及混合数K所对应的节省工作量见表2和图2。
表2阳性率或者不合格率与混合数对应的节省工作量效率表
1、当阳性率或者不合格率p=0(即没有检出或者都合格),混合数选K=2时,则S=0.5,节省一半的工作量。最佳混合数就是全部混合,只做一次测试。
2、当阳性率或者不合格率p=0.05(即5%),混合数选K=5时,混合检测法比逐个样本检测减少57%的工作量,是所有混合数中最高的值,效率达到最高。
3、如果阳性率或者不合格率p=0.10(即10%),则混合4个时达到最高效率。
4、而当阳性率或者不合格率提高到p=0.30(即30%),则只有混合3个时达到最高效率,但也只能节省1%的工作量。这时候,如果混合10个,反而增加了7%的工作量。
5、如果之后的阳性率再提高,无论怎么混合,都达不到减少工作量的目的。
所以从表2看到,只要是科学混合样品,都可以达到节省工作量的目的。
下面以两个具体实施例进一步解释本发明消费品化学检测项目的混样测试方法与装置。
例子1.混合样品测试玩具中邻苯二甲酸酯项目
国家玩具安全标准GB 6675.1-2014中规定玩具中的三种邻苯二甲酸酯(DBP,BBP,DEHP)的总含量不可大于1000mg/kg,按照GB/T 22048-2015《玩具及儿童用品中特定邻苯二甲酸酯增塑剂的测定》测试。通过分析该测试项目的不合格率、报告限和限量,确定可以使用混样测试模型,过程如下:。
1.测定过程
2.测定过程如图4所示。数学模型
样品中各种邻苯二甲酸酯增塑剂组分的含量按下式计算:
X
i=(A
i×C
s×V
i)/(A
s×m)
式中:X
i:样品中待测组分的含量,%;;
A
i:样品中待测组分的峰面积;
C
s:标准溶液的浓度,mg/L;
V:样品最终定容体积,ml;
As:标准溶液中待测组分的峰面积;
m:样品量,g
3.标准不确定度来源
来源 | 评定方法 |
样品质量 | 引用天平测量不确定度 |
体积 | 引用容量仪器容量不确定度/加液器体积不确定度 |
标准物质 | 引用证书的相对标准不确定度 |
偏差(回收率) | CRM样品和加标的回收率测量不确定度 |
精密度 | 基于不同样品的平行试验 |
4.计算分量标准不确定度
4.1样品质量的相对不确定度u(m)/m
由天平测量不确定度的评估(UE-CW1)可知,质量测量在1g处的测量不确定度0.00064g。因此,m=1g时,u(m)/m=0.00064g/1g=0.00064。
4.2体积的相对不确定度u(V)/V
25mLA级容量瓶的最大允许误差为0.12%,假定为三角形分布,u(V)/V=0.0012/√6=0.00049。(方法B)
4.3标准物质的相对不确定度u(STD)
步骤:称取有证标准物质0.02g左右,定容到100mL(浓度为200mg/L),分别移取10mL、2.5mL、1.25mL、0.25mL和0.1mL定容到50mL(浓度为40mg/L、10mg/L、5mg/L、1mg/L、0.4mg/L)。
由邻苯二甲酸酯增塑剂标准品的证书可查得:邻苯二甲酸酯增塑剂标准品最大的不确定度为: 5%,按均匀分布,可得其相对标准不确定度为:5%/√3=2.9%;
查天平的不确定度程序,称量0.02g左右的相对标准不确定度为:0.00064g/0.02g=3.2%;
50mLA级容量瓶的相对标准不确定度为:0.1%;
查移液枪最大的相对标准不确定度分别为:3%;
因此,标准工作溶液的最大相对标准不确定度为:
4.4回收率的相对标准不确定度u(R)
取有证标准物质RMC010蓝色PVC,按程序平行测定7次,测定结果如下(单位:mg/kg):
式中C
obs为测量值的平均值,C
CRM为有证标准物质的标准值,S
obs为测量值的标准偏差,n为测量次数。
方法B:
查表得t
0.05,6(t
0.05,6=2.45),上表中t值均小于2.45,表明回收率与100%无显著性差异,结果计算时无需用回收率对结果进行校正。
4.4.2计算加标样品标准偏差:u(R
s)
分别取PU、涂层、纺织品、液体等一系列代表性样品,分别加两个标准浓度加标1和加标2(分别加入0.5mL和5mL的200mg/L标准储备溶液,加标浓度为分别为4mg/L和40mg/L,相当于样品浓度为100mg/kg和1000mg/kg),按程序平行测试7次,计算回收率见下表(单位%)。
式中S
std为加标回收率的标准偏差,n为加标测量次数。(本次测量n=7)
4.4.3计算u(R
rep)
对于溶剂萃取方法测定邻苯二甲酸酯,整个基质被完全萃取,因此加标物和基质无显著差别,可忽略。
4.4.4回收率的相对标准不确定度计算
4.5精密度的相对标准不确定度u(RSD)
不同日期对不同类型样品进行一系列平行测试,以获得该程序的总的随机变化(精密度),测试结果见下表,其中10为CRM RMC010蓝色PVC,单位:mg/kg
u(RSD)=标准偏差/√2
DBP
BBP
DEHP
6.扩展不确定度计算
以上相对标准不确定分量计算结果列于下表。
扩展不确定度:U(C
sam)=k*[u(C
sam)/C
sam]
取包含因子k=2,合成上述分量,计算结果见下表。
合成相对标准不确定度
增塑剂 | u(m)/m | u(V)/V | u(STD) | u(R) | u(RSD) | u(C sam)/C sam | U(C sam) |
DBP | 0.064 | 0.049 | 5.3 | 2.5 | 4.2 | 7.2 | 10.5 |
BBP | 0.064 | 0.049 | 5.3 | 2.7 | 6.9 | 9.1 | 11.2 |
DEHP | 0.064 | 0.049 | 5.3 | 4.5 | 6.5 | 9.6 | 12.1 |
计算该项目的扩展不确定度,假设DBP,BBP,DEHP三种邻苯二甲酸酯的相对扩展不确定分别评定为:11%,12%,12%,根据公式5,可以计算出DBP+BBP+DEHP的相对扩展不确定为:20%。
根据公式4和计算出来的扩展不确定度,计算可以混合的样本数的最大值K
max=17,即可以最多17个混合,统计上万个玩具及儿童用品中邻苯二甲酸酯类增塑剂的不合格率为0.5%,查表2,混合数2~ 17之间,节省工作量最大的混合数是15,可以节省86%的工作量,因此最合适的混合数是15。此时,单个样本一种邻苯二甲酸酯的方法检出限为187mg/kg,单个样本三种邻苯二甲酸酯之和的方法检出限为560mg/kg。
假设15个混合测试样本为:绿色PVC、红色ABS、蓝色PU、…、灰色PVC,各自的质量分别为0.0671g,0.0679g,0.0674g,…,0.0679g。定容25ml后的DEHP测试结果为1.6mg/L。则混合样本中DEHP的平均含量:
单个样本中DEHP最大含量:
因为15个样本的质量相近,因此DEHP最大含量也可以这样计算:
W
max=W
avg×混合数=40×15=600mg/kg
因为限量浓度附近的相对扩展不确定度U
rel=20%,安全系数F=80%,修正后的限量为:
L’=L×(1-U
Rel)×F=1000×(1-20%)×80%=640mg/kg
因为限量是三种之和,所以还涉及到怎么计算其它未检出的项目的含量,按不同计算方法(包括按0计算,按方法检出限的一半计算,按方法检出限计算),有不同的结论,其报告结果见表4:
表4邻苯二甲酸酯检测报告
1:DBP和BBP的含量各按等于0计算;
2:DBP和BBP的含量各按等于方法检出限的一半计算;3:DBP和BBP的含量各按小于等于方法检出限计算;
4:600mg/kg小于修正后的限量640mg/kg;
5:787mg/kg和974mg/kg大于修正后的限量640mg/kg。
例子2.混合样品测试纺织品中禁用芳香胺含量。
测试纺织品中的禁用芳香胺含量是国际纺织品服装贸易中最重要的品质监控项目一,也是生态纺织 品最基本的质量指标之一。德国政府于1994年颁布的法令规定,凡是进入德国的皮革、纺织品必须进行禁用芳香胺检测,紧接着世界各国以及
(国际环保纺织协会)纷纷效法。所以全球检测机构测试纺织品中禁用芳香胺含量的量是非常巨大的,因此混和样品测试非常必要。
按照ISO 14362-1:2017测试纺织品中的22种禁用芳香胺时,如果选择单个禁用芳香胺的报告限为:5mg/kg,而U
rel=0%(因为不涉及限量,不需要考虑不确定度),安全系数F=90%,按照本方法测试,称取1g处理,最后定容到2ml(mtot=1g,V=2ml),使用A.3.2的三重四级杆串联液质联用仪HPLC-MS-MS测试的检测限IDL=0.1mg/L(检测限最不灵敏的一种芳香胺)。因为报告限是指每一个芳香胺(不是22种芳香胺之和),因此测试项目数M=1,计算可以混合的样本数的最大值K
max=22,即可以最多22个样品混合。,通过机构统计数据得知,纺织品中禁用芳香胺的阳性检出率为5%(其中多数是检出了4-氨基偶氮苯的分解产物苯胺,需要额外测试是否真正含有4-氨基偶氮苯),通过查询表2,在混合数2~22之间,节省工作量最大的混合数是5,可以节省57%的工作量,因此最合适的混合数是5。混合样本的一种芳香胺的方法检出限MDL=0.2mg/kg(按混合总质量计算),如果要报单个样本的方法检出限,则要提高5倍,单个样本一种芳香胺的方法检出限为1mg/kg,远远满足报告限5mg/kg的要求。
假设5个混合测试样本为:红色布、绿色布、蓝色布、黄色布、紫色布,各自的质量分别为0.2000g,0.2005g,0.2004g,0.1998g,0.1996g。定容2ml后的联苯胺测试结果为0.41mg/L。则混合样本中联苯胺的平均含量:
单个样本中联苯胺最大含量:
因为5个样本的质量相近,因此最大含量也可以这样计算:
W
max=W
avg×混合数=0.82×5=4.1mg/kg
因为U
rel=0%(因为不涉及限量,不需要考虑不确定度),安全系数F=90%,修正后的限量为:
L’=L×(1-U
rel)×F=5×(1-0%)×90%=4.5mg/kg
其报告结果见表5:
表5芳香胺检测报告
4.1mg/kg小于修正后的报告限4.5mg/kg。
国际标准ISO 8124-6:2018《玩具和儿童用品中邻苯二甲酸酯》的附录D已经由本发明申请者推动后引入了混样测试的概念和经验方案等(详细信息请参看附件1),已经正式发布并使用,受到广大检测机构采纳和好评;但是这个版本没有数学模型,缺乏针对各种待分析化学成分特性、化学仪器能力,前处理技术等数学量化分析,为此,在2019年9月在韩国首尔举办的ISO/TC181“玩具安全”国际玩具标委会年会上,经过各国充分讨论,在217号决议中决定在下一版的ISO 8124引入本发明的内容,即混样测试的数学模型作为该国际标准的正式规范性附录发布,由黄理纳(本发明申请人)担任项目领导人。同时,会议的218号决议决定再次任命黄理纳(本发明申请人)为ISO/TC181/WG6工作组召集人,承担ISO 8124-6《玩具及儿童用品邻苯二甲酸酯》的修订任务,任务内容主要就是要引入本发明的混样数学模型(详细信息请参看附件2)。这对于中国占领国际标准的战略制高点具有里程碑般的意义,也从一个侧面反映了本发明具有独创性。
以上所述实施例仅表达了本发明的实施方式,其描述较为具体和详细,但并不能因此而理解为对发明专利范围的限制。应当指出的是,对于本领域的普通技术人员来说,在不脱离本发明构思的前提下,还可以做出若干变形和改进,这些都属于本发明的保护范围。因此,本发明专利的保护范围应以所附权利要求为准。
Claims (8)
- 一种消费品化学检测项目的混样定量测试方法,其特征在于,包括如下步骤:获取待测项目的相关数据,并录入下述模型,求取最大混合数:式中,K max,最大混合数,去尾取整;L,待测项目的限量或者报告限,单位mg/kg;U rel,限量浓度附近的相对扩展不确定度;F,限量或者报告限的安全系数;m tot,混合测试样品的总质量,单位g;V,定容溶液的体积,单位mL;IDL,仪器检测限,单位mg/L;M,限量或者报告限对应的待测项目数;如果限量只是一个化学检测项目,则U rel,限量浓度附近的相对扩展不确定度根据以下公式计算:U rel=u rel×k式中,u rel,限量浓度附近的相对标准不确定度;k,包含因子,取置信度为95%,k=2;u rel,1,方法再现性的相对标准不确定度,即再现性数据的标准偏差;u rel,2,方法回收率的相对标准不确定度;u rel,3,标准曲线的相对标准不确定度;如果限量是多个化学检测项目之和,则U rel,限量浓度附近的相对扩展不确定度根据以下公式计算:U rel=u÷L×k式中,u,限量浓度附近的标准不确定度,单位mg/L;L,待测项目的限量或者报告限,单位mg/kg;k,包含因子,取置信度为95%,k=2;u 1,待测项目1的标准不确定度,单位mg/kg,u 2,待测项目2的标准不确定度,单位mg/kg,u 3,待测项目3的标准不确定度,单位mg/kg;确定待测项目的阳性率或者不合格率,查询节省工作量效率表,在2~K max之间选取节省工作量最大的混合数作为最合适的混合数,所述节省工作量效率表按照下式建立而成:式中,S表示节省的工作量,q表示阳性率或者不合格率,K表示混合数;按照最合适的混合数对待测样品进行分组,并进行混样测试。
- 根据权利要求1所述的消费品化学检测项目的混样定量测试方法,其特征在于,混样测试后,计算单个测试样本的待测物质的最大含量,若超出修正后的限量或者报告限,则将混合样本拆分单独再测。
- 根据权利要求1或2所述的消费品化学检测项目的混样定量测试方法,其特征在于,待测项目的阳性率/不合格率低于20%。
- 根据权利要求1或2所述的消费品化学检测项目的混样定量测试方法,其特征在于,限量/报告限的安全系数F由测试实验室各自自定,取值范围为0%-100%,和实验室各自的测试水平有关。
- 一种消费品化学检测项目的混样定量测试装置,其特征在于,包括如下模块:最大混合数求取模块,用于获取待测项目的相关数据,并录入下述模型,求取最大混合数:式中,K max,最大混合数,去尾取整;L,待测项目的限量或者报告限,单位mg/kg;U rel,限量浓度附近的相对扩展不确定度;F,限量或者报告限的安全系数;m tot,混合测试样品的总质量,单位g;V,定容溶液的体积,单位mL;IDL,仪器检测限,单位mg/L;M,限量或者报告限对应的待测项目数;如果限量只是一个化学检测项目,则U rel,限量浓度附近的相对扩展不确定度根据以下公式计算:U rel=u rel×k式中,u rel,限量浓度附近的相对标准不确定度;k,包含因子,取置信度为95%,k=2;u rel,1,方法再现性的相对标准不确定度,即再现性数据的标准偏差;u rel,2,方法回收率的相对标准不确定度;u rel,3,标准曲线的相对标准不确定度,即再现性数据的标准偏差;如果限量是多个化学检测项目之和,则U rel,限量浓度附近的相对扩展不确定度根据以下公式计算:U rel=u÷L×k式中,u,限量浓度附近的标准不确定度,单位mg/L;L,待测项目的限量或者报告限,单位mg/kg;k,包含因子,取置信度为95%,k=2;u 1,待测项目1的标准不确定度,单位mg/kg,u 2,待测项目2的标准不确定度,单位mg/kg,u 3,待测项目3的标准不确定度,单位mg/kg;最佳混合数确定模块,用于根据待测项目的阳性率或者不合格率,查询节省工作量效率表,在2~K max之间选取节省工作量最大的混合数作为最合适的混合数,所述节省工作量效率表按照下式建立而成:式中,S表示节省的工作量,q表示阳性率或者不合格率,K表示混合数;混样测试模块,用于按照最合适的混合数对待测样品进行分组,并进行混样测试。
- 根据权利要求5所述的消费品化学检测项目的混样定量测试装置,其特征在于,混样测试模块在混样测试后,计算单个测试样本的待测物质的最大含量,若超出修正后的限量或者报告限,则将混合样 本拆分单独再测。
- 根据权利要求5或6所述的消费品化学检测项目的混样定量测试装置,其特征在于,待测项目的阳性率/不合格率低于20%。
- 根据权利要求5或6所述的消费品化学检测项目的混样定量测试装置,其特征在于,限量/报告限的安全系数F的取值范围为取值范围为0%-100%,和实验室各自的测试水平有关。
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