2023年6月24日发(作者：)

Unit 12

What is Analytical Chemistry

Perhaps the most function definition of analytical chemistry is that it is "the qualitative and quantitative characterization of

matter ".也许对分析化学最实用的定义是：对物质进行定性和定量的表征。The word "characterization "is used in a very

broad sense .描述这个词被广泛的使用。It may mean the identification of the chemical compounds or elements present in a

sample to answer questions such as "Is there any vitamin E in this shampoo as indicated on the label ?"or "Is this white tablet an

aspirin tablet ?"or"Is this piece of metal iron or nickel ?"它可能意味着在回答诸如“在洗发香波中是否如标签所示有维生素E”“这是一个白色阿司匹林片？”或“这块金属是铁或镍”等问题时，对样本中的化合物或元素进行鉴定。This type of

characterization ,to tell us what is present is called qualitative analysis .这种类型的表征，要告诉我们什么是目前被称为的定性分析。Qualitative analysis is the identification of one or more chemical species present in a material .定性分析是鉴定一个或多个化学物质存在于一个材料中。Characterization may also mean the determination of how much of a particular

compound or element is present in a sample ,to answer questions such as "How much acetylsalicylic acid is in this aspirin

tablet ?"or "How much nickel is in this steel ?"描述也可能意味着测定有多少种化合物或元素存在于一个样品中，回答“水杨酸在这个阿司匹林片中含量多少”或“这块钢中含有多少镍”等这些问题。This determination of how much of a species

is present in a sample is called quantitative analysis .一种物质在一个样品中含量多少的这种测定被称为定量分析。Quantitative analysis is the determination of the exact amount of a chemical species present in a sample .定量分析是测定某种化学物质在某个样品中的确切数量。The chemical species may be an element ,compound ,or ion .化学物质可能是某些元素、化合物或离子。The compound may be organic or inorganic .该药物可能有机和无机两种。Characterization can refer to

the entire sample (bulk analysis ），such as the elemental composition of a piece of steel ,or to the surface of a sample (surface

analysis ),such as the identification of the composition and thickness of the oxide layer that forms on the surface of most metals

exposed to air and water .特性描述可能涉及到全分析，如构成一块钢的元素，或者表面分析，像鉴定绝大多数暴露在空气和水中的金属表面形成的氧化层的成分和厚度。The characterization of a material may go beyond chemical analysis to

include structural determination of materials ,the measurement of physical properties of a material ,and the measurement of

physical chemistry parameters like reaction kinetics .一个材料的特性描述可能超越化学分析所包括结构材料的确定，某个材料的物理性质的测量，以及物理化学参数的测量例如反应动力学。Examples of such measurements are the degree to

which a polymer is crystalline as opposed to amorphous ,the temperature at which a material loses its water of hydration ,how

long it takes for antacid "Brand A"to neutralize stomach acid ,and how fast a pesticide degrades in sunlight .这些测量的实例有：聚合物的结晶度（与非晶态相比）？物质失去结晶水的温度？“A牌”抗酸剂中和胃酸所需的时间？农药在阳光下的降解速度？These diverse applications make analytical chemistry one of the broadest in scope of all scientific disciplines .这些不同的应用使分析化学成为广泛的学科之一在所有的科学学科中。Analytical chemistry is critical to our understanding

of biochemistry ,分析化学对于我们了解生物化学是至关重要的。medicinal chemistry ,geochemistry ,environmental

science ,atmospheric chemistry ,the behavior of materials such as polymers ,metal alloys ,and ceramics ,and many other

scientific disciplines .药物化学、地球化学、环境科学、大气化学，材料学中的反应像聚合物、金属合金和陶瓷技术以及许多其他科学领域。

For many years ,analytical chemistry relied on chemical reactions to identify and determine the components present in a

sample. 多年来，分析化学依赖化学反应，以确定出现在一个样本中的组分。These type of classical methods ,often called

"wet chemical methods ",usually required that a part of the sample be taken ,dissolved in a suitable solvent if necessary and the

desired reaction carried out .这些类型的经典方法，经常被称为“湿化学方法”，通常需要采集一部分样品，溶解在适当的溶剂，如有必要，进行所需的反应。The most important analytical fields based on this approach were volumetric and

gravimetric analysis .这种重要的分析方法基于体积和重量的分析。Acid-base titrations ,oxidation -reduction titrations ,and

gravimetric determinations, such as the determination of silver by precipitation as silver chloride are all examples of wet

chemical analyses. 氯化银沉淀法测定银等都是湿化学分析示例。These types of analyses require a high degree of skill and

attention to detail on the part of the analyst if accurate and precise results are to be obtained .要想获得准确、精密的结果，这类分析需要高度技巧以及分析工作者对技巧细节的高度关注。They are also time consuming and the demands of today's

high-throughput pharmaceutical development labs and industrial quality control labs often do not permit the use of such

time-consuming methods for routine analysis .他们也耗费时间以及今天的高吞吐量制药开发实验室和工业质量控制实验室的往往不允许使用这种耗时的用于常规分析的方法的要求。In addition ,it may be necessary to analyze samples without

destroying them .此外，可能有必要分析样本而不破坏它们。Examples include evaluation of valuable artwork to determine if

a painting is really by a famous "Old Master" or is a modern forgery, as well as in forensic analysis, where the evidence may

need to be preserved.例子包括评估有价值的艺术品确定一幅画是被否来自一位著名的大师，或者是一个现在的仿品，同样在需要保存证据的法医分析那里。For these type of analyses,nondestructive analysis analysis methods are needed,and wet

chemical analysis will not do the job. 对于这些类型的分析、无损分析分析方法是必要的,和湿化学分析将不起作用。Wet

chemical analysis is still used in specialized areas of analysis, but many of the volumetric methods have been transferred to

automated instruments,Classical analysis and instrumental analysis are similar in many respects, such as in the need for proper

sampling, sample preparation, assessment of accuracy and precision, and proper record keeping.湿化学分析仍然使用在专业的分析领域，但许多容量法已移交给自动化工具，传统的分析和仪器分析在许多方面是相似的，比如在需要适当的采样、样品制备、评价的准确度和精密度,以及正确的数据保存。

Most analyses today are carries out with specially designed electronic instruments controlled by computers. 如今大多数分析是由电脑控制的特制电子仪器进行。These instruments make use of the interaction of electromagnetic radiation and

matter,or of some physical property of matter,to characterize the sample being analyzed.为了测定被分析样本这些工具使用电磁波与物质相互作用，或物质的物理性质。Often these instruments have automated sample introduction,automated date

processing,and even automated sample preparation. 通常,这些仪器自动进样,自动数据处理、甚至是自动制备样品。To

understand how the instrumentation operates and what information it can provide requires knowledge of

chemistry ,physics,mathematics, and engineering.为了解如何仪器操作和哪些信息仪器可以提供就需要化学、物理、数学和工程学知识。The fundamental of common analytical instruments and how measurements are performed with these

instruments are the subjects of the following chapters on specific instrumental techniques. 常见的基础分析仪器和这些仪器分析出的测量值是接下来特定仪器技术章节的主题。The analytical chemist must not only konw and understand analytical

chemistry and instrumentation ,but must also to serve as a problem solver to colleagues in other scientific ares. 分析化学家不但必须知道和了解化学分析和仪器,而且必须作为一个问题解决者为其他科学领域的同行。This means that the analytical

chemist may need to understand materials science,metallurgy,biology,pharmacology,agricultural science,food

science,geology,and other fields.这意味着分析化学家可能需要理解材料科学、冶金、生物学、药理学、农业科学、食品科学、地质学、和其他领域。The field of analytical chemist is advancing rapidly.分析化学领域的迅猛发展。To keep up with

the advance,the analytical chemist must understand the fundamentals of common analytical techniques,their capabilities,and

their shortcomings.为了跟上发展，分析化学家必须了解基础的常见的分析技术,它们的性能,它们的缺点。The analytical

chemist must understand the problem to be solved,select the appropriate technique or techniques to use,design the analytical

experiment to provide relevant date,and ensure that the date obtained are valid.分析化学家必须了解需要解决的问题，选择恰当的分离技术和联用技术，设计分析实验以提供相关数据，并保证数据有效。Merely providing data to other scientists is not

enough;the results, together with the accuuracy and precision of the data,to scientists who will use the data.仅仅提供数据给其它科学家是不够的，分析化学家必须能够解读数据，并将结果的意义和数据的精度（可靠性），传达给使用这些数据的科学家们。in addition to understanding the scientific problem, the modern analytical chemist often must also consider factors

such as time limitations and cost limitations in providing an analysis. 除了了解科学方面的问题，现代分析化学家往往必须也要考虑例如时间限制和成本提供分析限制的因素。Whether one is working for a government regulatory agency, a

hospital,a private company,or a university,analytical data must be legally defensible.无论是否为政府监管机构、医院、私营公司或大学,工作分析数据必须在法律上站得住脚。It must be of known,documented quality.它必须是已知的，有案可稽的质量。Record keeping, especially computer record keeping,assessing accuracy and precision,statistical data ,documenting,and

ensuring that the data meet the applicable technical standards aspects of the job of modern analytical chemists.记录保存，尤其是计算机数据保存，评估精度和精密、统计数据、记录并确保数据符合合适的现代分析化学家的工作技术方面标准。

Many analytical results are expressed as the concentration of the measured substance in a certian amount of sample. 很多分析结果来表示一定数量的样品中测量到的物质的浓度。The measured substance is called the analyte. 被测量的物质被称为分析物。Commonly used concentration units include molarity,weight percent,and units for trace levels of substances.常用的浓度单位包括摩尔浓度、质量分数和微量物质等级单位。One part per million by weight is one microgram of analyte in a gram

of sample,that is,1×10-6g analyte/g sample.在一克样品中百万分之一的重量就是一个微克分析，也就是样品的1×10-6微克/克。For many elements,the technique knowm as inductively coupled plasma mass spectromery can detect pares per trillion of

the element, that is, picograms of element per gram of sample.对多组分体系，电感耦合等离子体质谱技术，可以检测出含量为万亿份之一的成分，即没课样品中含量为皮克的成分。To give you a felling for these quantities,a million seconds is 12

days.让你感觉这些数量，100 万秒为 12 天。One part per billion in units of seconds would be is in 32 years,and one part per

trillion is one second in 32000 years.十亿分之一秒为单位将在32年后,一万亿分之一是在3200年后。Today,lawmakers set

environmental levels of allowed chemicals in air and water based on measurements of compounds and elements at part per

trillion levels because instrumental methods can detect part per trillion levels of analytes.今天，立法者基于化合物的测量值和万亿分之水平的元素因为仪器方法可以检测万亿元水平分析物来设置水和空气中允许化学品的环境水平。It is the analytical chemist who is responsible for generating the data that these lawmakers rely on.立法者依赖着分析化学家负责生成的数据。