tailieunhanh - Modern Analytical Cheymistry - Chapter 15

Quality Assurance Trong chương 1 chúng tôi ghi nhận rằng mỗi lĩnh vực hóa học mang lại một cái nhìn độc đáo với nguyên tắc rộng lớn hơn của hóa học. Hóa phân tích, quan điểm này được xác định là một cách tiếp cận để giải quyết vấn đề, được trình bày như là một quá trình năm bước: (1) Xác định và xác định vấn đề, (2) Thiết kế quy trình thử nghiệm, (3) Tiến hành một thử nghiệm và thu thập dữ liệu (4) Phân tích các dữ liệu thử nghiệm, và (5) đề nghị một giải. | Chapter ùa 15 uality Assurance I n Chapter I we noted that each field of chemistry brings a unique perspective to the broader discipline of chemistry. For analytical chemistry this perspective was identified as an approach to solving problems which was presented as a five-step process 1 Identify and define the problem 2 Design the experimental procedure 3 Conduct an experiment and gather data 4 Analyze the experimental data and 5 Propose a solution to the problem. The analytical approach as presented thus far appears to be a straightforward process of moving from problem-to-solution. Unfortunately or perhaps fortunately for those who consider themselves to be analytical chemists an analysis is seldom routine. Even a well-established procedure carefully followed can yield poor data of little use. An important feature of the analytical approach which we have neglected thus far is the presence of a feedback loop involving steps 2 3 and 4. As a result the outcome of one step may lead to a reevaluation of the other two steps. For example after standardizing a spectrophotometric method for the analysis of iron we may find that its sensitivity does not meet the original design criteria. Considering this information we might choose to select a different method to change the original design criteria or to improve the sensitivity. The feedback loop in the analytical approach is maintained by a quality assurance program Figure whose objective is to control systematic and random sources of The underlying assumption of a quality assurance program is that results obtained when an analytical system is in statistical control are free of bias and are characterized by well-defined confidence intervals. When used properly a quality assurance program identifies the practices necessary to bring a system into statistical control allows us to determine if the system remains in statistical control and suggests a course of corrective action when the system has fallen out of