Quality control chemist

Impure substances have melting points that are very dependent upon the amount of impurity present. For a few substances this is quantified as the molal freezing point depression constant. The result is that melting points can be a very useful indicator of purification efforts. As long as each purification step in a process results in a higher melting point, the substance has been made more pure. This same concept allows the quality control chemist to have a very sensitive method for detecting impurities that is lower than anticipated. 

Quality control chemist These chemists analyze raw materials, intermediate products, and final products for purity to make sure that they fall within specifications. They may also offer technical support for the customer or analyze returned products. Many of these chemists often solve problems when they occur within the manufacturing process. 

Formulator Glass technologist Industrial chemist Mix chemist Oil expert Paint formulator Pesticide chemist Powder expert Quality-control chemist Rubber chemist... 

Finally, the textbook concludes with two chapters discussing the design and maintenance of analytical methods, two topics of importance to analytical chemists. Chapter 14 considers the development of an analytical method, including its optimization, verification, and validation. Quality control and quality assessment are discussed in Chapter 15. 

All processes in the production of PSS columns are controlled by an efficient multistep quality control (QC) system (25). This QC system requires complete tests and documentation for all materials used in all production stages. All QC work has to be performed by specially trained and highly skilled polymer chemists. 

The synthesis of the packing materials is done by experienced polymer chemists using standardized equipment and procedures. PSS takes special care in cleaning the sorbents after polymerization to achieve constant quality and surface chemistry characteristics. Each production step is checked separately for quality control conformity. 

In a modern industrialised society the analytical chemist has a very important role to play. Thus most manufacturing industries rely upon both qualitative and quantitative chemical analysis to ensure that the raw materials used meet certain specifications, and also to check the quality of the final product. The examination of raw materials is carried out to ensure that there are no unusual substances present which might be deleterious to the manufacturing process or appear as a harmful impurity in the final product. Further, since the value of the raw material may be governed by the amount of the required ingredient which it contains, a quantitative analysis is performed to establish the proportion of the essential component this procedure is often referred to as assaying. The final manufactured product is subject to quality control to ensure that its essential components are present within a pre-determined range of composition, whilst impurities do not exceed certain specified limits. The semiconductor industry is an example of an industry whose very existence is dependent upon very accurate determination of substances present in extremely minute quantities. 

A successful program of quality control also involves maintenance of sanitary conditions and production of products free from adulteration, contamination, and filth. Methods given by the Association of Official Agricultural Chemists (1) should be applied to the finished product to ensure against seizure and prosecution by federal and state food and drug authorities. In many instances such methods of analysis are not adaptable to production-line control and less accurate but more rapid methods must be substituted. With such procedures, more severe tolerances must be used to provide a sufficient margin of safety. 

Much valuable research has been devoted to developing the basic principles for the production of frozen fruits and vegetables of high and uniform quality. If this knowledge could be applied to its fullest extent, there would be little need for concern over the quality of such foods. Before this can be done, those responsible for quality control must be provided with suitable standards of quality and condition, and objective methods of analysis which will clearly indicate conformance or nonconformance to the standards. Responsibility for this resides with the research food technologist or chemist. It constitutes a rich field for profitable and practical research. 

The pH scale was introduced by the Danish chemist Soren Sorensen in 1909 in the course of his work on quality control in the brewing of beer and is now used throughout science, medicine, agriculture, and engineering. 

A manufacturing company approached the cost of quality control in a realistic manner. Before a quotation was made for a new product, the control chemist submitted an estimate of the time required for running the necessary tests. An hourly charge was established for laboratory operation, and the cost of quality control could thus be established. The sales department did not like the arrangement because the cost was very much the same whether they sold 200 or 2000 gallons of a product. 

A few years ago, a customer filed suit against a nationally known manufacturer of automotive brake fluid for supplying faulty merchandise. When the company s control chemist went before the jury with his detailed quality control records, he was able to prove that the allegedly faulty batch made two years earlier met all the requirements established for this product. The plaintiff lost his case. 

Internal quality control (IQC) is one of a number of concerted measures that analytical chemists can take to ensure that the data produced in the laboratory are of known quality and uncertainty. In practice this is determined by comparing the results achieved in the laboratory at a given time with a standard. IQC therefore comprises the routine practical procedures that enable the analyst to accept a result or group of results or reject the results and repeat the analysis. IQC is undertaken by the inclusion of particular reference materials, control materials , into the analytical sequence and by duplicate analysis. 

Up to this point we have characterised our materials as continua and defined the material parameters. This may be all that is required for engineering purposes or quality control needs. Whenever a modification of the behaviour is sought, a deeper understanding of the origins of the response is required. It was pointed out in Chapter 1 that the rheology is controlled by the atomic or molecular interactions in the system, and this brings the subject properly into focus for the chemist. 

We must first appreciate that electrochemical simulations are probably more useful to the research chemist than the quality control analyst an analyst involved in quality control is likely to repeat a large number of measurements on a known chemical system, each time asking how much , rather than needing to ponder complicated mechanistic questions. 

The objective of QualAID ( ) is to provide advice on how much and what type of quality assiarance (QA) and quality control (QC) is needed for various types of environmental analyses. The purpose of this system is to provide consistently good advice to chemists whose primary field of expertise is other than QA/QC. 

Traditionally, the education that chemists and chemistry laboratory technicians receive in colleges and universities does not prepare them adequately for some important aspects of the real world of work in their chosen field. Today s industrial laboratory analyst is deeply involved with such job issues as quality control, quality assurance, ISO 9000, standard operating procedures, calibration, standard reference materials, statistical control, control charts, proficiency testing, validation, system suitability, chain of custody, good laboratory practices, protocol, and audits. Yet, most of these terms are foreign to the college graduate and the new employee. 

IUPAC, ISO, and AOAC International International Union of Pure and Applied Chemistry, International Organisation for Standardization, Association of Official Chemists Method validation, Standardization, internal quality control, proficiency testing, accreditation 4,8, 62-71... 

Terpene chemists use mainly gas chromatography in dealing with terpene mixtures in research and development as well as in quality control. Capillary gas chromatography with stable bonded-phase columns, the primary analytical method, is also being used more frequendy in the 1990s in product quality control because its greater resolution is helpful in producing consistent products. 

Acceptance criteria for precision depend very much on the type of analysis. For pharmaceutical quality control, precision of better than 1 % RSD is easily attained, while for biological samples the precision is more like 16% at the detection limit and 10% at higher concentration levels. For environmental and food samples, the precision is very much dependent on the sample matrix, the level of the analyte, and on the analytical method, being in the range of 2% to more than 20% RSD. Acceptable precision values as a function of the analyte concentration have been suggested (11) by the Association of Official Analytical Chemists (AOAC) peer-verified methods program (Table 25.1). 

Analytical chemists are by nature innovators and seekers of improvement. In the development area these qualities are invaluable in optimising method performance. Alas far too often, this desire for continuous improvement spills over into the interpretation of methods for quality control. Here we require consistency of application and rigorous control of processes and procedures. These aspects are anathema for many practitioners of the art of chemical analysis . 

AMERICAN OIL CHEMISTS SOCIETY (AOCS). Founded in 1909. It has over 5000 members. These members are chemists, biochemists, chemical engineers, research directors, plant personnel, and persons concerned with animal, marine, and legulai oils and fats and their extraction, refining, safety, packaging, quality control, and use. The address is 508 S. 6th St.. Champaign, IL 61820. http //www.aocs.org/... 

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