Retained sample

Removal of Processed Materials Materials such as product, off-spec material inventory, retained samples, and process... 

Clean up includes identifying, gathering, storing (when appropriate), and classifying materials associated with a specific toll. Decisions can then be made as to which raw materials, intermediates, and product will be shipped back to the client or kept by the toller. Some off-spec product, retained samples, or unused intermediates may be considered waste materials at this point. Equipment clean up can be extremely important to preserving quality and process safety integrity prior to the next production run of a new product. 

As described above, resolution can be improved by variations in plate number, selectivity or capacity factor. However, when considering the separation of a mixture which contains several components of different retention rates, the adjustment of the capacity factors has a limited influence on resolution. The retention times for the last eluted peaks can be excessive, and in some cases strongly retained sample components would not be eluted at all. 

Quality control - responsibility, review test results and production records, retain samples... 

A manufacturer usually stores samples of both raw materials and finished products for extended periods of time. He may even be required to do so by law. Sample storage may present hazards often overlooked. A single bottle of perfume, for instance, is too small to be considered a fire hazard, even though the material is quite flammable. Hundreds of these bottles, however, stored away as retain samples by a cosmetics manufacturer will become a fire hazard. 

Poor Record Keeping. Unfortunately, many small industrial laboratories have inadequate records. This can have unpleasant consequences. In one case, the manufacturer of an alcohol solution was challenged by a customer about meeting specifications set forth in the contract. For his defense, he had not retained samples that could be traced to the disputed deliveries, and his only written information consisted of scribbled notes on loose sheets of paper from his desk drawer. He lost the contract. An independent investigation indicated that he had probably done his job right, but he had no way to prove it. 

The test substance may be acquired in a number of ways. One common method is to purchase the product from a chemical dealer. This method of acquiring the test substance for a worker exposure or re-entry study allows one to proceed rapidly with the execution of the field portion of the study without the serious delays encountered while waiting for a test substance to be manufactured, assayed, and shipped to the site. Although having a test substance formulation which has been assayed under GLP standards and for which a certificate of analysis has been shipped to the test site is desirable, there are several instances when this is not practical. For example, one may encounter a worker exposure study where the pesticide to be evaluated is sold only in mini-bulk or even large bulk quantities holding as much as 2000 gal. In this case, duplicate 5-10-g or 5-10-mL retainer samples should be taken from the bulk or mini-bulk tanks for assay after the worker exposure study is in progress. 

Problem definition Ever since a production plant started using a new supplier of a carbon decolorizing agent, consistently acceptable polymer has not been obtained. The plant s technical director recently read an article about the power of new mass spectrometric techniques, so she sends you an urgent e-mail and sends a sample of the offending carbon and a retained sample of the previous supply. The technical director asks you to find the impurity in the new, ineffective decolorizing carbon. 

Raw material quality control records Retained sample documentation Quality control (qc) lab logs Emergency responder logs... 

If retained sample material from an interlaboratory test is available and it is stable after the test is finished, this also can be used as an in-house reference material. 

It may be necessary to retain samples of intermediate products in suiScient quantities, and under appropriate storage conditions, to allow the repetition or confirmation of a batch control. 

Size exclusion chromatography (SEC) separates molecules based on size in a short analysis time. Unlike other chromatographic techniques, SEC does not retain sample species in the column, the analysis time is fixed, and everything loaded onto the column elutes within a fixed time frame. The application of SEC is limited only to the solubility of the sample in a solvent. Since tetrahydrofuran (THE) is a good solvent for coal liquids, the separation of coal liquids by SEC can be easily achieved. 

This will be the so-fcalled "retainer sample and it should be ca 20 g (dry wt). Repeat the above procedures with each primary sample. Collect the remaining portions of each primary sample into one container, blend them, spread on a flat surface and divide as above into squares. Remove from each square an equal portion to make (after blending) a composite (of several primary samples), weighing ca 50 g (dry wt). Keep the bottle with this sample, as well as with the 20 g sample, tightly closed. Label each bottle accordingly Preparation of a dry sample... 

Adsorbent. An active granular solid used as the column packing in gas-solid chromatography which retains sample components by adsorptive forces. 

Test Chemical. Once the test chemical and its formulation have been defined, the needed amount is prepared and packaged, the batch is analyzed, and portions are shipped to the test locations. Retained samples are correctly stored. If the storage stability of this formulation has not been determined, some of the retained samples are used to determine its storage stability under typical storage conditions. In this and subsequent data gathering steps the investigators collecting the data need to be identified. 

The use of retain samples to routinely examine a statistically sound number of units is a valuable investigative tool. If the retain samples do not reveal any degradation, but other quality markers, such as consumer complaints, manufacturing deviations, and QC profiles, indicate shifts in quality, a problem with the retain sampling method should be considered. On the other hand, if the retain samples... 

Retain sample summary will consist of the following ... 

A summary of the annual visual inspection of retain samples based on a statistically sound sampling plan. 

Application of Prep-HPLC to PGS Analysis. Reverse phase liquid chromatography has proven to be well suited for cleanup of plant extracts by prep-HPLC (4, 46, 47, 48). When the mobile phase is initially an aqueous buffer at pH 2.8, all but the highly charged (e.g., zeatin ribotide with 5 AMP used as a representative compound for zeatin ribotide) plant hormones are retained at the head of the column (Fig. 1). Since the PGS are retained, samples can be injected onto the column in a dilute form. In-... 

For effective liquid chromatographic separations, a column must have the capacity to retain samples and the ability to separate sample components, efficiently. The capacity factor, k R, of a column is a direct measure of the strength of the interaction of the sample with the packing material and is defined by the expression... 

Tyler mesh size Sieve opening, (im Weight of retained sample, g Percent retained (by calculation) Cumulative percent passing (by calculation)... 

Random sample Representative sample Retained sample Selective sample... 

A retained sample is a sample taken for future reference purposes, e.g. for use in analysis where the result is the subject of a dispute. 

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