standard operating procedures

ideal operating procedures standard operating procedures stock(a) Operating Procedures A General OverviewAimThis document is non meant to be all encompassing but is designed to give readers an overview as to what should be in a SOP and what a SOP might look like.Background It was common in the past for to be photocopied from a book and notes/scribbles to be added to a system to change it to a Laboratorys specific affects. This resulted in psychoanalysts use different versions of the same method and obtaining different results. It also hindered the communication of improvements that an individual analyst had made to a method, as it was not known how many copies of a method existed and whether they had all been updated to include the improved method.A way to improve this chaos is to ensure that all methods and procedures shall be documented to the extent necessary to ensure proper implementation and consistency of application. Hence the introduction of the concept of SOPs S tandard Operating Procedures.It is some quantify not practical for laboratories to use an SOP which is fully documented specifying each type and individual tryout procedure. For example, analysis of soil samples for polyaromatic hydrocarbons. It is simpler to write an SOP on the prep of soil extracts for analysis by gas chromatography and another SOP of a more general nature regarding the analysis of extracts by gas chromatography.Information require for all SOPsAll SOPs should contain the following informationAuthorised by (Someone in the organization needs to approve the SOP to begin with it can be employ)Copy soma (A record of the number of copies of an SOP needs to be kept each individual copy has its own number identifies if on that point are any illicit versions in use ) Page x of y (e.g. Page 1 of 6 appears at the bottom of each page identifies if there are pages missing from a method) Other information may include when the method should be reviewed, individual re ference numbers for when an organisation has many SOPs, Issue numbers to identify new versions of a method from old versions of a method which have been withdrawn.To help explain some of the wrong below, parts of an SOP involving the analysis of nitrite in water have been reproduced in boxes like this. THESE WILL ONLY BE EXAMPLES AND ARE NOT COMPREHENSIVE.Title intent of A analyte(s)or measurand(s), in C matrix using D principleDetermination of nitrite in water by UV/Visible spectrophotometryScope Enables a user to see quickly whether the method is appropriate for a desired application (see also the Annex- method validation and measurement uncertainty).the analyte (measurand) which can be determined by the method, the sample matrix from which the analyte (measurand) may be determined, the technique used in the method, the minimum sample size, known interferences which prevent or limit the on the job(p) of the method, the concentration range of the method. The amount of nitrite in an aqueous sample can be determined. The detection limit is 0.01 mg dm-3 for a 30 cm3 sample. There is a maximum limit of 0.25 mg dm-3 for a 30 cm3 sample. Dilutions can be carried out on the sample to extend the range of analysis. Type of sample bleak and potable waters and sewage effluents. Samples that are extremely coloured or turbid can cause interference*. * If the alkalinity of the sample is high, such that a pH value of 1.9 0.1 is not attained after the addition of the sulphanilamide reagent (.) then the formation of the azo- spot is affected. *It may be more appropriate to have a separate parting for interferences.Warning Safety Precautionshandling the samples handling or preparing solvents, reagents, standards, or other materials operation of equipment requirements for additional handling environments, e.g. fume cupboards N-1-naphthylethylenediamine dihydrochloride should be regarded as a special hazard. Skin contact with the solid and solution containing it should be avoided. Disposable gloves should be worn when handling effluent or sewage samples. Normal precautions to avoid pare down contact and/or ingestion should be interpreted in the handling of all reagents. DefinitionsDefine any unusual terms, use ISO definitions wherever possible. Quote sources. embarrass chemical formulae/structures if appropriate.PrincipleOutline the principle by which the analytical technique operates. This class should be written so that a summary of how the method plant can be seen quickly.The method is based on the diazotisation of sulphanilamide by nitrite in the presence of phosphoric irate, at pH 1.9, and the subsequent formation of an azo dye with N-1-naphthylethylenediamine. The absorbance of this dye is measured at 540 nm and is related to the nitrite concentration by means of a normalization curve.Re exertionsWhere appropriate to clarifying the working of the method or calculations, include details of any relevant chemical reactions. Th is may be relevant, e.g. where derivatisation is involved, titrimetry etc..Reagents Materials List all of the reagents materials, blanks, QC samples and standards and certified reference materials required for the analytical process, identified by letter or number. Listdetails of any associated hazards including instructions for disposal, appropriate grade of reagent/chemical, specialist suppliers for rare chemicals, need for calibration and QC materials, details of preparation, including need to deck out in advance, containment and storage requirements, shelf life of raw material and aimd reagent, required concentration, noting whether w/v, w/w or v/v, labelling requirements. a. All reagents should be of at least analytical reagent grade. b. Water In all cases demineralised water shall be used. c. Nitrite Stock forStandard Solution, 1000 mg dm-3 NO2 moot out 1. five hundred0 g 0.0050 g of sodium nitrite, (previously dried overnight at 105 5 C and stored in a desiccator des iccant silica gel) and transfer quantitativelyto a 1 dm3 order A volumetric flask containing approximately 500 cm3 of water (b). Make up to the mark with water (b) and stopper. Shake until all the solid dissolves. Transfer to an fitly labelled glass store and store in the refrigerator. The solution is stable for 1 month. d. Orthophophosphoric acidulent 85% w/w e. 2 mg dm-3 Nitrite Standard Using a Grade A glass pipette, pipette 2 cm3 of 1000 mg dm-3 stock nitrite solution (c) into a 1 dm3 Grade A volumetric flask and make up to volume with water (b). Stopper and shake to mix. Transfer to an fitly labelled glass bottle, stopper and store in a refrigerator. The solution is stable for 1 week. f. Nitrite Stock for Quality Control Solution 1000 mg dm3 NO2 Ideally the sodium nitrite should be obtained from a different source to that used for the standard. Weigh out 1.5000 g 0.0050 g of sodium nitrite g. Sulphanilamide Reagent Using a 100 cm3 measuring cylinder, add 50 cm3 of 85% ortho phosphoric acid (d) to a 500 cm3 beaker containing 250 cm3 of water (b). Weigh out 20.00 g 0.25 g of sulphanilamide and quantitatively transfer to the beaker. Stir with a glass rod until the solid dissolves. Weigh out 1.00 g 0.10 g of N- 1-naphthylethylenediamine dihydrochloride and quantitatively transfer to the beaker. Stir with a glass rod until the solid dissolves. Quantitatively transfer the solution to a 500 cm3 volumetric flask and make up to volume with water (b). Stopper the flask and shake to mix. Transfer to an appropriately labelled amber glass bottle and store in the refrigerator. The solution is stable for 1 month. NB Immediately before use, this solution should be brought to room temperature. Points to note from exampleEach reagent is unequivocally identified so as to avoid confusion. Weigh 20.00 g Indicates that a balance capable of weighing to 2 decimal places is required. 20.00 g 0.25 g Tells the analyst that he needs to be between 19.75 g and 20.25 g. Using a 50 cm3 measuring cylinder Indicates accuracy required for this procedure. Quantitatively transfer Indicates that you need to transfer all the solid with washings to the beaker. Appropriately labelled This might include Name of reagent, Concentration of reagent, Date reagent made, Expiry date of reagent, Name of analyst who prepared the reagent Most com drifter systems can be used to produce sheets of labels that suits an individuals and/or organisations needs. Apparatus Equipment attract in sufficient detail the individual pieces of equipment and how they are attached to enable unambiguous set-up. For glassware include grade where applicable. Include environmental requirements (fume cupboards etc.).a. A Manufacturers name/model number UV/Visible spectrophotometer with 10 mm glass cells is used. b. The instrument should be switched on for a minimum of half an hour before the analysis. Set the wavelength to 540 nm. Details of operation of the instrument are given up in the ins truction manual for the instrument. It may be appropriate to reproduce the relevant parts of the instruction manual in the SOP i.e. how to set up and use the spectrophotometer. This will depend on how easy it is to get access to the manual.Sampling Sample PreparationInclude sufficient detail to describe how the test portion is obtained from the sample as received by the laboratory. All information on the precautions to be taken to minimise the risk of contamination of the samples needs to be included. Include information regarding the storage, conditioning and disposal of samples. Many laboratories will write a separate document about the receipt, labelling, storage and disposal of samples to save having to pair this information on individual SOPs.Environmental ControlList any special environmental conditions and cross reference to safety section, e.g. temperature manage.CalibrationIdentify the decisive parts of the analytical process. These will have to be controlled by careful operation and calibration. Cross reference to the relevant sections above. It may be easier to incorporate this section with the analytical procedure section.Include calibration of equipment what needs to be calibrated, how, with what, and how often?It is normally easier to write separate documents to cover the calibration of balances, automatic pipettes, thermometers, refrigerators, freezers and spectrophotometers to save having to put all this information into each SOP.Quality ControlExplain the quality control procedures, frequency of quality control checks during batch analysis, pass/fail criteria, action to take in the event of a failure. It may be appropriate to incorporate this section in the analytical procedure section.Analytical ProcedureDescribe the analytical procedure, cross referencing previous sections as appropriate including reagents (with the appropriate identifier), apparatus and instrumentation. Indicate at which point in the analytical procedure the quality c ontrol, and calibration procedures should be performed. Use a 50 cm3 measuring cylinder to transfer 30 cm3 of either sample, blank water (.), standard or QC solution to appropriately labelled test tubes. For each batch of samples, one sample should be recurd. For effluent samples or samples which are apparent to contain real levels of nitrite, using a glass pipette, pipette 3 cm3 of sample into a 50 cm3 measuring cylinder containing 27 cm3 of water. If any of the samples are highly coloured or turbid, prepare a sample blank by transferring 30 cm3 of the appropriate sample to an appropriately labelled test tube and add 1 cm3 of 10% orthophosphoric acid (). Treat as an ordinary sample except that water () is added instead of sulphanilamide reagent (.). Using an automatic pipette add 0.75 cm3 of sulphanilamide solution (.) to each tube. Mix without delay by swirling, and allow to stand for at least 30 proceedings but no longer than two hours. Measure the absorbance of the bla nk (.) and the standard (.) enroll the relevant information in the spectrophotometeric logbook* and check that the absorbance of the standard is within the specified range detailed in the log book. If the absorbance falls outside this range, consult a senior officer before proceeding further. Determine the nitrite concentration of the QC solution () and the samples. Plot the concentration recorded for the QC solution (.) on the appropriate quality control chart , together with the date and your initials. If the point does not fall within the set limits, the senior officer in charge must be informed. * each samples that give concentrations great than 0.25 mg dm3, must be discarded and the analysis repeated using a diluted sample. Points to noteIf any of the samples are highly coloured or turbid. Guidelines on how to handle difficult samplesUsing an automatic pipette Defines the accuracy that the reagent has to be measured toFor effluent samples or samples which are likely to con tain significant levels of nitrite Guidelines on how to handle samples whose nitrite concentration will probably exceed the range for the method.Leave the colour to develop for 30 to 60 minutes This implies that the colour development time is important. You will have needed to carry out some checks to show that these times are satisfactory.Any samples that give concentrations greater than 0.25 mg dm-3, must be discarded and the analysis repeated using a diluted sample Only concentrations in the working range of the method should be reported.Consult a senior officer There will always be times when the analyst encounters problems or unknown situations the analyst should be encouraged to seek help from an experienced member of staff.Log BooksInformation to be recorded in the log book associated with spectrophotometer might include serial publication number, service dates, calibration checks (e.g. wavelength), repairs (e.g. new lamp).On a daily basis information recorded might includ e date, name of analyst, analysis (e.g. nitrite), wavelength used, absorbance of blank, concentration and absorbance of standard.At the front of the log book should be sufficient information regarding the nitrite analysis for the operator to determine if there is a problem, e.g. nitrite analysis, wavelength 540 nm, acceptable absorbances of (a) blank 0.000 0.005, (b) 0.25 mg dm-3 nitrite standard 0.250 0.010. Repeatability measurement on the same solution 0.003.Log Books points to noteUse of a standard, quality control and blank and a replicate sample and put down the information in a log book means that you can demonstrate with reasonable certainty that (a) the reagents were made up correctly, (b) the standards were made up correctly, (c) there was no contamination present, (d) the spectrophotometer was set up correctly and (e) the analysis can be repeated and give a result to within the expected limit. computer scienceLay out the formulae for calculating the results ensuring a ll terms are clearly defined and derived. Specify requirements for checking, cross reference to QC requirements and indicate how corrections should be dealt with.reportage Procedures Including Expression Of ResultsIndicate how results should be reported, including rounding of numbers final units. It may be appropriate to indicate the level of associated with the method. Results are reported to two significant figures as mg dm-3 Nitrite (NO2) except where the customer has asked for the results to be reported as mg dm-3 Nitrogen in which case the analytical results are multiplied by 14/46. * Where significant dilutions have to be made then a comment about the dilution used should be put on the sheet used to report the results. Precision , accuracy and detection limits Spectrophotometric measurements on the same solution must have an absorbance range no greater than 0.003. A significant absorbance for a sample is 0.010 (after correction for the blank). A detection limit of 0.01 mg d m-3 (equivalent to an absorbance of approximately 0.010) is quoted for a 30 cm3 sample. This becomes 0.1 mg dm-3 for an effluent sample where the amount of sample taken is 3 cm3. Where typical absorbances readings (as listed in the log book) cannot be obtained for the standard, quality control and the blank, then further investigations must be carried out until the cause of the problem is found. * The results obtained for replicate analysis should be monitored, any significant difference ( 0.010 mg dm-3 ) should be investigated Literature ReferencesReferences may include operating manuals as well as published methods and standards.This method is based on Method H in the Department of the Environment Standing Committee of Analysts booklet Oxidised Nitrogen in water 1981.Annex Method Validation and Measurement UncertaintyMethods should be supported by experimental data providing information on accuracy, precision and selectivity . The major sources of uncertainty, relating to th e method should be identified and the assigned values listed. The overall uncertainty should be listed together with an explanation of how it was derived.In the case of the nitrite method that was based on a published method, the validation work involvedReproducibility showing comparable results were obtained. Repeatability showing in the results obtained for a known sample measured five times on the same day. Making up a set of 5 standards to show that the calibration was linear for the range 0.01 to 0.25 mg dm-3 NO2. Checking the detection limit using spiked samples . Checking that the time interval quoted for the colour development time was correct and non-critical within the stated range. We also looked at the method to identify major causes of magnetic declination in results e.g. measuring the sample volume with a measuring cylinder. We found that the biggest variation was in different analysts making up the same standard solutions therefrom the need to define an acceptab le absorbance range for the standard.