Process Waters. Drinking Water. Purified Water. Ultrapure Water. The great majority of samples for TOC are taken and analyzed in a laboratory. On-line analyses are used for higher level TOC analyses when the required frequency or speed of analysis makes it preferable. On-line measurements are also essential for the measurement of TOC levels below 50ppb to avoid contamination. This contamination can be from extraneous TOC in the environment or containers but, more seriously, from carbon dioxide in the air which will rapidly dissolve in pure water.
Carbon dioxide interferes with many of the techniques used to monitor trace TOC. TOC is universally measured by oxidizing the organic compounds present to forms which can be quantified. A variety of oxidation and detection methods are used depending on the nature and concentration of TOC being measured and the analytical requirements e. Persulphate oxidation, enhanced by UV or heat, is widely used for laboratory TOC determination in many types of water from potable to pharmaceutical and electronic grades.
The CO2 produced is usually measured by NDIR or by the change of conductivity that it produces when dissolved in a separate stream of pure water. To exclude the effect of other oxidation products the gas may be passed through a membrane. Good oxidation can be achieved but a compensation method is needed to account for the blank from the reagent. TOC at ppb levels can be detected. IC can be removed by acidifying the sample to a pH value of two or less to release IC as CO2 which can be measured or vented to waste. The situation is somewhat different for high purity waters with a low conductivity.
Water with a sufficiently low conductivity resistivity approaching As discussed before, all such trace-level measurements must be done on-line. A number of TOC monitors have evolved to meet the need for rapid monitoring of low ppb TOC levels in high purity laboratory water systems. A rapid response is needed to ensure that the results are available and relevant to the relatively small volumes of water being dispensed.
These monitors, generally, measure the conductivity of the water before and after oxidation; the change is calibrated against TOC content. Using a middle to high calibration standard, conduct a typical analysis. Any alternate column must be capable of yielding symmetrical peak elution for this perchlorate response as demonstrated by yielding a Peak Gaussian Factor of between 0. Proper suppressor If the instrument begins to have problems with reduced peak response or asymmetrical perchlorate peaks, the suppressor membranes should be cleaned.
Other computer based data systems may achieve approximately the same performance but the user should demonstrate this by the procedures outlined in Section 9. These cartridges are used to remove particulates from the sample matrix while loading the sample manually or if the autosampler employed does not filter the sample during loading. These cartridges are conditioned according to the manufacturer's directions and are used to reduce the matrix levels of sulfate.
These cartridges are conditioned according to the manufacturer's directions and are used to reduce the matrix levels of chloride. These cartridges are conditioned according to the manufacturer's directions and are used to reduce cations in the sample matrix. This protects the analytical column by removing silver which has leached from the Ag cartridge and may indirectly minimize the effect of carbonate by removing the cationic counter ion. Any alternate columns will likely have unique and specific conditions identified by the manufacturer.
This contamination will result in poor reproducibility of perchlorate retention times, elevated Consequently, exposure to the atmosphere should be minimized by storing these eluent solutions in sealed reservoirs under low pressure 3 to 5 psi helium. In addition, these solutions should be regularly prepared and held for no more than 5 days.
When refilling the eluent reservoir, completely replace old eluent solution by emptying the old eluent, rinsing the reservoir with reagent water, and refilling with the freshly prepared eluent solution. With this eluent, the suppressed conductivity detector background signal should be between 2 - 5 uS. This effectively removes dissolved gases which may form micro bubbles in the 1C, compromising system performance and adversely effecting the integrity of the data. Alternatively, an in-line degas apparatus maybe employed. NOTE: Sodium perchlorate represents a molar weight fraction of However, specified expiration dates should be marked on each prepared stock standard as part of any laboratory's quality control program, hi this regard, it is recommended that stock standards for perchlorate be held for no more than 12 months and an expiration date should be clearly specified on the label.
This solution is used to prepare simulated common anion samples in the determination of the MCT Section 9. The volume collected should be sufficient to insure a representative sample, allow for replicate analysis and laboratory fortified matrix analysis, if required, and minimize waste disposal. A thermally insulated sampling kit, designed to fit sampling bottles securely during shipment, should be used to protect the samples from these temperature extremes.
Typically, when analytes are believed to be stable, a 28 day holding time is established as a sufficient time period to permit a laboratory to conduct the analysis. The requirements of this program consist of an initial demonstration of laboratory capability, and subsequent analysis in each analysis batch Section 3. This section details the specific requirements for each of these QC parameters. The QC criteria discussed in the following sections are summarized in Section 17, Table 5 Calculate the mean measured concentration Cx of the replicate values as follows.
The source of the problem must be identified and corrected before either proceeding with the IDC or continuing with on-going analyses. These seven MDL replicate analyses may be performed gradually over three days or may represent data that has been collected, at a consistent MDL estimated concentration, over a series of more than three days. The MRL should be established at an analyte concentration either greater than three times the MDL or at a concentration which would yield a response greater than a signal to noise ratio of five.
Although the lowest calibration standard may be below the MRL, the MRL must never be established at a concentration lower than the lowest calibration standard. Next, the series of sequentially If a laboratory's MRL is higher, choose a perchlorate concentration for this exercise at approximately 5 times that MRL. Next, add 0. In many data acquisition and instrument control software, the peak area to height ratio is a definable parameter which can be specified for printout on the analysis report.
As the peak is distorted, the area will also eventually begin to be distorted and the quantitated concentration will be reduced, but this is typically secondary, with the ratio of peak area to height initially predicting this pending quantitation problem. X 9. To derive the MCT, perform a linear regression on these data by plotting PDjvu as the independent variable, x versus the matrix conductance as the dependent variable, y. This solution must contain perchlorate, at the laboratory determined MRL, as well as the common anions chloride, sulfate and carbonate, prepared consistent with the instruction for the mixed anion solutions in this section and at a concentration estimated to generate a conductance near the MCT.
If the MRL recovery When the conductance of a field sample is above the MCT, sample dilution or pretreatment, as described in respective Sections Data produced are used to assess instrument performance of a blank sample and evaluate contamination from the laboratory environment. Values that exceed 1A the MRL indicate a laboratory or reagent contamination is present. The source of the contamination must be determined prior to conducting any sample analysis.
Total Organic Carbon (TOC) and its Measurement
Any sample included in an automated analysis batch which has an invalid LRB, indicated by a quantitated perchlorate that exceeds 1A the MRL, must be reanalyzed in a subsequent analysis batch after the contamination problem is resolved. If an analysis batch only contains pretreated samples, then only a pretreated LRB is required.
The IPC is three tiered and is used to verify the state of the 1C system, over time, to quantitate perchlorate in highly ionic matrices. This must be conducted with each analysis batch since over time, column performance can change. This solution must be prepared consistent with the instruction in Section 9. This perchlorate concentration has been specified assuming the MRL has been set in the range of 3. If a laboratory's MRL is The observed retention time for perchlorate should closely replicate the times established when the column was originally installed.
A laboratory should retain a historic record of retention times for perchlorate to provide evidence of an analytical column's continued performance. This separate, An external source stock or QCS, which is used to verify the accuracy of the calibration curve when it was initially prepared Section Laboratories are required to analyze a LFB filtered as if it were a field sample with each analysis batch immediately following the ICCS. The LFB must be prepared with the same solution used to prepare the LFM and should be prepared at concentrations no greater than ten times the highest concentration observed in any field sample and should be varied to reflect the range of concentrations observed in field samples.
If any deviations in the perchlorate concentration are present, it will be reflected in the LFB and not exclusively attributed to a matrix upon analysis of the LFM. Calculate accuracy as percent recovery Section 9. If the LFB recovery for an analysis batch does not meet these recovery criteria the data are considered invalid, and the source of the problem should be identified and resolved before continuing analyses.
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If an analysis batch only contains pretreated samples, then only a pretreated LFB is required. Samples which exceed the MCT must either be diluted Section Samples which are pretreated have additional LFM requirements described in Section For a LFM to be valid, the target analyte concentrations must be greater than the native level and should adhere to the requirement outlined in Section 9. Fortified samples that exceed the calibration range must be diluted to be within the linear range, hi the event that the fortified level is less than the observed native level of the unfortified matrix, the recovery should not be calculated.
This is due to the difficulty in calculating accurate recoveries of the fortified concentration when the native sample concentration to fortified concentration ratio is greater than one. The LFM should not be prepared at concentration greater than ten times the highest concentration observed in any field sample and should be varied to reflect the range of concentrations expected in field samples. Repeated failure to meet suggested recovery criteria indicates potential problems with the procedure and should be investigated.
The sample matrix selected for this duplicate analysis must contain measurable concentrations of the target Without prior knowledge or strong suspicion that an unknown sample has measurable perchlorate concentrations, the best alternative is to analyze a duplicate LFM. Each time such modifications to the method are made, the analyst is required to repeat the procedure in Section 9. Whenever possible, the laboratory should perform analysis of quality control check samples and participate in relevant proficiency testing PT or performance evaluation PE sample studies.
Initial calibration verification is performed using a QCS as well as with each analysis batch using an initial, continuing when more than 10 field samples are analyzed , and end calibration check standards. The procedures for establishing the initial calibration curve are described in Section The procedures to verify the calibration with each analysis batch is described in Section The restriction of two orders of magnitude is prescribed since beyond this it is difficult to maintain linearity throughout the entire calibration range.
Tabulate peak area responses against the perchlorate concentration. The results are used to prepare a calibration curve. Acceptable calibration is confirmed after reviewing the curve for linearity second order fits are also acceptable and passing the criteria for the initial calibration check standard in Section Peak height can tend to be suppressed as a result of high levels of common anions in a given matrix which can compete for exchange sites leading to peak broadening. Using peak areas, it is the analyst's responsibility to review all chromatograms to insure accurate baseline integration of target analyte peaks, since poorly drawn baselines will significantly influence peak areas.
The QCS should be prepared at a concentration near the middle of the calibration curve. As specified in Section 9. Once the calibration curve has been established it MUST be verified for each analysis batch, prior to conducting any field sample analysis using an Initial Calibration Check Standard. The lowest level standard used to prepare the linear calibration curve must be used, hi cases where the analyst has chosen to set the MRL above the lowest standard, a standard at a concentration equal to the MRL is acceptable.
If more than 10 field samples are included in an analysis batch, the analyst must alternate between the middle and high continuing calibration check standard levels. The source of the problem must be identified and resolved before reanalyzing the samples or continuing analyses. However, all field samples between the middle and end calibration checks MUST be reanalyzed. The dilution procedure is found in Section Pretreatment is described in Section The exact magnitude of this dilution will adversely increase the MRL by an equivalent proportion.
Round up to the next whole number and dilute the sample by a proportion equivalent to this value. Analyze the sample as specified in Section If no perchlorate is measured above the elevated MRL and analysis or project objectives If sample dilution did not yield the required results, sample pretreatment should be employed.
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When the MCT is exceeded, it is most often due to a high levels of common anions chloride, sulfate, and carbonate in a particular matrix. If the analyst were to attempt the 1C analysis of this particular matrix, the common anions present in the sample would distort the baseline and negatively affect the accurate quantitation of perchlorate.
To effectively reduce a significant amount of these anions which contribute to the high conductivity reading, a series of pretreatment cartridges must be employed. For this pretreatment, three cartridges are attached in series in the following order: Ba, Ag, and H. It is recommended that all three cartridges be employed unless the analyst has specific knowledge that a matrix primarily has high levels of a specific common anion. Perform this rinse per manufacturer's instructions.
These pretreated quality control samples are required when an analysis batch contains a matrix which must be pretreated. The pretreated LRB and LFB are used to verify that no background interference or bias is contributed by the pretreatment. If a response is observed in the pretreated LRB, triple or quadruple the volume of reagent water rinse suggested by the manufacturer in Section If this additional rinsing procedure is required, it must be consistently applied to all the cartridges prior to conducting any matrix pretreatment.
This flow rate is critical to the pretreatment and must be carefully followed. Discard this fraction and begin collecting the pretreated sample aliquot of collected sample. If the conductance is now below the MCT, the sample is ready for analysis. If the conductance is still above the MCT, the flow rate through the pretreatment cartridge is likely too fast and the pretreatment should be repeated with new cartridges.
In some instances, double pretreatment cartridges may need to be applied. When this pretreatment is performed properly, U. This LFM must be fortified with perchlorate at concentrations close to, but greater than, the level determined in the native sample prior to the pretreatment. Initially, the pretreated sample is analyzed and perchlorate level is determined. Then, a second aliquot of sample must be fortified with perchlorate, pretreated to reduce the high common anion levels, and analyzed to assess perchlorate recovery from that matrix. This additional QC is required to rule out matrix effects and to confirm that the laboratory performed the pretreatment step appropriately.
Using a Luer lock, plastic 10 mL syringe, withdraw approximately 10 mL of sample from the micro beaker and attach a 0. Filter the sample into an autosampler vial or manually load the injection loop injecting a fixed amount of filtered, well mixed sample. If using a manually loaded injection loop, flush the loop thoroughly between sample analysis using sufficient volumes of each new sample matrix. Included in this table is the estimated retention time for perchlorate which has been achieved by this method. Other columns, chromatographic conditions or detectors maybe used if the requirements of Sections 1.
Lastly, analyze the LFB. Record the resulting peak size in area units and retention time for each analyte. The experience of the analyst should weigh heavily in the interpretation of these chromatograms. The response generated by these three new high concentration calibration standards must not exceed the upper linear range for the conductivity detector. The latter procedure involves significantly more time than a simple sample dilution therefore, it is advisable to collect sufficient sample to allow for sample dilution and sample reanalysis, if required.
This will spread out the peaks, causing later elution of perchlorate. Analysts are advised to carefully evaluate any of these eluent dilutions since when these eluent changes are incorporated, other coelutions may be encountered which were not initially evident. Additionally, the analyst must verify that this dilution does not negatively affect performance by repeating and passing all the QC criteria in Section 9, and by reestablishing a valid initial calibration curve Section When conducting automated analyses, careful attention must be paid to ensure sufficient volume of eluent in the reservoir is available to sustain extended operation.
In order to ensure their data are of acceptable quality, laboratories must ensure that all QC performance criteria are met throughout the analysis batch through subsequent careful inspection of the data. To help with this task, an acceptable sequence for a sample analysis batch, with all the method-required QC, is shown in Table 7. This schedule is included only as an example of a hypothetical analysis batch which contains normal sample matrices as well as samples which have failed the MCT.
If the perchlorate retention time has slightly shifted generally towards shorter times since the initial calibration, but is still within acceptance criteria and are reproducible during the analysis batch, the analyst should use the retention time in the daily calibration check standards to confirm the presence or absence of perchlorate anion. If the fortified sample reveals a split or shouldering peak response, the low concentration in the unfortified sample is likely an interferant and should not be reported as perchlorate.
Samples with a perchlorate response which exceeds the highest calibration standard concentration must be diluted and reanalyzed. When this is not possible the alternate calibration procedures described in Section Samples with perchlorate identified but quantitated below the concentration established by the lowest calibration standard, may be reported as "trace present" above the MDL but below the minimum reporting limit MRL and therefore not reported as a quantitated concentration. This retention time is graphically indicated in the chromatograms in Figures 1 through 4.
The HIW was designed to simulate a high ionic strength field sample and the HOW designed to simulate a high organic content field sample. The HOW was prepared from reagent water fortified with Conditions investigated included sample bottle construction HDPE plastic vs. Each data point in this table represents the mean percent recovery following triplicate analyses. These data were used to formulate the holding times shown in Section 8.
The chromatogram shown in Figure 4 were generated using the AS 16 column. When wastes cannot be feasiblely reduced at the source, the Agency recommends recycling as the next best option. The Agency urges laboratories to protect the air, water, and land by minimizing and controlling all releases from hoods and bench operations, complying with the letter and spirit of any waste discharge permit and regulations, and For further information on waste management consult the "Waste Management Manual for Laboratory Personnel," available from the American Chemical Society at the address listed in Section Jackson, P.
Okamoto, H. Report on the interlaboratory validation of 1C methods for perchlorate. Glaser, J. Code of Federal Regulations 40, Pt. Standard Solutions for Calibrating Conductivity Cells, p. D, 70th Ed. Stability when stored in various sampling bottles - All stored at room temperature Matrix Bottle type Unfortified Fortified Conc. Room Temperature adequate for shipping and storage. Holding time must not be exceeded. At least 5 calibration standards are recommended. Prepare mixed common anion solution at the MCT prepared consistent with procedures in Section 9. Confirm the sample's conductance and analyze at the beginning of each analysis batch.
The concentration selected for the LFB in subsequent analysis batches should be varied throughout the calibration range. Sample results from batches that fail LFB are invalid. Fortification must be made prior to pretreatment.
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Sample results from batches that fail a pretreated LFB are invalid. LFM must be fortified above the native level and at no greater than 10 x the highest field sample concentration. Calculate target analyte recovery using formula Sect. When a sample exceeds the MCT and pretreatment is employed to reduce the common anion levels, an additional LFM must be prepared from this matrix and subsequently pretreated exactly as the unfortified matrix.
Calculate the relative percent difference RPD using formula in Section 9. PGF must fall between 0. Wagner and Barry V. In addition, bromide can be accurately determined in source or raw water and it has been included due to its critical role as a disinfection by-product precursor. Bromide concentration in finished water can differ significantly between preserved and unpreserved samples and should not be attempted due to numerous variables which can influence the concentration.
Users of the method must demonstrate the ability to generate acceptable results with this method, using the procedures described in Section 9. Larger injection loops may be employed. An analysis batch must also include all required QC samples, which do not contribute to the maximum field sample total of The CAL Analysis of the initial sample Lj and the duplicate sample [ Dc Section 9. The LFM is analyzed exactly like a sample, and its purpose is to determine whether the field sample matrix contributes bias to the analytical result.
The background concentrations of the analytes in the field sample matrix must be determined in a separate, unfortified aliquot and the measured values in the LFM corrected for background concentrations. The' LRB is used to determine if method analytes or other interferences are present in the laboratory environment, the reagents, or the apparatus. This defined concentration can be no lower than the concentration of the lowest calibration standard and can only be used if acceptable quality control criteria for the ICCS are met.
Frequently, an aliquot of this solution is added to a known volume of reagent water and analyzed with procedures used for samples. The analyst must verify that these changes do not induce any negative affects on method performance by repeating and passing all the QC criteria as described in Section 9. With any proposed pretreatment, the analyst must verify that target analyte s are not affected by monitoring recovery after pretreatment. Normally, in this analysis, the elution of sulfate retention time of If residual chlorine dioxide is suspected in the sample, the sample must be purged with an inert gas helium, argon or nitrogen for approximately five minutes.
This sparging must be conducted prior to ethylenediamine preservation and at the time of sample collection. In order to accurately quantify bromate concentrations in the range 0.
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NOTE: Because of its acidic nature and high salt content, the PCR MUST be flushed from the reaction coil upon completion of the final analysis and prevented from draining through the reaction coil by gravity once the system is shut down. This can be accomplished either manually or by incorporating a column switching valve in combination with a flush and close method in the schedule. NOTE: The use of 2 mm columns is not recommended.
A 50 uL sample loop would be required with the 2 mm columns. This reduced injection volume would decrease the "on-column" bromate and negatively affect PCR reactivity and the subsequent absorbance response. As well, the 2 mm columns require a flow rate approximately 4 times less than the 4 mm columns. At the lower flow rates, band broading may become an issue and it would be difficult, if not impossible, to accurately maintain the appropriate reduced flow rate for the PCR.
The suppressor must be able to withstand approximately 80 psi back pressure which results from connecting the postcolumn hardware to the eluent out side of the suppressor. Insufficient baseline stability was observed on the conductivity detector using the ASRS in recycle mode. A laboratory must generate comparable data as a result of a complete IDC Section 9. The pressure settings will need to be established on an individual basis for each specific instrument configuration and at a level which yields the prescribed PCR flow rates. Dionex PCH- 2, or equivalent.
Other computer based data systems may achieve approximately the same MDLs but the user must demonstrate this by the procedure outlined in Section 9. Opaque or amber bottles are required due to the photoreactivity of the chlorite anion. These cartridges are used to remove particulates and [Fe OH 3 s ] which is formed during the oxidation-reduction reaction between Fe H and C1O2". These cartridges are conditioned according to the manufacturer's directions and are used to protect the analytical column and the suppressor membrane by removing excess ferrous iron [Fe H ].
The ferrous iron is added to field samples to reduce chlorite levels prior to analysis of chlorine dioxide disinfected water samples. Alternatively, an in-line degas apparatus may be employed. Chlorite requires careful consideration as outlined below in Section 7. The simplest approach is to determine the exact purity of the NaCIO 2 using the iodometric titration procedure. If the surrogate is removed, the laboratory must adhere to the alternate QC requirements found in Section 9. P, St. Louis, MO, or equivalent. Two-hundred-and-fifty milligrams of purified grade o-dianisidine, dihydrochloride salt [ ODA , Sigma, Cat.
D, or equivalent ] are dissolved, with stirring, in mL methanol Spectrophotometric grade, Sigma, Cat. M, St. Louis MO, or equivalent. The reagent is stable for up to one month. ONLY the purified grade of this reagent is acceptable. The purified ODA dihydrochloride salt is a white, fine crystalline powder. NOTE: All glassware used to prepare the postcolumn reagent must be thoroughly rinsed with reagent water prior to use. A champagne or light amber Over several hours, this slight coloration will fade.
Consequently, the PCR must be prepared in advance and allowed to sit until it is clear, for a minimum of 4 hours preferably overnight prior to use. Occasionally, no matter how well all the glassware used to prepare the postcolumn reagent is rinsed, a darkly colored solution oxidized ODA may result. These solutions MUST be discarded. For this reason, it is recommended that the PCR be made in a series of mL lots with dedicated glassware.
The clear solution should be filtered using a 0. The Fe IT solution must be prepared fresh every two days. Add a sufficient volume of the EDA preservation solution Section 7. The requirements of this program consist of an initial demonstration of laboratory capability IDC , and subsequent analysis in each analysis batch Section 3.
This section details the specific requirements for each of these QC parameters for both the conductivity and absorbance detectors used in this application. Although this method involves both conductivity and absorbance detection, the MDLs and MRLs may differ but the QC requirements and acceptance criteria are the same for both detectors.
The QC criteria discussed in the following sections are summarized in Section 17, Tables 4 and 5. For the absorbance detector, prepare 7 replicate LFBs fortified at a recommended concentration of 2. The source of the problem must be identified and corrected before proceeding with the IDC. The replicates must be prepared and analyzed over three days.
Report the concentration values in the appropriate units. Data produced are used to assess contamination from the laboratory environment. Analytes that exceed this level will invalidate the analysis batch for that method analyte in all corresponding field samples. When these types of pretreated samples, or any type of pretreatment is applied to field samples included as part of an analysis batch, a second LRB must be prepared, pretreated and analyzed to confirm no background effects of the pretreatment are present.
If the analysis batch contains only pretreated samples, then only a pretreated LRB is required. Since calibration solutions are prepared in large volumes and can be used over an extended period of time, the integrity of the concentration of the solution used to fortify the LFM is checked by analyzing the LFB. The recovery of all analytes must fall in the acceptable recovery range, as indicated below, prior to analyzing samples.
If the LRB recovery for an analysis batch does not meet these recovery criteria the data are considered invalid, and the source of the problem must be identified and resolved before continuing with analyses. As specified in Section This analysis confirms the MRL and demonstrates proper chromatographic performance at the beginning of each analysis batch. Chromatographic performance is judged by calculating the Peak Gaussian Factor PGF , which is a means to measure peak symmetry and monitoring retention time drift in the surrogate peak over time.
If these criteria are not met, corrective action must be performed prior to analyzing additional samples. Major maintenance like replacing columns require rerunning the IDC Section 9. A laboratory should retain a historic record of retention times for the surrogate and all the target anions to provide evidence of an analytical columns vitality. In this case, no measurement of PGF is required. However, the laboratory must carefully monitor the bromate retention time in the ICCS as an alternate to the surrogate retention time and, in the same manner, adhere to those specifications set forth in Section 9.
Additional LFM requirements, as described in Section 9. For a LFM to be valid, the target analyte concentrations must be greater than the native level and must adhere to the requirement outlined in Section 9. It is recommended that the solutions used to fortify the LFM be prepared from the same stocks used to prepare the calibration standards and not from external Fortified samples that exceed the calibration range must be diluted to be within the linear range. In the event that the v ' fortified level is less than the observed native level of the unfortified matrix, the recovery should not be calculated.
Repeated failure to meet suggested recovery criteria indicates potential problems with the pjrocedure and should be investigated. Initially, the field , sample is analyzed and chlorite, chlorate and bromide levels are determined. Then, a second aliquot of field sample is pretreated to remove chlorite, as described in Section A third aliquot of the field sample then must be fortified with bromate, pretreated as described in Section This additional QC is required to rule out matrix effects and to confirm that the laboratory performed the chlorite removal step Section This LFM should be fortified with bromate at concentrations close to but greater than the level determined in the native sample.
Recoveries are determined as described above Section 9. If the second analysis also fails the recovery criterion, report all data for that sample as suspect. The sample matrix selected for this duplicate analysis must contain measurable concentrations of the target anions in order to establish the precision of the analysis set and insure the quality of the data. If none of the samples within an analysis batch have measurable concentrations, the LFM should be repeated as a laboratory duplicate.
The specific practices that are most productive depend upon the needs of the laboratory and the nature of the samples. Whenever possible, the laboratory should perform analysis of quality control check standards and participate in relevant proficiency testing PT or performance evaluation PE sample studies. Initial calibration verification is performed using a QCS as well as with each analysis batch using an initial, continuing when more than 10 field samples are analyzed , and end calibration standards. On the conductivity detector for the four target analytes chlorite, bromate, bromide and chlorate the linear range should cover the expected concentration range of the field samples and should not extend over more than two orders of magnitude in concentration.
Because high Bromate concentrations are expected to be significantly lower. It is suggested that the conductivity detector be calibrated using at least five bromate calibration standard levels in the range u. The conductivity detector will observe a response for bromate at concentration below Prior to using mixed standards for calibration, it must be ensured that the individual calibration standards do not contain any appreciable concentrations of the other target analytes. The addition of EDA to all reagent water prepared calibration and quality control samples is required not as a preservative but rather as a means to normalize any bias contributed by the addition of EDA to preserve the field samples.
This is done by adding 20 uL of the surrogate solution Section 7. Next, transfer These volumes may be adjusted to meet specific laboratory autosampler volume requirements provided the fortified surrogate concentration is at the prescribed concentration of 1. The calibration standard is now ready for analysis. The same surrogate Li this situation, the laboratory must adopt the QC protocol outlined in Section 9. Increased sensitivity for low level detection of bromate by PCR can be achieved by increasing the injected sample volume. The results are used to prepare calibration curves using linear regression analysis for each analyte on the conductivity detector and using a quadratic regression analysis for bromate on the absorbance detector.
Using peak areas, it is the analyst responsibility to review all chromatograms to insure accurate baseline integration of target analyte peaks, since poorly drawn baselines will more significantly influence peak areas than peak heights. The QCS should be prepared at a concentration near the middle of the calibration and is best to be analyzed in triplicate. Once the calibration curves have been established for both the conductivity and absorbance detectors, they must be verified for each analysis batch, prior to conducting any field sample analyses using an Initial Calibration Check Standard.
Since two detectors are incorporated in this method, this must be accomplished by using a mixed calibration check standard for the four conductivity analytes and a separate low level bromate initial calibration check standard for the absorbance detector, hi both cases, the lowest level standard used to prepare the calibration curve must be used. In cases where the analyst has chosen to set the MRL above the lowest standard, a standard at a concentration equal to or below the MRL is acceptable.
For the reasons noted above, two separate continuing and end calibration check standards must be incorporated. The source of the problem must be identified and resolved before reanalyzing the samples or continuing with the analyses. However, all field samples between the middle and end calibration check standards must be reanalyzed. Next, place a The sample is now ready for analysis.
In this situation, the laboratory must adopt the QC protocol outlined in Section 9. Filter the sample into an autosampler vial if vial is not designed to automatically filter or manually load the injection loop injecting a fixed amount of filtered, well mixed sample. Since chlorite can interfere with the postcolumn quantitation of low levels of bromate as described in Section 4. The sample is then filtered using a 0. Prior to using any pretreatment, each lot of cartridges must be QC checked to insure proper analyte recoveries are maintained and laboratory reagent blanks are free from interferences.
In addition, consistent lots of reagents, pretreatment cartridges, and membrane cartridges must be used throughout an entire analysis batch to maintain assured QC uniformity. After mixing, verify the pH is between 5 and 6 using pH test strips, add 40 uL of ferrous iron solution Section 7. Filter the reaction mixture using a 0. Pass the solution through a hydrogen cartridge at a flow rate of approximately 2 mL per minute.
Discard the first 3 mL, and collect an appropriate volume depending on autosampler vial size for analysis. Add the respective volume of surrogate solution, depending on the volume collected, and the sample is ready for analysis. NOTE: Pretreated samples can be held for no more than 30 hours after initial pretreatment. If this time has expired, the pretreatment steps must be repeated on a second aliquot of both the field sample matrix and the respective LFM. Initially, the field sample is analyzed and chlorite, chlorate and.
Then, a second aliquot of field sample is pretreated to remove chlorite, as described above and analyzed to determine native bromate concentrations. The occurrence of organic compounds in water is a matter of increasing concern to the industry, ecologists and general public from the point of view of possible health hazards presented to both human and animal life. It has been well established that an amazing number of organic substances pesticides, detergents, solvents are released into the sea, rivers and lakes.
Industrial e. The availability of sophisticated analytical methods sensitive enough to determine extremely low concentrations of pollutants enables us to realize the extent and the nature of environmental contamination in natural water. Unable to display preview. Download preview PDF. Skip to main content. Advertisement Hide. Authors Authors and affiliations D. Kotzias C. This process is experimental and the keywords may be updated as the learning algorithm improves.
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