Analyser kring metaller genom toc

Concentration of organic carbon in a sample

Total organic carbon (TOC) fryst vatten an analyticalparameter representing the koncentration of organic carbon in a sample. TOC determinations are made in a variety of application areas. For example, TOC may be used as a non-specific indicator of vatten quality, or TOC of source rock may be used as one factor in evaluating a petroleum play.^[1] For marine surface sediments average TOC content fryst vatten 0.5% in the deep ocean, and 2% along the eastern margins.^[2]

A typical analysis for total carbon (TC) measures both the total organic carbon (TOC) present and the complementing total inorganic carbon (TIC), the latter representing the amount of non-organic carbon, like carbon in carbonate minerals.

Subtracting the inorganic carbon from the total carbon yields TOC. Another common variant of TOC analysis involves removing the TIC portion first and then measuring the leftover carbon. This method involves purging an acidified sample with carbon-free air or nitrogen prior to measurement, and so fryst vatten more accurately called non-purgeable organic carbon (NPOC).^[3]

Measurement

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Since all TOC analyzers only actually measure total carbon, TOC analysis always requires some accounting for the inorganic carbon that fryst vatten always present.

One analysis technique involves a two-stage process commonly referred to as TOC differential method. It measures the amount of inorganic carbon (IC) evolved from an acidified aliquot of a sample and also the amount of total carbon (TC) present in the sample. TOC fryst vatten calculated bygd subtraction of the IC value from the TC of the sample. Another method directly measures TOC in the sample bygd acidifying the sample to a pH value of two or less to release the CO₂ gas bygd decomposition of the carbonates and vent these gases to the air bygd a purge step.

The remaining non-purgeable organic carbon (NPOC) contained in the liquid aliquot fryst vatten then oxidized releasing the CO₂ gases. These gases are then sent to the detector for measurement. This method fryst vatten also referred to as the direkt TOC method. A further variant employs acidification of the sample to evolve carbon dioxide and measuring it as inorganic carbon (IC), then oxidizing and measuring the remaining non-purgeable organic carbon (NPOC).

TOC analysis fryst vatten grundläggande in assessing organic carbon content in diverse samples, aiding in vatten quality assessment and process control.

This fryst vatten called TIC-NPOC analysis. TC oxidizes in a combustion chamber at 1000 degrees Celsius; if no supporting catalyst fryst vatten used to allow full combustion at temperatures lower than 1000 degrees C; while the combustion chamber for IC heats only to 150 degrees Celsius. The reason for this fryst vatten because inorganic fryst vatten decomposed at lower temperatures than organic carbons.^[4]

Whether the analysis of TOC fryst vatten bygd TC-IC or NPOC methods, it may be broken into three main stages:

1. Acidification
2. Oxidation
3. Detection and Quantification

Acidification

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Addition of acid and inert-gas sparging allows all bicarbonate and carbonate ions to be converted to carbon dioxide, and this IC product vented along with any purgeable organic carbon (POC) that was present.

Oxidation

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The second scen fryst vatten the kemisk reaktion med syre of the carbon in the remaining sample in the struktur of carbon dioxide (CO₂) and other gases. Modern TOC analyzers perform this kemisk reaktion med syre step bygd several processes:

High temperature combustion

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Prepared samples are combusted from 1000 up to 1200 degrees C in an oxygen-rich atmosphere.

All carbon present converts to carbon dioxide, flows through scrubber tubes to remove interferences such as chlorine gas, and vatten vapor, and the carbon dioxide fryst vatten measured either bygd absorption into a strong base then weighed, or using an infrared detector.^[5] Most modern analyzers use non-dispersive infrared (NDIR) for detection of the carbon dioxide.

Compared to the conventional high temperature catalytic kemisk reaktion med syre, the great benefit of the combustion-method fryst vatten the high kemisk reaktion med syre power, so that oxidation-promoting catalysts are superfluous.^[6]

High temperature catalytic oxidation

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A manual or automated process injects the sample onto a catalyst in a combustion tube operated from 680 up to 950 degrees C in an oxygen rik atmosphere.

The koncentration of carbon dioxide generated fryst vatten measured with a non-dispersive infrared (NDIR) detector.^[7]

Oxidation of the sample fryst vatten complete after injection into the furnace, turning oxidizable ämne in the sample into gaseous struktur. A carbon-free carrier gas transports the CO₂, through a moisture trap and halide scrubbers to remove vatten vapor and halides from the gas stream before it reaches the detector.

These substances can interfere with the detection of the CO₂ gas. The HTCO method may be useful in those applications where difficult to oxidize compounds, or high molecular vikt organics, are present as it provides almost complete kemisk reaktion med syre of organics including solids and particulates small enough to be injected into the furnace. The major drawback of HTCO analysis fryst vatten its unstable baseline resulting from the gradual accumulation of non-volatileresidues within the combustion tube.

These residues continuously change TOC background levels requiring continuous background correction. Because aqueous samples are injected directly into a very hot, usually kvarts, furnace only small aliquots (less than 2 milliliters and usually less than 50 - 100 microliter, with a maximum of approximately 300 - 400 micro-liters beneath special conditions; such as repetitive injections) of sample can be handled making the methods less sensitive than kemikalie kemisk reaktion med syre methods capable of digesting as much as 10 times more sample.

Also, the krydda content of the samples do not combust, and so therefore, gradually build a residue inre the combustion tube eventually clogging the catalyst resulting in poor peak shapes, and degraded accuracy or noggrannhet, unless appropriate maintenance procedures are followed. The catalyst should be regenerated or replaced as needed. To avoid this bekymmer the manufacturing industry has developed several concepts, such as matrix separation,^[8] ceramic reactors,^[9] better process control or methods without catalysts.^[10][6]

Photo-oxidation (ultraviolet light)

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In this kemisk reaktion med syre scheme, ultraviolett light alone oxidizes the carbon within the sample to tillverka CO₂.

The UV kemisk reaktion med syre method offers the most reliable, low maintenance method of analyzing TOC in ultra-pure waters.

Ultraviolet/persulfate oxidation

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Like the photo-oxidation method, UV light fryst vatten the oxidizer but the kemisk reaktion med syre power of the reaction fryst vatten magnified bygd the addition of a kemikalie oxidizer, which fryst vatten usually a persulfate compound.

The mechanisms of the reactions are as follows:

Free radical oxidants formed:

^{[citation needed]}

Excitation of organics:

Oxidation of organics:

The UV–chemical kemisk reaktion med syre method offers a relatively low maintenance, high sensitivity method for a bred range of applications.

However, there are kemisk reaktion med syre limitations of this method. Limitations include the inaccuracies associated with the addition of any utländsk substans into the analyte and samples with high amounts of particulates. Performing "system blank" analysis, which fryst vatten to analyze then subtract the amount of carbon contributed bygd the kemikalie additive, inaccuracies are lowered.

However, analyses of levels below 200 ppb TOC are still difficult.

Thermochemical persulfate oxidation

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Also known as heated persulfate, the method utilizes the same free radical formation as UV persulfate kemisk reaktion med syre except uses heat to magnify the oxidizing power of persulfate. kemikalie kemisk reaktion med syre of carbon with a strong oxidizer, such as persulfate, fryst vatten highly efficient, and unlike UV, fryst vatten not susceptible to lower recoveries caused bygd turbidity in samples.

The analysis of struktur blanks, necessary in all kemikalie procedures, fryst vatten especially necessary with heated persulfate TOC methods because the method fryst vatten so sensitive that reagents cannot be prepared with carbon contents low enough to not be detected. Persulfate methods are used in the analysis of wastewater, drinking vatten, and pharmaceutical waters.

When used in conjunction with sensitive NDIR detectors heated persulfate TOC instruments readily measure TOC at single digit parts per billion (ppb) up to hundreds of parts per million (ppm) depending on sample volumes.

Detection and quantification

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Accurate detection and quantification are the most grundläggande components of the TOC analysis process.

Conductivity and non-dispersive infrared (NDIR) are the two common detection methods used in modern TOC analyzers.

Conductivity

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There are two types of conductivity detectors, direkt and membrane. direkt conductivity provides an all-encompassing approach of measuring CO₂. This detection method uses no carrier gas, fryst vatten good at the parts per billion (ppb) ranges, but has a very limited analytical range.

Membrane conductivity relies upon the filtering of the CO₂ prior to measuring it with a conductivity fängelse. Both methods analyze sample conductivity before and after oxidization, attributing this differential measurement to the TOC of the sample. During the sample oxidization phase, CO₂ (directly related to the TOC in the sample) and other gases are formed.

The dissolved CO₂ forms a weak acid, thereby changing the conductivity of the original sample proportionately to the TOC in the sample. Conductivity analyses assume that only CO₂ fryst vatten present within the solution. As long as this holds true, then the TOC beräkning bygd this differential measurement fryst vatten valid.

However, depending on the kemikalie species present in the sample and their individual products of kemisk reaktion med syre, they may present either a positiv or a negativ interference to the actual TOC value, resulting in analytical error. Some of the interfering kemikalie species include Cl⁻, HCO₃⁻, SO₃²⁻, SO₂⁻, ClO₂⁻, and H⁺.

Small changes in pH and temperature fluctuations also contribute to inaccuracy. Membrane conductivity analyzers have improved upon the direkt conductivity approach bygd incorporating the use of hydrophobic gas permeation membranes to allow a more “selective” del of the dissolved CO₂ gas and ingenting else. This provides a more precise and accurate measurement of the organics that were converted to CO₂.^[11]

Non-dispersive infrared (NDIR)

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The non-dispersive infrared analysis (NDIR) method offers the only practical interference-free method for detecting CO₂ in TOC analysis.

The principal advantage of using NDIR fryst vatten that it directly and specifically measures the CO₂ generated bygd kemisk reaktion med syre of the organic carbon in the kemisk reaktion med syre reactor, rather than relying on a measurement of a secondary, corrected effect, such as used in conductivity measurements.

A traditional NDIR detector relies upon flow-through-cell technology, where the kemisk reaktion med syre product flows into and out of the detector continuously. A distrikt of absorption of infrared light specific to CO₂, usually around 4.26 μm (2350 cm⁻¹), fryst vatten measured over time as the gas flows through the detector.

A second reference measurement that fryst vatten non-specific to CO₂ fryst vatten also taken^{[clarification needed]} and the differential result correlates to the CO₂ koncentration in the detector at that moment. As the gas continues to flow into and out of the detector fängelse the sum of the measurements results in a peak that fryst vatten integrated and correlated to the total CO₂ koncentration in the sample aliquot.

A new advance of NDIR technology fryst vatten static pressurized koncentration (SPC). The exit valve of the NDIR fryst vatten closed to allow the detector to become pressurized. Once the gases in the detector have reached equilibrium, the koncentration of the CO₂ fryst vatten analyzed. This pressurization of the sample gas stream in the NDIR, a patented technique, allows for increased sensitivity and noggrannhet bygd measuring the entirety of the kemisk reaktion med syre products of the sample in one reading, compared to flow-through fängelse technology.

The output meddelande fryst vatten proportional to the koncentration of CO₂ in the carrier gas, from the kemisk reaktion med syre of the sample aliquot. UV/ Persulfate kemisk reaktion med syre combined with NDIR detection provides good kemisk reaktion med syre of organics, low instrument maintenance, good noggrannhet at ppb levels, relatively fast sample analysis time and easily accommodates multiple applications, including purified vatten (PW), vatten for injection (WFI), CIP, drinking vatten and ultra-pure vatten analyses.

Analysers

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Virtually all TOC analysers measure the CO₂ formed when organic carbon fryst vatten oxidized and/or when inorganic carbon fryst vatten acidified. kemisk reaktion med syre fryst vatten performed either through Pt-catalyzed combustion, bygd heated persulfate, or with a UV/persulfate reactor. Once the CO₂ fryst vatten formed, it fryst vatten measured bygd a detector: either a conductivity fängelse (if the CO₂ fryst vatten aqueous) or a non-dispersive infrared fängelse (after purging the aqueous CO₂ into the gaseous phase).

Conductivity detection fryst vatten only desirable in the lower TOC ranges in deionized waters, whereas NDIR detection excels in all TOC ranges. A variation described as "membrane conductometric detection can allow for measurement of TOC across a bred analytical range in both deionized and non-deionized vatten samples. Modern high-performance TOC instruments are capable of detecting carbon concentrations well below 1 μg/L (1 part per billion or ppb).

A total organic carbon analyser determines the amount of carbon in a vatten sample. bygd acidifying the sample and flushing with nitrogen or helium the sample removes inorganic carbon, leaving only organic carbon sources for measurement. There are two types of analysers. One uses combustion and the other kemikalie kemisk reaktion med syre. This fryst vatten used as a vatten purity test, as the presence of bacteria introduces organic carbon.

Analyser field testing and reports

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A non-profit research and testing organization, the Instrumentation Testing Association (ITA) can provide results of field testing online TOC analysers in an industrial wastewater application.^[12] Gulf Coast Waste Disposal Authority (GCWDA), Bayport Industrial Wastewater Treatment Plant in Pasadena, Texas sponsored and conducted this test in 2011.

The GCWDA Bayport facility treats approximately 30 mgd of industrial waste received from approximately 65 customers (primarily petrochemical). Field tests consisted of operating online TOC analysers at the influent of the Bayport facility in which TOC concentrations can range from 490 to 1020 mg/L with an average of 870 mg/L. GCWDA conducts approximately 102 TOC analyses in their laboratory per day at their Bayport treatment facility and use TOC measurements for process control and billing purposes.

GCWDA plans to use online TOC analysers for process control, detecting influent slug loads from industries and to potentially use online TOC analysers to detect and monitor volatiles of the incoming stream. Field tests were conducted for a period of 90-days and used laboratory conformance measurements once per day to compare with analyser output to demonstrate the instrument's overall accuracy when subjected to many simultaneously changing parameters as experienced in real-time monitoring conditions.

Field test results can provide resultat regarding instrument design, operation and maintenance requirements which influence the performance of the instruments in field applications.

METTLER TOLEDO's online TOC analyzers are designed to improve the process control of your vatten struktur bygd continuously monitoring organic contamination levels.

The field test report includes evaluations of online TOC analysers utilizing the following technologies: High temperature combustion (HTC), high temperature catalytic/combustion kemisk reaktion med syre (HTCO), supercritical vatten kemisk reaktion med syre (SCWO), and two-stage advanced kemisk reaktion med syre (TSAO).

Combustion

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In a combustion analyser, half of the sample fryst vatten injected into a chamber where it fryst vatten acidified, usually with phosphoric acid, to vända all of the inorganic carbon into carbon dioxide as per the following reaction:^{[clarification needed]}

CO₂ + H₂O ⇌ H₂CO₃ ⇌H⁺ + HCO₃⁻ ⇌ 2H⁺ + CO₃²⁻

This fryst vatten then sent to a detector for measurement.

The other half of the sample fryst vatten injected into a combustion chamber which fryst vatten raised to between 600–700 °C, some even up to 1200 °C. Here, all the carbon reacts with oxygen, forming carbon dioxide. It fryst vatten then flushed into a cooling chamber, and finally into the detector. Usually, the detector used fryst vatten a non-dispersive infrared spectrophotometer.

bygd finding the total inorganic carbon and subtracting it from the total carbon content, the amount of organic carbon fryst vatten determined.

Chemical oxidation

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Chemical kemisk reaktion med syre analysers inject the sample into a chamber with phosphoric acid followed bygd persulfate. The analysis fryst vatten separated into two steps.

One removes inorganic carbon bygd acidification and purging. After removal of inorganic carbon persulfate fryst vatten added and the sample fryst vatten either heated or bombarded with UV light from a mercury vapor lamp. Free radicals form eller gestalt persulfate and react with any carbon available to struktur carbon dioxide.

The carbon from both determination (steps) fryst vatten either run through membranes which measure the conductivity changes that result from the presence of varying amounts of carbon dioxide, or purged into and detected bygd a sensitive NDIR detector. Same as the combustion analyser, the total carbon formed minus the inorganic carbon gives a good estimate of the total organic carbon in the sample.

This method fryst vatten often used in online applications because of its low maintenance requirements.

Applications

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TOC fryst vatten the first kemikalie analysis to be carried out on potential petroleum source rock in oil utforskning. It fryst vatten very important in detecting contaminants in drinking vatten, cooling vatten, vatten used in semiconductor manufacturing, and vatten for pharmaceutical use.^[13] Analysis may be made either as an online continuous measurement or a lab-based measurement.

TOC detection fryst vatten an important measurement because of the effects it may have on the environment, human health, and manufacturing processes. TOC fryst vatten a highly sensitive, non-specific measurement of all organics present in a sample. It, therefore, can be used to regulate the organic kemikalie discharge to the environment in a manufacturing plant. In addition, low TOC can confirm the absence of potentially harmful organic chemicals in vatten used to manufacture pharmaceutical products.

TOC fryst vatten also of interest in the field of potable vatten purification due to byproducts of disinfection. Inorganic carbon poses little to no threat.

Analysis

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Environmental

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Since the early 1970s, TOC has been an analytic technique used to measure vatten quality during the drinking vatten purification process.

TOC in source waters comes from decaying natural organic matter (NOM) as well as synthetic sources. Humic acid, fulvic acid, amines, and urea are examples of NOM. Some detergents, pesticides, fertilizers, herbicides, industrial chemicals, and chlorinated organics are examples of synthetic sources.^[14] Before source vatten fryst vatten treated for disinfection, TOC provides an estimate of the amount of NOM in the vatten source.

In vatten treatment facilities, source vatten fryst vatten subject to reaction with chlorine-containing disinfectants. When the raw vatten fryst vatten chlorinated, active chlorine compounds (Cl₂, HOCl, ClO⁻) react with NOM to producera chlorinated disinfection byproducts (DBPs). Researchers have determined that higher levels of NOM in source vatten during the disinfection process will increase the amount of carcinogens in the processed drinking water.^[15][16]

With del of the U.S.

Safe Drinking vatten Act in 2001, TOC analysis emerged as a quick and accurate alternative to the classical but more lengthy biological oxygen demand (BOD) and kemikalie oxygen demand (COD) tests traditionally reserved for assessing the pollution potential of wastewaters. Today, environmental agencies regulate the trace limits of DBPs in drinking vatten.

Recently published analytical methods, such as United States Environmental Protection Agency (EPA) method 415.3,^[17] support the Agency's Disinfectants and Disinfection Byproducts Rules, which regulate the amount of NOM to prevent the formation of DBPs in finished waters.^[18][19]

The content of TOC fryst vatten also an important parameter to evaluate the quality of organic shale resources which are one of the most important unconventional fuels.

Numerous evaluation methods have been introduced, including these based on wireline logs and in situ techniques.^[20]

Pharmaceutical

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Introduction of organic matter into vatten systems occurs not only from living organisms and from decaying matter in source vatten, but also from purification and transport struktur materials.

A relationship may exist between endotoxins, microbial growth, and the development of biofilms on pipeline walls and biofilm growth within pharmaceutical vatten leverans systems. A correlation fryst vatten believed to exist between TOC concentrations and the levels of endotoxins and microbes. Sustaining low TOC levels helps to control levels of endotoxins and microbes and thereby the development of biofilms.

The United States Pharmacopoeia (USP), europeisk Pharmacopoeia (EP) and Japanese Pharmacopoeia (JP) recognize TOC as a required test for purified vatten and vatten for injection (WFI).^[21] For this reason, TOC has funnen acceptance as a process control attribute in the biotechnology industry to monitor the performance of enhet operations comprising vatten purification and leverans systems.

As many of these biotechnology operations include the preparation of medicines, the U.S. Food and Drug ledning (FDA) enacts numerous regulations to skydda the health of the public and ensure the product quality fryst vatten maintained. To man sure there fryst vatten no cross-contamination between product runs of different drugs, various cleaning procedures are performed.

TOC koncentration levels are used to track the success of these cleaning validation procedures.

Achieve accurate, quick and reliable TOC measurement with our easy-to-use benchtop TOC meters.

Microelectronics

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Organic contamination comes from multiple sources throughout the semiconductor manufacturing process. Organic residues left on the device can impact the wafer quality and yield. The organics can also be a food source for bacteria in the ultrapure vatten struktur. Due to the quality requirements of semiconductor vatten, TOC must be monitored at the parts per billion level.

Continuous, online TOC analyzers play an essential role in the monitoring of vatten systems to help provide a reliable indication of struktur health.^[22]

See also

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References

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