Model 1030 TOC Analzyers - xylem-analytics.asia · Total organic carbon \⠀吀伀䌀尩 is often...
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JOHN WELSH, Ph.D. TOC PRODUCT MANAGER July 2018 A New Approach to High Salt Samples and TOC Analysis
Transcript of Model 1030 TOC Analzyers - xylem-analytics.asia · Total organic carbon \⠀吀伀䌀尩 is often...
JOHN WELSH, Ph.D.TOC PRODUCT MANAGER
July 2018
A New Approach to High Salt Samples and TOC Analysis
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Welcome to our webinar, A New Approach for High Salt Samples and TOC Analysis. This is the third webinar in a three-part series of webinars that I have presented this year. The first two webinars are available on the OI Analytical website: www.oico.com. Now, sit back, relax, and let’s not worry about those high salt samples!
Topics
• Importance of TOC• TOC Techniques• The Effects of Salt in Combustion TOC• Approaches to dealing with salt in Combustion
TOC
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In today’s webinar I will be covering the approach that OI Analytical employs for the determination of TOC on our Model 1080 TOC. I will touch on the importance of TOC, different TOC techniques, the effects of salt in TOC determination, and techniques that are used to mitigate the effects of salt.
Importance of TOC
Total organic carbon (TOC) is often used as a non-specific indicator of water quality. In the natural process of our environment and the man-made processes of industry the ubiquitous nature of carbon provides a screening tool to determine the status of water quality.TOC systems can determine contamination from natural occurring compounds, man-made compounds, viruses, bacteria or biological growth.
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The importance of TOC, as a water quality parameter, cannot be understated. Generally speaking, when we think of contamination in water, that contamination is comprise of carbon-containing compounds. This is true for all applications: ultra-pure water for microelectronics fabrication, boiler feed or process water, water for injection and clean-in-place validation in the pharmaceutical industry, drinking water and waste water.
Importance of TOC
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• Compliance Monitoring• Environmental (EPA)• Contract Laboratories• Municipalities
• Safety (FDA)•Pharmaceutical (Cleaning Validation)• Food
• Process Monitoring•Chemical & Petrochemical•Power•Semi-conductor •Pharmaceutical (WFI)
Non-specific detection of organics, provides general screening and acceptance criteria for various applications and processes.
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Total organic carbon (TOC) is often used as a non-specific indicator of water quality. In the natural process of our environment and the man-made processes of industry the ubiquitous nature of carbon provides a screening tool to determine the status of water quality. TOC systems can determine contamination from natural occurring compounds, man-made compounds, viruses, bacteria or biological growth. TOC determination provides quick and easy indication of organic contamination. It can be used as a general screening tool and indicate if predetermined acceptance criteria are met for wide variety of applications and processes. As we will see in the History of TOC, the need for Total Organic Carbon analysis grew out of the need to monitor seawater. Today, TOC is used for compliance monitoring to protect water quality and establish criteria for screening and measuring contaminant levels. TOC is used by Service Contract Laboratories and municipalities for the analysis of a wide variety of samples. The Unites States Pharmacopoeia (USP), European Pharmacopoeia (EP) and Japanese Pharmacopoeia (JP) all mandate TOC analysis as a required test. In emerging markets, such as Southeast Asia and China, these practices are being adopted. For process control, a pre-determined level of TOC has been defined whether that be wastewater effluent from a chemical or petrochemical plant, or ultra-pure water for injection in the pharmaceutical industry. In those applications, TOC determination provides valuable insight into the proper function of the process.
Oxidation Techniques
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プレゼンター
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I will cover the oxidation techniques that give name to the TOC analyzers that are available today.
Oxidation Techniques
• High Temperature Catalytic Oxidation
• Heated Persulfate with NDIR Detection
• UV Persulfate• NDIR Detection• Direct Conductivity or Membrane Conductivity
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プレゼンター
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So, today we have three, primary methods for the determination of TOC in the laboratory: High Temperature Catalytic Oxidation, Heated Persulfate with NDIR Detection, and UV Persulfate with either NDIR Detection or Conductivity/Membrane Conductivity Detection.
HTCO TOC
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In this seminar, I will concentrate on combustion TOC as it is one of the most widely used techniques for the determination of TOC for samples with high-salt content.
Characteristics of Combustion TOC
• Combustion is preferential to organic carbon that contains suspended materials.
• The major limitation to the combustion technique is the magnitude and variability of the blank.
• Minimum detection concentration is 1 ppm C or less, though 1 ppm C is highly recommended.
• The high temperature techniques accumulate non-volatile residues in the analyzer; however, the 680 °C technique minimized the fusion of dissolve salts.
• Can use phosphoric or sulfuric acid for acidification.
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プレゼンター
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Standard Method 5310B offers pertinent information on the combustion TOC technique. While this is not a complete listing of all of the recommendations, these are the most salient points about this technique. In general, the combustion TOC technique is applicable when the TOC concentration is above 1 ppm. While the method does offer the choice between phosphoric and sulfuric acid, I contend that sulfuric should not be used as this is a potential poison to precious metal catalysts.
Current Instrumentation
• Operate at 680 °C
• NDIR detection
• Platinum catalyst
• Quartz tube and packing
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The combustion tube on the left represents a design that can be found in most HTCO systems on the market today. The combustion tube on the right is unique to the Model 1030C for OI Analytical. The principle of the technique is very straightforward. A small aliquot of sample is injected onto a catalyst substrate in a combustion tube that is held at 680 to 950 C. This temperature can be higher in some instruments that do not use catalysts. The advantage of using lower temperatures (680 C) is that fusion of dissolved salts is minimized. I’ll be covering the topic of analysis of salt-containing samples by HTCO in the 26 July webinar. Since its’ inception not much has changed with HTCO systems over the years. However, I will present concepts developed in the OI Analytical Model 1080 TOC that are truly unique to the HTCO technique.
Quartz Glass
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• Fused quartz is glass consisting of silica in amorphous (non-crystalline) form.
• The optical and thermal properties of fused quartz are superior to those of other types of glass due to its purity.
• Quartz glassware is occasionally used in chemistry laboratories when standard borosilicate glass cannot withstand high temperatures or when high UV transmission is required.
• Quartz glass is always used in the construction of combustion tubes in HTCO TOC instruments.
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Read the slide.
Quartz Glass and Salt
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• Salt is the most difficult sample matrix for any TOC technique.
• This is particularly true for the combustion technique.
• Most likely, a sodium ion displaces a silicon ion and leads to devitrification of the quartz glass.
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Salt containing samples are the most difficult matrix for any TOC technique. This is particularly true for the combustion TOC technique. Aside from deposition on the catalyst, and other packing material, salt leads to the devitrification of the tube itself.
Quartz Glass
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• Vitrification
• (From Latin vitreum) is the transformation of a substance into a glass.
• Vitrification is usually achieved by heating materials until they liquidize, then cooling the liquid, often rapidly, so that it passes through the glass transition to form a vitrified solid.
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Glass is produced through the process of vitrification. A crystal, such as quartz, is transformed into an amorphous solid that we commonly refer to as glass.
Quartz Glass
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• Devitrification
• Causes of devitrification, commonly referred to as "devit", can include holding a high temperature for too long, which causes the nucleation of crystals. The presence of foreign residue such as dust on the surface of the glass or inside the kiln prior to firing can provide nucleation points where crystals can propagate easily. The chemical compositions of some types of glass can make them more vulnerable to devitrification than others, for example a high lime content can be factor in inducing this condition. In general opaque glass can devit easily as crystals are present in the glass to give its opaque appearance and thus the higher the chance it might devit.
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As one might expect, the reverse process of vitrification can occur under the appropriate conditions. For quartz glass, the process of devitrification occurs when quartz is exposed to salt-containing liquid at high temperatures. The combination of heat and salt lead to devitrification. The process is accelerated if either salt concentration, or temperature is increased.
Devitrification of Quartz
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The picture on the left is a combustion tube from one our modules that is used for TOC determination of solid samples. This picture was taken after analysis of beach sand samples. The picture on the right is a close-up view of the center section. This is not just the deposition of salt on the surface of the combustion tube. Rather, notice that the glassy surface of the quartz tube has actually started to crystallize. Eventually, this tube would lose its’ structure and collapse under its’ own weight.
How to Deal with Salt?
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Sulfuric Acid• It is thought that the higher boiling point fo sulfuric acid will keep the salt
in solution longer; thereby, preventing accumulation in the combustion tube
Salt Traps• Quartz wool captures the salt, so that it can be removed from the
sample before it reaches the catalyst
Rinsing• Water, and/or acid is routinely used to wash residue from the tube and
surface of the catalyst
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It is thought that the potassium salts of sulfuric acid, with the higher melting point than NaCl, have a positive effect on the lifetime of the combustion tube. Salt traps will ultimately clog and must be replaced. Rinsing with water, or acid, will definitely have a positive effect on the combustion tube and catalyst.
How to Deal with Salt?
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• Ceramic Combustion Tubes/Components• In some designs, special combustion tubes, valves, and injector
surfaces can be manufactured from ceramic, or ceramics, that will not suffer from devitrification like quartz.
• Special Salt Kits• Add on components that intend to mitigate the effects of salt.
• Catalyst Regeneration• It has been demonstrated that the catalyst can be removed,
reconditioned with hydrochloric acid and returned to the combustion tube.
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Ceramic tubes, while effective, can be rather expensive and will eventually require replacement. Kits using combustion tubes of a special geometry and packing scheme have been used in some instances. Some practitioners remove the catalyst, recondition with hydrochloric acid and return the catalyst to the combustion tube. While this may restore the catalyst, the devitrification of the combustion tube, itself, can still occur.
Catalyst Poisoning
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• Catalyst poisoning refers to the partial or total deactivation of a catalyst. Poisoning is caused by chemical compounds. Although usually undesirable, poisoning may be helpful when it results in improved selectivity.
• Poisoning often involves compounds that bond chemically to the active surface sites of a catalyst. Poisoning decreases the number of catalytic sites or the fraction of the total surface area that has the capability of promoting reaction always decreases, and the average distance that a reactant molecule must diffuse through the pore structure before undergoing reaction may increase. Poisoned sites can no longer accelerate the reaction with which the catalyst was supposed to catalyze.
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The conversion of carbon containing compounds to carbon dioxide occurs on the surface of a precious metal catalyst in the presence of oxygen. If the actives sites of the catalyst are not available, then no reaction occurs. Atoms, such as sulfur atoms, bond easily on the surface of a catalyst; thereby, preventing the reaction. This is one of the reasons why I believe that sulfuric acid is not desirable in combustion TOC.
• Reduce maintenance costs and simplify maintenance procedures
o A combustion tube, at some point in time, will require either a catalyst repacking, or complete replacement
o The frequency of this maintenance operation is dependent on several factors; such as, sample matrix, sample throughput and combustion tube design
Challenges with the HCTO Technique
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There are challenges associated with the HTCO technique that are not found in the other techniques by virtue of the fact that a combustion tube, operating at high temperature, is employed in the analysis. At some point, maintenance action of some form must be carried out on the combustion tube. This is generally confined to replacement of the catalyst; however, in some cases complete replacement of the combustion tube may be required. This is particularly true for the analysis of salt-containing samples.
Addressing the Challenges of Salt Samples
• Smart Slide injector design
• Catalyst Guard - furnace tube insert design
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プレゼンター
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The model 1080 TOC incorporates unique design features that help to mitigate the challenges that are faced in the determination of TOC in salt-containing samples. These design features include: the Smart Slide injector and Catalyst Guard.
Smart Slide Sample Injector
• Uses “ramps” in the slide to reduce friction while sliding
Ramps Clip
Shown in Sample Inject position
Actuator Attachment
• Feasibility testing completed during development• Increases lifetime of sealing O-ring from 30 days to 15 months• Lifetime of slide is 18 to 24 months
• Off-the-shelf actuator simplifies design; reduces labor; increases reliability
• Quick-disconnect linkage to detach actuator from cap
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プレゼンター
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The Model 1080 combustion tube cap uses “ramps” in the slide to reduce friction while sliding across the sealing surfaces. In our feasibility testing completed during development, this feature increases the lifetime of sealing O-ring from 30 days to 15 months. The anticipated lifetime of slide is 18 to 24 months. An off-the-shelf actuator simplifies design; reduces labor; increases reliability. A quick-disconnect linkage detaches the actuator from cap for easier maintenance.
Catalyst Guard Design
• New Catalyst Guard Design
• Uses small sacrificial tube to protect the main tube and catalyst.
• Decreases cost and frequency of replacing catalyst and tube.
• Reduces startup time after servicing just the guard tube.
• Feasibility testing- Tested with high salt/particulate samples- Verified cleaning/maintenance- Quantified “extended life” of catalyst
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プレゼンター
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A small, sacrificial tube is used to protect the main tube and catalyst. This simple feature decreases the frequency of replacing the catalyst and combustion tube. In our feasibility testing, this feature was tested with high salt/particulate samples.
Catalyst Guard Testing
• Catalyst Guard• Task: Test guard tube with High Salt samples (i.e. 3% NaCl
seawater simulation)• Goal: Meet or exceed the capability of the current OI Analytical
Model 1030C.
• Results:• 1080 High Salt test ran for over 4700 injections over 3+ weeks
without failure of the main combustion tube• Catalyst Guard tube definitely helped to extend the life of the main tube.
The main tube was reusable.• As expected, the Guard Tube was not reusable.• For comparison, an OI 1030C TOC was also tested and only ran for 200
reps before the injector clogged.
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プレゼンター
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The guard tube was tested using a 3% NaCl solution. The Model 1080 ran for over 4700 injections without failure of the main combustion tube or catalyst. As expected, the guard tube was not reusable; however, it could be replaced and operation of the instrument continued. For those of you familiar with the OI Model 1030C Combustion TOC and the combustion tube previously shown, that combustion tube clogged after 200 injections under the same conditions.
Catalyst Guard Testing
Pictures before and after 4700 injections of 40uL of 3% NaCl
(Before) (After)23
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This is a picture of the Catalyst Guard tube after the high salt test. Clearly, it shows that the tube did its’ job in taking the brunt of punishment from the salt-containing samples.
Case Study: High Salt Samples
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プレゼンター
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Now, I want to cover the Fundamentals of TOC Analysis
Case Study: High Salt Containing Samples
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• Samples with unknown TOC concentration were received from a customer for analysis.
• Salt content was reported to be in the range of 3 - 30%. However, the exact salt content for each sample was not known prior to analysis.
• It was thought that the TOC concentration would be in the range of zero to 10 – ppm.
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Samples with unknown TOC concentration were received from a customer for analysis. Salt content was reported to be in the range of 3 - 30%. It was thought that the TOC concentration would be in the range of zero to 10 – ppm.
Method Settings – Low Range
Setting ValueAnalysis Mode NPOC (Non-purgeable Organic Carbon)Sparging InternalSample Volume 500 μLAcid Volume 100 µLFurnace Temperature 680°CSample Sparge Time 1 minuteReaction Time 1 minuteDetection Time 3 minutes (max)Number of Replicates 3 No outlier removal
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プレゼンター
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Typical settings for a 0 – 10 ppm calibration curve. The samples were analyzed in NPOC mode. Sample and acid were added to the NPOC chamber and the TIC fraction sparged from the sample prior to TOC determination. Note the addition of a Reaction Time for the Model 1080. The Model 1080 uses a Stop Flow/Bypass injection scheme in which the sample is allowed time to react in the combustion tube. Sparge time can be kept to 1 minute since the sparge flow rate is 300 ml/min.
Initial Findings
• It was anticipated that the TOC concentration in this batch of samples would be in the single-digit range.
• The instrument was calibrated for 0 – 10 ppm.
• Most samples were in that range; however, two samples fell outside of the range.
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プレゼンター
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It was anticipated that the TOC concentration in this batch of samples would be in the single-digit range. The instrument was calibrated for 0 – 10 ppm. Most samples were in that range; however, two samples fell outside of the range.
Low Range Salt Sample Results
Check Standard/Sample Result (mg/L) RSDInstrument Blank 0.00 7.5240121 3.08 1.6840122 4.48 1.2040123 6.54 1.3940124 5.34 2.10
40125 12.30 1.78
40126 84.24* 1.19
Blank 1.23* 0.32
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プレゼンター
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These are the results from the analysis of unknown samples using the low-range calibration. Note that the last sample is almost a factor of ten higher than the highest point in the calibration curve. This result was unexpected, so the instrument was recalibrated in the range of 0 – 100 ppm and the samples reanalyzed to include this high concentration sample. The blank at the end of the sequence was high, but this could be expected since the instrument parameters were not optimal for high range samples.
Method Settings – High Range
Setting ValueAnalysis Mode NPOC (Non-purgeable Organic Carbon)Sparging InternalSample Volume 200 μLAcid Volume 100 µLFurnace Temperature 680°CSample Sparge Time 1 minuteReaction Time 1 minuteDetection Time 3 minutes (max)Number of Replicates 3 No outlier removal
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プレゼンター
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Adjustments to the instrument method were made to accommodate the unexpected high-range sample. The instrument was recalibrated in the range of 0-100 ppm and the samples were reanalyzed under these new conditions.
High Range Calibration Curve
R-Squared: 0.9996
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0
5000
10000
15000
20000
25000
0 20 40 60 80 100 120
Are
a C
ount
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Concentration (ppm)
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The calibration curve from the high range calibration. All standards were matrix-matched to the anticipated salt concentration. Each calibration point was analyzed in triplicate with no outlier removal.
Calibration Curve for Salt Samples
Calibration Standard RSD ValueReagent Water (Zero ppm) 3.871-ppm 0.9510-ppm 0.6325-ppm 0.7850-ppm 1.03100-ppm 0.09R-Squared Value 0.9998
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プレゼンター
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Results from the calibration curve shown in the previous slide. It is noteworthy to point out that these results were obtained without the use of outlier removal. That is, these are the results from three, consecutive injections of standard at each calibration point.
Low Range Salt Sample Results – HR Cal
Check Standard/Sample Result (mg/L) RSDInstrument Blank 0.0010-ppm Check Standard 10.66 0.29100-ppm Check Standard 98.65 0.2440121 3.42 1.0240122 5.46 1.5440123 7.55 1.7540124 5.64 1.54
40125 13.01 2.46
40126 93.80 0.50
Blank 0.278 11.87
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プレゼンター
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These are the results from the analysis of unknown samples using the high-range calibration. Check standards were inserted into the sequence at 10-ppm and 100-ppm. In almost all cases, the results in this calibration range were within 10-percent of the low range calibration results and the error of measurement. The sample, 40126, was nearly 100-ppm. Now that the method was optimized for this range, the blank at the end the sequence was well below the Reporting Limit for this type of sample analysis.
Summary
• Samples with high-salt loads generally are a problem for TOC determination.
• Salt can lead to devitrification of the quartz combustion tube and deposition on the catalyst.
• Approaches taken for the mitigation of the effects of salt can be expensive or lead to negative effects on the catalyst.
• A simple, easy to use approach is employed by the Model 1080 TOC.
• The Model 1080 approach should result in decreased cost of ownership, downtime, and increase the mean time between maintenance activities.
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Read the summary.
Q & A
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