By Jon S. Kauffman PhD., Lancaster Laboratories

Size: px

Start display at page:

Download "By Jon S. Kauffman PhD., Lancaster Laboratories"

Daniel Murphy
6 years ago
Views:

2 Robust analytical TOC method validation is essential to the success of any online TOC system, particularly systems that release pharmaceutical-grade water in real time. Meeting USP 643 or EP specifications may not eliminate risk. By Jon S. Kauffman PhD., Lancaster Laboratories ost pharmaceutical companies in the United States and Europe use laboratory-based total organic carbon (TOC) analyzers to meet USP and EP compendial standards for release of water to manufacturing. Many companies are actively converting, or plan to convert to automated water-release systems using on-line TOC analyzers as the instrument of record. Their motivation is to improve quality and lower the costs of producing pharmaceutical-grade water. New FDA guidances [1,2] encourage the application of scientific and riskbased approaches to the development of automated process control systems in the pharmaceutical industry. The basis of a properly designed and qualified online TOC-based real-time release (RTR) system is to identify and understand critical process parameters. Steps required include assessing current knowledge and experience, evaluating the analytical capabilities of available analyzers and analyzing the system design for risks, costs and return on investment [3,4]. Some users of on-line TOC-based real-time water release systems have experienced problems related to on-line TOC results that do not correspond to laboratory-based TOC results, sometimes resulting in factory-wide dysfunction and associated costs. The earliest published report was from Collagen [5], but usually companies do not make these problems public [6]. The cause of these problems can usually be traced to the lack of a proper analytical method validation for the on-line TOC in the actual environment of use. This article will describe methods and criteria that may be useful for validating online TOC instrumentation. COMPARISON STUDY TEST PLAN There are multiple on-line TOC methodologies commercially available, but neither the USP nor the EP compendial TOC chapters reference any particular method. ICH Q7A indicates that on-line TOC methods should be validated and proven suitable under the actual conditions of the pharmaceutical application. The USP <643> and EP <2.2.44> TOC chapters suggest that simply passing the system suitability test is sufficient to qualify the TOC for use in pharmaceutical waters; the documents ICH Q7A, ICH Q2(R1), USP <1225> and the AAPS Qualification of Analytical Instruments clearly state otherwise [7,8,9]. By definition, a TOC analyzer measures all the covalently bonded organic carbon in solution. Ideally, the TOC should be tested on the organics present in the water, but they are usually not known. Therefore, it was decided to perform an analytical TOC validation of different on-line TOC methodologies. This involved adding known concentrations of compendial organics, as well as organics likely to be present in real-world situations, directly into pharmaceuticalgrade water. These controlled standard solutions were then directly introduced into different on-line TOC analyzers to determine their individual recoveries. APPARATUS AND TEST EQUIPMENT For the test we used an ultrapure water (UPW) system that produced low levels of TOC (< 5 ppb). The primary water purification system consisted of an activated carbon bed, water softener bed, singlestage reverse osmosis unit, ultra low organic removal bed, UV reactor operating at 184 nm and 254 nm wavelengths and a mixed ion-exchange bed. This make-up water was injected into a storage tank and then recirculated through a second, larger UV reactor and two larger mixed bed ion-exchange beds to the distribution loop, before going back into the main storage tank. There were multiple points of use connected to the main distribution loop, one of which was used for our testing station. Most pharmaceutical water systems use storage tanks that are vented to the air through microbial-blocking vent filters, thereby adding dissolved CO 2 and O 2 to the water. To our primary water sample drop stream, we added a commercially available hollow fiber membrane device [10] to introduce controlled levels of dissolved carbon dioxide and oxygen to simulate this situation. The dissolved CO 2 was used to vary the water conductivity at 25 C from μs/cm (deionized) to 1.2 μs/cm. This upper conductivity level matches the USP chapter <645> conductivity limit for Water for Injection (WFI) at 25 C. Since the inlet water was deionized and degassed, we used an online conductivity sensor [11] to indirectly measure the CO 2 level and an on-line dissolved oxygen (DO) sensor [12] to measure the DO of the water. The system used to add organics, accurately, to a water stream has been previously described [13]. It consists of a NIST-traceable turbine flowmeter [14] for measuring the water system flow rate, a syringe pump and injection tee. Organics were injected into the water stream from a syringe at micro-liter per minute flow rates. A computer monitored the turbine meter to dynamically control the syringe s injection rate of organic to achieve a fixed dilution ratio. With this system, we were able to introduce controlled organic compound concentrations into multiple on-line TOCs in the analyzer test manifold. From an errors

3 TABLE COMPOUNDS TESTED Compound Concentration Class Sucrose 500 ppbc Compendial (USP/EP) 1,4 Benzoquinone 500 ppbc Compendial (USP/EP) Nicotinamide 500 ppbc Difficult to oxidize Methanol 50 and 500 ppbc Simple Alcohol Isopropanol (IPA) 500 ppbc Simple Alcohol Acetic Acid 19 ppbc (0.3 μs/cm) Weak Organic Acid CHCl 3 and Sucrose 11 ppbc and 225 ppbc Weak Organic Acid Trimethylamine 65 ppbc Weak Organic Base Chloroform 11 ppbc Interference organic analysis, using the injection of a known concentration of NaCl with a precision conductivity measurement, we estimated that the injected organic standard concentration accuracy was within ±3% of the targeted concentration. TESTED ORGANIC COMPOUNDS Typical laboratory TOC analyzers oxidize all the covalently bonded organic carbon in solution to CO 2, and then measure the CO 2 as carbon mass per solution volume. Common units of measure are μg of carbon/liter or parts per billion as carbon (ppbc). In order to understand the performance of on-line TOC analyzers, organics were selected that are not completely definitive but may be considered to be indicators of actual performance. Besides TOC ppbc the compendial and difficult-to-oxidize organics, we wanted to use organics that were likely to be present in pharmaceutical water. Their actual presence depends on the initial contamination in the raw water, the water purification technologies, the correct operation of the technologies and the extent of the final water purity. To determine the organics that are likely to be present in purified pharmaceutical waters, we reviewed water purification organic removal articles [15-18, 23], as well as papers published by Dr. Stephan Huber, analyzing pharmaceuticalgrade waters using his TOC/liquid chromatographic analyzer [19-20]. Based on these references, we chose to test the organics and test concentrations listed in the Table (below). Chloroform is a disinfection by-product that is Figure 1. Typical Data from Organic Injection Run 0 12:14 12:43 13:12 13:40 14:09 14:38 15: ppbc Methanol-High DO-High IC DC/UV MC/UV-Persulfate DC/UV-Rapid MC/UV often poorly removed using typical pharmaceutical water purification systems. Additional detailed justifications for the selection of these compounds have previously been published [22]. If a TOC analyzer recovers all organics equally well in the actual conditions of use, then one could select the most difficult-to-oxidize compound and test its recovery at the compendial TOC limit. This would establish the ability of the TOC analyzer to measure all the TOC. However, it has been observed that the selection of the most difficult-to-oxidize organic compounds may depend on the TOC methodology, sample pre-treatment, oxidation system stability and water sample characteristics such as DO, ph and conductivity. A reagentless on-line TOC analyzer using only shortwave UV light will have difficultly oxidizing organics that are optically non-absorptive or that require a lot of oxygen in order to be completely oxidized. The latter factor also depends on the presence of enough available DO in solution to meet the stoichiometric requirements for complete oxidation to CO 2 [22]. TESTED ON-LINE TOC ANALYZERS We tested commercial versions of three reagentless on-line TOC analyz-

4 ers available for pharmaceutical use. The three analyzers used different TOC methodologies. The first methodology is direct conductometric detection (DC) with partial oxidation of the organics and is referred to as DC/UV-Rapid method. The DC/UV-Rapid analyzer responds very rapidly to organics in water. It is a reagentless online analyzer. The second methodology uses direct conductometric detection with complete oxidation and is referred to as the DC/UV method. The DC/UV analyzer, a reagentless online analyzer, has been used in the pharmaceutical industry since Two versions of the membrane-conductometric (MC) detector, both with complete oxidation methodology, also were evaluated. The membrane conductometric method separates the CO 2 from the post oxidation sample into a separate water chamber where the conductivity is measured. The first version is the reagentless membrane conductometric and UV-only oxidation system and is referred to as MC/UV method. This is also a reagentless online analyzer. The second version is the membrane conductometric and UV with acid and persulfate reagents and is referred to as MC/UV-Persulfate method. The MC/UV-Persulfate analyzer is reagent-based and configurable for either laboratory or online use. Both of these TOCs have been used on pharmaceutical waters since Before testing began, all tested analyzers were required to have factory-issued calibration certificates and new UV lamps installed. In addition, each analyzer had to have successfully passed the USP <643> TOC system suitability test. ORGANIC INJECTION TEST RESULTS Figure 1 shows the graphical results of the response from the four test analyzers for an injection of 500 ppb as carbon of methanol. This injection was done with the DO level greater than 4 ppm as O 2. This level provides enough DO to exceed the stoichiometric requirements for complete oxidation of the organic to CO 2 [22]. 300% 250% 200% 150% 100% 50% 0% -50% Figure 2. Response of the Different Analyzers in High DO 505 ppbc Sucrose 500 Benzoquinone 50 ppbc Methanol MC/UV-Persulfate MC/UV DC/UV DC/UV-Rapid The typical CO 2 level is about 70 ppb as carbon or about 0.3 μs/cm of conductivity. This is the case in water systems that have PW storage tanks that are vented to air. For each injection, the average of five consecutive measurements of the water system baseline was subtracted from five consecutive measurements from the center of the TOC peak. The percent recovery was then calculated from the known injection concentration. ORGANIC PERCENT RECOVERY RESULTS Figure 2 shows the percent recovery results for the test compounds on the different TOC analyzers. All the tested TOC instruments recovered 500 ppb of the USP and EP system suitability standards, sucrose and 1,4-benzoquinone, and all analyzers would have passed a USP and EP system suitability test. The response of the analyzers to the two alcohols showed good percent recovery for all TOC methods, except for the DC/UV-Rapid, which showed very low recovery at both concentrations of methanol. Methanol is one of the smallest and simplest organics. Additionally, the percent recovery is not the same for either methanol or iso-propanol (IPA), suggesting a possible non-linear response for these alcohols. Both DC/UV and DC/UV-Rapid 500 ppbc Methanol 500 ppbc IPA 19 ppbc Acetic Acid 65 ppbc TMA 499 Nicotinamide 11 CHCl 3 /225 Sucrose showed low recovery of the organic weak acids and bases. Both MC/UV and MC/UV-Persulfate methods correctly recovered the weak acid and base. Organic nitrogen compounds can be difficult-to-oxidize [24]. The difficultto-oxidize nicotinamide (vitamin B3) read correctly on the MC/UV and the MC/UV-Persulfate, low on the DC/UV-Rapid method, but high on the DC/UV method. As reported in the literature [5,24,25] both of the direct conductometric methods showed very high responses to chloroform. DC/UV-Rapid result was 136 ppbc and the DC/UV result was 346 ppbc to the 11 ppbc chloroform, as shown in Figures 2 and 3. It is believed the oxidation product of chloroform includes hydrochloric acid and with both the DC methods this additional conductivity increases the TOC result. This suggests a possible reason for the direct conductometric method false positive responses to chloroform. The response to the 11 ppbc chloroform for the membrane conductometric analyzers was 21 ppbc for the MC/UV and 11.7 ppbc for the MC/UV-Persulfate TOC. The 11 ppbc chloroform and 225 ppbc (total TOC of 236 ppbc) sucrose response from the DC/UV was 506 ppbc and the DC/UV-Rapid response was 313 ppbc. The MC/UV 3180% 1250% 11 ppbc CHCl 3

TOC ppbc 600 500 400 300 200 100 response was 274 ppbc and the MC/UV- Persulfate response was 261 ppbc to the expected 236 ppbc injection.

5 TOC ppbc response was 274 ppbc and the MC/UV- Persulfate response was 261 ppbc to the expected 236 ppbc injection. Further research is needed to determine why false positive readings occur with some online TOC analyzers as observed with chloroform, since this problem may result in unnecessary out of specification issues for drug manufacturers. Our results also suggest that false negative readings with weak organic acids and bases warrant further investigation, since under reporting the real TOC value is a possible regulatory issue. It is important to note that the tested commercial online TOC systems all meet current USP release specifications. Given the variability of water sources and pharmaceutical water purification systems, it will be useful to evaluate these TOC technologies thoroughly in combination with the likely organic contamination in the water. These evaluations will ensure their suitability for use in online real-time release of water systems, and minimize potential risks. The USP <643> and EP suggest that 1,4 benzoquinone is difficult to oxidize, and that any TOC analyzer passing the benzoquinone-based system suitability test is suitable for use on pharmaceutical-grade water, but our testing suggests this may not be the case. It is interesting to note that the 2006 Japanese Pharmacopeia (JP) 15 0 does not completely harmonize with the USP<643> TOC or EP<2.2.44> TOC chapters, and our research, so far supports the conclusion of JP15, which states: If the apparatus conforms to the apparatus suitability test requirements described in General Chapter <643> Total Organic Carbon of the United States Pharmacopeia (USP28, 2005), otherwise described in Methods of Analysis Total Organic Carbon in Water for Pharmaceutical Use of the European Pharmacopoeia (EP 5.0, 2005), the apparatus may be used for monitoring a pharmaceutical water system, provided that water of high purity is used as feed water. A TOC apparatus, characterized by calculating the amount of organic carbon from the difference in conductivity before and after the decomposition of organic substances without separating carbon dioxide from the sample solution, may be influenced negatively or positively, when applied to a sample solution containing ionic organic substances or organic substances comprised of nitrogen, sulfur, or halogens such as chlorine and the like; therefore, the apparatus should be selected appropriately depending on the purity of pharmaceutical water to be measured and on the contamination risk upon apparatus failure [26]. In summary, this says the water must be Figure 3. Chloroform and Sucrose TOC Response ChCl ppbc TOC=10.9 ppbc ChCl ppbc + Sucrose 225 ppbc TOC=236 ppbc MC/UV-Persulfate MC/UV DC/UV DC/UV-Rapid of sufficient purity to use the described TOC apparatus. This description matches that of the direct conductometric TOC method. References 1. Final Report, Pharmaceutical CGMPs for the 21st Century A Risk-Based Approach, September 2004, gmp2004/gmp_finalreport2004.htm. 2. Guidance for Industry, PAT A Framework for Innovative Pharmaceutical Development, Manufacturing, and Quality Assurance, September 2004, guidance/6419fnl.htm. 3. Godec, R., Cohen, N., Automated Release of Water Using On-Line TOC Analysis and FDA Risk-Based cgmp, Inspection, and PAT Principles, Pharmaceutical Engineering, Jan/Feb Martinez, J. E., On-line TOC Analyzers Are Underused PAT Tools, BioProcess International, December McCurdy, Implementing TOC Testing for USP 23- A Case Study, Pharmaceutical Engineering, Nov/Dec Communication with Chris Heiss, CEO of Pharmaceutical Water Inc., 2850 N. El Paso Street, Colorado Springs, CO 80907, (719) , ch@pharmaceuticalwater.com. 7. From the FDA web site see section XII sub-section H at fnl.pdf or section 12.8 of Q7A from the ICH web site: DIA433.pdf. 8. From the FDA web site guidance/1320fnl.pdf and from the ICH web site 9. AAPS web site location or AAPS PharmaSciTech 2004; Volume 5, issue 1, Article 22 ( 10. Membrana Liqui-Cel web site: liqui-cel.com and 2.5 x 8 membrane contactor specification sheet com/uploads/documents/d59_2.5x8extra- Flow_Rev12_ pdf. 11. Mettler Toledo Thornton web page thorntoninc.com/770max.htm. 12. Swan Analytical Instruments AG Trace Oxygen Monitor with Faraday Verification SOLO Oxytrace web page: highpuritywater/oxygen.

13. Godec, R., The Performance Comparison of Ultrapure Water TOC Analyzers using an Automated Standard Addition Apparatus. Semiconductor Pure Water and Chemicals Conference, pp. 61-112, 2000. 14.

6 13. Godec, R., The Performance Comparison of Ultrapure Water TOC Analyzers using an Automated Standard Addition Apparatus. Semiconductor Pure Water and Chemicals Conference, pp , Flow Technology, Inc. turbine flow meter web page: Gottlieb, M., Meyers, P. The Production of Ultra Low TOC Resins. Semiconductor Pure Water and Chemicals Conference, pp , Pate, KT; DI Water Resistivity versus Trace Ion Levels. Ultrapure Water, pp , Vol. 8, No. 1, Jan./Feb., Mizuniwa, T, Kitami, K, Ito,M, Miwa,R. Analysis of Organic-combined Chloride, Sulfate and Nitrate Ions in Ultrapure Water. Semiconductor Pure Water and Chemicals Conference, pp , Governal, RA, Shadman, F. Design of High- Purity Water Plants: Fundamental Interactions in Removal of Organic Contamination. Ultrapure Water, Sep, Woiwode, W, Huber, S; Differnzierende TOC- Bestimmung zur Charakterisierung von Reinstwasser und Ruckstandsprufung im Verlauf der Reinigungsvalidierung ; Pharm. Ind. 62, 5, (2000). 20. Huber, S., DOC-Labor web site: doc-labor.de/ and click on USA Flag for English, click on applications, select pharmaceutical or mixed bed filters or Reverse Osmosis or Anion filter or Resin Examination or Cation Filter 21. Huber, S; personal communication showing an example of Chromatographic-TOC analysis of pharmaceutical water. 22. A Science Based Performance Comparison of On-Line TOC Analyzers at Emery, A.P., Girard JE, Jandik P; Investigation of Pure Water Contaminants Stemming From Ion Exchange Materials, Ultrapure Water, Oct Rydzewski, J., Identification of a Critical UPW Contaminant by Applying an Understanding of Different TOC Measuring Technologies, UPW Watertech Conference Proceedings, Portland, Oregon, Chu, Theresa; Trihalomethanes Can Cause RO/DI System Problems, Semiconductor Pure Water Conference, Japanese Pharmacopeia 15, page 1602, section Monitoring with an Indicator of Total Organic Carbon (TOC). About the Author Dr. Jon S. Kauffman is the Director of Method Development & Validation and Biopharmaceutical Sciences at Lancaster Laboratories. He earned a B.S. in Chemistry from Millersville University; a Ph.D. in Chemistry from University of Delaware; and has been with Lancaster Laboratories since His areas of expertise include mass spectrometry, chromatography, impurities testing, extractables and leachables testing, dissolution testing, method validation and biochemistry. He can be contacted at Lancaster Laboratories, 2425 New Holland Pike, P.O. Box 12425, Lancaster, PA , (717) Ext. 1377, ( Excerpted with permission from Pharmaceutical Manufacturing, November/December PUTMAN. All Rights Reserved. On the Web at

RELIABILITY OF TOC RESULTS IN ULTRAPURE WATER ANALYSIS

Tech Notes: 030101 RELIABILITY OF TOC RESULTS IN ULTRAPURE WATER ANALYSIS The intent of this technical note is to discuss current methods of TOC (Total Organic Carbon) analysis, including their advantages