WO2002040991A2 - Calibration standards, methods, and kits for water determination by karl fischer titration - Google Patents
Calibration standards, methods, and kits for water determination by karl fischer titration Download PDFInfo
- Publication number
- WO2002040991A2 WO2002040991A2 PCT/US2001/027790 US0127790W WO0240991A2 WO 2002040991 A2 WO2002040991 A2 WO 2002040991A2 US 0127790 W US0127790 W US 0127790W WO 0240991 A2 WO0240991 A2 WO 0240991A2
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- WO
- WIPO (PCT)
- Prior art keywords
- reagent
- calibration standard
- karl fischer
- tablet
- component
- Prior art date
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N31/00—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods
- G01N31/16—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods using titration
- G01N31/168—Determining water content by using Karl Fischer reagent
Definitions
- This invention relates to improved calibration reagents for water determination using the Karl Fischer reaction. More particularly, the invention relates to a formed tablet calibration standard-reagent for calibrating Karl Fischer reactions for determining water content in a substance, said reagent containing a first component, namely sodium tartrate dihydrate, and a second component, namely magnesium stearate.
- Moisture measurement is valuable because the presence of water can adversely affect a variety of applications across multiple industries. Some examples include pharmaceutical drug stability; foodstuff storage quality; properties of oils (e.g. viscosity); and reduced chemical reaction yield (e.g. production of plastics). Moisture content determination is an evaluation criterion necessary for stability considerations of New Drug Applications. Accurate control and monitoring of moisture in these fields is often required by regulatory agencies and necessary to improve product quality. A number of chromatographic, spectroscopic, electronic, thermal, and wet chemical methods have been used in the past to determine moisture levels (S. K. MacLeod, Anal. Chem. , 1991, 63, 557A-565A) .
- the water to be determined reacts with iodine on a quantitative basis and consequently, the amount of reacted iodine is a measure of the amount of water present in the sample.
- the reaction proceeds according to the following expression:
- the titration can be run in either protic or aprotic medium, with the protic medium seeing wider use due to higher sensitivity of the titer to sample and solvent composition (M. S. Kamat, R. A. Lodder and P. P. DeLuca, Pharmaceutical Research, 1989 6(11) 961-965.).
- the reaction in protic media i.e., alcohol
- the iodine is generated electrically from iodine present in the cell.
- the electric efficiency of this method is generally 100%, and the amount of water in the sample is calculated from the number of moles of electrons used in the iodine generation.
- the components necessary to carry out this reaction have been formulated and are readily available as Karl Fischer reagents. These reagents are divided into two groups, single-component and two-component systems. In the single-component systems, all ingredients (iodine, buffer, S0 2 , and solvent) are in one solution. In the two- component systems, the "vessel" solution contains the buffer, S0 2 , and a solvent, while the "titrant" solution contains iodine in a suitable solvent.
- Karl Fisher reagents are used in several types of analysis .
- a volumetric analysis using a volumetric reagent determines moisture by measuring the volume of the Karl Fischer reagent consumed during the analysis.
- a coulometric analysis using a coulometric reagent generates iodine by passing a current through the reagent and determines the moisture from the amount of current.
- Examples of instrumentation utilizing the Karl Fisher reaction for determination of water content comprise: 1) Volumetric Moisture Meter, Model KF-100, Mitsubishi Chemical Corporation; 2) Aquastar® Volumetric Titrator, Models VlB and V-200, EM Science; 3) Schott Titroline KF, Schott; 4) Metrohm® Volumetric Karl Fischer Titration Systems, Models 701, 784, 758, 756, Brinkmann Instruments, Incorporated; 5) Orion® Volumetric Karl Fischer Titrators, Models TURB02TM and AF8, Thermo Orion, Incorporated; and 6) Mettler-Toledo Titrators, Models DL53, DL55, DL58, Mettler-Toledo Corporation.
- the quality of the analysis is checked against calibration standards containing known moisture content.
- the correct moisture content determination for the standards confirms that the Karl Fischer titration analysis is running properly, or indicates that a problem exists.
- a variety of materials have been proposed as standards for moisture content determinations. The principal requirements of these materials are 1) that they contain a stoichiometric amount of moisture that is stable over a wide range of temperature and humidity, 2) solubility in the Karl Fischer titration reagents, 3) ease of handling and storage, 4) availability, and 5) uniformity (M. S. Kamat, R. A. Lodder and P. P.
- Ammonium oxalate Citric acid, Ferric ammonium sulfate. Ferrous ammonium sulfate, Lactose, Oxalic acid, Potassium citrate, Potassium sodium tartrate, Potassium tartrate, sodium acetate, sodium bitartrate, sodium citrate, and sulfosalicylic acid (Neuss, J. D., Obrien, and M. G. , Frediani, H. A., Analytical Chemistry, 23, 1332 [1951]). Much effort has been given to making liquid water standard solutions less hygroscopic. These efforts have not been completely successful, as the water content of the solutions change after the septum over the solutions has been pierced several times.
- Water is a very good calibration reagent, but it is difficult to accurately dispense liquid water into the Karl Fischer titrator. When delivered by volume, the inaccuracies of the small amount delivered make it difficult to obtain an accurate value. A more accurate measurement is obtained when the liquid water is delivered by weight, but this again presents difficulties in dispensing the water into the titrator. Also, degradation and stability of the standard become relevant due to the special material handling characteristics that must be considered for certified liquid calibration media.
- weighing paper can be rolled to create a funnel, but this requires operator dexterity.
- the titrator is open to the atmosphere, and length of time the vessel is open is inversely related to the accuracy of the determination. Therefore, the prior art method using powder calibration standards requires significant analyst time and creates variability in assay results.
- Karl Fischer titrations were affected by: 1) sample transfer time, 2) relative humidity in the laboratory, and 3) material lost in the material transfer. These factors make it desirable to have an improved calibration standard reagent . Such an improved reagent would result in reduced time to load the reagent, provide for more accurate and quantitative transfer, and have less fluctuation in water content, as compared to the prior art liquid and powder calibration standards .
- a formed tablet calibration standard-reagent for calibrating Karl Fischer reactions for determining water content in a substance. It is another object of this invention to provide an improved process for the determination of water in a sample using the Karl Fischer reaction, in which the calibration reagent that is employed is a formed tablet calibration standard-reagent.
- Said formed tablet calibration standard-reagent containing a first component, namely sodium tartrate dihydrate, and a second component, namely magnesium stearate.
- a formed tablet calibration standard-reagent would fundamentally reduce variability in the Karl Fischer assay. Differences due to analyst technique would be minimized because standard addition is simplified and more consistent. Cumbersome use of a syringe and injection into the titration vessel would be replaced with a single hand transfer of the tablet to the vessel through the sample port. Titration methodology would remain the same in all other aspects with the exception of instrument calibration.
- a formed tablet calibration standard would remove the barriers posed by prior art standards which act to deter the automation of Karl Fischer determination of water content. An automated Karl Fischer assay employing a formed tablet calibration standard would dramatically increase productivity in Karl Fisher water determinations.
- the invention relates to a formed tablet calibration standard-reagent for calibrating Karl Fischer reactions for determining water content in a substance, said reagent containing a first component, namely sodium tartrate dihydrate, and a second component, namely magnesium stearate, where the ratio by percent weight of said first component to said second component is from 99.7:0.3 to 99:1.
- the invention further relates to a method for determining the water content of a substance using a Karl Fischer analysis wherein, the reaction is calibrated using a calibration standard, the improvement comprising using said formed tablet calibration standard-reagent.
- the invention further relates to a formed tablet calibration standard- reagent kit, comprising a sealed package containing said formed tablet calibration standard-reagent.
- Kear Fischer reaction refers to the chemical reaction described by equation (1) supra, and all of the embodiments of that reaction herein described including those that employ semi-automated instrumentation (described supra) .
- the tablets described herein for use in calibrating Karl Fischer reactions may be formed by the customary procedures in the art of tablet making.
- the ratio of said first component to said second component is from 99.7:0.3 to 99:1.
- the ratio is 99.6:0.4, 99.5:0.5, and 99.4:0.6.
- the ratio is 99.5:0.5.
- the tablet may have a total weight ranging from about 25 milligrams to 500 milligrams. Preferably, the total weight is from about 50 milligrams to 500 milligrams. Most preferably the total weight is about 200 milligrams.
- sodium tartrate dihydrate was selected for preparation of the formed tablet calibration standard- reagent . Bulk sodium tartrate is nearly 100% pure and stable for an extended duration, without special storage requirements. In addition, sodium tartrate has a known theoretical moisture content. These advantages are incorporated into the tablet because of the formulation process. After size exclusion of larger crystals, the tartrate is compressed to the desired weight. The weight of the tablet determines its water content.
- This target amount is determined based on the optimum operating range of the titrator being used. When the water content of the replicate under test falls within this range, the variability in the assay is reduced. Since operating ranges vary by manufacturer, range appropriate sized tablets can be developed for optimal results in a specific instrument type.
- magnesium stearate improved tablet robustness and eliminated capping.
- the development of tablet formulation included experimentation to assess compression and tablet hardness versus release of moisture in the Karl Fischer assay. Tablets were formulated with 0.25% magnesium stearate; however, tablet production failed. The lack of sufficient lubricant caused the press to seize during production. A preferred embodiment was determined to be tablet production with 0.5% magnesium stearate by weight. This will be explained in more detail by reference to the following examples, which are merely illustrative, and not limiting of the invention.
- Sodium tartrate, dihydrate ACS reagent grade was used as the starting material to make formed tablets . Crystals were sieved through a #30 mesh screen (Fisher Standard Testing Sieve, 600 micrometer opening) , and placed in a common container. Retained material was discarded. To promote formation of the tablet, magnesium stearate was added to the filtered crystals by sizing through the same screen, and adding the excipient to the mixture. The two components, sodium tartrate and magnesium stearate, were mixed at a ratio of 95.5:05 percent by weight for 30 minutes using a "tumble" style mixing apparatus to achieve homogeneity. The homogeneous mixture was then compressed into formed tablets using a common tablet press.
- a 7-millimeter round tool and die set was selected to form the tablets. Tablet production was carried out according to customary practices in the art. The tablets produced by this procedure were found to have an average thickness of 0.155-0.160 inches, and an average hardness of 1.3 KP.
- the resulting tablets were surprisingly well formed and durable. In previous attempts to form tablets without magnesium stearate, or with 0.25% magnesium stearate, the tablets were not well formed and could not be handled without degradation of the tablets.
- the hardness of the tablet is known in the art of tablet making to be important to the structural and functional characteristics of the tablet. Further, it is known in the art of tablet making that generally the greater the force that is applied to the materials to be formed, the greater the hardness of the resulting tablet.
- formation of the tablets of the present invention did not follow this relationship. Unexpectedly it was determined that the combination of sodium tartrate dehydrate with magnesium stearate in the ratio of 95.5:0.5 produced tablets of optimal hardness. Tablets formed of this ratio were subsequently determined in Karl Fisher water determination analysis to provide results that were closest to the theoretical water content of sodium tartrate dihydrate, and therefore are most preferable as a formed tablet calibration standard reagent.
- the tablets formed with 0.5% magnesium stearate could be handled and used in the methods of Karl Fisher water determination described herein without crumbling and without the losses of material to the environment or upon contact with transferring instruments such forceps or weighing boats.
- the compact and discrete nature of the tablets minimized the handling requirements by the analyst, which resulted in less time to execute the analysis.
- the formed tablet calibration standard reagent was superior to the use of powder or liquid standard reagents in that analyst time was not required to aliquot the standard, and in that the transfer process was discrete and expedient.
- the formed tablet calibration standard-reagents prepared with 95% sodium tartrate dihydrate and 5% magnesium stearate were analyzed by Karl Fischer analysis.
- a commercial titration apparatus was used for the assays (Orion® Volumetric Karl Fischer Titrators, Models TURB02TM) .
- Each moisture analysis was conducted according to the customary procedures for this instrument. Briefly, the instrument is standardized by accurately weighing by difference approximately 30 mg of a liquid standard, namely Hydranal® water standard 10.0. The aliquot was delivered into the titration vessel and titrated to the end point with Karl Fischer reagent according to customary procedures. The tablets of Example 1 were then analyzed and water content was determined by customary procedure for this instrument. The empirical values observed were within 5 percent of the theoretical water content calculated for the sodium tartrate dihydrate tablets .
- a preferred embodiment of the present invention pertains to the use of the formed tablet calibration standard-reagent for calibrating Karl Fischer wherein the Karl Fisher reaction employs the two-component reagent system described supra. Surprisingly, it was determined that the two-component system has a greater capacity for repeated analyses as compared to the one component system when using the formed tablet calibration standard-reagent.
- the invention further relates to a method for determining the water content of a substance using a Karl Fischer analysis, wherein the reaction is calibrated using a calibration standard, the improvement comprising using a formed tablet calibration standard-reagent .
- the formed tablet calibration standard-reagent is used to calibrate the Karl Fischer reaction for determining water content in test substances.
- the formed tablet calibration standard-reagent replaces the prior art calibration standard in the method of calibrating the Karl Fisher reaction and determining the water content of test samples.
- Use of the tablet provides several advantages over the prior art standards, including reducing the time and effort required of the analyst and reducing the time the reaction vessel is open to the environment.
- a formed tablet calibration standard-reagent removes the barriers posed by liquid and bulk-powder standards to complete automation of the assay. Material handling of samples in tablet form is easily manipulated by robotics.
- the formed tablet calibration standard-reagent simplifies the requirements for assay automation, and is particularly well suited for pharmaceutical applications where the samples for water content determination are often pills or tablets. This simplified automation strategy would replace repetitious, tedious, and variable manual determinations of moisture content.
- the invention further relates to a formed tablet calibration standard-reagent kit, comprising a sealed package containing said formed tablet calibration standard- reagent .
- a formed tablet calibration standard-reagent kit comprising a sealed package containing said formed tablet calibration standard- reagent .
- These new reagents can be employed in kits that are sold to users for the determination of water content.
- An example is a sealed package containing these new reagents, where the calibration tablet can be easily removed from the sealed package and introduced into the Karl-Fischer reaction vessel.
Abstract
Description
Claims
Priority Applications (5)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AU2002212966A AU2002212966A1 (en) | 2000-11-14 | 2001-11-01 | Calibration standards, methods, and kits for water determination by karl fischer titration |
JP2002542868A JP2004529316A (en) | 2000-11-14 | 2001-11-01 | Calibration standards, methods and kits for moisture determination |
US10/399,117 US7122376B2 (en) | 2001-11-01 | 2001-11-01 | Calibration standards, methods, and kits for water determination |
EP01981313A EP1356275A2 (en) | 2000-11-14 | 2001-11-01 | Calibration standards, methods, and kits for water determination by karl fischer titration |
US10/793,722 US7049146B2 (en) | 2000-11-14 | 2004-03-05 | Calibration standards, methods, and kits for water determination |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
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US24848700P | 2000-11-14 | 2000-11-14 | |
US60/248,487 | 2000-11-14 |
Related Child Applications (3)
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US10/399,117 A-371-Of-International US7122376B2 (en) | 2000-11-14 | 2001-11-01 | Calibration standards, methods, and kits for water determination |
US10399117 A-371-Of-International | 2001-11-01 | ||
US10/793,722 Continuation-In-Part US7049146B2 (en) | 2000-11-14 | 2004-03-05 | Calibration standards, methods, and kits for water determination |
Publications (2)
Publication Number | Publication Date |
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WO2002040991A2 true WO2002040991A2 (en) | 2002-05-23 |
WO2002040991A3 WO2002040991A3 (en) | 2003-08-28 |
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PCT/US2001/027790 WO2002040991A2 (en) | 2000-11-14 | 2001-11-01 | Calibration standards, methods, and kits for water determination by karl fischer titration |
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EP (1) | EP1356275A2 (en) |
JP (1) | JP2004529316A (en) |
AU (1) | AU2002212966A1 (en) |
WO (1) | WO2002040991A2 (en) |
Cited By (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP1413883A1 (en) * | 2002-10-21 | 2004-04-28 | Lifescan, Inc. | Method of reducing analysis time of endpoint-type reaction profiles |
WO2005017520A1 (en) * | 2003-08-08 | 2005-02-24 | Merck Patent Gmbh | Stable water standard |
US7049146B2 (en) | 2000-11-14 | 2006-05-23 | Facet Analytical Services And Technology, Llc | Calibration standards, methods, and kits for water determination |
US7122376B2 (en) | 2001-11-01 | 2006-10-17 | Facet Analytical Services And Technology, Llc | Calibration standards, methods, and kits for water determination |
CN100335898C (en) * | 2005-03-08 | 2007-09-05 | 张家港市国泰华荣化工新材料有限公司 | Method for measuring water content in C1-C8 low level primary amine |
CN102192971A (en) * | 2011-03-18 | 2011-09-21 | 辽宁省计量科学研究院 | Disintegration time limit testing standard substance and preparation method thereof |
CN110850024A (en) * | 2018-08-21 | 2020-02-28 | 中国计量科学研究院 | Water detection calibration system, detection model establishing method and water detection method |
Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0482465A2 (en) * | 1990-10-25 | 1992-04-29 | MERCK PATENT GmbH | Waterstandard |
US5340541A (en) * | 1993-03-05 | 1994-08-23 | Eli Lilly And Company | Automated Karl Fischer titration apparatus and method |
-
2001
- 2001-11-01 JP JP2002542868A patent/JP2004529316A/en not_active Withdrawn
- 2001-11-01 WO PCT/US2001/027790 patent/WO2002040991A2/en not_active Application Discontinuation
- 2001-11-01 EP EP01981313A patent/EP1356275A2/en not_active Withdrawn
- 2001-11-01 AU AU2002212966A patent/AU2002212966A1/en not_active Abandoned
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0482465A2 (en) * | 1990-10-25 | 1992-04-29 | MERCK PATENT GmbH | Waterstandard |
US5340541A (en) * | 1993-03-05 | 1994-08-23 | Eli Lilly And Company | Automated Karl Fischer titration apparatus and method |
Non-Patent Citations (3)
Title |
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BURGER A ET AL: "Polymorphism and preformulation studies of lifibrol" EUROPEAN JOURNAL OF PHARMACEUTICS AND BIOPHARMACEUTICS, ELSEVIER SCIENCE PUBLISHERS B.V., AMSTERDAM, NL, vol. 49, no. 1, 3 January 2000 (2000-01-03), pages 65-72, XP004257136 ISSN: 0939-6411 * |
NEUSS J D ET AL: "SODIUM TARTRATE DIHYDRATE AS A PRIMARY STANDARD FOR KARL FISCHER REAGENT" ANALYTICAL CHEMISTRY, AMERICAN CHEMICAL SOCIETY. COLUMBUS, US, vol. 23, 1951, pages 1332-1333, XP001042005 ISSN: 0003-2700 * |
OHM A: "Interaction of Bay t 3839 coprecipitates with insoluble excipients" EUROPEAN JOURNAL OF PHARMACEUTICS AND BIOPHARMACEUTICS, ELSEVIER SCIENCE PUBLISHERS B.V., AMSTERDAM, NL, vol. 49, no. 2, 1 March 2000 (2000-03-01), pages 183-189, XP004257154 ISSN: 0939-6411 * |
Cited By (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US7049146B2 (en) | 2000-11-14 | 2006-05-23 | Facet Analytical Services And Technology, Llc | Calibration standards, methods, and kits for water determination |
US7122376B2 (en) | 2001-11-01 | 2006-10-17 | Facet Analytical Services And Technology, Llc | Calibration standards, methods, and kits for water determination |
EP1413883A1 (en) * | 2002-10-21 | 2004-04-28 | Lifescan, Inc. | Method of reducing analysis time of endpoint-type reaction profiles |
US7118916B2 (en) | 2002-10-21 | 2006-10-10 | Lifescan, Inc. | Method of reducing analysis time of endpoint-type reaction profiles |
WO2005017520A1 (en) * | 2003-08-08 | 2005-02-24 | Merck Patent Gmbh | Stable water standard |
US7416894B2 (en) | 2003-08-08 | 2008-08-26 | Merck Patent Gmbh | Stable water standard |
CN100335898C (en) * | 2005-03-08 | 2007-09-05 | 张家港市国泰华荣化工新材料有限公司 | Method for measuring water content in C1-C8 low level primary amine |
CN102192971A (en) * | 2011-03-18 | 2011-09-21 | 辽宁省计量科学研究院 | Disintegration time limit testing standard substance and preparation method thereof |
CN110850024A (en) * | 2018-08-21 | 2020-02-28 | 中国计量科学研究院 | Water detection calibration system, detection model establishing method and water detection method |
CN110850024B (en) * | 2018-08-21 | 2021-11-09 | 中国计量科学研究院 | Water detection calibration system, detection model establishing method and water detection method |
Also Published As
Publication number | Publication date |
---|---|
WO2002040991A3 (en) | 2003-08-28 |
AU2002212966A1 (en) | 2002-05-27 |
JP2004529316A (en) | 2004-09-24 |
EP1356275A2 (en) | 2003-10-29 |
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