Stability Testing Protocol Research Articles

Diclofenac sodium loaded liposomal gel for transdermal delivery: Formulation, characterisation and pharmacokinetic evaluation

The transdermal route of drug delivery has many advantages for drug administration in local and systemic therapy. But, skin is widely recognized for its effective barrier properties compared to other biological membranes. The low permeability of the skin makes it a minor port of entry for drugs. The vesicular drug delivery is thus potentially beneficial as vesicles tend to fuse and adhere to the cell surface; this is believed to increase the thermodynamic activity of the drug at stratum corneum interface thus leading to enhanced permeation rate. These vesicles can act as drug reservoirs and modification of their composition or surface can adjust the drug release rate and/or the affinity of the target site. Among different carriers like liposomes, niosomes, ethosomes and transferosomes, represent a promising drug delivery module. The current research Aims to develop diclofenac sodium loaded liposomal gel for effective transdermal delivery. Diclofenac sodium is a highly lipophilic non-steroidal anti-inflammatory drug. The Aim of the present study is to formulate and optimize Diclofenac sodium loaded liposomes by film hydration technique using HSPC as the lipid base and cholesterol as the stabilizer and then to carry out drug and excipient interaction studies (using DSC and FTIR) and pharmacokinetic evaluation of selected products on male Wistar rats and to evaluate the stability of the selected products as per suitable stability testing protocol following ICH guidelines.

Investigation of activity and stability of carbon supported oxynitrides with ultra-low Pt concentration as ORR catalyst for PEM fuel cells

In this study, a carbon supported oxynitrides catalyst with ultra-low Pt concentration (2wt%, Pt-ON/C) is synthesized from Co(NO3)2⋅6H2O, (NH4)6Mo7O24⋅4H2O and PtCl4 precursors by using NH3 as reducing agent and nitrogen source. It is investigated as oxygen reduction reaction (ORR) catalysts for proton exchange membrane (PEM) fuel cells and compared to conventional 2wt% Pt/C (ETEK) catalyst. Electrochemical and physical properties of both materials were characterized in detail. Pt-ON/C shows competitive ORR activity similar to Pt/C (ETEK) while demonstrating an improved stability. By using post mortem analysis with transmission electron microscope/scanning transmission electron microscope (TEM/STEM), the degradation mechanisms of both catalysts are investigated. Two different dominant mechanisms were suggested to explain the decreased activity of Pt/C (ETEK) under different operation protocols: for an accelerated stress test (AST) with low maximum potentials, a loss of Pt surface area associated with carbon oxidation leads to the decreased activity; while for AST with high maximum potentials, Pt particle growth, detachment, dissolution/re-deposition and severe carbon corrosion dominate the performance loss. In addition, in the catalyst of Pt-ON/C, Mo dissolution occurs under the entire potential window which, however, leads to the enhanced activity after lifetime stability test protocol.

Standardized Benchmarking of Water Splitting Catalysts in a Combined Electrochemical Flow Cell/Inductively Coupled Plasma–Optical Emission Spectrometry (ICP-OES) Setup

The oxygen evolution reaction (OER) is the limiting step in splitting water into its constituents, hydrogen and oxygen. Hence, research on potential OER catalysts has become the focus of many studies. In this work, we investigate capable OER catalysts but focus on catalyst stability, which is, especially in this case, at least equally as important as catalyst activity. We propose a specialized setup for monitoring the corrosion profiles of metal oxide catalysts during a stability testing protocol, which is specifically designed to standardize the investigation of OER catalysts by means of differentiating between catalyst corrosion and deactivation, oxygen evolution efficiency, and catalyst activity. For this purpose, we combined an electrochemical flow cell (EFC) with an oxygen sensor and an inductively coupled plasma–optical emission spectrometry (ICP-OES) system for the simultaneous investigation of catalyst deactivation, activity, and faradaic efficiency of catalysts. We tested various catalysts, with ...

New Accelerating Stability Testing Protocol for O/W Emulsions Stabilized by Nonionic Surfactants Including Storage Temperature Determination

Betnovate®, Daktacort®, Daktarin®, Hemoclar®, Kenacomb® and Lotriderm® are O/W creams stabilized by nonionic surfactant/s and distributed in the Egyptian market without stability problems. In this work, the above creams were used as stability reference standard creams to extrapolate numeral values for the proposed parameters of the new accelerated stability testing protocol. The temperature–conductivity relations that represent all the above tested creams have strong direct linear relationships. Determination coefficient R2 values of these relations were ≥0.909 and their yield values represented as temperatures were ≥21o. The stability-indicating phase inversion temperatures of these creams were more than 80o. These common characteristic results represent the basis parameters of the new accelerating stability testing protocol as well as for the determination of the optimum storage temperature of the emulsion under examination. The applicability and validity of this protocol is confirmed by comparing the parameters results obtained from newly formulated O/W 2% miconazole nitrate cream to that obtained from the and also by subjecting all the tested O/W creams including the newly formulated one to accelerating stability testing studies according to the recent approved Issues of ICH Guidelines Q1A (R2). These accelerating stability studies include the measurements of the homogeneity, average weight and leakage test, drug content, pH, viscosity and microbiological analysis of the emulsion. Matching of the compared results and the approval of the stability testing studies confirms the applicability and validity of the new protocol. The new protocol determines the optimum storage temperature condition required for each cream under examination through the determination of the yield value represented as temperature of its temperature–conductivity relation.

Developing Protocols for Measuring Biosolids Stability

The general goal of this project is to validate test protocols that are commonly used to assess the stability of various biosolids products, and to specify a standard for each test method. Toward this end, the project team conducted a literature review, surveyed selected practicing facilities, and conducted a sampling and analysis program. Information concerning stability-testing protocols and data for each biosolids-stabilization technology and testing method reviewed were collected and evaluated. The biosolids-stabilization technologies reviewed were aerobic and anaerobic digestion, alkaline stabilization, and composting; the testing methods reviewed were specific oxygen uptake rate, volatile solids reduction, additional volatile solids reduction, pH and changes in pH, and carbon dioxide evolution. The report recommends specific protocols for each testing method, and presents intrinsic precision data for each protocol. In addition, data is presented from facilities using each protocol, to serve as a basis for evaluating the collective degree of variability associated with each stabilization process. Collective variability results from sampling, feedstock, the stabilization process, and the intrinsic variability of each testing method. Using split sample testing, interlaboratory data (variability among different laboratories) are presented. Issues associated with variability, error sources, shortcomings, and numerical criteria values are discussed for each method. This title belongs to WERF Research Report Series ISBN: 9781843396550 (eBook)

Postero-lateral disc prosthesis combined with a unilateral facet replacement device maintains quantity and quality of motion at a single lumbar level.

BackgroundMechanically replacing one or more pain generating articulations in the functional spinal unit (FSU) may be a motion preservation alternative to arthrodesis at the affected level. Baseline biomechanical data elucidating the quantity and quality of motion in such arthroplasty constructs is non-existent.PurposeThe purpose of the study was to quantify the motion-preserving effect of a posterior total disc replacement (PDR) combined with a unilateral facet replacement (FR) system at a single lumbar level (L4-L5). We hypothesized that reinforcement of the FSU with unilateral FR to replace the resected, native facet joint following PDR implantation would restore quality and quantity of motion and additionally not change biomechanics at the adjacent levels.Study DesignIn-vitro study using human cadaveric lumbar spines.MethodsSix (n = 6) cadaveric lumbar spines (L1-S1) were evaluated using a pure-moment stability testing protocol (±7.5 Nm) in flexion-extension (F/E), lateral bending (LB) and axial rotation (AR). Each specimen was tested in: (1) intact; (2) unilateral FR; and (3) unilateral FR + PDR conditions. Index and adjacent level ROM (using hybrid protocol) were determined opto-electronically. Interpedicular travel (IPT) and instantaneous center of rotation (ICR) at the index level were radiographically determined for each condition. ROM, ICR, and IPT measurements were compared (repeated measures ANOVA) between the three conditions.ResultsCompared to the intact spine, no significant changes in F/E, LB or AR ROM were identified as a result of unilateral FR or unilateral FR + PDR. No significant changes in adjacent L3-L4 or L5-S1 ROM were identified in any loading mode. No significant differences in IPT were identified between the three test conditions in F/E, LB or AR at the L4-L5 level. The ICRs qualitatively were similar for the intact and unilateral FR conditions and appeared to follow placement (along the anterior-posterior (AP) direction) of the PDR in the disc spaceConclusionBiomechanically, quantity and quality of motion are maintained with combined unilateral FR + PDR at a single lumbar spinal level.

TiO2–RuO2 electrocatalyst supports exhibit exceptional electrochemical stability

Titanium dioxide–ruthenium dioxide (TiO2–RuO2; TRO) powders were prepared in both the hydrous and anhydrous form using a wet chemical synthesis procedure. These materials were characterized by XRD, TEM, and BET. Their electrical conductivity and electrochemical properties such as stability under potential cycling, electrochemical surface area (ECSA), electrocatalytic activity, and fuel cell performance were measured. Anhydrous TiO2–RuO2 (TRO-a) demonstrated exceptional electrochemical stability compared to baseline Vulcan XC-72R carbon when tested using an aggressive accelerated stability test (AST) protocol. The various TRO powders were catalyzed by depositing platinum nanoparticles by an impregnation–reduction method to yield Pt/TRO electrocatalysts. The Pt/TRO-a electrocatalysts had a mass activity of 54 mA mgPt−1 and a specific activity of 284 μA cmPt−2 for the oxygen reduction reaction. Fuel cell polarization data was obtained on membrane electrode assemblies (MEAs) prepared with Pt/TRO and baseline Pt/C electrocatalysts showed that the Pt-TRO-based MEAs exhibited very good performance. The performance obtained was below the Pt/C benchmark, however, further improvements in performance are expected with greater optimization of the Pt particle size and electrode structure.

Ta0.3Ti0.7O2 Electrocatalyst Supports Exhibit Exceptional Electrochemical Stability

Tantalum (Ta) modified TiO2 was synthesized using a sol-gel procedure and evaluated for use as an electrocatalyst support. Platinum nanoparticles were deposited on this support via the incipient wetness method. X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray energy dispersive spectroscopy (XEDS), X-ray photoelectron spectroscopy (XPS) and nitrogen desorption were used to investigate their microstructure. Of the formulations studied, Ta0.3Ti0.7O2 possessed an adequate powder electronic conductivity of 0.2 S/cm. The capacitance of this Ta0.3Ti0.7O2 support changed by only 12% whereas the pseudocapacitance of a carbon benchmark changed by over 100% over 10,000 support stability test cycles (support stability test protocol: 1.0-1.5 V vs. RHE at a scan rate of 500 mV/s in a 0.1 M HClO4 electrolyte at 25°C) under identical test conditions. The stability of 20% Pt/Ta0.3Ti0.7O2, 20% Pt/C, and 46% Pt/C (commercial, TKK) catalysts were evaluated by monitoring the evolution of the electrochemical surface area (ECSA) under load cycling (load cycling protocol: 0.6-0.95 V vs. RHE with a dwell time of 3 s at either potentials in a 0.1 M HClO4 electrolyte at 25°C). The loss in ECSA in 20% Pt/Ta0.3Ti0.7O2 was found to be 35% compared to 44-47% for 20% Pt/C and 46% Pt/C over 10,000 load cycles. 20% Pt/Ta0.3Ti0.7O2 yielded the following performance-related metrics: the ECSA of this electrocatalyst was 41 m2/g, the mass activity and area-specific activities for the oxygen reduction reaction (ORR) determined at 0.9 V vs. RHE in a 0.1 M HClO4 electrolyte at 25°C were 62 mA/mgPt and 151 μA/cm2Pt, respectively. Koutecky-Levich analysis carried out to evaluate ORR kinetics suggested that all 3 catalysts (20% Pt/Ta0.3Ti0.7O2, 20% Pt/C and 46% Pt/C) demonstrated similar ORR mechanisms. We propose that Ta0.3Ti0.7O2 shows outstanding promise as a corrosion-resistant alternative to carbon as an electrocatalyst support in polymer electrolyte fuel cells.

Primary Stability of a Dynamic Artificial Disc Tested in a Human Cadaveric Model

Abstract Sufficient anchorage of an interbody device will allow osseointegration and avoid implant migration. Shear forces in the lumbar spine are transferred across the bone/implant interface, resulting in relative motion between the implant and bone. Relative motion greater than 150 μm will have a detrimental effect on the osseointegration of titanium (Ti) implants. This study developed an in vitro, primary stability testing protocol to assess a total disc replacement (TDR). Testing was performed on seven human cadaveric L4 and L5 vertebrae. Cyclic shear loading of the prepared implant/bone interface was applied for 20 cycles in the anterior and posterior directions to ±350 N under an axial compressive load of 600 N. The relative motion was measured and the average of the last five cycles analysed. The shear force necessary to cause complete anterior migration of the TDR was also measured. The averaged cyclic motion for the last five cycles in both the anterior and posterior directions was below 85 μm for all specimens. The average yield force for complete anterior implant migration was 522.2 N (±105.9 N) and the failure force was 605.1 N (±118.4 N). A primary stability testing protocol was developed and employed to assess a TDR in human cadaveric bone. The measured relative motion for this TDR for each loading cycle was below 150 μm, which is favourable for osseointegration with the vertebral body endplates.

Butyronitrile-Based Electrolyte for Dye-Sensitized Solar Cells

We elaborated a new electrolyte composition, based on butyronitrile solvent, that exhibits low volatility for use in dye-sensitized solar cells. The strong point of this new class of electrolyte is that it combines high efficiency and excellent stability properties, while having all the physical characteristics needed to pass the IEC 61646 stability test protocol. In this work, we also reveal a successful approach to control, in a sub-Nernstian way, the energetics of the distribution of the trap states without harming cell stability by means of incorporating NaI in the electrolyte, which shows good compatibility with butyronitrile. These excellent features, in conjunction with the recently developed thiophene-based C106 sensitizer, have enabled us to achieve a champion cell exhibiting 10.0% and even 10.2% power conversion efficiency (PCE) under 100 and 51.2 mW·cm(-2) incident solar radiation intensity, respectively. We reached >95% retention of PCE while displaying as high as 9.1% PCE after 1000 h of 100 mW·cm(-2) light-soaking exposure at 60 °C.

Consensus stability testing protocols for organic photovoltaic materials and devices

Procedures for testing organic solar cell devices and modules with respect to stability and operational lifetime are described. The descriptions represent a consensus of the discussion and conclusions reached during the first 3 years of the international summit on OPV stability (ISOS). The procedures include directions for shelf life testing, outdoor testing, laboratory weathering testing and thermal cycling testing, as well as guidelines for reporting data. These procedures are not meant to be qualification tests, but rather generally agreed test conditions and practices to allow ready comparison between laboratories and to help improving the reliability of reported values. Failure mechanisms and detailed degradation mechanisms are not covered in this report.

Impact of cryopreservation on serum concentration of matrix metalloproteinases (MMP)-7, TIMP-1, vascular growth factors (VEGF) and VEGF-R2 in Biobank samples

Blood biomarkers are subject to pre-analytical variability. In many cases, the stability of important new tissue biomarkers during freeze cycles and storage has not been studied sufficiently. To test the stability of matrix metalloproteinases-7 (MMP-7) and their tissue inhibitors (TIMP-1), vascular growth factors (VEGF) and VEGF-receptor, serum samples were frozen and then thawed up to six times. The impact of storage temperature was investigated using an accelerated stability testing protocol. Stability at -20°C and -75°C was calculated using the Arrhenius equation. The average concentration of TIMP-1 was stable, even after six freeze/thaw cycles. One thawing did not change the concentration of MMP-7 and VEGF-receptor. However, repeated freeze/thaw cycles increased the measured values significantly. Decreases in VEGF concentrations were dramatic, even after the first freeze/thaw cycle. According to the Arrhenius calculation, MMP-7 showed excellent stability, at least 5 years at -20°C and several 100 years at -75°C. The VEGF-receptor maintains 90% of its initial concentration at -20°C over 3 months, and decades at -75°C. TIMP-1 and VEGF showed poor stability with cryopreservation, even at -75°C. The stability of MMP-7, TIMP-1, VEGF or VEGF-receptor in biobanking is highly variable, and this should be taken into account in the interpretation of results. A temperature -20°C is unsuitable for prolonged storage of the biomarkers investigated, and repeated thawing of sera is not recommended. VEGF is especially unstable and should be quantitated using serum that has never been frozen.

Prediction of Onset of Crystallization in Amorphous Pharmaceutical Systems: Phenobarbital, Nifedipine/PVP, and Phenobarbital/PVP

The aim of this work is to determine if a stability testing protocol based on the correlations between crystallization onset and relaxation time above the glass transition temperature (T(g)) can be used to predict the crystallization onsets in amorphous pharmaceutical systems well below their T(g). This procedure assumes that the coupling between crystallization onset and molecular mobility is the same above and below T(g). The stability testing protocol has been applied to phenobarbital, phenobarbital/polyvinylpyrrolidone (PVP) (95/5, w/w), and nifedipine/PVP (95/5, w/w). Crystallization onsets have been detected by polarized light microscopy examination of amorphous films; molecular mobility has been determined by dielectric relaxation spectroscopy above T(g) and by both isothermal calorimetry and modulated differential scanning calorimetry below T(g). We find that small amounts of PVP significantly retard re-crystallization. This dramatic effect of PVP is not related to mobility, so this approach applies, at best, to extrapolation of high temperature data on a given formulation to low temperatures. Variation in molecular mobility at these concentrations of PVP is not the dominant factor in determining variation in propensity for re-crystallization from glassy systems; we suggest surface interactions between PVP and nuclei and/or small crystals slowing growth control variation in crystallization kinetics between formulations.

Use of a Quality-by-Design approach to justify removal of the HPLC weight % assay from routine API stability testing protocols

Due to the high method variability (typically ≥0.5%, based on a literature survey and internal Merck experience) encountered in the HPLC weight percent (%) assays of various active pharmaceutical ingredients (APIs), it is proposed that the routine use of the test in stability studies should be discouraged on the basis that it is frequently not sufficiently precise to yield results that are stability-indicating. The high method variability of HPLC weight % methods is not consistent with the current ICH practice of reporting impurities/degradation products down to the 0.05% level, and it can lead to erroneous out-of-specification (OOS) results that are due to experimental error and are not attributable to API degradation. For the vast majority of cases, the HPLC impurity profile provides much better (earlier and more sensitive) detection of low-level degradation products. Based on these observations, a Quality-by-Design (QbD) approach is proposed to phase out the HPLC weight % assay from routine API stability testing protocols.

Prediction of Onset of Crystallization from Experimental Relaxation Times. II. Comparison between Predicted and Experimental Onset Times

Given a good correlation between onsets of crystallization and mobility above T(g), one might be able to predict crystallization onsets at a temperature of interest far below T(g) from this correlation and measurement of mobility at a temperature below T(g). Such predictions require that: (a) correlation between crystallization onset and mobility is the same above and below T(g), and (b) techniques used to measure mobility above and below T(g) measure the same kind of mobility [(b) demonstrated previously using dielectric and calorimetric techniques]. The objective of present work is to determine whether crystallization onset times couple with relaxation times determined above T(g), and if so to verify predictions made below T(g) (from data above T(g)) with experimental data. Model compounds were indomethacin, ketoconazole, flopropione, nifedipine, and felodipine. Onsets of crystallization measured above T(g) were coupled with dielectric mobility for indomethacin, felodipine, and flopropione. Prediction of crystallization onset times for temperatures below T(g) matched well with experimental data for indomethacin (25 degrees C, 35 degrees C: Predicted 473, 95 h; 624 +/- 158, 139 +/- 49 h) and flopropione (35 degrees C, 40 degrees C; Predicted 115, 58 h; 96 +/- 30, 59 +/- 10 h). The data suggests that coupling between crystallization onsets and molecular mobility at temperatures above T(g) may be exploited to develop stability testing protocol for crystallization from amorphous state.

Effects of Processing and Storage Conditions on Amyloid β (1–42) and Tau Concentrations in Cerebrospinal Fluid: Implications for Use in Clinical Practice

Reported concentrations of amyloid beta (1-42) (A beta 42) and tau in cerebrospinal fluid (CSF) differ among reports. We investigated the effects of storage temperature, repeated freeze/thaw cycles, and centrifugation on the concentrations of A beta 42 and tau in CSF. Stability of samples stored at -80 degrees C was determined by use of an accelerated stability testing protocol according to the Arrhenius equation. A beta 42 and tau concentrations were measured in CSF samples stored at 4, 18, 37, and -80 degrees C. Relative CSF concentrations (%) of the biomarkers after one freeze/thaw cycle were compared with those after two, three, four, five, and six freeze/thaw cycles. In addition, relative A beta 42 and tau concentrations in samples not centrifuged were compared with samples centrifuged after 1, 4, 48, and 72 h. A beta 42 and tau concentrations were stable in CSF when stored for a long period at -80 degrees C. CSF A beta 42 decreased by 20% during the first 2 days at 4, 18, and 37 degrees C compared with -80 degrees C. CSF tau decreased after storage for 12 days at 37 degrees C. After three freeze/thaw cycles, CSF A beta 42 decreased 20%. CSF tau was stable during six freeze/thaw cycles. Centrifugation did not influence the biomarker concentrations. Repeated freeze/thaw cycles and storage at 4, 18, and 37 degrees C influence the quantitative result of the A beta 42 test. Preferably, samples should be stored at -80 degrees C immediately after collection.

STABILITY OF INTERLEUKIN 6, SOLUBLE INTERLEUKIN 6 RECEPTOR, INTERLEUKIN 10 AND CC16 IN HUMAN SERUM

The stability of interleukin 6 (IL-6), its soluble receptor (sIL-6R), IL-10 and CC16 or uteroglobin (an endogenous cytokine inhibitor) in human serum was examined using an accelerated stability testing protocol according to the Arrhenius equation. Further, the effect of time delay between blood sampling and sample processing, clotting temperature and repeated freeze-thaw cycles on serum levels of these proteins were determined. Paired serum samples were stored at 4 degrees C, 20 degrees C, 30 degrees C and 40 degrees C for 1 to 21 days. We found that IL-6 and CC16 concentrations did not change at 4 degrees C, 20 degrees C and 30 degrees C. Interleukin-6 concentrations significantly declined after 11 days at 40 degrees C. The concentrations of sIL-6R and IL-10 did not change at 4 degrees C but significantly decreased at 20 degrees C (after 21 and 14 days respectively), 30 degrees C and 40 degrees C (after 1 day at both temperatures for both cytokines). Arrhenius-plots indicated that sIL-6R and IL-10 are stable for at least several years at -20 degrees C and -70 degrees C, respectively. Since their relative stability, no Arrhenius-plot could be calculated for IL-6 and CC16. The concentrations of the proteins examined were not significantly altered by repeated freeze-thaw cycles, nor by extended clotting times at 4 degrees C or 20 degrees C. We conclude that serum samples for the determination of IL-6, sIL-6R and CC16 can be stored at -20 degrees C for several years, but for IL-10 determinations, storage at -70 degrees C is recommended.

DEVELOPING PROTOCOLS FOR MEASURING BIOSOLIDS STABILITY

The general goal of this project is to validate test protocols that are commonly used to assess the stability of various biosolids products, and to specify a standard for each test method. Toward this end, the project team conducted a literature review, surveyed selected practicing facilities, and conducted a sampling and analysis program. Information concerning stability-testing protocols and data for each biosolids-stabilization technology and testing method reviewed were collected and evaluated. The biosolids-stabilization technologies reviewed were aerobic and anaerobic digestion, alkaline stabilization, and composting; the testing methods reviewed were specific oxygen uptake rate, volatile solids reduction, additional volatile solids reduction, pH and changes in pH, and carbon dioxide evolution. The report recommends specific protocols for each testing method, and presents intrinsic precision data for each protocol. In addition, data is presented from facilities using each protocol, to serve as a basis for evaluating the collective degree of variability associated with each stabilization process. Collective variability results from sampling, feedstock, the stabilization process, and the intrinsic variability of each testing method. Using split sample testing, interlaboratory data (variability among different laboratories) are presented. Issues associated with variability, error sources, shortcomings, and numerical criteria values are discussed for each method. This title belongs to WERF Research Report Series ISBN: 9781843396550 (eBook)

Lightfastness Studies of Water-based Inkjet Inks on Coated and Uncoated Papers

Instrumental color (i.e. L*A*B*) and optical density measurements were performed on coated and uncoated papers printed with water based inkjet inks using continuous binary array inkjet equipment. Lightfastness tests were performed in a QUV test chamber with Cool White Fluorescent lamps, Q-Sun Xenon Arc Test Chamber with a Window Glass Filter, and under glass at a Florida outdoor benchmark location (Q-Lab Weathering Research Service). These results were compared with two indoor exposure locations. Rank order was used to show good correlation between the various exposure methods. The results of this study generated data indicating that the lightfastness of water-based inkjet inks can be complex and dictated by the type of coated or uncoated paper used. This study also shows that inks printed on coated substrates are more susceptible to UV degradation than those printed on a bond or uncoated substrate. The development of a light stability test protocol is intended to simulate the conditions of the actual service environment. Meaningful data can be produced to better evaluate the “archivability” or predict durability of inkjet inks and substrates.

Determination of shelf life and activation energy for tumor necrosis factor-alpha in cerebrospinal fluid samples

The cytokine rumor necrosis factor-alpha (TNF-alpha) plays a prominent role in the inflammatory response and has been quantified in several kinds of body fluids. A safe method for keeping samples under the best storage conditions for later studies is clearly needed. We estimated TNF-alpha shelf life by using an accelerated stability testing protocol based on the Arrhenius equation. We investigated two kinds of samples: cerebrospinal fluid (CSF) normal pool (from patients without meningitis) and CSF pathological pool (from patients with pyogenic meningitis). Results of the stress protocol indicated that storing both normal and pathological CSF samples at -70 degrees C would maintain sample stability-i.e., retain at least 90% of the original TNF-alpha content-for approximately 5 years. At -20 degrees C and 4 degrees C, the projected stability time at which the same recovery would be obtained was 190 and 90 days, respectively.