Search

The objectives of root canal treatment are elimination of microorganisms, removal of pulpal remnants, removal of debris, and shaping of the root canal system so that it may be obturated. The most important step in endodontic therapy is canal preparation which can be achieved by accurate working length determination. Working length determines the extent of placing the instruments into the canal, it affects the degree of pain and discomfort which the patient will experience post treatment and it plays an important role in the success of the treatment if placed within correct limits. The cementodentinal junction, where the pulp tissue changes into the apical tissue, is the ideal physiologic apical limit of WL because at this point healing is supposed to be optimal, and the wound to the periapical tissues is minimal.The apical constriction is however, histological and is impossible to locate clinically or radiographically. There are several methods of determining working length which include radiographical methods, digital tactile sense, apical periodontal sensitivity, paper point method and electronic apex locators. The requirements of an ideal method for determining working length include rapid location of the apical constriction in all pulpal conditions, easy measurement, rapid periodic monitoring and confirmation, patient and clinician comfort, minimal radiation to the patient; ease of use in special patients; and cost effectiveness. To achieve the highest degree of accuracy in working length determination, a combination of several methods should be used. This article reviews the different methods to determine WL and their clinical implications. KEY WORDS Working Length, Apex Locator, Radiographic Method.

Decentralized wastewater treatment has become inevitable as conventional wastewater treatment plants involve huge construction and maintenance costs. One of the most popularly used decentralized wastewater treatments is constructed wetlands. Constructed wetlands are a cost-effective and sustainable treatment method for domestic and industrial wastewater. Over the years, there has been a lot of improvement in the design and process approaches of constructed wetlands. This review paper aims to find the impacts of design processes like artificial aeration, design and flow pattern, effluent recirculation, substrate media, vegetation, and C/N ratio on the treatment performance of constructed wetlands. Based on the review, it is found that intermittent aeration along with recirculation, hybrid constructed wetlands and baffled constructed wetlands are an effective way to remove ammonia and organics from wastewater. Phosphorous removal in constructed wetlands is highly dependent on substrates rather than wetland plants. Further, the paper discusses the future scopes and challenges in terms of improving the efficiency of constructed wetlands, reuse of industrial waste as substrate, solar energy based aeration, etc., to make constructed wetlands a sustainable wastewater treatment technology.

Moniezia expansa is common cestode in the small intestine of sheep and causes considerable damage to it. Therefore, an effort to study such biological aspects of Moniezia expansa which would help in its control is much needed. The glycogen content and in vitro consumption of endogenous glycogen was determined in immature, mature and gravid proglottids of Moniezia expansa by Anthrone method by Carroll et al.(1956). The total glycogen (on fresh weight basis) was found to be 3.03%, 4.26% and 3.85% respectively in immature, mature and gravid proglottids of unstarved (control) parasite. The glycogen content in immature, mature and gravid proglottids of parasites starved for 3 hrs. is 2.51%, 3.09% and 2.91% respectively, parasites starved for 6 hrs is 1.91%, 2.0% and 2.0% respectively, parasites starved for 9 hrs. 1.25%, 1.33% and 1.35 respectively and parasites starved for 12 hrs is 0.79%, 0.80% and 0.99% respectively (on fresh weight basis).The endogenous glycogen consumption (in percent of total glycogen content of control parasite) by immature, mature and gravid proglottid was found to be 17.16%, 27.46% 24.42% respectively in parasites starved for 3 hours, 36.96%, 53.05% and 48.05% respectively in parasites starved for 6 hours, 58.75% 68.78% and 64.94% respectively in parasites starved for 9 hours and 73.93%, 81.22% and 74.29% respectively in parasites starved for 12 hours. Rate of consumption of endogenous glycogen between different starvation time periods (in percentage per hour) for immature, mature and gravid proglottids is also calculated. Rate of consumption was maximum during early hours of starvation i.e. between 0–3 hrs and 3–6 hrs and was minimum at 9–12 hrs. Glycogen is the major energy reserve in parasitic helminths which live in low oxygen condition, as they are the best substrate for anaerobic energy production. The study of consumption of endogenous glycogen in cestode during starvation period may be quite helpful for their control in the host. The rate of endogenous glycogen consumption is helpful in understanding metabolic rate and physiological aspects of different proglottids of the parasite.

Normal modes and their dispersion have been obtained for polyselenophene (PSe) in the reduced zone scheme using Wilson's GF matrix method as modified by Higg's for an infinite polymeric chain. The Urey Bradley potential field is obtained by least square fitting to the observed infrared and Raman bands. The results thus obtained agree well with the experimental IR and Raman values. The characteristic features of dispersion curves such as repulsion and exchange of character, crossing, van Hove type singularities have been discussed and possible explanation has been given. Heat capacity has been calculated via density-of-states using Debye relation in the temperature range 0–450 K. Possible explanation for the inflexion region in the heat capacity variation is given. The spectra of the oligomers are checked with the finite–infinite spectral relationship and are found to be in agreement.

Polyvinylidene fluoride (PVDF) is a polymer of industrial importance, mainly due to its piezoelectric and pyroelectric properties. A comprehensive study of the normal modes and their dispersion in PVDF (β-form) has been reported in the reduced zone scheme using Wilson’s GF matrix method as modified by Higgs. A Urey-Bradley force field has been used. The evaluation of normal modes and their dispersion has been taken to logical conclusion by calculating the heat capacity as a function of temperature. The extent of agreement with the experimental data supports the potential field. Characteristic features of the dispersion curves such as repulsion and exchange of character have also been discussed.

Normal modes and their dispersion are obtained for planar zig-zag form of poly(β-hydroxybutyrate) using Urey–Bradley force field. A comparison is made with the spectra of its helical form. Apart from detailed assignment of modes, various characteristic features of dispersion curves have been explained as arising due to internal symmetry in energy momentum space. The density-of-states have been used to calculate heat capacity in the temperature range 10–450 K using Debye's formalism.

Normal modes and their dispersion have been obtained for polychloroprene in the trans form using Wilson's G F matrix method as modified by Higg's for an infinite polymeric chain. Urey Bradley force field has been used. Several new assignments, which are missing in earlier work, are reported. The assignments of lower frequency modes have been confirmed using inelastic neutron scattering data. The characteristic features of dispersion curves have been explained. Variation of heat capacity as a function of temperature has been predicted. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

computing principles focus on large-scale resource sharing in distributed systems in a flexible, secure and coordinated fashion. The most widespread contemplation is performance, because computational grid servers must offer cost-effective and high-availability services in the elongated period, thus they have to be scaled to meet the expected load. Performance measurements can be the base for performance modeling and prediction. With the help of performance models, the performance metrics (like buffer estimation, waiting time) can be determined at the development process. This paper describes the possible queue models those can be applied in the estimation of queue length to estimate the final value of the memory size. Both simulation and experimental studies using synthesized workloads and analysis of real-world Gateway Servers demonstrate the effectiveness of the proposed system.

Normal modes and their dispersion have been obtained for trans polydichlorobutadiene (PDCB) in the reduced zone scheme using Wilson’s G F matrix method as modified by Higg’s for an infinite polymeric chain. The Urey Bradley potential field is obtained by least square fitting of the observed infrared and Raman bands. The obtained results agree well with the experimental values. Because of the presence of centre of symmetry, the PDCB molecule obeys the mutual exclusion principle. Several new assignments which are missing in the earlier work are reported. The characteristic features of dispersion curves such as repulsion and exchange of character have been discussed and possible explanation has been given. Heat capacity has been calculated via density-of-states using Debye relation in the temperature range 10–450 K.

The normal modes and their dispersions for poly(l-asparagine) (PLN) in the α-helical form have been obtained in a reduced zone scheme with Wilson's GF matrix method as modified by Higgs. The results indicate that the modes below 1350 cm−1 show appreciable dispersion. Optically active frequencies corresponding to the zone center and zone boundary are identified and discussed. Some of the characteristic features of the dispersion curves are repulsion accompanied by an exchange of character and von Hove singularities. Amide modes, side chain modes, and mixed modes are reported. The heat capacity calculated from the dispersion curves via density-of-states using Debye's relation is compared with the experimental data in the temperature range of 220–390 K.

Polyaniline is unique among conducting polymers in that its electrical properties can be reversibly controlled both by the oxidation state of the main chain and by protonation. In the present communication we report normal modes and their dispersion in polyaniline pernigraniline base (PANI PNB) form using Urey - Bradely force field which in addition to valence force field accounts for the non-bonded interactions in the gem and cis configurations and tension terms. Some of the distinguished features of the dispersion curves such as cross-over and Von Hove type of singularities are discussed and possible explanations are given in terms of symmetry considerations. Several new assignments, which are missing in earlier work, are reported.

Microbial poly(e-L-lysine)(M-e-PL) is a naturally occurring biomaterial, which is water soluble, biodegradable, edible and non-toxic towards humans and environment. Normal mode analysis including phonon dispersion has been performed to understand completely the vibrational spectra of this polymer. Various characteristic features of the dispersion curves have been reported. The heat capacity is calculated as a function of temperature via density-of-states in the range 1-450 K.

Normal modes and their dispersion are reported for polydichlorophosphazene (PDCP). This polymer has several interesting features. Its backbone flexibility allows more than one structural possibility such as distorted cis‐trans planar, cis‐trans planar. PDCP can be used to prepare different polyphosphazenes which have many applications such as fire resistant materials, photonic materials, membranes, etc. Some of the distinguishing features of dispersion curves such as cross‐over, bunching and Von Hove type of singularities are discussed and possible explanations are given in terms of symmetry considerations. Several new assignments, which are missing in earlier work, are reported.

Vibration Spectra of Polyglycine Chain

The normal modes and their dispersions for poly(L-tryptophan) (PLTR) in the α-helical form have been obtained in a reduced zone scheme with Wilson's GF matrix method as modified by Higgs. Dynamic studies of the α form are of special significance as it is the predominant secondary structure for protein molecules. X-ray and circular dichroism (CD) studies by Peggion et al. have confirmed the α-helical conformation of PLTR. The side group of PLTR is more complicated than that of other natural polypeptides. It consists of both a pyrrole and a benzene ring along with a CH2 group. Optically active frequencies corresponding to the zone center and zone boundary are identified and discussed. Some of the characteristic features of the dispersion curves are repulsion accompanied by an exchange of character and von Hove singularities. The heat capacity has been calculated via densities of state with Debye's equation in the temperature range of 220–390 K and has been compared with experimental measurements. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 316–332, 2004

The normal modes and their dispersions for poly(l-ornithine) in the unusual cross-β form have been obtained in the reduced zone scheme using Wilson's GF matrix method as modified by Higgs. Optically active frequencies corresponding to the zone center and zone boundary are identified and discussed. Some of the characteristic features of the dispersion curves are repulsion accompanied by an exchange of character and von Hove type singularities. Heat capacity has been calculated via density-of-states using Debye's equation in the temperature range 50–500K.

Poly(β-benzyl- l -aspartate) (PBLA) shows unusual conformational variety and under varying conditions of preparation it is capable of adopting four different conformations, namely left-handed α helix (αl), right-handed α helix (αr), ω helix and β pleated sheet. We present here a complete phonon dispersion and heat capacity study on the β form of PBLA. A comparison of the characteristic features and the conformational dependence of modes for α, β and ω forms of PBLA are made. It is observed that the dispersion of modes in the β form is in general larger than in the α form. Crossing over and repulsion of various dispersion branches are discussed.

The normal modes and their dispersion are obtained for syndiotactic poly(4-methyl-1-pentene) in the reduced zone scheme using Wilson’s GF matrix method as modified by Higgs. Urey–Bradley force field has been used. A comparison is made with the spectra of its isotactic form to identify conformational sensitive modes and other spectral differences. Heat capacity has been calculated via density-of-states using Debye relation in the temperature range 50–330 K and compared with the experimental measurements.

The normal modes and their dispersions for form 1 of syndiotactic poly(1-butene) have been obtained using Wilson’s GF matrix method as modified by Higgs. Optically active frequencies corresponding to the zone center and zone boundary are identified and discussed. The Urey Bradley potential field is obtained by least square fitting of the observed Fourier transform infrared absorption bands. Specific heat has been obtained from dispersion curves via density of states. A comparative study of isotactic and syndiotactic forms of poly(1-butene) is presented.

Phonon dispersion studies have been made on the cis-transoid form of polyacetylene (PA) chain. Unlike the trans-transoid form reported earlier, this conformation shows crossover and repulsion characteristics in the optical modes. Detailed assignments of modes are given, and the predictive value of the heat capacity obtained via the density of states as a function of temperature is reported.

Poly( O -acetyl, l -serine), which is a precursor of poly( l -serine) in synthesic sequence, is found to exist in cross-β conformation. Normal mode analyses including phonon dispersion have been performed, to understand completely the FTIR spectra of this polypeptide, using Wilson's GF matrix method and Urey–Bradley force field. The characteristic features of dispersion curves like repulsion, exchange of character and bunching have been observed and discussed. In addition to the above the heat capacity is calculated as a function of temperature via density-of-states derived from dispersion curves.

Polymers of 2-methyl-1,3-pentadiene are capable of existing in both isotactic, as well as syndiotactic, configuration. The isotactic 1,4-cis polymer also exists in two stable forms that have different melting points. A complete study of normal modes and their dispersion was carried out using Higgs modification of Wilson's dynamical GF matrix method and the Urey Bradley force field. The force constants have been best fitted to the Fourier transform infrared (FTIR) frequencies. Characteristic features of dispersion curves, like bunching, repulsion, and exchange of character between various pairs of modes, were observed and are discussed here. In addition, the frequency distribution function derived from dispersion curves was used to calculate the heat capacity in the temperature range 50–450 K.

Poly(S-benzyl-L-cysteine) (PBLC) is a S-benzyl derivative of the natural amino acid poly(L-cysteine). Its normal modes and their dispersion in antiparallel β-sheet conformation have been obtained within the first Brillouin zone using Wilson's G.F. matrix method, as modified by Higgs for an infinite polymeric chain. The zone center frequencies and the Urey Bradley force field have been obtained by best fitting the observed Fourier transform IR (FTIR) absorption bands. The characteristic features of dispersion curves such as crossing, repulsion, and exchange of character are discussed. Predictive values of heat capacity in the temperature range of 50-500 K are reported.

Calculations of normal modes of isotactic 1,4- trans -poly(1,3-pentadiene) and their dispersion within the first Brillouin zone (reduced zone scheme) are reported here. Calculated vibrational frequencies are compared with the reported IR spectroscopic data and a close agreement is found between the two. Characteristic features of dispersion curves, like bunching and repulsion, are observed and discussed. Frequency distribution function derived from dispersion curves is used to calculate the heat capacity in the temperature range 50–450 K.

The Zimm and Bragg theory for helix-to-coil transitions has been suitably amended and applied to explain the two-step transition in the DNA triplex. The experimental measurements reported elsewhere have been successfully interpre- ted. The order-order and order-disorder transitions associated with the melting of the DNA triple helix, with and without netropsin binding, were characterized by the nucleation parameter, enthalpy change, sharpness of transition, and heat capacity. The destabilization of the triplex and stabilization of the duplex on netropsin binding are reflected in these characteristic parameters.

Normal modes and their dispersion are reported for the α-helical form of poly( l -aspartic acid) which is an important polypeptide used in the sustained release of drugs. Characteristic features of dispersion curves such as bunching and repulsion are discussed. Heat capacity is derived from the dispersion curves via density-of-states and compared with the available experimental data on sodium salt of the polymer.

It is well known that collagens exist in triple-helical form, and, on average, the individual chains have glycine at every third place. Collagens from different sources vary in distributions of other amino acids. They could also be different in the distribution of defects, which are generally nonhelical regions of low stability. Varying lengths of individual chains in the triple-helical system can also contribute to this variability. All these variations manifest themselves in the creation of a transition profile with undulations that are indicative of a multiphasic nature. In the present communication, we try to understand this variability by using essentially the Zimm and Bragg approach and suitably amending it for a triple-helical system. Factors that contribute to the multiphasic nature are incorporated into the transition model and discussed. Results obtained for collagen types I, II, III, Vx, Vy, and XI are in agreement with the experimental measurements. Transitions in the first three type...

Phonon dispersion studies for trans-l,4-polybutadiene (TPBD) are reported. The change in profile of the dispersion curves as a function of the ═CH─CH2─ dihedral angle φ has been obtained in order to find the geometry of the polymer that gives the best interpretation of the spectra. It is found for φ = 71°. The regions of high density of states obtained from the dispersion curves for an isolated chain have been used to explain the features of the spectra. Some of these, which were earlier attributed to interchain interactions, in fact arise due to intrachain interactions. Prominent features of the dispersion curves are discussed and heat capacity, derived therefrom, is reported. Calculations have also been performed for unsaturated C-deuterated and fully deuterated TPBD samples to check the validity of the force field and assignments.

Normal modes and their full dispersions are obtained for the right-handed α-helical poly(l-tyrosine). Optically active modes corresponding to the zone center and at the helical angle are assigned. Both the assignments and the force field are supported by the spectra of N-D species. In addition, modes corresponding to the regions of high density of states and other characteristic features of dispersion curves such as repulsion and exchange of character are discussed. Conformation sensitive modes of other α-helices are compared. Heat capacity is obtained from the dispersion curves via density of states and it is found in agreement with the measured data.

A stability-indicating high performance liquid chromatography assay method was developed to quantify metroprolol tartrate in pharmaceutical dosage forms. The method can also be used to quantify propranolol hydrochloride in injections and tablets. It is precise and accurate with a percent relative standard deviation of 0.9% for metoprolol and 0.7% for propranolol based on five determinations. The use of a counterion in the mobile phase is not required as described in the USP-NF method. Also, the procedure for extracting the drugs from tablets is very simple and does not require mechanical shaking for 30 minutes as described in the USP-NF. The new method was used to study the stability of metoprolol in an aqueous mixture. The drug was stable for at least 10 days when stored at 25 deg C in amber-colored bottles. However, 10% of the drug was not available due to adsorption onto the excipient. Solutions to this problem have been recommended.

The stability of cefmetazole sodium in 5% dextrose injection and 0.9% sodium choloride injection has been studied using a stability-indicating, high performance liquid chromatography (HPLC) assay method developed in our laboratory. This HPLC method is precise and accurate, with a percent relative standard deviation of 1.4 based on five readings. The admixtures were stable for two days at 25 deg C and for 28 days at 5 deg C, and they remained clear throughout the study period. The pH values decreased from 4.7 to 4.0 in 0.9% sodium chloride injection and from 4.8 to 4.2 in 5% dextrose injection. The expiry date of seven days at 5 deg C recommended by the manufacturer appears to be conservative from a chemical-stability standpoint.

The stability of indomethacin (from indomethacin sodium trihydrate powder for injection) in preservative-free 0.9% sodium chloride injection has been studied using a stability-indicating high-performance liquid chromatography assay method. The method described is precise and accurate, with a percent relative standard deviation of 0.7% based on five readings. The 0.1-mg/mL solutions were stable for at least ten days when stored at roomtemperature in 10-mL plastic vials in which the sodium chloride injections are marketed. The solutions remained clear throughout the study;and pH values did increase by about 0.5 units, since the admixtures were not buffered.

The stability of cefepime hydrochloride in 5% dextrose injection and 0.9% sodium chloride injection was studied using a stability-indicating assay method developed in our laboratory. This method is precise and accurate, with a percent relative standard deviation of 0.7% based on five readings. The admixtures were stable for two days at 25 deg C and 23 days at 5 deg C. The pH values of the admixtures did not change throughout this study, and the colors had changed from a very light yellow to a light yellow. The manufacturer recommends an expiry date of 24 hours at 20 to 25 deg C and seven days at 2 to 8 deg C.

The chemical stability of bethanechol aqueous solutions prepared using either tablets, injection or powder was studied. For an aqueous solution prepared using tablets, the initial result was low (86.5%) and the pH value was 7.1. With storage at 25 deg C, the result increased to almost 100% in 12 days and the pH value decreased to about 3.4. For the solution prepared from the injection, the initial result was 100%. After 40 days' storage at 25*C, the pH value decreased from 7.0 to 6.0 and the result was still almost 100% of the label claim. The aqueous solutions prepared from powder in phosphate buffers (pH values between 3.0 and 6.8) retained almost 100% of the potency at all pH values.

The chemical stabilities of ceftriaxone sodium and metronidazole in a mixture have been studied using a stability-indicating, high-performance liquid chromatography (HPLC) assay method. The HPLC method is precise and accurate, with a percent relative standard deviation of 1.4 based on five readings. Metronidazole did not lose any potency for four days when stored at 25+/-1 deg C. Ceftriaxone sodium lost less than 6% ofpotency in three days at 25+/-1 deg C. The products of decomposition did not interfere with the assay procedure. They eluted before the ceftriaxone peak. The solution remained clear (light yellow) throughout the study period, and the pH value did not change. Ceftriaxone sodium and metronidazole, when mixed together, were stable for three days at 25+/-1 deg C.

The adsorption of lorazepam in intravenous admixtures onto 50-mL polyvinyl chloride (PVC) bags has been studied using a spectorphotometric assay method reported in the literature. This method indicated a loss of 7.7% to 9.5% versus a high-performance liquid chromatography (HPLC) assay method developed in our laboratory, which showed a loss of 4.9% to 5.5%. In the spectrophotometric assay method, benzyl alcohol (the preservative in the lorazepam injection) interfered with the assay procedure. The HPLC assay method separated the peak of lorazepam from the benzyl alcohol peak. It also showed that part of the loss as determined by spectrophotometric assay method was due to the absorption of benzyl alcohol. The adsorbed lorazepam was adsorbed in less than six hours and there was no more loss after that. By storing different volumes of the admixture (20, 30, 40, and 50 mL) vertically in 50-mL PVC bags, the loss of drug due to adsorption did not show any siginificant differences.

The stability of ketorolac tromethamine in 5% dextrose injection and 0.9% sodium cholride injection has been studied using a stability-indicating, high-performance liquid chromatography assay method developed in our laboratory. This method is precise and accurate, with a percent relative standard deviation of 0.85% based on five readings. The admixtures were stable for at least 50 days when stored at 5 deg C. At 25 deg C the 0.9% sodium chloride admixture was stable for at least 35 days, and in 5% dextrose injection for only seven days. After 14 days of storage at 25 deg C the pH value of the admixture in 5% dextrose injection had decreased from 6.6 to 4.3. The changes in pH values of all other admixtures were less than 0.55. This assay method can be used to quantify ketorolac tromethamine in injections and tablets.

A high-performance liquid chromatography assay method for the quantitation of testosterone-cypionate-in-oil injection has been developed. The assay method is very simple, accurate and precise, with a percent relative standard deviation of 1.2 based on five readings. The extraction procedure is very simple compared with a very tedious and time-consuming procedure given in the United States Pharmacopoeia/National Formulary. The USP-NF assay method is based on gas chromatography. The benzyl alcohol (preservative) did not interfere with the assay preocedure. The newly developed method could not be applied to the quantitation of testosterone enanthate since the results were consistently low (-87%). The average recovery of testosterone cypionate from a commercial dosage form was 98.7%.

A high-performance liquid chromatographic assay method for the quantitation of alatrofloxacin in intravenous (IV) admixtures has been developed. The method is accurate and precise, with a percent relative standard deviation of 1.2% based on five injections. The method is stability indicating since the product of decomposition, trovafloxacin, did not interfere with the assay procedure. The IV admixtures of alatrofloxacin (1.88 mg/mL) in 5% dextrose and 0.45% sodium-chloride injections were stable for at least nine days when stored at room themperature. The pH values of the admixtures did not change and they remained clear throughout this study.

A high-performance liquid chromatography assay method for the quantition of testosterone propionate in an injection has been developed. The assay method is very simple, precise and accurate, with a percent relative standard deviation of 1.3 based on five injections. The benzyl alcohol (the preservative) and sesame oil (the vehicle) did not interfere with the assay procedure. The extraction procedure is very simple compared with a tedious and time-consuming method recommended in the USP-NF. The other similar compounds, testosterone, methyltestosterone, testosterone cypionate and testosterone enanthate, did not interfere with the assay method. Hence, the method developed is specific for this drug, versus the USP-NF method, which is nonspecific.

A high-performance liquid chromatographic assay method for the quantitation of trovafloxacin in film-coated tablets and an oral liquid dosage form (10 mg/mL) prepared from tablets has been developed. The assay method is very simple, precise and accurate, with a percent relative standard deviation of 1.8 based on five injections. The recovery from the tablets and the oral liquid dosage form was very close to the label claims. The method is stablilty indicating, since the peak from a degraded sample (using sodium hydroxide) did not interfere with the assay procedure. Furthermore, a number of excipients present in the tablets and the oral liquid dosage form did not interfere with the developed method. The oral liquid dosage form gave uniform results and the drug was stable for at least 14 days when stored in an amber-colored glass bottle at 25 deg C(+/-1). The pH of the formulation did not change.

An assay method based on high-performance liquid chromatography (HPLC), for the quantitation of testosterone in an aqueous suspension, has been developed. The method is very simple compared with a tedious and time-consuming method recommended by the USP-NF. It is an accurate and precise method; the percent relative standard deviation based on five injections was 1.15. The average recovery from four batches of suspension was 100% (percent relative standard deviation, 1.3) A number of inactive ingredients present in the suspension vehicle did not interfere with the assay procedure. Testosterone appears to be a very stable drug since it did not decompose significantly, even on heating. A 15-cm column gave sharper peaks vs. a 25-cm column and the sensitivity of the assay method increased by 400%.

The stability of pentobarbital sodium (10 mg/mL) in 0.9% sodium chloride injection and pentobarbital sodium (50 mg/mL) after repackaging in glass and polypropylene syringes has been studied at 25 deg C by means of a stability-indicating high-performance liquid chromatography assay method. The concentrations of the drug were directly related to peak heights, and the percent relative standard deviation based on 5 injections was 1.7. The pH value of the sample, which was prepared by diluting the injection (50 mg/mL) to 10 mg/mL with 0.9% sodium chloride injection, decreased from 9.2 to 8.2. At this pH, the free base began to crystallize out in less than 24 hours. After the undiluted commercial injection was repackaged in glass or polypropylene syringes, there was no significant loss of potency after 31 days of storage at 25 deg C. The pH value of the injection remained constant at 9.2.The pentobarbital sodium in injection appears to be very stable, because the loss in potency was only about 6.2% after it was boiled in water for 1.5 hours.

The chemical stability of methylprednisolone sodium succinate (10 mg/mL) in 0.9% sodium chloride injection has been studied at 25 deg C and 5 deg C in polypropylene syringes by means of a stability-indicating high-performance liquid chromatography assay method. The concentrations of the drug were directly related to the peak height, and the percent relative standard deviation based on five injections was 1.2. Benzyl alcohol, which is added as a preservative, did not interfere with the assay. Two products of decomposition separated from the intact drug. At 25 deg C, the loss of potency was less than 10% after 4 days of storage. At 5 deg C, the loss of potency was less than 5% when the injection was stored for 21 days. After 17 days of storage at 25 deg C, the pH value of the injection decreased from 7.2 to 6.5, and there was no change in the pH value when the injection was stored for 21 days at 5 deg C. The drug did not adsorb onto the syringes, and the physical appearance of the injection did not change.

The stability of ethacrynic acid (2.5 mg/mL) in oral liquid dosage forms was investigated. Tablets in 0.05 M phosphate buffer (available commercially) in water were used to prepare the dosage forms. The effects of mannitol and sugar on the stability of ethacrynic acid were negligible. There was no change in the physical appearance of the oral liquid dosage forms or pH values during the study. There was, however, a new peak in the chromatogram from the products(s) of decomposition. An oral liquid dosage form of ethacrynic acid containing 0.05 M phosphate buffer and 10% mannitol was stable for 24 days when stored at 5 deg C and for only 3 days when stored at 25 deg C.