Volumetric Flask Research Articles

Greater analytical accuracy through gravimetric determination of quantity

Scatter in analytical results caused by production tolerances in the volumetric measuring apparatus (pipettes, burettes, volumetric flasks), can be eliminated by weighing in the sample and standard solutions. For the techniques described, only conventional instruments and balances available in any analytical laboratory are required. In this way it is possible to improve the precision of the analytical result by a factor of 10.

Stability of esmolol hydrochloride and sodium nitroprusside in intravenous admixtures

The stability of esmolol hydrochloride and sodium nitroprusside in an admixture containing both drugs was studied. Solutions containing sodium nitroprusside in a final concentration of approximately 200 micrograms/mL and esmolol hydrochloride in a final concentration of 10 mg/mL in 5% dextrose injection were prepared in a 250-mL volumetric flask. The flask was wrapped with a light-protective cover, stored at ambient room temperature (15-30 degrees C), and protected from light. All experiments were conducted in triplicate with samples taken at 0, 2, 4, 8, and 24 hours. Testing included measurement of pH and absorbance at 400 and 600 nm. High-performance liquid chromatography was used to measure esmolol hydrochloride and sodium nitroprusside concentrations. No changes were observed in the physical appearance, pH, or absorbance of the admixtures. Neither the esmolol hydrochloride nor the sodium nitroprusside concentrations varied by more than 4% during the study. Under the conditions studied, esmolol hydrochloride is compatible with sodium nitroprusside in an admixture containing both drugs.

A Simple Extraction Procedure for Moderately Volatile Taste and Odor Compounds Such as Geosmin and 2-Methylisoborneol – Method and Applications

An extraction procedure is described which is the basis for a convenient method for analysis of large numbers of water samples for 2-methylisoborneol (MIB) and geosmin. The samples are extracted in a 2 1 volumetric flask by stirring with two small volumes of hexane or pentane. An internal standard is added to the dried extracts which are concentrated and analyzed by capillary gas chromatography using a flame ionization detector. Hexane gives better recoveries than pentane, and moderate to high stirring speeds are required. At 250 ng 1−1, hexane extraction is 49%±8% efficient for MIB and 59%±7% for geosmin at moderate stirring speeds. The detection limit is about 20 ng 1−1. This method has been used to analyze for MIB and geosmin in several Canadian water supplies and has been in use since 1984 at the Buffalo Pound Water Treatment Plant to monitor geosmin for various studies: a preliminary survey prior to startup of granular activated carbon (GAC) filtration for taste and odor control, monitoring performance of the GAC filters, and measuring release of geosmin from algae during pre-chlorination.

The Spectrofluorometric Determination of Anthraquinone with Hydroxylamine in the Dimethyl Sulfoxide Medium Containing Sodium Methoxide and Methanol

Abstract Anthraquinone reacts with hydroxylamine in the dimethyl sulfoxide (DMSO) medium containing sodium methoxide and methanol. Since the reaction product is fluorescent in the medium, this reaction can be used for the fluorometric determination of anthraquinone. A DMSO solution of a sample was mixed with a DMSO solution of hydroxylamine hydrochloride and a methanolic solution of sodium methoxide. The mixture was then allowed to stand for 20 min at 60 °C in a volumetric flask with a tightly fitting stopper. After cooling and dilution to the mark with DMSO, the fluorescence intensity of the solution was measured at 597 nm, with excitation at 494 nm. The intensity was stable for at least 2 h in the tightly stoppered flask. The determination limit of anthraquinone was 100 ng. By the application of this spectrofluorimetry, anthraquinone in 9,10-phenanthrenequinone could be successfully determined over the content range from 0.2 to 4%.

Spectrophotometric determination of zirconium in geological materials with Xylenol Orange.

A rapid and accurate method for the determination of Zr in geological materials is presented. The interference of F- was reduced by masking with Al+, and Fe3+ was reduced to Fe2+ with hydrazinium dichloride. A sample (0.2 g) was decomposed with a mixture of HNO3, HClO4 and HF, and the solution was evaporated to dryness. Then the dried sample was fused with a mixture of 2 g Na2CO3 and 0.3 g H3BO3, and the melt was dissolved in 17 ml of HCl (1 + 1), and it was diluted to 50 ml with water. Fifteen ml portion of the sample solution was transferred to a 50 ml volumetric flask. To it, 8 ml of Al chloride solution (Al3+ 25 mg/ml) and 5 ml of hydrazinium dichloride solution (15 w/v%) was added. The solution was heated in boiling water for 15 min. After cooling, 5 ml of Xylenol Orange solution (0.1 w/v%) was added and diluted up to the mark with water. Absorbance was measured at 535 nm. Ten samples could be analyzed in 5 h. This method was satisfactorily applied to a variety of geological reference materials.

More Powerful Peroxide Kjeldahl Digestion Method

Abstract Enhanced ammonia recovery and a simplified method are described for a rapid Kjeldahl digestion using sulfuric acid and hydrogen peroxide as the sole digestion reagents. This micro procedure uses a Vigreux fractionating head fitted to a 100 mL volumetric flask and a hot plate with a solid-state controller. Continuous-flow peroxide addition is controlled by a capillary funnel, and fumes are evacuated through a side-arm vent leading to a water aspirator. Complete recovery of nitrogen from the refractory compound, nicotinic acid, is obtained with less than 10 min digestion. The described method reduces digestion time by 25-50% over the open-manifold peroxy method. A digestibility index (DI), scaled 0-10, establishes the difficulty of digestion for each sample and assigns values to compounds. A useful tool for determining the minimal amount of reagent and digestion time required, the DI assigns zero for compounds not needing digestion and 10 for nicotinic acid. Digested samples obtained from the described method are suitable for direct colorimetric analysis of many elements in addition to Kjeldahl nitrogen. Distillation of the digested sample is not required

Ozonation des bases puriques en milieu aqueux: etudes cinetiques de la reaction

The kinetics of the action of ozone on purines and on pyrimidines have been the object of relatively few studies. According to Ishizaki et al. [ Chem. pharm. Bull. 29, 868–872 (1981)], the reaction of ozone on guanine is the fastest, whereas on adenine it is the slowest. There are few works concerning the ozonation of nitrogenous heterocyclic compounds [Doré, Symposium International “Ozone et Biologie”, Rennes (1984); Guyon, Thèse de Doctorat, Université de Poitiers (1984)]. However, it would seem that nitrogenous heterocyclic compounds with five centres and one nitrogen atom react more rapidly with ozone than those with six centres. The direct reaction of ozone on adenine, guanine and purine, in aqueous solutions was studied. For each compound the stoichiometric factor of the reaction, the kinetic law, and the rate constant value were determined. Moreover, the value of activation energy of the purine ozonation was evaluated. The study of the kinetics was carried out with a phosphate-carbonate buffer at pH = 7.6 ± 0.05 and ionic strength I = 0.2 mol 1 −1. Bicarbonates ([HCO 3 −] = 10 −2 mol 1 −1) acted as radical scavengers. The reactions occurred in small volumetric flasks (25 cm 3) where ozone in buffered solution was introduced with a syringe. Initial and final ozone concentrations were determined with indigo disulfonate, following the method indicated by Bader and Hoigné [ Wat. Res. 15, 449–456 (1981)]. Purines were dosed by HPLC analysis (Table 2). For each compound, a two order kinetic law was found: − d[C] dt = k c·[0 3]·[C] where C = organic compound. Purine (Pu). Ozonation consumes 4 mol O 3 mol −1 of purine (Fig. 1). The reaction order concerning purine was degenerated so as to accelerate the reaction rate. Table 3 gives the results and Figs 2(a) and (b) show two examples of curves and the kinetic exploitation. The average rate constant value was found to be: k Pu (20°C) = 7.9 ± 0.71 mol −1 s −1 ( pH = 7.6; [ HCO − 3] = 10 −2 mol 1 −1 . The same experiments carried out at different temperatures (2 and 10°C; Fig. 3) allowed us to determine the value of activation energy ( E = 15.3 kcal mol −1). This result is similar to those mentioned by Hoigné and Bader [ Wat. Res. 17, 173–183 (1983)] for ozonation of organic compounds (8 ⩽ E ⩽ 12 kcal mol −1). Adenine (A). This compound reacts very rapidly with ozone, so the reactions had to occur at 2°C. The stoichiometry was 2 mol O 3 mol −1 of adenine (Fig. 4). Table 5 gives us the rate constant values obtained at 2°C; Figs 5(a) and (b) show two examples of ozone consumption and the kinetic exploitation. The average rate constant value is: k A(2°C) = 2200 ± 550, 1 mol −1 s −1 ( pH = 7.6; [ HCO − 3] = 10 −2 mol 1 −1 . Guanine (G). The stoichiometry was difficult to determine. It is probably 1 mol O 3 mol −1 of guanine. The competitive kinetic method, between adenine and guanine at 2°C (Fig. 6), gave: k G k A = 1.6 ± 0.1 (r 2 = 0.973) . So we could calculate k G as: k G(2°C) = 3500 ± 1100, 1 mol −1 s −1 ( pH = 7.6; [ HCO − 3] = 10 −2 mol 1 −1 .

Determination of Ergotamine Tartrate in Tablets by Liquid Chromatography with Fluorescence Detection

A method is presented for the liquid chromatographic (LC) determination of ergotamine tartrate in tablets that is applicable even in the presence of other ingredients such as phenobarbital, belladonna alkaloids, and caffeine. The sample is transferred to a volumetric flask, a small volume of formic acid is added to dissolve and stabilize the ergotamine, and the solution is diluted to volume with methanol. The solution is mixed and filtered through paper. The LC system consists of a Rheodyne injector fitted with a 20 microL loop and a C18 reverse phase column; the mobile phase is acetonitrile-water-triethylamine (700 + 300 + 0.5). Ergotamine tartrate is determined fluorometrically at an excitation wavelength of 250 nm and an emission wavelength of 430 nm. Recovery studies were conducted at the 0.3 and 1.0 mg levels. Average recoveries were 99.6 and 100.8%, respectively; relative standard deviations (RSDs) were 1.08 and 2.21%, respectively. Some commercial preparations containing ergotamine tartrate in combination with other ingredients were also analyzed. The RSDs for 5 determinations of each of 2 ground composites were 0.09 and 0.34%.

Determination of nitrate ion content in recirculating water in petroleum refineries and petrochemical plants

A method for determining nitrate ions, using a 2,6-diacetaminopyridine solution in concentrated sulfuric acid, was investigated. Potassium nitrate solutions with nitrate ion contents of 1 mg/ml, including a 2% aqueous solution of sulfamic acid, a 0.5% solution of antimony trioxide in concentrated sulfuric acid, were used. The solutions were mixed with a 1-4 ml sample of recirculating water in two 25 ml flasks. The optical density of the solution was measured relative to the zero standard of the scale of the calibration curve. Nitrate ion content was measured by the calibration curve, from data obtained in a series of 25-ml volumetric flasks.

Stability of aqueous solutions of amoxicillin sodium in the frozen and liquid states

The stability of aqueous admixtures of amoxicillin sodium in both the liquid and frozen (solid) states was studied. Admixtures of amoxicillin sodium were prepared in sterile water for injection to a theoretical concentration of 10 mg/mL. For each experimental run, 2-mL aliquots of the admixture were placed in stoppered glass volumetric flasks and stored at temperatures ranging from 19.5 degrees C to -30 degrees C; 16 flasks were stored at each temperature. After equilibration for approximately 20 minutes, duplicate flasks at each temperature were removed from storage conditions for time-zero assay. Subsequently, duplicate flasks were assayed at various times, depending on the storage temperature, for up to 13 days or until more than 80% of the drug had degraded. All samples were assayed at least in duplicate using high-performance liquid chromatography. When amoxicillin solutions were in the liquid state (at temperatures between 19.5 and 0 degrees C), the time required for the amoxicillin concentration to decrease to 90% of its initial value (t90) increased as temperature decreased. However, between 0 degree C and -7 degrees C, the t90 of frozen solutions decreased from two days to 1.08 hours. As temperature declined further, the rate of degradation decreased until the solution was completely frozen; at -30 degrees C, the t90 had increased to 13 days. Amoxicillin sodium is unstable in aqueous solutions stored between 0 degrees C and -20 degrees C. If admixtures of this drug are to be frozen for later use, the storage temperature should be below -30 degrees C.

35] Spectrophotometric determination of iron in heme proteins

The spectrophotometric determination of iron in aqueous solutions relies on the formation of stable iron(II) complexes possessing a high absorptivity in the visible region of the spectrum. The majority of sensitive iron ligands have been compounds possessing the ferroin group—that is, the group which acts as a bidentate ligand toward iron (II), including 1,10-phenanthroline derivatives such as bathophenanthrolinesulfonic acid and triazine derivatives such as 2,4-bis pyridine tetrasulfonic acid. A method for the digestion of heme protein samples to liberate the iron completely from the heme groups consists of placing a heme protein sample in solid form or solution not exceeding 0.1 ml and containing 10–50 μ g of iron, into a 10-ml volumetric flask. After addition of 0.1 ml of perchloric acid (70%) and 0.1 ml of 30% hydrogen peroxide solution the sample is digested at 100° for 30 min. At this point there must not be any precipitate and the solution should have a pale straw yellow color. If necessary, additional 0.1 ml quantities of the perchloric acid and the hydrogen peroxide solution can be added and the time of digestion extended. The sample is then ready for the complexometric determination of iron. A procedure for hemoglobin iron analysis has been developed in which treatment with 2.5% sodium hypochlorite was used to liberate the iron. The procedure using 1,10-phenanthroline, provides a very reliable method for the determination of iron in a variety of hemeproteins and other iron-containing materials. A simple procedure has been developed of digesting the heme protein sample and 4-(2-pyridylazo)resorcinol (PAR) as the complexometric reagent at alkaline pH.

A two-liter pipet for bomb calorimetry

A 2-L volumetric flask modified to deliver a constant volume of water at a constant temperature.

Growth dynamics of Olisthodiscus luteus in outdoor tanks with flowing coastal water and in small vessels

Growth rates and periodicity of division of Olisthodiscus luteus were studied in outdoor tanks provided with a continuous flow of coastal water carrying a low density of wild plankters including O. luteus, during summer in 1981–1983. Cells collected from the tanks were individually cultured in small tissue culture chambers in the laboratory to observe growth rates and periodicity of division. A portion of an O. luteus patch on the wall of the tank was also cultured in a 1,000‐m1 volumetric flask hung in the tank. High growth rates, 2.0–5.0 div d−1, were observed in the tank. There was a strong tendency for large cells to dominate in the tank at the beginning of their fast growth phases and to be replaced by small cells toward the end of these growth phases. In small chambers O. luteus attained a growth rate of 3.3 div d−1; growth rates of large cells inoculated into these chambers were much higher than those of small cells. Growth rate in the flask was 2.3 div d−1. Olisthodiscus luteus showed a great preference for dark‐associated cell division. An apparent reciprocal codominance was observed between O. luteus and diatoms in the tank.

Improved device for direct transfer of filtered liquids to volumetric flasks

A device for direct transfer of filtered liquids to volumetric flasks has been modified to improve time savings and simplify operational procedures.

Stability of Aminophylline Injection in Three Parenteral Nutrient Solutions

The stability of aminophylline injection in crystalline amino acid-dextrose solutions containing standard additions of electrolytes, vitamins, and minerals was evaluated. Aminophylline injection was added to three parenteral nutrition (PN) solutions in dosages of 0.25-1.50 mg/ml. All of the samples were prepared in duplicate, stored in sealed volumetric flasks, and allowed to stand under normal lighting at room temperature or under refrigeration for 48 hours. Samples were analyzed for theophylline content by reverse phase high-pressure liquid chromatography at 1, 24, and 48 hours. Mean percent theophylline recovery 24 hours after admixture was 101 +/- 10.9%, 101 +/- 4.3%, and 100 +/- 4.3% in the three PN solutions. Solution pH values were stable for 48 hours. Refrigeration and lower amino acid concentrations did not alter stability. Aminophylline is stable in PN solutions for 24 hours in concentrations up to 1.5 mg/ml.

A field electrode method for the determination of sulfide

This paper reports the development of a field electrode method for the determination of total sulfide in water. The method involves the use of preweighed sodium sulfide crystals in the standardization process. Sodium sulfide crystals were weighed and sealed in air-tight plastic volumetric flasks. Standards were prepared in the field by adding a sulfide antioxidant buffer to the flasks containing the sulfide crystals and diluting it to mark with deionized deaerated water. Standards of lower concentration were prepared by serial dilutions of first standards. The results of the reproducibility determination revealed that sulfide concentrations as low as 6 ppb could be measured with a reproducibility of better than ±10%. Water samples were collected from a series of lakes in Fort Bend County, Texas (near Houston) and analyzed for sulfide content. The sulfide ion concentrations of these samples were determined directly in the field by use of an Orion Model 407A/F specific meter equipped with a silver/sulfide ion selective electrode in conjunction with a double junction reference electrode.

Monoterpenoid Content of Pygmy Rabbit Stomach Ingesta

Monoterpenoid Content of Pygmy Rabbit Stomach Ingesta

Spectrophotometric determination of palladium(II) with Sulfochlorophenol S

A spectrophotometric method is described for the determination of palladium (II) with Sulfochlorophenol S (abbreviated as SCPS). SCPS reacts with palladium in acidic medium to form a blue colored complex. The maximum absorption of the complex is at 643 nm (against the reagent blank). Recommended procedure is as follows: Into a 25 cm3 volumetric flask transfer a sample solution containing less than 64 μg of palladium. Add 10 cm3 of 2× 10-4 mol dm-3 SCPS solution, 1 cm3 of 0.25 mol dm-3 perchloric acid, and 1 cm3 of 2.5 mol dm-3 sodium perchlorate solution; dilute to about 20 cm3 with distilled water. Support the flask in boiling water for five min. Cool to room temperature, dilute to the mark with water. Measure the absorbance at 643 nm against the reagent blank prepared with the same method to do the sample. Beer's law was applied in the range up to 64 μg of palladium. The apparent molar absorptivity was 4.2 × 104 dm3 mol-1 cm-1, and the Sandell's sensitivity of the reaction was 0.0025 μg cm-2. Chloride, nitrate, and sulfate did not interfere at 3000-fold ratio to palladium. Fluoride and tartrate (1000-fold to palladium), platinum (IV) (200-fold) did not interfere with the determination.

Assessment of glomerular filtration rate using single injection of technetium Tc 99m pentetate.

In situations where complete urine collections are difficult to obtain, single-injection methods have been recommended for the assessment of glomerular filtration rates (GFRs) without recourse to urine collections. 1-6 These methods have generally used millicurie doses of isotope or smaller doses and scanning equipment. This report describes the effectiveness of technetium Tc 99m pentetate at a dose of 1 to 2 μCi/kg for the assessment of GFR. Methods .—The technetium Tc 99m pentetate was prepared from a commercial kit, diluted to 1 to 2 μCi/kg in approximately 3 mL of physiologic saline, and placed in a plastic syringe. After weighing the syringe on an analytical balance, 0.1 mL was injected into a 100-mL volumetric flask for use as a counting standard, and the syringe was reweighed. The remaining solution was injected into the subject's vein through a butterfly needle, the butterfly was flushed with 10 mL of saline, the time

A new transfer flask for quantitative analysis

The authors describe a new flask that has been designed for use in the quantitative transfer of a solution into the narrow neck of a volumetric flask.