Semi-micro Method Research Articles

The sodium 5-butyl-1,2-diphenyl-6-oxo-1,6-dihydropyrimidine-4-olate quantitative content determination in a standard sample

Introduction. The standard samples (SS) use is a necessary condition for the medicines' quality control implementation. Their development is an urgent problem for the pharmaceutical industry, especially for new biologically active compounds that can be further used as pharmaceuticals.Aim. This work aim is to establish the 5-butyl-1,2-diphenyl-6-oxo-1,6-dihydro pyrimidone-4-olate sodium quantitative content, for which anti-inflammatory and analgesic activity was previously proven, in a standard sample.Materials and methods. This work aim is to establish the 5-butyl-1,2-diphenyl-6-oxo-1,6-dihydro pyrimidone-4-olate sodium quantitative content, for which anti-inflammatory and analgesic activity was previously proven, in a standard sample. The main method for establishing a substance quantitative content in the SS is the material balance method. The water determination was carried out according to K. Fisher's method (semimicro method). Sulphated ash was determined according to the XIV edition Russian Federation State Pharmacopoeia General Pharmacopoeia Monograph "Sulphated ash". Related impurities and their content were assessed using the HPLC method on a Flexar liquid chromatograph equipped with a diode array detector (Perkin Elmer, USA). The residual solvents' determination was carried out by the headspace method using a gas chromatograph GC-2010Plus Shimadzu with a flame ionization detector. As an additional method for establishing the main component quantitative content, acidimetric titration with the equivalence point potentiometric indication was carried out.Results and discussion. The percentage was determined for the following indicators: water, residual organic solvents, related impurities, sulphated ash. Using the material balance method, it was found that the 5-butyl-1,2-diphenyl-6-oxo-1,6-dihydropyrimidin-4-olate sodium percentage in a standard sample is 96.01 ± 0.50 %. It was found by acidimetric titration that the 5-butyl-1,2-diphenyl-6-oxo 1,6-dihydropyrimidin- 4-olate sodium quantitative content in SS is 95.12 ± 0.02 %. The difference in the certified value can be explained by the fact that during titration, the SS aciform is released, which precipitates in an aqueous medium and contributes to a shift in the equilibrium and pH value. Consequently, the equivalence point is reached somewhat earlier. However, the data are practically comparable, but it is necessary to use the value obtained by the material balance method.Conclusion. A standard sample certification parameters were determined: water content, residual organic solvents, sulphated ash, related impurities. The main component quantitative content was determined using the material balance method and titrimetry (acidimetry with the equivalence point potentiometric indication).

Study of factors affecting the in vitro release of diclofenac sodium from hypromelose-based gels

The aim of our study was to identify factors affecting the in vitro release of diclofenac sodium (DS) from hypromellose-based gels (HPMC).
 Materials and methods. Gels with HPMC and liquids without HPMC were studied by viscosity-rotating viscometer method and spin probe electron paramagnetic resonance spectroscopy. Rheograms were used to determine the flow behavior and the apparent viscosity, and the EPR spectra were used to determine the rotational correlation time (τ–1) of the dissolved spin probes. The in vitro release tests were performed using vertical diffusion cells according to a validated procedure. The assay of DS and isopropyl alcohol (IPA) in the receptor medium was performed by high performance liquid chromatography (HPLC) and gas chromatography (GC) according to validated procedures, and the water content was determined using semi-micro method.
 Results. The apparent viscosity of the gels increased with increasing HPMC content and depended on the HPMC grade. The high apparent viscosity of the gels did not affect the values of τ–1 of the dissolved spin probes. In viscous gels and Newtonian fluids, the composition of which corresponded to the dispersion medium of gels, the values of τ–1 were identical and were in the range of rapid rotation, which is a prerequisite for similar and rapid release of the dissolved substances from gels and liquids. It was shown that the HPMC-based gel and Newtonian liquid without HPMC in terms of in vitro release parameters DS and IPA were equivalent. During in vitro testing the release of dissolved DS increased with increasing its concentration in the gel and depended on the dispersed state of DS. When the content of IPA was changed from 45.0 % to 22.5 %, the water absorption by the gel and the release of IPA decreased, and the release of DS increased, which was due to the decrease in the solubility of DS in the gel.
 Conclusions. HPMC, which provided high apparent viscosity of the gels, did not affect the value of τ–1 of the dissolved spin probes and the in vitro release of DS from the gels. The gel and Newtonian liquid were equivalent in terms of in vitro release of DS and IPA. The release of DS altered proportionally with the concentration of DS and depended on its dispersed state. As the content of IPA decreased, the release of IPA decreased, but the release of DS increased because of the decrease in the solubility of the DS in the gel

Utilization of Shrimp Waste as a Raw Material in Shrimp Sauce and Its Application on Shrimp Sauce Tilapia Dishes

One of the innovations to increase the economic value of shrimp waste is the implementation of shrimp waste into shrimp sauce and its use in shrimp sauce tilapia dishes. The purpose of this study was to determine the protein and lead (Pb) content of shrimp waste and shrimp sauce, the degree to which shrimp sauce differed in aroma, taste, and color from commercial oyster sauce, and the degree to which panelists preferred shrimp sauce tilapia dishes via organoleptic tests. This was a two-repetition experimental study with a completely randomized design (CRD). The protein content was determined using the Kjeldahl semi-micro method, whereas the lead content was determined using the spectrophotometric method. The Duo-Trio Test was used to determine the difference in organoleptic properties between shrimp sauce and commercial oyster sauce, whereas ANOVA followed by DMRT was used to analyze the hedonic properties of shrimp sauce tilapia dishes. The results of this study indicate that shrimp waste contains 18.281 percent protein and shrimp sauce contains 6.107 percent protein. The content of lead (Pb) in shrimp waste was 0.750 mg/kg, while the content of lead (Pb) in shrimp sauce was 0.052 mg/kg. The organoleptic tests revealed that shrimp sauce had a distinct aroma, taste, and color from commercial oyster sauce, whereas the hedonic tests revealed no difference in the hedonic properties of the three dishes' aromas, but there were differences in the hedonic properties of their taste and properties. The three dishes exhibit hedonic color. Panelists preferred commercial oyster sauce tilapia dishes over shrimp sauce tilapia dishes and commercial oyster sauce mixed tilapia dishes in terms of aroma, taste, and color (1:1). The shrimp sauce formula should be refined further so that it more closely resembles commercial oyster sauce in terms of aroma, flavor, and color.

Malacosoma neustria Larvalarına Farklı Sekonder Maddelerin Sinerjistik Etkisi

Bu çalışmada polifag bir tür olan Malacosoma neustria‘nın son larva döneminde toplam diyet tüketim miktarı, pupa ağırlıkları, pupaların lipit ve protein miktarları ve gelişme sürelerine sekonder maddelerin sinerjistik etkisi araştırılmıştır. Kontrol diyetine farklı konsantrasyonlarda (%1, 3, 5) tanik asit, galik asit ve p-Kumarik asit katılarak 9 diyet hazırlanmıştır. Kontrol diyetine %3 konsantrasyonda tanik asit, galik asit ve p-Kumarik asit katılarak ikili kombinasyonlu 3 diyet hazırlanmıştır. Üçlü kombinasyonda bir diyet yapılarak toplamda 14 diyet ile tercihsiz beslenme deneyi yapılmıştır. Lipit miktarının belirlenmesinde kloroform kullanılmıştır. Protein analizi semi-mikro Kjeldahl metodu ile Kjeltec Auto 1030 analizörü (Tecator, Sweden) ile yapılmıştır. İstatistik analizlerde ANOVA-Dunnet testi kullanılmıştır. Kontrol grubuna göre hem tanik asit hem de p-Kumarik asit içeren diyetlere ilave edilen madde konsantrasyonu arttıkça, M. neustria larvalarının toplam diyet tüketim miktarlarında, pupa protein ve lipit miktarlarında azalma olduğu bulunmuştur. Gallik asit ilave edilen diyetlerde gallik asit konsantrasyonu arttıkça toplam tüketim miktarının arttığı belirlenmiştir. Diyete ilave edilen tanik asit konsantrasyonu arttıkça gelişim süresinin uzadığı bulunmuştur. Bu çalışmada kullanılan sekonder maddelerin ilgili konsantrasyonlarına ve kombinasyonlarına larvaların dirençli olduğu ve pupa dönemine ulaşabildikleri gözlemlenmiştir.

Comparative analysis the frequency and spectrum of chromosome aberrations in irradiated in vitro peripheral blood lymphocytes of the elderly and centenarians from Kyiv

To establish and compare the frequency and spectrum of chromosome aberrations under X radiation exposure in vitro in dose 0.25 Gy peripheral blood lymphocytes of the elderly and centenarians. Material of cytogenetic research were peripheral blood lymphocytes from 11 elderly and 10 centenarians, which were irradiated in vitro in dose 0.25 Gy and cultured by generally accepted semi micromethod; slides of metaphase chromosomes were GTG stained and analyzed under the microscope with magnification x 1000. Under irradiation of blood in vitro the mean group frequencies of chromosome aberrations exceeded such without irradiation (р < 0.001) and were 11.60 ± 0.95 аnd 6.82 ± 0.63 per 100 cells in the elderly and the centenar ians, accordingly. Radiation induced increase in the frequency of chromosomal injuries occurred due to chromo some type aberrations which are markers of radiation exposure. In the elderly the elevated frequency of chromatid type aberrations also was registered what is considered a sign of chromosome instability. The results indicate increased sensitivity the blood lymphocytes from the elderly to radiation expo sure in low doses and allow to assume the advantage of persons with hereditary determined chromosomal stability in achieving longevity.

Development, Characterization and Acceptance of Fruit-Bread Biomass Green Brownie

Objective: This study aimed to develop and characterize a green breadfruit biomass brownie. Methods: We developed a brownie made with green breadfruit biomass to the detriment of traditional ingredients: flour and butter. We analyzed five replications on the chemical composition (moisture volatile at 105℃; ashes by calcination; ether extract Soxhlet; protein by the semi-micro Kjeldahl method; starch by Lane-Eynon method) as methodologies recommended by the Adolfo Lutz Institute [1], except the fiber, which was quantified by the method proposed by Van Soest [2]. It was further determined the antioxidant capacity (DPPH) and the content of total phenolic compounds (Folin-Ciocalteu reagent). The brownie was developed subjected to sensory analysis 100 untrained and the result was compared to a traditional version and two trademarks brownie gluten and lactose. Results: On the chemical composition, fiber is an important fraction in developed brownie (12.07 ± 0.29). For antioxidant capacity, Brownie showed excellent results (DPPH: 85% and 654.76 ± 4.10 mg/100g of gallic acid equivalent) greater than some fruits studied by other authors. The product was developed sensory well accepted, with higher acceptance rate to 70% in the overall assessment. Conclusion: It was concluded that there viability in production brownie green breadfruit biomass since proved to nutritional appeal even higher than others, with which it was compared, and was well accepted sensorially. One formulation optimization study might be interesting to improve Brownie texture.

The nutrient accumulation pattern and cycling in natural secondary forests in North China. A case study from the Caijiachuan watershed, Shanxi Province

In order to examine the nutrient content, and the distribution and accumulation patterns of individual nutrients in the natural secondary forests (NSFs), sample NSF plots were selected in the Caijiachuan watershed on the Loess Plateau. On the basis of a comprehensive field inventory to the NSFs in Caijiachuan watershed, a 40 m × 40 m sample plot was selected as the representative plot. Each tree plant was then measured to select the standard tree in accordance with a diameter-scale. For measurement of the biomass in the above-ground part of the tree, it was divided into parts and measured. The study measured the concentration of the 5 major macronutrients (namely N, P, K, Ca and Mg) and the 8 major micronutrients (namely Cd, Fe, Mn, Cu, Zn, Pb, Ni and B) in plant organs. An appropriate amount of the samples were weighed and exposed to H2SO4-H2O2 using the Kjeldahl heating digestion method. While N content was measured with the semi-micro determination method, P content was measured using vanadium molybdate yellow colorimetric method HNO3-HClO4 ICP heating digestion method was applied to determine the contents of Ca, Mg, K, Na, Fe, Cu, Zn, Mn, B, Cd, Pb, Ni. As for soil samples, corresponding approaches were employed to work out the contents of each of the above-mentioned nutrient elements. Among the tree, shrub and herbaceous layers, the content of macro-nutrients follows the sequence of Ca > N > K > Mg > P, compared with their counterpart of K > N > Ca > P > Mg in the litter layer. For the micronutrient contents, similar sequences (i.e., Fe > Mn > Zn > B > Cu > Pb > Ni > Cd) were observed in the tree, shrub and litter layers; whereas the herbaceous layer demonstrated a different sequence of Fe > Mn > B > Zn > Cu > Pb > Ni > Cd. Within the NSF ecosystem, total accumulation of the 5 major macronutrients (excluding that in the soil) reached 1089.82 kg/ha, of which the tree layer took up the largest share, 40.82%, followed in turn by the shrub layer (31.28%), the herbaceous layer (12.55%) and the litter layer (15.36%). In terms of nutrient-concentration in the plant organs within the tree layer, the overall sequence can be expressed as branches > roots > wood > bark > leaves. The total accumulation of the 5 major macro-nutrient in the soil reached 634.97 t/ha. In terms of the accumulation coefficients in each of the layers, the general pattern can be summed up as: shrub layer > tree layer > herbaceous layer, and N > P > Ca > K > Mg. In terms of the plant organ accumulation coefficients at the tree layer, the sequence was leaves > branches > roots > bark > wood. As for the accumulation coefficients of the micronutrients, the overall sequences for the tree layer, the shrub layer and the herbaceous layer can be listed as Cd > B > Zn > Cu > Mn > Ni > Pb > Fe; Cd > B > Zn > Mn > Cu > Ni >Pb > Fe and Cd > B > Mn > Zn > Cu > Ni > Pb > Fe, respectively. The study also revealed that the macronutrients that are absorbed, assimilated and returned by the NSF stand annually reached 99.054kg/(ha·year), 49.155 kg/(ha·year) and 49.899 kg/(ha·year), respectively, demonstrating a well-balanced state of nutrient cycling. With an average of 0.0013, the absorbance index of the macro-nutrients was ranked in the following sequence, N > P > K > Ca > Mg; whereas their utilization and cycling indexes were respectively sequenced as K > P > N > Mg > Ca and K > P > N > Mg > Ca. For the micronutrients the corresponding annual figures were 117.35 g/(ha·year), 50.96 g/(ha·year) and 66.39 g/(ha·year), respectively. The micronutrients, as a whole, showed a relatively small absorbance index (e.g.,Cd was the largest =0.0036). The average utilization index of all the microelements was 0.12.

Simple spectrophotometric method for determination of polyvinylalcohol in different types of wastewater

The determination of polyvinylalcohol (PVA) by the formation of the blue iodine–PVA complex method was established for a semi-micro method scale. The direct addition of iodine solution proved to be a better iodine source than iodine generated in situ. The ageing of reagents requires frequent calibrations. Common biopolymers such as starch, albumin and cellulose produced much lower colour intensity with reagents and their impact on the analysis is negligible. The method is not affected by paper filter filtration. The detection of PVA was successfully tested in different wastewater types and the method proved to be a powerful tool for PVA detection. It must be emphasised that quantification of PVA is strongly dependent on the PVA type and the quantification capacity; without information of the PVA structure or type is only tentative.

Semimicro Determination of COD Employing Microwave Digestion

A modified semimicro method is described for determining chemical oxygen demand (COD) employing microwave (MW) digestion (0.5 min exposure at 1,000 W power, and 10 min exposure at 250 W power) with a titration assessment. Composition of reaction mixture was the same as that of the usual reflux method. Determination was performed in glass vessels of original tetrafluoromethoxil containers. Under given conditions dichromate autoreduction was low. A good agreement with the usual reflux method was obtained with selected substances (potassium hydrogen phthalate, glutamic acid, glucose, dodecyl sulphate, where COD-MW/ThOD is 98.9–101.5%). With real samples (municipal sewage, mixed tanning and chemical wastewaters, and treated wastewater from biological treatment plants) the obtained results were also satisfactory (88.0–111.9%).

Analysis of tofisopam in human serum by column-switching semi-micro high-performance liquid chromatography and evaluation of tofisopam bioequivalency.

A rapid and sensitive column-switching semi-micro HPLC method is described for the direct analysis of tofisopam in human serum. The sample (100 microL) was directly injected onto the precolumn (Capcell Pak MF Ph-1), where unretained proteins were eluted to waste. Tofisopam was then eluted into an enrichment column using 13% acetonitrile in 50 mM phosphate buffer (pH 7.0) containing 5 mM sodium octanesulfonate and subsequently into the analytical column using 43% acetonitrile in 0.1% phosphoric acid containing 5 mM sodium octanesulfonate. The detection limit (2 ng/mL), good precision (CV < or = 4.2%) and speed (total analysis time 24 min) of the present method were sufficient for drug monitoring. This method was successfully applied to a bioequivalence test of two commercial tofisopam tablets.

Urinary Glycosaminoglycan Excretion Quantified by an Automated Semimicro Method in Specimens Conveniently Transported from Around the Globe

Current and future treatments for children with mucopolysaccharidosis (MPS) diseases require early, presymptomatic diagnosis, yet existing diagnostic methods to quantitate urinary glycosaminoglycan (GAG) are labor-intensive, and thus not applicable for newborn screening. Direct and rapid quantification of GAG excretion with 1,9-dimethylmethylene blue (DMB) is applicable to small volumes of urine collected, dried, and mailed on a paper matrix (MPS Test). To determine if this assay could be automated, a robotic instrument was programmed to accomplish the procedure; the pilot method simultaneously determined GAG and creatinine concentrations in 10 patient specimens/run. Each analyte is measured in 4 dilutions, thus increasing the operating range to cover a broad spectrum of normal and pathologic levels. Samples and reagents are mixed in a 96-well tray format in approximately 20 min, and densitometric measurements are recorded in less than 60 s. Optical density measurements are electronically transmitted to a desktop computer to select optimal dilutions, identify values above or below the level of reliability, make calculations, and print reports. This automated method was applied to 255 specimens from 101 subjects representing each of the MPS diseases—specifically, types I (n = 126), II (n = 47), III (n = 48), IV (n = 17), VI (n = 14) and VII (n = 3). This method discriminated pathologic elevations of GAG excretion of MPS patients particularly when multiple specimens were available. Patients with non-MPS lysosomal diseases had normal GAG excretion, except for a patient with fucosidosis who had markedly elevated levels. Automation of the direct DMB method provides the key technology necessary for newborn screening for MPS diseases.

New ultrasound assisted chemical oxygen demand determination

A new method for the chemical oxygen demand (COD) determination assisted by ultrasonic radiation has been evaluated for the first time. The suggested method uses an instrumentation simpler and cheaper than the previous ones used for the same purpose. With this preliminary version of the method the optimized experimental conditions are: high ultrasonic power (143 W, 95% of maximum nominal power; 126.5 W/cm 2 of power density); high sulphuric acid concentration (>60%); and a sonication time of 2 min. Under these conditions this first prototype shows the same limitations as the official COD method as regards the type of organic compounds. It works successfully with easily oxidative organic matter (sodium oxalate, glucose and salicylic acid) but the COD values obtained with more difficult organic matter are poor. When the ultrasonic assisted method is applied to real waste waters the precision is statistically not different to that of the conventional semi-micro method but the COD values obtained lie between 50 and 60% of the values obtained with the conventional semi-micro method. Hence, the use of the ultrasonic radiation for COD determination seems to be an interesting and promising alternative to the conventional ones but still much more research efforts must be done in order to improve the instrumental set-up. The suggested direction of these developments must be a more efficient interaction between the ultrasonic radiation and the sample.

Miniaturized solid-phase extraction with resin disks

The properties and advantages of membrane disks for solid-phase extraction (SPE) are described. Miniaturization is a trend in SPE, as well as chemical analysis in general. A semimicro method is reviewed in which an extraction disk 4 mm in diameter is used for SPE. Even smaller scale separations are possible with a device in which a membrane 0.7 mm in diameter was incorporated into the needle of a 50-μl syringe. Aqueous samples containing 10 ppb of eight substituted benzenes were passed through the miniaturized-SPE syringe automatically using a single-syringe infusion pump. Elution volumes of 5 μl provided 500-fold concentrations and delivered average recoveries greater than 90% and an average relative standard deviation (RSD) of 4.6% for the analytes. Direct injection of the 5 μl eluate from the miniaturized-SPE syringe into a gas chromatograph also produced average recoveries greater than 90% and an average RSD of 6.2%.

A simple, rapid and sensitive semimicro method for the measurement of cyanide in blood.

Conventional methods do not meet the clinical need for rapid cyanide measurements. We report a procedure which can provide a result in 10 min. It should be of particular interest to laboratories serving cardiac or renal units which use the hypotensive agent sodium nitroprusside, and burns units to which fire victims may be admitted suffering the effects of HCN from inhaled smoke. A sample of blood (100 microL) is mixed with H3PO4, containing a surfactant, and the HCN is trapped in an alkaline mixture of 1,2-dinitrobenzene and 4-nitrobenzaldehyde in 2-methoxyethanol. The catalytic action of cyanide, which produces purple 2-nitrophenylhydroxylamine, is stopped with acetone after 6 min. The absorbance measured at 560 nm shows a linear relationship with the cyanide concentration, but the slope varies with the ambient temperature. Since KCN added to both 50 mmol/L NaOH and blood gives similar assay results, any inaccuracy arising from changes in temperature can be avoided by running standards at the same time as the blood sample.

Preparative thin-layer chromatographic separation and subsequent gas chromatographic–mass spectrometric analysis of monoacylglycerols derived from butter oil by fungal degradation

A semi-micro method has been developed using preparative thin-layer chromatography (TLC) to separate acylglycerols for the subsequent analysis by gas chromatography–mass spectrometry (GC–MS). Monoacylglycerols (MAGs) were formed from butter oil by fungal degradation with Penicillium roquefortii. Total lipids were extracted with hexane–2-propanol (3:2, v/v) and separated on silica gel preparative TLC plates with fluorescence indicator (Merck). The plates were developed in hexane–diethyl ether–formic acid (80:20:2, v/v). Lipid bands were detected under UV light or with iodine vapour, removed and then extracted with hexane–2-propanol (3:2, v/v). The MAG band ( R F 0.03) was silylated into trimethylsilyl (TMS) ethers. Structures and composition of MAG-TMS ethers were analysed by GC and GC–MS. Formation of characteristic ions for the identification of sn-1(3)- and sn-2-MAG isomers was discussed. The method is simple, inexpensive and powerful for the separation and analysis of relatively small amounts of MAGs (0.2–5.0 mg) formed from fungal degradation.

Rapid determination of chemical oxygen demand by a semi-automated method based on microwave sample digestion, chromium(VI) organic solvent extraction and flame atomic absorption spectrometry

In the present work, a new flow injection analysis (FIA) manifold for the rapid determination of chemical oxygen demand is presented and evaluated. The FIA manifold combines sample digestion by means of an oxidant solution (i.e., potassium dichromate and mercury sulfate) and an acid solution (sulfuric acid and silver sulfate) in a domestic microwave oven with the liquid–liquid extraction of Cr(VI) with tributyl phosphate (TBP). Finally, the remaining (non-reduced) Cr(VI) is determined in the organic phase by atomic absorption spectrometry. The digestion of the organic matter is carried out in the stopped-flow mode. Potassium hydrogenphthalate has been used for optimization of the method and as a standard to check its performance. The optimized conditions (oxidation) are: digestion time, 7 min; acid concentration, 67% (v/v). The optimized conditions for the extraction of the remaining Cr(VI) are: acid concentration, ≥30% (v/v); TBP, 1 ml. The proposed method has been successfully applied, with the exception of pyridine, to several organic compounds and waters. A semi-micro method has been used for comparison. The application range extends from 40 to 12 000 mg O 2 l −1, whereas the lowest limits of detection and quantification are 13.5 and 45 mg O 2 l −1, respectively. Following this method, the interference of Cl − can be compensated for at least up to 10 000 mg l −1 Cl −. Up to nine samples per hour can be analyzed.

Flow injection method for the rapid determination of chemical oxygen demand based on microwave digestion and chromium speciation in flame atomic absorption spectrometry

The present paper describes a new flow injection method for the determination of Chemical Oxygen Demand (COD). This method consists of a first digestion step, where the sample is heated by microwave radiation, a second one where an anionic exchange resin retains the Cr(VI) that has not been reduced by the organic matter of the sample and a third one where Cr(VI), after being eluted, is determined by flame atomic absorption spectrometry. The microwave power applied, the sulphuric acid concentration, the liquid flow in the digestion step and the sample volume were the variables studied. The recovery and precision obtained with this method are similar to those obtained using a standard semi-micro method, whereas the throughput is much higher (up to 50 determinations per hour). As regards sensitivity, by changing the sample loop volume and the concentration of dichromate, one can analyze samples with Chemical Oxygen Demand values between 25 and 5000 mg/l. The limit of detection is about 7 mg/l COD. An interesting feature of the new method, which is not shared by most other flow injection methods of Chemical Oxygen Demand determination, is that there is no matrix effect in the determination step.

Rapid semi-micro method for separating non-ortho chlorinated chlorobiphenyls from other chlorobiphenyls

A method for separating common non-ortho chlorinated chlorobiphenyls, namely 3,4,4′-tri-, 3,4,4′,5-, 3,3′,4,4′-tetra, 3,3′,4,4′,5-penta-, and 3,3′4,4′,5,5′-hexachlorobiphenyl (IUPAC Nos. 37, 81, 77, 126, and 169) from other chlorobiphenyls in shellfish tissue at pg g–1 wet mass concentrations is described. The method is based on saponification followed by extraction into 2,2,4-trimethylpentane, clean-up by gel-permeation chromatography and sulfuric acid treatment, separation of non-ortho chlorinated chlorobiphenyls from other chlorobiphenyls using a Florisil–carbon column and measurement using capillary GC–low resolution MS with selected ion monitoring to eliminate many interfering materials. Recoveries of chlorobiphenyls (20–5000 pg g–1 wet mass) averaged 84.5 ± 6.5%. The detection limits (3 times the noise level) are 20 pg g–1 wet mass for IUPAC Nos. 37, 77, 81, and 126 and 50 pg g–1 wet mass IUPAC No. 169. The method gave results for non-ortho chlorinated chlorobiphenyl concentrations in lobster digestive gland tissues and Aroclors equivalent to those obtained by a conventional procedure.

Potentiometric determination of urea with perchloric acid in acetic anhydride

A potentiometric method for the quantitative determination of urea is proposed. Urea is titrated with perchloric acid in acetic anhydride solvent. This method is rapid and less costly than the semi-micro Kjeldahl method. In addition, its accuracy is nearly identical with that of Kjeldahl's method. An analysis of a given sample is completed in about 30 min.

A rapid semi-micro method for the separation of lipoprotein fractions that uses a benchtop ultracentrifuge

A rapid semi-micro method for the separation of lipoprotein fractions that uses a benchtop ultracentrifuge