Fluorometric and spectrophotometric determination of pirbuterol hydrochloride in authentic and dosage forms

Pirbuterol hydrochloride has been assayed in alkaline medium by using a fluorometric method to measure fluorescence intensity at 372 nm with excitation at 310 nm and by the delta A method at 242 nm. The linearity ranges are 0.5-4 micrograms/mL and 10-50 micrograms/mL, respectively. An authentic pirbuterol HCl sample was analyzed by nonaqueous potentiometric titration using 0.1N perchloric acid, and the results were compared with those for fluorometric and delta A methods. The mean percent recoveries for the authentic sample were 98.72 +/- 1.13 and 99.24 +/- 0.85, respectively. When applied to commercial capsules containing 10 mg and 15 mg each, the fluorometric method gave mean percent recoveries of 101.11 +/- 1.05 and 98.12 +/- 0.93; the delta A method gave mean percent recoveries of 100.57 +/- 0.83 and 97.80 +/- 0.75, respectively.     

A simple procedure for colorimetric determination of organic carbon in soil

Abstract

A simple procedure is described for the rapid determination of organic carbon content in a large number of soil samples using an automated segmented flow analyser. The method is a modification of the wet oxidation/ digestion methods based on potassium dichromate combined with a colorimetric method for determination of chromic oxide (Stevenson and Clare, 1962). Using a segmented flow analyser for the colorimetry, the procedure is capable of automated routine analyses of large numbers of samples and was shown to give high and repeatable recoveries of organic carbon from a range of compounds. Organic carbon values for a range of soils analysed by the reported method and by the dry combustion technique showed a high correlation.     

Determination of organic matter in sewage sludges

Abstract

Procedures for determining organic matter indirectly and directly in sludges are described. A good agreement between chromic acid oxidation and dry—combustion elemental analysis methods of determining organic‐C was observed. Sludge organic matter content was determined directly by loss‐on‐ignition by thermal analysis. An average C factor of 1.68 to estimate the organic matter from organic‐C, obtained by chromic acid oxidation method, was calculated for aerobically digested sludges.     

Hypochlorous and peracetic acid induced oxidation of dairy proteins

Hypochlorous and peracetic acids, both known disinfectants in the food industry, were compared for their oxidative capacity toward dairy proteins. Whey proteins and caseins were oxidized under well controlled conditions at pH 8 as a function of the sanitizing concentration. Different markers for protein oxidation were monitored. The results established that the protein carbonyl content was a rather unspecific marker for protein oxidation, which did not allow one to differentiate the oxidant used especially at the lower concentrations. Cysteine, tryptophan, and methionine were proven to be the most vulnerable amino acids for degradation upon hypochlorous and peracetic acid treatment, while tyrosine was only prone to degradation in the presence of hypochlorous acid. Hypochlorous acid induced oxidation gave rise to protein aggregation, while during peracetic acid induced oxidation, no high molecular weight aggregates were observed. Protein aggregation upon hypochlorous acid oxidation could primarily be linked to tryptophan and tyrosine degradation.     

Evaluation of a rapid chromic acid method for determination of total nitrogen in soils

Abstract

A chromic acid method proposed for rapid determination of total nitrogen (N) in soils was evaluated by comparing its results with those obtained by a Kjeldahl method commonly used for total N analysis of soils. Analyses of 12 surface soils selected so that they differed markedly in texture and organic carbon content showed that the chromic acid method recovered only 87.5% to 94.1% (average, 90.5%) of the soil N recovered by the Kjeldahl method. The recovery of N from ammonium sulfate and soils by the chromic acid method decreased with increase in time of digestion with chromic acid from 1 minute to 15 minutes (the recommended digestion time). This indicates that the low recovery of soil N by the chromic acid method was at least partly due to oxidation of ammonium to nitrate and/or nitrite by chromic acid and subsequent gaseous loss of these forms of N. Support for this conclusion was provided by analyses showing that about half of the N that could not be recovered as ammonium after digestion of ammonium sulfate with chromic acid for 15 minutes was in the form of nitrate.     

Oxidation of quercetin by salivary components. Quercetin-dependent reduction of salivary nitrite under acidic conditions producing nitric oxide

Under acidic conditions, nitrite is protonated to nitrous acid (pK(a) = 3.2-3.4) that can be transformed into nitric oxide by self-decomposition and reduction. When sodium nitrite was mixed with quercetin at pH 1-2, quercetin was oxidized producing nitric oxide. In addition to quercetin, kaempferol and quercetin 4'-glucoside were also oxidized by nitrous acid, but oxidation of apigenin, luteolin, and rutin was slow compared to oxidation of the above flavonols. These results suggested that flavonols, which have a free hydroxyl group at carbon position 3, can readily reduce nitrous acid to nitric oxide. When the pH of saliva was decreased to 1-2, formation of nitric oxide was observed. The nitric oxide formation was enhanced by quercetin, and during this process quercetin was oxidized. These results indicate that there is a possibility of reactions between phenolics and nitrous acid derived from salivary nitrite in the stomach.     

Evaluation of lipid ultraviolet absorption as a parameter to measure lipid oxidation in dark chicken meat

The application of lipid UV absorption (235, 269, and 280 nm) to follow up lipid oxidation in dark chicken meat has been evaluated using raw and cooked samples with different alpha-tocopherol contents (modulated by dietary supplementation). To this purpose, when absorption was measured at 235 nm, second-derivative spectrophotometry did not show any significant advantage over nonderivative spectrophotometry. For absorption at 269 and 280 nm, nonderivative spectrophotometry more sensitively monitored lipid oxidation than second- and third-derivative spectrophotometry. In addition, only direct measurements at 235 and 269 nm and second-derivative measurements at 235 nm showed a limited usefulness to follow up lipid oxidation in our samples. However, these UV absorption parameters were much less effective than lipid hydroperoxide values measured through a ferrous oxidation-xylenol orange method and 2-thiobarbituric acid values determined by a third-derivative spectrophotometric method with acid aqueous extraction.     

测定土壤硝态氮的紫外分光光度法与其他方法的比较

使用酚二磺酸法、还原蒸馏法、镀铜镉还原．重氮化偶合比色法和改进紫外分光光度法（校正因数法）测定了中国9种不同类型土壤的硝态氮含量，分析了改进紫外分光光度法与其余三种测定方法的差异及其适用性。统计分析表明对于有机质含量低于50g kg^-1的矿质土壤，可以使用2．2作为校正因数，四种分析方法的测定值具有极显著的相关性，尤其是紫外分光光度法与酚二磺酸法的测定结果最为接近，没有极显著差异；对于有机质含量接近和高于50g kg^-1的土壤，校正因数还需要修改。紫外分光光度法具有操作简单、测定速度快等优点，适用于批量快速测定。     

Sample oxidation procedures for the determination of chromium and nickel in biological material

Abstract

Sample preparation methods for atomic absorption spectrophotometric analysis of chromium and nickel in biological materials were examined. Radiotracer recovery, precision of analysis and analysis of NBS reference samples were the criteria used. Chromium and nickel in biological materials can be successfully prepared for atomic absorption spectrophotometry by dry ashing with nitric acid treatment of the partially oxidized sample. It was necessary to use at least 5% nitric acid to extract the chromium and nickel from the ash. Vet digestion with nitric acid alone was satisfactory for nickel but not for chromium. Wet digestion gave greater variance and required considerably more time. We found no evidence of loss of chromium by either volatilization or insolubility. Since this method is satisfactory for nickel determination it may be implied that it is also satisfactory for other nonvolatile first transition series elements.     

Free-radical scavenging capacity using the fenton reaction with rhodamine B as the spectrophotometric indicator

A spectrophotometric method was developed to measure antioxidant free-radical scavenging capacity. Rhodamine B (RhB) was oxidized by hydroxyl radical generated via the Fenton reaction to yield a photoinactive RhB product. RhB absorption at 550 nm was restored when antioxidant agents scavenged hydroxyl radical to protect RhB from oxidation. On the basis of the dose response of antioxidant recovery capacity, a model was developed to calculate the free-radical scavenging ability. This method was sensitive to a wide range of antioxidant activity with ascorbic acid reference set as one; the antioxidant recovery capacity of quercetin was 635 compared to 2 for benzoic acid.     

Effect of Sample Preparation Methods on Analytical Values of Some Micro‐ and Secondary Nutrients in Plant Tissues

Abstract: Plant tissues of rice and wheat crops (n = 5) collected at harvest time were wet‐ashed in di‐acid mixture [analytical‐grade nitric acid (HNO₃)–perchloric acid (HClO₄), 3:1, v/v] on a sand bath at 200 °C or dry‐ashed in a muffle furnace at 550 °C for 3 h in triplicate. The samples were analyzed for calcium (Ca), iron (Fe), and molybdenum (Mo) using double‐beam atomic absorption spectrophotometry (GBC‐Avanta ∑ model) and for boron (B) by colorimetry (UV‐VIS spectrophotometer, ECIL‐GS 5705 model) using Azomethine‐H procedure. As per the paired t‐test, both wet‐ashing and dry‐ashing procedures resulted in statistically similar analytical values for B, Ca, Fe, and Mo. However, the mean coefficients of variation were higher with the wet‐ashing procedure (6.19 to 9.64%) as compared to the dry‐ashing procedure (2.14 to 3.45%). The dry‐ashing procedure was found to be the best for routine chemical analysis of B and Mo in plant samples.     

Interaction between ascorbic acid and chlorogenic acid during the formation of nitric oxide in acidified saliva

When saliva and gastric juice are mixed, salivary nitrite is transformed to nitrous acid to produce nitric oxide (NO). The NO formation in acidified saliva was enhanced by ascorbic acid and chlorogenic acid. Thiocyanate ion (SCN(-)) also enhanced the transformation of nitrous acid to NO. During the NO formation in the presence of both ascorbic acid and chlorogenic acid, ascorbic acid was preferentially oxidized. Chlorogenic acid was oxidized after ascorbic acid had been oxidized. Ascorbyl radical was detected during the oxidation of ascorbic acid, and the radical intensity was decreased by chlorogenic acid. The decrease is discussed to be due to the reduction of the oxidation intermediate or product of chlorogenic acid by ascorbyl radical. The result obtained in this study suggests that ascorbic acid was preferentially oxidized and that not only ascorbic acid but also ascorbyl radical could interact with the oxidation intermediate or product of chlorogenic acid when chlorogenic acid was added to the mixture of saliva and gastric juice that contained ascorbic acid.     

LC-MS investigation of oxidation products of phenolic antioxidants

Two oxidation systems were examined for the oxidation of three groups of phenolic antioxidants; five cinnamic acids, two benzoic acids, and two phenols characteristic of olive fruits. Periodate oxidation, which is reported to produce products similar to polyphenol oxidase, was contrasted with the reactivity of the Fenton system, an inorganic source of hydroxyl radicals. Reaction products were identified as various quinones, dimers, and aldehydes, but the nature of the products differed between the two oxidation systems. Structure-activity effects were also observed for the different phenols. All cinnamic acids in this study reacted with the Fenton reagent to produce benzaldehydes as the main products, with the exception of 5-caffeoylquinic acid. In contrast, periodate oxidation gave no reaction with some of the cinnamic acids. Quinone formation was observed for the two compounds, caffeic acid and 5-caffeoylquinic acid, possessing o-hydroxy groups. Caffeic acid was unusual in that dimer formation was the main initial product of reaction. Benzoic acids were readily oxidized by both systems, but no identifiable products were isolated. Oleuropein was oxidized by both oxidants used in this study, resulting in quinones in each system, whereas little or no oxidation of tyrosol was observed. This highlights the importance of conjugation between the alkene double bond and the hydroxy group. The results question the validity of many existing methods of testing antioxidant activity.     

Effects of Selected Barley Cultivars and Their Pearling Fractions on Inhibition of Human LDL Oxidation In Vitro Using a Modified Conjugated Dienes Method

Oxidation of LDL cholesterol is an important factor in the development of atherosclerosis and heart disease. In this study, selected Canadian and Egyptian barley cultivars and their pearling fractions were evaluated for antioxidant capacity to inhibit human LDL oxidation in vitro. Measurement of conjugated dienes (CD) at 234 nm was optimized to determine the degree of LDL oxidation. Dilution of oxidized LDL with iso‐propanol gave a distinct diene conjugation peak. Significant differences in total phenols content (TPC) were found between the cultivars tested, with the hulless barley having greater TPC and inhibition capacity compared with hulled barleys. The outer layers fraction contained the highest TPC, lowest CD formation, and longest lag time, whereas the inner, or endosperm fraction, had the lowest inhibition effects. The middle pearling and hull fractions possessed intermediate inhibition effects. The inhibitory effect of barley extracts was dependent on phenols concentration following a linear or quadratic pattern. The results suggest that barley whole meals, outer layers, middle pearling, or hull fraction would be a potential LDL antioxidant.     

Determination op fluoride in plant samples by a potentiometric method and near‐infrared reflectance spectroscopy

Abstract

The determination of fluoride in plant materials was studied using a specific ion electrode following extraction using either deionized water or 0.1 M perchloric acid.

When the extracting agent was water, the amount of fluoride determined was generally 37% less than that obtained using perchloric acid. However, a close relationship was observed between the amounts extracted by either procedure. When perchloric acid is used, the method was found to be precise (variation coefficient 0.74%), accurate (average recovery 98.67%) and sensitive enough to be used in the routine analysis of plant materials.

The determination of fluoride by near‐infrared reflectance analysis (NIRA) was also used which gave generally acceptable results.     

Evaluation of alternative substrates for determining methane-oxidizing activities and methanotrophic populations in soils

The magnitude of methane emission is a net result of methane production and the oxidation rate. The possibility of measuring oxidized products of alternative substrates of methane monooxygenase was examined to determine methane-oxidizing ability of soils, and to count methanotrophic populations in soils. Wetland rice soils were incubated under methane containing air to enirch the methanotrophs. Methane loss and oxygen uptake were inhibited by acetylene, dimethylether, and nitrapyrin (N-Serve). Acetylene was used routinely, because it inhibited methane oxidation even at a low concentration of 0.03 to 0.06 l ml^-1 in the incubation headspace. Propylene at 10 kPa was used as an alternative substrate of methane monooxygenase, and the formation of propylene oxide was measured. When soils were incubated under methane, their methane-oxidizing activity increased. Propylene oxide formation increased simultaneously. Acetylene also blocked propylene oxidation. The results of several experiments and propylene oxide formation (r=0.87 after long-transformation). These results indicate that propylene oxide formation can be used as a semiquantitative measure of the methane-oxidizing activity of soils. The colonies of soluble methane monooxygenase-forming methanotrophs were counted on Cu-deficient methanotroph agar medium by the formation of naphthol from haphthalene. The counts increased from 10⁴ (0 days) to 10⁷ (21 days) g^-1 soil during oxic incubation under methane.     

Determination of low concentrations of organic phosphorus in soil solution

Abstract

Phosphorus (P) export from agricultural land is an important source of water‐quality deterioration in many areas of the world. Part of the total phosphorus in the soil solution is represented by dissolved organic P at concentrations that can be as low as 1x10^‐6 M of P. The suitability of four digestion methods for the destruction of organic P and determination of orthophosphate at low concentrations and small volumes using the malachite green method has been evaluated. The acid digestion procedures evaluated were 1) sulfuric and perchloric acid, 2) sulfuric acid and potassium persulphate, 3) nitric acid, and 4) nitric and perchloric acid. As inositol hexaphosphate (IHP) represents one of the more resistant molecules to acid hydrolysis in soils, this compound has been chosen to assess the recovery assay of the recommended procedure. The digestion procedures were adapted for the malachite green spectrophotometric method, in order to obtain lower analytical limits for P determination. The sulfuric‐perchloric acid digestion gave excellent recovery and reproducibility, and can therefore be used for determining organic P in solution at concentrations as low as 6.45x10^‐7 M.     

An Improved Turbidimetric Estimation of Total Sulfur in Plant Samples

The estimation of total sulfur content in plant samples by the nitric acid-perchloric acid wet oxidation, when used with the Tabatabai and Bremner's adaptation of the Barium chloride-gelatin method of Dodgson, gives lower results as compared to the magnesium nitrate oxidation, particularly for samples low in sulfur content. For samples containing relatively high sulfur content, both methods of oxidation give comparable results.     

Nitric Acid Oxidation for Improvement of a Chinese Lignite as Soil Conditioner

Oxidation is known commonly to enhance humic acid (HAs) contents of coal, but in China, most humic substances are used directly as soil conditioners or applied in combination with fertilizers without oxidation. Therefore, we investigated the impact of nitric acid (HNO₃) oxidation on the characteristics of HAs derived from a Chinese lignite. The results showed that total HA content was increased by HNO₃ oxidation, thus consequently increasing its cation exchange capacity and moderate humification. Besides, HAs extracted from oxidized lignite were richer in oxygen-containing functional groups with smaller molecular size than natural lignite. Compared with natural lignite, retention capacities of nitrogen and potassium by oxidized lignite were significantly greater. However, phosphorus-retention capacity was decreased to near zero, which might enhance the availability of phosphorus in soil. In general, optimum HNO₃ oxidation had favorable effects on lignite and improved its characteristics for use as a soil conditioner.     

Protein and lipid oxidation during frozen storage of rainbow trout (Oncorhynchus mykiss)

This study aimed at investigating protein and lipid oxidation during frozen storage of rainbow trout. Rainbow trout fillets were stored for 13 months at -20, -30, or -80 degrees C, and samples were analyzed at regular intervals for lipid and protein oxidation markers. Lipid oxidation was followed by measuring lipid hydroperoxides (PV), as well as secondary oxidation products (volatiles) using dynamic headspace GC-MS. Free fatty acids (FFA) were measured as an estimation of lipolysis. Protein oxidation was followed using the spectrophotometric determination of protein carbonyls and immunoblotting. Significant oxidation was observed in samples stored at -20 degrees C, and at this temperature lipid and protein oxidation seemed to develop simultaneously. FFA, PV, and carbonyls increased significantly for the fish stored at -20 degrees C, whereas the fish stored at -30 and -80 degrees C did not show any increase in oxidation during the entire storage period when these methods were used. In contrast, the more sensitive GC-MS method used for measurement of the volatiles showed that the fish stored at -30 degrees C oxidized more quickly than those stored at -80 degrees C. Detection of protein oxidation using immunoblotting revealed that high molecular weight proteins were oxidized already at t = 0 and that no new protein oxidized during storage irrespective of the storage time and temperature. The results emphasize the need for the development of more sensitive and reliable methods to study protein oxidation in order to gain more explicit knowledge about the significance of protein oxidation for food quality and, especially, to correlate protein oxidation with physical and functional properties of foods.