Determination of fructose and glucose in cucurbitaceae by h.p.l.c.

High performance liquid chromatography (h.p.l.c.) was used to characterise and quantify fructose and glucose in seven members of the Cucurbitaceae family. The h.p.l.c. system consisted of a μ-Bondapak/Carbohydrate packed column, a solvent system of acetonitrile-water (800 ml l^?-1) with a flow rate of 2.5 ml min^?-1, and a refractive index detector. The analysis, including sample preparation, was completed in less than 45 min. The quantities of fructose and glucose obtained were, except for one sample, <1% on a fresh weight basis, and the glucose: fructose ratios ranged from 0.41:1 to 0.93:1.     

Tryptophan determination of food proteins by h.p.l.c. after alkaline hydrolysis

The alkaline hydrolysis of proteins prior to tryptophan analysis has been evaluated, and a method for the measurement of tryptophan by reverse phase h.p.l.c. after alkaline hydrolysis has been proposed and compared with published methods. Hydrolysis with either LiOH or NaOH gave similar results. Tryptophan values and the recovery of added 5-methyltryptophan were similar when hydrolysis was made under tap-water vacuum (1500 Pa) or at high vacuum (2 Pa). Partially-hydrolysed starch reduced the losses of tryptophan during hydrolysis better than thiodiglycol. High levels of indolyl-3-propionic acid or 5-methyltryptophan did not further improve tryptophan recovery. 5-Methyltryptophan is the preferred internal standard; its recovery after hydrolysis more closely resembled that of protein-bound tritiated tryptophan from goat casein than did the recoveries of α-methyltryptophan or free ¹⁴C-tryptophan. Under some conditions, the recovery of protein bound tryptophan was lower than the recovery of free tryptophan. The stability of tryptophan in hydrolysates was improved by using a phosphate buffer pH 7.0 containing 0.02% sodium azide.     

An h.p.l.c. method for the quantitative determination of asulam, acetylasulam and sulphanilamide in peaches

An analytical method has been developed for the determination of the herbicide, asulam [methyl(4-aminobenzenesulphonyl)carbamate] and two metabolites, sulphanilamide and acetylasulam individually, in peaches. Asulam and acetylasulam were partitioned from an aqueous phase with ethyl ether, leaving behind more polar components which interfered with the analysis of these compounds. The sulphanilamide was next partitioned from the aqueous phase into ethyl acetate. Each fraction was then chromatographed on its own neutral alumina column, activity grade 1, and analysed by high performance liquid chromatography (h.p.l.c.) using a C-18 reverse phase column. From peach samples fortified at the 0.10 p.p.m. level, recoveries averaged 72% (asulam), 100% (acetylasulam) and 90% (sulphanilamide). No residues of these compounds were found in two studies of peaches harvested 0, 5, 10, 15 and 20 days following asulam treatment at 0-7.50 kg/ha.     

A rapid h.p.l.c. method for the determination of methionine hydroxy analogue free acid in supplemented feeds

Two methods are described for determining methionine hydroxy analogue free acid (HMB) in supplemented poultry feeds. The procedure is based on extraction of analogue from the feed, followed by high-pressure liquid chromatographic measurement of the HMB directly after extraction or, more rigorously, after extraction and hydrolysis of oligomers to monomer. Recoveries of HMB over the supplementation range 0.08–0.25% (by wt) are 98% with coefficients of variation of 5.4% in commercial poultry feeds. A 98% correlation coefficient is obtained when the analyses are compared with the gas chromatographic method.     

A simplified procedure for quantification of potato glycoalkaloids in tuber extracts by H.p.l.c.; comparison with ELISA and a colorimetric method

An improved high-performance liquid chromatography (h.p.l.c.) procedure for determination of glycoalkaloid levels in potato tubers has been developed in which Sep-Pak cartridges replace the commonly used alkaline precipitation for clean-up of tuber extracts. Glycoalkaloids are extracted from fresh tuber tissue into an aqueous medium, the extract is submitted to clean-up and α-solanine and α-chaconine are quantitatively separated on a reversed phase column with ethanolamine modifier added to the mobile phase. Potato tubers were comparatively analysed for their glycoalkaloid content by this and two other methods: a recently developed immunoassay (ELISA) and a colorimetric procedure representing the traditional chemical approach. Agreement between the h.p.l.c. and the other methods was good.     

Determination of sugars in tropical root crops using 13C N.m.r. spectroscopy: Comparison with the h.p.l.c. method

The ¹³C nuclear magnetic resonance (n.m.r.) spectrum of sugars normally present in foods, viz. glucose, fructose, sucrose, maltose and raffinose contains resonances that are diagnostic of each sugar. The quantity of each sugar is determined by measurement of the ratios of the peak heights of the sugar resonances compared with peak height of an internal standard, present at constant concentration in all solutions. A linear calibration relationship between the peak height ratio and concentration is established for single resonances of glucose and fructose and for two resonances of each of sucrose, maltose and raffinose. Samples of sweet potato and taro flour dried at 40°C, were blended with 80% ethanol, the sugars were extracted and analysed by ¹³C n.m.r. and h.p.l.c. Both methods gave similar results and have similar degrees of reproducibility. The n.m.r. method is useful for quantitation of sugars and identification of other molecules extracted from the food, but requires more material than does h.p.l.c. Drying at 40°C causes a decrease in sucrose content and increases in glucose, fructose and maltose which partly compensate for the loss in sucrose. There is considerable variability of the sugar content between different sweet potato tubers and between different taro corms of the same cultivar as well as across different cultivars. For sweet potato the total sugar content is 0.6-3.6% fresh weight, with considerably more sucrose present than glucose, fructose and maltose. With taro total sugar content is 0.2-0.8% fresh weight. Raffinose is present in one sample only.     

A silica gel chromatographic procedure adapted to liquid-scintillation counting of 14c labelled organic acids from plant material and silage

A method is described for the separation of a wide range of organic acids present in plant material and in silage. The method consists of cold extraction with dilute sulphuric acid, followed by purification of the extract on a silica gel column. The organic acids in the purified extract were separated quantitatively using a continuous gradient-elution system of eluents through a small silica gel column. The extraction method was found to be more efficient for extracting citric, oxalic and fumaric acids from red clover, than a standard method with ethanol, water and ion-exchange resins. Most of the acids of the tricarboxylic acid cycle were detected in red clover. An unidentified acid accounted for more than 37% of the organic acidity. The activity of ¹⁴C-labelled acids could be measured directly on the eluate from the column in combination with a liquid scintillation system.     

H.p.l.c. Determination of trace levels of succinic acid in orange juice from Freeze-damaged and undamaged fruit

Succinic acid was determined by high-performance liquid chromatography (h.p.l.c.) in juice from oranges subjected to freeze damage on the tree and by storage at below freezing temperatures. Succinic acid levels did not change in fruit subjected to freezing temperatures while on the tree or in storage. In order to measure succinic acid at these low levels (5–180 mg litre^?1 juice) an earlier h.p.l.c. procedure was modified.     

Comparison of centrifugation and filtration techniques for the size fractionation of colloidal material in soil suspensions using sedimentation field-flow fractionation

Sedimentation field-flow fractionation (SdFFF) with UV detection is used to systematically investigate the effect of traditional membrane filtration and centrifugation procedures on the isolation of specific size fractions from soil suspensions. Both procedures were used to isolate the nominal <0.45 and <0.2 microm fractions from a clay soil suspension. Results showed that the membrane filtration approach seriously underestimated the total mass of particulate matter present as compared to the centrifugation approach. This has serious implications forthe interpretation of results for "colloidal" and "soluble" fractions from soil suspensions and other environmental matrices obtained using the standard membrane approach. The results also show that sedimentation FFF has great potential as a robust and relatively mild technology for studying size distributions in the "colloidal" range for soil suspensions and other aquatic matrices.     

Identification and characterization of sorption domains in soil organic matter using strucuturally modified humic acids

The sorption of phenanthrene was examined in humic acids (HAs) from different sources: a compost, a peat soil, and a mineral soil. Sub-samples of each HA were subjected to bleaching or hydrolysis to remove predetermined chemical groups from their structures. Bleaching successfully removed a large percentage of rigid, aromatic moieties, whereas hydrolysis removed the mobile, carbohydrate components. Phenanthrene sorption by all HAs was nonlinear (N < 1). However, the phenanthrene isotherms of the bleached HAs were more linear than those of the untreated HAs, whereas the removal of the carbohydrate components by hydrolysis produced more nonlinear isotherms. The introduction of pyrene to the phenanthrene sorption system yielded more linear isotherms for all the HAs, indicative of competitive sorption. Proton spin-spin (1H T2) relaxation determined by nuclear magnetic resonance (NMR) was used to identify separate rigid (condensed) and flexible (expanded) 1H populations and to determine their distribution. These 1H domains were highly sensitive to temperature and correlated well with reported glass transition temperatures for HAs. In combination with the chemical treatments, sorption, and spectroscopic data, we were able to observe some significant relationships among chemical groups, sorption behavior, and structural characteristics.     

Assessment of a sequential extraction procedure for perturbed lead-contaminated samples with and without phosphorus amendments

Sequential extraction procedures are used to determine the solid-phase association in which elements of interest exist in soil and sediment matrixes. Foundational work by Tessier et al. (Tessier, A.; Campbell, P. G. C.; Bisson, M. Anal. Chem. 1979, 51, 844-851) has found widespread acceptance and has been employed as an operational definition for metal speciation in solid matrixes. However, a major obstacle confronting sequential extraction procedures is species alteration of extracted metals before, during, and after separation of solids from solution. If this occurs, the results obtained from sequential extraction do not provide an accurate account of metal speciation within the matrix because the metal forms are altered from their field state. Many researchers dismiss this drawback since several sorption and precipitation processes are believed to occur at time scales much longer than any particular extraction step. This assumption may not be valid. The objectives of this study were to investigate the potential formation of pyromorphite (Pb5(PO4)3Cl) during the sequential extraction steps of Pb-spiked samples with and without calcium phosphate amendments and to examine the differences in the operationally defined distribution of Pb in samples with and without the presence of P. The systems that were examined in the absence of phosphate behaved, for the most part, adequately according to the operational definitions of the extraction procedure. However, when the samples were amended with phosphate, results were drastically changed with a significant shift of extractable Pb to the residual phase. This redistribution was due to pyromorphite formation during the extraction procedure as confirmed by X-ray diffraction and X-ray absorption (XAS) spectroscopies. These results indicate that sequential extraction methods may not be suitable for Pb speciation in perturbed environmental systems (i.e., fertilized agricultural soils or amended contaminated soils) and that rigorous interpretation should be avoided, if not supported by methods to definitively prove metal speciation (e.g., XAS).     

Effect of moisture content during incubation of soil treated with organic materials on changes in sulphate and sulphide levels

Water-soluble sulphate and total sulphide levels were determined during 0, 3, 6 and 12 weeks' incubation (30°) of soil at varying moisture contents (0–133% mwhc) with and without addition of 1 % organic materials (cellulose, compost and dwarf peas, all in a finely ground state). With added peas, conditions were apparently anaerobic at all moisture contents, since immobilisation of sulphate and accumulation of sulphide occurred. Where cellulose or compost were added, sulphide accumulated only at 80% mwhc and higher moisture contents, and increased with moisture content. In unamended soil and soil + compost only sulphate accumulated at 20–60 % mwhc and accumulation increased with moisture content in this range. Where cellulose was added sulphate immobilisation occurred and was less at 20–60% mwhc than at higher moisture levels. At 80% mwhc or more anaerobic effects were predominent. The optimum moisture contents for the accumulation of sulphate and sulphide were 60% and 133% mwhc respectively.     

An automated procedure for the determination of aluminium in soil and plant digests

An automated procedure for the determination of aluminium in soil and plant digests using the Technicon Autoanalyzer is described. Aluminium is determined with the complexing dye sodium alizarin-3-sulphonate (Alizarin Red S). The interfering effect of iron is removed with thioglycollic acid. The reagent gives a very reproducible and linear response up to 15 parts/million of aluminium. Leaf tissue samples tested included those from rubber, tea, maize, coconut, oil palm, sorghum and rice. Soil types tested were Serdang, Rengam, Munchong and peat.     

Interactive priming of biochar and labile organic matter mineralization in a smectite-rich soil

Biochar is considered as an attractive tool for long-term carbon (C) storage in soil. However, there is limited knowledge about the effect of labile organic matter (LOM) on biochar-C mineralization in soil or the vice versa. An incubation experiment (20 °C) was conducted for 120 days to quantify the interactive priming effects of biochar-C and LOM-C mineralization in a smectitic clayey soil. Sugar cane residue (source of LOM) at a rate of 0, 1, 2, and 4% (w/w) in combination with two wood biochars (450 and 550 °C) at a rate of 2% (w/w) were applied to the soil. The use of biochars (~ -36‰) and LOM (-12.7‰) or soil (-14.3‰) with isotopically distinct δ(13)C values allowed the quantification of C mineralized from biochar and LOM/soil. A small fraction (0.4-1.1%) of the applied biochar-C was mineralized, and the mineralization of biochar-C increased significantly with increasing application rates of LOM, especially during the early stages of incubation. Concurrently, biochar application reduced the mineralization of LOM-C, and the magnitude of this effect increased with increasing rate of LOM addition. Over time, the interactive priming of biochar-C and LOM-C mineralization was stabilized. Biochar application possesses a considerable merit for long-term soil C-sequestration, and it has a stabilizing effect on LOM in soil.     

Spectrophotometric determination of boron in plant and soil samples by a new solvent extraction procedure

A routine method has been developed for the determination of boron in plant and soil samples. The boron in the prepared samples is converted into BF₄- in a H₂SO₄-HF system, then extracted as a coloured complex with Azure-C (or mthylne blue) into dichloroethane and finally determined spectrophotometrically. Satisfactory recoveries (±7%) were obtained for plant tissue analyses.     

Recent advances in methodology for analysis of phytate and inositol phosphates in foods.

This review summarises the methods available for the analysis of phytate and structurally related molecules, i.e., inositol polyphosphates. Phytate has been determined by colorimetry, low pressure ion exchange column chromatography, phosphorus-31 fourier transform nuclear magnetic resonance spectroscopy (31P FT NMR), near-infrared reflectance spectroscopy and high performance liquid chromatography (HPLC). Among these techniques anion exchange column chromatography and HPLC were shown to be best suited for separation of inositol phosphates. Since inositol phosphates do not have a characteristic absorption spectrum, their detection in HPLC analysis is limited to methods employing monitoring of refractive index, post column reaction products, conductivity or indirect detection although other detection methods may be feasible. As refractive index detection under isocratic eluent conditions is relatively easy to manipulate, anion-exchange HPLC methods using a low capacity column or ion-pair HPLC methods are recommended for the analysis of inositol phosphates in nutritional studies.     

中国过滤材料性能测试方法标准的现状及建标工作

阐述了国内外通油过滤材料和空气过滤材料的主要性能及其测试方法。指出我国尚未建立“过滤材料性能测试方法标准”,不利于过滤材料行业的发展,建议正视现实,推动该标准的建立,并提出了建标原则和具体项目的建议。     

烟田施用有机肥对土壤理化性状和烟叶香气成分含量的影响

本试验研究了烟田施用不同数量草炭对土壤的有机质含量、理化性状、土壤微生物数量及烟叶中香气成分含量的影响。结果表明,烟田施用有机肥草炭8250~16500 kg/hm2,随着施肥量的增加,土壤有机质、腐殖质含量,土壤真菌、细菌和放线菌数量均增加;烟叶香气成分中总醇量增加,总醛量减少,总酮量稍有增加。