Quantitative Determination of Gluten Protein Types in Wheat Flour by Reversed-Phase High-Performance Liquid Chromatography

A combined extraction-HPLC procedure was developed on a microscale to determine the amounts of the different gluten protein types (ω5-, ω1,2-, α- and γ-gliadins; high molecular weight [HMW] and low molecular weight [LMW] glutenin subunits) in wheat flour. After preextraction of albumins and globulins from flour (100 mg) with a salt solution (2 × 1.0 mL), extraction of gliadins was achieved with 60% aqueous ethanol (3 × 0.5 mL). Subsequently, the glutenin subunits were extracted under nitrogen and at 60°C with 50% aqueous 1-propanol containing Tris-HCl (0.05 mol/L, pH 7.5), urea (2 mol/L) and dithioerythritol (1%). The separation and quantitative determination of gliadins and glutenin subunits was then performed by reversed-phase HPLC on C₈ silica gel at 50°C using a gradient of increasing acetonitrile concentration in the presence of 0.1% trifluoroacetic acid. The flow rate was 1.0 mL/min, and the detection wavelength was 210 nm. Temperature and flow rate were modified for the quantitation of single underivatized HMW subunits. To determine the absolute amounts of protein types, different protein standards (gliadin, LMW and HMW subunits, bovine serum albumin) with known protein contents were compared to HPLC absorbance areas. The calibration curves were almost identical and linear over a broad range (20–220 μg). This extraction-HPLC procedure allows an accurate, reproducible, sensitive, and relatively fast quantitative determination of all gluten protein types in wheat flour, and can be applied to quality evaluation of cereals as raw materials or in processed products.     

Sequential Extraction of Lead from Grain Size Fractionated River Sediments Using the Optimized BCR Procedure

Fluvial bed sediments are widely used for characterizing anthropogenic contaminant signals in urban watersheds. This study presents the first preliminary examination of sequentially extracted Pb from grain size fractionated bed sediments using the optimized (standardized) BCR procedure. Baseline sediment samples and samples from the vicinity of three storm-sewer outlets in Nuuanu Stream, Honolulu, Hawaii, were examined. The weighted average Pb liberated from four sequentially extracted phases was 144?±?26 mg/kg (±SD). These Pb concentrations are high compared to 3 mg/kg leached by a 0.5 M HCl solution, and 13 mg/kg from a 4-acid total digestion of baseline sediments. Over a 1.8 km section of stream channel, land use variations and traffic density differences had little impact on the magnitude of Pb in specific phases for each of the six grain size fractions examined. Regardless of grain size or spatial location, Pb in the reducible phase exceeded that in oxidizable, residual and acid extractable phases. Weighted reducible Pb concentrations for three sewer outlet sites ranged from 69 to 92 mg/kg, and this phase typically accounted for 70–80% of all labile Pb. The <63 μm grain size class did not exhibit the highest Pb concentration, instead this was found in either the 125–250 μm or 500–1,000 μm fractions. Examining bed sediment phase associations of Pb over a smaller length dimension (i.e., 40 m) centered around one sewer outlet, indicated higher concentrations at the outlet (180 mg/kg) compared to upstream (132 mg/kg) or downstream (150 mg/kg). The differences were primarily associated with higher Pb concentrations in the reducible and oxidizable phases of the coarse sand fractions (500–2,000 μm) at the outlet. Overall, all data point to a significant anthropogenic signal for Pb in bed sediments in the urbanized section of Nuuanu Stream.     

Determination and Speciation of Aluminum in Environmental Samples by Cation Exchange High-Performance Liquid Chromatography with High Resolution ICP-MS Detection

A cation-exchange high-performance liquid chromatography with high resolution inductively coupled plasma mass spectrometric detection (CE-HPLC/ICP-MS) was developed for the determination and the speciation of aluminum in environmental samples. Three types of aluminum species (AlL_x ^<+2, AlL_x ²⁺, Al³⁺) were separated from one another, and were determined with the present system. The comparison of the present system with an established CE-HPLC with fluorimetric detection using 5-sulfo-8-quinolinol (CE-HPLC/FL) was described. The present system showed better sensitivity for aluminum than CE-HPLC/FL. Moreover, the analytical results for soil extract and lake water samples obtained with both methods were in good agreement with each other.     

Reversed-Phase High-Performance Liquid Chromatography of naturally occurring phenolic acids in soils

A method for the analysis of phenolic acids in plant and soil materials by high-performance liquid chromatography (HPLC) is described. Separation is by reversed-phase chromatography, based on differential polarity of the investigated compounds. Optimal separation conditions are achieved by using a concave gradient elution. The HPLC technique offers excellent resolution, reproducibility and an analysis time of 30 Min.     

Rapid Trichloroacetic Acid Extraction and Liquid Chromatography Method for Determination of Nicotinamide in Commercial Cereals

Determination of niacin in fortified infant and dairy products has been accomplished using a variety of analytical liquid chromatography (LC) methods. Applications of these LC techniques to other food matrices suffer due to the presence of endogenous absorbing peaks at 260 nm that co‐chromatograph with the nicotinic acid and nicotinamide vitamers. We have successfully adapted the LC method of Woollard and Indyk for the determination of nicotinamide in reference and commercial cereal products. Unbound nicotinamide in fortified cereal was extracted with 0.6M tri‐chloroacetic acid and chromatographed on a C₁₈ reversed‐phase column using a mobile phase of 75% methanol and water (pH 2.8, with formic acid) with sodium dioctylsulphosuccinate (0.1%) as the ion‐pairing agent. Using Spectral Analysis ChromQuest software, a three‐dimensional view showed only nicotinamide under the LC peak. Similarity index spectral matches of nicotinamide standard and the LC peak were ≈100%, indicating the absence of interferences. Nicotinamide recoveries for the reference cereals of VMA195 and VMA 399 (from AACC International, St. Paul, MN) and GM 19B (from General Mills, Medallion Laboratories, Minneapolis, MN) were 90–103% of assigned value. Experimental values for oat, corn, rice, and bran cereals showed that actual niacin content in commercial cereals may be significantly above (111–170%) declared label values. Because manufacturers may fortify at a level higher than the declared label level to ensure shelf life compliance, these data do have significant implications when making precise estimates of niacin intake based on label claims.     

Separation of Wheat Proteins by Two-Dimensional Reversed-Phase High-Performance Liquid Chromatography Plus Free Zone Capillary Electrophoresis

Gliadins and glutenins from four hard red winter wheat cultivars were separated by a novel two-dimensional (2D) technique. Protein extracts were separated by reversed-phase high performance liquid chromatography as the first dimension with each 30-sec interval collected separately. Those fractions were then separated by free-zone capillary electrophoresis (FZCE) for the second dimension. Data was combined into 2D surface contour plots similar to traditional gel electrophoresis 2D maps. For HPLC, C₈ and C₁₈ columns were used in the first dimension to separate gliadins and glutenins, respectively. Uncoated fused silica capillaries (27 cm × 25 μm, i.d.) were used for the 2D FZCE separations. Differences in the 2D maps of both gliadin and glutenin fractions were found between pairs of both closely related and sister lines that varied in quality.     

通过型固相萃取-高效液相色谱-串联质谱法同时测定水产品中的5种硝基咪唑和地西泮

为建立一种同时检测水产品中5种硝基咪唑(甲硝唑、地美硝唑、洛硝哒唑、羟基甲硝唑、羟甲基甲硝咪唑)和地西泮的分析方法,本研究以通过型固相萃取柱Captiva EMR-Lipid (EMR)为净化手段,采用液相色谱-串联质谱法(HPLC-MS/MS)分析水产品中6种目标化合物的残留量.结果 表明,样品经缓冲盐调节pH值,乙...     

Elemental Speciation and Distribution in Sediments of a Eutrophied Subtropical Freshwater Reservoir Using Postextraction Normalisation

The speciation and distribution of trace and major elements (Al, As, Cd, Cr, Cu, Fe, Mn, Ni, P, Pb and Zn) in the sediments of Emigrant Creek Dam (ECD), New South Wales Australia were investigated using sequential extraction, postextraction normalisation and spatial mapping to indicate source and dispersion patterns. Subsurface coring provided an estimate of elemental enrichment and showed that As 1.9?>?P 1.7?>?N 1.5????Cd 1.5?>?Mn 1.3 were enriched. Moreover, a high proportion of the enriched elements (mean 57, 34, 47 and 87?% for As, P, Cd and Mn, respectively) were assessed as being bioavailable. Comparisons with ISQGs found that sediments from sites in proximity to Emigrant Creek inflows had the highest accumulations of metals and the greatest potential for causing biological harm. Spatially, contaminants accumulate in ECD sediments adjacent to anthropogenic sources including a cattle dip site, dredged sediment and macrophyte dump areas, and agricultural/residential runoff. Moreover, the integrated technique and postextraction normalisation allow assessment of texturally diverse and difficult sediments.     

固相萃取-高效液相色谱法测定4种蔬果中2,4-D的残留量

为建立蔬果中2,4-D残留量高效液相色谱(HPLC)检测方法,以固相萃取为净化手段,采用HPLC法检测番茄、葡萄、枇杷和黄瓜4种蔬果中2,4-二氯苯氧乙酸(2,4-D)的残留量。结果表明,样品经碱性水溶液提取、酸化,C18固相萃取小柱净化后,能够有效排除杂峰干扰,2,4-D残留量检测准确。该方法的线性相关系数为0.9980,检测限为0.0012 mg·kg~(-1),2,4-D的添加回收率为81.8%~116.0%,变异系数(CV)小于6%,表明方法准确度高,能满足番茄、葡萄、枇杷和黄瓜产品中2,4-D残留量的检测。采用此方法测定番茄等4种蔬果21份样品,样品中仅有2份番茄样品检测出2,4-D,残留量均小于0.02mg·kg~(-1)。本研究为利用HPLC检测果蔬中2,4-D残留量奠定了理论基础。     

超声提取-离子色谱法测定土壤中10种水溶性阴离子

采用超声提取–离子色谱法测定了土壤中F~–、CN~–、BrO_3~–、Cl~–、NO_2~–、Br~–、NO_3~–、PO_4~(3–)、SO_4~(2–)、C_2O_4~(2–)等10种水溶性阴离子含量。样品中阴离子用水浸提,提取条件为:固液比1:10,温度30℃,超声振荡时间30 min。提取完成后离心,取上清液通过0.22μm滤膜过滤后测定。在选定的离子色谱测定条件下,10种被测阴离子的检出限为0.009 7～0.31 mg/kg,不同阴离子的加标回收率为84.0%～112%,相对标准偏差(n=7)为0.09%～4.3%。     

Development of Analytical Procedure for the Determination of Exchangeable Cr(VI) in Soils by Anion-exchange Fast Protein Liquid Chromatography with Electrothermal Atomic Absorption Spectrometry Detection

Analytical procedure for the determination of exchangeable Cr(VI) was developed. In order to optimise the extraction procedure, the efficiency of extraction of exchangeable Cr(VI) in soil samples was investigated in KH₂PO₄–K₂HPO₄ buffer solutions (0.015 up to 0.2 mol l^?1), adjusted to the pH of the soil. Phosphate buffer was used to efficiently desorb Cr(VI) from soil particles. The extraction time (mechanical shaking) ranged from 1 up to 72 h. Cr(VI) in soil extracts was determined by anion-exchange fast protein liquid chromatography with electrothermal atomic absorption detection (FPLC-ETAAS). The study was performed on soil samples from the field treated with the tannery waste for seventeen years. Samples were analysed in the 16 year after the last waste application. It was experimentally proven that the optimal phosphate buffer concentration was 0.1 mol l^?1 and extraction time 16 h. An additional experiment was done to confirm that during the extraction, soluble Cr(III) was not oxidised to Cr(VI) by Mn(IV) oxides present in soil samples. For this purpose soil with the same characteristics, but not treated with tannery waste, was spiked with Cr(III) and the analytical procedure performed. No measurable Cr(VI) concentrations were detected. The repeatability of measurement was 2.5%, while the reproducibility of measurement was 6.9%. The accuracy of the analytical procedure was tested by spiking of soil samples with Cr(VI). The recoveries were better than 95%. The analytical procedure with limit of detection (LOD) 15 ng g^?1 of Cr(VI) was sensitive enough for the determination of exchangeable Cr(VI) in soils. In field soil samples analysed the concentrations of exchangeable Cr(VI) were found to be about 200 ng g^?1.     

超声萃取–高效液相色谱测定土壤/沉积物中1-羟基芘

本文对超声萃取土壤/沉积物中1-羟基芘(1-hydroxypyrene)的提取条件进行了优化研究,建立了一种超声萃取–高效液相色谱–荧光检测1-羟基芘的方法。结果表明:甲醇和二氯甲烷的混合溶剂为最佳萃取溶剂;甲醇与二氯甲烷的体积比是影响萃取效率的主要因素。通过正交试验进一步确定了最佳提取条件为:甲醇/二氯甲烷体积比35∶65、土液比2 g∶10 ml、提取时间20 min、提取次数3次。在最佳提取条件下,5种不同类型的土壤/沉积物中1-羟基芘的加标回收率数值变化范围很大(6.6%~83.3%),并且这种变化与样品的pH密切相关,而与样品总有机碳含量无关。     

A Rapid Acid-Oxalate Extraction Procedure for the Determination of Active Fe-oxide Forms in Calcareous Soils

Extraction with acid NH₄-oxalate is widely used to estimate the content of “active” forms of Fe oxides in soil. In calcareous soils, this extraction presents some problems (pH change, production of CO₂), which have been circumvented by decalcifying the soil before extraction. However, because of its tediousness, this procedure cannot be applied for routine purposes. In this paper, we describe a rapid procedure in which the soil is treated with oxalic acid before oxalate extraction to neutralize the active calcium carbonate equivalent. The method is simple and provides a useful estimation of the content of active Fe forms that are not occluded in the coarse particles and aggregates of carbonate.     

高效液相色谱法测定土壤中的二氯喹啉酸

用50 ml甲醇︰0.05 mol/L硼砂溶液(p H=10)(9︰1,v/v)作为提取剂对20 g(或适量)土壤样品中残留的二氯喹啉酸振荡提取2 h,离心过滤后分取滤液25 ml浓缩,甲醇定容至2 ml,再用滤膜过滤后待测定;高效液相色谱仪(HPLC)以1.0 ml/min的甲醇︰1%乙酸水溶液(55︰45,V/V)为流动相,柱温45℃,在238 nm的紫外光波长下进行二氯喹啉酸的外标法定量。该方法精密度为6.0%,检出限为0.012 mg/kg,不同类型土壤的加标回收率74.9%~98.8%,能满足有机分析要求。该方法既简捷易操作,又能满足土壤中二氯喹啉酸低残留量的测定。     

火焰原子吸收光谱法间接测定土壤中有效硫

试验旨在建立火焰原子吸收光谱法间接测定土壤中有效硫,试验原理基于SO42-和BaCrO3溶液反应生成BaSO4沉淀,置换出定量的CrO42-,通过原子吸收法测定Cr,通过换算得知有效硫的含量。试验优化了影响结果的浸提剂、静置时间、陈化时间等因素;通过标准土样的验证,结果可靠、稳定。     

土壤磺胺类抗生素固相萃取-高效液相色 谱法的构建与优化

设计正交试验对红壤中磺胺甲恶唑(sulfamethoxazole, SMZ)的萃取方法进行优化,并结合高效液相色谱,构建了固相萃取-高效液相色谱联合测定法(SPE-HPLC),并将该方法应用于不同抗生素以及不同类型土壤中SMZ的提取测定。结果表明,在以乙腈–磷酸盐缓冲液为提取液、提取液量为10 ml、超声时间为15 min、9 ml甲醇淋洗固相萃取柱(HLB)的条件下,红壤中SMZ的提取效果最优,0.25 mg/kg的SMZ回收率达到85.58%,能够满足环境样品的分析要求。利用该法提取测定红壤中不同抗生素包括3种磺胺类抗生素(磺胺嘧啶、磺胺二甲基嘧啶、磺胺甲基嘧啶)和2种四环素类抗生素(土霉素、盐酸四环素),结果表明,当抗生素浓度为0.25 mg/kg时,磺胺类抗生素(SAs)的回收率范围在67.31%～85.58%,四环素类抗生素(TCs)的回收率范围在20.81%～59.33%。利用该法分别提取测定不同类型土壤中的SMZ回收率,得到潮土中SMZ的回收率最大,达到92.92%,其次为荒漠土、红壤、紫色土,最低的回收率出现在黄棕壤,仅为53.62%。据相关性分析表明,回收率与土壤电导率(EC)、微生物碳氮比(C/N)呈极显著负相关(P0.01),与阳离子交换量(CEC)、有机质(SOM)呈显著负相关(P0.05)     

Rapid High‐Performance Liquid Chromatography Determination of Tocopherols and Tocotrienols in Cereals

A rapid normal‐phase high‐performance liquid chromatography (NP‐HPLC) method has been developed for rapid determination of the total content of tocopherols (T) and tocotrienols (T3) in cereals. The new method uses a one‐step extraction followed by NP‐HPLC coupled with a fluorescence detector. The new method provides a baseline separation of the critical peaks of beta‐tocotrienol (β‐T3) and gamma‐tocopherol (γ‐T) within a short time of analysis. The extraction step requires no saponification step or addition of antioxidant. Addition of butylated hydroxytoluene (BHT) had no effect on the stability of vitamin E during sampling. The recovery was 96–100%. The method is demonstrated by successful quantification of vitamin E in barley, wheat, and spelt grains, as well as wheat germ and flours from wheat, spelt, and rye.     

离心式微流控液相萃取法测定水和土壤中油和油脂

现场便携式快速分析仪测定液体固体中的各种污染物,越来越成为人们的实际需求。如水和土壤中的油和油脂（OG）,会引起环境污染,威胁公共健康。微流控设备,由于其试剂消耗低、成本低、分析时间短、所需能量和空间小、经济、环境安全,使得分析方法发生着潜在的革命性变化,几个环境样品的同时制备和分析都在一个集成光盘上进行的离心式微流控系统分析能力越来越为人们熟知。在磁力驱动下,通过＂可动磁铁＂的有效搅拌完成液相和液固萃取,磁力驱动样品制备单元集合固体分析的沉积/过滤,以及最终液体或固体样品的检测池于一个光盘上,对水和土壤中的OG进行萃取,以四氯乙烯代替氟里昂113和四氯化碳为萃取溶剂,实现了OG的红外法检测,检出限为11μg.mL-1。     

超高效液相色谱串联质谱法同时检测复杂基质中四环素类抗生素及其代谢产物

为同时检测复杂基质中（由猪粪和蘑菇渣混合而成的堆肥原料）3种四环素类抗生素（四环素TC、土霉素OTC和金霉素CTC）及其代谢产物,建立了超高效液相色谱串联质谱检测方法（UPLC—MS／MS）。该方法同时采用pH值=4的Na2EDTA-Mellvaine缓冲溶液和乙腈为提取溶液,经过固相萃取净化后,以乙腈和0．1％的甲酸水溶液为流动相,采用超高效液相色谱柱进行分离,在电喷雾正离子模式下,用四极杆串联质谱仪进行定性和定量分析。3种四环素类抗生素及其代谢产物均在7min内完成分离,总共分析时间为12min。在0-6mg·kg^-1DW（Dryweight）浓度范围内,3种四环素类抗生素及其代谢产物的标准曲线线性良好,线性相关系数R2均大于0．9960,重现l生也较好（n=11,相对标准偏差均小于15％）。在3个加标水平0．2mg·kg^-1DW、1mg·kg^-1DW和4mg·kg^-1DW下,TC、OTC、CTC的回收率分别为71％-89％、66％～94％和66％～84％;去甲基金霉素（DMCTC）的回收率为52％-64％;差向异构产物的回收率在32％～51％之间;脱水产物以及差向脱水产物的回收率均低于30％。3种四环素类抗生素及其代谢产物的检出限和定量限分别在1．668～17．270μg·kg^-1和5．561—45．918μg·kg^-1范围内,表明该方法具有较高的灵敏度。对北京市某露天堆肥场中的样品进行测定发现,TC、OTC、CTC的浓度分别为0．4、1．6、2．9mg·kg^-1,检测到的代谢产物主要为相应的差向异构体,其中差向金霉素（ECTC）的浓度最高,达到2．7mg·kg^-1,和母体的含量水平比较接近,其他代谢产物也有不同程度的检出。