Spectrophotometric flow injection determination of total phosphorus in beer using on-line UV/thermal induced digestion

A flow injection system for the automatic determination of total phosphorus in beer is described. The developed manifold uses a two-stage photooxidation/thermal digestion procedure together with oxidizing and hydrolyzing reagents to convert all forms of phosphorus compounds to orthophosphate. Polyphosphates are hydrolyzed by acid and heat, and organo-phosphates are digested by UV-catalyzed peroxodisulfate oxidation. The orthophosphate formed is then spectrophotometrically determined by the phosphomolybdenum blue reaction, using stannous chloride as reducing agent. The results obtained for a set of 19 beer samples (with concentrations from 120 to 735 mg P/L) were in good agreement with the reference method, the maximum relative deviation found being 4.7%. Relative standard deviations for ten consecutive determinations were lower than 1.5%, and a detection limit of 1 mg P/L was achieved. Received: 18 May 1999 / Revised: 5 July 1999 / Accepted: 7 July 1999     

Determination of total phosphorus in water by photochemical decomposition with ultraviolet irradiation

A simple and convenient photochemical decomposition method has been developed for the determination of total phosphorus in natural and sewage water. Organic phosphorus compounds and inorganic polyphosphates may be completely converted into orthophosphate in the presence of 0.3M sulphuric acid and 0.12% potassium persulphate with 50 min irradiation. The relative standard deviations found for analysis of natural water (P 35 microg/l.) and sewage (P 2.4 mg/l.) were 5.7% and 1.0% respectively. The method gives results comparable to those obtained by digestion with persulphate.     

Determination of total phosphorus in waters with amperometric detection by coupling of flow-injection analysis with continuous microwave oven digestion

For the determination of total phosphorus in waters by flow-injection analysis, a continuous microwave oven decomposition with subsequent amperometric detection of orthophosphate is proposed. The percentage digestion was examined for two different decomposition reagents and by varying the pH of the carrier and the length and diameter of the digestion coil. With potassium peroxodisulphate decomposition the recoveries of phosphorus vary from 91 to 100% for organic phosphorus compounds, and with perchloric acid decomposition the recoveries vary from 60 to 70% for inorganic polyphosphates. Calibration graphs are linear for up to 30 mg P l^?1, the determination limit is 0.1 mg P l^?1 and the precision of the method is 3% (relative standard deviation) (n = 5) at 5 mg P l^?1. The sampling rate is 20 h^?1. Good recoveries of phosphorus after addition to domestic waste water sample are obtained.     

固相萃取-高效液相色谱法同时测定啤酒中的4种异构化α-酸

建立了固相萃取-高效液相色谱同时测定啤酒中4种异构化α-酸的方法。采用Sep-Pak C18萃取柱,系统研究了啤酒中异构化α-酸的最佳固相萃取条件。选择以2 mL酸化甲醇为洗脱溶剂,萃取前调啤酒样品的pH至2.5。该方法准确可靠,重现性好,4种异构化α-酸的回收率为90.6%～96.4%,相对标准偏差小于4%。异α-酸、二氢异α-酸、四氢异α-酸和六氢异α-酸的最低检测限依次为0.14,0.36,0.33和0.53 mg/L。     

Determination of phosphate species in nutrient solutions and phosphorus in plant material as phosphovanadomolybdic acid by flow injection analysis

A flow-injection spectrophotometric method for the determination of orthophosphate is described. The signal from the yellow phosphovanadomolybdic acid complex is recorded at 400 nm. The detection limit is 0.1 mg P 1^?1 (as orthophosphate), the calibration graph is linear up to 30 mg P 1^?1 and up to 240 samples can be analysed per hour. The method is used in the determination of phosphorus in digested plant material, and is also applicable for separating free orthophosphate from acid-labile aluminium phosphate colloids in nutrient solutions.     

Magnetic mixed hemimicelles solid-phase extraction of xanthohumol in beer coupled with high-performance liquid chromatography determination

In this study, silica-coated magnetic nanoparticles (Fe(3)O(4)/SiO(2) NPs) modified by cetyltrimethylammonium bromide (CTAB) were synthesized. They were successfully applied for extraction of xanthohumol in beer based on magnetic mixed hemimicelles solid-phase extraction (MMHSPE) coupled with high-performance liquid chromatography-ultraviolet determination. The main factors influencing the extraction efficiency including the surfactant amount, the beer pH, the extraction time, the desorption condition and the maximum extraction beer volume were optimized. Under the optimized conditions, a concentration factor of 60 was achieved by extracting 120 mL beer sample using MMHSPE and the detection limit of xanthohumol is 0.0006 mg/L. The proposed method was successfully applied for determination of xanthohumol in various beer samples with the xanthohumol contents in the range of 0.031-0.567 mg/L. The satisfactory recoveries (90-103%) were obtained in analyzing spiked beer samples.     

Differential pulse polarographic determination of orthophosphate in aqueous media

The determination of orthophosphate in aqueous media by differential pulse polarography is described. It is based on determination of the molybdenum in 12-phosphomolybdic acid. High sensitivity is achieved by measuring the polarographic wave due to the catalytic reduction of perchlorate or nitrate in the presence of molybdenum(VI). The method is suitable for samples as small as 3.5 ml which contain as little as 9 ng of phosphorus per ml. The average relative deviation is 3.0% at the 0.045 mg/l. phosphorus level and 1.6% at the 1.2 mg/l. level. Results for the analysis of EPA quality-control water and real surface-water samples are reported.     

Characterization of phosphate solubilizing bacteria in sediments from a shallow eutrophic lake and a wetland: isolation, molecular identification and phosphorus release ability determination

The transformation of phosphorus (P) is a major factor of lake eutrophication, and phosphate releasing bacteria play an important role in the release process. Experiments were conducted to investigate P content and characterize phosphate solubilizing bacterial composition at the molecular level in a shallow eutrophic lake and a wetland. Results showed that P concentrations were relatively high and derived from agricultural runoff and domestic or industrial pollution. Enumeration and molecular identification of these strains indicated that these bacterial groups were abundant in the ecosystem and various kinds of bacteria participated in the phosphorus release process. Twelve phosphate solubilizing bacteria, including eight organic P-solubilizing bacteria (OPBs) and four inorganic P-solubilizing bacteria (IPBs), which belonged to three different families, were isolated and identified. Cupriavidus basilensis was found for the first time to have the ability to mineralize organic P (OP). Laboratory tests on P release ability revealed that IPBs were more effective at releasing P than OPBs. The most efficient IPB strain could accumulate over 170 mg·L-1 orthophosphate, while the equivalent OPB strain only liberated less than 4 mg·L-1 orthophosphate in liquid culture. The results obtained from this investigation should help clarify the roles of microorganisms in aquatic systems and the mechanisms of eutrophication.     

Speciation analysis of orthophosphate and myo‐inositol hexakisphosphate in soil‐ and plant‐related samples by high‐performance ion chromatography combined with inductively coupled plasma mass spectrometry

A novel method based on high‐performance ion chromatography inductively coupled plasma mass spectrometry employing strong anion exchange chromatography with HNO₃ gradient elution for simultaneous analysis of orthophosphate and myo‐inositol hexakisphosphate (IP₆) in soil solution and plant extracts is presented. As inductively coupled plasma mass spectrometry analysis of phosphorus at m/z 31 is hampered by N‐based interferences, ³¹P was measured as ³¹P¹⁶O⁺ at m/z 47 employing dynamic reaction cell technique with O₂ as reaction gas. Orthophosphate and IP₆ were separated within a total chromatographic run‐time of 12 min revealing a limit of detection of 0.3 μmol/L. The coefficients of determination obtained in a working range of 1–100 and 1–30 μmol/L were 0.9991 for orthophosphate and 0.9968 for IP₆, respectively. The method was successfully applied to extracts from three different soils as well as root and shoot extracts of Brassica napus L. The precision of three independently prepared soil extracts was in the range of 4–10% relative standard deviation for PO₄^3? and 3–8% relative standard deviation for IP₆. Soil adsorption/desorption kinetics for IP₆/orthophosphate were performed for investigating the sorption behavior of the two P species in the experimental soils.     

流动注射-分光光度法在线全自动测定正磷酸盐

通过将GB/T6913-2008分光光度法在线化,设计研制了正磷酸盐流动注射自动在线监测仪;优化了显色剂浓度、载流液浓度、采样环长度等实验参数,建立了水中正磷酸盐流动注射全自动在线分析方法,并考察了其实际使用效果.结果表明,当待测水样中PO34浓度在0～15.0 mg/L范围内时,吸光度和浓度呈良好的线性关系,检出限为...     

Characterization of Plant Seeds by Phosphorus-31 Nuclear Magnetic Resonance Spectroscopy

Plant seeds accumulate and store phosphorus for the initial growth of seedlings. Phosphorus speciation by ³¹P nuclear magnetic resonance spectroscopy of NaOH–EDTA seed extracts showed that P was mainly present in organic forms such as phytate and α- and β-glycerophosphate in poppy, sesame, mustard, fennel, and cumin seeds. The inorganic P forms present included orthophosphate and pyrophosphate. The highest concentration of orthophosphate was found in NaOH–EDTA extracts of fennel seeds (41.7%) and the lowest in mustard (9.3%) and sesame seeds (6.9%). For the organic P forms, the highest concentration of phytate was found in mustard seeds (85.2%) and the lowest in fennel seeds (43.3%). Other organic P forms detected were α- and β-glycerophosphate ranging from 1.2 to 5.1% and 0.7 to 2.1%, respectively. Pyrophosphate was detected in trace amounts only in fennel (0.7%) and poppy seeds (0.5%). The only orthophosphate diester observed was in sesame seeds at a low concentration (0.7%), while phosphonates and polyphosphates were not present in any seeds. Phytate was the most dominant P form in all seeds except for fennel and cumin, which contained the lowest phytate concentration but the highest orthophosphate and glycerophosphate concentrations. These results suggest that P transferred from the plant vegetative parts to the developing seeds during maturation is converted to phytate (organic P) in addition to being stored as orthophosphate (inorganic P).     

Sequential injection spectrophotometric determination of orthophosphate in beverages, wastewaters and urine samples by electrogeneration of molybdenum blue using tubular flow-through electrodes

A novel and automated sequential injection procedure is proposed for the spectrophotometric determination of orthophosphate without requiring unstable chemical reducing species used in the classical molybdenum blue method. The flowing methodology is based on the on-line generation of the detectable species by electrochemical reduction of the 12-molybdophosphoric acid complex using a stainless steel tubular flow-through working electrode. The established method is linear up to 20 mg/l P, with coefficients of variation (n=10) of 2.4 and 1.8% for 2.0 and 10 mg/l P, respectively. The versatility of the sequential injection method to analyse samples containing high orthophosphate levels has been demonstrated by the implementation of a dilution chamber as well as flow-reversal techniques, yielding relative standard deviations (n=17) better than 2.0% for standards containing 200 and 800 mg/l P. The proposed analyser features an extremely wide dynamic range (viz., 0.3-800 mg/l) as well as improved tolerance to silicate interference, so that Si/P ratios higher than 50 are tolerated at the 5% level. Electrochemical conditions, reagent concentrations and physical variables have been thoroughly investigated. The method has been applied to the determination of orthophosphate in wastewaters as well as beverages and biological samples containing high concentrations of the target analyte. The t-test comparison of the means for the developed sequential injection system with electroreduction and both the molybdenum blue classical spectrophotometric batch procedure and inductively coupled plasma-optical emission spectrometric detection selected as external reference methods revealed that there is no evidence of significant differences between the obtained results at the 95% confidence level.     

电感耦合等离子体发射光谱法测定磷石膏中的水溶性五氧化二磷

建立电感耦合等离子发射光谱法(ICP–OES)测定磷石膏中水溶性五氧化二磷含量的方法。用超声波快速提取磷石膏中的磷,在178.284 nm波长下,用CID固体检测器测定样品溶液的光谱强度。五氧化二磷的质量浓度在0.007~200 mg/L范围内与光谱强度线性关系良好,线性相关系数r=0.999 96,检出限为0.006 9 mg/L。样品加标回收率在98%~102%之间,测定结果的相对标准偏差为0.95%~1.11%(n=6),该方法的测定结果与国标法基本一致。该法简便、快速,适合磷石膏中水溶性五氧化二磷的测定。     

微流池多光程土壤有效态氮磷测定方法研究

农业面源氮磷污染是当前地表水体污染主要来源,而土壤有效态氮磷测试大都依赖于流动分析仪在实验室完成,无法满足个性化土壤有效态氮磷现场测定需求。建立了一种微流池多光程的土壤有效态氮磷测定技术,通过柔性化参数设置,实现不同土壤有效态氮磷测试规范和现场测试。以广东省韶关市农业科学研究所和北京市农林科学院提供的26个样品为例进行有效态铵态氮、硝态氮和磷测定验证。实验结果表明,微流池多光程土壤有效态氮磷测定方法中有效态铵态氮、硝态氮和磷的检出限(LOD)分别为0.0086、0.0094和0.0078 mg/L,相对标准偏差(RSD)分别为0.80%、5.7%和0.90%,加标回收率在92.0%~103%,平均单样品测试时间6 min。测试过程自动化,极大地提升了土壤有效态氮磷测定效率和测试结果准确性,为农业面源污染防治提供技术支撑。     

A multi-pumping flow system with on-line photochemical conversion and improved sensitivity for phosphorus fractionation in freshwaters

A flow-based procedure with solenoid micro-pumps was developed for phosphorus fractionation (dissolved organic and inorganic phosphorus) in freshwaters. The spectrophotometric detection was based on the formation of molybdenum blue and the organic species were on-line photo-converted to orthophosphate. The analytical response was linear within 10 and 75?µg?L^?1 with a detection limit of 2.0?µg?L^?1 (99.7% confidence level). Coefficient of variation of 1.8% (50?µg?L^?1 P, n?=?20) and sampling rate of 40 determinations per hour were achieved. Per determination, 160?µg (NH₄)₆Mo₇O₂₄, 10?µg SnCl₂, 640?µg K₂S₂O₈ and 10?mg NaOH were consumed, generating 2.0?mL of waste. Slopes of analytical curves obtained for four different organic phosphorus species agreed with those obtained for orthophosphate, indicating quantitative conversion. The results for freshwater samples agreed with those obtained by the AOAC reference procedure at 95% confidence level. The organic matter did not interfere in the photo-oxidative process. The proposed procedure is a fast and environmentally friendly alternative for the phosphorus fractionation in freshwaters.     

Constant-current potentiometric titration of orthophosphate with cetylpyridinium chloride: a feasibility study

The feasibility of constant-current potentiometric titration of orthophosphate with cetylpyridinium chloride has been studied. The phosphate solution is acidified with hydrochloric acid to pH 1.1-1.3 and an excess of molybdate solution added. For l mg of phosphorus (as phosphate) the optimum Mo:P ratio is about 40. Cetylpyridinium chloride reacts stoichiometrically with 12-molybdophosphate, in 3:1 ratio. The optimum cathodic polarizing current is 1.1 muA. The blanks for molybdate are relatively small, constant and non-stoichiometric.     

Separation and quantification of beer carbohydrates by high-performance liquid chromatography with evaporative light scattering detection

An HPLC method with an evaporative light scattering detector was optimized and validated for quantification of carbohydrates in beer. The chromatographic separation was achieved using a Spherisorb NH2, 5 microm chromatographic column and gradient elution with acetonitrile/water. The determinations were performed in the linear range of 0.05-5.0 g/L for fructose, 0.05-5.0 g/L for glucose, 0.05-15.0 g/L for maltose, 0.05-10.0 g/L for maltotriose, and 0.05-5.0 g/L for maltotetraose. The detection limits were 0.005 g/L for fructose, 0.008 g/L for glucose, and 0.01 g/L for maltose, maltotriose, and maltotetraose. The reliability of the method in terms of precision and accuracy was evaluated in three beer matrices, low alcohol beer, 6% alcohol beer, and beer made with part of adjuncts (4.5% alcohol). Relative standard deviations (RSDs) ranged between 1.59 and 5.95% (n = 10), and recoveries ranged between 94 and 98.4%.     

Retention of pesticides and nutrients in a vegetated buffer root zone compared to soil with low biological activity

A laboratory study has been conducted to examine the retention processes of nitrogen and pesticides through vegetated buffer zones compared to bare soil. Soil columns with low biological activity and vegetation columns with normal biological activity were tested. Pesticides frequently used in vegetable production (namely aclonifen, azinphos-methyl, chlorpropham, diazinon, dimethoate, fluazinam, iprodione, linuron, metalaxyl, metamitron, metribuzin and propachlor) equal to 1/50 to 1/5 part of recommended doses, and nutrients equal to 1, 5 and 20 mg N/L and 0.2 mg P/L, were added. The pesticide retention was more than 60% for all pesticides, except dimethoate, with a retention of about 30% in columns with low microbial activity. Biological transformation and plant uptake were important for removal of nitrogen and organic matter. Nitrogen retention was high (over 90%) in vegetation columns. Plant uptake and phosphorus content in soil were important for phosphorus retention.     

基于冷冻熔炼的液-液萃取/气相色谱法测定啤酒中的N-二甲基亚硝胺

建立了一种新型的冷冻熔炼液-液萃取法直接提取啤酒中的N-二甲基亚硝胺（N-nitrosodimethylamine,NDMA）,萃取液经GC-FID分析,双柱法定性,外标法定量。优化的前处理条件为：以二氯甲烷为萃取溶剂,啤酒样品和萃取溶剂的体积比为9：1,-19 ℃下冷冻16 h。结果表明：NDMA在5~200 mg/L范围内具有良好的线性关系（r²=0.9996）;在5、10和20 mg/L 3个加标水平下的回收率分别为84.94%、83.24%、85.14%,平行7次测定的相对标准偏差（RSD）分别为3.06%、3.19%、2.63%。与常规液-液萃取方法（需要经过蒸馏、萃取、旋蒸、氮吹4个步骤）相比,本方法稳定、可靠,且操作简单,有机溶剂消耗量少。     

Spectrophotometric determination of orthophosphate ions for conducting indicator investigations in stratal waters

The methodologies for determining orthophosphate ions by spectrophotometry and flow-injection analysis for 1995?C2011 in different features are briefly described in the paper. The method of the spectrophotometric determination of orthophosphate in the form of molybdophosphoric heteropolyacid via reduced ascorbic acid in the presence of potassium antimonyl tartrate has been modified. The method allows analysts to determine 0.1?C1.0 mg/L of orthophosphate ions in natural waters and has been tested by analyzing a model solution similar to the subterraneous waters of the Arigol licensed area. The advantages of the developed method, compared to the certified method, consist of the possibility of the express assessment and lower consumption of chemical reagents. The method is suitable for indicator investigations in geophysics.