Optimization of microwave digestion for mercury determination in marine biological samples by cold vapour atomic absorption spectrometry

Optimization of acid digestion method for mercury determination in marine biological samples (dolphin liver, fish and mussel tissues) using a closed vessel microwave sample preparation is presented. Five digestion procedures with different acid mixtures were investigated: the best results were obtained when the microwave-assisted digestion was based on sample dissolution with HNO3-H2SO4-K2Cr2O7 mixture. A comparison between microwave digestion and conventional reflux digestion shows there are considerable losses of mercury in the open digestion system. The microwave digestion method has been tested satisfactorily using two certified reference materials. Analytical results show a good agreement with certified values. The microwave digestion proved to be a reliable and rapid method for decomposition of biological samples in mercury determination.     

TXRF法测定松花粉中的9种生命元素

建立了微波消解前处理,全反射X射线荧光法(TXRF)同时测定松花粉中K、Ca、Ti、Mn、Fe、Ni、Cu、Zn和Rb9种生命元素含量的分析方法.松花粉原料经过微波消解前处理后,采用全反射X射线荧光光谱净计数、QXAS分析软件解谱和单一内标法进行定量分析.比较了干灰化法、湿消解法和微波消解法3种前处理方法的效果,并确立微波消解法作为样品前处理方法.用微波消解- TXRF法测定了花粉标准物质中的上述9种元素,并计算得到其仪器检出限(LLD)为0.002～0.054 mg/L,方法检出限(LDM)为0.004～0.122 mg/kg.TXRF法测定各元素的相对标准偏差(RSDs)为1.0％～5.5％.该方法操作简单、样品用量少、检出限低,对实际样品松花粉的测定结果与ICP - MS法无显著性差异.     

土壤中铅的分析方法比对

对不同的样品消解方法及电感耦合等离子体质谱、电感耦合等离子体原子发射光谱、石墨炉原子吸收光谱法测定土壤中铅的测定结果进行比对。采用电热板、微波及水浴3种加热方式,选择硝酸、氢氟酸、双氧水、王水、高氯酸、盐酸的不同组合进行土壤样品消解,通过分析测定值的精密度和准确度,考察消解体系对电感耦合等离子体质谱、电感耦合等离子体发射光谱、石墨炉原子吸收光谱法测定结果的影响。结果表明采用电感耦合等离子体质谱法测定土壤中的铅,最适宜的消解体系是硝酸-氢氟酸-高氯酸(微波加热),采用电感耦合等离子体原子发射光谱法测定最适宜的消解体系是硝酸(电热板加热),采用石墨炉原子吸收光谱法测定最适宜的消解体系是硝酸-盐酸-高氯酸(微波加热)。电感耦合等离子体质谱法的精密度和准确度优于另外两种方法。     

Enzymatic determination of choline in milk using a FIA system with potentiometric detection

The development of a FIA system for the determination of total choline content in several types of milk is described. The samples were submitted to hydrochloric acid digestion before injection into the system and passed through an enzymatic reactor containing choline oxidase immobilised on glass beads. This enzymatic reaction releases hydrogen peroxide which then reacts with a solution of iodide. The decrease in the concentration of iodide ion is quantified using an iodide ion selective tubular electrode based on a homogeneous crystalline membrane. Validation of the results obtained with this system was performed by comparison with results from a method described in the literature and applied to the determination of total choline in milks. The relative deviation was always < 5%. The repeatability of the method developed was assessed by calculation of the relative standard deviation (RSD) for 12 consecutive injections of one sample. The RSD obtained was < 0.6%.     

Evaluation of closed-vessel microwave digestion method for the determination of trace impurities in polymer-based photoresist by inductively coupled plasma mass spectrometry

A closed microwave digestion method followed by inductively coupled plasma spectrometric (ICP-MS) analysis was evaluated for the determination of trace impurities in photoresist. To optimize the digestion procedure, several digestion parameters such as acid, heating temperature and heating time were evaluated. Besides, the digestion efficiency of used photoresist material and the recovery of analyte elements obtained by the use of gravimetric method and ICP-MS measurement, individually, were also compared to clarify the completeness of digestion. According to our experiments, the gravimetric method was found to be not so relevant to the completeness of digestion, because the remaining sample matrix could cause suppression effect in the subsequent ICP-MS measurement. In view of minimizing blank value and working time, a simple single-step heating program was proposed to mineralize 0.25 ml of photoresist material with 5 ml of nitric acid at 180 °C for 10 min. Based on the comparative study of the analytical results obtained by instrumental neutron activation analysis (INAA) and proposed method, the reliability of proposed method for the determination of trace metallic impurities in photoresist material has been confirmed.     

Simultaneous Determination of Total Nitrogen and Metal Elements in Tobaccos by High Performance Ion Chromatography

A simple method, developed primarily for simultaneous determination of total nitrogen and inorganic cations by high performance ion chromatographic (HPIC), was optimized for digestion of flue‐cured tobaccos, and compared with the traditional Kjeldahl method and atomic absorption spectrometry (AAS). Nitrogen determination by either Dumas method or Kjeldahl method is time‐consuming and tedious. Metal elements determination by either inductively coupled plasma‐mass spectrometry (ICP‐MS) or AAS may be more expensive and requires specialist equipment. The use of HPIC to simultaneous determine total nitrogen as ammonium ion and metal elements as inorganic cations after sample digestion significantly improves the speed of the analysis compared with the conventional methods. The cation‐exchange column and suppressed conductivity detector was used for determination of ammonium and inorganic cations in the presence of the elevated levels of sulfuric acid found in digested sample. The propsoed digestion method was accurate and precise, and required little investment. The determination of ammonium and inorganic cations was linear from 15 pg·L^?1 up to 25 ng·L^?1. The results obtained by the HPIC method were compared with those for the conventional methods approach for the determination of total nitrogen and metal elements. The application of the HPIC method is also demonstrated for a variety of other plant samples matrices.     

Ultrasound assisted pseudo-digestion for determination of iron and manganese in citric acid fermentation mediums by electrothermal atomic absorption spectroscopy

A sensitive, simple and rapid method for ultra-trace determination of iron and manganese based on ultrasound assisted pseudodigestion in citric acid fermentation medium samples (beet and cane molasses and raw sugar based mediums) is described. Parameters influencing pseudo-digestion, such as sonication time, sample mass and solvent system were fully optimized. Final solutions obtained upon sonication were analyzed by electrothermal atomic absorption spectrometry (ETAAS). The best conditions for metal pseudo-digestion were as follows: a 25, 30 and 20 min sonication time for beet molasses, cane molasses and raw sugar based medium samples, respectively, 0.7 g sample mass of raw sugar based samples, 0.5 g sample mass of molasses based samples and an extraction mixture of concentrated HNO₃-H₂O₂, in 25 mL of solvent. Analytical results obtained for the two metals by ultrasound assisted pseudo-digestion and conventional wet digestion methods showed a good agreement. This method reduces the time required for all treatments (heating to dryness, cooling and separation) in comparison with conventional wet digestion method. The accuracy of the method was tested by comparing the obtained results with that of conventional wet digestion method.      

Mealworm Oil (MWO) Enhances Wound Healing Potential through the Activation of Fibroblast and Endothelial Cells

Mealworm and mealworm oil (MWO) have been reported to affect antioxidant, anti-coagulation, anti-adipogenic and anti-inflammatory activities. However, the function of MWO in wound healing is still unclear. In this study, we found that MWO induced the migration of fibroblast cells and mRNA expressions of wound healing factors such as alpha-smooth muscle actin (α-SMA), collagen-1 (COL-1) and vascular endothelial growth factor (VEGF) in fibroblast cells. The tube formation and migration of endothelial cells were promoted through the activation of VEGF/VEGF receptor-2 (VEGFR-2)-mediated downstream signals including AKT, extracellular signal-regulated kinase (ERK) and p38 by MWO-stimulated fibroblasts for angiogenesis. Moreover, we confirmed that MWO promoted skin wound repair by collagen synthesis, re-epithelialization and angiogenesis in an in vivo excisional wound model. These results demonstrate that MWO might have potential as a therapeutic agent for the treatment of skin wounds.     

微波消解同时衍生化GC-MS法测定血浆中脂肪酸的研究

研究了利用微波能对样品进行加热, 以Ｈ２ＳＯ４ － 甲苯－ 甲醇体系作衍生化试剂, 在消化的同时对血浆中的脂肪酸进行衍生化, 然后用ＧＣ－ ＭＳ 法测定血浆中脂肪酸。 对微波功率、微波加热时间、消解及衍生化试剂等条件进行了优化, 测定结果较好。该法整个消化及衍生化过程只需２ ｍｉｎ , 与传统方法相比大大缩短了实验操作时间, 特别适用于大量样品的测定。     

微波消解技术在农业样品分析中的应用

利用光纤压力自控密闭微波消解系统对土壤和植株样品中重金属元素测定的影响进行了研究，确立了样品消解试剂、微波消解每件及样品预处理方法。结果表明，该方法与常压湿法消解相比，具有样品消解时间短、消解试剂用量少、样品污染小等特点，是准确可靠的土壤及植株样品中重金属元素检测样品消解处理方法。     

微波消解-电感耦合等离子体发射光谱法测定土壤中的硫

利用微波消解仪消解土壤样品,采用电感藕合等离子体发射光谱仪测定土壤中硫的含量。以浓王水为消解试剂,对土壤样品进行微波消解,优化了王水用量,考察了微波消解条件、谱线干扰情况和仪器参数对硫灵敏度的影响。硫的质量浓度在0~40 mg/L范围内与光谱强度具有良好的线性关系,线性相关系数为0.9997,硫的检出限为0.053 mg/L。土壤中硫测定结果的相对标准偏差为1.54%~7.84%(n=7)。对六种土壤国家一级标准物质进行了测定,测定结果与推荐值相符,无显著性差异。该方法简便、准确,分析效率高,能够满足日常批量样品分析的要求。     

Comparative determination of Ba, Cu, Fe, Pb and Zn in tea leaves by slurry sampling electrothermal atomic absorption and liquid sampling inductively coupled plasma atomic emission spectrometry

The comparative determination of barium, copper, iron, lead and zinc in tea leaf samples by two atomic spectrometric techniques is reported. At first, slurry sampling electrothermal atomization atomic absorption spectrometry (ETAAS) was applied. The results of Ba and Pb determination were calculated using the method of standard additions, and results of Cu, Fe and Zn from the calibration graphs based on aqueous standards. These results were compared with the results obtained after microwave-assisted wet (nitric+hydrochloric+hydrofluoric acids) digestion in closed vessels followed by inductively coupled plasma-atomic emission spectrometric (ICP-AES) determination with the calibration by means of aqueous standards. The exception was lead determined after a wet digestion procedure by ETAAS. The accuracy of the studied methods was checked by the use of the certified reference material Tea GBW-07605. The recoveries of the analytes varied in the range from 91 to 99% for slurry sampling ETAAS, and from 92.5 to 102% for liquid sampling ICP-AES. The advantages of slurry sampling ETAAS method are simplicity of sample preparation and very good sensitivity. Slurry sampling ETAAS method is relatively fast but if several elements must be determined in one sample, the time of the whole microwave-assisted digestion procedure and ICP-AES determination will be shorter. However, worse detection limits of ICP-AES must also be taken into the consideration in a case of some analytes.     

Microwave digestion and matrix separation for the determination of cadmium in urine samples by electrothermal atomization atomic absorption spectrometry using a fast temperature program

 A method is proposed which involves sample pretreatment followed by electrothermal atomic absorption spectrometry (ETAAS) for determination of cadmium in human urine. A microwave digestion system was devised to accommodate double-closed vessels for simultaneous digestion of batches of up to 24 urine samples in about 20 min. After digestion, matrix substances which might interfere were removed using silica-immobilized 8-hydroxyquinoline (I-8HOQ) columns. The analyte adsorbed on the column was then eluted with dilute nitric acid solution and determined by ETAAS using a fast temperature program. Neither ashing steps in the furnace heating program nor use of matrix modifiers was necessary. The accuracy, precision, limit of detection, and sample throughput of the method were evaluated. With meticulous control of systematic errors which may be introduced in the pretreatment procedures, the present method can serve as a reference technique for the analysis of Cd in urine samples. Received: 29 July 1996/Revised: 30 September 1996/Accepted: 13 October 1996     

Microwave digestion and matrix separation for the determination of cadmium in urine samples by electrothermal atomization atomic absorption spectrometry using a fast temperature program

 A method is proposed which involves sample pretreatment followed by electrothermal atomic absorption spectrometry (ETAAS) for determination of cadmium in human urine. A microwave digestion system was devised to accommodate double-closed vessels for simultaneous digestion of batches of up to 24 urine samples in about 20 min. After digestion, matrix substances which might interfere were removed using silica-immobilized 8-hydroxyquinoline (I-8HOQ) columns. The analyte adsorbed on the column was then eluted with dilute nitric acid solution and determined by ETAAS using a fast temperature program. Neither ashing steps in the furnace heating program nor use of matrix modifiers was necessary. The accuracy, precision, limit of detection, and sample throughput of the method were evaluated. With meticulous control of systematic errors which may be introduced in the pretreatment procedures, the present method can serve as a reference technique for the analysis of Cd in urine samples. Received: 29 July 1996/Revised: 30 September 1996/Accepted: 13 October 1996     

Rapid determination of chemical oxygen demand using a focused microwave heating system featuring temperature control

This paper demonstrates the use of a microwave heating system, employed in the chemical digestion step, for the determination of chemical oxygen demand in wastewater. The results are first compared with those provided by standard methods using reference substances. The problems arising from abrupt heating of the sample and the potential thermal decomposition of potassium dichromate are examined. Two different approaches to sample digestion involving a gradually increasing irradiation time were tested. First, a constant power strategy is applied, and the second proposes a constant temperature approach by using a temperature control system.By optimising the operating conditions, the digestion time was reduced to 8-60 times with respect to the standard method. The reference digestion time is 5 min. In especially difficult digestions, the proposed approach provides a substantially improved degradation with respect to conventional procedures. The procedure was applied to wastewater from various industries and found to ensure thorough digestion of all samples and to provide favourable results in all cases tested.     

Determination of selenium, zinc and cadmium in antidandruff shampoos by atomic spectrometry after microwave assisted sample digestion

Microwave assisted pre-treatments for atomic spectrometric determination (inductive coupled plasma-optical emission spectrometry, ICP-OES or flame atomic absorption spectrometry, FAAS) of metallic elements, usually present in antidandruff shampoos, are proposed. They are based on the digestion of the sample with HNO₃ into a closed reactor, which is irradiated at 800 W for a few minutes. Selenium was determined by ICP-OES. The limit of detection was 0.11 mg l⁻¹; the relative standard deviation (R.S.D.) for the selenium content in the samples was in the 0.6–3.6% range. The results obtained were in agreement with the label contents and the recovery of the proposed method was in the 100–106% range. Zinc and cadmium were determined by FAAS. The limit of detection for zinc determination was 0.078 mg l⁻¹; the R.S.D. for zinc contents was in the 0.8–8.6% range. A limit of detection of 0.09 mg l⁻¹ was obtained for cadmium determination; the R.S.D. for cadmium contents was in the 0.7–2.7% range. The determinations were performed after two different sample mineralization pre-treatments — dry ashing (in an electric furnace) and wet mineralization (in a microwave oven). Both methodologies provided comparable results for zinc and cadmium determination in shampoos. The proposed microwave assisted digestion procedures allow a precise and accurate determination of selenium, zinc and cadmium in commercial antidandruff shampoos, and the sample pre-treatment is less time-consuming than the classic methods.     

微波消解分光光度法测定污水中的总磷

建立微波消解分光光度法测定污水中总磷的方法。采用微波消解法消解污水．讨论了消解时间和压力对消解效果的影响。测定总磷的线性范围为0～0．4mg/L。用该法测定总磷环境标准样品中的总磷,测定结果与标准值基本一致,测定结果的相对标准偏差为1．65％(n=5)。     

Determination of Pt from coke samples by ICP-MS after microwave assisted digestion and microwave assisted cloud point extraction

Platinum in coke samples was determined by inductively coupled plasma mass spectrometry (ICP-MS) after microwave-assisted sample digestion and temperature controlled microwave assisted cloud point extraction (MW-CPE). Interferences due to hafnium (¹⁷⁹Hf¹⁶O) were successfully eliminated using MW-CPE with 2-MBT prior to the determination of platinum by ICP-MS. The validity of the method was studied by spike recovery tests and by analyzing certified reference material (BCR-723 street dust). The results obtained for platinum in the BCR-723 were generally in good agreement with the certified values. Furthermore, the preliminary platinum results obtained for coke sample by ICP-MS after MW-CPE were compared to those obtained by a reference method (NiS-Fire Assay preconcentration/Te coprecipitation and ICP-MS determination).     

电感耦合等离子体发射光谱法测定地质样品中的钨、钼、锡

改进了电感耦合等离子体发射光谱法(ICP-AES)同时测定多金属矿石等地质勘查样品中钨、钼、锡的溶样方法。采取酸溶和碱熔结合,先用硝酸和高氯酸及氢氟酸溶样,用盐酸(1+1)浸取再过滤,滤渣及滤纸灰化后再碱熔,最后用电感耦合等离子体发射光谱法(ICP-AES)测定钨、钼、锡。克服了传统的酸溶法导致锡的测定结果偏低和碱熔法易堵塞ICP-AES矩管和雾化器的两大弊端,方法经国家一级标准物质验证,精密度和准确度均能达到日常分析的要求。     

A new approach of direct sample-digestion before vaporization for determination of a metal in rocks by inductively coupled plasma atomic emission spectrometry.

A new approach to sample digestion, subsequent vaporization and introduction to an inductively coupled plasma (ICP) atomic emission spectrometer was developed for the direct determination of magnesium. To each small sample cuvette made of tungsten, a ground rock sample was precisely weighed. The cuvette was situated on a tungsten boat furnace. Ammonium fluoride solution was added to the cuvette as a chemical modifier. After the on-furnace digestion has been completed, the analyte, magnesium, in the cuvette was vaporized and introduced into the ICP atomic emission spectrometer. Since the powdered samples were wet-digested in the sample cuvettes prior to vaporization, they could be analyzed by using a calibration curve prepared from aqueous standard solutions. This method was applied to the determination of magnesium in several standard reference materials with satisfactory results.