ICP-MS法和GF-AAS法检测乳粉中铬元素的测量系统评价

铬元素是食品质量安全重点监测项目,GB 5009.123—2023《食品安全国家标准食品中铬的测定》中规定了食品中铬的2种常用检验方法:石墨炉原子吸收光谱(graphite furnace atomic absorption spectrometry,GF-AAS)法和电感耦合等离子体质谱(inductively coupled plasma mass spectrometry,ICP-MS)法。使用Minitab统计分析工具,运用控制图法、独立样件法、t检验法及方差分析法对上述2种常用检验方法测量系统的稳定性、偏倚、线性、重复性与再现性进行分析。结果表明:2种检测方法测量系统极差图和均值图均无异常点,组内误差处于统计受控状态,稳定性良好;量具线性和偏倚分析结果均不存在显著偏倚和显著线性误差;量具R&R报告分析结果表明,ICP-MS法和GF-AAS法测量系统重复性和再现性良好;双因子方差分析表明,样品是唯一显著影响测量误差的因子;研究变异分析表明,测量系统误差可以接受。ICP-MS法和GF-AAS法不仅能有效保障乳粉中铬元素含量检测数据的可靠性和可重复性,为实验室进行测量系统的误差分析与控制提供科学依据,同时也为乳制品中其他重金属检测及其他食品中重金属检测的测量系统评价提供一定参考。

GF-AAS与ICP-MS测定水中总铬含量的方法比对及其不确定度评定

石墨炉原子吸收光谱(GF-AAS)法和电感耦合等离子体质谱(ICP-MS)法是灵敏度较高的2种测定水中铬含量的方法。文中采用357.9 nm与429.0 nm波长条件下GF-AAS法、52与53质核比条件下ICP-MS法测定水质铬标准物质中总铬元素含量,从标准曲线、准确性、重复性、加标回收率、检出限、定量限、测量不确定度评定多个方面进行对比分析。结果表明,4组测定条件下,标准物质测定结果均在标准值不确定度范围内。其中,429.0 nm波长GF-AAS法测定结果相对其他3组显著偏低(P<0.05);ICP-MS法在检出限、定量限方面优于GF-AAS法;GF-AAS法测定结果357.9 nm波长优于429.0 nm波长。

Formation mechanism of the graphite-rich protective layer in blast furnace hearths

A long campaign life of blast furnaces is heavily linked to the existence of a protective layer in their hearths. In this work, we conducted dissection studies and investigated damage in blast furnace hearths to estimate the formation mechanism of the protective layer. The results illustrate that a significant amount of graphite phase was trapped within the hearth protective layer. Furthermore, on the basis of the thermodynamic and kinetic calculations of the graphite precipitation process, a precipitation potential index related to the formation of the graphite-rich protective layer was proposed to characterize the formation ability of this layer. We determined that, under normal operating conditions, the precipitation of graphite phase ~om hot metal was thermodynamically possible. Among elements that exist in hot metal, C, Si, and P favor graphite precipitation, whereas Mn and Cr inhibit this process. Moreover, at the same hot-face temperature, an increase of carbon concentration in hot metal can shorten the precipitation time. Finally, the results suggest that measures such as reducing the hot-face tem- perature and increasing the degree of carbon saturation in hot metal are critically important to improve the precipitation potential index.

Determination of vanadium in food and traditional Chinese medicine by graphite furnace atomic absorption spectroscopy

Various experimental conditions were described for the vanadium determinationby graphite furnace atomic absorption spectroscopy (GFAAS). The experiments showed that whenatomization took place under the conditions where the combination of a pyrolytic coating graphitetube and fast raising temperature were used and the temperature was stable, the signal peak shapescould be improved, the sensitivity was enhanced, and the memory effect was removed. The vanadium infood and traditional Chinese medicinal herbs can be accurately determined using the standard curvemethod.

Determination of Trace Amounts of Nickel (Ⅱ) by Graphite Furnace Atomic Absorption Spectrometry Coupled with Cloud Point Extraction

A new method based on the cloud point extraction（CPE） for separation and preconcentration of nickel（Ⅱ） and its subsequent determination by graphite furnace atomic absorption spectrometry（GFAAS） was proposed, 8-hydroxyquinoline and Triton X-100 were used as the ligand and surfactant respectively. Nickel（Ⅱ） can form a hy-drophobic complex with 8-hydroxyquinoline, the complex can be extracted into the small volume surfactant rich phase at the cloud point temperature（CPT） for GFAAS determination. The factors affecting the cloud point extraction, such as pH, ligand concentration, surfactant concentration, and the incubation time were optimized. Under the optimal conditions, a detection limit of 12 ng/L and a relative standard deviation（RSD） of 2.9% were obtained for Ni（Ⅱ） determination. The enrichment factor was found to be 25. The proposed method was successfully applied to the determination of nickel（Ⅱ） in certified reference material and different types of water samples and the recovery was in a range of 95%―103%.

Preconcentration of Vanadium(Ⅴ) on Crosslinked Chitosan and Determination by Graphite Furnace Atomic Absorption Spectrometry

A new method is proposed for the preconcentration of vanadium(Ⅴ) with crosslinked chitosan (CCTS) and determination by graphite furnace atomic absorption spectrometry (GFAAS). The adsorption rate of vanadium(Ⅴ) by CCTS was 97% at pH 4.0, and vanadium(Ⅴ) was eluted from crosslinked chitosan with 2 mL 2.0 mol·L -1 chlorhydric acid and determined by GFAAS. The detection limit (3σ,n=7) for vanadium(Ⅴ) was 4.8×1 0 -12g and the relative standard deviation (R.S.D) at concentration level of 2.6 μg·L -1 is less than 3.6%. The method shows a good selectivity and high sensitivity, and it was applied to determination of vanadium(Ⅴ) in oyster and water samples. The analytic recoveries are (97±5)%.

A Study of the Background Absorption of Chitosan in the Graphite Furnace Atomic Absorption Spectrometry

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Determination of Trace Iron in High Purity Sodium Fluoride by Graphite Furnace Atomic Absorption Spectrometry

A method is described for the direct determination of iron in high purity sodium fluoride using graphite furnace atomic absorption spectrometry. Interferences caused by the matrix are investigated. It is shown that the ashing temperature can be increased to 1 400°C and matrix interferences eliminated, the sensitivity of iron increased in 1. 27 fold by the addition of nickel nitrate. The method is applied to the determination of iron in sodium fluoride and satisfactory results are obtained.

Determination of Trace Amounts of Lead by Modified Graphite Furnace Atomic Absorption Spectrometry after Liquid Phase Microextraction with Pyrimidine-2-thiol

The liquid phase microextraction (LPME) was combined with the modified Graphite furnace atomic absorption spectrometry (GF-AAS) for determination of lead in the water and solid samples. In a preconcentration step, lead was extracted from a 2 ml of its aqueous sample in the pH = 5 as lead-Pyrimidine-2-thiol cationic complex into a 4 μl drop of 1,2 dichloroethane and ammonium tetraphenylborate as counter ion immersed in the solution. In the drop, the lead-Pyrimidine-2-thiol ammonium tetraphenylborate ion associated complex was formed. After extraction, the microdrop was retracted and directly transferred into a graphite tube modified by [W.Pd.Mg] (c). Some effective parameters on extraction and complex formation, such as type and volume of organic solvent, pH, concentration of chelating agent and counter ion, extraction time, stirring rate and effect of salt were optimized. Under the optimum conditions, the enrichment factor and recovery were 525% and 94%, respectively. The calibration graph was linear in the range of 0.01 - 12 μg?L–1 with correlation coefficient of 0.9975 under the optimum conditions of the recommended procedure. The detection limit based on the 3Sb criterion was 0.0072 μg?L–1 and relative standard deviation (RSD) for ten replicate measurement of 0.1 μg?L–1 and 0.4 μg?L–1 lead was 4.5% and 3.8% respectively. The characteristic concentration was 0.0065 μg?L–1 equivalent to a characteristic mass of 26 fg. The results for determination of lead in reference materials, spiked tap water and seawater demonstrated the accuracy, recovery and applicability of the presented method.

Fe-Si droplets associated with graphite on blast furnace coke

Fe-Si droplets on the surface of blast furnace （BF） coke from 25 to 50 cm at the tuyere level are mostly composed of Fe3Si, which has various shapes （round, elongated, and irregular） and penetration degrees into the BF coke matrix. The shapes and penetration degrees may depend on the saturation of molten iron by silicon during interaction with the coke matrix. The droplets are covered by a tiny shell of carbon. Graphite observed inside the droplets can be divided into two categories： well-formed tabular crystals with relatively large size and flakes with structures similar as those in cast iron. The textures of the droplets reflect composition, interaction with the coke matrix, and cooling conditions.

Background Absorption of TmCl_3 and Tm(NO_3)_3 Matrices in Graphite Furnace Atomic Absorption Spectrometry

The effects of background absorption of TmCl 3 and Tm(NO 3) 3 matrices in graphite furnace atomic absorption spectrometry(GFAAS) were inverstigated. The experiments demonstrated that the background absorption of Tm matrices is obviously wavelength dependent. The background absorption of TmCl 3 is larger than that of Tm(NO 3) 3, especially in short wavelength region. The background absorption of TmCl 3 is decreased significantly as the ashing temperature increases and that of Tm matrices is eliminated completely at about 1900 ℃. The time distribution of background signal is related to the atomization temperature and the heating mode of atomization HNO 3 can be used to reduce the background absorption of TmCl 3 matrix.

A Study of the Background Absorption of Slurry Algae in the Graphite Furnace Atomic Absorption Spectrometry

In general, biological organisms have the ability to absorb a specific element selectively. Holcombe and his co-workers reported that copper, nickel and cobalt could be separated from riverine and sea-water samples and cadmium from river water samples by unicellular green algae and were determined by slurry GFAAS. Dar-

Determination of Pb Content in Soil Samples by Graphite Furnace Atomic Absorption Spectrometry

[ Objective] A method was established to determine trace Pb in soil by graphite furnace atomic absorption spectrometry. [ Method] The pre-treatment of soil sample was conducted by nitric acid -perchloric acid -hydrochloric acid system. Palladium nitrate was added to eliminate ma- trix interference. Digestion acid, ashing and atomization temperature of the sample were selected. The operating parameters of instrument and tem- perature-rise program of graphite furnace were optimized. National standard matter was used to verify accuracy of the method. [Result] The detec- tion limit for Pb was 0.27 μg/g by graphite furnace atomic absorption spectrometry, and the recovery rate was 91.0% -96.1%. [ Conclusion The method had rapid analysis velocity, high sensitivity, less interference and easy operation. When applied to determination of trace Pb in the soil, the method obtained satisfactory results.

Investigation of Distribution for Trace Lead and Cadmium in Chinese Herbal Medicines and Their Decoctions by Graphite Furnace Atomic Absorption Spectrometry

Lead and cadmium in herbal medicines are highly toxic to living organisms even in low concentrations. An effective method is developed for analysis of trace lead and cadmium in Chinese herbal medicines and their decoctions by graphite furnace atomic absorption spectrometry (GFAAS). The effects of analytical conditions on absorbance were investigated and optimized. A water-dissolving capability for Pb and Cd was investigated, and the contents of different species in five Chinese herbal medicines and their decoctions were analyzed. The content ratios (kow) of n-octanol-soluble Pb or Cd to water-soluble Pb or Cd were evaluated, and the distribution of Pb and Cd in water decoction at stomach and intestine acidities was developed, in the first time. The contents of water-soluble Pb and Cd, n-octanol-soluble Pb and Cd, and their content ratios were related with the kind of medicine and the acidity of the decoction. The proposed method has the advantages of simple operation, high sensitivity and high speed, with 3 σ detection limits of 4.2 pg for Pb and 0.1 pg for Cd.

Measuring Conditions for the Determination of Lead in Iron-Matrix Samples Using Graphite Atomizers with/without a Platform in Graphite Furnace Atomic Absorption Spectrometry

In graphite furnace atomic absorption spectrometry (GF-AAS), the atomization process of lead occurring in graphite atomizers with/without a platform plate was investigated when palladium was added to an iron-matrix sample solution containing trace amounts of lead. Absorption profiles of a lead line were meas- ured at various compositions of iron and palladium. Variations in the gas temperature were also estimated with the progress of atomization, by using a two-line method under the assumption of a Boltzmann distribu- tion. Each addition of iron and palladium increased the lead absorbance in both the atomizers, indicating that iron or palladium became an effective matrix modifier for the determination of lead. Especially, palladium played a significant role for controlling chemical species of lead at the charring stage in the platform-type atomizer, to change several chemical species to a single species and eventually to yield a dominant peak of the lead absorbance at the atomizing stage. Furthermore, the addition of palladium delayed the peak after the gas atmosphere in the atomizer was heated to a higher temperature. These phenomena would be because the temperature of the platform at the charring stage was elevated more slowly compared to that of the furnace wall, and also because a thermally-stable compound, such as a palladium-lead solid solution, was produced by their metallurgical reaction during heating of the charring stage. A platform-type atomizer with palladium as the matrix modifier is recommended for the determination of lead in GF-AAS. The optimum condition for this was obtained in a coexistence of 1.0 × 10–2 g/dm3 palladium, when the charring at 973 K and then the atomizing at 3073 K were conducted.

Determination of Heavy Metals at Sub-ppb Levels in Water by Graphite Furnace Atomic Absorption Spectrometry Using a Direct Introduction Technique after Preconcentration with an Iminodiacetate Extraction Disk

A direct analysis method combining an iminodiacetate extraction disk (IED) with graphite furnace atomic absorption spectrometry was developed for the determination of Co, Ni, Cu, Cd, Sn, Pb, and Bi at sub-ppb levels in water. A 100 mL water sample was adjusted to pH 5.6 with nitric acid and a 1 mol?L–1 ammonium acetate solution, and then passed through an IED (diameter, 47 mm;effective filtering diameter, 35 mm) at a flow rate of 80 - 100 mL?min–1 to preconcentrate seven analytes. The IED was dried at 100?C for 20 min in an electric oven, and 110 - 145 small disks, each 2 mm in diameter, were punched out from the IED. A small disk was introduced into the graphite furnace and atomized according to a heating program. For Cd, Sn, Pb, and Bi measurements, Pd was used as a chemical modifier to enhance the absorbances. Calibration was performed using aqueous standard solutions. The detection limits, corresponding to three times the standard deviation (n = 5) of the blank values, were 0.092 μg·L–1 for Co, 0.12 μg·L–1 for Ni, 0.40 μg·L–1 for Cu, 0.077 μg·L–1 for Cd, 0.92 μg·L–1 for Sn, 0.61 μg·L–1 for Pb, and 0.80 μg·L–1 for Bi with an enrichment factor of 140 using a 100-mL water sample. A spike test for the seven analytes in tap water, rainwater, river water, and mineral drinking water showed quantitative recoveries (93% - 108%).

ICP-MS和GFAAS检测生活饮用水中镉、铬、铅的方法比较

目的:探索实验室检测生活饮用水中镉、铬、铅元素含量经济便捷的方法。方法:比较电感耦合等离子体质谱(Inductively Coupled Plasma Mass Spectrometry,ICP-MS)法和石墨炉原子吸收光谱(Graphite Furnace Atomic Absorption Spectrometry,GFAAS)法检测生活饮用水中镉、铬、铅元素含量的相关系数、方法检出限、回收率、重复性和精密度等。结果:两种方法在对应浓度范围内线性关系良好,r值均大于0.999;ICP-MS法的检出限为0.001 05~0.022 10μg·L^(-1),GFAAS法的检出限为0.067 1~1.120 0μg·L^(-1);ICP-MS法的回收率为96.5%~105.4%,GFAAS法的回收率为93.4%~100.6%;ICP-MS法的精密度为0.596%~0.922%,GFAAS法的精密度为2.52%~3.99%;两种方法的相对标准偏差均小于5%。结论:两种方法均具有检出限低、灵敏度高、分析精密度高的特点,实验室可根据需测元素、成本及效率等情况,选择合适的方法。

电感耦合等离子体质谱法(ICP-MS)和石墨炉原子吸收光谱(GFAAS)法测定大米粉中铅含量的探讨和比较

采用微波消解前处理方法,建立电感耦合等离子体质谱法(ICP-MS)和石墨炉原子吸收光谱法(GFAAS)测定大米粉中铅含量的方法,并进行比较分析。结果表明ICP-MS法和GFAAS法均能对大米粉中的铅元素进行很好的分析测定,校正曲线的相关系数均在0.999以上,线性关系良好;各方法铅元素检出限均小于国标方法要求的检出限,灵敏度较高;加标回收率范围在93.9%~103.2%之间,回收率良好;相对标准偏差RSD值均小于5.0%,精密度良好;大米粉标准物质测定值均在标示值范围内,准确度良好。

Determination of trace lead in rice of sewage irrigation by graphite furnace atomic-absorption spectrometry

The early literatures reported that a lot of matrix interference were encounted in the determination of lead content in various samples. Chlorides produced serious interference on analysis of lead content. All acids except phosphoric acid reduced sensitivity of determination of Pb. Hinderberger et al.reported that lead was determined without the interference could be removed by using NH4H2PO4 as matrix modifier in L’vov platform atomization. The combination of pyrolytic graphite tube with solid pyrolytic graphite platform and Zeeman background correction technique was used in our experiments for determination of lead content in rice samples, with 0.1% Mg(NO)and 2% NHHPOas matrix modifier.