甲基红褪色光度法测定食盐中碘的研究

在酸性介质中,溴化钾存在下,碘酸根对甲基红有褪色作用,且褪色的程度与碘酸根的量有关,从而建立了碘的光度测定新方法。方法的最大吸收在520nm处,碘定量测定的线性范围为0～16μg/10mL,检出限为1.47×10-8g/mL。方法操作简单、快速、重现性好,用于加碘食盐中碘的测定,结果满意。     

氧化邻苯三酚红褪色光度法测定食盐中碘

１引言 碘是人体必需营养元素之一,成年人缺碘会导致甲状腺机能亢进,患大脖大病,小孩缺碘会导致甲状腺发育不良,生长发育迟缓,智力低下,甚至于痴呆。食盐中加碘是防止碘缺乏病最主要、最经济、最简单的方法。测定微量碘最常用的方法是重铬酸钾法,也有用催化光度法、离子色谱法、离子选择性电极法等。基于国家有关规定,碘盐中所加人的碘必须以碘酸钾形式,本文利用在酸性介质中,碘酸根能氧化邻苯三酚红使之褪色,且褪色的程度与碘酸根的存在量有关,从而建立了光度法测定碘的新方法。实验表明,在０．３６～０．９６ ’ｍｏｌ／ＬＨ…     

溴邻苯三酚红褪色光度法测定食盐中碘的研究

在硫酸介质中,碘酸根能氧化溴邻苯三酚红使之褪色,且褪色的程度与碘酸根的存在量有关,从而建立了光度法测定碘的方法。有色溶液的最大吸收波长为510nm,碘的存在量在0～30μg/25ml范围内符合比耳定律,表观摩尔吸光系数ε=1.81×104L·mol-1·cm-1。方法简便、快速、选择性好,准确度高,用于测定食盐中微量碘时,结果满意。     

甲基橙氧化褪色吸光光度法测定碘的研究

提出了在硫酸介质中并在溴化钾的催化下,碘酸根氧化甲基橙褪色吸光光度法测定碘的新方法.试验结果表明,在最大吸收波长510nm处,碘浓度在0～50μg/50ml范围内呈线性关系,表观摩尔吸光系数为9.0×10~(4).方法已用于测定碘盐及海带中的碘,结果满意.     

酸性络蓝K褪色光度法测定食盐中微量碘

在硫酸介质中 ,碘酸根对酸性络蓝 K具有褪色作用 ,且褪色的程度与碘酸根存在量有关 ,从而建立了光度法测定碘的新方法。方法最大吸收波长为 52 4 nm,表观摩尔吸光系数为 2 .1 9×1 0 4 L·mol-1·cm-1,碘的浓度在 0～ 60 μg/2 5ml范围内符合比耳定律。方法简单、快速、准确、选择性好、灵敏度高 ,用于测定碘食盐中的碘含量 ,结果满意     

酸性红褪色分光光度法测定食盐中碘的含量

研究了在H_2SO_4-KBr的介质中,碘酸钾能够氧化酸性红并使之褪色,且褪色的程度与碘酸根的含量在一定范围内有很好的线性关系,从而建立了一种新的测定碘的方法。实验结果表明,酸性红的最大吸收波长为510nm,碘的含量在0～50μg/50mL范围内,符合比耳定律,其回归方程为△A=0.004 13C+0.032 14,相关系数R2=0.998 3,检出限为0.78μg/50mL。方法操作简单,快速准确,用于食盐中碘含量的测定,结果令人满意。     

溴酸钾氧化甲基红褪色催化光度法测定微量铁

铁广泛存在于自然界,它不仅是广泛应用的金属材料元素,更重要的它是人体必需的微量元素、食品的重要组成元素,与人类生命活动密切相关。因此,微量铁的测定方法研究一直被受关注。测定铁的常用方法有分光光度法和原子吸收光谱法,但普通分光光度法灵敏度低。催化动力学光度法具有灵敏度高、仪器廉价、操作简便、分析成本低、便于推广等优点。     

二甲酚橙褪色光度法测定微量碘的研究

研究了在硫酸介质中,溴化钾催化下,碘酸根氧化二甲酚橙褪色的最佳条件。其最大吸收波长λmax为430nm,表观摩尔吸光系数为1．3×104L·mol-1·cm-1,碘浓度在0-30μg／25ml范围内呈线性关系。方法用于测定加碘食盐中碘,回收率可达98．0％-101．3％,结果满意。     

中性红氧化褪色光度法测定海带中的微量碘

讨论了用H2SO4-KBr-IO3--中性红氧化褪色光度法测定海带中微量碘的方法。在酸性介质中,以KBr作为催化剂,碘酸根对中性红有褪色作用,且褪色的程度与碘酸根的量有关,碘定量测定的线性范围为0~25μg/mL,表观摩尔吸收系数ε=1.79×104L.mol-1.cm-1。回收率97.1%~101.7%。该法是测定海带中微量碘的一种较理想的方法。     

二甲基黄褪色光度法测定微量碘

在硫酸介质中,溴化钾催化下,碘酸根对二甲基黄有褪色作用,且褪色的程度与碘酸根的量有关,从而建立了光度法测定碘的新方法。方法的最大吸收波长为515nm,表观摩尔吸光系数为3.1×104L·mol-1·cm-1,碘浓度在0～20μg/10ml范围内符合比耳定律,检出限为1.02×10-8g·ml-1。方法简单、快速、选择性好、灵敏度高,用于测定碘盐中碘的含量,结果满意。     

柯衣定褪色光度法测定食盐中碘

建立了加碘盐中碘含量测定新的光度分析法, 借助于在H2SO4介质中碘酸根氧化柯衣定使其褪色, 褪色前后的吸光度之差ΔA与碘含量成正比进行测量的. 柯衣定在波长455 nm处有强吸收, 碘含量在0～50 μg/mL范围内呈线性关系, 方法的相对标准偏差小于0.84%, 回收率为101.7%～105.7%.     

Reverse flow injection spectrophotometric determination of iodate and iodide in table salt

A very simple and sensitive reverse flow injection method is described for the determination of iodate and iodide. The iodate reacts with excess iodide in acidic medium to form tri-iodide, which can be spectrophotometrically monitored at 351 nm, and the absorbance is directly related to the concentration of iodate in the sample. The determination of iodide is based on oxidizing iodide to iodate. The calibration curve is linear in the range of 0.02-3.0 μg ml⁻¹ I with r²=0.9998, and the limit of detection is 0.008 μg ml⁻¹ I. The chemical and flow injection variables were studied and optimized to make the procedure suitable for quantitating iodate and iodide in table salts. It is shown that the reverse flow injection analysis could greatly improve the sensitivity and precision for determination of iodate with a relative standard deviation of 0.9%. A complete analysis, including sampling and washing, could be performed in 35 s. The procedure was applied successfully to the determination of iodate and iodide in table salts, and the results were statistically compared with results determined by standard iodometry method.     

Microwave-assisted alkaline digestion combined with microwave-assisted distillation for the determination of iodide and total iodine in edible seaweed by catalytic spectrophotometry

Microwave energy has been novelty applied to speed up a tetramethylammonium hydroxide (TMAH) alkaline digestion of seaweed samples and to assist distillation of iodine from seaweed alkaline digests. Iodide in the alkaline digests from seaweed and distilled iodine, reduced back to iodine in a hydroxylamine hydrochloride solution, was determined by a catalytic spectrophotometric method based on the catalytic effect of iodide on the oxidation of As(III) by Ce(IV) in H₂SO₄/HCl medium (Sandell-Kolthoff reaction). The determination of iodide was directly performed in the alkaline digests, while total iodine was assessed by analyzing the hydroxylamine hydrochloride solution after the distillation process. Microwave-assisted alkaline digestion was performed using 7.5 mL of TMAH and irradiating samples at 670 W for two 5.5 min steps. Microwave-assisted distillation was carried out using 4.0 mL of the alkaline digest and 3 mL of a 2.2 M hydrochloric acid and 0.05% (m/v) sodium nitrite solution, with a microwave power at 670 W for two 90 s steps. The distillate (iodine vapor) was bubbled in 10 mL of a 500 μg mL⁻¹ hydroxylamine hydrochloride solution (accepting solution). The linear calibration ranges were 0.30-20.0 and 0.40-20.0 μg L⁻¹ for iodide determination and total iodine determination, respectively. The limit of detection was 9.2 μg g⁻¹ for iodide and 28.5 μg g⁻¹ for total iodine. Repeatability of the overall procedures, expressed as R.S.D. for 11 determinations, was 2.6% for 196.3 μg g⁻¹ of iodide measured after microwave-assisted alkaline digestion, and 5.8% for 954.3 μg g⁻¹ of total iodine by microwave-assisted alkaline digestion followed by microwave-assisted distillation. Finally, accuracy of the methods was assessed by analyzing the NIST-09 (Sargasso) certified reference material and the methods were applied to the determination of iodide and total iodine in different Atlantic edible seaweed samples with satisfactory results.     

催化光度法测定蔬菜中微量碘的研究

在H3PO4介质中,碘对高碘酸钠氧化丁基罗丹明B的反应有显著的催化作用,据此建立了测定微量碘的催化动力学光度法.方法灵敏、简便、选择性好.测定Ⅰ-的检出限为17.7 ng/mL, 线性范围为0.02～2.00 μg/mL,已用于蔬菜中碘的测定.     

靛蓝胭脂红-溴酸钾体系催化光度法测定微量碘

研究了在室温及0．4mol/L H2SO4介质中碘离子对KBrO3氧化靛蓝胭脂红褪色反应的催化作用,建立了一种测定微量碘的新方法。碘离子浓度在0．20－2．0μg/mL范围内与△A呈线性关系,检测限为0．14μg/mL。多数常见离子无干扰。可用于海带中微量碘的测定。     

Preconcentration of iodide from saline water samples and determination by the catalytic method

A method is described for the determination of nanogram levels of iodide in saline water samples. The interfering chloride, present in milligram levels, is eluted out of a column of a strong anion exchanger, retaining the iodide quantitatively. The iodide is then recovered from the column with 2 M ammonium nitrate solution. The determination is carried out by the catalytic method based on the reduction of Ce(IV) by As(III) in presence of iodide. The arresting method was found to be more sensitive. The method can be easily adapted in a field laboratory, with accuracy comparable with neutron activation analysis.     

Unique reactivity of a 1,4-dilithiobutadiene with methyl iodide

Reactions of 1,4-dilithiobutadiene 5 with MeI in THF gave predominantly methyl iododiene 6. Monolithio monoiodo intermediate 8 was shown not to be involved in the formation of 6, but the results were consistent with the involvement of monolithio monomethyl intermediate 11, which could lead to 6 by metal-halogen exchange. Several other lithioalkenes also reacted with MeI to give alkenyl iodides.     

An optical redox chemical sensor for determination of iodide

A novel optical sensor based on a redox reaction for the determination of iodide has been developed. The optode membrane is constructed by immobilization of methyltrioctylammonium chloride on triacetylcellulose polymer. The exchange of chloride as counter ion with iodate in the membrane changes the color to yellow, when it is placed in acidic solution of iodide. The sensor can readily be regenerated by 0.1 mol L⁻¹ NaOH in less than 15 s. The optode has a linear range of 3.94 × 10⁻⁶ to 5.51 × 10⁻⁵ mol L⁻¹ of iodide ions with a limit of detection 7.44 × 10⁻⁷ mol L⁻¹. The relative standard deviation for eight replicate measurements of 3.94 × 10⁻⁶ and 1.57 × 10⁻⁵ mol L⁻¹ of iodide was 2.83 and 1.38%, respectively. The sensor was successfully applied to the determination of iodide in tablet, powdered milk and urine samples.     

顺序注射停流分光光度法测定痕量碘

食物中碘的含量一直是人们关注的问题,研究食物中微量碘的分析方法具有重要的现实意义.目前测定碘的方法主要有色谱法[1,2]、荧光法[3,4]、分光光度法[5,6]等.     

Spectrophotometric determination of carbon tetrachloride via ultrasonic oxidation of iodide accelerated by dissolved carbon tetrachloride

Ultrasonic oxidation of iodide was investigated in the presence of carbon tetrachloride (CCl₄). The ultrasonic oxidation of potassium iodide led to formation of iodine and then I₃⁻ in the presence of excess iodide, and the generated I₃⁻ shows strong UV absorption with a molar absorptivity of 2.31 × 10⁴ L mol⁻¹ cm⁻¹ at the maximum absorption wavelength of 351 nm. The ultrasonic oxidation of iodide was found to be significantly promoted by a small addition of CCl₄, and it was further found that the generation rate was increased with the amount of CCl₄ added. This can be used to analyze the level of CCl₄ dissolved in aqueous solutions. Under optimum conditions, the concentration of generated iodine (or its absorption at 351 nm) was found to correlated linearly with the concentration of CCl₄ in the range of 0.2-50 mg L⁻¹ (detection limit = 0.09 mg L⁻¹, R² = 0.999). As an alternative indirect spectrophotometric method of CCl₄ determination, the proposed method was successfully applied to determine the concentrations of CCl₄ in several practical samples, showing merits of being sensitive and simple of operation.