Streamlined sample preparation procedure for determination of perchlorate anion in foods by ion chromatography-tandem mass spectrometry

A rapid, sensitive, and specific method was developed for the determination of perchlorate anion in foods. The foods included high moisture fruits and vegetables, low moisture foods (e.g. wheat flour and corn meal), and infant foods. Improvements to existing procedures were made in sample preparation that reduced sample test portion size from 100 to 5 or 10 g, extraction solvent volume from 150 to 20-40 ml, and replaced blending extraction-vacuum filtration and their associated large glassware with a simple shakeout-centrifugation in a small conical tube. Procedures common to all matrices involved: extraction, centrifugation, graphitized carbon solid phase extraction (SPE) cleanup, and ion chromatography-tandem mass spectrometry (IC-MS/MS) analysis. A Waters IC-Pak Anion HR column (4.6 mm × 75 mm) was eluted with 100 mM ammonium acetate in 50:50 (v/v) acetonitrile/water mobile phase at a rate of 0.35 ml/min. A triple stage quadrupole mass spectrometer, equipped with electrospray ionization (ESI) in the negative ion mode, was used to detect perchlorate anion. An ¹⁸O₄-labeled perchlorate anion internal standard was used to correct for any matrix effects. The method limit of quantitation (LOQ) was: 1.0 μg/kg in fruits, vegetables, and infant foods; 3.0 μg/kg in dry products. Fortified test portions gave 80-120% recoveries. Determination of incurred perchlorate anion residues agreed well with results for comparable commodities or products analyzed by published methods.     

Stability of low levels of perchlorate in drinking water and natural water samples

Perchlorate ion (ClO₄⁻) is an environmental contaminant of growing concern due to its potential human health effects, impact on aquatic and land animals, and widespread occurrence throughout the United States. The determination of perchlorate cannot normally be carried out in the field. As such, water samples for perchlorate analysis are often shipped to a central laboratory, where they may be stored for a significant period before analysis. The stability of perchlorate ion in various types of commonly encountered water samples has not been generally examined—the effect of such storage is thus not known. In the present study, the long-term stability of perchlorate ion in deionized water, tap water, ground water, and surface water was examined. Sample sets containing approximately 1000, 100, 1.0, and 0.5 μg l⁻¹ perchlorate ion in deionized water and also in local tap water were formulated. These samples were analyzed by ion chromatography for perchlorate ion concentration against freshly prepared standards every 24 h for the first 7 days, biweekly for the next 4 weeks, and periodically after that for a total of 400 or 610 days for the two lowest concentrations and a total of 428 or 638 days for the high concentrations. Ground and surface water samples containing perchlorate were collected, held and analyzed for perchlorate concentration periodically over at least 360 days. All samples except for the surface water samples were found to be stable for the duration of the study, allowing for holding times of at least 300 days for ground water samples and at least 90 days for surface water samples.     

Matrix diversion methods for improved analysis of perchlorate by suppressed ion chromatography and conductivity detection

Two inline matrix diversion methods were developed for the sensitive analysis of perchlorate in a matrix comprising up to 1000 mg l⁻¹ of chloride, sulfate and bicarbonate ions using suppressed ion chromatography and conductivity detection. The first method used a cryptand C1 concentrator column, which exhibited a high selectivity for perchlorate ion over the other matrix anions. After retaining the sample anions in a concentrator column derivatized with a crytpand phase, a rinse step was implemented with a weak base to divert the matrix ions to waste while selectively retaining perchlorate in the concentrator column for subsequent analysis. The analysis was done using a 2 mm IonPac^® AS16 or 2 mm IonPac^® AS20 separator column. The second method was a two-dimensional matrix diversion method with a focus on improving the detection sensitivity. The first dimension was used to achieve some resolution of the matrix ions from perchlorate. The perchlorate ion was then diverted into a concentrator column for subsequent analysis in the second dimension. By pursuing analysis using a 4 mm IonPac^® AS16 or IonPac^® AS20 column in the first dimension and subsequently pursuing analysis using a 2 mm IonPac^® AS16 or IonPac^® AS20 column format, excellent sensitivities were achieved when the first and second dimensions were operated at the same linear flow velocity (cm min⁻¹). While sensitive detection of perchlorate in the low μg l⁻¹ regime was achieved by the above methods in the presence of matrix ions, superior recovery for perchlorate was demonstrated under a variety of matrix concentrations by the second method.     

高氯酸盐与十六烷基三甲基溴化铵作用的光散射

利用光散射光谱法研究了高氯酸根和阳离子表面活性剂十六烷基三甲基溴化铵(CTAB)的作用。 在酸性条件下,高氯酸根和CTAB通过静电作用形成离子缔合物,导致体系光散射强度增强。 环境水样中的常见阴离子如Cl^-、Br^-、ClO₃^-、NO₃^-和PO₄^3-等与CTAB单独作用时其光散射强度很弱,而当它们与高氯酸根同时存在时,由于协同作用使体系散射强度发生改变。 以Cl^-为例,借助动态光散射测定,初步探讨了体系协同作用的机理。     

RE(Ala)4(Im)(ClO4)3*2H2O固体配合物的合成及其红外光谱研究

本文通过稀土高氯酸盐与L-丙氨酸(L-Ala)及咪唑(Im)反应,合成了标题配合物RE(Ala)_4(Im)(ClO_4)_3·2H_2O(RE=Pr,Nd,Sm),测定了配合物的红外光谱,对其主要吸收带进行了归属。红外光谱的研究结果表明,丙氨酸以内盐的形式存在于配合物中,通过羧基与稀土离子配位,且随着RE原子量的增大,羧基与RE~(3 )间配位键离子性逐渐减弱,共价性逐渐增大;咪唑环上的N参与了配位。     

35Cl NMR研究溶液中离子对和离子缔合

测量了Sr和Ba高氯酸盐在乙腈和乙醇中0.5 mol·L~(-1)溶液的~(35)Cl NMR峰宽Δv和粘度η。按核四极矩弛豫机理, 结合文献中Mg~[1]和Ca~[2]盐的数据, 一种溶剂中各盐的Δv/η之比当反映~(35)Cl核处的电场梯度平方之比。按接触型离子对假设, ~(35)Cl处电场梯度平方之比应等于(r_++r_-)~(-6)。测得各盐的Δv/η之比与计算的(r_++r_-)~(-6)吻合, 论证了在乙腈与乙醇中为接触型离子对。同时文中报告了Δv/η和盐的摩尔电导随水或DMF加入的变化。     

Preconcentration/preelution ion chromatography for the determination of perchlorate in complex samples

The determination of perchlorate in complex matrices by ion chromatography (IC) with an online preconcentration and preelution technique is discussed. The method was applied to different sample types containing large concentrations of matrix anions that would otherwise interfere with analysis via conventional IC. The present approach was highly effective in removing most of the matrix anions and was thus resistant to the interferences commonly encountered in a high ionic strength background. Method performance was evaluated by analyzing for low-level perchlorate in synthetic high ionic strength solutions, tissue extracts, and hydroponic nitrate fertilizer samples. Not only is it easier to practice the present method compared to USEPA Method 314.0, but for most of these samples the present approach provided equal to or better recovery of perchlorate than Method 314.0. With a sample of specific conductance 12,650 μS cm⁻¹, for example, the present method provided a perchlorate recovery of 101% at the 25 μg L⁻¹ level versus 89% by EPA Method 314.0. Method detection limits of perchlorate in hydroponic fertilizer samples with this method (130-190 μg kg⁻¹) are the lowest thus far reported.     

Ln（ClO_4）_3－DAPTU－H_2O三元体系30℃时的相平衡研究

测定了Ｌｎ（ＣｌＯ_４）_３－ＤＡＰＴＵ－Ｈ_２Ｏ（Ｌｎ＝Ｌａ，Ｓｍ，Ｙｂ）三元体系在３０℃时的溶解度及饱和溶液的折光率，绘制了相应的溶度图和折光率－组成图，各体系的溶度曲线和折光率曲线均由三支组成，分别与ＤＡＰＴＵ、Ｌｎ（ＤＡＰＴＵ）_２（ＣｌＯ_４）_３·８Ｈ_２Ｏ（Ｌｎ＝Ｌａ，Ｓｍ，Ｙｂ）和Ｌｎ（ＣｌＯ_４）_３·ｎＨ_２Ｏ（Ｌｎ＝Ｌａ，ｎ＝８；Ｓｍ，ｎ＝９；Ｙｂ，ｎ＝８）相对应。从溶度图上发现了３个未见文献报道的固液异组成溶解的化合物，通过化学分析及元素分析、ＴＧ－ＤＴＧ、ＩＲ对其进行了表征。     

Lithium Perchlorate Diethyl Ether Solution: A Highly Efficient Media for the Abramov Reaction

The f -hydroxy phosphonates are readily prepared by treating aromatic or aliphatic aldehydes and ketones with trialkylphosphite in the presence of trimethylsilylchloride in a very short time and in almost quantitative yields.