A rapid and decisive determination of thiocyanate in blood by electrospray ionization tandem mass spectrometry

A rapid and reliable method was developed to identify and quantify the thiocyanate ion (SCN⁻) in blood. SCN⁻ was reacted with NaAuCl₄ to produce Au(SCN)₂⁻, which was extracted with octanol. The extract was injected directly into an electrospray ionization tandem mass spectrometer. Quantification of SCN⁻ was performed by selected reaction monitoring of the product ion SCN⁻ at m/z 58 that derived from the Au(SCN)₂⁻ precursor ion (m/z 313). SCN⁻ could be measured in the quantification range of 0.05–10 μM in aqueous solution with a limit of detection of 0.013 μM within 15 min. Using only 5 μl of blood, the SCN⁻ level of a victim who ingested sodium cyanide was determined to be 32.7 ± 2.1 μM, indicating a quite small increase from the control level of 15.5 ± 8.7 μM.     

Potentialities of mass spectrometry (ICP-MS) for actinides determination in urine.

The applicability of inductively coupled plasma-mass spectrometry (ICP-MS) for determining actinides in urine was investigated. Performances of ICP-MS including detection limit and analysis time were studied and compared with alpha spectrometry performances. In the field of individual monitoring of workers, the comparison chart obtained in this study can be used as a guide for medical laboratories to select the most adequate procedure to be carried out depending on the case in question (the radioisotope to be measured, the required sensitivity, and the desired response time).     

Determination of 129I in atmospheric samples by accelerator mass spectrometry.

A method for the radiochemical extraction of 129I from atmospheric charcoal filters and its measurement by accelerator mass spectrometry is presented. Either the 129I concentration or the 129I/127I atom ratio can be determined in the sample. With this method, air filters from Seville, in the Southwest of Spain (37.4 degrees N, 6 degrees W) have been analyzed. Sensitivities in the order of 10(4) atoms/m3 for 129I concentrations and 10(-10) for 129I/127I atom ratios are obtained. AMS measurements are performed with the 6 MV tandem accelerator at the ETH-H?nggerberg in Zurich.     

Sensitive determination of arsenite and arsenate in plasma by electrospray ionization tandem mass spectrometry after chelate formation

Inorganic arsenite (As³⁺) and arsenate (As⁵⁺) are well-known poisons, and the toxicity of As³⁺ is about ten times that of As⁵⁺. In this study, a simple, rapid, and sensitive method was developed for As³⁺ in plasma using electrospray ionization (ESI) tandem mass spectrometry (MS-MS). After washing plasma with trichloroethylene (TCE), As³⁺ in the aqueous layer was reacted with pyrrolidinedithiocarbamate (PDC, C₄H₈NCSS_-), and the produced As(PDC)3 was extracted with methyl isobutyl ketone (MIBK); a 1-μl aliquot of the MIBK layer containing As(PDC)₃ was introduced into the MS-MS instrument in the direct-flow injection mode. Other arsenic compounds such as As⁵⁺, monomethyl arsonic acid, dimethyl arsinic acid, arsenobetaine, arsenocholine, and tetramethyl arsonium did not produce As(PDC)₃. Therefore, without liquid chromatographic separation, As³⁺ alone could be detected after washing with TCE followed by solvent extraction of As(PDC)₃ with MIBK. Thus, inorganic As⁵⁺ was reduced to As³⁺ with thiosulfate, and then the total inorganic As was quantifi ed as As³⁺; As⁵⁺could be calculated by subtracting As³⁺from the total inorganic As. The MS-MS quantification was performed by selected reaction monitoring using a peak at m/z 114 of a product ion (C₄H₈NCS)⁺ formed by collision-induced dissociation from the precursor ion As(PDC)₂ ⁺ at m/z 367. The mass spectral identification on MS-MS spectrum was possible even at 1 ng As³⁺/ml plasma. The calibration curve for As³⁺ showed linearity from 0.5 to 100 ng/ml plasma. The limits of detection by selected reaction monitoring were 0.3 ng/ml in water and 0.2 ng/ml in plasma. The analysis could be completed in less than 15 min, because chromatographic separation was not necessary before the MS-MS detection.     

电喷雾质谱技术在手性识别中的应用

本文综述了近年来电喷雾等软电离质谱技术用于手性识别的研究进展。其研究方法主要分为对映体标记法、离子—分子反应法以及动力学方法等3类。通过综述对质谱技术用于手性识别的不足之处以及未来主要发展趋势进行了讨论。     

Use of TEVA resin for the determination of U isotopes in water samples by Q-ICP-MS.

In order to measure uranium isotopic mass ratio in natural water samples by Q-ICP-MS, an application of TEVA resin (Eichrom) was studied to separate and concentrate U. After being evaporated to dryness, the sample residue was dissolved in 6 M HCl, then, TEVA extraction was carried out. U extracted on the resin could be removed with 20 ml of 1 M HCl (U fraction) when Fe content was lower than 2 mg. U recovery in U fraction showed a negative correlation with Fe content in the samples.     

Simultaneous determination of coinage metals, copper, silver, and gold in tissues using electrospray ionization tandem mass spectrometry

A rapid and sensitive mass spectrometric method was developed for the simultaneous determination of the coinage metals of copper (Cu), silver (Ag), and gold (Au). The metals in a wet-ashed tissue solution were complexed with diethyldithiocarbamate (DDC; C₄H₁₀NCS₂) and were extracted with isoamyl alcohol. After acidification of the extract with oxalic acid, metals were quantified using their product ions, Cu(DDCH)⁺, Ag(DDCH)⁺, and Au(DDCH)⁺ that derived from the precursor ions Cu(DDC)₂ ⁺, Ag(DDC)₂ ⁺, and Au(DDC)₂ ⁺, respectively, by electrospray ionization tandem mass spectrometry. The limits of detection were 0.6, 0.3, and 1 μg/l for Cu, Ag, and Au, and the quantification ranges were 2–100, 1–100, and 3–100 μg/l for Cu, Ag, and Au, respectively. Cu levels in spontaneously hypertensive osteogenic disorder rats at 6 weeks of age and 30 weeks of age were found to be 1.8 times and 5.1 times those of the normotensive osteogenic disorder rats, respectively, when using wet-ashed kidney solutions diluted 1000-fold.     

Determination of Urine Luck in urine using electrospray ionization tandem mass spectrometry

A simple, rapid and sensitive method using tandem mass spectrometry (MS-MS) has been developed for the determination of chromate Cr⁶⁺ in urine. Cr⁶⁺ is a substantial component of Urine Luck, which is used to conceal the presence of drugs in urine. Cr⁶⁺ was complexed with diethyldithiocarbamate (DDC) and extracted with isoamyl alcohol in the presence of citric acid. Then a 1-μl aliquot of isoamyl alcohol containing Cr-DDC complex was directly injected into an MS-MS instrument without chromatographic separation. The quantification was performed using selected reaction monitoring at m/z 363.8 of product ion CrO(DDC)₂ ⁺ obtained by collision-induced dissociation from the precursor ion, CrOH(DDC)₃ ⁺ at m/z 513.1. This method was validated with the analysis urine samples obtained from volunteers. A linear calibration curve could be obtained in the range of 0.18–100 ng/ml. The limits of detection and quantification of Cr⁶⁺ were 0.05 and 0.18 ng/ml, respectively, using only 10 μl of urine. Results could be obtained in less than 10 min for a sample. After oxidation of Cr³⁺ to Cr⁶⁺, near 100% recovery was confirmed using standard reference materials such as SRM 2670a (low level and high level) and SRM 1643e. The most outstanding advantage of this ESI-MS-MS method is that it gives excellent product ion mass spectra for identification of Cr⁶⁺.     

Overcoming ICP-QMS instrumental limitations for (99)Tc determination in environmental solid samples using radiochemistry.

Besides its capabilities, quadrupole-based ICP-MS counting establishes several limitations on (99)Tc analysis in environmental samples. Overcoming these limitations requires the use of radiochemical methods. We have developed a new method for the detection of (99)Tc by ICP-QMS in solid environmental samples. In order to improve the limit of detection of the technique, high amounts of solid samples (> or = 100g) are used. Hence, great amounts of the interfering elements are involved in the process, and therefore special emphasis is put on achieving a good commitment between adequate matrix elements removal and a minimization of the limit of detection. The performances of the method are analyzed in terms of conveniently defined figures of merit. The developed method is applied to several fallout level samples. In this way, the real performances and especially the real limitations of this method are shown.     

Corrections for self-attenuation in gamma-ray spectrometry of bulk samples.

On the basis of the measurement of over 70 radioactive standard bulk sources with different matrix density and different shapes, the gamma-ray self-attenuation corrections needed in activity determination by means of gamma-ray spectrometry are evaluated. The full-energy peak efficiency dependence on the density, and the self-attenuation correction dependence on the photon energy are described.     

Determination of technetium-99 in environmental samples by inductively coupled plasma mass spectrometry

A new analytical technique using inductively coupled plasma mass spectrometry (ICP-MS) was applied to the determination of ⁹⁹Tc in some environmental samples. The accuracy and precision of the new method were assessed by comparison with those of the liquid scintillation counting method. The results obtained by ICP-MS were in good agreement with those by liquid scintillation counting at a relative deviation of 3%. The detection limit is 1.1 mBq/mL (1.73 pg/mL).     

Peak resolution and tailing in alpha-particle spectrometry for environmental samples.

Peak resolution in alpha-particle spectrometry is generally quoted as full-width-at half maximum. However, the extent of tailing of alpha particle peaks into regions of lower energy is often a critical factor for accurate spectral analysis, particularly given the relatively low count rates observed for many environmental samples. In this paper we examine the influence of various factors on peak resolution and tailing for spectra collected using solid-state alpha detectors, in particular chamber gas pressure and source deposit thickness.     

Improved determination of plutonium content and isotopic ratios in low activity samples by alpha-particle and underground L X-ray measurement.

The determination of the isotopic ratio of 239Pu and 240Pu by alpha-particle spectrometry is limited due to the small differences in the alpha-particle energies. But taking into account the differences in the L X-ray emission probabilities of the two plutonium isotopes, an additional L X-ray measurement allows the isotopic ratio of 239Pu and 240Pu to be determined. The sensitivity of this method can be improved, as described in this work, by performing the L X-ray measurement in an underground laboratory.     

Bioanalytical method for simultaneous determination of benzodiazepines in vitreous humor using liquid chromatography-tandem mass spectrometry

The use of vitreous humor (VH) in forensic casework has been growing in the last years due to numerous advantages. Several compounds can be evaluated in this matrix, including benzodiazepines whose determination is essential due to their great availability and potential of dependance and misuse. Postmortem toxicological analyses are required to determine the influence of benzodiazepines in deaths. However, most of the analytical methods which determine these drugs in VH are laborious and time consuming. This article describes a simple method based on protein precipitation for the determination of eight benzodiazepines in VH samples. Samples were prepared through a protein precipitation method and analyzed by liquid chromatography tandem mass spectrometry. Solvent choice and sample and solvent volumes for precipitation were optimized using chemometric approaches. The method was validated for selectivity, lower limit of quantification (LLOQ), linearity, carryover, precision, bias, matrix effect and dilution integrity. In order to verify the applicability, 62 vitreous humor samples were analyzed. LLOQs were 1 ng/mL and calibration curves were linear from 1 to 25 ng/mL (r2 > 0,99) for all analytes. Bias, precision and dilution integrity results were satisfactory according to proper guidelines. Ionization suppression was significant with values ranging from 8 to 37%. Two samples from real cases were positive for diazepam with the following concentrations: 6.80 ng/mL and 47.68 ng/mL, approximately 10 times lower than those found in peripheral blood. The procedure described here can be used as a straightforward and low cost method for the quantitation of multiple benzodiazepines in VH.     

LC-MS法检测大鼠血浆中酒石酸美托洛尔的方法学研究

目的：建立准确、灵敏、可靠的LC-MS法检测大鼠血浆中酒石酸美托洛尔的浓度。方法：血浆样品用乙酸乙酯液-液萃取,内标选用盐酸普萘洛尔,液相色谱柱为ThermoODS-C18（5.0μm,100mm×2.1mm）,流动相为含0.1%甲酸的乙腈：甲醇：水（20：20：60,体积比）,流速为0.2ml/min;仪器选用Agilent公司1100LC/MSDSL型液相色谱-质谱联用仪,采用电喷雾离子化电离源（ESI）,选择性离子监测（SIM）方式进行正离子检测,用于定量分析的离子反应分别为m/z267→268（美托洛尔）和m/z259→260（普萘洛尔）。结果：在本实验条件下,美托洛尔与内标盐酸普萘洛尔分离良好,保留时间分别为1.79和4.01min,0.1～50ng/ml范围内线性关系良好（r2=0.99411）,提取回收率均大于80%,日内日间精密度均小于15%（n=5）。结论：该方法快速、准确、灵敏度高,专属性好,可用于酒石酸美托洛尔在大鼠体内药物代谢动力学的研究。     

Accelerator mass spectrometry measurement of 240Pu/239Pu isotope ratios in Novaya Zemlya and Kara Sea sediments.

Generally low levels of plutonium in environmental samples, often combined with limited sample sizes, necessitate reliable low-level techniques for determination of Pu isotopes. Accelerator mass spectrometry (AMS) has proved to be a powerful method for measuring low-level Pu activity concentrations and Pu isotope ratios. Based on procedural blanks, detection limits for AMS were below 1 fg Pu (equivalent to ca. 2 microBq 139Pu), which can compete with both TIMS, high sensitivity ICP-MS, and certainly alpha-spectrometry, while showing less interference, memory and matrix effects as compared to routine ICP-MS techniques. In addition to low detection limits, the technique offers the advantage of giving information on Pu isotope ratios. Measurements of sediments collected from dumping sites at Novaya Zemlya showed deviation from global fallout 240Pu/239Pu ratios.     

Calcium isolation from large-volume human urine samples for 41Ca analysis by accelerator mass spectrometry

Calcium oxalate precipitation is the first step in preparation of biological samples for ⁴¹Ca analysis by accelerator mass spectrometry. A simplified protocol for large-volume human urine samples was characterized, with statistically significant increases in ion current and decreases in interference. This large-volume assay minimizes cost and effort and maximizes time after ⁴¹Ca administration during which human samples, collected over a lifetime, provide ⁴¹Ca:Ca ratios that are significantly above background.     

Automated analysis of sequence polymorphism in STR alleles by PCR and direct electrospray ionization mass spectrometry

Short tandem repeats (STRs) are the primary genetic markers used for the analysis of biological samples in forensic and human identity testing. The discrimination power of a combination of STRs is sufficient in many human identity testing comparisons unless the evidence is substantially compromised and/or there are insufficient relatives or a potential mutation may have arisen in kinship analyses. An automated STR assay system that is based on electrospray ionization mass spectrometry (ESI-MS) has been developed that can increase the discrimination power of some of the CODIS core STR loci and thus provide more information in typical and challenged samples and cases. Data from the ESI-MS STR system is fully backwards compatible with existing STR typing results generated by capillary electrophoresis. In contrast, however, the ESI-MS analytical system also reveals nucleotide polymorphisms residing within the STR alleles. The presence of these polymorphisms expands the number of alleles at a locus. Population studies were performed on the 13 core CODIS STR loci from African Americans, Caucasians and Hispanics capturing both the length of the allele, as well as nucleotide variations contained within repeat motifs or flanking regions. Such additional polymorphisms were identified in 11 of the 13 loci examined whereby several nominal length alleles were subdivided. A substantial increase in heterozygosity was observed, with close to or greater than 5% of samples analyzed being heterozygous with equal-length alleles in at least one of five of the core CODIS loci. This additional polymorphism increases discrimination power significantly, whereby the seven most polymorphic STR loci have a discrimination power equivalent to the 10 most discriminating of the CODIS core loci. An analysis of substructure among the three population groups revealed a higher θ than would be observed compared with using alleles designated by nominal length, i.e., repeats solely. Two loci, D3S1358 and vWA produced θ estimates of 0.0477 and 0.0234, respectively, when the expanded allele complement (i.e., nominal allele and SNPs) was considered compared to 0.0145 and 0.01266, respectively when only nominal repeat number was considered. These differences may indicate underlying population specific allele distributions exist within these populations. A system of nomenclature has been developed that facilitates the databasing, searching and analyses of these combined data forms.