Uracil in human DNA from subjects with normal and impaired folate status as determined by high-performance liquid chromatography-tandem mass spectrometry.

A sensitive and selective method for determination of the uracil content in human DNA was first developed on the basis of high-performance liquid chromatography-tandem mass spectrometry. Uracil was excised from DNA using uracil DNA glycosylase. The released uracil was derivatized with 4-bromomethyl-7-methoxycoumarin, thereby forming bis-N,N'-(4-methylene-7-methoxycoumaryl)-uracil (uracil-MMC). 15N2-Uracil was used as an internal standard. The analytes were separated on an Adsorbsphere XL ODS column. A SCIEX API III tandem mass spectrometer equipped with a turbo ion-spray interface was used as the detector. Multiple reaction monitoring using the parent --> product ion combinations of m/z 489 --> 232 and 491 --> 233 were used to detect uracil-MMC and the internal standard, respectively. The detection limit for this assay is <1.0 x 10(-10) mol/L uracil, and the linearity is from 1.0 x 10(-10) to 2.5 x 10(-6) mol/L. The method was used for determination of uracil in human DNA. Our data show that the uracil levels in human DNA isolated from peripheral white blood cells did not differ between subjects with folate deficiency and subjects with normal red cell folate levels.     

Automated two-column ion exchange system for determination of the speciation of trace metals in natural waters

A rapid method for determination of metal speciation based on an automated two-column ion exchange system is described. Two fractions of dissolved trace metal species are directly determined by on-line flame atomic absorption spectrophotometry after preconcentration by sequential columns of Chelex-100 chelating resin and AG MP-1 macroporous anion resin. A third fraction is determined by standard addition. Variables that affect the results obtained by the two-column system are studied by the use of model complexing agents. With a 10-mL sample loop, the sample throughput is 6 samples per hour and detection limits are 0.1 micrograms/L for Cu(II), 0.08 micrograms/L for Cd(II), and 0.2 micrograms/L for Zn(II). The method is used to determine the speciation of Cu(II), Cd(II), and Zn(II) in natural water samples.     

A method for screening total mercury in water using a flow injection system with piezoelectric detection

An automatic microgravimetric screening system based on piezoelectric detection and the use of acidic stannous chloride as reductant was developed for the fast detection and determination of total mercury in water. Reduced mercury is detected as an amalgam by using a gold-coated piezoelectric crystal, the sensor subsequently being regenerated by passing it through a peroxydisulfate solution. The gold-coated piezoelectric crystal is a highly efficient retention unit for the main soluble mercury species (inorganic, complexed, and organometallic) previously reduced to elemental mercury and is free of interferences from other metal ions. This detector exhibits good sensitivity: it allows the determination of mercury at sub-parts-per-billion concentration levels (0.30-1.00 microg/L). The precision, expressed as relative standard deviation, was +/- 2.7% (n = 11; P = 0.05) at 0.5 microg/L total mercury. The proposed method was successfully used as a rapid screening method for mercury monitoring in natural waters.     

Determination of chromium in urine by stable isotope dilution gas chromatography/mass spectrometry using lithium bis(trifluoroethyl)dithiocarbamate as a chelating agent

An isotope dilution gas chromatography/mass spectrometry method using lithium bis(trifluoroethyl)dithiocarbamate as a chelating agent is described for the determination of chromium in urine. A wet digestion procedure with HNO3-H2O2 is used for oxidizing the organic matter associated with urine samples. The isotope ratios are measured by selected ion monitoring in a general-purpose mass spectrometer using a 10-m fused silica capillary column. Memory effect, in sequential analyses of samples with different isotope ratios, was evaluated by preparing a series of synthetic mixtures and was found to be negligible. The accuracy of the method was verified by quantitation of chromium in the NIST freeze-dried urine reference material, SRM-2670, with a recommended chromium concentration of 13 micrograms/L in the normal level and certified chromium concentration of 85 +/- 6 micrograms/L in the elevated level.     

Determination of tin in human blood serum by radiochemical neutron activation analysis

A method was developed for the determination of tin in human serum by radiochemical neutron activation analysis, using the long-lived radioisotope Sn(T1/2 = 115.09 days). This radioisotope decays to a daughter isotope 113mIn, the most suitable nuclide for counting (T1/2 = 1.658 h, gamma-ray of 391.7 keV). Experience showed that, with the exception of the serum samples with the lowest tin levels, in the experimental conditions of the present study tin could mostly also be determined by using its radioisotope 117mSn(T1/2 = 13.61 days, gamma-ray of 158.5 keV). Samples were collected and prepared by using the procedure elaborated by the authors, which proved its effectiveness in preventing significant sample contamination on several occasions. Because samples had to be irradiated at 10(14) n.cm-2.s-1, dry ashing was necessary. After irradiation, tin was separated by solvent extraction of tin(IV) iodide from a sulfuric acid-ammonium iodide solution with toluene. The dry ashing and solvent extraction steps were exhaustively tested by means of radioactive tracer experiments whereas the accuracy and precision of the analytical method were thoroughly checked by analyzing biological reference materials (Bowen's kale powder, the NBS' bovine liver, the NBS' nonfat milk powder, and the "second-generation" biological reference material--freeze-dried human serum--for trace element determinations, developed by the authors).(ABSTRACT TRUNCATED AT 250 WORDS)     

Preconcentration and preseparation procedure for platinum determination at trace levels by neutron activation analysis

A procedure that simultaneously allows both preconcentration and preseparation of platinum for its determination by neutron activation analysis at trace levels (<0.1 microg x g(-1)) in environmental related matrixes is developed. The method is mainly based on a two-step chemical procedure: (i) a preirradiation concentration/separation based on a column chromatography separation where the platinum is previously retained and subsequently separated from Au, Ca, Na, Br, and P; (ii) a postirradiation separation/purification of the 199Au at 158.4 keV used for the platinum determination via [198Pt (n,gamma)-->199Pt (beta-)-->199Au]. The method eliminates the following radionuclides with the gamma lines in the region of 158 keV: 47Sc (daughter of Ca) at 159.3 keV; 199Au (produced by double neutron capture onto the natural 197Au) at 158.4 keV; 123m Te at 158.8 keV. In addition, the background activity deriving from 24Na, 32p, and 82Br is drastically reduced. The method was tested by the analysis of certified rock material and then applied for platinum determination in airborne particulate matter.     

Determination of macroconcentrations of platinum by combined application of gravimetry and inductively coupled plasma—Atomic emission spectrometry

A combined method for macroconcentrations of platinum determination in chloroplatinic acid and industrial concentrate obtained during processing of some types of electronic engineering scrap that is based on a combination of gravimetric precipitation of platinum by ammonium chloride with subsequent determination of a residual concentration of platinum in a filtrate using the ISP-AES method is developed. The errors at each stage of analysis, as well as the total error, are estimated. It is shown that the accuracy of macro-concentrations of platinum determination using the combined method is not inferior to the accuracy of classical gravimetric analysis (the relative standard deviation does not exceed 0.15% for 15–40% wt concentrations of platinum). The combined method of analysis based on a combination of gravimetry and ISP-AES makes it possible to decrease labor expenditures and the time of analysis as compared to the classical one.     

Nitroprusside and methylene blue methods for silicone membrane differentiated flow injection determination of sulfide in water and wastewater.

Hydrogen sulfide evolved from an acidified sample is pre-concentrated by permeation in a stationary alkaline acceptor solution enclosed in a silicone rubber sample loop. Depending on the sample volume pre-concentrated, the applicable analytical range spans low micrograms/L to tens of mg/L for both methods. The methylene blue method is more sensitive by a factor of approximately 30 and actually permits practical determinations in the sub-micrograms/L levels. The limit of detection (LOD) for the nitroprusside method ranges from 20 micrograms/L for a 20 microL sample by conventional flow-injection determination (no membrane, throughput 30 samples/h) to less than 2 micrograms/L for 12 mL sample pre-concentrated in the membrane system (throughput 5 samples/h). The membrane is highly resistant to fouling and permits analysis of untreated wastewater samples bearing suspended solids, oil, grease, etc. without any pretreatment. No significant interference is observed with either chemistry. Although the nitroprusside chemistry is less sensitive, it does not involve the use of concentrated aggressive reagents and is recommended unless ultratrace determinations are essential. Viable reaction mechanisms are proposed for both of these chemistries.     

Slurry sampling in serum blood for mercury determination by CV-AFS

The heavy metal mercury (Hg) is a neurotoxin known to have a serious health impact even at relatively low concentrations. A slurry method was developed for the sensitive and precise determination of mercury in human serum blood samples by cold vapor generation coupled to atomic fluorescence spectrometry (CV-AFS). All variables related to the slurry formation were studied. The optimal hydrochloric concentration and tin(II) chloride concentration for CV generation were evaluated. Calibration within the range 0.1-10 microg L(-1) Hg was performed with the standard addition method, and compared with an external calibration. Additionally, the reliability of the results obtained was evaluated by analyzing mercury in the same samples, but submitted to microwave-assisted digestion method. The limit of detection was calculated as 25 ng L(-1) and the relative standard deviation was 3.9% at levels around of 0.4 microg L(-1)Hg.     

Gas chromatography-microchip atmospheric pressure chemical ionization-mass spectrometry

An atmospheric pressure chemical ionization (APCI) microchip is presented for combining a gas chromatograph (GC) to a mass spectrometer (MS). The chip includes capillary insertion channel, stopper, vaporizer channel, nozzle and nebulizer gas inlet fabricated on the silicon wafer, and a platinum heater sputtered on a glass wafer. These two wafers are joined by anodic bonding creating a two-dimensional version of an APCI microchip. The sample from GC is directed via heated transfer line capillary to the vaporizer channel of the APCI chip. The etched nozzle forms narrow sample plume, which is ionized by an external corona discharge needle, and the ions are analyzed by a mass spectrometer. The GC-microchip APCI-MS combination provides an efficient method for qualitative and quantitative analysis. The spectra produced by microchip APCI show intensive protonated molecule and some fragmentation products as in classical chemical ionization for structure elucidation. In quantitative analysis the GC-microchip APCI-MS showed good linearity (r(2) = 0.9989) and repeatability (relative standard deviation 4.4%). The limits of detection with signal-to-noise ratio of three were between 0.5 and 2 micromol/L with MS mode using selected ion monitoring and 0.05 micromol/L with MS/MS using multiple reaction monitoring.     

Determination of Trace Level Iodine in Biological and Botanical Reference Materials by Isotope Dilution Mass Spectrometry

A method has been developed for the determination of trace level iodine in biological and botanical materials. The method consists of spiking a sample with ¹²⁹I, equilibration of the spike with the natural iodine, wet ashing under carefully controlled conditions, and separation of the iodine by co-precipitation with silver chloride. Measurement of the ¹²⁹I/¹²⁷I ratio is accomplished by negative thermal ionization mass spectrometry using LaB₆ for ionization enhancement. The application of the method to the certification of trace iodine in two Standard Reference Materials is described.     

ICP-AES法测定盐渍海蜇中的硼

目的:本文研究ICP-AES(Inductively Coupled Plasma-Atomic Emission Spectrometry)测定盐渍海蜇中硼的方法。方法:盐渍海蜇经水浴蒸干、灰化、消解,优化仪器的工作参数后采用ICP-AES上机测定。结果:ICP-AES能够准确测定盐渍海蜇中硼的含量,方法检出限为0.10mg/kg,相对标准偏差低于2%,回收率为97%～104%。结论:该方法操作简便、样品处理简单、干扰少,适合盐渍海蜇中硼的测定。     

A validated liquid chromatography/tandem mass spectrometry assay for cis-amminedichloro(2-methylpyridine)platinum(II) in human plasma ultrafiltrate

The clinical use of platinum drugs as anticancer agents has encountered problems when relating pharmacokinetic profiles with efficacy and toxicity is attempted. This has been mainly due to the lack of specific and sensitive analytical methodology to examine concentrations of the unbound drug in plasma. The presence of a carbocyclic ring on the new drug, cis-amminedichloro(2-methylpyridine)platinum(II) (ZD0473) suggested that it would be possible to develop the first stable isotope dilution LC/MS assay for a platinum drug in human plasma ultrafiltrate samples. The dichloro form of the drug exists in equilibrium with at least two aquated forms in plasma. The molecular form of the drug, therefore, depends on the length of time that the plasma sample is maintained at room temperature before freezing. Therefore, we have developed a method that quantitatively converts the aquated species back to the dichloro form of the parent drug so that a single molecular species can be analyzed. Selected reaction monitoring was performed on the transition of m/z 393 [M + NH4]+ to m/z 304 [M + NH4 -NH3 - 2 x HCl]- for ZD0473, and m/z 400 [M + NH4]+ to m/z 310 [M + NH4 - NH3 - HCl - 2HCl]+ for [2H7]ZD0473. The standard curves were fitted to a quadratic regression over the range from 10 to 5000 ng/mL in human plasma ultrafiltrate. The lower limit of quantitation for ZD0473 was 10 ng/mL for 100 microL of plasma ultrafiltrate. This simple, rapid, reliable, and sensitive method of quantitation had excellent accuracy and precision. The method provided adequate sensitivity for the analysis of plasma ultrafiltrate samples from a phase II study in which ZD0473 was administered to patients as an intravenous infusion at a dose of 150 mg/m2.     

Indirect determination of sulfide at ultratrace levels in natural waters by flow injection on-line sorption in a knotted reactor coupled with hydride generation atomic fluorescence spectrometry

A simple and sensitive nonchromatographic approach for indirect determination of sulfide at ultratrace levels in natural waters based on its selective precipitation with Hg2+ on the inner wall of a knotted reactor (KR) was developed for flow injection on-line sorption coupled with hydride generation atomic fluorescence spectrometry (HG-AFS). With the Hg2+ pH kept at 2.0, the HgS precipitation was formed in the KR after a reaction time of 120 s. A 10% (v/v) HCl was introduced to elute the remnant inorganic mercury and to merge with the KBH4 solution (0.05% m/v) for HG-AFS detection. Under the optimal experimental conditions, the sample throughputs were 20 h(-1). The detection limit was found to be 0.05 microg L(-1), and the relative standard deviation (RSD, n = 11) for determination of 2.0 microg L(-1) sulfide was 3.3%. The developed method was successfully applied to the determination of sulfide in a variety of natural water samples and wastewater samples with the gas-phase separation and sorption apparatus.     

超高效液相色谱-串联质谱法测定育苗基质中矮壮素和缩节胺残留量

研究建立一种检测育苗基质中矮壮素和缩节胺残留的超高效液相色谱-串联质谱法(UPLC-MS/MS)分析方法。样品采用甲醇-乙酸铵水溶液直接提取,样品无需任何净化过程;在亲水作用色谱柱SeQuant ZLC-HILIC MERCK(150 mm×2.1 mm,5μm)上进行分离,再用V(乙腈):V(含0.1%甲酸的20 m mol/L乙酸铵溶液)=6:4为流动相等梯度洗脱;电喷雾正离子(ESI+)模式电离,多反应监测(MRM)模式检测对定性和定量离子进行MS测定,内标法定量。结果表明:矮壮素和缩节胺的添加水平在0.2～10μg/kg的空白添加浓度范围内线性良好(r2>0.999),在1、2和5μg/kg添加水平范围内,平均回收率分别为105.1%～111.6%和72%～110.2%;相对标准偏差(RSD)分别为4.0%～9.2%和7.7%～12.4%,矮壮素和缩节胺2种物质检出限(LOD)为0.2μg/kg,测定低限(LOQ)为1.0μg/kg。该方法简便、快速、灵敏、准确、耐用,适合育苗基质中矮壮素和缩节胺残留的确证和定量测定。     

Determination of aluminum in the human serum of a dialysis patient by ion-pair reversed-phase partition high-performance liquid chromatography.

An ion-pair reversed-phase partition high-performance liquid chromatography-spectrophotometric method is described for the determination of aluminum in human serum, based on its complexation with 2,2'-dihydroxyazobenzene. The chelate is separated on C18-bonded silica packing by using an aqueous methanol mobile phase containing tetrabutylammonium bromide and is detected with 0.005 AU full-scale at 510 nm. The proposed system offers a simple, sensitive, and selective method. The detection limits defined as twice the standard deviation of the blank signal, are 0.2 micrograms L-1 in pure solution and 6 micrograms L-1 in serum. The sample solution is prepared from 0.4 mL of serum after protein precipitation with hydrochloric acid and methanol. There was good agreement between the values obtained by this method and graphite furnace atomic absorption spectrophotometry. The aluminum concentrations in 121 patients on hemodialysis were 6-201 micrograms L-1.     

微波灰化法测定进出口饲料中的灰分

采用程序升温微波灰化法测定饲料中的灰分,方法可靠、操作简单,适应性强,大大缩短了检测周期。其结果与国标法GB／T5009,4—2003、行业标准SN／T0800,6—1999均无显著性差异。     

Development and evaluation of a reference measurement procedure for the determination of estradiol-17beta in human serum using isotope-dilution liquid chromatography-tandem mass spectrometry

Estradiol is the most potent natural estrogen and is derived from the ovaries. Its concentration in blood is measured to determine ovarian function. A reference measurement procedure for estradiol in serum involving isotope-dilution coupled with liquid chromatography-tandem mass spectrometry (LC/MS/MS) has been developed and critically evaluated. A deuterated estradiol (estradiol-d3) was used as an internal standard. The estradiol and its internal standard were extracted from serum matrix using solid-phase extractions and derivatized with dansyl chloride prior to reversed-phase LC/MS/MS. The accuracy of the measurement was evaluated by a comparison of results of this reference method on lyophilized human serum reference materials for estradiol [Certified Reference Materials (CRMs) 576, 577, and 578] with the certified values determined by gas chromatography/mass spectrometry (GC/MS) reference methods and by a recovery study for the added estradiol. The results of this method for estradiol agreed with the certified values within the uncertainty of the measurements for the three CRMs. The recovery of the added estradiol ranged from 100.7 to 101.8%. This method was applied to the determination of estradiol in frozen serum samples from three individual female donors. Excellent reproducibility was obtained with within-set coefficient of variations (CVs) ranging from 0.6 to 2.2% and between-set CVs ranging from 0.2 to 0.4%. Excellent linearity was also obtained, with correlation coefficients of all linear regression lines (measured intensity ratios vs mass ratios) ranging from 0.998 to 1.000. The detection limit at a signal-to-noise ratio of approximately 3 was 0.6 pg of estradiol (or 1 ng/L, as expressed as a concentration). This well-characterized LC/MS/MS method for serum estradiol, which demonstrates good accuracy and precision, low susceptibility to interferences, and comparability with GC/MS reference methods, qualifies as a reference measurement procedure that can be used to provide an accuracy base to which routine methods for estradiol can be compared and that will serve as a standard of higher order for measurement traceability.     

Separation and identification of twelve catechins in tea using liquid chromatography/atmospheric pressure chemical ionization-mass spectrometry

A method has been developed for the direct microscale determination of 12 catechins in green and black tea infusions. The method is based on liquid chromatography/atmospheric pressure chemical ionization-mass spectrometry (LC/APCI-MS). Standard catechin mixtures and tea infusions were analyzed by LC/APCI-MS with detection of protonated molecular ions and characteristic fragment ions for each compound. The identities of eight major catechins and caffeine in tea were established based on LC retention times and simultaneously recorded mass spectra. In addition, monitoring of the catechin-specific retro Diels-Alder fragment ion at m/z 139 throughout the chromatogram provided a unique fingerprint for catechin content in the samples that led to the identification of four minor chemically modified catechin derivatives in the infusions. This report is the first to describe the comprehensive determination of all 12 reported catechins in a single analysis. The utility of LC/APCI-MS for providing routine separation and identification of catechins at femtomole to low-picomole levels without extraction or sample pretreatment, and its potential as a standard analytical tool for the determination of polyphenols in natural products and biological fluids, are discussed.     

能量色散X射线荧光光谱法测定铂钌合金中的铂含量

应用能量色散X射线荧光光谱法（EDXRF）对铂钌合金（铂含量为90％～96％）中铂含量进行测定。利用一套铂钌为主量的工作标样,测量并收集此工作标样所含元素的特征X射线光谱,建立标准工作曲线,编制和优化分析程序,测定铂钌合金中铂元素的含量。对铂钌合金样品的测试结果与其他方法进行比较,证明方法可行。铂钉合金中铂含量在90％-96％时,分析精度优于0．3％。