直接进样-冷原子吸收光谱法测定矿产品中汞

无需离线的化学前处理而直接进样,热解汞齐化后在波长253.65 nm处用冷原子吸收光谱法进行汞的测定。对取样量、样品测定方式及背景值控制、仪器分析条件的选择等进行了探讨。方法的线性范围为0.1~600 ng,检出限为0.000 7μg/g。将该方法用于两个参考矿产样中汞的测定,结果与参考值相符,相对标准偏差(n=7)分别为3.3%和1.1%;用本方法、消解后利用冷原子吸收光谱法和电感耦合等离子体原子发射光谱法对铜精矿、锰矿、锌矿等含汞矿样进行测试比较,方法间无显著性差异。测定一个样品仅需5 min,样品用量少,适合批量样品的测试。     

直接粉末进样-能量色散X射线荧光光谱法测定地质样品中多种组分

为提高现场快速分析的能力,充分发挥小型实验室设备的功能,实验采用能量色散X射线荧光光谱仪,直接使用粉末样品分析常规地质样品中的多种组分。用理论α系数和康普顿内标校正基体效应和谱线重叠干扰,直接将粉碎加工到200目(74μm)的样品放在液体塑料盒中进行测量。对地质样品标准物质进行样品用量试验表明,样品用量大于3.0g时,测量结果趋于稳定或者在认定值的准确度控制范围内变动,实验时选取4.0g作为样品用量。精密度试验表明,除组分La、Ce、Sn、W、U和Na_2O的相对标准偏差(RSD,n=12)大于10%外,其他组分的RSD都小于10%,尤其是组分Ti、Mn、Co、Rb、Sr、SiO_2、K_2O、CaO和Fe_2O_3的RSD都在1%以下。通过对未参加回归的标准物质的验证,参照《地球化学普查(比例尺1∶50 000)规范样品分析技术要求补充规定》,该法对常规地质样品可定量分析Ti、V、Mn、Co、Ni、Cu、Zn、Ga、As、Rb、Sr、Y、Zr、Nb、Th、U、K_2O、CaO和Fe_2O_3等19种组分,近似定量分析Ce和W,半定量分析Cr、La、Sn、SiO_2和Na_2O。由于将样品放入液体塑料盒中进行测量,无需压片制样设备,该法适合野外现场分析应用。     

Characterisation of TNF-alpha-related peptides by high-performance liquid chromatography-mass spectrometry and high-performance liquid chromatography-tandem mass spectrometry

Ion-spray triple quadrupole mass spectrometry and high-performance liquid chromatography were used to investigate the products from the solid phase synthesis of (H)-Leu-Thr-Glu-Asn-(OH), a TNF-alpha active-site probe. The target sequence was assembled using tert.-butoxycarbonyl (Boc) chemistry in stepwise fashion from the C-terminal on an Boc-Asn-OCH2-Pam-copoly(styrene-divinylbenzene) resin [Pam = 4-(carboxamidomethyl)benzyl ester]. The crude product was deprotected and cleaved from the resin by HF-p-cresol treatment for 1 h at 0 degrees C. HPLC analysis at 214 nm indicated two late-eluting major products and an early-eluting product. Preparative HPLC demonstrated that the early-eluting product contained ca. 80% of the expected recovered sample mass. Each component was then directly analysed by mass spectrometry and tandem mass spectrometry. The early eluting peak was confirmed as the desired LTEN sequence. Synthesis of the same sequence using 9-fluorenyl methoxycarbonyl (Fmoc) chemistry gave an identical product and confirmed the above analysis. The most significant by-product was derived from arylation of the glutamyl group by the quencher p-cresol. The likely origins of the by-products are discussed.     

Analysis of antibiotics by liquid chromatography-mass spectrometry

We examined the time-resolved and steady-state fluorescence quenching of N-acetyl-L-tryptophanamide (NATA) by acrylamide and iodide, over a range of viscosities in propylene glycol. The quenching of NATA by acrylamide and iodide results in heterogeneity of the intensity decay which increases with the quencher concentration. We attribute the complex decays of NATA to transient effects in diffusion and the nature of the fluorophore-quencher interaction. These data were compared using the phenomenological radiation boundary condition (RBC) and distance-dependent quenching (DDQ) models for collisional quenching. We used global analysis of the time-resolved frequency-domain and steady-state data to select between the models. Consideration of both the frequency-domain and steady state data demonstrate that the quenching rate depends exponentially on the fluorophore-quencher distance, indicating the validity of the DDQ model. The rate constants for acrylamide and iodide quenching, at the constant distance of 5 A, were found to be near 10(13) s-1 and 10(9) s-1, respectively. These rates reflect electron transfer and exchange interactions as the probable quenching mechanisms, respectively.     

Mass spectrometry of cannabinoids

The mechanism of fragmentation of cannabinoids to fragments m/e 314, 299, 271, 258, 246, 243, and 231 is given. Cannabidiol cannabinoidiol, cannabinol, delta6- and delta1-tetrahydrocannabinol, cannabichromene, cannabicyclol, derivatives with pentyl, propyl, and methyl side chains, their methyl ethers, and cis-trans and ortho-para isomers were analyzed by GLC-mass spectrometry using different energies for fragmentation during GLC elution. The following mechanism was distinguished: loss of a methyl radical, ring closure and rotation, McLafferty rearrangement, retro Diels-Alder, internal protonation, isomerization and internal bond formation, and one-step fragmentation to m/e 231.     

Rapid identification of comigrating gel-isolated proteins by ion trap-mass spectrometry

In the search for novel nuclear binding proteins, two bands from a sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) gel were analyzed and each was found to contain a number of proteins that subsequently were identified by tandem mass spectrometry (MS/MS) on a quadrupole ion trap instrument. The bands were digested with trypsin in situ on a polyvinylidene difluoride (PVDF) membrane following electroblot transfer. Analysis of a 2.5% aliquot of each peptide mixture by matrix assisted laser desorption/ionization-mass spectrometry (MALDI-MS) followed by an initial database search with the peptide masses failed to identify the proteins. The peptides were separated by reversed-phase capillary high performance liquid chromatography (HPLC) in anticipation of subsequent Edman degradation, but mass analysis of the chromatographic fractions by MALDI-MS revealed multiple, coeluting peptides that precluded this approach. Selected fractions were analyzed by capillary HPLC-electrospray ionization-ion trap mass spectrometry. Tandem mass spectrometry provided significant fragmentation from which full or partial sequence was deduced for a number of peptides. Two stages of fragmentation (MS3) were used in one case to determine additional sequence. Database searches, each using a single peptide mass plus partial sequence, identified four proteins from a single electrophoretic band at 45 kDa, and four proteins from a second band at 60 kDa. Many of these proteins were derived from human keratin. The protein identifications were corroborated by the presence of multiple matching peptide masses in the MALDI-MS spectra. In addition, a novel sequence, not found in protein or DNA databases, was determined by interpretation of the MS/MS data. These results demonstrate the power of the quadrupole ion trap for the identification of multiple proteins in a mixture, and for de novo determination of peptide sequence. Reanalysis of the fragmentation data with a modified database searching algorithm showed that the same sets of proteins were identified from a limited number of fragment ion masses, in the absence of mass spectral interpretation or amino acid sequence. The implications for protein identification solely from fragment ion masses are discussed, including advantages for low signal levels, for a reduction of the necessary interpretation expertise, and for increased speed.     

Thermodynamics of the liquid binary iron-tin by mass spectrometry

The first study of the entire liquid binary iron-tin is reported. The system exhibits ideal/Henrian behavior on the iron-rich side, and pseudoregular behavior on the tinrich side. Near 1300°C the miscibility gap in the liquid is evident; at 1500°C it cannot be ascertained by the mass spectrometric method. The center of the tendency for demixing is near xsn = 0.60. The activity coefficients at 1537°C are in the range 0 < xsn < 0.41: γFe = 1 and γsn = 2.15; in the range 0.79 <xSn < 1-00: lnγ_Fe = -0.41 + 2.31x²Sn and ln γsn = 2.36 x²Fe. SIGURD WAGNER, formerly Postdoctoral Fellow, Department of Metallurgical Engineering, Ohio State University, Columbus, Ohio     

Thermodynamics of the liquid binary iron-titanium by mass spectrometry

At 1545°C (1818 K) the liquid binary system iron-titanium is symmetric and regular with the integral excess Gibbs energy and the integral enthalpy of mixing equal to − 9,700 cal (−40,600 J)x _Fe x _Ti Per g-atom referred to the liquid components. Formerly Postdoctoral Fellow, Department of Metallurgical Engineering, Ohio State University, Columbus, Ohio     

Characterisation of cholera toxin by liquid chromatography--electrospray mass spectrometry

Cholera toxin, one of the toxins that may be generated by various strains of the bacterium Vibrio cholerae, can be considered as a substance possibly used in biological warfare. The possibilities of characterising the toxin by liquid chromatography electrospray mass spectrometry (LC-ES-MS) were investigated. The toxin can be detected by flow-injection (FIA) ES-MS of a dialysed solution and observation of the charge envelope signals of its A-unit and B-chain protein; sufficient information for identification by the molecular mass of either protein could be obtained for quantities in the order of 10 fmol. Confirmatory analysis was carried out by 2-mercaptoethanol reduction and FIA-ES-MS detection of the product proteins or by tryptic digest LC-ES-MS with ion chromatogram detection of most of the tryptic fragments of the A-unit and B-chain from the singly, doubly or triply charged ion signals. The confirmatory tryptic digest LC-ES-MS analysis could be achieved with quantities as low as 1 pmol. Possible biovariations in the toxin can mostly be determined by sequencing, where the amino acid composition of tryptic fragments of the A1-chain, T5 and T15, and of the B-chain, T1, T4 and T5, cover all known biovariations. Partial sequencing of cholera toxin, originating from a classical strain, O1/569B, was achieved by LC-ES-MS/MS of most tryptic fragments larger than three amino acid residues.     

煤中天然有机物的高效液相色谱-质谱/质谱分析

运用红外光谱法测定褐煤氧化前后的结构变化,在1580cm-1及1400cm-1处的两个特征峰表明氧化煤中含有大量的羧酸类物质。以此为基础,采用温和的碱氧化方法对煤进行氧化处理,选择了合适的分离条件,建立了氧化煤中天然有机物质预分离样品的高效液相色谱方法,并通过电喷雾串联质谱(ESI(-)-MS/MS)法对其中一组质量数相差58的物质进行了细致的分析。选择m/z268为特征吸收峰,并依据煤的大分子结构,对分析得到的物质进行细致的结构推测,认为该物质应为含有两个乙酸基侧链的炔基喹啉,其化学式为C15H11NO     

Mass spectrometry of N-acylated daunorubicin derivatives

The mass spectra of peracetylated daunorubicin, N-octanoyl-, N-dodecanoyl- and N-(N'-dodecanoyl-glycyl)daunorubicin, and perdeuteroacetylated N-dodecanoyldaunorubicin were analyzed. Major fragmentation pathways were suggested and ion compositions were determined by high resolution measurements.     

The use of high-flow high performance liquid chromatography coupled with positive and negative ion electrospray tandem mass spectrometry for quantitative bioanalysis via direct injection of the plasma/serum samples

Two bioanalytical methods have been developed and validated utilizing high flow high performance liquid chromatography (HPLC) for on-line purification of plasma and serum samples and electrospray tandem mass spectrometry for detection and quantitation. Each plasma or serum sample, after mixing with an aqueous solution of the internal standard, was injected into a small diameter (1 x 50 mm) column packed with large particles of OASIS (30 microns), with a 100% aqueous mobile phase at a high flow rate (3-4 mL/min). The combination of the high linear speed (6-8 cm/s) of the aqueous mobile phase and the large particle size resulted in the rapid passage of the proteins and other large biomolecules through the column while the small-molecule analytes were retained on the column. During this purification period, the HPLC effluent was directed to waste. After the purification step, the HPLC mobile phase was rapidly changed from 100% aqueous to < or = 100% organic, the flow was reduced to 0.5-0.8 mL/min, and the column effluent was directed towards the mass spectrometer. The small molecule analytes were eluted during this period. In the method developed and validated for the quantitative determination of compound I in rat plasma (method A), the same OASIS column (1 x 50 mm, 30 microns) served as the purification and analytical (elution) column. In the method developed for the simultaneous determination of pravastatin and its positional isomer biotransformation product (SQ-31906) in human serum (method B), the purification column was connected to a conventional C18 analytical column (3.9 x 50 mm, 5 microns) to achieve the required chromatographic separation between the two isomers. For method A, where 50 microL of rat plasma mixed 1:1 with water containing the internal standard was injected, the standard curve range was 1 to 1,000 ng/mL. For method B, where 200 microL of a human serum sample mixed 4:1 with water containing the internal standard was injected, the standard curve range was 0.5 to 100 ng/mL. The total analysis time for each method was < or = 5 min per sample. The accuracy, inter-day precision and intra-day precision were within 10% for both methods.     

Analysis of novel hydroperoxides and other metabolites of oleic, linoleic, and linolenic acids by liquid chromatography-mass spectrometry with ion trap MSn

Linoleate is oxygenated by manganese-lipoxygenase (Mn-LO) to 11S-hydroperoxylinoleic acid and 13R-hydroperoxyoctadeca-9Z,11E-dienoic acid, whereas linoleate diol synthase (LDS) converts linoleate sequentially to 8R-hydroperoxylinoleate, through an 8-dioxygenase by insertion of molecular oxygen, and to 7S,8S-dihydroxylinoleate, through a hydroperoxide isomerase by intramolecular oxygen transfer. We have used liquid chromatography-mass spectrometry (LC-MS) with an ion trap mass spectrometer to study the MSn mass spectra of the main metabolites of oleic, linoleic, alpha-linolenic and gamma-linolenic acids, which are formed by Mn-LO and by LDS. The enzymes were purified from the culture broth (Mn-LO) and mycelium (LDS) of the fungus Gaeumannomyces graminis. MS3 analysis of hydroperoxides and MS2 analysis of dihydroxy- and monohydroxy metabolites yielded many fragments with information on the position of oxygenated carbons. Mn-LO oxygenated C-11 and C-13 of 18:2n-6, 18:3n-3, and 18:3n-6 in a ratio of approximately 1:1-3 at high substrate concentrations. 8-Hydroxy-9(10)epoxystearate was identified as a novel metabolite of LDS and oleic acid by LC-MS and by gas chromatography-MS. We conclude that LC-MS with MSn is a convenient tool for detection and identification of hydroperoxy fatty acids and other metabolites of these enzymes.     

Mass spectrometry of ribosomes and ribosomal subunits

Nanoflow electrospray ionization has been used to introduce intact Escherichia coli ribosomes into the ion source of a mass spectrometer. Mass spectra of remarkable quality result from a partial, but selective, dissociation of the particles within the mass spectrometer. Peaks in the spectra have been assigned to individual ribosomal proteins and to noncovalent complexes of up to five component proteins. The pattern of dissociation correlates strongly with predicted features of ribosomal protein-protein and protein-RNA interactions. The spectra allow the dynamics and state of folding of specific proteins to be investigated in the context of the intact ribosome. This study demonstrates a potentially general strategy to probe interactions within complex biological assemblies.     

Determination of arylphenoxypropionic herbicides in water by liquid chromatography-electrospray mass spectrometry

The study described here investigates the replicability of gender-specific risk profiles for gonorrhea based on an Alaskan sample compared to a U.S. national sample of drug users at risk for HIV infection. The Alaska sample (interviewed at a field station in Anchorage, Alaska; N=1,049) and the national sample (interviewed at 18 sites other than Alaska; N=17,619) consisted of cocaine smokers and injection drug users not in drug treatment. A history of gonorrhea infection was self-reported and coded as ever or never. The Anchorage and national risk profile for men included the following factors: (a) history of intranasal or parenteral cocaine use, (b) being black versus nonblack, (c) being older, (d) income from illegal activity, and (e) history of amphetamine use. The Anchorage and national risk profiles for women included the following factors: (a) trading sex for money, (b) being Native American versus non-Native American, and (c) trading sex for drugs. The Anchorage model for women included perceived homelessness as a factor, but it was not retained in the national model. The extent of the replicability of these models illustrates the generalizability of Alaskan findings to other U.S. drug-using populations. The authors also discuss the implications of these findings for disease prevention.     

离子色谱法测定电镀液中F-和Cl-

提出了离子色谱法检测电镀液中F-和Cl-的方法.根据高沸点酸置换低沸点酸,用硫酸作为蒸馏剂,在一定的温度下,将F-和Cl-一起蒸馏出进行分离和富集,消除了电镀液中大量共存离子的干扰和对色谱柱的污染.使用IonPacASl4A作为色谱柱,在合适的色谱条件下,F-和Cl-的色谱峰能很好地分离,其检出限分别为0.84 μg/L和0.37 μg/L,相对标准偏差F-小于7.3%,Cl-小于4.2%(n=10),加标回收率F-在91%～107%、Cl-在95%～105%之间(n=10),电镀液中共存离子对F-和Cl-的测定无干扰.方法用于电镀液中F-和Cl-的同时测定,具有很好的可行性和实用性.     

Future potential of targeted component analysis by multidimensional liquid chromatography-mass spectrometry

Multidimensional liquid chromatography (MDLC) may be used in either (i) the profiling mode where it is the objective to fractionate all components in a mixture or (ii) the targeted component mode in which it is the objective to determine specific analytes. This paper focuses on targeted component analysis from complex mixtures, addressing the critical operations of analyte selection and transport from the first to the second dimension. Although the physical operation of switching a component into the second dimension with computer controlled valving is simple, it is shown that changes in analyte retention time and peak width with column age and fouling are a serious problem. The analyte moves out of the preselected time window for valve switching and quantitation is compromised in the second dimension. It is proposed that a solution to the "drifting peak" phenomenon in targeted component analysis is to use binary mobility elution in the first dimension. Binary mobility refers to those systems, such as affinity chromatography, in which analyte mobility is generally either 0 or 1 relative to mobile phase velocity. Coupling these binary changes in analyte mobility in the first dimension with valve switching eliminates the "drifting peak" phenomenon. In addition, it is shown that a wide time window may be used in affinity separations without compromising the separation or accumulating contaminants. Several cases are described in which immunosorbents were used with reversed phase columns to provide quantitative targeted component analyses from complex mixtures.