乳粉中黄曲霉毒素M1残留标准物质研制

通过饲喂牛的方式获得乳粉中黄曲霉毒素M1阳性乳品,经冷冻干燥、混匀、包装、分装、辐照灭菌制备了乳粉中黄曲霉毒素M1标准物质。6家实验室均采用液相色谱-同位素稀释质谱法对乳粉中黄曲霉毒素M1标准物质进行联合定值。分别采用F检验和t检验对标准物质进行均匀性、稳定性检验,结果表明该标准物质均匀性与稳定性良好,均符合标准物质定值技术要求。对定值结果进行不确定度评定,乳粉中黄曲霉毒素M1残留标准物质定值结果为(2.45±0.41)μg/kg,k=2。该标准物质可用于乳品中黄曲霉毒素M1的日常质量控制及定量检测。     

血清中皮质醇成分分析标准物质的研制

皮质醇是一种重要的肾上腺皮质激素,同时也是一种重要的临床诊断标志物,为保证检测结果具有溯源性、可比性和准确性,研制了血清中皮质醇成分分析标准物质。对血清样品进行分离、过滤、混匀、分装,进行均匀性检验、稳定性考察和定值分析。采用超高效液相色谱–同位素稀释串联质谱(UPLC–ID–MS/MS)法进行定值,混合健康男性血清和健康女性血清中皮质醇的定值结果分别为107.63 ng/g(U=1.44 ng/g,k=2),92.24 ng/g(U=1.68 ng/g,k=2)。采用CCQM–K63a比对样品对定值方法进行验证,测量结果在该比对参考值的不确定度范围内。研制的皮质醇成分分析标准物质符合国家一级标准物质技术要求。     

标准物质的定值

介绍标准物质定值的要求和过程.     

毫米波反射率标准物质定值的不确定度评定

对毫米波反射率标准物质定值的不确定度进行了评定,分析了各不确定度分量的来源并进行了量化.毫米波反射率标准物质的扩展不确定度U≤1dB(k=2),满足技术指标要求.结果表明,影响不确定度的主要因素为标准物质的稳定性.     

NTO纯度标准物质定值研究

为了对纯度标准物质3-硝基-1,2,4-三唑-5-酮(NTO)定值,获得其纯度值和不确定度,采用"杂质扣除法"对标准物质进行定值,用化学分析法对定值结果进行验证.通过对定值过程的A、B类不确定度评定,获得定值结果的不确定度.NTO纯度标准物质的纯度值为99.57%,扩展不确定度U=0.02%(k=2).     

关于铀同位素标准物质的几个问题

讨论了铀同位素标准物质(UIRM)研制中的一些技术问题,如IRM中同位素丰度的定值,IRM不确定度的影响因素等,并介绍了国内外UIRM研制情况。     

同位素稀释-超高效液相色谱-串联质谱法同时测定水产品中15种头孢菌素的残留量北大核心CSCD

提出了同位素稀释-超高效液相色谱-串联质谱法(UHPLC-MS/MS)同时测定水产品中15种头孢菌素残留量的方法。称取处理好的样品5 g,加入100μg·L^(-1)同位素内标混合溶液200μL,静置30 min后,再加入酸性氧化铝2 g,用5 mL 80%(体积分数)乙腈溶液重复提取两次,合并上清液。将上清液转移至Oasis Prime HLB固相萃取小柱,收集流出液,于40℃氮吹至1 mL左右,再加入含0.1%(体积分数)甲酸的乙腈溶液1 mL,经0.22μm尼龙滤膜过滤。以Agilent InfinityLab Poroshell 120 SB C_(18)色谱柱为固定相,以不同体积比的0.1%(体积分数)甲酸溶液和乙腈的混合液为流动相进行梯度洗脱,选择电喷雾离子源正离子(ESI^(+))模式和多反应监测(MRM)模式进行分析,内标法定量。结果显示:15种头孢菌素的质量浓度在一定范围内与其对应的响应值与内标响应值的比值呈线性关系,检出限(3S/N)为0.3~2.0μg·kg^(-1);对空白样品进行3个浓度水平的加标回收试验,回收率为75.9%~119%,测定值的相对标准偏差(n=6)为1.6%~6.5%。方法用于实际样品分析,其中1份草鱼样品中检出头孢氨苄,检出量为3.78μg·kg^(-1)。     

乙酰甲胺磷丙酮溶液标准物质的制备及定值

采用乙酰甲胺磷纯度标准物质为原料,以丙酮为溶剂,制备了浓度为1．00mg／mL的乙酰甲胺磷丙酮溶液标准物质,用液相色谱法和气相色谱法进行了确认,A类标准不确定度为0．009％,B类标准不确定度包括标准物质制备、原料纯度、不均匀性和不稳定性引入的不确定度,其量值分别为0．43％,0．10％,0．87％和0．24％,合成不确定度为0．03mg／mL（k=-2）,乙酰甲胺磷丙酮溶液标准物质的浓度为（1．00±0．03）mg／mL。     

睾酮甲醇溶液标准物质的定值及不确定度评定

针对目前食品中兴奋剂类药物检测的需求,研制了睾酮甲醇溶液国家级标准物质。通过对经筛选的市售原料纯品进行液相色谱-质谱(LC-MS)和红外光谱(IR)定性分析后,利用高效液相色谱法(HPLC)对睾酮蛋白同化类固醇类兴奋剂原料进行纯度定值。利用HPLC在244nm监测,0.1%HAc-乙腈(50∶50,体积比)作为流动相进行等度洗脱,以Inertsil ODS-SP(250mm×4.6mm,5μm)进行分离,测得液相条件下睾酮固体的纯度为99.89%。为保证纯度测量的准确性,采用多家联合定值对睾酮的纯度进行检验。睾酮溶液标准物质经重量-重量法配制后,进行均匀性和稳定性实验,浓度赋值后进行不确定度评定。研制的睾酮溶液标准物质目前已被批准为国家二级标准物质并应用于实际检测。     

超高效液相色谱-三重四极杆质谱法测定化妆品中秋水仙碱、秋水仙胺和秋水仙碱苷EI北大核心CSCD

建立了一种同时测定化妆品中秋水仙碱、秋水仙胺和秋水仙碱苷的超高效液相色谱-三重四极杆质谱分析方法。试样经正己烷饱和的甲醇-乙腈(1∶1,V/V)混合溶剂超声提取,蜡基类样品经正己烷溶解分散后提取,膏霜类样品在提取液中加入乙酸铵以改善样品乳化情况,提取液离心过滤后,以5 mmol/L乙酸铵(含0.1%甲酸)-甲醇作为流动相梯度洗脱,经ACQUITY UPLC BEH C_(18)色谱柱分离后,采用超高效液相色谱-三重四极杆质谱在电喷雾正离子电离模式和多反应监测(MRM)模式检测。3种化合物在0.5~10μg/L范围内线性关系良好,相关系数大于0.995,检出限为3.0μg/kg,定量限为10.0μg/kg,在10.0,20.0,100μg/kg 3个加标水平下的平均回收率为81.5%~109.2%,相对标准偏差为0.5%~8.7%。该方法适用于化妆品中秋水仙碱、秋水仙胺和秋水仙碱苷的测定。     

Quadrupole ion trap mass spectrometry: a view at the turn of the century

A personal account of the quadrupole ion trap researches carried out in my laboratory and in collaboration with other laboratories. This account commences with the announcement, in 1983, of the first commercially available ion trap detector, manufactured by Finnigan MAT, and continues to the present day. Much of the ion trap mass spectrometry research that took place during the period following this announcement until 1994 has been discussed in detail in three volumes entitled Practical Aspects of Ion Trap Mass Spectrometry that were published in 1995. Except for those researches that impinged directly on our work during this period, no discussion of the contents of these three volumes is repeated here. The ion trap literature from 1994 to the present has been reviewed selectively so as to convey to the reader the dynamic nature of ion trap mass spectrometry and the wide variety of its application.     

Determination of rosiglitazone and metformin in human serum by CE-ESI-MS

A new method for the determination of anti-diabetic drugs metformin and rosiglitazone based on the use of capillary electrophoresis with electrospray mass spectrometry was developed. The proposed method allowed their separation within 11 min by using 50 mM formic acid at +20 kV. Positive electrospray ionization and selected ion monitoring [M+H](+) of metformin (m/z=130) and rosiglitazone (m/z=358) were performed. Several important experimental parameters influencing electrospray ionization of metformin and rosiglitazone were studied. The final composition of sheath liquid was water/methanol/formic acid (50:49.5:0.5, v/v/v), at a flow rate of 2 μL/min. The developed method was applied for the determination of metformin and rosiglitazone simultaneously in human serum after protein precipitation with acetonitrile. The limits of detection of developed method were 4.42 and 2.14 ng/mL for rosiglitazone and for metformin, respectively, which is sufficient for therapeutic serum concentration levels monitoring for both studied drugs.     

Determination of trace levels of pyrethroid metabolites in human urine by capillary gas chromatography-high resolution mass spectrometry with negative chemical ionization

Summary Applications of high-resolution gas chromatography and high-resolution mass spectrometry (GC-MS) for identification and quantitation of trace amounts of pyrethroid metabolites in human urine samples are demonstrated. The method covers the pyrethroid metabolitescis- andtrans-3-(2,2-dichlorovinyl)-2,2-dimethyl-cyclopropane carboxylic acid (cis- andtrans-DCCA),cis-3-(2,2-dibromovinyl)-2,2-dimethylcyclopropane carboxylic acid (cis-DBCA), 4-fluoro-3-phenoxybenzoic acid (FPBA), and 3-phenoxybenzoic acid (3-PBA). After acid-induced hydrolysis of urine samples and exhaustive solvent extraction, a carbodiimide-coupled esterification of the free carboxylic acids with hexafluoroisopropanol (HFIP) is applied. Identification of the derivatives formed is achieved by low-resolution electron-impact mass spectrometry (EIMS) using an ion-trap detector. Quantitation was by capillary gas chromatography—high-resolution mass spectrometry using negative chemical ionization (GC-NCIMS). 2-Phenoxybenzoic acid (2-PBA) served as internal standard. The limits of detection forcis- andtrans-DCCA,cis-DBCA, FPBA and 3-PBA were 0.03 μg L⁻¹ or below. The applicability of the presented method was tested on urine samples of persons exposed to low levels of pyrethroids.     

Determination of misoprostol free acid in human breast milk and serum by gas chromatography/negative ion chemical ionization tandem mass spectrometry

To study an expected transition of misoprostol from human blood into breast milk, a novel method for the determination of its active metabolite misoprostol acid (MPA) was developed. MPA was determined in serum and breast milk samples by an isotope dilution assay using gas chromatography/negative ion chemical ionization tandem mass spectrometry (GC/NICI-MS/MS). After addition of (15S)-15-methylprostaglandin E(2) (15-methyl-PGE(2)) as an internal standard, MPA was extracted from both matrices using a reversed-phase cartridge. The prostanoids were derivatized with O-2,3,4,5,6-pentafluorobenzylhydroxylamine hydrochloride (PFBHA) and 2,3,4,5,6-pentafluorobenzyl bromide (PFBB) to the pentafluorobenzyl oxime (PFBO)-pentafluorobenzyl ester (PFB) derivatives. The sample was subjected to thin-layer chromatography with ethyl acetate-hexane (1 : 1 (v/v)) as the developing solvent. The corresponding zone was extracted. After derivatization to the trimethylsilyl ether, MPA was determined by GC/NICI-MS/MS using the [molecule (M) - pentafluorobenzyl (PFB)](-) ([P](-)) ions as precursor in the negative ion chemical ionization mode. The product ions used for quantification were [P - 2TMSOH - C(6)F(5)CH(2)OH](-) (MPA) and [P - 2TMSOH - C(6)F(5)CH(2)OH - CO(2)](-)(15-methyl-PGE(2)), respectively. The limit of quantification for MPA was approximately 1 pg ml(-1) in breast milk and serum samples. The correlation coefficients of the calibration curves for MPA were r > 0.997 in the 0.5-2000 pg ml(-1) range for both tested matrices.     

Separation and identification of ceramides in the human stratum corneum by high-performance liquid chromatography coupled with electrospray ionization mass spectrometry and electrospray multiple-stage mass spectrometry profiling

Summary A sensitive, selective, and rapid method is described for analysis of ceramides in the human stratum coracum by direct coupling of HPLC with an electrospray ion-trap mass spectrometry. Nonaqueous reversed-phase chromatography stabilizes the electrospray ionization, resulting in sensitivity that enables direct measurement of skin lipid extracts with no special sample preparation. Assignment of individual signals to the corresponding ceramide species is based on interpretation of the fragment spectra from MS-MS experiments. This enables much finer differentiation between ceramdies than that achievable by thin-layer chromatography. Summary A sensitive, selective, and rapid method is described for analysis of ceramides in the human stratum corneum by direct coupling of HPLC with an electrospray ion-trap mass spectrometry. Nonaqueous reversed-phase chromatography stabilizes the electrospray ionization, resulting in sensitivity that enables direct measurement of skin lipid extracts with no special sample preparation. Assignment of individual signals to the corresponding ceramide species is based on interpretation of the fragment spectra from MS-MS experiments. This enables much finer differentiation between ceramides than that achievable by thin-layer chromatography.     

Determination of brominated alkylbenzenes in nickel industry sludge by capillary gas chromatography

Summary Capillary gas chromatography coupled to both mass spectrometry (GCMS) and atomic emission spectroscopy (GC-AED) was studied for the analysis of bromine-containing alkylbenzenes present in sludge from a nickel refinery. Owing to the high abundance of chlorinated compounds, location of the brominated species was difficult based on GC-MS with electron ionization. In contrast, GC-MS with negative chemical ionization (GC-NCIMS) and GC-AED enabled bromine-selective detection and were utilized for an effective location of the brominated compounds. Bromine-selective detection by GC-NCIMS relied on the monitoring of Br⁻ (m/z 79/81) with CH₄ as ionization gas, while atomic emission (827.2 nm) from a helium plasma was utilized in the case of GC-AED. While GC-NCIMS was 30–500 times more sensitive than GC-AED, the latter technique was superior for quantitative purposes. Because the bromine response of the AED was independent of molecular structure, quantification was possible without reference material.     

Application of atmospheric pressure ionization HPLC-MS-MS for the analysis of natural products

Summary The development of techniques utilizing atmospheric pressure ionization, namely atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI), has pioneered the coupling of liquid chromatography (HPLC) with mass spectrometry in recent years. Both ESI and APCI generate ions from polar and labile biomaterials with remarkable ease and efficiency. In particular, the use of HPLC with tandem mass spectrometry (MS-MS) opens further dimensions in the field of bioorganic analysis. Thus, HPLC-MS-MS provides the tools for direct elucidation of the structure and variety of polar natural compounds in complex matrices. In order to develop efficient and straightforward strategies for the analysis of polar natural products, the potential and the limitations of these hyphenated analytical techniques are discussed using heterocyclic aromatic amines, fumonisins, acylated glycoconjugates and regioisomeric fatty acid hydroperoxides as examples. Presented at the 21^st ISC held in Stuttgart, Germany, 15^th–20^th September, 1996     

Separation of Amadori peptides from their unmodified analogs by ion-pairing RP-HPLC with heptafluorobutyric acid as ion-pair reagent

Glycation is a common class of nonenzymatic posttranslational modifications relevant for several diseases and cell aging in general, such as D-glucose-derived modifications at the ɛ-amino groups of lysine residues in blood proteins, especially albumin, immunoglobulin, and hemoglobin, for diabetic patients. These Amadori compounds are identified on the peptide level after enzymatic digestion and chromatographic separation by mass spectrometry. Their syntheses usually rely on a global glycation approach. Both areas require the reliable separation of glycated peptides from their unmodified congeners present in different ratios, which is typically not achieved by standard eluent systems in ion-pairing RP-HPLC (IP-RPLC). Here, we compare aqueous acetonitrile and methanol gradients containing either trifluoroacetic acid (TFA) or heptafluorobutyric acid (HFBA) as ion-pairing agents to separate such peptide pairs. TFA-containing eluents resulted in rather low resolutions, and the glycated and unglycated peptides often coeluted. HFBA increased the retention times of the unmodified peptide more than for the glycated peptide thereby improving the separation of all eight studied peptide pairs, even achieving baseline separations for some sequences. Thus the use of HFBA as ion-pair reagent provides a universally applicable eluent system in IP-RPLC to separate glycated peptides from their unmodified counterparts, even at the preparative scale required for synthetic peptides.     

气相色谱-负离子化学源质谱法分析牛奶饮品和奶粉中19种有机磷农药残留

将气相色谱-负离子化学源质谱法(GC-NCIMS)应用于牛奶饮品和奶粉中19种有机磷农药残留的同时分析。牛奶饮品和奶粉经乙腈提取剂超声提取、Florisil硅藻土和中性氧化铝双净化剂同时净化及正己烷-乙酸乙酯(体积比1∶1)混合洗脱剂洗脱后,以三苯基磷酸酯为内标物,采用GC-NCI MS的选择离子监测方式(SIM)定性与定量分析。当牛奶饮品和奶粉的加标浓度水平为20、100、500μg/kg时,平均加标回收率为64.5%~129%,相对标准偏差为2%~20%;除喹硫磷的方法检出限(MDL)为2.4μg/kg外,其余18种有机磷农药的MDL均小于1.0μg/kg;线性范围为10~500μg/kg,相关系数均大于0.9988,此分析方法成功地应用于牛奶饮品和奶粉中多种痕量有机磷农药残留的分析。