Selective detection of sulfur-containing compounds by gas chromatography/chemical reaction interface mass spectrometry

Addition of a reactant gas to a low pressure microwave-induced plasma creates a reaction interface in which complex molecules are converted into small polyatomic neutral species. For a given reactant gas the array of these small molecules reflect s the elemental composition of the original analyte. In this study HCI has been found highly effective as a reactant gas for selective detection of sulfur-eontaining compounds using capillary gas chromatography/ chernical reaction interface mass spectrometry. Detection limits as low as 30 pg of a sulfur-containing compound and a dynamic range of two orders of magnitude were achieved.     

Aldehyde analysis by high performance liquid chromatography/tandem mass spectrometry

This paper describes the development of a high performance liquid chromatography/tandem mass spectrometric (MS/MS) procedure for the specific qualitative and quantitative analysis of lipid aldehydes in biological matrices. A derivatisation method, which results in molecules that exhibit a common product ion on MS/MS, permits informative precursor ion scans, at high sensitivity. This has been applied to the examination of plasma in order to examine the production of aldehydes consequent on in vitro lipid oxidation. Quantitative analysis of target molecules using multiple reaction monitoring has been developed to permit quantitation in the same matrices.     

Analyssis of pharmaceutical substances by reaction gas chromatography/mass spectrometry

Derivatization of six pharmaceutical substances (catopril, metoclopramide, sotalol, hydrochlorothiazide, nalidixic acid, and stavudine) has been performed using five derivatizing reagents of different types; the derivatization has been followed by the GC/MS detection of the resultant products. The number of labile hydrogen atoms in the initial molecules substituted by the structural fragments of derivatizing reagents has been determined.     

Determination of the metabolites of gestrinone in human urine by high performance liquid chromatography, liquid chromatography/mass spectrometry and gas chromatography/mass spectrometry

Gestrinone was studied by high performance liquid chromatography (HPLC) for screening and by gas chromatography/mass spectrometry (GC/MS) for confirmation. When the chromatograms of blank, spiked urine and dosed urine were compared by HPLC, two unknown metabolites were found and these were excreted as the conjugated forms. Metabolites 1 and 2 were tested by LC/MS and LC/MS/MS and both had parent ions at m/z 325. The fragment ion of metabolite 1 was at m/z 263 and ions for metabolite 2 were m/z 307 [MH - H(2)O](+), 289, 279 and 241. LC/MS/MS of m/z 263 as the parent ion of metabolite 1 gave fragment ions at m/z 245 and 217, which were assumed to be [263 - H(2)O](+) and [235 - H(2)O](+), respectively. The trimethylsilyl (TMS)-enol-TMS ether derivative of gestrinone displayed three peaks in its GC/MS chromatogram, formed by tautomerism.     

Characterization of impurities in dirithromycin by liquid chromatography/ion trap mass spectrometry

With a recently developed liquid chromatographic (LC) method, using a phosphate buffer, several unknown impurities present in dirithromycin samples were separated. In this paper, a reversed-phase liquid chromatography-tandem mass spectrometry method is described for the investigation of dirithromycin and related substances. The method employed uses a Zorbax Extend C18 column (250 mm x 4.6 mm I.D.), 5 microm, and a mobile phase consisting of acetonitrile, 2-propanol, water and ammonium acetate solution pH 8.5. Mass spectral data are acquired on an LCQ ion trap mass spectrometer equipped with an electrospray ion (ESI) source operated in the positive ion mode. The LCQ is ideally suited for the identification of related substances because it provides on-line LC/MS(n) capability, which allows efficient identification without time-consuming isolation and purification procedures. Using this method, the fragmentation behavior of dirithromycin and its related substances was studied and the unknown impurities occurring in commercial samples were investigated. In total the structures of nine impurities were elucidated, among which three were different analogues with a modification in the side chain on the oxazine ring. Two impurities showed a different alkyl group in position C13. In two impurities the desosamine sugar was involved with changes in the degrees of methylation of the amino group. One unknown impurity was identified as dirithromycin F and another unknown was characterized as dirithromycin N-oxide.     

Characterization of impurities in spiramycin by liquid chromatography/ion trap mass spectrometry

A reversed-phase liquid chromatography/tandem mass spectrometry method is described for the investigation of spiramycin and related substances. The method uses an XTerra C18 column (250 x 4.6 mm i.d.), 5 microm, and a mobile phase consisting of acetonitrile, methanol, water and ammonium acetate solution, pH 6.5. Mass spectral data were acquired on an LCQ ion trap mass spectrometer equipped with atmospheric pressure chemical ionization (APCI) operated in the positive ion mode. Using this method, the fragmentation behavior of spiramycin and its related substances was studied and the unknown impurities occurring in commercial samples were investigated. In total 17 compounds were identified, among which three reported as specified impurities in the European Pharmacopoeia. The other impurities showed mainly a modification in the forosamine sugar or in the substituent at C-3 and C-6 positions. In one impurity, the mycarose sugar is absent.     

Analysis of wax ester molecular species by high performance liquid chromatography/atmospheric pressure chemical ionisation mass spectrometry

High chromatographic resolution of wax esters (WEs) was achieved by non-aqueous reversed-phase liquid chromatography on a Nova-Pak C18 column by optimising the acetonitrile/ethyl acetate mobile phase gradient. The retention behaviour of WEs was studied in this chromatographic system. The WEs eluted according to their equivalent carbon number (ECN) values; within the group of WEs with the identical ECN, the most unsaturated species tended to elute first. The isobaric WEs with different positions of the ester moiety were separated from each other whenever the lengths of the chains were sufficiently different. The methyl-branched esters eluted at shorter retention times than the straight-chained analogues, and the resolution among methyl-branched WEs depended on the position of the branching. The analytes were detected by atmospheric pressure chemical ionisation mass spectrometry (APCI-MS) using data-dependent scanning. WEs provided simple full-scan spectra with abundant protonated molecules and low-intensity fragments. Collision-induced dissociation (CID) promoted identification of the WE molecular species. The responses of WEs were found to be dependent on the number of double bonds and on the alkyl-chain length; the limits of the detection ranged from 20 μmol/L to 200 nmol/L. The HPLC/APCI-MS was applied for the analysis of the WEs isolated from honeycomb beeswax, jojoba oil and human hair. Good agreement between reported results and the literature data was achieved, with several novel polyunsaturated WEs also being found.     

Rapid identification of Mg-chelated chlorins by on-line high performance liquid chromatography/atmospheric pressure chemical ionization mass spectrometry

On-line high performance liquid chromatography/atmospheric pressure chemical ionization mass spectrometry (HPLC/APCI-MS) has been applied to the identification of a number of tetrapyrrolic pigments as well as several magnesium-free analogs. Mass spectra, acquired both in positive (+) and negative (-) ionization mode, allow not only the determination of the structural features of the pigments, but also a very easy differentiation of the Mg-chelated pigments from the free bases. In the positive ionization mode, all pigments show mainly a [M + H]+ ion and a [M + H - C20H38]+ fragment ion corresponding to the loss of the phytyl chain via a hydrogen rearrangement. In the negative ionization mode, on the other hand, although all pigments give an abundant molecular anion [M]-*, only the Mg-chelated chlorin spectra show a prominent fragment [M - C20H39]- produced by a formal loss of the phytyl radical.     

Characterization of impurities in sisomicin and netilmicin by liquid chromatography/mass spectrometry

The characterization of unknown impurities present in netilmicin and sisomicin by liquid chromatography (LC) coupled with mass spectrometry (MS) is described. The volatile ion-pairing agent trifluoroacetic acid (TFA) was used for the retention of the main compounds and their impurities on a reversed-phase (RP) C18 column, because they are highly hydrophilic and basic compounds. The method showed good separation between netilmicin and its four potential related substances prescribed in the European Pharmacopoeia, which were identified by comparison of their retention times with those of the reference substances. Furthermore, in total 16 unknown impurities in a netilmicin sample and six in a sisomicin sample with unknown identity were detected. The structures of the unknown compounds were deduced based on comparison of fragmentation patterns with those of the reference substances investigated in LC/MSn experiments by the use of electrospray ion trap mass spectrometry.     

Optimization for detection of flunarizine by high performance liquid chromatography/electrospray/mass spectrometry

This paper describes a newly developed high performance liquid chromatography/electrospray/mass spectrometry (HPLC/ES/MS) method for the determination of flunarizine (FZ) in artificial cerebrospinal fluid. The optimization for the detection of FZ in biological fluid by LC/ES/MS was investigated. The effects of solvent composition, the addition of modifier and flow rate on the detection of FZ by ES/MS were examined. The detection limit of this method (0.8 nM) proved to be much better than previously reported methods. Satisfactory accuracy (98.2–106.0%) of this newly developed method was obtained. The application of this method was demonstrated by analyzing FZ in rat microdialysis samples.     

Analysis of tetrapyrrolic pigments and derivatives in sediments by high performance liquid chromatography/atmospheric pressure chemical ionization mass spectrometry

A new application is described of the on-line high-performance liquid chromatography/positive and negative ion atmospheric pressure chemical ionization mass spectrometry (APCI(+/–)-MS) to the identification of tetrapyrrolic compounds in sediment samples containing complex mixtures of natural pigments and their diagenetic products. The method relies on the production of radical anions in order to determine the molecular masses of the molecules which yield abundant fragment ions when analyzed in the positive mode. This approach allows to verify the occurrence of coeluting components by examining their negative ion spectra and to complete their identification on the basis of their fragment ions produced in the positive ion spectra. Received: 24 September 1998 / Revised: 23 December 1998 / Accepted: 29 December 1998     

Analysis of tetrapyrrolic pigments and derivatives in sediments by high performance liquid chromatography/atmospheric pressure chemical ionization mass spectrometry

A new application is described of the on-line high-performance liquid chromatography/positive and negative ion atmospheric pressure chemical ionization mass spectrometry (APCI(+/–)-MS) to the identification of tetrapyrrolic compounds in sediment samples containing complex mixtures of natural pigments and their diagenetic products. The method relies on the production of radical anions in order to determine the molecular masses of the molecules which yield abundant fragment ions when analyzed in the positive mode. This approach allows to verify the occurrence of coeluting components by examining their negative ion spectra and to complete their identification on the basis of their fragment ions produced in the positive ion spectra. Received: 24 September 1998 / Revised: 23 December 1998 / Accepted: 29 December 1998     

Detection of sulfur-fumigated paeoniae alba radix in complex preparations by high performance liquid chromatography tandem mass spectrometry

Detection of sulfur-fumigated Paeoniae Alba Radix (PAR) in different complex preparations is challenging due to the relatively lower content of PAR and interference from more complicated components in complex preparations with different multiple constituent herbs. In this study, a high performance liquid chromatography- triple-quadrupole tandem mass spectrometry method was developed for detecting sulfur-fumigated PAR in different complex preparations. Paeoniflorin, the major component of PAR, and paeoniflorin sulfonate, the characteristic artifact transformed from paeoniflorin during sulfur-fumigation of PAR, were used as chemical markers. Multiple reaction monitoring (MRM) scan was employed to maximize sensitivity and selectivity. Through optimizing full mass scan and daughter ion scan conditions, two mass transitions were selected and employed respectively for unequivocal identification of paeoniflorin and paeoniflorin sulfonate. The detection limits for paeoniflorin and paeoniflorin sulfonate using MRM were much lower than those detected with UV 270 nm. Paeoniflorin and paeoniflorin sulfonate could be simultaneously detected in different commercial PAR-containing complex preparations without interference of other components using the established method, indicating that the newly established method was selective and sensitive enough for screening sulfur-fumigated PAR in commercial complex preparations.     

Characterization of amiodarone metabolites and impurities using liquid chromatography/atmospheric pressure chemical ionization mass spectrometry

Using the high performance liquid chromatography/atmospheric pressure chemical ionization tandem mass spectrometry (HPLC/APCI-MS/MS) technique, together with established trends from the literature, the structures of metabolites and impurities of amiodarone, an anti-arrhythmic drug, have been assigned. By comparing analyses of products of incubation with rat liver microsomes with controls in which glucose 6-phosphate dehydrogenase was omitted, metabolites could be distinguished from impurities. Structures for the two proposed metabolites and four impurities are proposed.     

Optimization of the atmospheric pressure chemical ionization liquid chromatography mass spectrometry interface

Use of optimized instrument parameters that result from statistical experimentation revealed that the sensitivity of atmospheric pressure chemical ionization (APCI) liquid chromatography-mass spectrometry (LC/MS) is greater than the sensitivity of an optimized Thermabeam? LC/MS interface by about 3 orders of magnitude, when tested on aromatic compounds. APCI is one of the few LC/MS techniques in which the chromatogram is directly comparable with liquid chromatographs that use ultraviolet detection. The optimum instrument parameters for a Finnigan SSQ-7000 APCI LC/MS interface were found at low flow rates (e. g., 0. 1 mL/min), relatively low capillary heat (e. g., 225 °C), and high sheath-gas pressure (e. g., 60 lb/in²). The optimization was achieved by monitoring the responses of sensitivity, fragmentation, and cluster ion formation. The fine tuning for high sensitivity calls for a high percentage of water in the mobile phase. In contrast, a high percentage of organic content in the mobile phase is required to obtain abundant protonated molecular ions with respect to fragmentation and clustering. This is an important consideration for analyses of unknowns.     

32种氧化型染料的高效液相色谱定量及高效液相色谱-串联质谱确证方法北大核心CSCD

染发类产品中氧化型染料种类多,实际样品测定时干扰多,建立染发类产品中多种常用染料的测定方法,为该类产品的有效监管提供技术手段十分必要。该研究根据染料使用频率分组,采用能够屏蔽硅羟基和金属离子影响的C_(18)柱,优化了《化妆品安全技术规范》(2015年版)中32种染料的高效液相色谱法(HPLC)并建立了高效液相色谱-串联质谱(HPLC-MS/MS)确证方法。样品以10 g/L亚硫酸氢钠水溶液为抗氧化剂,用无水乙醇-水(1∶1,v/v)混合溶液冰浴超声提取10 min。HPLC方法采用甲醇、乙腈和磷酸盐缓冲液为流动相分两个液相色谱条件进行梯度洗脱分离,于280 nm波长下检测,其中一个HPLC条件中的相互干扰组分均在另一个HPLC条件下完全分离,避免了实际样品检测时组分间的干扰,并排除了32种以外的其他15种常用染料的干扰。HPLC-MS/MS方法分别采用5 mmol/L乙酸铵水溶液-乙腈和5 mmol/L乙酸水溶液-乙腈为正离子和负离子模式下的流动相,电喷雾离子模式下用多反应监测(MRM)模式进行定性和定量分析。HPLC和HPLC-MS/MS两个方法中,日内精密度和48 h内稳定性的相对标准偏差(RSD)<10%,回收率为82.6%~114.9%(RSD<10%)。HPLC方法中32种染料在大约10~500 mg/L范围内线性关系良好(r^(2)>0.99),检出限为9.7~40.1μg/g;HPLC-MS/MS方法中氢醌线性范围为2.0~79.7 mg/L,检出限为8.0μg/g,其他组分线性范围约为0.1~4 mg/L,检出限为0.01~0.4μg/g。采用HPLC、HPLC-MS/MS两个方法和《化妆品安全技术规范》方法同时测定实际样品,共检出16种染料,检出含量范围为58~25160μg/g。3个方法检测结果的RSD为1.9%~10.1%。该研究增加了HPLC-MS/MS确证方法,适应化妆品法定检验中的未知物确认程序;方法简便快速,结果准确,专属性强,具有较好的通用性和可操作性。     

高效液相色谱-串联质谱法分离鉴定单唾液酸四己糖神经节苷脂中的杂质

用高效液相色谱法（HPLC）分析了单唾液酸四己糖神经节苷脂(GM1)药物的冻干粉、中间体和注射液各6个批号的样品,以期查找出采用不同工艺生产的成品中造成临床副反应的可能杂质。在用HPLC对多个批号GM1成药的对比分析中,发现某个批号的GM1干粉中多出2个杂质峰,其保留时间与制作该批号的GM1中间体的2个杂质峰保留值相同。对该批号的GM1干粉和相应批号的GM1中间体中的目标杂质进行半制备级收集,经冷冻干燥除溶剂富集35倍后,用电喷雾-四极杆-飞行时间质谱（ESI-Q-TOF MS）定性分析,对主分子离子峰进行了二级质谱分析。经谱图解析后,推断在GM1干粉和中间体中存在的保留值相同的杂质可能是同种组分。两个杂质峰的结构皆为岩藻糖(Fuc)-GM1,仅是神经酰胺上的长链基团有所不同,峰1的该基团由16个CH2组成,而峰2的该基团由18个CH2组成。临床数据表明含有上述两种杂质的2批GM1注射液都有副反应,而没有上述杂质的4批GM1注射液都没有临床副反应,而且这两批有临床副反应的GM1注射液都是用同一个批号的含有这两种杂质的中间体制成的,因此推断上述两个杂质可能是引起副反应的主要组分。     

Investigation of amodiaquine bulk drug impurities by liquid chromatography/ion trap mass spectrometry

Three unknown impurities in an amodiaquine bulk drug sample were detected by reversed-phase high-performance liquid chromatography with ultraviolet detection (HPLC/UV). A liquid chromatography/tandem mass spectrometry (LC/MS(n)) method is described for the investigation of these impurities. Mass spectral data were acquired on an LCQ ion trap mass analyzer equipped with an electrospray ionization (ESI) source operated in positive ion mode. The fragmentation behavior of amodiaquine and its impurities has been studied. Based on the mass spectral data and the specifics of the synthetic route, the possible structures of these impurities were elucidated as 4-[(5-chloroquinolin-4-yl)amino]-2-(diethylaminomethyl)phenol (impurity I), 4-[(7-chloroquinolin-4-yl)-amino]phenol (impurity II) and 4-[(7-chloroquinolin-4-yl)amino]-2-(diethylaminomethyl)-N(1)-oxy]phenol (impurity III). The structures were confirmed by their independent synthesis and NMR spectral assignment.     

Quantification of human pharmaceuticals in water samples by high performance liquid chromatography-tandem mass spectrometry

An improved analytical method for determination of human pharmaceuticals in natural and wastewaters with ng L⁻¹ sensitivity is presented. The method is applicable to pharmaceuticals from a wide range of therapeutic classes including antibiotics, analgesics, anti-inflammatories and anti-cancer compounds. Pharmaceuticals were extracted from waters using solid-phase extraction, and after concentration, analysed by high performance liquid chromatography with tandem mass spectrometric detection (HPLC-MS/MS). Identification of each compound was secured using retention time and by the selected reaction monitoring of two transitions, one of which was additionally used for quantification. Limits of detection ranged from 0.03 to 0.96 ng L⁻¹ and were up to two orders of magnitude lower than those of previously published methods. The method was validated using spiked samples prepared from tap, river and sea water as well as wastewater effluents, collected from the North of Scotland. Analysis of wastewater effluents revealed the presence of mefenamic acid, ibuprofen, erythromycin, diclofenac and trimethoprim. None of the selected pharmaceuticals were detected in river, tap or sea water samples.