Evaluation of low-pressure gas chromatography linked to ion-trap tandem mass spectrometry for the fast trace analysis of multiclass pesticide residues

A rapid multiresidue method for the analysis of 72 pesticides has been developed using a single injection with low-pressure gas chromatography/tandem mass spectrometry (LP-GC/MS/MS). The LP-GC/MS/MS method used a short capillary column of 10 m x 0.53 mm i.d. x 0.25 microm film thickness coupled with a 0.6 m x 0.10 mm i.d. restriction at the inlet end. Optimal LP-GC conditions were determined which achieved the fastest separation in MS/MS detection mode. Also MS/MS conditions were optimized in order to increase sensitivity and selectivity. The analytical parameters of the LP-GC/MS/MS method were compared with those obtained by GC/MS/MS using a conventional capillary column (30 m x 0.25 mm i.d. x 0.25 microm film thickness). Better precision and sensitivity values were obtained with the LP-GC/MS/MS approach. The limits of detection (LOD) of the compounds ranged from 0.1 to 14.1 microg L(-1) for LP-GC/MS/MS, lower than those obtained for conventional GC/MS/MS that ranged from 0.1 to 17.5 microg L(-1). The peak widths obtained with the short column in LP-GC are similar to those obtained using conventional capillary GC columns, and the peaks can be successfully identified by MS/MS detection with the conventional scan speed of ion-trap instruments. In addition, the analysis time was significantly reduced with LP-GC/MS/MS (32 min) versus GC/MS/MS (72 min), allowing the number of samples analyzed per day in a routine laboratory to be doubled.     

Analytical study of comprehensive and targeted multidimensional gas chromatography incorporating modulated cryogenic trapping

This paper reports the results of an analytical study comparing capillary gas chromatography (GC) operated in the normal mode with 2 new GC techniques, comprehensive GC (GC x GC) and targeted (or selective) multidimensional GC, which use a longitudinally modulated cryogenic system (LMCS), recently developed in our laboratory. A high-temperature application of derivatized sterols, of interest in fecal pollution monitoring, was chosen for this work. A directly connected coupled-column ensemble was used, comprising a nonpolar column and a moderately polar column. With LMCS, effluent from the first column is zone-compressed in a cryogenic trap and then pulsed to a short second column, producing narrower peaks with sharp, tall peak responses at the detector. The modulator is operated at a constant frequency, e.g., 0.25 s(-1), to produce the GC x GC result, or is moved in a predefined manner so that whole peaks are selectively trapped and subsequently pulsed through to the second column in the targeted mode. Standard solutions containing a mixture of 7 sterols and 5-alpha-cholestane internal standard were used. Detection sensitivity is increased by a factor of >25 with the use of LMCS. The estimated limit of detection was about 0.1 microg/mL when normal GC with flame ionization detection (GC/FID) and a 1.0 microL splitless injection volume were used, compared with 0.02 and 0.004 microg/mL for the LMCS operated in GC x GC and selective modes, respectively. Calibration curves for GC/FID were linear over the 0.1-2.0 microg/mL range tested. Reproducibilities for the GC x GC and normal GC modes were comparable; generally, relative standard deviations (RSD) were on the order of 3-4%, based on raw peak responses. Improved reproducibility was found for selective LMCS operation, at an RSD of around 2%; with internal standardization, better results were achieved. The coupled-column arrangement allowed complete separation of sterol peaks from overlapping impurity peaks in a number of instances with LMCS modes, and its use should improve data quality over that of normal GC operation, in which the overlapping peaks interfere with measurement of peak response in the normal mode.     

Studies of structural alterations of humic acids from conifer bark residue during composting by pyrolysis-gas chromatography/mass spectrometry using tetramethylammonium hydroxide (TMAH-py-GC/MS)

Pyrolysis-gas chromatography/mass spectrometry using tetramethylammonium hydroxide (TMAH-py-GC/MS) was used to characterize the humic acids (HAs) produced during the composting of conifer bark. The syringyl to guaiacyl ratios of HAs during composting were estimated from the peak area ratios for 3,4,5-trimethoxy to 3,4-dimethoxy benzene derivatives (0.11–0.50), which are characteristic of conifer species. The peak areas for nitrogen-containing and fatty acid pyrolysate compounds increased significantly during composting, indicating the degree of humification during composting. HA samples from the bark composts contained higher levels of diterpene resin acids, monoterpenes and sesquiterpenes. To investigate the species of terpenes, the HA was extracted with ethanol, and the components of the extract classified into α-HA and hymatomelanic acid (HMA) fractions, respectively. The peak areas for terpenes in the α-HA fraction were much smaller than those in the original HA, indicating that the majority of terpenes were extracted into the HMA fraction. If terpenes were to bind to HMA via unspecified interactions, no peaks would be apparent for the direct injection of HMA in ethanol into the GC/MS without pyrolysis. A comparison of the total ion chromatograms of HMA for the TMAH-py-GC/MS and GC/MS revealed that terpenes in the HA had been incorporated into polymeric structures of HMA. These results indicate that terpenes are transferred from the raw bark and incorporated into HA fractions during the composting processes.     

Comprehensive Two-Dimensional Gas Chromatography with Mass Spectrometric Detection (GC × GC/MS) Applied to the Analysis of Petroleum

Comprehensive two-dimensional gas chromatography coupled with mass spectrometric detection (GC × GC/MS) is a three-dimensional analytical method. In its application to petroleum analysis, the high peak capacity of GC × GC produced chromatographic resolution of over 750 peaks from a marine diesel fuel. The MS detector provided a full-scan mass spectrum for each resolved peak. The integration of an MS detector with GC × GC provides increased capability to identify minor components, determine members of homologous series, and characterize ordered peak patterns of related components that are visible in the GC × GC chromatogram.     

Comprehensive two-dimensional gas chromatography/mass spectrometric analysis of pepper volatiles

The headspace compositions of 13 pepper and peppercorn samples of different species, colloquially also referred to as pepper, were analyzed, and more than 300 compounds were tentatively characterized by means of comprehensive two-dimensional gas chromatography in tandem with flame ionization detection, quadrupole mass spectrometric detection and time-of-flight mass spectrometric detection (GC x GC-FID, GC x GC/qMS and GC x GC/TOFMS, respectively). The analysis of volatile organic compounds (VOCs) was performed after solid-phase microextraction (SPME) using a 75-microm PDMS/DVB fibre. Fingerprint comparison between the three techniques permitted peaks to be assigned in the GC x GC-FID experiment based on the analogous MS analysis, taking into account retention shifts arising from method variations. When using GC x GC/TOFMS, about five times more peaks were identified than in GC x GC/qMS. Retention indices for all peaks were calculated in the bi-dimensional column set comprising of a 5% phenyl polysilphenylene-siloxane primary column and a polyethylene glycol second column. The spectra obtained by both mass detection techniques (qMS and TOFMS) give very similar results when spectral library searching was performed. The majority of the identified compounds eluted as pure components as a result of high-resolution GC x GC separations, which significantly reduces co-elution, and therefore increases the likelihood that pure spectra can be obtained. The differences between TOFMS and qMS (in fast scanning mode) spectra were generally small. Whilst spectral quality and relative ion ratios across a narrow peak (e.g. w(b) approximately 100-150 ms) do vary more for the fast peaks obtained in GC x GC/qMS operation, than with TOFMS, in general adequate spectral matching with the library can be achieved.     

衍生-气相色谱-质谱法测定水中痕量雌激素

提出了气相色谱-质谱法测定水中雌二醇、雌酮、雌三醇、戊酸雌二醇、己烯雌酚、乙炔雌二醇、双酚A和壬基酚等8种雌激素含量的方法。样品经乙酸乙酯提取和HLB小柱净化后,所得净化液中的雌激素与三甲基硅基化剂(TMS)或七氟丁酸酐(HFBA)进行衍生化反应产物用正己烷定容。在气相色谱分离中用DB-5MS毛细管柱为固定相,在质谱分析中采用全扫描和选择离子监测模式。8种雌激素的峰面积与质量浓度在20.0～1 000μg.L-1范围内呈线性关系,检出限(3S/N)在0.1～0.5μg.L-1之间。方法用于水中雌激素的测定,回收率在71%～103%之间,相对标准偏差(n=6)在4.2%～15%之间。     

Molecular structure of tris(dipivaloylmethanato)lutetium(iii) studied by gas electron diffraction and ab initio and DFT calculations

Combined gas electron diffraction/mass spectrometry (GED/MS) was used to determine the molecular structure of tris(dipivaloylmethanato)lutetium(III), Lu(dpm)(3)(dpm = 2,2,6,6-tetramethyl-heptane-3,5-dionato). Up to about 520-570 K the vapour consisted only of molecules Lu(dpm)(3). The experimental data recorded at 408(5) K indicate that the molecules have D(3) symmetry. The bond distances (r(h1)) in the chelate ring are Lu-O 2.197(6) Angstrom, C-O 1.270(4) Angstrom and C-C 1.390(6) Angstrom . Theoretical computations at the HF and DFT levels with basis sets up to 6-311G* afford structures similar to those found experimentally, with a distorted LuO(6) antiprism.     

Effects of pressure drop on absolute retention matching in comprehensive two-dimensional gas chromatography

Comprehensive two-dimensional gas chromatography (GC x GC) analysis has the capability to resolve many more components of complex mixtures than traditional single column GC analysis. There is an increasing need to provide reliable identification of these separated components; time-of-flight mass spectrometry (TOFMS) is the most appropriate technology to achieve this task. Rather than require MS for all GC x GC separations, it is desirable to assign peak identities to specific peak positions in the GC x GC separation space, and this necessitates matching peak retentions in the two experiments - GC x GC-FID and GC x GC-TOFMS. The atmospheric vs. vacuum outlet conditions confound this task. It is shown here that by employing a supplementary gas supply, provided to a T-union between the column outlet and the MS interface, it is possible to generate 2D chromatograms for GC x GC-FID and GC x GC-TOFMS that are essentially exactly matched. There is no degradation in separation performance or efficiency in the second column in the system interfaced to the T-union. Since the GC x GC-FID experiment uses hydrogen for maximum efficiency, and GC x GC-TOFMS uses helium carrier, translation of (conditions/retentions) must account for the different viscosities of the carrier gases. Translation of conditions is based on well-known principles established in single column analysis. Tabulated data illustrate that retention reproducibility was of the order of better than 4 s for the average first dimension retention difference, and about 40 ms for the average second dimension retention difference when comparing GC x GC-FID and GC x GC-TOFMS results. This should provide considerable support for identification in routine GC x GC-FID analysis of specific sample types, once the peaks in 2D separation space have been assigned identities through GC x GC-TOFMS analysis.     

白音华褐煤可溶有机质的组成和结构特征

依次采用石油醚、环己烷、二硫化碳、丙酮、甲醇和等体积的丙酮/二硫化碳混合溶剂对白音华褐煤(BL)进行分级萃取得到萃取物(E_1-E_6),利用甲醇、甲苯和等体积的甲醇/甲苯混合溶剂对萃取残渣进行连续热溶得到热溶物(SP_1-SP_3)。利用傅里叶变换红外光谱(FT-IR)、气相色谱质谱(GC/MS)和实时直接分析-质谱(DART-MS)对萃取物和热溶物的组成和结构特征进行了分析。BL总的萃取物产率和热溶物产率分别为9.37%和21.84%。E_5和E_6的FT-IR谱图中有较强的羟基吸收峰,而E_1的FT-IR谱图中脂肪C-H的伸缩振动峰强度明显高于其他萃取物;三种溶剂热溶物的FT-IR谱图相似,但SP_1和SP_3的FT-IR谱图中羟基吸收峰较强。E_1和E_5中GC/MS可检测化合物分别以烷烃和芳烃为主,E_5中还含有较多的含氧化合物;三种热溶物中化合物均以烷烃和芳烃为主,SP_3中酚类、酮类和酯类等含氧化合物的含量较高。DART-MS可检测出萃取物和热溶物中GC/MS无法检测出的较强极性和难挥发化合物;热溶物中含量较高的化合物的碳数和等价双键数(Double bond equivalent,DBE)分别集中分布在10-25和2-16,并且DBE随碳数增加而增加。     

搅拌棒吸附子萃取与GC-MS法测定水中20种有机氯农药

建立了搅拌棒吸附子萃取/气相色谱-质谱法(SBSE/GC-MS)同时检测水中α-六六六、γ-六六六、β-六六六、七氯、δ-六六六、艾氏剂、环氧七氯、γ-氯丹、顺-氯丹、硫丹Ⅰ、p,p-滴滴伊、狄氏剂、异狄氏剂、p,p-滴滴滴、硫丹Ⅱ、p,p-滴滴涕、异狄氏剂醛、硫丹硫酸盐、甲氧滴滴涕、异狄氏剂酮20种有机氯农药含量的方法.样品在室温下经拌棒吸附子搅拌吸附,甲醇解吸附后,以J&W DB-35 MS(30 m×0.25 mm×0.25 μm)石英毛细管色谱柱为分析柱,气相色谱-质谱选择离子流模式检测.考察了萃取时间、氯化钠及甲醇加入量等对萃取的影响.实验结果表明:在2.5 ～20.0 μg/L 范围内,20种有机氯农药呈良好的线性关系,检出限(S/N=3)为0.008 ～0.118 μg/L,水样中分别添加2.5、20 μg/L的20种有机氯农药,回收率为 52% ～117%,相对标准偏差小于13%(n= 6).该方法操作简便、快速、灵敏度高,应用于实际样品检测,结果满意.     

Analysis of MS/MS fragmentation of taxoids

The fragmentation pathways of seven types of taxoids were investigated by using a LC-MS/MS method, namely: (1) neutral taxoids with a C-4(20) double bond; (2) taxoids with a C-4(20) double bond and oxygenation at C-14; (3) 5-cinnamoyl taxoids with a C-4(20) double bond; (4) a basic taxoid with a C-4(20) double bond; (5) a taxoid with a C-4(20) epoxide; (6) taxoids with an oxetane ring; and (7) taxoids with an oxetane ring and a phenylisoserine C-13 side chain. Depending on the class of core structure and the substitution pattern, each taxoid gave either the molecular adduct ion [M+NH4]+ or [M+H]+. In the MS/MS, the molecular adduct ion gave characteristic product ions corresponding to the loss of water, acetic acid, benzoic acid, and cinnamic acid or the phenylisoserine group. These could reflect the difference of the substitutions and structural modifications and should be utilized for the structure elucidation oftaxoids by LC-MS.     

AsS2Cl-an Arsenic(V) compound? Formation, stability and structure of gaseous AsSCl and AsS2Cl--a combined experimental and theoretical study

By reaction of solid As(4)S(4) with gaseous Cl(2) at a temperature of 410 K gaseous AsSCl and AsS(2)Cl are formed. Unexpectedly in AsS(2)Cl the arsenic is not of formal oxidation state +V but +III: the molecular structure of AsS(2)Cl is arranged as a 1-chloro-dithia-arsirane and comprises an hitherto unknown AsS(2) three-membered ring. Thermodynamic data on AsSCl and AsS(2)Cl are obtained by mass spectrometry (MS). The experimental data are extended and confirmed by ab initio quantum chemical calculations (QC). The following values are given: Δ(f)H(0)(298)(AsSCl) = -5.2 kJ mol(-1) (MS), Δ(f)H(0)(298)(AsSCl) = 1.7 kJ mol(-1) (QC), S(0)(298)(AsSCl) = 296.9 J K(-1) mol(-1) (QC) and c(p)(0)(T)(AsSCl) = 55.77 + 3.97 × 10(-3)T- 4.38 × 10(5)T(-2)- 1.83 × 10(-6)T(2) and Δ(f)H(0)(298)(AsS(2)Cl) = -39.0 kJ mol(-1) (MS), Δ(f)H(0)(298)(AsS(2)Cl) = -20.2 kJ mol(-1) (QC), S(0)(298)(AsS(2)Cl) = 321.3 J K(-1) mol(-1) (QC) and c(p)(0)(T)(AsS(2)Cl) = 80.05 + 5.09 × 10(-3)T- 7.61 × 10(5)T(-2)- 2.35 × 10(-6)T(2) (298.15 K < T < 1000 K) (QC). The ionization energies are determined (IP(AsSCl) = 10.5, IP(AsS(2)Cl) = 10.2 eV). The IR spectrum of AsSCl is detected by means of matrix isolation spectroscopy. The estimated force constant f(As=S) = 4.47 mdyn·?(-1) gives rise to an As=S double bond.     

Characterization of synthetic nucleic acids by electrospray ionization quadrupole time-of-flight mass spectrometry

The potential of electrospray ionization quadrupole-quadrupole-time-of-flight mass spectrometry (ESI-QqTOF-MS) for the characterization of synthetic nucleic acids was evaluated. Oligonucleotides ranging in size from 12 up to 51 nucleotides were analyzed via direct infusion MS as well as via liquid chromatography (LC) online hyphenated to MS. These experiments proved the outstanding mass spectrometric performance of the TOF mass analyzer in regard of accuracy, reproducibility, resolution, and sensitivity. During a 1-min run, the monoisotopic mass of (dT)(24) was measured with a maximum relative mass deviation of 7.64 ppm proving the high mass accuracy of the TOF analyzer. Over a period of 1 h, mean deviations were determined in the range between -3.58 ppm and 3.06 ppm demonstrating the high stability of the applied external calibration. The molecular mass of a 51-mer was measured with a deviation smaller than 3.23 ppm from the theoretical value. The resolution exceeded a value of m/Deltam = 20 000 (m is the measured mass and Deltam the full peak width at half-maximum), which enabled the separation of the isotopic peaks of all investigated oligonucleotides. Because of the outstanding transmission and detection efficiency of the TOF mass analyzer, detection limits in the amol/microl to low fmol/microl range were reached. The usability of LC-ESI-QqTOF-MS for the qualitative and quantitative analysis of synthetic oligonucleotide mixtures was demonstrated.     

杂多酸催化裂解松香产物中挥发油成分分析

杂多酸（ＨＰＡ）催化松香裂解的产物为油状物,本文利用气相色谱／质谱（ＧＣ／ＭＳ）联用技术对该产物的挥发组分进行了分析,共分离出１７７个峰,通过与数据库标准图谱对照鉴定出绝大部分组分。其中有２８种组分含量较高,占挥发成分总含量的５１．５２％,主要为松香裂解产生的Ｃ６～Ｃ２０的烯烃、芳香烃及酮类。     

液-液萃取富集-气相色谱法测定水中有机氯农药和多氯联苯

采用正己烷作萃取溶剂提取并富集水样中有机氯农药(OCP's)和多氯联苯(PCB's),所得提取液经浓缩至约0.5mL并定容至1.0mL后,用气相色谱法-电子捕获检测器测定水中有机氯农药和多氯联苯。采用Rtx-5MS和Rtx-1701双柱法根据与标准物质的保留时间相对比进行定性分析;采用Rtx-5MS柱对被测组分按外标法进行定量分析。结果表明:各种农药质量浓度均在0.5～40μg·L~(-1)范围内与峰面积呈线性关系。有机氯农药和多氯联苯的检出限(3s)在0.001 1～0.004 7μg·L~(-1)之间。用标准加入法测得其回收率在83.3%～112.1%之间,相对标准偏差(n=7)在4.4%～9.4%之间。     

Temperature-sensitive resolution of cis- and trans-fatty acid isomers of partially hydrogenated vegetable oils on SP-2560 and CP-Sil 88 capillary columns

This study examines the effect of the column operating temperature of 100 m SP-2560 and CP-Sil 88 capillary gas chromatographic (GC) columns on the separation of cis- and trans-octadecenoic (18:1) isomers in partially hydrogenated vegetable oils. The overlapping GC peaks were measured at column isothermal temperatures of 170, 175, 180, 185, and 190 degrees C. With both columns, isothermal operation at 180 degrees C produced the fewest overlapping peaks of the cis and trans isomers. At this temperature, all trans-18:1 isomers, except 13t-18:1 (t = trans), 14t-18:1, and 15t-18:1 isomers were resolved from the cis-18:1 isomers. The peaks of the 13t-18:1 and 14t-18:1 isomer pair, which always elute together, overlapped peaks of the 6c-18:1 (c = cis), 7c-18:1, and 8c-18:1 isomers; the peak of the 15t-18:1 isomer overlapped the major cis-18:1 peak, which was mainly due to 9c-18:1. Isothermal operations above or below 180 degrees C produced some additional overlapping problems. At 185 and 190 degrees C, the peaks of the 16t-18:1 and 13c-18:1 isomers overlapped. At 175 and 170 degrees C, the 16t-18:1 peak overlapped the 14c-18:1 peak, and the peaks of the 13t + 14t-18:1 isomer pair partially overlapped the major cis-18:1 peak. The separation of 11c-20:1 and alpha-linolenic acid and its geometric isomers was also affected by the column operating temperature. Isothermal operation of the SP-2560 column at 180 degrees C produced a baseline separation of 11c-20:1 and alpha-linolenic acid and its geometric isomers, whereas with the CP-Sil 88 column the best resolution was obtained at 170 degrees C. The results of this study show that the SP-2560 capillary column has a slight advantage over the CP-Sil 88 column for the simultaneous resolution of all the fatty acids generally found in partially hydrogenated vegetable oils.     

Full-range analysis of ambient volatile organic compounds by a new trapping method and gas chromatography/mass spectrometry

This study investigated the feasibility of analyzing a full range of ambient volatile organic compounds (VOCs) from C(3) to C(12) using gas chromatograph mass spectrometry (GC/MS) coupled with thermal desorption. Two columns were used: a PLOT column separated compounds lighter than C(6) and a DB-1 column separated C(6)-C(12) compounds. An innovative heart-cut technique based on the Deans switch was configured to combine the two column outflows at the ends of the columns before entering the MS. To prevent the resolved peaks from re-converging after combining, two techniques were attempted (hold-up vs. back-flush) to achieve the intended "delayed" elution of heavier components. Thus, the resulting chromatogram covering the full range of VOCs is a combination of two separate elutions, with the heavier section following the lighter section. With the hold-up method, band-broadening inevitably occurred for the delayed C(6)-C(7) DB-1 compounds while the light compounds eluted from the PLOT column. This broadening problem resulted in peak tailing that was largely alleviated by adding a re-focusing stage while the DB-1 compounds were back-flushed, and this modified technique is referred to as the back-flush method. With this modification, the separation of the C(6)-C(7) compounds improved dramatically, as revealed by the decrease in peak asymmetry (As) and increase in resolution. Linearity and precision for these peaks also improved, yielding R(2) and RSD values better than 0.9990 and 2.8%, respectively.     

Metabonomics investigation of human urine after ingestion of green tea with gas chromatography/mass spectrometry, liquid chromatography/mass spectrometry and (1)H NMR spectroscopy

A method using gas chromatography/mass spectrometry (GC/MS), liquid chromatography/mass spectrometry (LC/MS) and (1)H NMR with pattern recognition tools such as principle components analysis (PCA) was used to study the human urinary metabolic profiles after the intake of green tea. From the normalized peak areas obtained from GC/MS and LC/MS and peak heights from (1)H NMR, statistical analyses were used in the identification of potential biomarkers. Metabolic profiling by GC/MS provided a different set of quantitative signatures of metabolites that can be used to characterize the molecular changes in human urine samples. A comparison of normalized metabonomics data for selected metabolites in human urine samples in the presence of potential overlapping peaks after tea ingestion from LC/MS and (1)H NMR showed the reliability of the current approach and method of normalization. The close agreements of LC/MS with (1)H NMR data showed that the effects of ion suppression in LC/MS for early eluting metabolites were not significant. Concurrently, the specificity of detecting the stated metabolites by (1)H NMR and LC/MS was demonstrated. Our data showed that a number of metabolites involved in glucose metabolism, citric acid cycle and amino acid metabolism were affected immediately after the intake of green tea. The proposed approach provided a more comprehensive picture of the metabolic changes after intake of green tea in human urine. The multiple analytical approach together with pattern recognition tools is a useful platform to study metabolic profiles after ingestion of botanicals and medicinal plants.     

Development of two‐dimensional gas chromatography (GC×GC) coupled with Orbitrap‐technology‐based mass spectrometry: Interest in the identification of biofuel composition

Comprehensive gas chromatography (GC) has emerged in recent years as the technique of choice for the analysis of volatile and semivolatile compounds in complex matrices. Coupling it with high‐resolution mass spectrometry (MS) makes a powerful tool for identification and quantification of organic compounds. The results obtained in this study showed a significant improvement by using GC×GC‐EI‐MS in comparison with GC‐EI‐MS; the separation of chromatogram peaks was highly improved, which facilitated detection and identification. However, the limitation of Orbitrap mass analyzer compared with time‐of‐flight analyzer is the data acquisition rate; the frequency average was about 25 Hz at a mass resolving power of 15.000, which is barely sufficient for the proper reconstruction of the narrowest chromatographic peaks. On the other hand, the different spectra obtained in this study showed an average mass accuracy of about 1 ppm. Within this average mass accuracy, some reasonable elemental compositions can be proposed and combined with characteristic fragment ions, and the molecules can be identified with precision. At a mass resolving power of 7.500, the scan rate reaches 43 Hz and the GC×GC‐MS peaks can be represented by more than 10 data points, which should be sufficient for quantification. The GC×GC‐MS was also applied to analyze a cellulose bio‐oil sample. Following this, a highly resolved chromatogram was obtained, allowing EI mass spectra containing molecular and fragment ions of many distinct molecules present in the sample to be identified.     

Original GC–FID Determination of Non-Chromophoric Impurities in Quetiapine: An Antipsychotic Drug

A rapid and sensitive gas chromatographic method using flame ionization detection (GC–FID) has been developed and validated for five process related non-chromophoric impurities viz, 2-(2-chloroethoxy)ethanol (2-CEE), piperazine, 2-(piperazin-1-yl)ethanol (HEP), 2-[2-(piperazin-1-yl)ethoxy]ethanol (HEEP), 2,2-[piperazine-1,4-diylbis(ethane-2,1-diyloxy)]diethanol (DEEP) observed during the process development of quetiapine hemifumarate, an antipsychotic drug is presented. All five non-chromophoric impurities ranging from 0.05 to 0.1% were detected using DB-5 (30 m × 0.53 mm, 5 μm) column with a good peak separation. The method was fully validated according to the ICH Q2 (R1) guidelines. The investigated validation protocols showed that the method has acceptable specificity, accuracy, linearity, precision, robustness and high sensitivity with detection limits and quantitation limits ranging from 0.001 to 0.01% and 0.004 to 0.03%, respectively. These non-chromophoric impurities generated during the process were identified by GC–MS and are characterized by MS, ¹H NMR and FT-IR spectroscopy.