Characterization of copolymers by high performance liquid chromatography

Size exclusion chromatography (SEC) is capable of evaluating the molecular weight distribution (MWD) of a sample. Information about the chemical composition distribution can be gained by gradient high performance liquid chromatography (gradient HPLC), where a poor starting eluent is, in the course of the separation, substituted by another one of increasing elution strength. Both normal-phase and reversed-phase systems can be employed. The combination of SEC and gradient HPLC enables chromatographic cross-fractionation to be performed efficiently.     

Fast high performance liquid chromatography and ultraviolet-visible quantification of principal phenolic antioxidants in fresh rosemary

An improved HPLC method is reported for the determination of rosemary's principal phenolic antioxidants, rosmarinic and carnosic acids, providing a fast and simultaneous determination for both of them by using a solid phase column. The analysis was performed with fresh methanolic extractions of Rosmarinus officinalis. To quantify the amount of antioxidants in a fast and reproducible way by means of UV-vis absorption measurements, a spectrophotometric multi-wavelength calibration curve was constructed based on the antioxidant contents obtained with the recently developed HPLC method. This UV-vis methodology can be extended to the determination of other compounds and herbs if the restrictions mentioned in the text are respected.     

Analysis of 'ARN' naphthenic acids by high temperature gas chromatography and high performance liquid chromatography

Examination by high temperature GC (HTGC) of the methyl esters of the so-called 'ARN' naphthenic acids from crude oils of North Sea UK, Norwegian Sea and West African oilfields revealed the distributions of resolved 4-8 ring C80 tetra acids and trace amounts of other acids. Whilst all three oils contained apparently the same major acids, the proportions of each differed, possibly reflecting the growth temperatures of the archaebacteria from which the acids are assumed to have originated. The structures of the 4, 5, 7 and 8 ring acids are tentatively assigned by comparison with the known 6 ring acid and related natural products and an HPLC method for the isolation of the individual acids is described. ESI-MS of individual acids isolated by preparative HPLC established the elution order of the 4-8 ring acids on the HPLC and HTGC systems and revealed the presence of previously unreported acids tentatively identified as C81 and C82 7 and 8 ring analogues.     

Characterization of high performance glass capillary gas chromatography

Summary High resolution gas chromatography requires the highest performance characteristics of gas chromatographic systems in terms of sampling and sample handling in strumentation, columns, and data handling. This paoper describes high precision computer measurements for characterizing capillary column efficiencies which are within 75% of the theoretical limit of capillary GC. Particular emphasis is given to detailed peak shape analysis, measurement accuracy and reproducibility, and system stability. Using known instrument performance parameters, it is then possible to characterize column performance with high accuracy in a meaningful manner. It is proposed that wall-coated tubular columns be characterized in terms of their chromatographic performance by the following parameters: Trennzahl (separation number), number of theoretical plates/meter, program temperature beseline stability, acid-base ratio, and the coefficient of skewness for 1-octanol. Statistical moments (m2) and hybrid moments are used to describe capillary column chromatographic performance because they may be related to basic physico-chemical column processes. These measurements are very sensitive parameters for characterizing GC columns. Using an online computer-based data system, the limits of capillary GC are shown to be limited by the sampling and injection steps.     

Determination of triazine herbicides in surface and drinking waters by off-line combination of liquid chromatography and gas chromatography-mass spectrometry

Summary Mass spectra of 12 triazines were obtained by electron impact (EI), positive-ion chemical ionization (PCI) and negative-ion chemical ionization (NCI) using methane and isobutane as reagent gases. EI mass spectrometry is more sensitive than PCI and NCI, although the chemical ionization modes increase selectivity markedly. A pre-column packed with polymer stationary phase was employed to preconcentrate surface and drinking water samples. After desorption of the analytes with ethyl acetate, an aliquot was injected directly into the GC-MS system. Atrazine and simizine were found in these samples at 10–80 ppt levels. The limits of detection for both herbicides were below 10 ppt in drinking water.     

Determination of cortisol in guinea pig urine by high performance thin-layer chromatography, high performance liquid chromatography, and thin-layer chromatography/radioimmunoassay

Summary In order to collect urinary samples from unrestrained guinea pigs, animals were kept in their familiar home cages with wood shavings for bedding. Cortisol was removed from shavings by a simple washing step, and an attempt was made to measure its concentrations by high performance thin-layer chromatography (HPTLC), high performance liquid chromatography (HPLC), or thin layer chromatography/radioimmunoassay (TLC-RIA). After intramuscular administration of 25 mg cortisol, cortisol excretion increased from about 20–30 μg/day to 400–500 μg/day (HPTLC: 531 μg/day, HPLC: 493 μg/day; TLC-RIA: 394 μg/day). Similarly, the treatment of the animals with 20 IU ACTH resulted in an augmented cortisol excretion, with mean values of 294 μg/day (HPTLC), 256 μg/day (HPLC) and 143 μg/day (TLC-RIA), respectively. The present study shows, for the first time, that cortisol excretion in unrestrained laboratory animals can be determined. Whilst the cortisol values measured by HPTLC and HPLC agree, the amounts measured by TLC-RIA were significantly lower. These differences are probably due to the presence of substances in urine or shavings which interfere with the radioimmunological determination. Hence, cortisol should be determined either by HPTLC or HPLC. Beside having a desirable specificity, these methods are more suited than TLC/RIA for steroid analysis since they confer the possibility of measuring additional steroids (e.g. precursors and/or metabolites of cortisol) in a single urine extract. This is especially the case for the HPTLC method since substances can be transformed into fluorescent derivatives.     

Analysis of phenolic compounds by high performance liquid chromatography and ultra performance liquid chromatography

Two novel chromatographic methods both based on utilization of sub-2-micron particle columns were developed for the analysis of phenolic compounds in this work. An HPLC system was equipped with C(18) silica-based analytical column (50 mm x 4.6 mm, 1.8 microm) and a UPLC system with ethylene-bridged hybrid C(18) analytical column (100 mm x 2.1 mm, 1.7 microm). In total 34 phenolic substances were divided into groups of phenolic acids, flavonoids, catechins and coumarins and were analysed in sequence using different gradient methods. System suitability test data, including repeatability of retention time and peak area, mean values of asymmetry factor, resolution, peak capacity and the height equivalent of a theoretical plate were determined for each gradient method by 10 replicate injections. The developed methods were applied in the analysis of real samples (grape wines, teas).     

高效液相色谱-气相色谱在线联用同时测定土壤中饱和烃和芳香烃

为加强对土壤中石油烃类污染物的风险管控,生态环境部已将石油烃类列为土壤中的重点监测项目.石油烃源于石油与合成油,是涵盖一定碳数范围的碳氢化合物,主要分为饱和烃和芳香烃两大类.芳香烃通常是高度烷基化的单环、双环与多环芳烃,其对人和动物的毒性较饱和烃大很多,因此,仅仅测定土壤中总石油烃含量难以准确评估其环境毒性.目前环境领...     

Chemically bonded stationary phases for gas and high performance liquid chromatography

Summary This review is intended to summarize current knowledge on chemically bonded stationary phases. Their preparation and effect on chromatographic processes in GC and HPLC are described and the complex separation mechanism on these phases is discussed.     

Simultaneous quantification of seven bioactive components in Caulis Lonicerae Japonicae by high performance liquid chromatography

This study presents a new HPLC method for the simultaneous determination of seven major components, namely chlorogenic acid, caffeic acid, loganin, sweroside, secoxyloganin, rutin and luteolin 7-O-glucoside in Caulis Lonicerae Japonicae, a commonly used traditional Chinese medicinal herb derived from the caulis of Lonicera japonica Thunb. These seven compounds, belonging to the chemical types of phenolic acids, iridoids and flavonoids, were separated on a C18 column (250 x 4.6 mm, 5.0 microm) with the column temperature at 30 degrees C. The mobile phase was composed of (A) aqueous acetic acid (0.4%, v/v) and (B) acetonitrile using a gradient elution of 10% B at 0-12 min, 10-17% B at 12-25 min and 17% B at 25-35 min. The flow rate was 1.0 mL/min and detection wavelength was set at 245 nm. The limit of detection (S/N = 3) ranged from 0.10 to 0.23 microg/mL and the limit of quantification (S/N = 10) ranged from 0.69 to 3.56 microg/mL. All calibration curves showed good linear regression (r2 > 0.9990) within the test ranges. The intra- and inter-day precisions as determined from sample solutions were below 1.24 and 2.28%, respectively. The recoveries for seven compounds were found to range from 94.2 to 103.6%. This verified method has been successfully applied to evaluation of commercial samples of Caulis Lonicerae Japonicae from different markets in China.     

Identification and quantification of the constituents of madder root by gas chromatography and high-performance liquid chromatography

The possibilities in the identification and quantitation of the constituents of Rubia tinctorum L.'s root, called also madder root, was described and compared by gas chromatography (GC)-MS, high-performance liquid chromatography (HPLC)-UV/photodiode array detection (DAD) and HPLC-MS: chromatographic analyses were carried out in parallel, from the same samples/extracts/hydrolyzates. Anthraquinone glycosides, anthraquinones, carboxylic acids and sugars were determined directly in the presence of the matrix and in its extracts without and subsequently to hydrolyses. Hydrolyses were performed as a function of time, with hydrochloric and trifluoroacetic acids, as well as enzymatically. Data revealed that as hydrolyzing agent trifluoroacetic acid is to be preferred. Madder root's anthraquinones (pseudopurpurin/purpurin, alizarin, lucidin, munjistin, nordamnacanthal) were identified on the basis of their absorption spectra (HPLC-DAD) and fragmentation patterns by GC-MS and HPLC-MS, equally. Reproducibility of anthraquinone's quantitation, by HPLC-DAD and GC-MS, in the concentration ranges of 4 x 10(-5) to 3 x 10(-2)g/g dried sample, provided an average reproducibility of 4.2% (varying between 0.9 and 9.4% relative standard deviation (RSD percentages)). Carboxylic acids (malic, citric, quinic, rosmarinic acids) and saccharides (xylose, ribose, fructose, glucose, sucrose, primverose) were quantified as their trimethylsilyl (oxime) ether/ester derivatives by GC-MS, in the concentration ranges of 10(-5)g to 10(-2)g/g dried sample, with an average reproducibility of 4.7% RSD.     

液相色谱-毛细管气相色谱/质谱离线联用分析烟草中的挥发性及半挥发性成分

建立了一种用于烟草样品中挥发性、半挥发性成分分析的液相色谱-毛细管气相色谱/质谱(LC-CGC/MS)离线联用方法。研究了LC-CGC/MS的分离机理。LC分析选用氨基分析柱(250 mm×2.0 mm, 5 μm)作为分析柱,正己烷-二氯甲烷-乙腈(90:6.6:3.4, v/v/v)作为流动相,对挥发性、半挥发性成分进行分离,收集得到5个馏分,并存放在5个氮吹瓶中。多次进样并收集相同时间段的馏分,氮吹浓缩至1 mL,然后分别进行CGC/MS分析,所用的CGC柱为DB-5MS(60 m×0.25 mm×0.25 μm)。结果显示,与直接采用CGC/MS分析相比,采用LC-CGC/MS分析复杂样本的效果更好,定性的可靠性更高。     

纳升电喷雾-离子迁移谱及其与高效液相色谱的联用

搭建了一套纳升级电喷雾-离子源离子迁移谱仪。首先,分别对尾吹气流速、溶剂流速等影响仪器去溶剂化效果的参数进行了研究和优化。在此基础上,用一系列胺类化合物对该仪器的去溶剂化效果、分辨能力以及灵敏度进行了表征。实验结果表明,该仪器能够对电喷雾离子液滴实现完全去溶剂化;三辛胺的检出限可以达到10 μg/L。最后,将该仪器用作高效液相色谱的检测器,在无需衍生化的条件下对胺类混合物样品进行检测。由三乙胺、二乙胺以及丁胺组成的混合样品被成功分离并测定。该系统对三乙胺、二乙胺以及丁胺的线性响应范围均达到近两个数量级。     

Reversed phase C18 packings for the separation of polycyclic aromatic hydrocarbons by high performance liquid chromatography

Chromatographia - The preparation of C18 stationary phases for the separation of polycyclic aromatic hydrocarbons has been investigated. The effect of the pore size of the silica, the endcapping...     

Measurement of albuterol in guinea pig serum by high performance liquid chromatography with fluorescence detection

A sensitive, simple and reproducible high performance liquid chromatographic method for detecting and quantifying albuterol in guinea pig serum is described. A structurally related compound, bamethan, was used as an internal standard. The method employs ion-pair extraction with di(2-ethylhexyl)phosphate followed by chromatography on a Zorbax SB C18 reversed-phase column. Fluorescence detection was used to identify the compounds of interest. The calibration curve was linear between 1 and 50 ng/mL albuterol hemisulfate salt (0.83 and 41.50 ng/mL albuterol base), and the limit of detection for a 1 mL sample was 1 ng/mL albuterol hemisulfate salt (0.83 ng/mL albuterol base). Serum levels of albuterol were quantified from guinea pigs that had received the drug by continuous subcutaneous infusion at a dose of 0.2 mg/kg/day for 1, 5 or 10 days, or 10 days followed by a 24 h washout period.     

Comparison of ultra high performance supercritical fluid chromatography,ultra high performance liquid chromatography,and gas chromatography for the separation of synthetic cathinones

A comparison of ultra high performance supercritical fluid chromatography, ultra high performance liquid chromatography, and gas chromatography for the separation of synthetic cathinones has been conducted. Nine different mixtures of bath salts were analyzed in this study. The three different chromatographic techniques were examined using a general set of controlled synthetic cathinones as well as a variety of other synthetic cathinones that exist as positional isomers. Overall 35 different synthetic cathinones were analyzed. A variety of column types and chromatographic modes were examined for developing each separation. For the ultra high performance supercritical fluid chromatography separations, analyses were performed using a series of Torus and Trefoil columns with either ammonium formate or ammonium hydroxide as additives, and methanol, ethanol or isopropanol organic solvents as modifiers. Ultra high performance liquid chromatographic separations were performed in both reversed phase and hydrophilic interaction chromatographic modes using SPP C18 and SPP HILIC columns. Gas chromatography separations were performed using an Elite‐5MS capillary column. The orthogonality of ultra high performance supercritical fluid chromatography, ultra high performance liquid chromatography, and gas chromatography was examined using principal component analysis. For the best overall separation of synthetic cathinones, the use of ultra high performance supercritical fluid chromatography in combination with gas chromatography is recommended.     

Determination of lysinoalanine by high performance liquid chromatography

This work suggests an HPLC method for qualitative and quantitative determination of N^ε(2-amino-2-carboxyethyl)-L -lysine (LAL). LAL was released from total hydrolysates of various proteins of animal origin and derivatized with dansyl chloride. The performance of two different columns, Spherisorb 3S TG and μ-Bondapack C₁₈, was compared; better resolution and quantitative response were obtained with the former. The mobile phase was a mixture of 0.01 M phosphate buffer (pH 7) and acetonitrile. Linear response and quantitative repeatability were tested for both detectors used (UV-Vis set at 254 nm; fluorimetric set at λ_ex(max) = 360 nm and λ_em(max) = 525 nm). For LAL standard the minimum detectable amount was 0.05 ng, whereas for LAL in actual samples the amount was 0.5 ng (40 μg/g of analyzed proteins). Good analytical repeatability was obtained, resulting in CV % of 4.7 and 3.8 for UV and fluorimetric detectors, respectively. LAL recovery was determined using both detectors; the values obtained were 94 % (fluorimetric) and 92 % (UV). Greater noise levels were observed with the fluorimetric detector and its higher sensitivity could not, therefore, be fully utilized. The highest amounts of LAL were found in the casein (2816 μg/g) and cooked albumin (615 μg/g) samples.     

衍生化-高效液相色谱法测定西索米星

采用反相高效液相色谱法，以2，4-二硝基氟苯为衍生化试剂。其线性范围为10mg/L-500mg/L；检出限为5.0mg/L；相对标准偏差为2.3%。方法适用于西索米星的产品质量控制。     

Exploring the fatty acids of vernix caseosa in form of their methyl esters by off-line coupling of non-aqueous reversed phase high performance liquid chromatography and gas chromatography coupled to mass spectrometry

Vernix caseosa is a greasy biofilm formed on the skin of the human fetus in the last period of pregnancy. This matrix is known to contain a range of uncommon branched chain fatty acids. In this study, we studied the fatty acid composition of vernix caseosa by non-aqueous reversed phase high performance liquid chromatography (RP-HPLC) fractionation followed by gas chromatography-electron ionization mass spectrometry (GC/EI-MS) of the fractions. For this purpose the fatty acids from vernix caseosa were converted into the corresponding methyl esters. These were fractionated by non-aqueous RP-HPLC using three serially connected C(18)-columns and pure methanol as the eluent. Aliquots of the HPLC fractions were directly analyzed by GC/EI-MS in the selected ion monitoring mode. Data analysis and visualization were performed by the creation of a two dimensional (2D) contour plot, in which GC retention times were plotted against the HPLC fractions. Inspection of the plot resulted in the detection of 133 different fatty acids but only 16 of them contributed more than 1% to the total fatty acids detected. Identification was based on HPLC and GC retention data, GC/MS-SIM and full scan data, as well as plotting the logarithmic retention times against the longest straight carbon chain. In selected cases, aliquots of the HPLC fractions were hydrogenated or studied by means of the picolinyl esters. Using these techniques, the number of double bonds could be unequivocally assigned to all fatty acids. Moreover, the number of methyl branches, and in many cases the positions of methyl branches could be determined. The enantioselective analysis of chiral anteiso-fatty acids resulted in the dominance of the S-enantiomers. However, high proportions of R-a13:0, R-a15:0, and R-a17:1 were also detected while a17:0 was virtually S-enantiopure.     

Rapid simultaneous quantification of fructooligosaccharides in Morinda officianalis by ultra‐high performance liquid chromatography

Many Chinese herbal medicines with tonifying effects contain high levels of inulin fructooligosaccharides. These herbal medicines have high development and utilization value because of their effects against dementia, depression, and oxidative stress; on improving learning and memory ability; and on enhancing immunity. In this study, a method was developed for the separation and simultaneous quantitation of fructose, glucose, sucrose, and ten inulin fructooligosaccharides by ultra‐high‐performance liquid chromatography with evaporative light scattering detection within 10 min. Separation was performed on an Amide column with gradient elution. The calibration curves for the 13 constituents showed good linearity (R² > 0.9991). The limits of detection and quantification were 10.78–33.44 and 35.94–124.81 μg/mL, respectively, and the recoveries ranged from 98.90 to 103.67%. This method was successfully used to quantify the 13 constituents in the Chinese herbal medicine Morinda officinalis. The contents of the ten inulin fructooligosaccharides ranged from 56.28 to 60.71%. This method is accurate, rapid and simple and can be used for quantitative analysis in the quality control of herbal medicines and functional foods.