Determination of imazethapyr and imazapyr residues in soil by coupled-column liquid chromatography

Summary A column-switching method using two separation columns combined with UV detection at 260 or 236 nm has been used to determine the imidazolinone herbicides imazethapyr and imazapyr in soils. The residues were extracted from the soil with 0.1 M aqueous sodium carbonate solution and, after adjusting the pH to 2.0, the solution was partitioned with dichloromethane. Limits of determination for imazethapyr and imazapyr were 3 μg/kg. Recoveries were from 55 to 75% for both imidazolinone herbicides in the range 3–100 μg/kg in soil.     

Determination of interferon-gamma in Chinese hamster ovary cell culture supernatant by coupled-column liquid chromatography

A robust tandem HPLC method coupling size-exclusion (Shodex Asahipak GS-320HQ) and reversed phase (Vydac 218TP54) columns with ultraviolet detection was developed for quantitative determination of interferon-gamma (IFN-gamma) in Chinese hamster ovary cell culture supernatant. The 2D-HPLC system was linked up by a 6-port 2-position low hold-up volume switch valve. Compared to a commercial ELISA kit for IFN-gamma, the coupled column LC approach was able to detect and quantify soluble IFN-gamma, regardless of the glycoprotein's molecular/conformational variability and sample background. Each LC-LC analysis took 90 minutes inclusive of column regeneration. The relative standard deviation of measurements (n = 5) was less than 3%. The limit of detection (LOD) was determined to be 0.35 microg IFN-gamma.     

Separation of phenolic compounds and corresponding glucuronides by coupled-column micellar reversed-phase liquid chromatography

Summary An isocratic HPLC technique for separation of phenolic compounds and corresponding glucuronides in urine is developed. Sample pre-treatment, often a tedious and rate-limiting factor, was eliminated by use of a coupled column system. Spiked urine samples were injected directly into a C₄ precolumn and a selected fraction was transferred on-line from the precolumn to a silanized C₁₈ analytical column in the backflush mode. Analyte peak enrichment was attained by employing mobile phases of different elution strengths. The weaker mobile phase (7% v/v acetonitrile) was used to strongly retain the analytes on the precolumn while most of the polar endogenous compounds were washed to waste. Elution and transfer of the trapped analytes from the precolumn to the analytical column was achieved by introducing a stronger mobile phase (20% v/v acetonitrile) with the aid of a switching valve. The use of cetyltrimethylammonium bromide as counter ion and micellar agent in the mobile phase involved a high selectivity for the analytes relative to the urine matrix components and allowed simultaneous analysis of the glucuronides and parent compounds without the need of gradient elution. The system demonstrated a good repeatability on spiked urine samples. Who passed away July 21, 1996     

超高效液相色谱法测定水果和饮料中残留的氟嘧菌酯和嘧螨酯

建立了多种水果和饮料中氟嘧菌酯和嘧螨酯残留的超高效液相色谱测定方法。样品用乙酸乙酯-环己烷(体积比为1∶1)超声波萃取,凝胶渗透色谱法净化,超高效液相色谱-二极管阵列检测器检测,外标法定量。采用BEH C18色谱柱(50 mm×2.1 mm,1.7 μm),流动相为水-乙腈(体积比为3∶7),流速为0.3 mL/min,柱温为40 ℃,紫外检测波长为251 nm。实验结果表明：氟嘧菌酯和嘧螨酯在0.05～2 mg/L范围内线性关系良好(r>0.999),在不同的基质中添加3个浓度水平(0.01,0.05,0.1 mg/kg)的氟嘧菌酯和嘧螨酯,两者的回收率均在82.60%～101.11%之间,相对标准偏差为5.4%～15.3%;检出限不大于6 μg/kg,定量限不大于20 μg/kg。     

Determination of preservatives in cosmetics and food samples by micellar liquid chromatography

An analytical procedure has been developed for the analysis of benzoic acid, p-hydroxybenzoic acid, methyl-, ethyl-, propyl-, isopropyl-, and butyl esters of p-hydroxybenzoic acid by micellar liquid chromatography. After dilution in n-propanol the sample was directly injected onto a Lichrosorb ODS, 5 microm (250 x 4.6 mm ID) column and eluted with aqueous 2% Brij-35 adjusted to pH 3.0 with phosphoric acid:propanol (80:20 v/v) at a flow rate of 1 mL min(-1) and UV detection at 254 nm. A linear calibration curve was obtained simultaneously for each component in the range of 50-500 microg mL(-1) for benzoic acid and 5-150 microg mL(-1) for the other components; detection limits were within 25-250 ng mL(-1) corresponding to 125-1250 pg per injection (5 microL). The reproducibility in terms of average peak area and average retention time was obtained with coefficients of variation (CV) of 1.2% and 0.5%. The method was applied to analysis of these compounds in cosmetics (shampoos, hand lotions, creams, and bath foam) and food samples.     

超高效液相色谱法检测土壤中硝基呋喃类药物残留

建立超高效液相色谱法检测土壤中硝基呋喃类药物残留。通过单因素和正交设计试验,考察了超声时间、提取温度、提取次数对硝基呋喃类药物残留回收率的影响。最优提取条件为超声时间10 min、提取温度45℃、提取次数为4次。硝基呋喃类药物的质量浓度在1~4μg/mL范围内与色谱峰面积成良好的线性关系,线性相关系数均大于0.9999。加标回收率为74.34%~102.52%,测定结果的相对标准偏差为0.91%~4.49%(n=6)。该方法简单、快速,测定结果准确可靠,可用于土壤中硝基呋喃类药物残留量的测定。     

Determination of thiopental in human serum and plasma by reversed-phase high-performance liquid chromatography

Summary A high-performance liquid chromatographic method for the analysis of thiopental in 100l of human serum or plasma is described. The procedure involves protein precipitation with acetonitrile. The supernatant is directly injected into a chromatograph containing a reversed-phase CLC-ODS (Shimadzu) column. A 5050 (v/v) mixture of water-acetonitrile, at a flow-rate of 1.0ml/min is used as the mobile phase. Detection is carried out ata wavelength of 280nm. Total analysis time per sample is 10min. The assay was found to be linear in the range of 0.1 to 120g/ml. Reproducibility was good, with intra-assay coefficients of variation from 1.780 to 3.208% and inter-assay coefficients of variation from 3.241 to 4.860%. The absolute recoveries were 97.4 to 101,4%. Other drugs were tested for potential interference with the assay, but none was found.     

高效液相色谱法测定黄瓜和油菜中的啶虫脒残留量

建立了一种高效液相色谱测定黄瓜和油菜中啶虫脒农药残留的方法。以乙腈提取,弗罗里硅土净化,采用Agilent 1100高效液相色谱仪带DAD检测器对待测组份进行了分离和测定,检测波长254 nm,使用C18不锈钢反相柱（250 mm×4.6 mmi.d.,5μm）,以V（乙腈）∶V（水）=30∶70作流动相,啶虫脒在0.05-2.00mg/L范围内呈良好的线性关系（r=0.9999）,方法的添加回收率范围为73.7%-85.6%。RSD为2.2%-10.3%,能够满足啶虫脒在黄瓜和油菜中残留分析的要求。     

Determination of procaine and tetracaine in plasma samples by micellar liquid chromatography and direct injection of sample

Summary A liquid chromatographic procedure is proposed for the determination of procaine and tetracaine in plasma samples with direct injection. The method uses a Spherisorb octadecylsilane ODS-2 C₁₈ analytical column and a micellar mobile phase containing 0.15 M sodium dodecyl sulphate, 0.5% triethylamine at pH 2.5 and 10% propanol. The UV detection was carried out at 300 nm. Plasma sample preparation required only adequate dilution with the mobile phase before injection into the chromatographic system. The proposed method allows the determination of procaine and tetracaine in plasma at therapeutic levels.     

液相色谱法检测水果蔬菜中的烟碱类农药残留

建立了果蔬样品中5种烟碱类农药(噻虫嗪、吡虫啉、啶虫脒、噻虫啉、噻虫胺)残留的液相色谱快速检测方法。样品采用乙腈提取,浓缩,水转溶后经ENVI-18固相萃取柱净化,0.02 mol/L NaOH预淋洗除去柱上中等极性干扰物,100%乙腈1 mL洗脱5种烟碱类残留,反相高效液相色谱-二极管阵列检测器检测。在黄瓜空白基质中0.1~1.0 mg/kg的加标浓度范围内,5种农药的回收率为50.8%~108.9%,相对标准偏差(RSD)小于15%;而苹果、梨、香蕉、西红柿和韭菜空白基质在0.1~1.0 mg/kg添加水平下,5种农药的回收率均大于80%,RSD小于11%。所测试的6种果蔬样品中噻虫嗪、噻虫胺、吡虫啉的检出限(LOD)为0.01~0.02 mg/kg,啶虫咪和噻虫啉的LOD为0.03~0.05 mg/kg,方法可满足水果蔬菜中烟碱类农药多残留分析的要求。     

Determination of alkenylbenzenes and related flavour compounds in food samples by on-column preconcentration-capillary liquid chromatography

A new, simple and versatile method is presented for the determination of different concentration levels of alkenylbenzenes (eugenol, isoeugenol, eugenol methyl ether, myristicin, anethole and estragole) and the related flavour compounds (coumarin and pulegone) in food samples. The method involves the use of a stationary phase (capillary column) for the enrichment with appropriate elution. After the sample had completely passed through the capillary column the eluent was changed and the separation/detection was achieved. Excellent linearity was obtained under the proposed conditions for a direct determination method and a method including on-line preconcentration. The limits of detection were in the ranges 97–148 and 9.5–14.2 ng/mL, respectively. Evidence for a matrix effect was not found and recoveries between 92 and 110% were obtained. The precision of the method, expressed as relative standard deviation values, was below 5% in all cases. The applicability of this methodology was tested by analyzing synthetic and real food samples.     

Determination of serum metabolic profiles of bile acids by microcolumn liquid chromatography/laser-induced fluorescence

A method for the determination of individual free and conjugated bile acids in serum using microcolumn liquid chromatography coupled with a laser-induced fluorescence detector is described. Bile acids are separated into free/glycine-conjugate and taurine-conjugate fractions using a Sep-Pak SIL cartridge. The taurine-conjugated bile acid fraction is subjected to enzymatic hydrolysis. Subsequently, free and conjugated bile acids are labeled using 4-(bromomethyl)-7-methoxycoumarin as a fluorogenic reagent, producing stable derivatives that can be excited by the 325 nm line of a He/Cd laser. Prior to their fluorimetric detection, the individual components of a bile acid serum profile are separated by reversed-phase microcolumn liquid chromatography.     

Determination of ephedra alkaloids by high-performance liquid chromatography

Summary Two simple methods were developed for the simultaneous determination of six alkaloids (ephedrine, pseudoephedrine, norephedrine, norpseudoephedrine, methylephedrine and methyl-pseudoephedrine) inEphedrae Herba by high-performance liquid chromatography. The first method was carried out by using a Cosmosil 5C₁₈-MS column with a gradient solvent system consisting of a phosphate buffer and acetonitrile, and detection at 210 nm. The contents of alkaloids in non-pretreated ephedra herb extracts could be determined easily in 50 min. Alternatively, the alkaloids could be determined within 35 minutes by using a Cosmosil 5C₁₈-MS column with an isocratic solvent system of a sodium dodecyl sulfate-acetonitrile solution. The two methods are compared and discussed.     

Determination of glyphosate residues in plants by precolumn derivatization and coupled-column liquid chromatography with fluorescence detection

A rapid method was developed for the trace-level determination of glyphosate in olives. After extraction of the glyphosate with water-dichloromethane and simultaneous removal of the olive oil, an aliquot of the aqueous extract is derivatized with 9-fluoroenylmethyl chloroformate (9-fluorenylmethoxycarbonyl chloride; FMOC-CI) to produce a highly fluorescent derivative. A 2 mL aliquot of this extract is injected directly into a coupled-column liquid chromatography system with fluorimetric detection (LC/LC-FD). The procedure was validated by recovery experiments at 3 spiking levels; recoveries ranged from 80 to 97% with relative standard deviations of 3-6%. The limits of detection and quantitation were estimated to be 0.01 and 0.05 mg/kg, respectively. The method was also applied to other plant materials, i.e., tomato plants, strawberry plants, and pear trees (branches, leaves, and fruits) suspected to be contaminated by glyphosate. In all these cases, the extraction was performed in aqueous media. The derivatization reaction was modified by increasing the FMOC-CI concentration, to ensure a quantitative reaction between analyte and reagent in the presence of high levels of coextractives, which also react with FMOC-CI. The final determination was by LC/LC-FD, yielding a rapid, selective, and sensitive method for the determination of glyphosate residues in these samples. The method was tested with real-world samples after application of glyphosate to the surrounding area of crops.     

Determination of abamectin residues in fruits and vegetables by high-performance liquid chromatography

A rapid and sensitive HPLC method has been developed and validated for the determination of abamectin residues (avermectin B1a and B1b, as well as the metabolite 8,9-Z-avermectin B1) in apples, pears and tomatoes. Residues are extracted with acetonitrile. The diluted extract is cleaned up on a C18 solid-phase extraction cartridge. Abamectin residues are derivatised with trifluoroacetic acid and 1-methylimidazole and determined by reversed-phase liquid chromatography with fluorescence detection (excitation: 365 nm and emission: 470 nm). High and consistent recoveries, ranging from 88 to 106%, were obtained, at spiking levels of 10, 20 and 50 micrograms/kg, when analysing apples, pears and tomatoes.     

A study of the liquid chromatography of some fungicidally active arylsulphonohydrazides

Summary A number of fungicidally active arylsulphonohydrazides are examined by normal- and reversed-phase liquid chromatography. Although good separations are achieved by reversed-phase LC, difficulties are encountered due to analyte hydrolysis. On the other hand, satisfactory analyses are possible by normal-phase LC particularly on modified silicas.     

固相萃取-超高效液相色谱联用测定水果及果酱中的展青霉素

以硅酸镁、硅胶、硅藻土、硫酸钙为原料,加入乙醇研磨成匀浆,干燥,填充于聚丙烯柱管中,制备成新型固相萃取小柱。样品经果胶酶酶解,乙腈提取,固相萃取净化,以C18色谱柱(100 mm×2.1 mm,1.8μm)为分离色谱柱进行定性、定量分析。流动相为0.8%(体积分数)四氢呋喃水溶液,流速为0.5 mL/min,以276 nm波长进行检测。考察了果胶酶对萃取效果的影响、固相萃取小柱的净化效果及最佳色谱分析条件。在0.1~10 mg/L范围内,展青霉素峰高与质量浓度呈良好的线性关系,相关系数(R~2)为1,方法检出限为10.22μg/kg,样品的加标回收率为86.58%~94.84%,相对标准偏差(RSD)为1.45%~2.28%。实验结果表明,自制固相萃取小柱净化效果好,超高效液相色谱分离效能高,样品测定操作方法简单,结果准确,对水果制品的质量安全控制具有重要的意义。     

多功能柱净化-高效液相色谱法检测谷物中的玉米赤霉烯酮

建立了玉米和小麦中玉米赤霉烯酮（ZEN）的多功能柱净化-高效液相色谱检测方法。样品经乙腈-水混合溶剂（V（乙腈）：V（水）=84：16）提取,通过多功能净化柱（MFC）进行一次性净化,以Symmetry^R C18柱为分离柱,甲醇-水（V（甲醇）：V（水）=68：32）为流动相进行高效液相色谱分离和检测。玉米赤霉烯酮的质量浓度在0．01～4．0μg／mL范围内呈良好线性,相关系数为0．9996。检出限为0．04μg／g,在0、04—5．0mg／kg添加范围内的回收率为87．5％～98．6％,相对标准偏差为1．5％～8．3％。     

Determination of sugars by liquid chromatography with post-column catalytic derivatization and fluorescence detection

Summary A method for the determination of reducing sugars such as fructose and glucose and nonreducing sugar such as sucrose by high performance liquid chromatography followed by an acidic hydrolysis and a derivatization with benzamidine has been developed. After separation of sugars on a gel column packed with a polymer-based cation exchange material (Sugar-Pak I, Waters-Millipore), the sucrose is first hydrolysed in a solid phase reactor to convert it into reducing subunits. A post-column fluorigenic reaction with benzamidine under alkaline condition allows the selective determination of both natural and converted reducing carbohydrates.This procedure has proven to be selective (fluorigenic detection) and highly sensitive (allowing detection as little as picomoles amounts), reproducible and linear over a broad range of concentrations: 5×10^–4 to 1.0×10^–2 M.The applicability of this method to natural matrices such as plant extracts and beverages is also described. The sugar content of a barley extract has been determined and compared with a specific enzymatic test. The determined sugar content of natural and commercial lemon juices as well as of Cola beverages has been compared with those found by the conventional LC refractive index analytical procedure. In all cases, the results were comparable and were within the experimental errors of the methods.