Determination of tetracyclines residues in honey by on-line solid-phase extraction high-performance liquid chromatography

An automated system using on-line solid-phase extraction (SPE) high-performance liquid chromatography (HPLC) with ultraviolet (UV) detection was developed for the determination of tetracyclines (TCs), such as tetracycline (TC), oxytetracycline (OTC), chlortetracycline (CTC), metacycline (MC), and doxycycline (DC) in honey. One milliliter diluted honey sample was injected into a conditioned C18 SPE column and the matrix was washed out with water for 3 min. By rotation of the switching valve, TCs were eluted and transferred to the analytical column by the chromatographic mobile phase. Chromatographic conditions were optimized. TCs were separated in less than 8 min with a gradient elution using a mixture of 0.8% formic acid and acetonitrile. The UV detection was performed at 365 nm. The conditions for on-line SPE, including solvent and total time for loading sample and washing matrix were also optimized. Time for extraction and separation decreased greatly. For the five kinds of TCs, the limits of detection (LODs) at a signal-to-noise of 3 ranged from 5 to 12 ng g⁻¹. The relative standard deviations (R.S.D.) for the determination of TCs ranged from 3.4 to 7.1% within a day and ranged from 3.2 to 8.9% in 3 days, respectively.     

Determination of gliclazide in serum by high-performance liquid chromatography using solid-phase extraction.

A simple and sensitive high-performance liquid chromatographic method for a routine assay of gliclazide in serum is described. Serum samples spiked with glibenclamide (internal standard) were applied to Bond Elut C18 cartridges. After washing with phosphate buffer (pH 7.5) and water, the cartridge was eluted with 60% methanol. The eluate was evaporated to dryness. The residue was dissolved in methanol and injected onto an octadecyl silica column (5 microns, 150 mm x 4.6 mm I.D.). The mobile phase was 0.04 M potassium dihydrogenphosphate (pH 4.6)-acetonitrile-isopropyl alcohol (5:4:1, v/v). Ultraviolet detection at 227 nm was used. The minimum detectable level of gliclazide was 20 ng/ml.     

Determination of estazolam in plasma by high-performance liquid chromatography with solid-phase extraction.

A high-performance liquid chromatography (HPLC) assay was developed for the determination of estazolam in human plasma. Estazolam and alprazolam as an internal standard were detected by ultraviolet absorbance at 240 nm. Estazolam in plasma was extracted by a rapid and simple procedure based on cyanopropyl bonded-phase extraction. Chromatographic separation was achieved with a reversed-phase C8-5 column using a mobile phase of 0.5% potassium dihydrogenphosphate(pH 4.5)-acetonitrile (70:30, v/v). The determination of estazolam was possible in the concentration range of 1.0 - 200.0 ng/mL. The mean recovery of estazolam added to plasma was 96.1 +/- 1.5% with coefficients of variation of less than 5.5%. This method is applicable for accurately monitoring the plasma level of estazolam in healthy subjects participating in scientific research.     

Determination of 4-aminopyridine in serum by solid-phase extraction and high-performance liquid chromatography.

An assay for the determination of 4-aminopyridine in serum has been developed using 3,4-diaminopyridine as internal standard and reversed-phase high-performance liquid chromatography with detection at 244 nm. A mobile phase of acetonitrile-methanol-ethanol-1% ammonium carbonate (75:10:10:5) provided excellent separation of both compounds. Samples were extracted on solid-phase columns. The linearity, precision, recovery and the limit of detection were all sufficient for the routine use of this assay in clinical studies of patients treated with 4-aminopyridine.     

Determination of tetracyclines in plasma by high-performance liquid chromatography

A new method for the separation and quantitative determination of certain anti-biotics of the tetracycline series in blood plasma by high-performance liquid chromatography on a column filled with Partisil PXP 5 silica gel is described.I. M. Sechenov First Moscow Medical Institute. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 376–379, May–June, 1981.     

Determination of tetracyclines in plasma by high-performance liquid chromatography

A new method for the separation and quantitative determination of certain anti-biotics of the tetracycline series in blood plasma by high-performance liquid chromatography on a column filled with Partisil PXP 5 silica gel is described.     

Determination of sulfonamides in livers using matrix solid-phase dispersion extraction high-performance liquid chromatography

The matrix solid-phase dispersion (MSPD) was applied for extracting seven sulfonamides (SAs) in liver samples. The separation and determination were carried out by high-performance liquid chromatography. The analytes were derivated with fluorescamine and detected with fluorescence detector. The types of dispersion adsorbents for MSPD were examined and the highest recovery was obtained when the diatomaceous earth was used as the dispersion adsorbent and the mass ratio of dispersion adsorbent to sample was 3:1. The acetone was used as the elution solvent. Under the optimal conditions, the linear range for determining the SAs in liver samples was 5.0-1000.0 ng/g. The porcine, chicken and cattle liver samples were analyzed and the average recoveries of seven SAs were higher than 84.6%.     

Determination of imazaquin residues in soil by solid-phase extraction and high-performance liquid chromatography

A method has been developed for the quantitation of imazaquin residues in soil. The herbicide was extracted from soil with methanol-water (2 + 1, v/v) and cleaned up by strong anion-exchange solid-phase extraction cartridges. Analysis was performed by using high-performance liquid chromatography with ultraviolet detection. Average recoveries through the method ranged from 90.7 to 100.6%, with relative standard deviation equal to or lower than 6.6%. The limit of detection was estimated to be 0.0015 mg/kg, and the minimum quantitation concentration of imazaquin in soil was 0.005 mg/kg. This method was successfully applied to evaluate imazaquin residue levels in soil and its dissipation rates in a soybean field in the Xisanqi District of Beijing, People's Republic of China. The dissipation study showed that the half life of imazaquin in soil was 10.37 +/- 0.0135 days at 3 different application rates.     

Determination of forchlorfenuron residues in watermelon by solid-phase extraction and high-performance liquid chromatography

A method using solid-phase extraction for cleanup, followed by high-performance liquid chromatography with ultraviolet detection (HPLC/UV), was developed for the determination of forchlorfenuron residues in watermelon. The pesticide is extracted from the sample with acidic acetonitrile, and the extract is loaded onto a primary-secondary amine (PSA) column. The pesticide is eluted with acetone and determined by HPLC/UV. The PSA column was found to provide effective cleanup, removing the greatest number of sample matrix interferences. The acetonitrile extraction followed by the PSA cleanup provided recoveries of >95%, coefficients of variation (precision) of <10%, and sensitivity of 0.005 mg/kg, in agreement with the directives for method validation in residue analysis. The proposed method was successfully used to determine forchlorfenuron residue levels and dissipation rates in watermelon grown in an experimental greenhouse in Beijing, People's Republic of China.     

High-performance liquid chromatography of sulphonamides extracted from bovine and porcine muscle by solid-phase dispersion.

A method has been developed for the analysis of sulphonamides in bovine and porcine muscle, based on solid-phase dispersion. Muscle tissue was blended with pre-washed C18 coated silica (55-105 microns), and the resulting homogeneous solid packed into a polypropylene syringe barrel. Fatty material was washed from the sample using hexane, and the sulphonamide analytes eluted with dichloromethane. The collected fraction was dried under nitrogen and reconstituted in 20% methanol in 0.01 M sodium acetate/acetic acid (pH 5) buffer. After sonication and filtration, the sample was analysed by high-performance liquid chromatography on a C18 column using UV diode array detection. Individual sulphonamides could be detected down to 0.01 ppm, whilst analyte identity could be confirmed by diode array spectrum down to 0.02 ppm.     

固相萃取-高效液相色谱检测葡萄酒中赭曲霉毒素A

使用C18小柱固相萃取, C18反相柱(250 mm×4.6 mm i.d.)分离,V(乙腈):V(水):V(乙酸)＝99:99:2为流动相,荧光检测器(激发波长333 nm,发射波长460 nm)检测,测定葡萄酒中赭曲霉毒素A.其质量浓度在6.25～200 ng/mL范围内呈良好线性,相关系数为0.9997.样品经浓缩60倍后,方法检出限为0.027 ng/mL.对红葡萄酒、干红及白葡萄酒进行了加标回收实验,回收率为80.1%～109.8%.平行7份样品加标回收率相对标准偏差为5.9%.对市售6种葡萄酒进行了赭曲霉毒素A的测定.     

Determination of linear alkylbenzene sulfonates by ion-pair solid-phase extraction and high-performance liquid chromatography

In this paper, the potential use of multiwalled carbon nanotubes (MWCNTs) as solid phase extraction (SPE) adsorbent was evaluated for preconcentration of linear alkylbenzene sulfonates (LAS) using ion-pair (IP)-SPE with tetrabutylammonium hydroxide (TBAH). The LAS homologues present in the aqueous sample were ion-paired with TBAH and the solution was passed through the MWCNT cartridges. The analytes retained in the cartridge were eluted with methanol and the concentrated methanol extract was analysed by HPLC-UV. In order to obtain the satisfactory recovery of LAS homologues, various parameters including the type and amount of the ion-pair reagents, the desorption and enrichment conditions such as the effect of eluent and its volume, pH, the flow rate, the ultrasonic time of sample, and the volume of sample solution were systematically optimized. Under the optimal conditions, LAS homologues could be easily extracted by the proposed SPE cartridge. The favorable limits of detection (LOD) for LAS homologues were in the range from 0.02 to 0.03 μg L⁻¹, and the relative standard deviations (RSDs) were 1.55-2.54% for 10 μg L⁻¹ LAS (n = 6). The proposed method has been successfully applied for the analysis of LAS homologues in aqueous environmental samples. A comparison study with ion-pair solid extraction on MWCNTs, C8 and C18 as adsorbents for LAS demonstrated that ion pair-based solid extraction on MWCNTs adsorbent was advantageous over C8 and C18, the widely used traditional adsorbents.     

Determination of benzene metabolites in urine of mice by solid-phase extraction and high-performance liquid chromatography.

A method was developed for quantitative measurement of trans,trans-muconic acid, catechol, hydroquinone and phenol in urine. Hydrolysis of esterified and glucuronized phenolic compounds was effected by specific enzymes. The hydrolysed mixture was purified and separated by solid-phase extraction with an anion exchanger, followed by extraction with diethyl ether. By using a clean-up procedure the natural background from mouse urine could be reduced, so that the detection limit of the metabolites was in the range 3-60 mg/l. Optimization of the chromatographic conditions resulted in a short high-performance liquid chromatography analysis time. Phenol had the longest retention time of about 10 min. The clean-up procedure could also be used for phenylmercapturic acid, an additional benzene metabolite, but for sensitive high-performance liquid chromatographic detection of phenylmercapturic acid other conditions are necessary.     

Determination of triazines and dinitroanilines in waters by high-performance liquid chromatography after solid-phase extraction

A rapid and selective method for the simultaneous determination of triazines and dinitroanilines in real water matrices is suggested based on a preliminary adsorption on an RP-18 cartridge, an elution step using acetonitrile and HPLC separation with a Lichrosorb RP- Select B column and UV detection. The washing step cartridge is critical for triazines: terbutryn is eluted with quantitative recovery only after washing with an NH₃ solution. The degree of enrichment of the compounds studied has been determined: triazine recoveries are quantitative, while dinitroaniline recoveries are between 66% and 78% at the lowest fortification level. The detection limits for the ten herbicides are in the range 0.03-0.1 μg/l. The analysis time is 2 h.     

Determination of rotenone residues in raw honey by solid-phase extraction and high-performance liquid chromatography

A method for determining residues of the insecticide rotenone in raw-honey by high-performance liquid chromatography (HPLC) is described. To extract the residues, organic solvents such as ethyl acetate, n-hexane/dichloromethane and solid-phase extraction with octadecylsilane cartridges or Florisil packed columns were tested. Determination was carried out by reversed-phase HPLC using acetonitrile-buffer phosphate (pH 7) (60:40, v/v) as mobile phase and detection at 210 nm. Although the data showed that the two extraction methods were able to isolate the pesticide residues, the extraction on octadecylsilane cartridges was preferred due to its simplicity and higher recovery. Recoveries depended strongly on the fortification level for the two extraction procedures. Practical determination limits of 0.015 mg/kg were obtained. In the analysis of honeys, from beehives treated with rotenone at therapeutical doses for 1 month, residual amounts below 0.2 mg/kg were found.     

Determination of ethylenediaminetetraacetic acid in sea water by solid-phase extraction and high-performance liquid chromatography

The chelating agent EDTA is widely used, and as a result is showing up widely in the aquatic environment. Here we describe a preconcentration procedure for measuring EDTA concentration in sea water samples by HPLC. The procedure consists of forming an Fe(III) complex followed by solid-phase extraction using an activated carbon cartridge. After the preconcentration, EDTA was quantified by HPLC with ultraviolet detection (260 nm). The enrichment permitted the determination of EDTA at concentrations as low as 1 nM. Good recoveries were obtained for both brackish and full-strength sea water with high repeatability (RSD < 6%). The method was applied to sea water samples taken from near the mouth of the Oyabe River in Japan.     

Determination of p-methylthiobenzamide and p-methylthiobenzamide-S-oxide from rat plasma using solid-phase extraction and high-performance liquid chromatography

p-Methylthiobenzamide (PMTB) is a thiocarbonyl compound exhibiting marked hepatotoxicity and nephrotoxicity. We describe a high-performance liquid chromatographic method for analyzing PMTB and a metabolite, p-methylthiobenzamide-S-oxide (PMTBSO), from rat plasma using a solid-phase extraction technique. In this way, PMTB and PMTBSO can be extracted from 0.5 ml of plasma and separation achieved by an ODS analytical column in as little as 9 min. The mobile phase used was methanol-water (55:45, v/v) and the wavelength for detection was 290 nm. The limits of detection in plasma were 15 ng/ml for PMTB and 33 ng/ml for PMTBSO; the absolute recovery from spiked plasma samples was greater than 84.4% for both compounds and the internal standard. The method was linear throughout the range used with correlation coefficients greater than 0.969. The intra-day accuracy ranged from 1.52 to 15.23% relative error for the PMTB concentration range 151-3025 ng/ml; accuracy of 4.97% or less was obtained for PMTBSO concentrations of 1672-20,068 ng/ml. The intra-day precision (coefficient of variation) of the procedure was found to be no greater than 5.28% for PMTB and 7.9% for PMTBSO. Inter-day accuracy and precision measurements were similar.     

Determination of alkylphenols and alkylphenol polyethoxylates by reversed-phase high-performance liquid chromatography and solid-phase extraction

A simple, accurate and reproducible reversed-phase high-performance liquid chromatography (HPLC) method was developed for the separation and characterisation of alkylphenols (APs) and alkylphenol polyethoxylates (APEOs), using a C18 octadecyl silica (ODS) column. APs and each APEO oligomer were separated successfully within a reasonable time without gradient elution. An excellent resolution was obtained, even for mixtures of APs and low EO number APEOs, which are otherwise difficult to separate using conventional normal-phase HPLC methods. This method, combined with solid-phase extraction, was highly applicable for the simultaneous determination of alkylphenols and alkylphenol ethoxylates in real samples.