Characterization of commercial kava-kava herbal drug and herbal drug preparations by means of nuclear magnetic resonance spectroscopy

The efficiency of one- and two-dimensional NMR experiments in characterizing the content of the constituents of both herbal drugs and herbal drug preparations is demonstrated for kava-kava. These experiments directly detect active constituents represented by kavalactones in both a finely powdered herbal drug and a commercial extract. In addition, NMR spectroscopy can detect all other compounds present in the extract. As previously evidenced, NMR experiments can represent a generally applicable technique for rapid screening and are a complement to the classical analytical techniques such as high-performance thin-layer chromatography, high-performance liquid chromatography, capillary gas chromatography, and electrophoresis. These experiments can be considered a very simple and fast analytical method to obtain a fingerprint of the herbal drugs and their preparations, and to quantify the content of the active principles of the extract.     

Determination of ivermectin in medicated swine feeds at the 2 ppm concentration level

An analytical method has been developed that is applicable to the determination of Ivermectin in medicated feeds at the 2 ppm concentration level. It is based upon liquid chromatographic analysis with a reverse-phase column and ultraviolet detection. After the drug is extracted from the feed into methanol, an analytical sample is prepared by the consecutive use of column chromatography on alumina and solid-phase extraction on Sep-Pak C18 and silica cartridges. This procedure has been applied to the concentration range 0.50-3.0 ppm of Ivermectin in feed with an accuracy of +/- 2% mean relative error and a precision of +/- 2% relative standard deviation at the 2 ppm concentration level.     

Colorimetric determination of arprinocid in feed.

An analytical method has been developed for the determination of arprinocid (9-(2-chloro-6-fluorophenylmethyl)-9H-purin-6-amine) in feed, based upon measurement of the absorbance of the diazo chromophore formed from a product of zinc reduction of the drug in acidic solution. The analyte is extracted from the feed into chloroform in the presence of a pH 7 phosphate buffer and isolated by adsorption chromatography on alumina, followed by partitioning between hexane and 0.15M HCl. The reduction product in the aqueous phase is then treated for colorimetric measurement. This procedure has been applied to determining 0.0010--0.0080% arprinocid in feed with a precision of less than 5% relative standard deviation near the middle of this concentration range. Of 32 feed additives examined, only zoalene and sulfamethazine were serious interferences. A study and discussion of several factors, e.g., reaction time, pH, and amount of zinc metal, that affect the analytical reactions are also included.     

Simple multiresidue method for monitoring of trimethoprim and sulfonamide residues in buffalo meat by high-performance liquid chromatography

A simple, specific, and rapid analytical method for the determination of trimethoprim (TMP) and three sulfonamide (SA) antimicrobial drug residues in buffalo meat is developed and validated. This method is based on a solid-phase extraction technique followed by high-performance liquid chromatography (HPLC)-photodiode array (PDA) detection. Target compounds were extracted from the meat by acetonitrile and water, cleaned up on a Bond Elute C 18 cartridge column, and separated on a RP-C 18 column during HPLC analysis. Acetonitrile along with water appears to be an excellent extractant as recovery of the analytes at maximum residues levels (MRLs) in spiked sample was in the range of 75-108%, with coefficient of variations (CVs) ranging between 1.34 and 22%. The limit of detection (LOD) and the limit of quantification (LOQ) were 0.031 and 0.062 microg/g, respectively, for all of the compounds. Intra- and interday assay precisions of the method at 0.125 microg/g concentrations for any drug ranged between 3 and 4%. The linearities of the TMP, sulfadimidine (SDM), sulfadoxine (SDO), and sulfamethoxazole (SMX) were 0.9989, 0.9999, 0.9998, and 0.9997, respectively. For robustness, the analytical method was applied to 122 buffalo meat samples obtained from export meat processing plants.     

Development of an enzyme-linked immunosorbent assay for the determination of maduramicin in broiler chicken tissues.

Maduramicin is one of the most widely used coccidiostats in the world. A rapid and accurate analytical method for this drug should provide producers and users with an effective management tool. The current chromatographic methods are sensitive but labor-intensive. This paper reports the development of an enzyme-linked immunosorbent assay (ELISA) based on an immunoaffinity chromatography cleanup procedure for the analysis of maduramicin in broiler chicken tissues (including muscle, liver, and fat). Recoveries from fortified tissue homogenates at levels of 30.0-120.0 microg kg(-)(1) ranged from 76.4 to 107.5% with coefficients of variation of 3.8-16.4%. The limits of detection were 1.0 ng g(-)(1) in muscle, 2.8 ng g(-)(1) in liver, and 1.5 ng g(-)(1) in fat. The ELISA results from the analysis of incurred residue in tissue samples showed the cleanup procedure is viable.     

Some principles of microbiological turbidimetric assays of antibiotics.

Turbidimetric methods for determining the potency of antibiotics are inherently more accurate and more precise than are comparable agar diffusion procedures, but assays conducted in liquid media are subject to degradation from less than ideal conditions to a much greater extent than are diffusion methods. The relationships between test organisms, antibiotics, and assay concentrations are discussed. A valid assay procedure must produce a linear response with an adequate slope (-0.4 to -1.2) by the test organism to increasing concentrations of drug; such linear response normally occurs over a limited range of concentrations. Criteria used to select photometers that offer the greatest advantages to analytical microbiologists are described, with guidelines for the most effective use of the chosen instrument.     

Determination of 17alpha-methyltestosterone in muscle tissues of tilapia, rainbow trout, and salmon using liquid chromatography-tandem mass spectrometry

An analytical method was developed to quantitate and confirm the presence of 17alpha-methyltestosterone in the muscles of tilapia, rainbow trout, and salmon. The method employed two liquid-liquid partitioning steps and two solid-phase extraction columns for sample cleanup. The final extracts were analyzed on an isocratic reverse-phase liquid chromatography-tandem mass spectrometry system with atmospheric-pressure chemical ionization in the positive ion mode. The method was validated at levels from 0.40 to 1.6 ng/g, with MT-d3 used as an internal standard. The accuracy was between 100% and 110%, and coefficients of variation of <10% were obtained for all three fish species. Muscle tissues from dosed fish were also assayed to demonstrate the effectiveness of the method for recovering the parent drug.     

Strengthening Analytical Support in Agricultural Research

The need for analytical support in agricultural research and development has long been recognized, especially for soil fertility evaluation and management, assessment of crop and food quality, and selection and breeding of nutritious food staples. In addition, the demand for analytical research support in the general areas of agriculture interfacing with human health and environmental quality has greatly increased in recent years. The trend for increased demand for analytical support will most likely continue in the future. To meet such diverse, increasing demands for analytical support, we need to upgrade infrastructure facilities and simultaneously teach and train students and young researchers in the use of modern analytical tools. This is prerequisite to providing timely, efficient, and effective analytical support, as such support is the key to monitoring, assessing, and maintaining soil, food, and environmental quality and to breeding nutritious food staples.     

Application of analytical standards in method development: selected chlorinated phenols and herbicides

Pure analytical standards are key components in the successful development of accurate analytical methods. When such compounds are unavailable commercially, a laboratory synthesis activity can provide such materials for use in method development. An example of such an approach is the synthesis of ethyl ethers of chlorinated phenols and ethyl esters of several phenoxy herbicides. Individual synthesis steps and the characterization of such materials are described. The use of such analytical standards in method development is vital for defining method characteristics. In addition, such materials are helpful in diagnosing chromatographic and mass spectral problems in the course of this work. Key mass spectral information including parent and daughter scans obtained from these analytical standards by using tandem mass spectrometry provide the basis for a new analytical method with increased sensitivity and specificity.     

土壤水下渗解析解与数值解的比较研究

针对饱和—非饱和条件下土壤水的垂向下渗,分别用半经验计算公式和全物理基础的HYDRUS模型模拟了不同降雨情景下的土壤水渗漏量,对两种方法的计算结果进行了比较。结果表明,两种方法均能反映出土壤水渗漏率与降雨强度的相关性,降雨强度和降雨总量的增加引起土壤水渗漏总量的增加。在较小雨强条件下,公式计算土壤水渗漏总量稍大于HYDRUS模型计算,雨强较大时则相反。两种方法的计算结果在渗漏率峰值的出现时间和土层底部初始出流时间上存在差异。当土层厚度减小时,半经验解析式的计算精度有所提高,在使用该解析式时,建议对土壤层分层计算,可以提高计算精度。     

处理土壤水垂直不饱和流问题的一种坐标变换方法

尽管土壤水不饱和流问题的数值求解已经广泛地被采用,但要了解土壤水不饱和运动的内在机理,解析解仍然是无法被取代的。由于土壤水不饱和流的非线性使得解析解的获得非常困难,特别是当考虑重力作用的不饱和流问题时,情况将变得更加复杂。所以直到目前,人们还没有得到考虑重力作用下的不饱和流方程的完整的解析解。本文提出了一种坐标变换方法,将重力作用下的不饱和流方程变成了与无重力作用的不饱和流方程完全相同的形式,进而首次获得了该问题的一个可用初等函数表达的解析解。本文所提出的坐标变换方法和所获得的解析解在实验上都得到了较好的验证。     

Quantitative analysis of acrolein in heated vegetable oils by liquid chromatography with pulsed electrochemical detection

A sensitive and selective analytical method for the determination of acrolein in heated vegetable oils by liquid chromatographic separation with pulsed electrochemical detection is described. An optimized triple-step pulsed waveform, based on the formation/inhibition of PtOH species on the electrode surface, a consequence of the absence/presence of adsorbing analytes, is described for the sensitive detection of acrolein in acidic medium. Under these optimized experimental conditions the proposed analytical method allowed detection limits of 0.15 microM without pre- or postcolumn derivatization or tedious cleanup procedures. The proposed analytical method was successfully employed for the sensitive determination of acrolein in fresh and heated vegetable oils with good mean recoveries, selectivity, and analytical reproducibility.     

A sensitive method for detection of sulfamethazine and N4-acetylsulfamethazine residues in environmental samples using solid phase immunoextraction coupled with MALDI-TOF MS

Sulfamethazine (SMT) and its major metabolite, N(4)-acetylsulfamethazine (NA-SMT), were each recovered from spiked water (0.1 ppb) and 10% (w/v) aqueous suspensions of soil (1 ppb) or composted manure (1 ppb), by using a three-stage solid phase immunoextraction (SPIE) system, followed by detection with matrix-assisted laser/desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS). Sulfonamide recovery rates are reported for separate stages of the SPIE system and for trace-level sulfonamide SPIE extraction from the environmental samples. SPIE MALDI-TOF MS is a rapid and definitive technique with potentially better efficiency relative to other established trace-level sulfonamide analytical methods. SPIE MALDI-TOF MS required 1.5 h per batch (8-24 samples/batch) for sample enrichment, 5 min per batch for probe preparation, and 5 min per sample to acquire and process the spectrum. This is the first time MALDI-TOF MS has been reported as a potential means of detecting trace-level drug residues in complex environmental samples.     

Measurement uncertainty associated with sample processing of oranges and tomatoes for pesticide residue analysis

The homogeneity of analytical samples and the stability of pesticides during the sample processing of oranges and tomatoes were evaluated. The mean concentrations of 14C-labeled chlorpyrifos in analytical portions (subsamples) after processing show that homogeneity is dependent on sample type as well as the processing procedure. The homogeneity of analytical samples of tomatoes processed cryogenically was much better than those processed at ambient temperature. For tomatoes, the minimum analytical portion masses required for between-analytical portion variation of < 0.3 Ho were 110 and 5 g for processing at ambient and cryogenic temperatures, respectively. Results for orange showed that analytical portion sizes of 5 g provided sufficient homogeneity from both sample processing procedures. Assessments of pesticide stability demonstrated that most were relatively stable during processing at either ambient or cryogenic temperatures. However, some pesticides, including dichlofluanid, chlorothalonil, tolylfluanid, and dicloran, appeared to suffer much greater losses (>20%) during processing at ambient temperature. For these analytes, loss is interpreted as chemical degradation.     

Regulatory perspective of pesticide analytical enforcement methodology in the United States

A critical overview is presented of the current regulatory problems encountered by the U.S. Environmental Protection Agency in evaluating the adequacy of pesticide analytical enforcement methodologies submitted in support of proposed pesticide tolerances. One of these problems is the development and validation of appropriate, adequate enforcement analytical methods which account for all free or bound/conjugated residue components of the "total toxic residue" in the commodities of concern. Also included is a detailed discussion of suggested improvements in the development and validation of these enforcement methods, for example, integrating radiolabeled metabolism studies with the subsequent development and validation of proposed analytical enforcement methodologies. New procedures are proposed to facilitate the availability of analytical methods to enforcement agencies and other organizations during the method validation process. Future initiatives to use the collaborative study process in the development and validation of Pesticide Analytical Manual, Volume 2, enforcement methods for contemporary pesticides are also discussed.     

计算喷雾干燥塔直径和高度的解析法

为了改进图解积分法要反复查列线图的繁琐过程及克服该法不能编程计算的困难，提出了计算喷雾干燥塔直径和高度的一种新方法——解析法。采用解析法导出了过渡区(喷雾干燥大部分情况均落在此区间)计算雾滴水平飞翔距离和时间、雾滴减速运动垂直下降距离和时间的解析式，还导出了层流区、湍流区计算雾滴运动距离的解析式。利用这些解析式结合已报道的层流区及湍流区计算雾滴运动时间的有关解析式即可用解析法求出喷雾干燥塔的直径和高度。算例表明，解析法比图解积分法简便、准确，解析法手算或计算机编程计算均很方便、计算精度可以满足工程设计要求。     

Analytical methods assessment for exchangeable cations analysis in soil: MIP OES appraisement

ABSTRACT

Soil monitoring and research often requires a comparison of laboratory data generated by diverse instruments and in different laboratories to demonstrate the reliability and accuracy of the results. The outcomes of this work highlight a performance comparison among different analytical methods for the determination of calcium (Ca), magnesium (Mg), sodium (Na), and potassium (K), in soil. Five soil samples were used for analytical methods comparison, corresponding to an argentine agricultural soil interlaboratory, and four soil samples from the Pampa region of Argentina were used for analytical application of the instrumental methods. The results obtained with flame atomic absorption and emission spectrometry (FAAS-FAES) and microwave-induced plasma optical emission spectrometry (MIP OES) were compared to those obtained by conventional analytical methods as complexometric titration and flame photometry. As there were no significant differences between classical methods with instrumental ones, FAAS-FAES and MIP OES were validated following criteria based on international guidelines. Accuracy, precision, linearity, limits of detection and quantification, sensitivity, analytical sensitivity, and working range were evaluated. The results established the satisfactory performance of FAAS-FAES and MIP OES for exchangeable cations. MIP OES is an efficient alternative to FAAS-FAES, with wide linear dynamic range, which is advantageous concerning to the concentrations in which these exchangeable cations are found in soils, avoiding sample dilutions. The most remarkable advantage of MIP OES is the low running costs as it does not use flammable and toxic gases. Due to its benefits MIP OES could be recommended as the main analytical method for exchangeable cations determination.     

Trace metal speciation in natural waters: Computational vs. analytical

Improvements in the field sampling, preservation, and determination of trace metals in natural waters have made many analyses more reliable and less affected by contamination. The speciation of trace metals, however, remains controversial. Chemical model speciation calculations do not necessarily agree with voltammetric, ion exchange, potentiometric, or other analytical speciation techniques. When metal-organic complexes are important, model calculations are not usually helpful and on-site analytical separations are essential. Many analytical speciation techniques have serious interferences and only work well for a limited subset of water types and compositions. A combined approach to the evaluation of speciation could greatly reduce these uncertainties. The approach proposed would be to (1) compare and contrast different analytical techniques with each other and with computed speciation, (2) compare computed trace metal speciation with reliable measurements of solubility, potentiometry, and mean activity coefficients, and (3) compare different model calculations with each other for the same set of water analyses, especially where supplementary data on speciation already exist. A comparison and critique of analytical with chemical model speciation for a range of water samples would delineate the useful range and limitations of these different approaches to speciation. Both model calculations and analytical determinations have useful and different constraints on the range of possible speciation such that they can provide much better insight into speciation when used together. Major discrepancies in the thermodynamic databases of speciation models can be evaluated with the aid of analytical speciation, and when the thermodynamic models are highly consistent and reliable, the sources of error in the analytical speciation can be evaluated. Major thermodynamic discrepancies also can be evaluated by simulating solubility and activity coefficient data and testing various chemical models for their range of applicability. Until a comparative approach such as this is taken, trace metal speciation will remain highly uncertain and controversial.     

Pathology: studies of chronic toxicity and carcinogenicity.

Safety evaluation of chemicals in use or destined for use by humans is a complex endeavor which requires accurate analytical chemical results, extensive animal studies, and thoughtful interpretation of the data. Especially difficult are attempts to extrapolate the animal data to man. The analytical chemist can base many of his conclusions on data concerning quantity; the toxicologist cannot. The analytical chemist works very hard for an answer, but when he gets it, his task is usually completed. When the toxicologist gets an answer from a given experiment, his problems have just started; he must attempt to interpret the data and, even more difficult, to extrapolate the results of animal data to man. Thus, accurate analysis of chemicals and trace substances in biological tissues form the foundation of the work of the toxicologist. A closer association between analytical chemists and toxicologists should prove beneficial to both and to the progress of science.     

分析技术在土壤微塑料研究中的应用现状

微塑料污染已成为环境领域研究的热点问题。受采样、前处理和分析技术的限制,现有研究中检测到的微塑料尺寸普遍较大。定量分析技术不够成熟,文献数据之间的可比性较差。复杂组分和表面附着物导致土壤微塑料的分析检测存在更大的挑战。为更好地掌握研究现状与发展趋势,本文从光谱分析、热分析、显微分析等角度分类,对土壤微塑料研究中的分析技术进行了解析、对比和总结。光谱分析对微塑料进行定性和数量统计,常见的有傅里叶变换红外光谱法和拉曼光谱法。热分析用于组分鉴定和质量分析,具体分为裂解气质联用和热重波谱联用。显微分析则对形貌和尺寸进行表征,包括光学显微镜和电子显微镜两种。提出微塑料分析技术越来越丰富,但是针对土壤微塑料的分析是一项复杂的工作。分析技术的标准化是评价和治理微塑料污染的关键;现有的土壤微塑料检测方法各有利弊。组合或联用技术的使用有望更高效、精准地实现对土壤微塑料定性定量分析;应从需要解决的科学问题出发,根据研究目的合理选择分析技术;部分分析技术在土壤微塑料的实际测定有待于进一步的探索与验证。