Analysis of precision of activation analysis method

The precision of an activation analysis method prescribes the estimation of the precision of a single analytical result. The adequacy of these estimates to account for the observed variation between duplicate results from the analysis of different samples and materials, is tested by the statistic T, which is shown to be approximated by a chi-squared distribution. Application of this test to the results of determinations of manganese in human serum by a method of established precision, led to the detection of airborne pollution of the serum during the sampling process. The subsequent improvement in sampling conditions was shown to give not only increased precision, but also improved accuracy of the results.     

Quality control of sampling: proof of concept

Quality control in sampling has been demonstrated as practicable in sampling procedures that require the combination of sample increments to form a composite sample. The proposed method requires no sampling resources or use of time beyond those normally used. Increments are allocated at random into two half-sized composites, each of which is analysed separately. The absolute difference between the two results is plotted on a one-sided control chart, which is interpreted like a Shewhart chart. In commonly prevailing circumstances the analytical precision is negligible and the chart represents sampling precision alone.     

新的脉冲进样AAS法测定“麻杏石甘汤”中的微量金属元素

本文研制了一种新的脉冲进样装置，用于火娄原子吸收分光光度法测定中药煎剂中的Ｃａ，Ｍｇ，Ｆｅ，Ｍｎ，Ｚｎ五种金属元素含量，实验表明，利用此种装置可以同时获得两种进样方式的分析结果，线性范围比常规法宽两倍，耗样量，精密度及分析速度均优于常规法。     

Bipolar pulse conductometric detection of enzyme reactions in flow-injection systems Urea in serum and urine

Conductometric monitoring of enzymatic reactions in a flow-injection system is described. Two conductance cells are used and the responses are manipulated automatically to provide a differential signal. The hydrolysis of urea, catalyzed by urease, is used as an example to illustrate the technique. Blood serum and urine control standards are used to assess the precision and accuracy. The conductometric method is shown to be equal to, or better than existing methods for urea with regard to detection limits (0.1 mM in urine, 0.01 mM in serum), working range, precision (3% RSD), accuracy, and sample preparation. The method has a sample throughput of 20 h^?1.     

Automated continuous-flow determinations of serum proteins by pulse polarography

A new flow-through cell is described for application of the dropping mercury electrode to the determination of serum proteins in an automated continuous-flow system. By using differential pulse polarography with short controlled drop times, it is possible to run a rapid automated system at sampling rates of up to 120 per hour with approximately +/- 1% precision and less than 3% carry-over. With the Brdicka reagent, hexa-amminecobalt(III) chloride, various serum proteins can be determined in the range 5-50 mug/ml. The method therefore offers a rapid and sensitive automated procedure for determination of serum proteins.     

微流动注射进样-加热雾室-等离子体质谱测定血清中的铂

开发了一种基于雾化室加热的微流动注射进样系统,并用于血清中Pt的测定。该进样系统由微量毛细管雾化器、加热微型雾化室、八通道十六孔多功能旋转阀、蠕动泵和注射泵组成。研究了雾化室尺寸、加热温度和采样环体积对信号强度的影响。当雾化室内径为9 mm、加热段长度为6 cm,雾化室温度90 ℃,采样环体积为5 μL时,195Pt的信号强度提高了2.31倍,同时信号精密度从5.1%降至2.2%,并得到峰形良好的信号峰。该进样系统的试样消耗小、灵敏度和检出限均优于常规进样系统。10次测定10 μg/L的Pt标准溶液和血清样品溶液,峰高的RSD分别为2.9%和3.3%。该进样系统测得10个血清中的Pt含量与常规进样系统的测试结果无显著差异,在样品量稀少的情况下具有良好的应用价值。     

Standard operation protocol for analysis of lipid hydroperoxides in human serum using a fully automated method based on solid-phase extraction and liquid chromatography-mass spectrometry in selected reaction monitoring

Standard operating procedures (SOPs) are of paramount importance in the analytical field to ensure the reproducibility of the results obtained among laboratories. SOPs gain special interest when the aim is the analysis of potentially unstable compounds. An SOP for analysis of lipid hydroperoxides (HpETEs) is here reported after optimization of the critical steps to be considered in their analysis in human serum from sampling to final analysis. The method is based on automated hyphenation between solid-phase extraction (SPE) and liquid chromatography-mass spectrometry (LC-MS). The developed research involves: (i) optimization of the SPE and LC-MS steps with a proper synchronization; (ii) validation of the method-viz. accuracy study (estimated as 86.4% as minimum value), evaluation of sensitivity and precision, which ranged from 2.5 to 7.0 ng/mL (0.25-0.70 ng on column) as quantification limit and precision below 13.2%), and robustness study (reusability of the cartridge for 5 times without affecting the accuracy and precision of the method); (iii) stability study, involving freeze-thaw stability, short-term and long-term stability and stock solution stability tests. The results thus obtained allow minimizing both random and systematic variation of the metabolic profiles of the target compounds by correct application of the established protocol.     

Determination of trace elements in plant materials by slurry sampling graphite furnace AAS — some analytical problems

Summary The analytical conditions of cadmium, lead, nickel and cobalt determination in plant material by slurry sampling graphite furnace atomic absorption spectrometry (GFAAS) are presented. The results of stability tests for slurries prepared in different ways are also shown. The ratio of the amount of analyte found in the liquid phase to the total amount of analyte in the slurries is investigated. The determination results are calculated from aqueous standard calibration graphs (cobalt and nickel) or by the standard addition method (cadmium and lead). Statistical evaluation of the results from the certified materials indicate that the slurry method is both accurate and comparable in precision to the conventional wet-ashing procedure.Presented at the 5th International Colloquium on Solid Sampling, with Atomic Spectroscopy, May 18–20, 1992; Geel, Belgium. Papers edited by R. F. M. Herber, Amsterdam     

渐进取样法及其应用

提出了渐进取样法,通过样本数目的累积,使总方差估计值达到所需的精度。应用Ｍｏｎｔｅ Ｃａｒｌｏ模拟技术考察了满足一定取样精度的样本数目及其偏差。将该方法应用于散装生铁块中Ｓｉ、Ｍｎ、Ｃ、Ｓ、Ｐ含量分析的取样,结果令人满意。该项研究对于大宗货物的实际随机取样具有重要参考价值。     

Uncertainty of sampling in chemical analysis

 Uncertainty of sampling is the contribution from sampling errors to the combined uncertainty associated with an analytical measurement when the measurand is the concentration of the analyte in the 'target', the total bulk of material that the sample is meant to represent. Of the errors considered to contribute to uncertainty, random errors of sampling, characterised by precision, are much more accessible to investigation than those due to bias. Where an approximation to random sampling can be achieved, realistic precisions can normally be estimated. In some instances reproducibility precision is significantly greater than repeatability precision, and the contribution of between-sampler variations to sampling uncertainty must be acknowledged. However, the collaborative trial of a sampling method is an expensive and difficult exercise to execute. A system of internal quality control for routine sampling can be introduced. Fitness for purpose has been defined in terms of the required combined uncertainty of sampling and analysis. Received: 4 November 1997 · Accepted: 26 November 1997     

Sensitive determination of the phosphodiesterase III/IV inhibitor zardaverine in human serum by direct sample injection, automated precolumn clean-up and high-performance liquid chromatography.

A high-performance liquid chromatographic method is described for the determination of the phosphodiesterase III/IV inhibitor zardaverine in serum by using fully automated clean-up of large-volume serum samples on a semi-preparative-scale precolumn followed by chromatography on two analytical columns operated with two different solvent systems. The switching of the analytical columns provides the necessary specificity and sufficient sensitivity for UV detection is obtained by the sample volume. The method was shown to give nearly quantitative recovery, allowing the use of external standard quantification. Good precision and linearity within the concentration range 1-50 ng/ml could be demonstrated. The method is suitable for routine measurements in support of kinetic studies of zardaverine in man.     

Uncertainty in analyte mass for samples containing small numbers of particles.

A sampling equation was derived that relates the standard deviation in analyte mass to the number of particles in the sample, the fractions of the different types of particles in the mixture and the masses and analyte concentrations of the individual particles. The equation, which is applicable to samples containing any number of particles, was verified by sampling and analysis of two cereal grain mixtures for manganese, potassium, chlorine and magnesium, and by Monte Carlo computer simulation. Comparison of the sampling precision of analyte mass with the analytical measurement precision was also studied, and it was shown that use of the equation allows the calculation of the minimum number of particles required to hold the sampling relative standard deviation to that of the analytical measurement.     

Comparison of denuder and impinger sampling for determination of gaseous toluene diisocyanate (TDI)

An air-sampling method employing denuders coated inside with a chemisorptive stationary phase has been evaluated for analysis of the hazardous gaseous 2,4 and 2,6 isomers of toluene diisocyanate (TDI). The denuder stationary phase consisted of polydimethylsiloxane (SE-30) to which dibutylamine (DBA) was added as a reagent for derivatization of TDI. The accuracy and precision of sampling by means of denuders were shown to differ only slightly from those of the established impinger method. The denuder method was, however, also shown to be suitable for long-term measurements (up to 8 h). The limit of determination (LOD) of the method, including LC-APCI-MS-MS analysis, was found to be 1.9 microg m(-3) and 1.2 microg m(-3) for 2,4- and 2,6-TDI, respectively, for short-term measurements (15 min). Significant lower LOD was obtained for long-term measurements. This is well below the Occupational Safety and Health Administration (OSHA) 8-h TWA (time-weighted average) exposure limit, which is 40 microg m(-3) for the sum of the TDI isomers. The denuder method was also found to be robust and easy to handle. The samplers can be prepared several days before sampling with no loss in performance. The contents of denuders should, on the other hand, be extracted immediately after sampling to prevent degradation of the isocyanate derivatives formed.     

Flow Injection Analysis of Glucose in Human Serum by Chemiluminescence

Abstract

Combining the rigidly controlable conditions of Flow Injection Analysis with detection by chemiluminescence, a method for determination of glucose in serum via enzymatic degradation by glucose in serum via enzymatic degradation by glucose oxidase is described. With a Standard deviation of less than 2% the sampling frequency is 75 samples per hour. Results obtained by the proposed procedure are compared with those acquired by a routine AutoAnalyzer method used at a local hospital. It is shown that any influence on the yield of chemiluminescence due to difference in viscosity of the injected samples effectively can be eliminated.     

Flow injection analysis for calcium in serum,water and waste waters by spectrophotometry and by ion-selective electrode

The Flow Injection technique is shown to provide fast, reliable and sensitive methods for the determination of calcium in various aqueous as well as serum samples; spectrophotometric or potentiometric detection can be used. At sampling rates of 100–110 samples per hour, with 30-μl sample injections, high reproducibility of measurement and low reagent consumption are achieved in both methods. In the spectrophotometric method, the analytical readout is available within 12 s after sample injection at a total reagent consumption of 0.75 ml per analysis. The potentiometric measurement of the calcium activity in serum is placed on a reliable basis by alternating measurements of serum samples and aqueous standards without incurring any non-reproducible changes in potential between aqueous and serum solutions. This permits the simultaneous determination of pH and pCa, the analytical readout being available within XXX s of sample injection. The good agreement between the results obtained with the Flow Injection method and those attained by atomic absorption and EDTA titrations as well as pCa stat-measurements show that the new methods are potentially suitable for routine analysis.     

Clinical usefulness of a trypsin radioimmunoassay kit

From the clinical use of RIA-gnost trypsin kit, the following results were obtained. 1. Standard curve showed a steep and good curve was shown. 2. Incubation: The condition for the first incubation was set at the room temperature for 10-24 hours and that for the second incubation at the room temperature for 3-5 hours. With these settings, satisfactory results were obtained. 3. Reproducibility and recovery: The C.V. of the reproducibility and the recovery were considered superior, and the values were below 10% and +/- 3%, respectively. 4. Correlation between trypsin and serum elestase-1: An excellent positive correlation (coefficient of correlation r = 0.889) was shown. 5. Serum trypsin concentration of normal and pancreatic diseases: The normal range was from 100 to 500 ng/ml. Acute pancreatitis rose obviously. Diabetes mellitus and chronic pancreatitis was below 500 ng/ml and the pancreatic cancer showed a tendency to scatter in the range of 50-1,250 ng/ml. The above results indicated that serum trypsin can be easily measured with high precision by using this method. Thus the method is considered useful for the diagnosis of pancreatic diseases.     

Separation of free iodide from other I-species in human serum – Quantification in serum pools and individual samples

A method for the determination of free iodide in human serum has been developed. Iodide from pooled serum samples has been separated from the organic matter by SEC, subsequently freeze-dried and analyzed by ion chromatography. Investigations for recovery and precision have been carried out and provided sufficient results. For quality assurance ICP-MS has been taken additionally as a total I-detector. The iodide results of ICP-MS agree well with IC values. Iodine containing SEC- fractions from iodide-spiked samples has shown no increased I-values except that in the iodide fractions, proving that there has been no iodide conversion into other I-species (and vice versa) during the whole procedure. Free iodide from two serum pools of different healthy persons has been determined as 2.25 and 2.43 microg I(-)/l, respectively. The values are related to total iodine levels determined by ICP-MS. For comparative reasons a table of individual iodine and iodide values is presented.     

GC/MS法测定室内空气中邻苯二甲酸酯类物质

针对室内空气中日益严重的邻苯二甲酸酯类污染,建立了固相萃取柱采样,GC/MS测定室内空气中16种邻苯二甲酸酯类物质的测试方法,可用于评价室内空气质量。