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PubMed1986

Pattern recognition used to investigate multivariate data in analytical chemistry.

Pattern recognition and allied multivariate methods provide an approach to the interpretation of the multivariate data often encountered in analytical chemistry. Widely used methods include mapping and display, discriminant development, clustering, and modeling. Each has been applied to a variety of chemical problems, and examples are given. The results of two recent studies are shown, a classification of subjects as normal or cystic fibrosis heterozygotes and simulation of chemical shifts of carbon-13 nuclear magnetic resonance spectra by linear model equations.

Carbon Radioisotopes↗
PubMed1998

The accuracy of laboratory measurements in clinical chemistry: a study of 11 routine chemistry analytes in the College of American Pathologists Chemistry Survey with fresh frozen serum, definitive methods, and reference methods.

CONTEXT: Better procedures are needed whereby national proficiency testing survey providers can assess and improve the accuracy of laboratory measurements in clinical chemistry. SETTING: The 1994 College of American Pathologists Comprehensive Chemistry Survey. DESIGN: This study of matrix effects and the accuracy of laboratory measurements for 11 analytes linked the logistics of the Survey to definitive methods at the National Institutes of Standards and Technology, reference methods at the Centers for Disease Control and Prevention, proficiency testing materials, and a fresh frozen serum sample. The data were analyzed with a statistical model of laboratory measurements. RESULTS: (1) Matrix biases affected the results reported from 69% of the 644 peer group/survey specimen pairs evaluated. (2) Because of matrix biases, the reference value was the correct target value only 32% of the time; thus, the traceability established by definitive method and reference method value assignments on Chemistry Survey specimens did not assure accuracy on patient samples. (3) In contrast to matrix biases, the error caused by random matrix effects with proficiency testing samples was about the same as that caused by random specimen effects with fresh frozen serum, and both were less than within-run random analytic error. (4) Calibration biases occurred in 73% of the 180 peer groups evaluated, and, after matrix biases were removed, the total variance of interlaboratory measurements was due to peer group calibration bias (48%), within-peer-group random calibration error (31 %), within-run random error (14%), and random specimen effects (7%). CONCLUSIONS: An opportunity exists to improve method calibration accuracy in clinical chemistry. With improved design, national proficiency testing surveys can monitor and help reduce method calibration error by converting reported survey results to a true accuracy base that predicts accuracy on patient samples. For medical purposes, the correct target values on artificial (matrix-modified) chemistry materials are reference values adjusted for the matrix bias of each peer group. Matrix biases estimated by the use of fresh frozen serum can be used as factors to transfer the accuracy of definitive methods from artificial reference materials to patient samples.

Bias↗
PubMedDate not supplied

Involvement of analytical chemistry in chemical speciation of metals in clinical samples.

The different chemical species of the trace elements in a living system are determinants for their physiological behaviour. Their study is necessary to improve the understanding of trace element kinetics and metabolism. In a complex matrix, such as biological fluids and tissues, some trace elements will occur as free or mononuclear ions; other as low molecular weight complexes, as reversible or irreversible macromolecular complexes. Speciation investigations entail the separation of the compounds, followed by the measurement of the trace element in the different fractions. Frame-work-procedures are outlined and attention is drawn on the many difficulties that can be encountered. These include the complexity of the matrix, insufficient specificity of the separation of biocompounds, fortuitous contaminations with trace elements, and cutting the original metal-protein binding. State of the art description is given for the speciation studies of AI, As, Cd, Cr, Co, Cu, Hg, Ni, Pb, Pt, Se, Sn, and Zn.

Aluminum↗
PubMed2005

DNA microarrays: is there a role for analytical chemistry?

DNA microarrays, or "DNA chips", represent a relatively new technology that is having a profound impact on biology and medicine, yet analytical research into this area is somewhat sparse. This article presents an overview of DNA microarrays and their application to gene expression analysis from the perspective of analytical chemistry, treating aspects of array platforms, measurement, image analysis, experimental design, normalization, and data analysis. Typical approaches are described and unresolved issues are discussed, with a view to identifying some of the contributions that might be made by analytical chemists.

Animals↗
PubMed1986

Immunoassays in environmental analytical chemistry.

A review is presented which summarizes the recent developments of immunoassays in environmental analytical chemistry. The basic principle of the method and the following steps in the development of an immunoassay procedure are discussed in detail: Synthesis of the immunogen, immunization procedure, synthesis of the labelled antigen (tracer), advantages and drawbacks of radioimmunoassay, fluoroimmunoassay and enzyme immunoassay. A special emphasis is put on approved methods which can be applied in almost any analytical laboratory. Numerous examples of immunoassays for different pesticides and pollutants (dioxins, polychlorinated biphenyls, mycotoxins) are presented. Besides the respective test features, their applicability for residue determinations in biological samples is kept in the foreground. The advantages and drawbacks of the immunoassays are discussed in comparison with conventional analytical methods. An outlook to future application fields for immunoassays and new trends (e.g. the utilization of monoclonal antibodies) is presented.

Environmental Pollutants↗
PubMed2001

[Methods, developments and applications of circular dichroism and simultaneous dual CD/UV spectroscopy in analytical chemistry].

Circular dichroism (CD) is one of the few sensitive indicators of molecular configuration. CD spectroscopy has therefore long been used for structure elucidation. Recent trends show, however, an enormous progress of CD spectroscopy in analytical chemistry, either as an independent method, or as a detector in hyphenated separation techniques. Its uses became especially widespread in pharmaceutical analyses, since enantiomeric purity is a crucial criterion of drug quality. Objectives of the present Ph.D. work included fundamental research in CD and related methodologies, but also, its applications in pharmaceutical analysis. A technical prerequisite of our research work was the instrumental hyphenation of separation and chiroptical detection techniques, which has been achieved by the combination of high performance liquid chromatographic and circular dichroism spectroscopic devices. Our home-built apparatus was the first HPLC-CD instrument in Hungary. Its uses allowed the elaboration of a new method for the determination of peak homogeneity, which applies simultaneous, dual CD/UV detection, and a subsequent ratio-formation. An improved version of this method resulted in the deconvolution of overlapping chromatographic peaks. Another type of peak homogeneity control method was elaborated by rapid, on-line recording of CD spectra in the progress of elution, in order to analyse apparently homogeneous peaks. Circular dichroism has also been applied to quantitate enantiomeric purity in composite samples without any separation of the analytes, and also, to determine equilibrium constants of protonating chiral compounds.

Chemistry, Analytic↗
PubMed2000

Use of weighted least-squares splines for calibration in analytical chemistry

Weighted least-squares spline functions are discussed and applied for calibration processes in analytical chemistry. Different weighting techniques are also considered, and for the evaluation of the results some quality coefficients are proposed. Depending upon the structure of the data, some weighting procedures may improve the results dramatically. Considering the results obtained in the case of TLC densitometry, it seems that nonlinear weighting procedures based upon the distance to the function are the best ones, with a plus for the y-distance type. It is difficult to give general rules regarding the optimal parameters of the weighted calibration splines-function order (m), number (N) and distribution of knots, and weighting technique. These depend upon the structure of the data. However, higher order splines are not recommended since the result might become extremely unstable. The example used to illustrate the performances of the procedures discussed here involved only a single independent variable. The method is general and extends practically to any number of variables, thus resulting in a multivariate approach.

Journal Article↗
PubMed1993

Reference intervals for 21 clinical chemistry analytes in arterial and venous umbilical cord blood.

Reference intervals were determined for 21 clinical chemistry analytes in umbilical cord arterial and venous blood from healthy term infants. Nonparametric analysis (rank number) was used to determine the central 95% reference interval. No significant differences were observed between male and female infants. Reference intervals for glucose, urea, creatinine, urate, phosphate, calcium, albumin, total protein, cholesterol, triglycerides, alkaline phosphatase, alanine aminotransferase, aspartate aminotransferase, creatine kinase, lactate dehydrogenase, gamma-glutamyltransferase, and magnesium all were significantly different from adult values.

Blood Chemical Analysis↗
PubMed1997

Reference values of common blood chemistry analytes in healthy population of Rawalpindi-Islamabad area.

The reference values of common blood chemistry analytes in healthy population, aged newborn to 80 years, of Rawalpindi Islamabad area were determined at AFIP, Rawalpindi. A total of 2115 healthy subjects, 1206 males and 909 females, were included in the study. Plasma glucose was analysed by GOD/POD, serum cholesterol by CHOD/PAP, triglycerides by GPO/PAP, urea by urease/GLDH, creatinine by Jaffe' rate reaction, uric acid by uricase, total bilirubin by Jendrassik and Grof, total protein by biuret, alanine transaminase (ALT) by optimized IFCC and alkaline phosphatase (AP) by optimized DGKC method. The between batch CVs of all the parameters were within acceptable quality goals. The reference values were calculated using 2.5 and 97.5 percentiles as lower and upper limits (95% CI). In healthy adult males the reference values were: fasting plasma glucose, 3.6-6.0 mmol/l; serum cholesterol; 3.2-6.6 mmol/l; triglycerides, 0.6-2.3 mmol/l; urea, 2.8-6.4 mmol/l; creatinine, 65-132 umol/l; uric acid, 164-430 umol/l; total bilirubin, 5-18 umol/l; total protein, 57-83 g/l; ALT, 15-45 U/l and AP, 185-620 U/l. The values in adult females, children and elderly subjects were slightly different than adult males. The reference values of our population show mild to moderate differences from the other Asian, European and American populations. It is recommended that reference values of different biochemical investigations should be established in various areas of Pakistan to make appropriate use of such investigations.

Adolescent↗
PubMed2004

Micro parallel liquid chromatography: enabling technology for discovery analytical chemistry.

Since the introduction of combinatorial chemistry, compound libraries have undergone a significant increase in size and diversity. The ensuing expansion and diversification of compound libraries have resulted in increased demand for analytical throughput. Following the evolution of new technologies for generating lead compounds and targets and the desire to increase research and development productivity, analytical chemistry is now gaining attention as a bottleneck that would benefit from advances in instrumentation for increased analytical throughput. The commercial introduction of the Veloce trade mark micro parallel liquid chromatography system from Nanostream offers discovery analytical chemists the capability to analyze 24 samples in parallel with as little as 0.5 microl of sample. The system offers a scalable analytical approach to address bottlenecks in historically underserved areas, such as compound library purity screening, as well as higher value-added applications, such as log P determination and aqueous solubility assessment. This article describes the Veloce system and presents representative data from several discovery analytical applications.

Chemistry Techniques, Analytical↗
PubMed1999

Utilization of enzyme-substrate interactions in analytical chemistry.

Enzymes are capable of a highly specific interaction with a variety of substances including their respective substrates. This review summarizes how such interactions may be used in analytical (bio-)chemistry, e.g., for the elucidation of the binding mechanism, the determination of the binding strength, the carting of the binding site, or the screening of possible substrate/inhibitor molecules. Possible assay formats such as analytical affinity chromatography, affinity capillary electrophoresis (ACE), conventional affinity gel electrophoresis (AEP), and related techniques are discussed together with examples of recent applications. In addition a brief section on enzyme-substrate reactions as tools in analytical chemistry is included, since these are perhaps even more important to analytical (bio-)chemistry. The development and application of bioanalytical systems and especially biosensors in various fields including medicine, biotechnology, agriculture, defense and foodstuffs are considered.

Electrophoresis↗
PubMed1997

Effects of hemolysis on serum chemistry analytes in ratites.

Since hemolysis has been a common problem in submitted ratite serum samples, a study was performed to determine interference by hemolysates. Nine chemistry analytes including glucose, total protein, albumin, creatine kinase (CK), gamma-glutamyl transferase (GGT), aspartate aminotransferase (AS7), calcium (Ca), phosphorus, and uric acid were evaluated on a wet reagent analyzer (Ciba Corning Express 550) and on a dry slide reagent analyzer (VetTest 8008). In emus, increasing hemoglobin concentrations increased total protein, albumin, and CK for both analyzers. With increasing hemoglobin concentrations, the Ciba Corning 550 analyte values were increased for AST, Ca, and uric acid and decreased for glucose and phosphorus, the opposite effect was seen in values from the VetTest 8008. GGT levels were variable or sometimes undetectable. Changes in ostrich analytes with hemolysis were similar to emus using the same analyzer. The effects of serum hemolysis often differed in magnitude and direction between the two chemistry analyzers. Interferographs were constructed to aid in rapid assessment of the effects of hemolysis on submitted serum samples.

Journal Article↗
PubMed1989

Biological variability of 26 clinical chemistry analytes in elderly people.

Analytical, within-subject, and between-subject components of variation were estimated for 26 clinical chemistry analytes from duplicate analyses of 10 specimens collected from 27 healthy elderly subjects over a period of 20 weeks. Within-subject variations were similar to those generated previously by us in younger subjects. We conclude, therefore, that homeostasis is not compromised by age alone, and biological variability does not increase simply with age. All analytes except serum water had marked individuality, showing that conventional population-based reference values are of limited utility. The critical differences required for two results to be significantly (P less than or equal to 0.05) changed are not the same as those that prompt action by clinicians. Although heterogeneity of within-subject variation does exist, we believe that the critical differences generated will be useful in routine clinical decision making.

Adult↗
PubMedDate not supplied

Publication speed in analytical chemistry journals.

Variations of the time elapsing between submission or acceptance and publication ("lapse time") of papers have been studied for 10 major analytical chemistry journals, for the 1985-1999 period. The time from receipt of all manuscripts up to their publication and the period between their acceptance and their publication were analyzed in four selected years: 1985, 1990, 1995, and 1999. The majority of the investigated journals showed good average performance with sometimes disturbing fluctuations. Talanta has not been able to catch up with the rest, while the Analyst has recently become clear leader in publication speed.

Journal Article↗
PubMed2002

The role of Raman spectroscopy in the analytical chemistry of potable water.

Advances in instrumentation are making Raman spectroscopy the tool of choice for an increasing number of chemical applications. For example, many recalcitrant industrial process monitoring problems have been solved in recent years with in-line Raman spectrometers. Raman is attractive for these applications for many reasons, including remote non-invasive sampling, minimal sample preparation and tolerance of water. To a lesser extent, Raman spectroscopy is beginning to play a significant role in environmental analysis for the same reasons. At present, the environmental applications typically apply only to the most contaminated situations due to the still relatively high limits of detection. However, some emerging sampling technologies hold out the promise that Raman may soon be more widely applicable to the analytical chemistry of potable water. Herein we discuss these recent advances, summarize some examples of environmental applications to aqueous systems and suggest avenues of future developments that we expect to be most useful for potable water analysis. Also, a simplified, but detailed, theory of normal Raman scattering is presented. While resonance-enhanced Raman spectroscopy, surface-enhanced Raman spectroscopy and non-linear Raman techniques are briefly discussed, their theories and instrumental configurations are not addressed. Also, this article deals primarily with the modern dispersive Raman experiment (as opposed to the Fourier transform Raman experiment), because it seems most suited for potable water analysis. The goal of this article is to give the environmental scientist with no specialized knowledge of the topic just enough theory and background to evaluate the utility of this rapidly developing analytical tool.

Chemistry Techniques, Analytical↗