The use of flow-injection analysis for the direct determination of calcium and magnesium in blood serum and plasma is described. An inexpensive rotary valve is used to inject the serum sample (4 microliters) into a flowing non-segmented stream of reagent which carries the sample slug through a long narrow-bore coil--where it gradually disperses--and into the nebuliser of an atomic absorption spectrometer. This on-stream sample dilution removes the need for predilution of the sample. The resulting absorbance signals are recorded as peaks less than 40 seconds after sample injection. Analytical recoveries and precision are good for both elements and the results by flow-injection analysis compare well with established routine methods.

Calcium↗

PubMed1984

Homogeneous fluoroimmunoassay using Lucifer yellow VS: determination of albumin plasma.

Non-separation fluoroimmunoassays are well suited to automation. The potential sensitivity of such assays has not been realised because the most commonly used label (fluorescein) has absorption and emission spectra which coincide with those of blood constituents and because it has a very small Stokes shift. Lucifer yellow VS has a larger Stokes shift than fluorescein and an emission maximum at longer wavelength. We describe an energy transfer fluoroimmunoassay for plasma albumin in which Lucifer yellow VS is used to label albumin and rhodamine B isothiocyanate is used to label anti-albumin antibodies. The assay shows good correlation with a dye-binding method for albumin and has sensitivity and precision which compare favourably with similar assays using a fluorescein label.

Energy Transfer↗

PubMed1984

The design of automated analysis machines.

Since the introduction of the first automatic chemical analysis machine 25 years ago, development has progressed rapidly and a wide range of machines are now available. The original machines were constrained by the available analytical techniques, but later developments in methodology have permitted much more latitude. There are four main groups of machines and these differ markedly in operating principles. In addition there are many unclassifiable devices which have been developed for special purposes. The principles underlying the design of the machines are discussed, and as far as possible an account is given of the steps in development which led to their modern form. The principles of fluid flow, which govern the operation of many of these machines, are considered in some detail. Proposals are made regarding the areas in which new development is possible and desirable in the hope of encouraging further work in this field.

Biomedical Engineering↗

PubMed1983

Serum iron and total iron-binding capacity determination by flow-injection analysis with atomic absorption detection.

The deproteinised sample (150 microliters) is 'injected' into a continuously flowing stream of deionised water which is pumped, via a capillary tube, to the nebuliser of an atomic absorption spectrophotometer. Analytical readout is obtained, in the form of transient peaks, 6 s after sample injection. Before injection traces of haemoglobin are removed from the serum by treatment with trichloroacetic acid-ascorbate solution. This protein precipitant facilitates rapid removal of haemoglobin bound iron without the need for heating. After centrifugation the supernatant solution is introduced into the flowing stream by use of a novel inexpensive 'injector'. Analytical recovery and precision are good, and results compare well with those obtained by a standard AutoAnalyzer procedure.

Autoanalysis↗

PubMed1983

Use of Lucifer yellow VS as a label in fluorescent immunoassays illustrated by the determination of albumin in serum.

The use of a new label for fluoroimmunoassay is described. Lucifer yellow VS is a highly fluorescent vinyl sulphone dye which, under mild conditions, forms covalent bonds with amino and sulphydryl groups but is extremely stable in water. A large Stokes shift (110 nm) and an emission maximum at 540 nm give Lucifer yellow further advantages over the more commonly used labels. The use of the dye as a label has been demonstrated by developing a heterogeneous fluoroimmunoassay for human serum albumin. The fluoroimmunoassay gave comparable results to those obtained using a less specific colorimetric dye-binding assay (r = 0.97, n = 20). The advantages, limitations, and other potential uses of Lucifer yellow are discussed.

Colorimetry↗

PubMed1983

Controlled dispersion analysis: flow-injection analysis without injection.

Flow-injection analysis is a precise, elegant, and economical technique, but its most troublesome feature is the mode of injection of the sample slug. We describe an alternative approach in which the sample is aspirated by the sample probe. In the simplest version the probe normally rests in reagent; when sampling is to take place, the pump is stopped and the probe is transferred to the sample container. The pump makes a predetermined angular movement, the probe is returned to reagent, and the pump is restarted. In more advanced versions the same approach is combined with the merging zone technique. The system is economical, precise, and capable of full automation in a multichannel discretionary analyzer.

Autoanalysis↗

PubMed1982

Zinc and copper determination in microsamples of serum by flow injection and atomic absorption spectroscopy.

A new approach to the direct determination of copper and zinc in serum and plasma is described. The sample is injected into a continuously pumped stream of water which is fed into the nebuliser of an atomic absorption spectrophotometer. Analytical results are obtained as a series of sharp peaks on a chart recorder. Analytical variables have been investigated, and the proposed method gave results comparable to those obtained using a conventional method based on precipitation of serum proteins with trichloroacetic acid. The proposed method takes less time to perform and was found to give more precise results than the conventional method. In addition, the flow injection analysis method can be performed using microsamples (10-100 microliters) and is thus ideally suited for use on children.

Copper↗

PubMed1982

FLow-injection analysis: a new approach to quantitative measurements in clinical chemistry.

Flow-injection analysis, founded on an approach that is entirely different from continuous-flow analysis, involves use of three principles: sample "injection," controlled dispersion of sample (rather than a dispersion retarded with gas bubbles), and reproducible timing. The conditions governing the dispersion of the sample in the flowing carrier stream are considered, and we illustrate how the dispersion can be manipulated to suit particular analytical requirements. Instrumentation and practical aspects of flow-injection analyses are discussed, especially with regard to clinical chemistry applications, and the technique is compared with the more conventional gas-segmented-flow analysis system. We conclude that, because of its speed, economy, and simplicity, flow-injection analysis will eventually replace the gas-segmented approach for many clinical chemistry analyses.

Chemistry, Clinical↗

PubMed1982

Simultaneous enzyme immunoassay of two thyroid hormones.

We describe an enzyme immunoassay in which the two thyroid hormones, triiodothyronine and thyroxin, are measured simultaneously in a single tube. The method involves labeling the two with separate enzymes (beta-galactosidase and alkaline phosphatase, respectively), whose catalyzed reactions can easily be distinguished from each other by absorption spectrophotometry, with o-nitrophenyl-beta-galactoside and phenolphthalein monophosphate as substrates. Performance of this dual assay method compares well with that of conventional single-hapten enzyme-labeled assays, and results compare well with those by two single-hapten radioimmunoassays. The dual assay has certain advantages over single-hapten methods: smaller sample volume, lower reagent cost, and shorter overall assay time. As presented here, the use of enzyme labels to measure two (or more) haptens simultaneously represents a significant advance in the use of immunoassay techniques.

Humans↗

PubMed1982

Direct determination of therapeutic concentrations of lithium in serum by flow-injection analysis with atomic absorption spectroscopic detection.

In this flow-injection system for direct determination of lithium in serum by atomic absorption spectroscopy, the 10-microL sample is manually injected into a continuously flowing non-segmented stream of de-ionized water, which is pumped, via a dispersion tube, to the spectrometer's nebulizer. Controlled dispersion of the sample zone, before it is introduced into the nebulizer, produces the required sample dilution. Effects of varying the length of the dispersion tube, the flow rate, and the sample size were studied. Analytical readout is obtained, in the form of transient peaks, 5 s after sample injection. It is necessary to include physiological concentrations of sodium and potassium in the standard because each of these cations enhances the lithium absorbance signal. Analytical recovery (98.5 to 101%) and CV (about 2%) are good, and results compare well with those obtained by aspiration of prediluted samples (n = 121, r = 0.99).

Chemistry, Clinical↗

PubMed1979

Ileostomy reconstruction.

A study of 47 patients undergoing ileostomy reconstruction is presented. The most common indications were recession (15 patients) and a desire for a continent type of ileostomy (12 patients). Less frequent indications were stenosis (6 patients), parastomal ulceration (6 patients), prolapse (4 patients), unsatisfactory siting (3 patients), and parastomal hernia (1 patient). Refashioning of the ileostomy at the same site was possible in 17 patients, whilst repositioning at a new site was required in 30 cases. In 28 of these laparotomy was carried out to enable repositioning, but in two cases resiting was performed without laparotomy. After the original operation, reconstruction may become necessary at any time from a few months to over 20 years.

Adolescent↗

PubMed1978

Hospital maintenance in developing countries.

Explore the source record for details and available documents.

Africa↗