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An evaluation was made of 8 atomic absorption systems for the determination of lead in capillary blood in order to determine their suitability for the routine analysis of 100 specimens per day. The precision of results obtained with the Delves cup or tantalum ribbon was better than that with the graphite crucible. Using the Delves cup, results with the filter paper disc technique were higher and less precise than those with liquid blood samples. Other systematic differences in accuracy between methods were found which could not be related to either instrumental configuration or sample form.

A simple technique is described for drying sera on washed, dry sand or ordinary sugar cubes for the sero-diagnosis of leptospirosis. The results are shown to be very similar to those obtained with fluid sera or sera dried on filter paper discs. Sera adsorbed on sand or absorbed in sugar eliminated some of the problems associated with sera dried on paper. This method is suitable for use in the field and is expected to be of value in epizootiological studies where contamination and chemical denaturation of fluid serum samples held without refrigeration is a problem.

A study of the forward collection efficiencies of paper-coated glass and copper cylinders (diameters of 7.5 and 4.0 cm) was conducted in a wind tunnel in which the flow was turbulent. Dibutyl phthalate droplets of MMD 1.3 microns were collected in air-flow velocities of 16.8, 12, and 8.3 mph. Deposition by inertial impaction was precluded by selection of these particle sizes, wind velocity, and cylinder size. The forward collection efficiencies were less than 1% in all cases (greater for the paper-coated glass cylinders than for the paper-coated copper). In general, the forward collection efficiency increased with the reciprocal of the cylinder diameter and was greater at 16.8 mph than at 12.0 and 8.3 mph. At the turbulence intensities used in this work (0.5%, 1.8%, and 4.7%), intensity of turbulence had no effect on forward collection efficiency.

Two major improvements on a high voltage paper electrophoresis apparatus are described. Special tinned brass radiator plates have been very effective for cooling the system. Multichambered electrolyte vessels have facilitated the separation of various biological mixtures at several pH's in a single run at room temperature.

IPC-1478 filter paper efficiency was evaluated using polystyrene latex and dioctyl phthalate (DOP aerosols). Efficiency was measured as a function of particle size, filtration velocity, and filter mass loading. Experimental results of 0.557-µm and larger particle sizes indicate that this medium has limited effectiveness under high-velocity and high-loading conditions. Differences in efficiency were observed when this medium was tested with solid and liquid aerosols.

The effect of Millipore filtration on four methods of bilirubin determination in amniotic fluid was investigated. Millipore filtration is unacceptable as a method of amniotic fluid clarification when the methods of Ovenstone and Connon6 or Fleming and Woolf5 are used. Results obtained from the methods of Liley1 and Freda2 were not much affected by this type of filtration.

Cernik, A. A., and Sayers, M. H. P. (1971). Brit. J. industr. Med., 28, 392-398. Determination of lead in capillary blood using a paper punched disc atomic absorption technique. Application to the supervision of lead workers. The presence of lead in blood is the most incontrovertible evidence of absorption but hitherto the need for venepuncture has limited its determination in the supervision of industrial workers. Micro-methods using atomic absorption spectrophotometry (AAS) have, however, made possible the development of a sufficiently reliable test using a drop of blood obtainable by ear prick for use in the field for screening purposes. A micro-sampling method by AAS is compared with a routine polarographic procedure (POL) using venous blood (corr. coeff. = 0·990). The pipetting of microlitres of blood can be eliminated by spotting the blood onto filter paper, allowing it to dry in air, and then using a punched-out standard disc of dried blood for analysis instead. Correlation of this method (PD) with the micro-sampling technique (AAS) is good (r=0·981). The PD method using capillary blood also correlates acceptably with the micromethod using venous blood (r = 0·913). A pilot field study using capillary blood estimated by the PD technique showed that with this method blood can be collected by ear prick in factories for monitoring workers in the lead industry, thus eliminating the need for routine venepuncture.

(1955). A New Method for Determination of Bacterial Sensitivity to Chemotherapeutic Agents by Means of Paper Strips. Scandinavian Journal of Clinical and Laboratory Investigation: Vol. 7, No. 3, pp. 259-263.

✓ A simple membrane filter technique is described for the collection and demonstration of exfoliated neoplastic cells in the cerebrospinal fluid (CSF). Abnormal cells were demonstrated in 30 cases: in four of these the diagnosis of a benign intracranial tumor was possible. Using this technique, it appears that cells from the majority of neoplasms in contact with the CSF will be demonstrable. This new technique is superior in many ways to the conventional concentration methods of centrifugation, flocculation, sedimentation, or filtration now used. The primary advantages are the simplicity, the bedside availability, the ability to reuse the filtered fluid for additional studies, the preservation of the cells for later analysis should a cytological laboratory not be immediately available, and, of primary importance, the excellent preservation of cellular morphology.

Concentrations of toxic metals can be determined in a drop of blood, such as might be obtained from a finger-prick, by spotting the blood onto filter paper, drying it, and then burning a standard size disc punched from the filter paper in an atomic absorption spectrophotometer. Results for lead, cadmium and zinc determined in this manner compare favorably with accepted macro-methods of analysis. The advantages of this procedure, namely the ease of specimen collection and the simplicity of the analysis, may make this the method of choice in biochemical monitoring for trace metal absorption by workers.

Homogeneous suspensions of streptomycete spores were desirable for plating after mutagenesis. Filtration through 8-μm membrane filters (Millipore Corp.) more effectively separated hyphae and spore clumps from single spores than did filtration through cotton wefts or paper.

FILTER paper is frequently used as a means of supporting radioactive substances, such as proteins or the effluent from a column, for counting in liquid scintillation counters. While this is satisfactory for most isotopes in common use, the efficiency of counting tritium is undesirably low, being a fraction of the efficiency obtainable with tritiated toluene. Glass fibre paper, however, has been found to allow a much higher counting efficiency, approaching the theoretical maximum.

Eighteen acidic and neutral organic compounds were studied for adsorption onto Filter I (MF-Millipore filter) with a diameter of 17.5 mm. The adsorption after filtration of 3 ml. of solution ranged from zero to almost 100%. The adsorption to Filter II (Whatman filter), however, was much lower and in some cases negligible. The water-soluble or ionic forms of compounds are less adsorbed. The extent of adsorption for each compound might depend on its concentration, filtration rate, volume of solution filtered, and Filter I size used. The adsorption was found to be reversible and could be represented by the Freundlich adsorption isotherm equation. The water-soluble impurities from both types of filters were also studied. Their absorbances below 230 mμ were considerably high. The implication of adsorption and impurities from filters on quantitative-qualitative chemical analysis was discussed.

AN automatic scanning technique employing a Geiger–Muller tube for the location and estimation of radioactive substances separated on unidimensional paper chromatograms has been described1. The application of this technique to two-dimensional chromatograms is tedious because a large sheet of paper has first to be cut up into the equivalent number of unidimensional strips and each strip scanned separately. To obviate this difficulty, an alternative technique to the conventional form of two-dimensional paper chromatography has been successfully developed for the application of two or more solvent systems to the same labelled mixture.

RECENTLY, it has been obvious that in most biological materials N-acetylsialic acid (N-acetyl-neuraminic acid) and N-glycolloylsialic acid occur together. By the introduction of a micromethod for the determination of glycollic acid, Klenk and Uhlenbruck1 have made possible the evaluation of the amount of N-glycolloylsialic acid in isolated sialic acids. In search of a more direct method, we tried partition chromatography, employing the solvent systems previously used for the separation of sialic acids but with unfavourable results2,3. As the pK a of sialic acids are low, about pH 2.7, it is necessary to use rather a strong acid in the solvents to prevent the dissociation of the carboxylic group. Of the different acids tried, only trichloracetic acid and hydrochloric acid were suitable. On crystallization of the sialic acids we had observed that N-glycolloylsialic acid was much more insoluble in alcohols than N-acetylsialic acid. Therefore, we tried mixtures of alcohols with the acids mentioned above. The best results were obtained with n-butanol/n-propanol/ 0.1 N hydrochloric acid (1:2:1, v/v). In this solvent the R F values were for N-acetylsialic acid 0.45, and for N-glycolloylsialic acid 0.34, on Whatman paper No. 1. The solvent system applied cannot be used for the separation of diacetylsialic acids and is unsuitable for the separation of free acids and the methyl esters of the sialic acids.