Separate Calibration Curves Research Articles

Studies on the quantification of specific cyanogens in cassava products and introduction of a new chromogen

AbstractThe enzymic assay for cyanogens in cassava as developed by Cooke (1978) and improved by O'Brien et al (1991), was compared with a standard method, involving autolysis/steam distillation/titration, and further improved with a more acceptable coloration and other minor changes. Cooke's assay, using a linamarin calibration curve, gave similar values for cyanogenic potential in fresh cassava as the standard method. For cassava samples with high non‐glycosidic cyanogen levels, Cooke's assay yielded slightly lower values. Isonicotinate/1,3‐dimethyl barbiturate as reagent in the König reaction had the following advantages compared with the so far applied pyridine/pyrazolone color reagent. It is less toxic and does not release repulsive vapours. It is faster, cheaper and easier to handle, and has increased sensitivity and longer storability. Direct measurement of cyanogenic potential was accurate in extracts containing 35–700 μM. Recovery of linamarin supplements was 102±4%. Separate calibration curves of linamarin, acetone cyanohydrin and KCN were necessary for accurate calculation of cyanogenic glycosides and cyanohydrin levels. Extract storability depended slightly on storage temperature, but was not changed by inclusion of ethanol in the extract medium.

Estimating reactivity of pozzolanic materials by a spectrophotometric method

Following earlier work on estimating the reactivity of pozzolanic materials, three classes of pozzolanas have been further investigated, to ascertain whether or not a more linear calibration curve is possible. A better linear correlation exists when separate calibration curves between absorbance and lime-pozzolana mortar strength values for different classes of pozzolanas are drawn. Pozzolanic activity has been characterized by a parameter called pozzolana reactivity index. Practical aspects and validity of the method are discussed. A good correlation coefficient between absorbance and pozzolana reactivity index values in agreement with lime-pozzolana mortar strength was obtained.

Sensitive method for the determination of daunorubicin and all its known metabolites in plasma and heart by high-performance liquid chromatography with fluorescence detection

The cytostatic agent daunorubicin is effective against leukaemia. An important side-effect is cardiomyopathy, common to all anthracyclines. Since anthracycline metabolites are thought to contribute to the observed cardiotoxicity, a method for the quantitative determination of all metabolites in plasma as well as in tissues is needed as a basis for the further investigation of the correlation between toxicity and the amount of each metabolite formed. Using Sep-Pak C 18 cartridges we were able to extract daunorubicin and its five metabolites, including the aglycones, with recoveries in the range 50–90%. Depending on the chemical properties of each metabolite, fluorescence detection following high-performance liquid chromatographic separation permitted detection limits as low as 0.2–0.9 n M in plasma and 0.8–3·10 −11 mol/g in tissue, at a signal-to-noise ratio of 2, which compare favourably with literature data. The method showed linearity in the ranges 1–250 n M in plasma and 0.04–4.0 nmol/g in tissue ( r ≥ 0.998). The accuracy, determined at 10 and 100 n M for plasma and at 0.1 and 1.0 nmol/g for tissue, was in the range 86–103 and 85–110% for plasma and tissue, respectively. The within-day and between-day repeatability values were acceptable (between 2 and 12%). Because of large inter-compound differences, separate calibration curves were used for each anthracycline. Application of the assay to the analysis of plasma and tissue samples of mice after intravenous injection of daunorubicin proved successful.

Pulsed NMR for Molecular Structure Analysis of EPDM

Abstract The use of pulsed NMR analysis under proper operating conditions has proven to be useful for controlling various polymer compositions in the manufacture of EPDM. It can be used in determining the amount of oil incorporated into oil-extended EPDMs. At higher oil contents, the differences in EPDM properties will affect this test method, which will require a separate calibration curve for each type of polymer. It can be used to measure the propylene content of EPDM. Comparison data have shown that this technique is more accurate in predicting crystallinity or propylene content than the standard IR method within the propylene range of 22 to 41%. Pulsed NMR can also be used to predict uncured EPDM compound tensile strength and EPDM/PP compression-molded tensile strength. Since these properties are affected by the crystallinity of EPDM, of which percent ethylene is the major contributor, then tensile strength can be determined indirectly. Based on the tensile and SER correlation, it seems obvious that this technique is measuring the spin-spin relaxation times of the crystalline phase, whereas the ir method is only measuring propylene content.

Lattice parameter measurement of sub-micron device structures in compound semiconductors via convergent-beam electron diffraction

Convergent-beam electron diffraction (CBED), which is one of the techniques available on a modern transmission electron microscope (TEM), is sensitive to small localized lattice parameter changes and its application is therefore important in the characterization of sub-micron device structures. Unfortunately, dynamical diffraction effects prevent direct extraction of changes in the lattice parameter from CBED patterns which are obtained from high atomic number materials such as compound semiconductors. Therefore, in order to measure the relative lattice mismatch of a quaternary (InGaAsP) device structure grown on InP, we have opted to calibrate the relative position of CBED features with X-ray lattice parameter measurements which were obtained from planar quaternary layers grown on InP substrates. Three parameters from bright-field CBED patterns were measured as a function of the X-ray determined lattice mismatch in order to establish three separate calibration curves. CBED measurements taken from a device structure were found to produce similar values of lattice mismatch when interpreted using the calibration curves. The close correspondence of these three values of the lattice mismatch ((4.541 ± 2.119) × 10 −4, (5.158 ± 2.881) × 10 −1 and (4.819 ± 4.021) × 10 −4), enhances the credibility of this approach for the characterization of sub-micron device structures.

A Rapid EDXRF Method of Simultaneous Quantitative Elemental Analysis Using an Annular Cd-109 Source

Recent EDXRF studies of Chinese ceramics of the Ming (1368–1644) and Qing (1644–1911) dynasties, the Republic period (1912–1939), and the modern period (after World War II) have given encouraging results for the identification of modern fake reproductions and the attribution and dating of Chinese porcelains. However, quantitative elemental determination requires tedious calibration procedures. In general, a separate calibration curve is required for each element to be determined, and, when one is using Cd-109 sources, quantitative elemental determination (say from Mn to Nb) would be rather time-consuming.

Effectiveness of superphosphate and crandallite-millisite rock phosphates on a deep, very sandy soil as assessed by plant growth and soil extractable phosphate

The initial and residual effectiveness of superphosphate, Christmas Island C-grade ore (C-ore) and 500�C heated (calcined) C-ore (Calciphos) was measured on a deep, very sandy soil near Badgingarra, W.A. Different levels of each fertiliser were applied once only in May 1980. Yields of lupins (1980 and 1983) and subterranean clover (1981) were used to determine the effectiveness of the fertilisers, and in 1986 the residual value of the fertilisers was measured for wheat, oats, and barley, relative to freshly applied superphosphate. Samples of the top 10 cm of soil were collected each January-February for soil tests for P which were compared to plant yields measured in the following spring (Aug.-Dec.). Superphosphate was the most effective fertiliser, though its effectiveness declined by about 50% between years 1 and 2, and by a further 25% between years 2 and 4. C-ore was only about one-tenth as effective as superphosphate in the year of application, and its effectiveness declined by about 40% between years 1 and 2, and by a further 15% between years 2 and 4. Calciphos was about one-fifth as effective as superphosphate in the year of application, and its effectiveness declined by about 40% between years 1 and 2, and remained approximately constant between years 2 and 4. In 1986, the effectiveness of 1980 applied superphosphate was between about one-quarter to one-fifth as effective as freshly applied superphosphate for wheat, oats and barley, and the 1980 applied C-ore and Calciphos were about 15% as effective as freshly applied superphosphate. The amount of P extracted by sodium bicarbonate from soil fertilised with superphosphate decreased by about 50% between years 2 and 3, by a further 20% between years 3 and 4, and by a further 15% between years 4 and 7. For soil treated with Calciphos, the amount of extractable P doubled between years 2 and 3 and thereafter remained approximately constant. Very little P was extracted from soil fertilised with C-ore. Separate calibration curves were required in most cases for the relationship between yield and soil test values for superphosphate and rock phosphate in 1981 and 1983, and for each fertiliser and species in 1986. A substantial amount of superphosphate-added P (50-70%) and about 20% of rock phosphate-added P had leached below 50 cm of the topsoil 6 years after application.

Increases in soil water content decrease the residual value of superphosphate

In pot experiments, levels of superphosphate incorporated through the whole soil were incubated for 30 days in 2 lateritic soils from south-western Australia at 1 of the following 5 soil water contents: air-dry for 30 days, at field capacity for 10 or 30 days, and flooded for 10 or 30 days. The soils were then air-dried for 30 days and the residual value of the superphosphate relative to freshly applied superphosphate was measured using 30-day-old triticale (x Triticosecale cv. Tyalla) and wheat (Triticum aestivum cv. Gamenya) plants. Soil samples were collected just before sowing from each pot for measurement of bicarbonate-extractable phosphorus (P) levels which were compared with the DM yield of plant tops. For all treatments there was a common relationship between the P concentration (data not shown) or P content in the tops and the DM yield. This shows that the treatments can be considered as different dilutions of the same fertiliser. Less P was taken up by plants as the moisture content and period of contact with moist soil increased, and this limited yield. The effectiveness of superphosphate incubated in dry soil was similar to the effectiveness of freshly applied superphosphate. Incubation in moist soil reduced the effectiveness of superphosphate for plant growth, by about 50% for soils incubated at field capacity and 70% for flooded incubated soils. As calculated from the P content of plant tops, the effectiveness of superphosphate incubated in dry soil was similar to the effectiveness of freshly applied superphosphate, and the effectiveness of superphosphate decreased by about 55% for soils incubated at field capacity and 75% for flooded incubated soils. The amount of P extracted by sodium bicarbonate from soil sampled just before sowing was also influenced by the incubation treatments, and decreased in the following order: freshly applied = air dry incubated > field capacity incubated > flooded incubated. Thus the bicarbonate-soluble P extracted from the soil qualitatively paralleled the yield results. However, compared with the yield results, the decreases were not as marked. When the bicarbonate-extracted P results were compared with subsequent yields of triticale or wheat, separate calibration curves were required for the different incubation treatments.

Residual value of superphosphate and Queensland rock phosphate for serradella and clover on very sandy soils as assessed by plant growth and bicarbonate-soluble phosphorus

Superphosphate (0-0.4 t/ha P) and Queensland rock phosphate (0-20 t/ha P) were incorporated into the top 10 cm of very sandy soil near Esperance, W.A. The effectiveness of the fertilisers for pastures was calculated from dry herbage yields of yellow serradella, slender serradella and subterranean clover. Soil samples were collected just after fertiliser application and at intervals up to 2.5 years for measurement of bicarbonate-extractable phosphorus (soil test), which was related to plant yield. Results for all 3 species were very similar in response to superphosphate. The effectiveness of superphosphate decreased by about 50% between years 1 and 2, and by a further 25% between years 2 and 3. The effectiveness of Queensland rock phosphate was about 7% that offreshly applied superphosphate in the year of application for all 3 species and for the next 2 years, its effectiveness relative to freshly applied superphosphate remained about constant for yellow serradella and approximately doubled for slender serradella and clover. For superphosphate 2.5 years after application, the amount of phosphorus extracted by the soil test compared with freshly applied superphosphate decreased by about 80%. The soil test extracted a very small proportion of the phosphorus applied as Queensland rock phosphate and the amount extracted decreased by about 50% during 2.5 years. Although the plants responded strongly to increasing levels of applied phosphorus, soil test values remained low until yields of about half the maximum yield were attained. Separate calibration curves were required for each fertiliser and species and each calibration curve was best described by 2 component linear spline functions.

Investigation by pyrolysis—gas chromatography of the composition of multicomponent polymeric mircoheterogeneous systems based on some vinyl monomers

A method for the quantitation of the composition of copolymers of styrene and acrylonitrile, methyl methacrylate and butyl acrylate, filled and unfilled with dispersive silica, including copolymers chemically bound to the filler, has been developed based on pyrolisis—gas chromatography (Py—GC). I7 based on pyrolisi-gas chromatography (Py—GC). It is shown that Py—GC can be used for the determination of the composition of perfluorinated and partially fluorinated copolymers of tetrafluoroethylene having metal oxides as fillers. However, for partially fluorinated copolymers it is necessary to prepare separate calibration curves with due consideration to the catalytic influence of fillers upon thermal degradation. Parameters of the macromolecular structure, R, characterizing the relative contents, of monomeric sequences in the macrochain were determined for the copolymer of tetrafluoroethylene with a relative sta of tetrafluoroethylene with a relative standard deviation not exceeding 0.075.

Optimization of Conditions for Accurate Phosphonate and Total Phosphorus Assay on Lipid Samples, in Conjunction with Thin-Layer Chromatography

The range of inorganic acid normalities for maximum color formation of the phosphomolybdenum- blue complex (under heating) increases by elevating the ammonium molybdate concentration, and at a ratio of molybdate molarity/acid normality equal to 10, there is maximum color development at any acid normality in the range 1-4 ɴ with either HClO4 or H2SO4 (or their mixtures). On the basis of these features a revised method is described for the accurate determination of phosphonate-P percent of total-P. on lipid extracts and on TLC bands. The color at the final step, in both cases, is developed under the same conditions of molybdate, HClO4 and H2SO4 concentrations, thus avoiding possible errors produced by the use of two separate calibration curves.

Quantitative determination of calcite and dolomite in soils by X‐ray diffraction

SUMMARYAn X‐ray diffraction method using CaF2 as internal standard was applied to the carbonate‐rich soils of the ukurova and Göksu plains in Southern Turkey. Soil samples, freed from carbonates, were used as matrices and a separate calibration curve was prepared by known carbonate additions for each soil series. Statistical tests showed that one calibration curve was sufficient to determine calcite and dolomite contents of seven soil series. Particle orientation was an important factor for accurate analyses and a test, using the known addition method, should be carried out before using a matrix material other than carbonate‐free soils.

A SIMPLE VOLUMETRIC INSTRUMENT TO ESTIMATE BIOMASS OF FLUID-PRESERVED INVERTEBRATES

AbstractPlacing preserved animals in the wide arm of a fluid-filled U-shaped open tube provides an accurate linear measure of biomass. Changes in fluid level are monitored by projecting an image of the tube into a dissecting microscope equipped with an ocular micrometer. Precision of the calibration curves is equivalent to length–weight regressions. However, only a single curve need be generated to predict wet weight of many taxa. Separate calibration curves are required to predict dry weights of hard- and soft-bodied taxa. The instrument is not suitable for measuring biomass of living individuals.

DETERMINATION OF ALDICARB SULFONE IN HYDROPONICALLY GROWN CUCUMBERS

During a two week period, several residents of a small Nebraska community experienced violent illnesses with short duration following ingestion of locally grown hydroponic cucumbers (Goes et al. 1979). Approximately a year later during another two week period, a second similar outbreak occurred. In each incident those who ingested hydroponic cucumbers experienced similar illnesses. All of the cucumbers were grown at the same greenhouse. The carbamate insecticide aldicarb, was detected in some cucumbers grown at the hydroponic greenhouse.The aldicarb was determined as aldicarb sulfone (a metabolite) by gas chromatography employing a flame photometric detector (FPD) with a 394 mμ filter selective for sulfur‐containing compounds. Separate calibration curves, derived from aldicarb sulfone, are required for the quantitation.

High precision isotopic ratio analysis of volatile metal chelates

High precision isotope ratio measurements have been made for a series of volatile alkaline earth and transition metal chelates using conventional GC/MS instrumentation. Electron ionization was used for alkaline earth chelates, whereas isobutane chemical ionization was used for transition metal studies. Natural isotopic abundances were determined for a series of Mg, Ca, Cr, Fe, Ni, Cu, Cd, and Zn chelates. Absolute accuracy ranged between 0.01 and 1.19 at. %. Absolute precision ranged between +-0.01-0.27 at. % (RSD +- 0.07-10.26%) for elements that contained as many as eight natural isotopes. Calibration curves were prepared using natural abundance metals and their enriched /sup 50/Cr, /sup 60/Ni, and /sup 65/Cu isotopes covering the range 0.1-1010.7 at. % excess. A separate multiple isotope calibration curve was similarly prepared using enriched /sup 60/Ni (0.02-2.15 at. % excess) and /sup 62/Ni (0.23-18.5 at. % excess). The samples were analyzed by GC/CI/MS. Human plasma, containing enriched /sup 26/Mg and /sup 44/Ca, was analyzed by EI/MS. 1 figure, 5 tables.

Indirect Micro-determination of Primary and Secondary Amines by Copper (II)-catalyzed Oxidation of Pyrocatechol Violet

An indirect method is described for the micro-determination of primary and secondary amines in the presence of tertiary amine by means of a catalytic indicator reaction. The copper bis (dithiocarbamate) complex formed from primary or secondary amine and carbon disulfide in the presence of copper was removed by extraction into chloroform. The remaining copper in aqueous solution was determined by measuring the rate of oxidation of pyrocatechol violet by hydrogen peroxide. A simplified complementary tristimulus colorimetry (SCTS method) was used for determination of the reaction rates, since it has the advantage of permitting accurate determination of the rate constants in the presence of color impurities. Quantitative recoveries were obtained of microamounts of primary and secondary amines with good accuracy (from -2.9% to +2.9% error). The method presented is sensitive and does not require a separate calibration curve for each primary and secondary amine.

Optical probes of membrane potential.

There are two basically different mechanisms for the fluorescence and absorption changes of merocyanine, cyanine and oxonol dyes. The permeant dyes (cyanine and oxonol dyes, with delocalized charges) work by a potential-dependent accumulation mechanism. These dyes show large (up to 80%) fluorescence and absorption changes with suspensions of cells, and the changes are complete in seconds. The impermeant dyes (merocyanine dyes, with localized charges) and the permeant dyes also show optical changes that take place in fractions of milliseconds. The rapid optical changes are relatively small (less than or equal to 5 X 10(-3)) but can often be easily detected in experiments with single cells. The rapid, nonaccumulative, optical changes result from membrane-localized dye movements. Cyanine dye-absorption changes occur because of a potential-dependent partition of dye between the membrane and the adjacent aqueous region at the high dye-concentration side of the membrane. Dimers and larger aggregates are formed in the aqueous region during the change. Merocyanine dyes may also work by the same mechanism. DiS-C3-(5) is presently the best dye for measuring membrane potentials of cells, organelles, and vesicles in suspension, but several other cyanines work nearly as well (P.J. Sims, A.S. Waggoner, C.-H. Wang, J.F. Hoffman, Biochemistry 13:3315, 1974). For each system, the ratio of dye to membrane must be varied until the optimum fluorescence change is found. A separate calibration curve must be obtained for each system. For measuring fluorescence and/or absorption changes in single cells, merocyanine 540 and diBA-C4-(5) work well but produce some photodynamic damage with high intensity illumination. A rhodanine merocyanine (WW-375) gives very large absorption changes and does not damage tissue during strong illumination. As the mechanisms of the optical changes are worked out, it should be possible to design and synthesize more sensitive, less toxic dyes that are easier to calibrate. And, as the mechanisms of the optical changes are worked out, these dyes may be useful for studying the structure and dynamics of excitable membranes.

Comparison of Two Formulations of Acid Orange 12 for the Determination of Protein in Milk

Abstract A new formulation of Acid Orange 12 reagent solution for the determination of protein, using 16.037–16.041, has been tested for linearity of response and dye binding capacity. A total of 13 fluid dairy products and one nonfat dry milk were collaboratively studied by 5 laboratories, each using both the old and the new dye solutions. Separate calibration curves were prepared for each dye solution. Analysis of variance (mixed model) showed that the dye solution and the dye solution × sample interaction were nonsignificant sources of variation. Laboratories were a significant source; the estimated standard deviation due to laboratories was 0.023% protein. It appears that very slight differences in calibration curves exist in the different laboratories, but it is not known whether this is associated with the old or new solutions. The new formulation has been adopted as official first action for use in method 16.037–16.041.

A New Micro-osmometer

This apparatus measures the rate of distillation at room temperature between the unknown solution and a known standard solution under carefully defined conditions. It is calibrated using solutions of known osmotic pressure. It is there fore an empirical vapour-pressure osmometer. The sample (o-o6 ml.) is placed in the capsule C (Fig. i) and the standard solution contained in the pipette P, where it is held at a fixed position due to surface tension at the jet. The upper meniscus is located on the eye-piece scale of the microscope M. The capillary tube above the meniscus and the space inside the screw plunger S are air filled. By turning the screw S the standard solution can be extruded to hang as a drop from the tip of the jet. After a measured time (20 min.) the drop is again drawn into the pipette to the fixed position at which it comes to rest automatically, and the change in volume, due to condensation or evaporation, measured on the microscope scale. If the sample has a surface tension not much lower than that of water, the osmometer can be used in the reverse way, the sample being drawn into the pipette and the standard in the capsule. Used in this way only 0 001 ml. of the sample is needed. A separate calibration curve is required for each standard (Fig. 2) and each standard has a range of about 9 atm. ( A = 0 75o C.). The standard deviation of single determinations is ±0 06 atm. ( A = 0 005° C.). This is uniform over the range investigated (0-28 atm. or i = 2-3° C.). Satisfactory comparisons between the osmometer and the cryoscopic method have been obtained with samples of plant sap (Table I). The osmometer has the advantage of needing only a small volume of solution which can be viscous, opaque, and need not be free from cell debris, &c. It operates at physiological temperatures and needs no very stringent temperature control. It is simple to construct and manipulate and occupies less than 1 hour per deter mination of which only 15 minutes is taken up in operation.

The B.N.F. Jet-Test on Organic Bright Nickel Deposits

SynopsisThe rate of penetration of organic bright nickel deposits in the B.N.F. jet-test is shown to vary with the thickness of the deposit. Therefore, to determine thickness by this method it is necessary to use a calibration curve relating apparent and true thickness. Although minor variations in plating conditions have little effect, separate calibration curves are required for deposits from different proprietary solutions and there is some evidence that differences can arise between individual baths of nominally the same type. Unless the calibration can be checked on deposits from a given bath, it is therefore recommended that the jet test on organic bright nickel deposits be used primarily as an acceptance test of the “limit” type.