SERUM TRIIODOTHYRONINE DETERMINATION BY SATURATION ANALYSIS

1973 ◽  
Vol 72 (4) ◽  
pp. 714-726 ◽  
Author(s):  
A. Burger ◽  
B. Miller ◽  
C. Sakoloff ◽  
M. B. Vallotton
Keyword(s):  
Ionic Strength ◽  
Limit Of Detection ◽  
Improved Method ◽  
Accuracy Of Measurement ◽  
Tracer Amount ◽  
The Mean ◽  
Physiological Values ◽  
Hyperthyroid Patients ◽  
Solvent Blank

ABSTRACT An improved method for the determination of serum triiodothyronine (T3) has been developed. After addition of a tracer amount of the hormone, T3 was extracted from 1 ml serum under conditions of pH and ionic strength which favoured T3 extraction (89%) over thyroxine (T4) extraction (58%). Chromatography of the extracted material on Sephadex LH-20 separated T3 completely from residual T4. The T3 eluate was dried, then re-dissolved in 0.5 ml NaOH 0.04 n. To 0.2 ml duplicate aliquots, a standard amount of TBG was added for the competitive protein analysis. After one hour incubation at 4°C, separation of bound from free T3 was achieved on small Sephadex G-25 columns. Overall recovery was 67 ± 10.8% and correction for the loss was made. The solvent blank was 37 ± 27 (sd) ng/100 ml. Accuracy of measurement of known quantities of T3 added to serum was 98.4%. The coefficient of variation within the assay was 6.2% and between the assays it was 11.4%. The limit of detection (0.1 ng) corresponded to a concentration of 25 ng/100 ml. T4 added to serum did not interfere with T3 determination until high non-physiological values were reached. The mean ± sd serum T3 in 54 euthyroid subjects was 153 ± 58 ng/100 ml and in 24 hyperthyroid patients it was 428 ±186 ng/100 ml; 4 out of the 24 hyperthyroid values were within 2 sd of the mean euthyroid group. All the values found in the euthyroid group were well above the limit of detection of the method.

scholarly journals An Improved Method for Analysis of Cholecalciferol-Treated Baits

1999 ◽  
Vol 82 (4) ◽  
pp. 792-798
Author(s):  
Richard E Mauldin ◽  
John J Johnston ◽  
Craig A Riekena
Keyword(s):  
Extraction Method ◽  
Limit Of Detection ◽  
Rapid Determination ◽  
Liquid Extraction ◽  
Detector Response ◽  
Improved Method ◽  
Standard Curve ◽  
Time Periods ◽  
Precision And Accuracy

Abstract A liquid extraction method is described that permits rapid determination of cholecalciferol (D3) in rodenticidal grain baits. Purified D3 was incubated for various time periods to produce pre-D3. Response ratios (concentration/detector response) for various concentrations of pre-D3 and D3 in solutions permitted generation of a correction factor for direct quantitation of pre-D3 in solutions with a pure D3 standard. The method has equal precision and accuracy, yet is simpler and less time consuming and requires less solvents than widely accepted methods for extracting D3 from grain baits. Recoveries from control oat baits fortified at 0.05 and 0.75 wt% were 100.9 and 98%, respectively. A standard curve for concentrations ranging from 6.4 to 204 μg/mL had an r2 of 0.9999 and an intercept of zero and was linear and proportional. The method limit of detection was 2.0 × 10−4 wt % D3.

scholarly journals Sensitive Determination of Terazosin in Pharmaceutical Formulations and Biological Samples by Ionic-Liquid Microextraction Prior to Spectrofluorimetry

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
Mohsen Zeeb ◽  
Mahdi Sadeghi
Keyword(s):  
Ionic Liquid ◽  
Ionic Strength ◽  
Biological Samples ◽  
Limit Of Detection ◽  
Pharmaceutical Formulations ◽  
Experimental Conditions ◽  
Relative Standard ◽  
Common Ion ◽  
Liquid Microextraction

An efficient and environmentally friendly sample preparation method based on the application of hydrophobic 1-Hexylpyridinium hexafluorophosphate [Hpy][PF6] ionic liquid (IL) as a microextraction solvent was proposed to preconcentrate terazosin. The performance of the microextraction method was improved by introducing a common ion of pyridinium IL into the sample solution. Due to the presence of the common ion, the solubility of IL significantly decreased. As a result, the phase separation successfully occurred even at high ionic strength, and the volume of the settled IL-phase was not influenced by variations in the ionic strength (up to 30% w/v). After preconcentration step, the enriched phase was introduced to the spectrofluorimeter for the determination of terazosin. The obtained results revealed that this system did not suffer from the limitations of that in conventional ionic-liquid microextraction. Under optimum experimental conditions, the proposed method provided a limit of detection (LOD) of 0.027 μg L−1and a relative standard deviation (R.S.D.) of 2.4%. The present method was successfully applied to terazosin determination in actual pharmaceutical formulations and biological samples. Considering the large variety of ionic liquids, the proposed microextraction method earns many merits, and will present a wide application in the future.

scholarly journals Occurrence of aflatoxins in peanuts and peanut products determined by liquid chromatography with fluorescence detection

2013 ◽  
pp. 27-35 ◽  
Author(s):  
Biljana Stojanovska-Dimzoska ◽  
Zehra Hajrulai-Musliu ◽  
Elizabeta Dimitrieska-Stojkovic ◽  
Risto Uzunov ◽  
Pavle Sekulovski
Keyword(s):  
Liquid Chromatography ◽  
Fluorescence Detection ◽  
Limit Of Detection ◽  
Total Content ◽  
Immunoaffinity Column ◽  
Limit Of Quantification ◽  
Three Samples ◽  
The Mean ◽  
Positive Results

Liquid chromatography with fluorescence detection using immunoaffinity column clean-up was a method described for determination of aflatoxins (AFB1, AFB2, AFG1 and AFG2) in peanuts and peanut based products. The validation of the procedure was performed. Good coefficient of correlation was found for all aflatoxins in the range of 0.9993-0.9999. Limit of detection (LOD) and limit of quantification (LOQ) ranged from 0.003-0.005 mg/kg and 0.009-0.023 mg/kg, respectively, which was acceptable. The mean recovery for total aflatoxins was 88.21%. The method also showed acceptable precision values in the range of 0.171-2.626% at proposed concentration levels for all four aflatoxins. RSDR values (within laboratory reproducibility) calculated from the results showed good correlation between two analysts for all aflatoxins and they ranged from 4.93-11.87%. The developed method was applied for the determination of aflatoxins in 27 samples of peanuts and peanut based products. The results showed that 21 peanut samples (77.7%) were below LOD of the method. Three samples had positive results over the MRL. There was one extreme value recorded for the total aflatoxins in peanut (289.2 mg/kg) and two peanut based products, peanut snack and peanut, with total content of aflatoxins being 16.3 mg/kg and 8.0 mg/kg, respectively. The obtained results demonstrated that the procedure was suitable for the de?termination of aflatoxins in peanuts and peanut based products and it could be implemented for the routine analysis.

Gas Chromatographic Determination of Polychlorinated Biphenyls in Mussels from Galicia, Spain

1994 ◽  
Vol 77 (4) ◽  
pp. 985-988 ◽  
Author(s):  
Elena Alvarez Piñeiro ◽  
Jesus Simal Lozano ◽  
Asuncion Lage Yusty
Keyword(s):  
Environmental Protection Agency ◽  
Mytilus Galloprovincialis ◽  
Capillary Column ◽  
Polychlorinated Biphenyl ◽  
Limit Of Detection ◽  
Chromatographic Determination ◽  
Method Performance ◽  
The Mean ◽  
Gas Chromatographic Method

Abstract We have modified a standard capillary column gas chromatographic method (U.S. Environmental Protection Agency No. 505) for the determination of polychlorinated biphenyl (PCB) residues and applied the technique to mussels (Mytilus galloprovincialis) from Galicia, Spain. During the purification step, SepPak Florisil minicolumns are used instead of conventional columns. Method performance is good (limit of detection, 0.032 μg/kg; recovery, 99%; method precision as coefficient of variation among 10 samples, 2.5%), and compared with the standard method, less eluant is required and analysis is faster. The mean PCB content of 107 mussels collected from various points on the coast of Galicia was 113 μg/kg.

Therapeutic Monitoring of Anticonvulsant Drugs: Gas-Chromatographic Simultaneous Determination of Primidone, Phenylethylmalonamide, Carbamazepine, and Diphenylhydantoin

1975 ◽  
Vol 21 (11) ◽  
pp. 1658-1662 ◽  
Author(s):  
Charles J Least ◽  
George F Johnson ◽  
Harvey M Solomon
Keyword(s):  
Simultaneous Determination ◽  
Standard Method ◽  
Chromatographic Method ◽  
Limit Of Detection ◽  
Internal Standard ◽  
Normal Serum ◽  
Therapeutic Monitoring ◽  
The Mean ◽  
Gas Chromatographic Method

Abstract We describe a sensitive and precise gas-chromatographic method in which benzylmalonate methylester monoamide is used as the internal standard for the simultaneous determination of primidone, phenylethylmalonamide, carbamazepine, and diphenylhydantoin. The trimethylsilyl derivatives of the anticonvulsants are well separated from each other and from normal serum constituents. The lower limit of detection for each drug is 0.5 mg/liter when 1 ml of serum is analyzed. Withinrun precision (CV), established by analysis of 10 replicates, was as follows: primidone (5.4 mg/liter), 2.6%; phenylethylmalonamide (5.5 mg/liter), 1.6%; diphenylhydantoin (6.6 mg/liter), 3.8%; and carbamazepine (10.4 mg/liter), 3.2%. Fifty specimens were analyzed for primidone and 35 for diphenylhydantoin by a standard gas-chromatographic method involving on-column methylation and by the procedure we have developed. The mean value observed for primidone with the on-column alkylation procedure was 9.3 mg/liter and with our procedure was 9.6 mg/liter. When values for our assay were regressed against values for the standard method, the slope of the least-squares line was 0.936, the intercept was 1.00 mg/liter, and r was 0.939. The mean values observed for diphenylhydantoin by on-column methylation and with our procedure were both 12.6 mg/liter. When values for our assay were regressed against the standard method, the slope of the leastsquares line was 0.944, the intercept was 0.3 mg/liter, and r was 0.988

scholarly journals Analytical evaluation of Kone Microlyte determination of ionized magnesium

1994 ◽  
Vol 40 (1) ◽  
pp. 52-55 ◽  
Author(s):  
H E van Ingen ◽  
H J Huijgen ◽  
W T Kok ◽  
G T Sanders
Keyword(s):  
Limit Of Detection ◽  
Analytical Evaluation ◽  
High Concentration ◽  
Serum Samples ◽  
Ionized Magnesium ◽  
Carrier Liquid ◽  
The Mean ◽  
High Concentration Range ◽  
Induced Changes

Abstract We performed an analytical evaluation of a commercially available instrument for determining ionized magnesium through use of a neutral carrier, liquid-membrane-based ion-selective electrode. Reproducibility (CV 2-4%), linearity (0.30-2.50 mmol/L), lower limit of detection (0.30 mmol/L), and absence of interference from Ca2+ indicate adequate performance for measuring ionized magnesium in plasma or serum samples in the normal to high-concentration range. Sodium in excess of 150 mmol/L caused a negative bias, which can be explained by ionic strength-induced changes in activity coefficients. The use of heparin as an anticoagulant must be restricted to concentrations < 15 units/mL because of the binding of magnesium to heparin. The mean +/- SD concentration of ionized magnesium and its fraction of total magnesium in 76 healthy volunteers were 0.56 +/- 0.05 mmol/L and 0.65 +/- 0.04, respectively.

scholarly journals Application of ion pair complexes to design novel potentiometric membrane sensors for direct determination of frusemide in pharmaceuticals

2020 ◽  
Vol 6 (1) ◽  
Author(s):  
Nagaraju Rajendraprasad ◽  
Kanakapura Basavaiah
Keyword(s):  
Limit Of Detection ◽  
Direct Determination ◽  
Standard Addition ◽  
Ion Pair ◽  
Bromocresol Green ◽  
Bromophenol Blue ◽  
Experimental Parameters ◽  
The Mean

Abstract Background Fabrication of two membrane sensors using two acidic indicators among sulphonthalein dyes, namely bromophenol blue (BPB) and bromocresol green (BCG), and their use as indicative electrodes for the quantification of frusemide (FUR) is presented. The ion pair complexes of FUR with BPB or BCG are used to prepare the membranes in THF solvent, PVC matrix and dibutyl phthalate (DBP) as plasticizer and subsequently to fabricate FUR-BPB (Sensor I) and FUR-BCG (Sensor II) sensors. Results Sensors I and II are employable to determine 2.4 × 10-5–2.4 × 10-3 mol/L FUR at operative pH of 3.71. The calibration curve between the potentials against the concentration of FUR yielded the slopes of 58.73 ± 1 and 57.66 ± 1 mV/decade, respectively, using Sensors I and II, and this confirmed the Nernstian behaviour. Satisfactory correlation was obtained between the measured potentials and FUR concentration with the proposed sensors, and this was revealed by regression coefficient values of 0.9987 and 0.9980 for Sensors I and II, respectively. The LOD (limit of detection) values were calculated and reported for both the sensors. The experimental parameters were optimised to yield acceptable characteristics of both the sensors in the context of performance. The role of excipients of tablets and interferences were assessed by standard addition protocol. The obtained results confirmed the ineffective role of excipients of tablets and foreign species used as interferents. Conclusion The designed sensors were validated to confirm the accurate, precise, robust and rugged functioning in determining FUR. The mean of recovered FUR, close to 100%, revealed the acceptable and effective functioning of the proposed sensors. Excellent results were obtained by FUR tablets’ analysis using both the sensors.

scholarly journals Desarrollo de un Método para la Especiación de Selenio en Muestras de Cerveza

2018 ◽  
Vol 3 (1) ◽  
pp. 1
Author(s):  
Marinela Colina ◽  
Jennifer Smith ◽  
Gilberto Colina ◽  
Brinolfo Montilla
Keyword(s):  
Total Mercury ◽  
Limit Of Detection ◽  
Total Concentration ◽  
Chemical Species ◽  
Control Population ◽  
Limit Of Quantification ◽  
Palabras Clave ◽  
Icp Ms ◽  
The Mean

Se desarrolló un método por cromatografía iónica (CI) para la especiación de selenio en muestras líquidas de cerveza, empleando H2O2 y luz UV como sistema oxidante. Las especies aniónicas de selenio fueron separadas utilizando una columna aniónica AS4A y un guarda columna AG4 Dionex, la fase móvil empleada fue de 1,7 mM NaHCO3/1,8 mMNa2CO3, para la cuantificación se empleó un detector de conductividad iónica. El tiempo de retención del ión Se(IV) fue de 7,8 min y para Se(VI) de 15,7 min. Los límites de detección obtenidos para Se(IV) y Se(VI) fueron de 0,15 y 0,28 mgL-1, respectivamente. Se establecieron las condiciones óptimas de análisis del proceso de oxidación de los compuestos puros de selenio: selenito y selenio-DL- metionina, mediante el estudio de diferentes parámetros como cantidad de peróxido adicionado, tiempo de digestión y pH. La separación de los iones Se(IV) y Se(VI) en muestras de cerveza se realizó empleando una fase móvil de 2,0 mM de carbonato de sodio y 1,0 mM de hidróxido de sodio, ésta mezcla separa los iones de selenio sin tener problemas de interferencias de nitrato, fosfato y sulfato. Los límites de detección determinados para Se(IV) y Se(VI) fueron 0,08 y 0,07 mgL-1, respectivamente. El método desarrollado se comparó con un método referencial ICP AES, obteniéndose excelentes resultados. Palabras clave: Especiación, selenio, cerveza, cromatografía iónica.    ABSTRACT In this work, analytical methodologies were developed for the determination of mercury levels in blood and plasma samples of patients with leukemia registered at the Haematological Institute of the West, Maracaibo, evaluating the total concentration of Hg and its chemical species in blood samples from the patients studied (n = 34) and of control subjects (n = 5), by the HPLC-ICP-MS. The calculated limit of detection found for the determination of Hg in blood and plasma was 1.39 μg Hg/L and the limit of quantification was 1.39 μg Hg.L-1. The total mercury concentrations in blood and plasma of 16.89±8.76 μg Hg.L-1 [8.22-45 μg Hg.L-1] and 25.77±5.12 μg Hg.L-1 [10.6-40.87μg Hg.L-1] respectively and for the control population were 25.3637±11.4 [10.6-40.87 μg Hg.L-1] and 74.46±16.09 [64.38-102.82 μg Hg.L-1]. The mean of Hg-S of the group of males evaluated was 16.08±7.85 µg Hg.L-1, and in females were 18.68±10.05 μg.L-1, the mean of Hg-S in the females was significantly higher (P <0.05) than the mean Hg-S observed. The detection limits for the Hg chemical species studied in blood are: Hg+ (0,7 µg Hg.L-1), Hg+2 (0,53 µg Hg.L-1). The concentrations found for Hg+2 and CH3Hg+ in leukemia patients in blood and plasma were 8.16±1.67 [6.96-10.97], 9.85±6.22 μg Hg+2.L-1 [6.04-20.74], and 11.47±4.33 μg Hg+2.L-1 [7.28-18.63], 11.28±5.40 [6.24-18.63] respectively, while for the control population were 10.04±3.84 μg Hg+2.L-1 [5.41-15.86], 12.24±5.76 [6.00-21.37] and 33,48±8.62 μg Hg+2.L-1 [27.59-48.36], 28.44±13.13 [18.25-50.23].  Key words: leukemia, mercury, blood, plasma.

scholarly journals II. On the application of the conversion of chlorates and nitrates into chlorides, and of chlorides into nitrates, to the determination of several equivalent numbers

1839 ◽  
Vol 129 ◽  
pp. 13-33 ◽  
Keyword(s):  
Hydrochloric Acid ◽  
Nitrous Acid ◽  
The Other ◽  
Improved Method ◽  
Whole Numbers ◽  
The Mean ◽  
The One

1. The following researches originated from some experiments which were undertaken to discover an improved method for ascertaining the quantity of nitrate of potassa existing in crude saltpetre. After several unsuccessful attempts the action of hydrochloric acid was tried. The fact, that nitrates are decomposed by this acid, has been long known; but the nature of the resulting compound of potassium has not, so far as I am aware, been hitherto determined. I anticipated that the nitrate would be decomposed into chloride of potassium. To decide the question some pure nitrate of potassa was mixed with hydrochloric acid, and the mixture heated; while at common temperatures no perceptible action occurs, but immediately the acid becomes hot, decomposition commences. Chlorine and nitrous acid are evolved with copious effervescence, and the nitrate slowly disappears. The solution was gradually evaporated to dryness, and the dry salt treated with an additional quantity of acid until decomposition was no longer evident. The resulting salt was then carefully examined, and it was found to be pure chloride of potassium. This experiment was repeated several times, and all the results concurred in satisfactorily establishing the fact, that nitrate of potassa may be perfectly converted into chloride of potassium, provided a sufficient quantity of the acid be employed, and the temperature necessary to effect the decomposition be properly regulated. 2. So far the decomposition was admirably adapted for the object mentioned at the commencement. The usual impurities, such as chlorides, sulphates, silica, &c. which any sample of crude saltpetre might contain, would obviously remain unchanged, while the nitrate of potassa alone suffering decomposition, its quantity could easily be ascertained, by comparing the weight of the resulting salt with that obtained from a known quantity of absolutely pure nitrate. Several experiments were therefore performed to determine the exact quantity of chloride of potassium corresponding to a known weight of nitrate. The mean result of four experiments gave the ratio of 100 of nitrate to 73·730 chloride. I was then naturally led to compare this result with the equivalent numbers of these two compounds. In this country there are two series of equivalents in general use, one in which whole numbers are adopted, and the other in which fractional parts are admitted. For example, according to the former, nitrate of potassa will be 102, and to the latter 101·3. So chlo­ride of potassium will be 76 and 74·6. Whence, according to the former, every 100 parts of nitrate should yield 74·51 of chloride: the latter gives the ratio of 100 to 73·613. But these results differ considerably from my experiments. In the one case, we have a difference of ·78, and in the other ·12. Whence therefore could they arise? Either the process must be defective, or the equivalent numbers, so generally considered as correct, must be erroneous.

scholarly journals Homogeneous, Nonradioactive, Enzymatic Assay for Plasma Pyridoxal 5-Phosphate

2002 ◽  
Vol 48 (9) ◽  
pp. 1560-1564 ◽  
Author(s):  
Qinghong Han ◽  
Mingxu Xu ◽  
Li Tang ◽  
Xuezhong Tan ◽  
Xiuying Tan ◽  
...  
Keyword(s):  
Vitamin B6 ◽  
Independent Risk Factor ◽  
Limit Of Detection ◽  
Active Form ◽  
Enzymatic Assay ◽  
Biologically Active ◽  
Radioenzymatic Assay ◽  
The Mean ◽  
American Laboratory

Abstract Background: Pyridoxal 5′-phosphate (PLP) is the biologically active form of vitamin B6. Clinical studies suggest that low PLP concentrations are an independent risk factor for cardiovascular and other diseases. However, PLP concentrations are not routinely diagnosed because of the lack of a homogeneous, nonradioactive assay. We describe a homogeneous, nonradioactive, enzymatic PLP assay that uses the apo form of the PLP-dependent recombinant enzyme, homocysteine-α,γ-lyase (rHCYase). Methods: PLP was removed from holoenzyme rHCYase by incubation with hydroxylamine to obtain apo-rHCYase. The restoration of enzymatic activity by reconstitution of the holoenzyme was linearly related to the amount of PLP bound to the enzyme. The amplification principle of the assay allowed nanomolar concentrations of PLP to be measured by the conversion (by reconstituted holo-rHCYase) of millimolar concentrations of homocysteine to H2S. N,N-Dibutylphenylenediamine (DBPDA) was used for determination of H2S, the combination of which forms a chromophore with high absorbance. The assay was initiated by incubation of 5 μL of plasma with apo-rHCYase in a binding buffer for 60 min at 37 °C. Homocysteine (2.5 mmol/L) was added to the assay buffer and incubated at 37 °C for 20 min. The DBPDA reaction was allowed to progress for 10 min and then read at 675 nm. Results: The PLP enzymatic assay has a lower limit of detection of 5 nmol/L and is linear to 200 nmol/L. The recovery of PLP was 98%. The mean within- and between-run CVs were 9.6% and 12%, respectively. Correlation of 45 samples in the PLP enzymatic assay and the B63H radioenzymatic assay (American Laboratory Products Co., Ltd.) yielded: y = 0.9367x + 10.569 (R2 = 0.9201). Conclusions: This new PLP assay is the first homogeneous, nonradioactive, vitamin B6 diagnostic method. The assay is applicable to chemistry automated analyzers and may have wide clinical use.

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