BIOASSAY OF SEAWATER: I. A 14C UPTAKE METHOD FOR THE DETERMINATION OF CONCENTRATIONS OF VITAMIN B12 IN SEAWATER

1966 ◽  
Vol 12 (1) ◽  
pp. 175-183 ◽  
Author(s):  
A. F. Carlucci ◽  
S. B. Silbernagel
Keyword(s):  
Internal Standard ◽  
Natural Seawater ◽  
Centric Diatom ◽  
Inhibitory Effects ◽  
Internal Standards ◽  
Sterile Medium ◽  
Seawater Samples ◽  
C Assimilation ◽  
Uptake Method

A method is described employing 14CO2 uptake by the marine centric diatom Cyclotella nana (clone 13-1) for the bioassay of vitamin B12 in seawater. Seawater samples were filter sterilized, supplemented with sterile medium constituents, and diluted with a similarly supplemented, charcoal-treated filtered seawater. Samples or diluted samples, internal standards, and external standards were inoculated with the diatom such that the initial concentration of cells was approximately 1 × 104 per milliliter. The bioassay flasks were incubated for 47 hours, 14C as Na214CO2 was added, and 14C assimilation was measured after a 2-hour exposure. The rate of uptake of 14C could be related to B12 concentrations when these were in the range of 0.05 to 3.0 μμg B12 per milliliter. A 49-hour incubation time was selected since cells required time to adapt to seawaters collected from different locations. The concentration of B12 in a seawater sample was calculated from the radiocarbon uptake, the percentage of the internal standard recovered, and the dilution factor. The method is more sensitive than that described by Gold from which it was derived, and takes into account the serious inhibitory effects found in many samples of natural seawater. The limit of sure detection is about 0.05 μμg B12 per ml and the standard deviation of the method was about 0.3 μμg per ml when measuring 1.4 μμg B12 per ml in inhibitory seawater.

BIOASSAY OF SEAWATER: II. METHODS FOR THE DETERMINATION OF CONCENTRATIONS OF DISSOLVED VITAMIN B1 IN SEAWATER

1966 ◽  
Vol 12 (6) ◽  
pp. 1079-1089 ◽  
Author(s):  
A. F. Carlucci ◽  
S. B. Silbernagel
Keyword(s):  
Vitamin B1 ◽  
Vitamin B ◽  
Internal Standards ◽  
Cell Counts ◽  
No Inhibition ◽  
Uptake Rates ◽  
Seawater Samples ◽  
Uptake Method

Methods for the bioassay of seawater for vitamin B1 (thiamine) using the marine chrysomonad, Monochrysis lutheri, are described. Cell counts after a 120-hour incubation or 14C-uptake rates after a 48- or 72-hour incubation were proportional to the vitamin B1 concentrations in seawater. Samples of seawater were supplemented with nutrients, filter-sterilized, and, if necessary, diluted with medium prepared in charcoal-treated seawater. External and internal standards were used. A starved culture of M. lutheri was added and the assay-flasks were incubated in the light for 46 or 70 hours, after which 14C as Na214CO3 was added and its uptake was measured after 2 hours. Cell counts were made after 120 hours. Most of the samples bioassayed to date showed no inhibition to the alga. The range of vitamin B1 concentrations which can be assayed was about 2–35 ng/l by 46-hour preincubation followed by 14C-uptake measurements or by counting cells after 120 hours. The range was extended to 100 ng B1/l after the 70-hour preincubation in the 14C-uptake method. These methods were capable of determining vitamin B1 in seawater at about one-tenth the level reported previously.

A sensitive liquid-chromatographic method for determination of 3'-azido-3'-deoxythymidine (AZT) in plasma and urine.

1988 ◽  
Vol 34 (8) ◽  
pp. 1565-1568 ◽  
Author(s):  
M A Hedaya ◽  
R J Sawchuk
Keyword(s):  
Human Plasma ◽  
Prescription Drugs ◽  
Chromatographic Method ◽  
Internal Standard ◽  
Infectious Complications ◽  
Over The Counter ◽  
Internal Standards ◽  
Liquid Chromatographic Method ◽  
Liquid Chromatographic

Abstract We describe a liquid-chromatographic assay for AZT in human plasma and urine. This assay involves the use of two internal standards, allowing reference of AZT peaks to the appropriate internal standard, the choice depending on the range of concentrations encountered. This method is isocratic, specific, sensitive enough to allow quantification of AZT in concentrations observed clinically, and requires only 13 min of chromatographic time. We saw no interference from various over-the-counter and prescription drugs often used in treating the infectious complications of AIDS.

Quantitative Determination of Chlorpromazine. HC1 in Tablets, Spansules, Injectables, and Bulk Chemical by Nuclear Magnetic Resonance Spectroscopy

1978 ◽  
Vol 61 (1) ◽  
pp. 52-54
Author(s):  
John E Zarembo ◽  
Richard J Warren ◽  
David B Staiger
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Internal Standard ◽  
Resonance Spectroscopy ◽  
Internal Standards ◽  
Tetramethylammonium Bromide ◽  
Bulk Chemical ◽  
Characteristic Signal ◽  
Nuclear Magnetic

Abstract A nuclear magnetic resonance (NMR) procedure is described for the quantitative analysis of chlorpromazine. HC1 in bulk chemical as well as in final dosage forms—tablets, spansules, and injectables. The method is based on measurement of a characteristic signal of chlorpromazine relative to an internal standard. Three different internal standards are specified: Cyclohexane was selected because of the convenience and rapidity with which samples could be prepared for assay. Piperonal was used to verify the method and to show that precision and accuracy were not affected by the volatility of the cyclohexane. Tetramethylammonium bromide was used as an internal standard for Thorazine injectable. No interferences were found from stearates and other tablet excipients. The NMR procedure provides a simple, direct, and specific assay with a precision of ± 1–2%.

Effects of Internal Standards and Peak Profile Functions on Quantitative XRD Phase Analysis of Cement and its Hydrates

2011 ◽  
Vol 492 ◽  
pp. 424-428
Author(s):  
Yong Qi Wei ◽  
Wu Yao ◽  
Wei Wang
Keyword(s):  
Phase Analysis ◽  
Internal Standard ◽  
Direct Determination ◽  
Quantitative Phase Analysis ◽  
X Ray Diffraction ◽  
Profile Function ◽  
Internal Standards ◽  
Refinement Method ◽  
Xrd Phase Analysis

Quantitative X-Ray diffraction (QXRD) combined with the Rietveld refinement method allows direct determination of crystalline phase content of cement and its hydrates. However, relatively precise results need the correction of proper internal standards and the use of matched peak profile functions with masterly refinement strategies. The aim of this paper is to research and discuss effects of these factors on the quantitative phase analysis results. For this purpose, different internal standards and peak profile functions with corresponding refinement strategies were attempted in experiments and refinements. The results indicate that Al2O3as internal standard is more suitable for cement and its hydrates than ZnO, and the better peak profile function is CW function 2 rather than function 3 in GSAS.

Application of Inductively Coupled Plasma/Mass Spectrometry for the Measurement of Chromium, Selenium, and Molybdenum in Infant Formula and Adult Nutritional Products: First Action 2011.19

2012 ◽  
Vol 95 (3) ◽  
pp. 588-598 ◽  
Author(s):  
Lawrence H Pacquette ◽  
Andre Szabo ◽  
Joseph J Thompson ◽  
Steve Baugh
Keyword(s):  
Infant Formula ◽  
Inductively Coupled Plasma ◽  
Internal Standard ◽  
Reference Method ◽  
Standard Reference Materials ◽  
Internal Standards ◽  
Inductively Coupled ◽  
Technology Standard ◽  
Plasma Mass Spectrometry

Abstract An inductively coupled plasma/MS method was developed for the simultaneous determination of Cr, Se, and Mo in infant formula and other nutritional products. All samples were digested using a closed vessel microwave oven system, together with Ni and Te internal standards. The practical quantitation limits for Cr, Se, and Mo were 0.4, 0.2, and 0.4 ng/mL, respectively; dilution factors were 250 for powders and 50 for liquids. The Cr, Se, and Mo concentrations in 10 nutritional products were within specification limits; within-day and day-to-day (6 independent days) precision values were <5% RSD. For two control samples, the observed precision was ≤2% RSD over 10 independent days. Cr, Se, and Mo results were within the certified limits in three National Institute of Standards and Technology standard reference materials. The average sample spike recoveries for 10 nutritional products ranged from 93 to 107%. Robustness studies showed a minimal effect from concomitant easily ionized element concentrations. However, the choice of internal standard and matrix-matching carbon content were critical to obtaining accurate Se results. All indications are that this method would be a suitable candidate as a global reference method for the determination of these trace elements in infant formula, adult nutritionals, and other nutritional products.

A Sensitive Gas Chromatography-Mass Spectrometry Method for the Determination of Patulin in Apple Juice

2012 ◽  
Vol 95 (6) ◽  
pp. 1709-1712 ◽  
Author(s):  
Hong Xiao ◽  
Shanlin Fu
Keyword(s):  
Drug Testing ◽  
Apple Juice ◽  
Internal Standard ◽  
Extraction Process ◽  
Gas Chromatography Mass Spectrometry ◽  
Internal Standards ◽  
Nitrobenzyl Alcohol ◽  
Specimen Volume ◽  
Common Laboratory

Abstract A simple and sensitive GC/MS method was developed for the detection of patulin in apple juice. The method utilized a common laboratory chemical, 3-nitrobenzyl alcohol, as an internal standard. The calibration curve, ranging from 5 to 100 μg/L, showed good linearity with a correlation coefficient of 0.999. The LOD and LOQ were 2 and 5 μg/L, respectively. The significant advantage of the method was removal of the need for in-house synthesis of appropriate internal standards as reported by other researchers. The method also eliminated the need for careful sample preparation procedures, as outlined in some AOAC methods in which no internal standard was utilized. The streamlined extraction process and the improved sensitivity warrant the developed method to be a useful alternative for drug testing laboratories, especially those with large specimen volume and throughput to determine patulin levels in apple juice.

scholarly journals Simultaneous Determination of Chromium, Selenium, and Molybdenum in Nutritional Products by Inductively Coupled Plasma/Mass Spectrometry: Single-Laboratory Validation

2011 ◽  
Vol 94 (4) ◽  
pp. 1240-1252 ◽  
Author(s):  
Lawrence H Pacquette ◽  
Andre Szabo ◽  
Joseph T Thompson
Keyword(s):  
Simultaneous Determination ◽  
Inductively Coupled Plasma ◽  
Internal Standard ◽  
Reference Method ◽  
Standard Reference Materials ◽  
Internal Standards ◽  
Inductively Coupled ◽  
Technology Standard ◽  
Plasma Mass Spectrometry

Abstract An inductively coupled plasma/MS method was developed for the simultaneous determination of Cr, Se, and Mo in infant formulas and other nutritional products. All samples were digested using a closed vessel microwave oven system, together with Ni and Te internal standards. The practical quantitation limits for Cr, Se, and Mo were 0.4, 0.2, and 0.4 ng/mL, respectively; dilution factors were 250 for powders and 50 for liquids. The Cr, Se, and Mo concentrations in 10 nutritional products were within specifcation limits, and within-day and day-to-day (6 independent days) precision values were <5% RSD. For two control samples, the observed precision was ≤2% RSD over 10 independent days. In three National Institute of Standards and Technology standard reference materials, Cr, Se, and Mo results were within the certifed limits. The average sample spike recoveries for 10 nutritional products ranged from 93 to 107%. Robustness studies showed a minimal effect from concomitant easily ionized element concentrations. However, the choice of internal standard and matrix matching carbon content were critical to obtaining accurate Se results. All indications are that this method would be a suitable candidate as a global reference method for the determination of these trace elements in nutritional products.

Interlaboratory Study on Determination of 2,3,7,8-Tetrachlorodibenzo-p-dioxin in Fish

1983 ◽  
Vol 66 (3) ◽  
pp. 700-707
Author(s):  
John J Ryan ◽  
Jean C Pilon ◽  
Henry B S Conacher ◽  
David Firestone
Keyword(s):  
Mass Spectrometry ◽  
Sample Preparation ◽  
Internal Standard ◽  
Extraction Techniques ◽  
Fish Fillet ◽  
Internal Standards ◽  
Freeze Dried ◽  
Fish Samples ◽  
Resolution Mass

Abstract An interlaboratory round robin study was carried out to estimate the reliability of data on 2,3,7,8-tetra-chlorodibenzo-p-dioxin (TCDD) in fish. Using different methods, 13 laboratories (4 Canadian, 9 American) agreed to analyze 4 fish samples; 3 were Great Lakes salmonids containing bio-incurred levels of TCDD below 100 ppt and the fourth was an ocean fish fillet containing no measurable TCDD. Samples were sent as freeze-dried portions as it was shown that no change of TCDD occurred by this sample preparation. Results were normalized between laboratories by supplying each with an aliquot of the same 2,3,7,8-TCDD standard. Eight laboratories reported a set of results of which one set was rejected. Values from the 7 remaining laboratories for the 3 positive fish showed mean concentrations in pg/g (ppt) and (CV, %) of 61.2 (13.9), 30.4 (18.4), and 32.3 (25.4). Detection limits averaged 3.6 ppt and ranged between 1 and 10 ppt. No significant differences appeared in the concentration of 2,3,7,8-TCDD in fish samples from methods differing in the use of: (i) digestion or extraction techniques, (ii) high or low resolution mass spectrometry, and (iii) isomer specific or nonspecific separations. Overall recovery values using internal standards varied greatly (29-109%) even within the same laboratory and pointed to the need to use an internal standard to obtain precise results. Agreement among laboratories was good considering the level quantitated (ppt) and the diverse methodology.

Infrared Determination of Quartz in Clay Minerals

1983 ◽  
Vol 37 (4) ◽  
pp. 342-347 ◽  
Author(s):  
J. A. Graham ◽  
J. M. Walker
Keyword(s):  
Infrared Spectroscopy ◽  
Calcium Carbonate ◽  
Quantitative Determination ◽  
Clay Minerals ◽  
Internal Standard ◽  
Manganese Carbonate ◽  
Internal Standards ◽  
Calibration Curves ◽  
Cast Film

A method for the quick and reliable quantitative determination of quartz in clay by infrared spectroscopy by using the cast film technique is presented. The technique is demonstrated for two different internal standards, calcium carbonate and manganese carbonate, and is compared with a mull oil technique. The calibration curves were prepared with synthetic mixtures of standard kaolinite and quartz. Analysis of powdered samples demonstrated an absolute precision of less than 1.0% with an accuracy of less than 1.0% when using the manganese carbonate as the internal standard.

scholarly journals Determination of acidity constants at 37 °C through the internal standard capillary electrophoresis (IS-CE) method: internal standards and application to polyprotic drugs

The Analyst ◽  
2020 ◽  
Vol 145 (17) ◽  
pp. 5897-5904 ◽  
Author(s):  
Leo Lebanov ◽  
Elisabet Fuguet ◽  
Javier M. Melo ◽  
Martí Rosés
Keyword(s):  
Capillary Electrophoresis ◽  
Internal Standard ◽  
Acidity Constants ◽  
Internal Standards ◽  
Capillary Electrophoresis Method ◽  
Electrophoresis Method

This work provides the pKa at the biorelevant temperature of 37 °C for a set of compounds proposed as internal standards for the internal standard capillary electrophoresis method. The method is applied to pKa determination of polyprotic drugs.

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