scholarly journals Design and Preparation of Samples for the International Collaborative Study

Radiocarbon ◽  
1989 ◽  
Vol 31 (03) ◽  
pp. 407-413 ◽  
Author(s):  
D D Harkness ◽  
G T Cook ◽  
B F Miller ◽  
E M Scott ◽  
M S Baxter
Keyword(s):  
Calcium Carbonate ◽  
Environmental Samples ◽  
Collaborative Study ◽  
International Collaborative ◽  
Stage 1 ◽  
International Collaborative Study

Sample materials issued to participants in the interlaboratory calibration exercise are defined and in context of their intended interpretational significance. Preparation of the benzene and calcium carbonate standards as issued for stage 1 is described in detail; likewise, the source and pretreatment/extraction of the environmental samples dispatched for stages 2 and 3.

scholarly journals International Collaborative Study: Structuring and Sample Preparation

Radiocarbon ◽  
1990 ◽  
Vol 32 (3) ◽  
pp. 267-270 ◽  
Author(s):  
G T Cook ◽  
D D Harkness ◽  
B F Miller ◽  
E M Scott ◽  
M S Baxter ◽  
...  
Keyword(s):  
Statistical Analysis ◽  
Sample Preparation ◽  
Collaborative Study ◽  
Intercomparison Exercise ◽  
Hierarchical Nature ◽  
Precision And Accuracy ◽  
International Collaborative ◽  
Stage 1 ◽  
Selection Of ◽  
International Collaborative Study

The success of any intercomparison exercise depends largely on participation and cooperation of a sufficient number of laboratories and the selection of a suitable suite of samples. Unless the latter is satisfactorily devised, the former cannot be guaranteed. The hierarchical nature of this study has necessarily resulted in a far more comprehensive set of sample types than has previously been employed. The exercise was structured to satisfy the following criteria: 1) to enable the participating laboratories to assess the experimental precision and accuracy of the component stages of the dating process; 2) samples should be typical of those routinely dated by the laboratories. This takes on a particular significance in Stage 1 where they should resemble as closely as possible the counting medium; 3) an objective statistical analysis of the results at each component stage of the study.

scholarly journals Systematic Biases in Results of the International Collaborative Study and Their Probable Sources

Radiocarbon ◽  
1990 ◽  
Vol 32 (3) ◽  
pp. 289-294 ◽  
Author(s):  
Mieczysław F Pazdur ◽  
Romuald Awsiuk ◽  
Tomasz Goslar ◽  
Anna Pazdur
Keyword(s):  
Linear Correlation ◽  
Collaborative Study ◽  
Correlation Coefficients ◽  
Large Scatter ◽  
Medium Term ◽  
Systematic Biases ◽  
International Collaborative ◽  
Stage 1 ◽  
Very High ◽  
International Collaborative Study

Results of the International Collaborative Study show an unexpectedly large scatter of individual dates as well as systematic biases. Very high values of linear correlation coefficients are observed for all results of Stage 2 and for benzene samples of Stage 1. We observed moderate correlations for carbonate samples and the lowest for natural samples of wood and peat of Stage 3. The correlation is practically negligible among results obtained in different stages. The probable reasons for such effects are seen in medium-term changes in the calibration of the counting systems.

An International Collaborative Study to Investigate Standardisation of Hirudin Potency

1993 ◽  
Vol 69 (05) ◽  
pp. 430-435 ◽  
Author(s):  
Colin Longstaff ◽  
Man-Yu Wong ◽  
Patrick J Gaffney
Keyword(s):  
Specific Activity ◽  
Collaborative Study ◽  
Residual Activity ◽  
Quality Standard ◽  
Upper Limit ◽  
Assay Procedure ◽  
Specific Activities ◽  
International Collaborative ◽  
Range Of Values ◽  
International Collaborative Study

SummaryAn international collaborative study has been carried out to investigate the reproducibility of hirudin assays in 13 laboratories using four recombinant hirudins and one natural, sulphated product. A simple assay procedure was proposed involving the titration of α-thrombin with inhibitor and measurement of residual activity using a chromogenic substrate. A standard α-thrombin preparation was supplied to ensure that this reagent was of uniform quality throughout the study. The method appeared to present no difficulties and laboratories reported similar potencies for the 5 hirudin samples, in line with expected values. This gave 200–222 Thrombin Inhibitory Units/ampoule (TIU/ampoule) of lyophilised hirudin, with geometric coefficient of variation (gcv) values ranging from 10.15–15.97%. This corresponds to specific activities of approximately 14,300–15,900 TIU/mg protein. This is close to the upper limit of previously reported values of specific activity. We conclude that the precision of this determination compared with the wider range of values in the literature (8,000–16,000 thrombin inhibitory units [TIU]/mg) results from the use of good quality standard α-thrombin by all laboratories. This study has important implications for hirudin standardisation.

A Collaborative Study Designed to Establish the 4th International Standard for Heparin

1984 ◽  
Vol 52 (02) ◽  
pp. 148-153 ◽  
Author(s):  
D P Thomas ◽  
A D Curtis ◽  
T W Barrowcliffe
Keyword(s):  
Collaborative Study ◽  
International Standard ◽  
Thrombin Inhibition ◽  
Freeze Dried ◽  
Assay Methods ◽  
The Mean ◽  
International Collaborative ◽  
International Collaborative Study

SummaryAn international collaborative study, in which 22 laboratories participated, was carried out to establish a replacement for the International Standard for Heparin. A total of 248 assays were analyzed, including APTT, thrombin inhibition and anti-Xa assays, as well as pharmacopoeial assays. Overall, there was less than 5% difference in the mean potency estimates of the candidate preparations, by all assay methods. The freeze-dried preparation 82/502 demonstrated the closest parallelism by bioassay to the existing standard and was established by WHO as the 4th International Standard for Heparin, with an assigned unitage of 1780 i.u. per ampoule.

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