Sample holding time

Capel, P.D., Larson, S.J. (1995) A chemodynamic approach for estimating losses of target organic chemicals form water during sample holding time. Chemosphere 30, 1097-1107. 

In addition to determining the presence or absence of pollutants of interest in the sample, the routine analysis must include quality control/quality assurance tests to determine the precision and accuracy of the test results and any possible source of errors such as sample contamination, absence of preservative, or exceeding of sample holding time. The QA/QC is discussed at length in Chapter 1.2. 

After the samples have been packaged, they are shipped to the laboratory (Step 7). Samples must reach the laboratory in the shortest period of time possible, as any delays in transit jeopardize temperature conditions inside the shipping container and erode sample holding time. Incorrect information on shipping labels and lack of coordination with the delivery service are known to cause delays of sample delivery to the laboratory. 

Logistics of daily sample shipment from the project site to the laboratory that may affect the sample holding time... 

Sample Custodians open the coolers, remove the COC Forms and verify the COC Form against the cooler contents. At many laboratories, Sample Custodians will not sign and date the COC Form and log-in a sample into the LIMS until all identified discrepancies have been resolved with the client. The resolution of outstanding issues may delay the start of analysis and erode the sample holding time. The following mistakes made by field sampling personnel are detected at this first step of the laboratory process ... 

Common steps in sample preservation are the use of proper containers, temperature control, addition of preservatives, and the observance of recommended sample holding time. The holding time depends on the analyte of interest and the sample matrix. For example, most dissolved metals are... 

The measurements were conducted on a rotary viscometer Viscoster UTS 50 of HAAKE. Applications software was used for treatment of the results. A Cone Board instrument was used. Radius = 25 mm Aperture angle = 3.49 x 10" rad kegel PK5 2.0 GRAD cone running clearance = 100 pm sample volume = 1.2 cm. The measurements were conducted at shear rate 30 - 2.2 X 10 s and within a temperature range from -20 to 50 °C. Sample holding time at preset temperature before measurements was 20 min. 

---