Attachment of samples

Figure 2. Vests provide secure attachment of sampling equipment to workers who are engaged in strenuous activities.

Double-sided sticky tapes are popular for the attachment of samples. Various brands and types are available. For many routine measurements conventional tape is sufficient however, some thicker variants may lead to problems when pressure is exerted to fix the samples, since the tape will relax and hence cause substantial drift in the AFM image. A similar effect may be present as a result of thermal expansion, when a cold AFM is operated with high resolution in the first hour(s)... 

This method follows the ASTM D 1159 and D 2710 procedures and the AFNOR M 07-017 standard. It exploits the capacity of the double olefinic bond to attach two bromine atoms by the addition reaction. Expressed as grams of fixed bromine per hundred grams of sample, the bromine number, BrN, enables the calculation of olefinic hydrocarbons to be made if the average molecular weight of a sufficiently narrow cut is known. 

Samples logged into the system are assigned a unique number which is often physically attached to the sample using a bar-code label. The testing protocol is contained in the LIMS and is based on the point in the process from which the sample was taken. This information and the identification of the type of sample enable the LIMS to schedule the testing of the material. 

A more permanent installation is provided by a chain-driven sampler, widely used in paper (qv) and steel (qv) mills, manufactured as the E Sampler by QCEC (20). A cup, which is attached to a chain positioned perpendicular to flow, travels down through the Hquid flow and returns to the upper sprocket, where the sample is drained into a container. Flow-proportional timers can be installed to change the rate of sampling with flow rate (see Flow l asurel nt). 

In outline the procedure consists of carefully weighing about 5-10 mg of sample on to a shaped piece of paper (Fig. 3.11c) which is folded in such a way that the tail (wick) is free. This is then placed in a platinum basket or carrier suspended from the ground-glass stopper of a 500 mL or 1 litre flask. The flask, containing a few millilitres of absorbing solution (e.g. aqueous sodium hydroxide), is filled with oxygen and then sealed with the stopper with the platinum basket attached. 

Carbon-supported Ru-Sn catalyst Ru and Sn Mossbauer measurements were performed to investigate catalysts of ruthenium and tin supported on activated carbon (Ru-Sn/C). The samples were subjected to different reducing and oxidizing treatments. The presence of tin leads to a substantial increase of the Lamb-Mossbauer factor of the metallic Ru-particles showing that tin strengthens the attachment of the particles to the support. The close contact between the two metals appears to be decisive for the formation of catalytically active sites (Ru-Sn and Ru-SnOj,-)... 

When the bacteria to be detected are less than 1% of the total population in a sample, IFAs cannot be used because of interference from unrelated particles that are concentrated when large volumes of sample are filtered. To overcome this problem, the organism of interest may be concentrated by immunomagnetic separation.10,51 62 For this procedure magnetic beads coated with monoclonal or polyclonal antibodies are mixed with the sample. The beads are collected with a magnet, and the cells attached to the beads then are removed, enumerated, and identified by IFAs. 

The temperature resistance of the polysiloxane on the samples was tested by stepwise heating up to 500°C. Whereas the pure hydrolysis product undergoes a complete thermal degradation via oxidative conversion of the CH3-Si groups into HO-Si groups, the polysiloxane persists on the silica sample. This stabilization effect most likely results from the covalent attachment of the methyl-polysiloxane. 

The 13C NMR sensitivity can sometimes be a problem, but for the kind of samples studied here the effective concentration of monomer units is several molar which does not place excessive demands on present Fourier transform NMR spectrometers. In addition to the sensitivity of the chemical shift to structure (9), the relaxation of protonated carbons is dominated by dipole-dipole interaction with the attached proton (9). The dependence of the relaxation parameters T, or spin-lattice, and Tor spin-spin, on isotropic motional correlation time for a C-H unit is shown schematically in Figure 1. The T1 can be determined by standard pulse techniques (9), while the linewidth at half-height is often related to the T2. Another parameter which is related to the correlation time is the nuclear Overhauser enhancement factor, q. The value of this factor for 13C coupled to protons, varies from about 2 at short correlation times to 0.1 at long correlation... 

For the determination of the radon daughter concentrations down to 1 Bq m 3 a counting and sampling time of 60 minutes and a counting time of 20-40 minutes after the end of sampling were used. From the counts of Po-218 and Po-214 of the two samples measured in different intervals the concentrations of the free and attached radon daughters were calculated (Wicke and Porstendorfer, 1983). 

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