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LGC6181 Sewage Certified values for 12 metals collected
sludge - leachable from a city water treatment plant
metals immediately after discharge from a digestion tank
LGC144R Sewage sludge (domestic Certified values for 9 total and 9 aqua
origin) - trace metals regia-soluble metals
LGC145R Sewage sludge (mixed Certified values for 8 total and 5 aqua
origin) - trace metals regia-soluble metals
LGC146R Sewage sludge Certified values for 9 total and 9 aqua
(industrial origin) - trace metals regia-soluble metals
CRM088 Sewage sludge - PAHs Certified values for 8 PAHs
RTC018 Raw sewage sludge - metals Certified values for 23 metals
RTC029 Sewage sludge - metals Certified values for 22 metals
SRM2781 Domestic sludge - metals Certified values for 10 metals
SRM2782 Industrial Certified values for 10 metals collected
sludge - leachable and from an industrial site in northern
total metals New Jersey, USA
aPCB, polychlorinated biphenyl; PAH, polycyclic (polynuclear) aromatic hydrocarbon; PCDD, polychlorinated dibenzo-^-dioxin; PCDF, polychlorinated dibenzofuran; EDTA, ethylenediaminetetraacetic acid; DTPA, diethylen-etriaminepentaacetic acid; BTEX, benzene-toluene-ethylbenzene-xylene(s); TPH, total petroleum hydrocarbon; semi-VOAs, semi-volatile organic analytes.
Comment on the types, i.e. metals vs. organics, of certified reference materials presented in Table 2.1.
The range of CRMs available for environmental analyses is an expanding area of development for certifying bodies. You should note from Table 2.1 that while metals in environmental matrices are dominant there is an increasing number of CRMs for organic compounds, e.g. polynuclear aromatic hydrocarbons (PAHs). This trend is likely to continue for some time.
Analysis of reagent blanks. Analyse reagents whenever the batch is changed or a new reagent is introduced. Introduce a minimum number of reagent
Methods for Environmental Trace Analysis
blanks (typically 5% of the sample load); this allows reagent purity to be assessed and, if necessary, controlled and also acts to assess the overall procedural blank.
• Calibration with standards. A minimum number of standards should be used to generate the analytical curve, e.g. six or seven. Daily verification of the working curve should also be carried out by using one or more standards within the linear working range.
Examine the graphs shown in Figure 2.4 and determine their linear working ranges.
• Analysis of duplicates. This allows the precision of the method to be reported.
• Maintenance of control charts. Various types of control charts can be maintained for standards, reagent blanks and replicate analytes. The purpose of each type of chart is to assess the longer-term performance of the laboratory, instrument, operator or procedure, based on a statistical approach.
Concentration (mg l 1) (a)
Concentration (mg l 1) (c)
Concentration (mg l 1) (b)
20 40 60 80
Concentration (mg l-1) (d)
Figure 2.4 Plots for linear dynamic range determinations (cf. SAQ 2.2).
Investigative Approach for Sample Preparation
This chapter has considered the various aspects of planning the experimental work, introducing the concepts of quality assurance, accuracy and precision, and certified reference materials. It is now time to consider the initial phase of any environmental analysis procedure, i.e. sampling, and this will be discussed in the next chapter.
1. Anon, Certified Reference Materials Catalogue, Issue No. 3, Laboratory of the Government Chemist, Teddington, UK, 2000.
Methods for Environmental Trace Analysis. John R. Dean Copyright © 2003 John Wiley & Sons, Ltd. ISBNs: 0-470-84421-3 (HB); 0-470-84422-1 (PB)
• To understand the concept of representative sampling.
• To understand the principles of sampling soil and sediment, water and air.
• To be able to determine the number of samples to be taken and be aware of the limitations.
In an ideal world, all environmental samples would be analysed instantaneously without any need to transport samples to a laboratory. However, things are never quite like that. In order to economize on time, effort and cost, the areas under investigation must be sampled. Therefore, sampling of a particular site, lake or the atmosphere is required. Sampling constitutes the most important aspect of environmental analysis as without effective sampling all of the subsequent data generated are worthless. There are two primary types of sampling for environmental analysis, i.e. random sampling and purposeful sampling. The most important is random sampling as it infers no selectiveness to the sampling process.
Before reading on, how would you sample an agricultural field for soil samples, a flowing river for water samples, or the indoor air in an industrial manufacturing site?
Probably you have been able to suggest some approaches. Now read on to see if your ideas are appropriate.