Books
in black and white
Main menu
Home About us Share a book
Books
Biology Business Chemistry Computers Culture Economics Fiction Games Guide History Management Mathematical Medicine Mental Fitnes Physics Psychology Scince Sport Technics
Ads

Chromatografy Methods for Environmental - Ando D.J.

Ando D.J. Chromatografy Methods for Environmental - Wiley publishing , 2003. - 265 p.
Download (direct link): chromatography2003.pdf
Previous << 1 .. 12 13 14 15 16 17 < 18 > 19 20 21 22 23 24 .. 83 >> Next

It is also important to prepare the sample container prior to sample storage. In the case of samples for metal analysis, the following procedure is recommended. The sample container, borosilicate glass or plastic (polyethylene, polypropylene or ‘Teflon’ (PTFE)) should be treated in the following sequence:
1. Wash in detergent to remove any solid residues (may not be necessary).
2. Soak containers for at least 24 h in an acid bath (10% nitric acid; 10 ml of concentrated nitric acid in every 100 ml volume of water).
3. Rinse with deionized distilled water.
4. Repeat the rinse step at least twice more with deionized distilled water.
In some cases, the removal of organic residues from glassware requires the use of a chromic acid wash (prepared by adding 100 ml of concentrated sulfuric acid slowly and with constant stirring to a solution of 5 g of sodium dichromate in 5 ml of water). In this situation, it is important to thoroughly rinse the glassware in deionized water so as to remove any trace of chromium, particularly if the latter species is part of the analytical scheme.
Table 4.1 Selected examples of preservation techniques for water samples“
Compound Container Preservation Maximum holding time
Metals
Total Polyethylene, with a polypropylene cap (no liner), or glass 100 ml of water acidified (HNO3) to pH < 2 6 months
Dissolved Polyethylene, with a polypropylene cap (no liner), or glass 200 ml of water filtered on site, then acidify (HNO3) to pH < 2 6 months
Suspended Polyethylene, with a polypropylene cap (no liner), or glass 200 ml of water filtered on site 6 months
Chromium Polyethylene, with a polypropylene cap (no liner), or glass Cool to 4°C (200 ml of water) 24 h
Non-metals
Fluoride Plastic or glass None required (300 ml of water) 28 days
Chloride Plastic or glass None required (200 ml of water) 28 days
Bromide Plastic or glass None required (100 ml of water) 28 days
Nitrate and nitrite Plastic or glass Cool to 4°C, add H2SO4 to pH < 2 (100 ml of water) 28 days
Sulfate Plastic or glass Cool to 4°C (50 ml of water) 28 days
Organics
Pesticides (organochlorine) Glass 1 ml of a 10 mgmD1 HgCl2 or adding of extraction solvent (500 ml of water) 7 days, 40 days after extraction
Pesticides (organophosphorus) Glass 1 ml of a 10 mgmD1 HgCl2 or adding of extraction solvent (500 ml of water) 14 days, 28 days after extraction
Pesticides (chlorinated herbicides) Glass Cool to 4°C, seal, add HC1 to pH < 2 (500 ml of water) 14 days
Pesticides (polar) Glass 1 ml of a 10 rngrnD1 HgCl2 (500 ml of water) 28 days
Phenolic compounds Glass Cool to 4°C, add H2S04 to pH < 2 (500 ml of water) 28 days
Biological oxygen demand (BOD) Plastic or glass Cool to 4°C (1000 ml of water) 48 h
Chemical oxygen demand (COD) Plastic or glass Cool to 4°C, add H2S04 to pH < 2 (50 ml of water) 28 days
aAs recommended by different agencies, e.g. The Environmental Protection Agency (EPA) and The International Organization for Standardization (ISO).
Methods for Environmental Trace Analysis
Table 4.2 Stability of chemical species in environmental matrices [1]
Matrix Container Preservation Maximum holding time Reference
Organotin species“
Synthetic solutions Polyethylene HC1 acidified water, in the dark, at 4 C 3 months 2
(TPT and TBT)
Synthetic solutions Brown glass HC1 acidified water at 25° C 20 days 3
(TPT and TBT)
Sea water (TBT) Pre-washed ‘Pyrex’ bottles Filtered sample acidified to pH < 2 and stored at 4°C — 4
Sea water (butyltins but Polycarbonate bottles Cooled to 4°C and stored in the dark 7 months 5
not TPT)
Sea water Ci8 cartridges Room temperature 60 days for TPT and 7 months for butyltins 5
Sediment (wet) (TBT) Cooled to 4° C or frozen, followed by different drying procedures, i.e. oven drying at 50° C, freeze-drying and air-drying. NOT suitable for DBT and MBT 4 months 4
Sediment (wet) (OT) Loss of butyltins when using either air-drying under the action of light, an IR lamp or oven drying at 110° C. Butyltin and phenyltin species unaffected by lyophilization or desiccation procedures 3 months for phenyltins and 1 year for butyltins 6
Freshwater sediment (OT) — Store at — 20° C, independent of the treatment used for preservation 18 months 5
Oysters and cockles Lyophilization (drying procedure) allows butyltin species to be stable if stored at — 20° C and in the dark 150 days 5
Mussels Lyophilization (drying procedure) allows butyltin species to be stable if stored at — 20° C and in the dark 44 months 7
Organoarsenicalsb
Distilled and natural (As(iii) and As(v)) ‘Pyrex’ and polyethylene bottles Sulfuric (0.2 vol%) acidified water (pH < 1.5) at room temperature; 40% losses if pH increased 125 days 8
0continued overleaf)
Storage of Samples
4^
4^
Table 4.2 (continued)
Matrix Container Preservation Maximum holding time Reference
Interstitial water (As(iii)) ‘Pyrex’ and polyethylene bottles HC1 acidified water (pH 2) and cool to ~0°C 6 weeks 9
Water (methylated species) — HC1 (4 ml I-1 of sample) acidified water Several months 10
Previous << 1 .. 12 13 14 15 16 17 < 18 > 19 20 21 22 23 24 .. 83 >> Next