Chuẩn bị mẫu, tài liệu, và lô hàng Sau khi các thủ tục thu thập mẫu là hoàn tất, hộp đựng mẫu phải được bảo quản (nếu cần), giới hạn, tạm giữ, niêm phong, và vận chuyển cùng với các tài liệu phù hợp với các trang web trên hoặc phòng thí nghiệm phân tích cố định để phân tích. Chăm sóc tuyệt vời nên được thực hiện khi chuẩn bị mẫu cho lô hàng từ một lỗi trong quy trình này có tiềm năng vô hiệu các mẫu và các dữ liệu tiếp theo. Chuẩn bị mẫu Ngay sau. | CHAPTER 5 Sample Preparation Documentation and Shipment After the sample collection procedure is complete sample containers must be preserved if required capped custody-sealed and transported along with appropriate documentation to the on-site or fixed analytical laboratory for analysis. Great care should be taken when preparing samples for shipment since an error in this procedure has the potential of invalidating the samples and subsequent data. SAMPLE PREPARATION Immediately after a sample bottle has been filled it must be preserved as specified in the Sampling and Analysis Plan. Sample preservation requirements vary based on the sample matrix and the analyses being performed. Radiological analyses run on soil sediment or solid waste samples rarely require any sample preservation since the radiological composition and activity levels are not influenced by temperature or other factors as the chemical composition is. Water or liquid waste samples for radiological analysis are often preserved with nitric acid HNO3 to prevent isotopes from adhering to the walls of the sample container. Enough nitric acid is added to lower the pH to 2. For chemical analysis the only preservation typically required for soil or sediment samples is cooling the sample to 4 C. For water samples some analyses only require cooling to 4 C whereas others also require a chemical preservative such as HNO3 sulfuric acid H2SO4 hydrochloric acid HCl or sodium hydroxide NaOH . Enough acid or base is added to the sample bottle either to lower the pH to 2 or to raise the pH to 10. The laboratory running the analyses will specify which preservative is required for a particular chemicals used to preserve a sample must be of analytical grade to avoid the potential for contaminating the sample. Cooling samples to 4 C is particularly important for samples to be analyzed for volatile organic compounds since cooling the sample slows the rate of chemical degradation. 271 2001 by CRC Press .