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Laboratory Orientation and Testing of Body Fluids and Tissues for Forensic Analysts

Examples of Written Formulations

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Examples of written formulations
National Institute of Justice (NIJ) (see reuse policy).

Written formulations may be presented in different ways. For example, the instructions for preparation of the four reagents below use different styles to present the correct required information.

5% Chelex (w/v)
(Bio-Rad 143-2832 or equivalent):
Add 5 grams of Chelex 100 Resin to 100 ml of sterile deionized water. Properly label and date the container. Store at room temperature. Expires 1 year after preparation.

Proteinase K, 10 mg/ml (Sigma P-2308 or equivalent):
Dissolve 250 mg proteinase K in 25 ml deionized water. Aliquot and freeze. Properly label, date, and initial the container. If possible, individual aliquots may be labeled. Expires in approximately 3 years per manufacturer's recommendation.

20% (w/v) SDS:
1L bottle
800mL DI H2O
200g SDS (must be ultra pure – electrophoresis grade)
warm if necessary to dissolve
200ml DI H2O
store at RT (no expiration)

Citrate Buffer:
(0.1M Sodium citrate, pH 5.0)
1L bottle
800mL DI H2O
18.4g trisodium citrate dihydrate (Na3C6H5O5 · 2H2O)
adjust pH to 5.0 (takes about 6g citric acid monohydrate, C6H8O7 · H2O)
store at RT (no expiration)

Sample Excerpt from Log Book

The following generic format represents one method of documentation for recording information on specific reagents. For those reagents requiring quality control, this form may be modified to record the date of QC of the reagent and by whom.


Batch #

Initials / Date

Chemical / Lot#; Reagent / Batch#










Sample Label for Reagent Containers

 Alternatively, laboratory tape may be used to mark containers/aliquots with the appropriate information.

The QAS requires reagents to be labeled with the identity of the reagent, the date of preparation or expiration, and the identity of the individual preparing the reagent. Quality assurance and quality control will both be discussed at length in a subsequent module.

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