Procedures for Preparing Reagents and Media used in Firearm and Tool Mark Examinations

Transcription

1 Procedures for Preparing Reagents and Media used in Firearm and Tool Mark Examinations North Carolina State Bureau of Investigation Firearm and Tool Mark Section July 10, 1996 Revised February 23, 1998 Revised April 2, 1998 Effective October 28, 2002

2 : PURPOSE This manual will set forth the procedures and steps taken to create the reagents and media used by the Firearm and Tool Mark Section in examinations. Page 2 of 13

3 TABLE of CONTENTS SECTION 1 SECTION 2 SECTION 3 Chemicals & Supplies Needed Safety Procedures Griess Test for Gunpowder Residue % Acetic Acid Solution 3-1 Nitrite Swabs 3-1 Griess Paper 3-2 Sodium Rhodizonate Test for Lead Residue 3-3 Sodium Rhodizonate Solution ph Buffer Solution 3-3 5% Hydrochloric Acid Solution 3-3 Lead Swabs 3-4 Serial Number Restoration Solutions 3-5 & 3-6 SECTION 4 Disposal How to Read a Material Safety Data Sheet APPENDIX I Page 3 of 13

4 CHEMICALS & SUPPLIES NEEDED SECTION 1 The following chemicals and supplies will be needed to produce the reagents and media used by the Firearm and Tool Mark Section: Chemicals Glacial Acetic Acid, 99.8%, biochemical grade Sodium Nitrite Sulfanilic Acid Iron (III) Chloride (also called Ferric Chloride) 1-Naphthol Methanol Sodium Rhodizonate (also called Rhodizonic acid, disodium salt) Sodium Bitartrate Sodium Hydroxide Tartaric Acid Hydrochloric Acid, reagent ACS Cupric Chloride Deionized Water Supplies 6" Cotton Tipped Swabs Desensitized Photographic Paper Lead Sheets (will be utilized but not consumed) Page 4 of 13

5 SAFETY SECTION 2 Everyone involved in laboratory operations must be safety minded. Avoid working in the laboratory alone. Do not eat, drink, use tobacco products or apply cosmetics in areas other than those specified for that purpose. Keep work areas clean and ensure access to exits. Prior to handling chemicals identify the physical properties and hazards of the chemicals. Always add acid to water instead of water to acid. Use a funnel when pouring chemicals. Keep flammable materials away from open flames and sparks. Use a fume hood when working with flammable materials. Always ensure your personal safety by wearing the appropriate personal protection equipment. Eye protection must be worn at all times by anyone working or visiting an area of the laboratory where hazards exist. Wear protective hand coverings when handling corrosive agents. Wear protective clothing. Material Safety Data Sheets (MSDS) are located in the section Conference Room (right corner, front wall of room) in a binder. Appendix 1 is a copy of OSHA publication 2265, Material Safety Data Sheet. This document describes how to read an MSDS. A copy of this document is also at the front of the Section MSDS binder. Spill Control Materials There is a container of sodium bicarbonate for neutralization of acid spills and several boxes of flammable absorbing material located in Drug Chemistry Section. These materials should be used in the event of any manageable spill of liquid acid solutions and liquid flammable solutions. Also available are heavy duty gloves, forearm guards, and aprons for use in dealing with strong corrosives spills. Page 5 of 13

6 PROCEDURES SECTION 3-1 Griess Test for Gunpowder Residue This test is used to determine the presence of gunpowder residues and the patterns of gunpowder residue that are exhibited by a particular weapon. Preparation of 15% Acetic Acid Solution Combine 150 ml of glacial acetic acid with 850 ml of deionized water in a 1000 ml graduated cylinder. This solution may be doubled or halved to produce the desired quantity. Store at room temperature. Solution expires six (6) months after preparation. Record preparation on Chemical Mixture Log. Each examiner is responsible for transferring current information (preparation and expiration dates) from bulk solution containers to their individually assigned storage container if so used. Preparation of Nitrite Swabs 1. Dissolve grains of sodium nitrite in 25 ml of deionized water in a 50 ml beaker. 2. Soak the cotton tipped ends of swabs in the solution. 3. Dry the swabs by placing them upside-down (cotton tip up) in a beaker. 4. Test swabs by saturating the tip of an untreated swab (control) with 15% acetic acid solution and streaking a piece of Griess paper. Then saturate a freshly prepared nitrite swab with 15% acetic acid solution and streak the same piece of Griess paper in a different location. A positive test result occurs when an orange streak is produced by the nitrite swab. The streak made by the control swab should be clear. This recipe can be doubled or halved to produce the desired quantity. Store nitrite swabs at room temperature. Nitrite swabs have no expiration date. Record preparation on Chemical Mixture Log. Page 6 of 13

7 PROCEDURES SECTION 3-2 Preparation of Griess Paper 1. Dissolve 7.7 grains of sulfanilic acid in 100 ml of deionized water in a 500 ml beaker. 2. Dissolve 4.3 grains of 1-Naphthol in 100 ml of methanol in a 500 ml beaker. 3. Combine the equal amounts of sulfanilic acid and 1-naphthol solutions. 4. Place solution in a non-reactive photo processing tray. 5. Briefly dip precut sheets of desensitized photographic paper into tray. Simply submerge each sheet. 6. Hang sheets to dry and place the remaining Griess paper solution into an uncontaminated and sealed storage container (to make paper in the future begin at step 4). 7. Once the Griess paper has dried, test a piece for sensitivity to nitrite compounds by saturating the tip of an untreated swab (control) with 15% acetic acid solution and streaking the paper. Then saturate the tip of a nitrite swab with 15% acetic acid solution and streak the same piece of Griess paper in a different location. A positive test result occurs when an orange color appears on the paper where the nitrite swab was streaked. The streak made by the control should not turn orange. Store paper and unused solution at room temperature. Solution expires one (1) year after preparation. Paper does not expire. Record chemical preparation on Chemical Mixture Log. Prepare Griess paper as needed, no permanent record of paper preparation is required. Page 7 of 13

8 PROCEDURES SECTION 3-3 Sodium Rhodizonate Test for Lead Residue This test is used to determine the presence of lead. Preparation of Sodium Rhodizonate Solution Combine a small amount of sodium rhodizonate with 10 to 20 ml of deionized water in a 50 or 100 ml beaker until the solution is saturated. Saturation occurs when a slight sediment is noted on the bottom of the beaker after stirring with a clean glass rod. (The saturated solution will appear the color of strong tea.) Do not store. Make only enough solution for immediate use. Preparation of 2.8 ph Buffer Solution Dissolve 29.3 grains of sodium bitartrate and 23.1 grains of tartaric acid per 100 ml of deionized water in a 500 ml beaker. This usually requires both heat and agitation to complete within a reasonable period of time. This recipe may be doubled or halved to produce the desired quantity. Store at room temperature in an uncontaminated and sealed container. Solution expires one (1) month after preparation. Record preparation on Chemical Mixture Log. Preparation of 5% Hydrochloric Acid Solution Combine 5 ml of hydrochloric acid, reagent ACS, with 95 ml of deionized water in a 500 ml beaker. This solution may be double or halved to produce the desired quantity. Store at room temperature. Solution expires six (6) months after preparation. Record preparation on Chemical Mixture Log. Each examiner is responsible for transferring current information (preparation and expiration dates) from bulk solution containers to their individually assigned storage container. Page 8 of 13

9 PROCEDURES SECTION 3-4 Preparation of Lead Swabs 1. Wipe cotton tip of swabs on the surface of the lead sheets thereby transferring lead to the cotton swabs. 2. Test the lead swabs by following the Sodium Rhodizonate Test for Lead Residue. An untreated swab (control) should be tested as well. A positive test result occurs when the lead swab turns a blue-violet color following the spraying of 5% hydrochloric acid (last solution applied) indicating the presence of lead. The control should not turn blue-violet. Store lead swabs at room temperature. Lead swabs have no expiration date. Record preparation on Chemical Mixture Log. Page 9 of 13

10 PROCEDURES SECTION 3-5 Preparation of Serial Number Restoration Solutions Acidic Ferric Chloride Solution Combine 25 grams of FeCl 3 (Ferric Chloride) with 100 ml of deionized water. Then add 25 ml of HCl (Certified A.C.S. Plus) and stir until the FeCl 3 is no longer visible in the solution. Solution expires one (1) year after preparation. Davis Reagent Combine 5 grams of CuCl 2 H 2 O (Cupric Chloride) with 50 ml of deionized water. Then add 50 ml of HCl (Certified A.C.S. Plus) and stir until the CuCl 2 H 2 O is no longer visible in the solution. Solution expires one (1) year after preparation. Ferric Chloride Combine 25 grams of FeCl 3 (Ferric Chloride) with 100 ml of deionized water and stir until the FeCl 3 is no longer visible in the solution. Solution expires one (1) year after preparation. Fry s Reagent Dissolve cupric chloride into 200 ml of hydrochloric acid, reagent ACS, until saturated in a 500 ml beaker. Saturation occurs when a slight sediment is noted on the bottom of the beaker after stirring with a clean glass rod. Store in a sealed Nalgene bottle at room temperature. Solution expires one (1) year after preparation. 25% Nitric Acid Solution Add 75 ml of HNO 3 (Nitric Acid) to 225 ml of deionized water and mix. Solution expires one (1) year after preparation. Page 10 of 13

11 PROCEDURES SECTION % Sodium Hydroxide Solution Dissolve 10 g NaOH (Sodium Hydroxide) into 90 ml of deionized water until the pellets are no longer visible. Solution expires one (1) year after preparation. Turner s Reagent Combine 2.5 grams of CuCl 2 H 2 O (Cupric Chloride) with 30 ml of deionized water. Then add 40 ml of HCl (Certified A.C.S. Plus) and 25 ml of Ethanol. Stir until CuCl 2 H 2 O is no longer visible in the solution. Solution expires one (1) year after preparation. Page 11 of 13

12 DISPOSAL SECTION 4 Disposal of Reagents and Media used in the Firearm and Tool Mark Section All reagents used in the Firearm and Tool Mark Section may be diluted with a sufficient quantity of water and poured down the drain. Griess paper, Nitrite swabs, and Lead swabs may be disposed of in the trash. Page 12 of 13

13 APPENDIX I How to read a Material Safety Data Sheet. (This information is not available in electronic format). Page 13 of 13