- Email: [email protected]
mass spectrometer
J. Anal. Appl. Pyrolysis 71 (2004) 47–50
Analysis of red phosphorus using a pyrolysis gas chromatograph/mass spectrometer J. Schieferecke∗ , D. Worley Kansas Bureau of Investigation Headquarters Laboratory, 1620 SW Tyler Street, Topeka, KS 66612, USA
Abstract A qualitative method has been developed for the analysis of red phosphorus found in clandestine methamphetamine manufacturing laboratories. This method converts the red allotropic form of phosphorus into the white allotropic form of phosphorus using heat (The Merck Index—An Encyclopedia of Chemicals, Drugs, and Biologicals, eleventh ed., 1989, p. 1167) from a pyrolysis unit. The pyrolysis unit is interfaced to a gas chromatograph/mass spectrometer for positive phosphorus identification. © 2003 Elsevier B.V. All rights reserved. Keywords: Phosphorus; Heat; Spectrometer
1. Introduction There are many methods available for the clandestine manufacture of methamphetamine. One popular manufacturing method uses red phosphorus in conjunction with iodine and water to produce hydriodic acid. The hydriodic acid reacts with ephedrine and/or pseudoephedrine to produce methamphetamine. Therefore, the determination of phosphorus in clandestine methamphetamine manufacturing samples becomes important for criminal case construction. In clandestine laboratories, red phosphorus is found commonly as a fine red powder in bottles, cans, on filter paper, on matchbook strike plates and as sediment in solution. Some characteristics of phosphorus include one naturally occurring isotope with a molecular weight of 30.97 g mol−1 . Phosphorus has three allotropic forms—white, black, and red. The white and red allotropic forms are the most common and their discussion follows. White phosphorus is poisonous, while pure red phosphorus is not poisonous. Red phosphorus is insoluble in water and organic solvents, while white phosphorus is slightly to ∗
Corresponding author. Tel.: +1-785-296-8335. E-mail address: [email protected] (J. Schieferecke).
0165-2370/$ – see front matter © 2003 Elsevier B.V. All rights reserved. doi:10.1016/S0165-2370(03)00097-4
48
J. Schieferecke, D. Worley / J. Anal. Appl. Pyrolysis 71 (2004) 47–50
very soluble in several organic solvents, i.e. ether, chloroform, benzene and carbon disulfide. White phosphorus is stored under water, while red phosphorus is not. Red phosphorus ignites at ≈ 260 ◦ C in air, while white phosphorus ignites at ≈ 30 ◦ C in moist air. White phosphorus is made of four atoms of phosphorus forming a symmetrical, tetrahedral P4 molecule, while long chains of the P4 units form red phosphorus. When distilled in an oxygen deficient atmosphere at 290 ◦ C, the bonds between the red phosphorus P4 units break forming P4 vapor that condenses to a liquid that solidifies to white phosphorus. However, when held at ≈ 250 ◦ C, white phosphorus converts slowly back to red phosphorus. This conversion accelerates with the addition of a trace of iodine and once started will continue at a lower temperature [1].
The determination of red phosphorus has been performed using many methods. One of the first qualitative methods developed by the Kansas Bureau of Investigation (KBI) Chemistry Unit was the derivation of red phosphorus to phosphorus tribromide using bromine, carbon disulfide, pipettes and two test tubes. To the first test tube, two drops of bromine was added to ≈ 2 ml of carbon disulfide. To the second test tube, a few milligrams of red phosphorus was added, then covered with ≈ 2 ml of carbon disulfide. The carbon disulfide/bromine solution was slowly added and mixed with the phosphorus/carbon disulfide mixture. The addition was stopped when approximately half of the red phosphorus had been consumed. The sample was mixed until the bromine color cleared. A sample introduced into the gas chromatograph/mass spectrometer provided positive sample identification of the phosphorus tribromide derivative. Because bromine and phosphorus tribromide are hazardous chemicals to personnel and chromatographic columns, there was a need to find a better way to analyze red phosphorus. The KBI Chemistry Unit acquired a GC/MS with a direct insertion probe and developed a method for the analysis of red phosphorus. The probe contained a filament that volatilized red phosphorus samples directly into the mass spectrometer source. The system permitted phosphorus identification; however, maintaining consistent sample size was a problem. This combined with a cumbersome probe procedure limited the use of the unit. In order to augment our inorganic analysis capabilities, the KBI Chemistry Unit acquired an X-ray fluorescence spectrophotometer. It quickly became a favorite for the determination of phosphorus in clandestine methamphetamine laboratory samples. This instrument had the occasional need for an expensive detector replacement. When this happened, the KBI Chemistry Unit would use the phosphorus tribromide derivation method or the direct insertion probe to analyze red phosphorus samples. While evaluating a phosphorus tribromide sample spectra, a small chromatographic peak with a corresponding white phosphorus spectrum was observed (no determination was made of the white phosphorus source. The white phosphorus may have been part of the sample or it may have been a byproduct of the derivation process.) This observation was significant because it led to the search to convert red phosphorus into white phosphorus. Soon, a KBI
J. Schieferecke, D. Worley / J. Anal. Appl. Pyrolysis 71 (2004) 47–50
49
chemist developed a method for quickly heating red phosphorus in a nitrogen-purged and capped test tube. The method used ≈ 3 mg of red phosphorus, 10 × 75 mm flint glass test tubes and 10 mm Fisherbrand Tainer Top Safety closures. Preparing the sample involved placing red phosphorus in a test tube, purging the test tube with dry nitrogen and quickly capping the test tube. The conversion took place in an operating fume hood using heat from a Bunsen burner applied to the bottom of the test tube. When the sample started to form white vapor, the test tube was removed and allowed to cool. The vapor condensed inside the test tube into very small clear droplets. Chloroform (2 ml) quickly added to the test tube dissolved the clear droplets. A sample of the solution subjected to the gas chromatograph/mass spectrometer permitted phosphorus identification. Shortly thereafter, the KBI Chemistry Unit acquired an Agilent GC/MS system (6890A GC and 5973 MS) fitted with a CDS Analytical, Inc. Pyroprobe 2000 pyrolysis instrument. After installation and initial testing were complete, a KBI chemist realized that the high temperature and inert conditions in the Pyroprobe 2000 were comparable to the recently developed purged and capped test tube technique. A sample of red phosphorus was placed into the Pyroprobe 2000 under the same conditions as the initial test samples. The results were encouraging and the following method developed for the analysis of red phosphorus.
2. Experimental A sample of red phosphorus (<0.1 mg) was pyrolyzed with a setpoint of 750 ◦ C for 20 s using a CDS Pyroprobe 2000. Analysis was performed using an Agilent GC/MS
Fig. 1. Chromatographic peak and mass spectrum of white phosphorus produced from red phosphorus.
50
J. Schieferecke, D. Worley / J. Anal. Appl. Pyrolysis 71 (2004) 47–50
(6890A/5973) system with a HP-1MS (30 m × 0.32 mm × 0.25 film thickness) capillary column. The oven ramped from 100 to 275 ◦ C at 25 ◦ C per minute. Helium was the carrier gas, had an inlet pressure of 10.00 psi and split ratio of 50:1. The mass spectrometer scan range was 30–200 AMU. The phosphorus spectra obtained with this technique (Fig. 1) were similar to those obtained using the direct insertion probe and those using the nitrogen purged and capped test tube technique.
3. Discussion Suspected clandestine laboratory red phosphorus samples vary widely in composition. Because of this variation, the temperatures used for the operation of the Pyroprobe 2000 and the gas chromatograph operations are higher to ensure sample pyrolysis and elution. The pyrolysis technique employed to analyze samples thought to contain red phosphorus is an easy technique to learn and use. It gives excellent results with less sample handling than the direct insertion probe technique or the nitrogen purged, capped, and heated test tube technique. In addition, this technique reduces the hazards associated with handling white phosphorus.
Reference [1] W.F. Ehret, Smith’s College Chemistry, sixth ed, Appleton-Century, New York, London, 1946, p. 365.
Analysis of red phosphorus using a pyrolysis gas chromatograph/mass spectrometer J. Schieferecke∗ , D. Worley Kansas Bureau of Investigation Headquarters Laboratory, 1620 SW Tyler Street, Topeka, KS 66612, USA
Abstract A qualitative method has been developed for the analysis of red phosphorus found in clandestine methamphetamine manufacturing laboratories. This method converts the red allotropic form of phosphorus into the white allotropic form of phosphorus using heat (The Merck Index—An Encyclopedia of Chemicals, Drugs, and Biologicals, eleventh ed., 1989, p. 1167) from a pyrolysis unit. The pyrolysis unit is interfaced to a gas chromatograph/mass spectrometer for positive phosphorus identification. © 2003 Elsevier B.V. All rights reserved. Keywords: Phosphorus; Heat; Spectrometer
1. Introduction There are many methods available for the clandestine manufacture of methamphetamine. One popular manufacturing method uses red phosphorus in conjunction with iodine and water to produce hydriodic acid. The hydriodic acid reacts with ephedrine and/or pseudoephedrine to produce methamphetamine. Therefore, the determination of phosphorus in clandestine methamphetamine manufacturing samples becomes important for criminal case construction. In clandestine laboratories, red phosphorus is found commonly as a fine red powder in bottles, cans, on filter paper, on matchbook strike plates and as sediment in solution. Some characteristics of phosphorus include one naturally occurring isotope with a molecular weight of 30.97 g mol−1 . Phosphorus has three allotropic forms—white, black, and red. The white and red allotropic forms are the most common and their discussion follows. White phosphorus is poisonous, while pure red phosphorus is not poisonous. Red phosphorus is insoluble in water and organic solvents, while white phosphorus is slightly to ∗
Corresponding author. Tel.: +1-785-296-8335. E-mail address: [email protected] (J. Schieferecke).
0165-2370/$ – see front matter © 2003 Elsevier B.V. All rights reserved. doi:10.1016/S0165-2370(03)00097-4
48
J. Schieferecke, D. Worley / J. Anal. Appl. Pyrolysis 71 (2004) 47–50
very soluble in several organic solvents, i.e. ether, chloroform, benzene and carbon disulfide. White phosphorus is stored under water, while red phosphorus is not. Red phosphorus ignites at ≈ 260 ◦ C in air, while white phosphorus ignites at ≈ 30 ◦ C in moist air. White phosphorus is made of four atoms of phosphorus forming a symmetrical, tetrahedral P4 molecule, while long chains of the P4 units form red phosphorus. When distilled in an oxygen deficient atmosphere at 290 ◦ C, the bonds between the red phosphorus P4 units break forming P4 vapor that condenses to a liquid that solidifies to white phosphorus. However, when held at ≈ 250 ◦ C, white phosphorus converts slowly back to red phosphorus. This conversion accelerates with the addition of a trace of iodine and once started will continue at a lower temperature [1].
The determination of red phosphorus has been performed using many methods. One of the first qualitative methods developed by the Kansas Bureau of Investigation (KBI) Chemistry Unit was the derivation of red phosphorus to phosphorus tribromide using bromine, carbon disulfide, pipettes and two test tubes. To the first test tube, two drops of bromine was added to ≈ 2 ml of carbon disulfide. To the second test tube, a few milligrams of red phosphorus was added, then covered with ≈ 2 ml of carbon disulfide. The carbon disulfide/bromine solution was slowly added and mixed with the phosphorus/carbon disulfide mixture. The addition was stopped when approximately half of the red phosphorus had been consumed. The sample was mixed until the bromine color cleared. A sample introduced into the gas chromatograph/mass spectrometer provided positive sample identification of the phosphorus tribromide derivative. Because bromine and phosphorus tribromide are hazardous chemicals to personnel and chromatographic columns, there was a need to find a better way to analyze red phosphorus. The KBI Chemistry Unit acquired a GC/MS with a direct insertion probe and developed a method for the analysis of red phosphorus. The probe contained a filament that volatilized red phosphorus samples directly into the mass spectrometer source. The system permitted phosphorus identification; however, maintaining consistent sample size was a problem. This combined with a cumbersome probe procedure limited the use of the unit. In order to augment our inorganic analysis capabilities, the KBI Chemistry Unit acquired an X-ray fluorescence spectrophotometer. It quickly became a favorite for the determination of phosphorus in clandestine methamphetamine laboratory samples. This instrument had the occasional need for an expensive detector replacement. When this happened, the KBI Chemistry Unit would use the phosphorus tribromide derivation method or the direct insertion probe to analyze red phosphorus samples. While evaluating a phosphorus tribromide sample spectra, a small chromatographic peak with a corresponding white phosphorus spectrum was observed (no determination was made of the white phosphorus source. The white phosphorus may have been part of the sample or it may have been a byproduct of the derivation process.) This observation was significant because it led to the search to convert red phosphorus into white phosphorus. Soon, a KBI
J. Schieferecke, D. Worley / J. Anal. Appl. Pyrolysis 71 (2004) 47–50
49
chemist developed a method for quickly heating red phosphorus in a nitrogen-purged and capped test tube. The method used ≈ 3 mg of red phosphorus, 10 × 75 mm flint glass test tubes and 10 mm Fisherbrand Tainer Top Safety closures. Preparing the sample involved placing red phosphorus in a test tube, purging the test tube with dry nitrogen and quickly capping the test tube. The conversion took place in an operating fume hood using heat from a Bunsen burner applied to the bottom of the test tube. When the sample started to form white vapor, the test tube was removed and allowed to cool. The vapor condensed inside the test tube into very small clear droplets. Chloroform (2 ml) quickly added to the test tube dissolved the clear droplets. A sample of the solution subjected to the gas chromatograph/mass spectrometer permitted phosphorus identification. Shortly thereafter, the KBI Chemistry Unit acquired an Agilent GC/MS system (6890A GC and 5973 MS) fitted with a CDS Analytical, Inc. Pyroprobe 2000 pyrolysis instrument. After installation and initial testing were complete, a KBI chemist realized that the high temperature and inert conditions in the Pyroprobe 2000 were comparable to the recently developed purged and capped test tube technique. A sample of red phosphorus was placed into the Pyroprobe 2000 under the same conditions as the initial test samples. The results were encouraging and the following method developed for the analysis of red phosphorus.
2. Experimental A sample of red phosphorus (<0.1 mg) was pyrolyzed with a setpoint of 750 ◦ C for 20 s using a CDS Pyroprobe 2000. Analysis was performed using an Agilent GC/MS
Fig. 1. Chromatographic peak and mass spectrum of white phosphorus produced from red phosphorus.
50
J. Schieferecke, D. Worley / J. Anal. Appl. Pyrolysis 71 (2004) 47–50
(6890A/5973) system with a HP-1MS (30 m × 0.32 mm × 0.25 film thickness) capillary column. The oven ramped from 100 to 275 ◦ C at 25 ◦ C per minute. Helium was the carrier gas, had an inlet pressure of 10.00 psi and split ratio of 50:1. The mass spectrometer scan range was 30–200 AMU. The phosphorus spectra obtained with this technique (Fig. 1) were similar to those obtained using the direct insertion probe and those using the nitrogen purged and capped test tube technique.
3. Discussion Suspected clandestine laboratory red phosphorus samples vary widely in composition. Because of this variation, the temperatures used for the operation of the Pyroprobe 2000 and the gas chromatograph operations are higher to ensure sample pyrolysis and elution. The pyrolysis technique employed to analyze samples thought to contain red phosphorus is an easy technique to learn and use. It gives excellent results with less sample handling than the direct insertion probe technique or the nitrogen purged, capped, and heated test tube technique. In addition, this technique reduces the hazards associated with handling white phosphorus.
Reference [1] W.F. Ehret, Smith’s College Chemistry, sixth ed, Appleton-Century, New York, London, 1946, p. 365.