Theft of Demerol and other controlled substances by health care professionals is a recurring problem across the U.S. In June 1989, the author (working at the toxicology lab of St. Mary's Hospital in Rochester, New York) received a call from the Drug Enforcement Administration (DEA) regarding a Demerol theft investigation. A number of patients at a local hospital were complaining that they still had pain even after receiving their Demerol injections. Toxicology studies suggested that they had not in fact received any Demerol, implying diversion/theft by a nurse or other health-care professional. Hundreds of nurses were working at any one time, and they often worked on different nursing stations. To identify a suspect, the case agent systematically switched all nurses' floor schedules over several days. This process demonstrated that the patient complaints only occurred when a certain nurse was on duty. The case involved 75 mg Demerol syringes. The agent reasoned that the Demerol was being removed and used by the nurse, and a unknown liquid placed back in the syringe for patient injection. Because no patient became ill, it was felt that the nurse was using one of four sterile solutions as the replacement. The agent wanted to know exactly which of the four solutions was being used so that he could confront the suspect from a basis of fact and thereby elicit a confession. The available solutions included two normal salines and two sterile waters. Osmolality and specific gravity testing were performed on a control (untampered) Demerol syringe solution, on a suspect (tampered) Demerol syringe solution, and on all four sterile solutions. An independent quantitative analysis on the suspect Demerol solution confirmed that it only had 3.9 mg of Demerol remaining - consistent with a single plunger removal of Demerol and refill with one of the sterile solutions. The osmolality and specific gravity results are reported in Table 8.
Table 8 - Osmolality and Specific Gravity Measurements in the Missing Demerol Case
| Sample | Osmolality [mOsm/kg] | Spec. Gravity |
|---|---|---|
| 75 mg Demerol Control Syringe | 429 | 1.037 |
| 75 mg Demerol Suspect Syringe | 381 | 1.011 |
| Abbott Bacteriostatic Saline | 374 | 1.010 |
| Lyphomed Saline | 291 | 1.004 |
| Quad Bacteriostatic Water | 93 | 1.005 |
| Abbott Sterile Water | 1 | 1.000 |
As the results show, the specific gravity testing had limited usefulness because it could not unambiguously differentiate between all solutions. However, the osmolality testing demonstrated that Abbott Bacteriostatic Saline was most likely used to refill the syringe. The observed 381 mOsm/kg result in the suspect syringe (slightly higher than the Abbott solution), was probably due to the slight effect of the 3.9 mg of Demerol still remaining in the solution. Upon confrontation with the evidence, the nurse admitted her guilt. With the
exception of osmolality, no other laboratory method available at that time could have been employed to differentiate between different brands of saline and water. Osmolality would clearly be a useful technique for similar, current cases of controlled substance thefts from hospitals, pharmacies, doctors' offices, and similar stocks.
Additional Potential Forensic Applications
Identification of Sugar-Based Beverages Substituted for Diet Beverages 2,4
The accidental or purposeful substitution of a sugar-based beverage for a diet (sugarless) beverage can be harmful to a diabetic individual. Several different lots of Pepsi and Diet Pepsi were tested to determine if it would be possible to differentiate the sugar based beverage from the diet beverage. The results are as follows:
Pepsi: 711-737 mOsm/kg (n=5)
Diet Pepsi: 13-32 mOsm/kg (n=6)
Although only 11 different lots were tested, there is clearly enough difference between the two types of beverages to allow a reasonable determination of diet versus sugar-based.
Poisoning of Domestic Pets' Water with Ethylene Glycol
Dogs and cats are very sensitive to the poisonous effects of antifreeze (which contains ethylene glycol). Fatal amounts are 1.4 mL/kg for cats and 6.6 mL/kg for dogs 5. The sweet odor and taste of ethylene glycol makes it very attractive to animals, and it is therefore a particularly insidious poison. Osmolality is a very useful initial screen for suspect solutions in that it will detect the presence of ethylene glycol (and also other alcohols) at very low levels in water. Based on ethylene glycol's molecular weight of 62.02, a 1 percent solution in water would read 161 mOsm/kg, versus a typical tap water value of approximately 3 mOsm/kg.
Identification of Water 2,3,4
Water is submitted on occasion to crime laboratories. Although osmolality cannot detect the presence of large molecular weight compounds in water at low concentrations [i.e., most "classic" street drugs], it is an excellent tool to identify that a submitted solution is water. Most waters tested ranged from 0 - 8 mOsm/kg. Only high-mineral content spring waters had higher values, up to 28 mOsm/kg. Non-water solvents will not freeze and no result will be obtained. Any polar solvent mixed into water will greatly increase its osmolality. Acids and bases that have been added to the water will increase the osmolality and also give a pH change. For example, a solution of 1 mL of Chlorox [5 percent hypochlorite] in 100 mL of distilled water, has a pH of 10.5 and an osmolality of 43 mOsm/kg. A solution of 1 mL of 12N HCl in 100 mL of distilled water has a pH of 1.0 and an osmolality of 243 mOsm/kg. A 1 percent solution of ethanol in distilled water has a osmolality of 158 mOsm/kg.
Field Testing
With results available within 15 minutes after plug-in, on only 0.25 mL of sample, the Advanced 3D3 Osmometer instrument used in this study (or any equivalent osmometer) can be easily adapted for field testing at large concert events from police D.U.I. vans. This would allow rapid beverage screening before submission of case samples to the crime lab.
Limitations
"Date-Rape" Benzodiazepines in Solution 2
As previously mentioned, the high molecular weight of common "classic" street drugs, and their low concentration in submitted solutions, makes osmolality an ineffective screening tool for their identification. For example, a single methylphenidate (Ritalin) tablet containing 5 mg of active drug and weighing 91 mg, produced a measured osmolality of only 11 mOsm/kg when dissolved in 30 mL distilled water. Therefore, osmolality is not viable for detection of drink tampering with, e.g., flunitrazepam (Rohypnol) or other sedative benzodiazepines that are employed for drug facilitated sexual assault.
Urine in Beverages 6
Beverages are occasionally maliciously adulterated with urine. The osmolality of an individual's urine varies widely [50 - 1400 mOsm/kg] and greatly depends on the person's degree of hydration. Urea, the compound of highest concentration in the urine, varies from 0.7 - 3.3 g/100 mL, and is a better indicator of tampering than osmolality. Although a typical random urine volume of 4 - 8 oz [118 - 237 mL] may be produced, let us assume 1 oz [30 mL] was introduced into a 50 oz pot of coffee[1480 mL]. The resulting urea levels would be 14 - 67 mg/100 mL. This is easily measured with a typical urea analysis method, which usually have a dynamic range of 2 - 212 mg/100 mL.
Saliva in Beverages 3
Similarly, beverages are occasionally maliciously adulterated with saliva. Amylase, which is present in very high levels in saliva [20,000 units/100 mL], is a better indicator of beverage adulteration with saliva versus osmolality. A typical 0.5 mL "spit" volume in an 8 oz [237 mL] cup of coffee would result in a measured amylase of 422 units/100 mL. This is easily measured with an amylase method having a dynamic range of 1-200 units/100 mL.
Conclusions
With ever increasing case loads and limited personnel resources, crime laboratories need efficient new tools to process the disturbing increases in liquid sample submissions. Osmolality, an effective analytical tool of the hospital laboratory and food and consumer products industries, is a low cost, rapid, facile, and non-destructive screening tool for forensic chemists and toxicologists.
Acknowledgements
Special thanks to Don Wiggin from Advanced Instruments for the loan of the 3D3 osmometer, and to the Rochester Institute of Technology and Drug ID Systems for providing the samples for testing.
Reference
- The Advanced Osmometer Model 3D3 User's Guide, Advanced Instruments Inc, Norwood, MA (2000)
- J. Wesley, Unpublished Data, Drug ID Systems, Inc., Rochester, NY using an Advanced 3D3 Osmometer (2001).
- J. Wesley, Unpublished Data, St. Mary's Hospital Toxicology Lab, Rochester, NY using an Advanced 3D2 Osmometer (1985-1990).
- T. Senosi, Rochester Institute of Technology, Rochester, NY using an Advanced Wide Range 3W2 Osmometer (2000-2001).
- L. Tilley, The Five Minute Veterinary Consultant, 2nd Ed. (2000).
- N. Tietz, Fundamentals of Clinical Chemistry, 3rd Ed, W.B. Saunders Co. p. 961 (1987).