This means that (for example), if we fill a 10 mL syringe to its 10 mL mark and we all agree the syringe is full (contains no significant air), the best we can know is that the syringe contains somewhere between 9.6 mL and 10.4 mL. The fact that you can move the plunger in a syringe to a particular mark on its scale does not necessarily mean you are accurately measuring that amount, especially at the lower end of the scale. General-purpose syringes are used in many laboratories and other workplaces for drawing up and expelling liquids or suspensions. They are designed to fit appropriate needles, tubing, syringe filters, or similar devices, and are constructed of plastic, glass, or a combination of both. They may also have metal components. Products should be stored in relative humidity less than 80%, non-corrosive gases, cool, dry and well-ventilated clean room. All used needles as well as their attached used syringes must be placed in hazardous waste sharps containers immediately after use. They may not be thrown in trash baskets.

If we apply gravimetrics to the preparation process, and those gravimetrics correct the concentration computed for the vial based on detecting the addition of 9.4 mL rather than 9.6 mL, it is still only an approximation since we cannot know what was really in the vial in the first place, by a surprisingly wide margin. The range that was 830 mg to 1245 mg is reduced to 870 mg to 1200 mg. Since many gravimetric systems have an acceptable error in the ±5% range, there’s not much of this process they can ameliorate. What they can do is present evidence that suitable mass of something was transferred from one container to another. And that’s valuable. The short story here is that even the difference between two proximate values at two points behind the decimal (e.g. 1.04 and 1.05), results in a change in volume that cannot be practically measured, much less be accurately (within ±10%) by a syringe that can measure the entire volume.Intradermal (ID) Shallow injection to be given just under the skin between the dermis and the epidermis. Used mainly for skin tests. Not used to deliver medications. 0.1 mL is the usual volume for skin test injections. A 1-mL syringe is used. This is a 5 mL syringe. Each line measures in 0.2 increments until it reaches a total capacity of 5 mL. A vial labeled to contain 1 gram of Cefazolin Sodium (as described in its USP monograph) is -10% to +15%. While it is likely that not all vials fall at the ends of this range, the best we can know is that the vial itself contains somewhere between 900 mg and 1,150 mg. It seems likely that vendors generally err on the heavy side of that equation, but the likelihood that a vial contains exactly 1 gram is small. FIGURE 6-7 A, 1-mL tuberculin syringe. B, 100-Unit 1-mL insulin syringe. (From Potter PA, Perry AG: Fundamentals of nursing, ed. 7, St. Louis, 2009, Mosby.)

You can’t make a measurement more precise by performing arithmetic on it (you can’t weigh 1000 items on a scale accurate to the nearest gram and produce an accurate weight to the microgram level). The amount of medication in a source container of an injection is defined by the USP monograph for that injection. For example, according to the monograph for Cefazolin Sodium for Injection, a container is considered accurately filled if it contains between -10% and +15% of its labeled potency. Based on looking at over 250 monographs of liquid injections, most are within ±10% (though there are some significant outliers. Again, this doesn’t mean that all instances of any product are at these limits; it does mean that any instance of a product could be at these limits and be considered to be accurately filled. FIGURE 6-8 Parts of a syringe. (From Potter PA, Perry AG: Fundamentals of nursing, ed. 7, St. Louis, 2009, Mosby.) The most accurate syringe in common use has an accuracy of ±4% when its nominal volume is 5 mL or greater when delivering at 50% or more of its nominal volume.Low dead space syringes: Authors’ response Zule, William A.; Cross, Harry E.; Stover, John; Pretorius, Carel International Journal of Drug Policy, 2013, Vol.24(1), pp.21-22, 2013 My observation is that we tend to treat these objects as if what appears on their labeling (including the measurement scale on the syringe) was completely and quintessentially accurate. The truth is that it may not be.